The epidemic of childhood allergic disorders has been associated to the decline of infectious disease. However, exposure to many triggers  contribute to the disease. Breast feeding practices, nutrition, dietary and obesity also play a multifaceted role in shaping the observed worldwide trends of childhood allergies. Guidelines for treatment are available, but their implementation is suboptimal. Then developed countries are slowing learning integrating the development of suitable guidelines with implementation plans. Awareness, psychosocial and family factors strongly influence asthma and food allergy control. Moreover, monitoring tools are necessary to facilitate self-management. By taking into consideration these and many other pragmatic aspects, national public health programs to control the allergic epidemic have been successful in reducing its impact and trace the need for future research in the area. Howeverpecially . Similarpecially . By contpecially . In parapecially . Many pupecially , progrespecially , environpecially -11 or thpecially . A recenpecially . On indipecially ,14-16. Fpecially . Birth oAlthough infections are risk factors of chronic urticaria  and otheThe role of atopic sensitization and viral infections in asthma has been extensively reviewed  and inveGuidelines for treatment are available, but their implementation is suboptimal. Then developed countries are slowing learning integrating the development of suitable guidelines with implementation plans. Awareness, psychosocial and family factors strongly influence asthma and food allergy control. Moreover, monitoring tools are necessary to facilitate self-management. By taking into consideration these and many other pragmatic aspects, national public health programs to control the allergic epidemic have been successful in reducing its impact and trace the need for future research in the area.at population level but also that risk factors of susceptibility must be taken into account at individual level.Traffic-related air pollution (TRAP) and biomass fuels (BMF) play a central role in the asthma epidemic especially in middle and low income countries. In Asia, TRAP and BMF increase the risk of asthma outbreaks, asthma exacerbations, respiratory infections and even COPD . But alsThe asthma epidemic is not the only one among children of developed and developing countries. A parallel increase in obesity and asthma rates suggests that allergic respiratory disease may be linked to dietary factors and behaviors and that the two conditions may influence each other . AccordiThe epidemic of childhood allergic disorders has been associated to the decline of infectious disease. However, exposure to many triggers  contribute to the disease. Breast feeding practices, nutrition, dietary and obesity also play a multifaceted role in shaping the observed worldwide trends of childhood allergies.A smaller study among Italian children has shown that the female gender is a risk factor for asthma associated to obesity . Regularin utero was found associated with enhanced allergen-induced lymphocyte responses and cytokine production into airways [The impact of nutrition on the development of respiratory disorders in childhood may begin already before birth. In a Finnish population-based birth cohort study (n = 2441), mother’s reduced intake of certain foods  during pregnancy was associated with increased risk of wheeze (but not asthma) in her child at 5 years of age ,54. Howe airways . A case– airways . Vitamin airways . Moreove airways ,58 and s airways . On the  airways . Last bu airways . Similar airways .Suitable and reliable prediction tools are essential to identify targets for prevention. Since many years clinical scientists are trying to find markers predicting asthma. A recent study has shown that inflammatory markers, including many interleukins  are elevated in the exhaled breath condensate already during the pre-clinical phase anticipating wheezing . FurtherPrediction models are used to facilitate the identification of targets for prevention. Until a few years ago, allergic asthma prevention has been mostly based on allergen avoidance. Studies results though show no or little benefit from allergen avoidance. By contrast, a national plan for allergy and asthma prevention, recently implemented in Finland, has shown that implementation of balanced diets, physical activity and protection from other allergy promoting factors such as tobacco smoke represent adequate prevention methods . This FiIn contrast to asthma, studies on prediction and prevention of atopic eczema are still providing relatively conflicting outcomes. However, the “classical” biomarkers of allergy, such as total and specific IgE levels are still considered valuable pre-clinical predictive biomarkers -73. For Asthma control is essential to prevent long-term consequences of asthma and improve patients’ quality of life. Hence, many studies focus on identification of reliable diagnostic tools to monitor asthma control. While the diagnostic role of atopic tests, lung function and challenge tests in asthma are quite established since decades that of breath condensate is still hotly debated. Exhaled nitric oxide (NO), a non-invasive marker of airway inflammation, can be implemented in the diagnosis and management of asthma and its strong relation to atopy, (e.g. house dust mite sensitization) has been recently described . FurtherOther measures of oxidative stress have been also tested. A case–control study on 219 Turkish children has shown that higher concentrations of Malondialdehyde and GSH in exhaled breath condensate are a marker of asthma and allergic rhinitis and are associated with enhanced oxidative stress . AnotherAnti-inflammatory drugs and bronchodilators -93 and aFood allergy monitoring and control is a highly developing area of investigation and we can consider here only a few examples of studies dealing with the need of molecular diagnosis, the antigen-specificity of oral tolerance induction and the use of epinephrine, respectively.Cross-reactivity and pan-allergens represent one of the difficulties that often hamper the diagnosis of allergies to vegetal food in childhood. Therefore, diagnostic tools should be developed to support clinicians in distinguishing between tolerant and allergic and then between primary and secondary allergic patients. In birch-pollen-associated secondary soy allergy, SPT with soy flour and molecular diagnostic of specific IgE to Gly m4 facilitate a correct diagnosis . IgE levStudies on oral tolerance induction (OIT) are defining more and more the usefulness and limitations of this novel therapeutic approach. Cow’s milk allergy affects 1.9-4.9% of the children, of which a few might suffer from a protein energy malnutrition caused by the subsequent dietary . TherefoDespite intensive research and progress, allergic diseases in childhood still represent a complex challenge for the family and the society. They has a considerable impact on quality of life for the patients and a financial burden for the society caused by increased costs, morbidity and mortality . A recenHence, not only for the patients, but also for their families it is important to establish clear plans beyond the patient’s direct needs by involving the community. Such perspectives can be successfully achieved by national-wide management programs aimed at minimizing disease’s impact on the whole society and the healthcare systems . FurtherGuidelines for treatment are available, but their implementation is suboptimal. Developed countries are slowing learning integrating the development of suitable guidelines with implementation plans. Awareness, psychosocial and family factors strongly influence asthma and food allergy control. Moreover, monitoring tools are necessary to facilitate self-management. By taking into consideration these and many other pragmatic aspects, national public health programs to control the allergic epidemic have been successful in reducing its impact and trace the need for future research in the area.Moreover, awareness for food allergies and anaphylaxis must be improved also among teachers and school-personnel, since schools are the places with the highest attack-related death rate . RecommeThe most recent advances in the field of childhood asthma summarized in this review give us an idea of how fast clinical research in this area is making progress. Solid approaches to avoid risk factors and to promote protective factors should be established according to the recent findings. Nevertheless, many studies demonstrated the huge lack in adopting and implementing recommendations and guidelines in everyday life, which require further development of current intervention and control strategies in the framework of national asthma control programs to choke the worldwide asthma epidemic.AR: Allergic rhinitis; BMI: Body mass index; CI: Confidence interval; DBPC: Double blinded placebo controlled; GINA: Global initiative for asthma; HDM: House dust mites; HRV: Human rhinovirus; ISAAC: International study of asthma and allergies in childhood; OR: Odds ratio; PAH: Polycyclic aromatic hydrocarbons; PM: Fine particular matter; RSV: Respiratory syncytial virus; SCIT: Subcutaneous specific immunotherapy; SLIT: Sublingual specific immunotherapy; SOTI: Specific oral tolerance induction; SPT: Skin prick test; Yr(s): Year(s).The authors declare that they have no competing interests.DH wrote the draft version and made the literature search. ST revised the final version. Both authors read and approved the final manuscript.


Global climate change will have multiple effects on human health. Vulnerable populations—children, the elderly, and the poor—will be disproportionately affected.We reviewed projected impacts of climate change on children’s health, the pathways involved in these effects, and prevention strategies.We assessed primary studies, review articles, and organizational reports.Climate change is increasing the global burden of disease and in the year 2000 was responsible for > 150,000 deaths worldwide. Of this disease burden, 88% fell upon children. Documented health effects include changing ranges of vector-borne diseases such as malaria and dengue; increased diarrheal and respiratory disease; increased morbidity and mortality from extreme weather; changed exposures to toxic chemicals; worsened poverty; food and physical insecurity; and threats to human habitation. Heat-related health effects for which research is emerging include diminished school performance, increased rates of pregnancy complications, and renal effects. Stark variation in these outcomes is evident by geographic region and socioeconomic status, and these impacts will exacerbate health disparities. Prevention strategies to reduce health impacts of climate change include reduction of greenhouse gas emissions and adaptation through multiple public health interventions.Further quantification of the effects of climate change on children’s health is needed globally and also at regional and local levels through enhanced monitoring of children’s environmental health and by tracking selected indicators. Climate change preparedness strategies need to be incorporated into public health programs. Global climate change is anticipated to increase the average global temperature and the frequency of extreme weather events. Regional projections, however, show substantial variation in amount and timing of precipitation, increasing in some places and decreasing in others, and they indicate an overall increase in variability of weather patterns . Sea levUsing a children’s health framework , in the The exposures that influence children’s health begin before conception—reflecting parents’ diets and other environmental exposures—and continue through pregnancy, childhood, and adolescence. Children have less effective heat adaptation capacity than do adults .Plasmodium falciparum malaria from mosquitoes, a vector exquisitely sensitive to changes in temperature and precipitation, they have a higher complication rate  and a higher mortality rate relative to older populations, presumably because they have less acquired functional immune response  metric that includes morbidity as well as mortality and provides a composite picture of health impacts caused by diverse risk factors . AccordiGlobally, for all ages, the burden of disease attributable to climate change in the year 2000 was > 150,000 deaths  and 5.5 million lost DALYs  . These ea) establishing response functions for climate-sensitive diseases using existing data sets, b) conducting targeted surveillance to detect changes in current climate-sensitive disease outcomes, and c) projecting climate-sensitive health burdens. Above we reviewed efforts to quantify the existing global burden of climate-sensitive disease among children, which builds on the first two of McMichael’s tasks. We now focus on some specific climate-sensitive health risks that also build on baseline epidemiology but further detail the mechanisms underlying these child-specific risk factors.Global climate change will likely increase the spread of some infectious diseases categorized as vector-borne, food-borne, and water-borne diseases. Among the vector-borne illnesses, the climate health impact literature focuses primarily on malaria, dengue fever, and tick-borne diseases such as Lyme disease. Complications from a number of such diseases, particularly malaria, are higher in children. Regarding diarrheal diseases, a number of studies have shown links between temperature or rainfall events and generic acute gastrointestinal illness or specific food- or water-borne illnesses . One stuThe 2002 World Health Report states that childhood malnutrition is the most widespread and pervasive primary risk factor for the major diseases of children . ClimateNumerous air pollutants with well-established pediatric respiratory effects  will potWeed pollen, shown to increase in climate change simulation studies, and grass pollen have been associated with children’s asthma exacerbations, emergency department visits, and hospitalizations . The lasHealth impacts on children from projected increases in frequency and severity of extreme storm events and sea level rise that result from global warming include acute injuries, chronic mental illness, food insecurity issues, food and water contamination, and potential wide-scale population displacement. All of these topics have been examined extensively in previous review articles . One addIn the 1990s, disasters affected 66.5 million children around the world . EstimatThere are also potentially subclinical effects from extreme heat events. The impacts include decreased functioning and diminished productivity . AlthougIn one London-based study, children 0–4 years of age showed hospitalization rates above baseline not only for respiratory but also for renal disorders in relation to increasing ambient summer temperatures . In addiStudy of the potential influences on pregnancy and prenatal complications of direct temperature effects related to climate change is an area of emerging research . There iPoorer households have been observed to be more vulnerable to climate change–related events such as floods , and chiChildren warrant special consideration when quantifying the impact of potential toxic exposures because of their potential increased susceptibility to negative health effects during their rapid growth and development and greater exposures per body weight. Changes in temperature, humidity, and the hydrologic cycle will affect patterns of exposure to chemicals used in food production and other pest control . An inveChemicals known as persistent organic pollutants (POPs) last for decades without biodegrading. Global surface temperatures, wind patterns, animal migratory patterns, and global ice volume play a role in the distribution of these chemicals . ClimateAspergillus species. Risk of contamination depends on many factors such as regional climate, preseason precipitation, minimum and maximum daily temperature, and daily net evaporation  is produced by poration . More thporation , which iporation . Other hporation . Researcporation .Estimating the future burden of climate-related disease impacts on children is complex. Future projections should take into account not only local climate-related effects but also other significant environmental changes such as stratospheric ozone depletion, accelerating loss of biodiversity, and alterations in elemental cycles such as the nitrogen cycle . AlthougMany countries with the highest rates of childhood disease and death are undergoing demographic transitions toward greater industrial development. However, according to the 2002 World Health Report , even afPrevention strategies in relation to climate change have largely focused on reduction or mitigation of greenhouse gas (GHG) levels in the global system. However, many GHGs in the atmosphere and dissolved in the ocean from past and ongoing human activity are long-lived and will drive climate change for years to come, a process termed “built-in” climate change . Their cThe concept of prevention in public health is multitiered. Previous articles on the impacts of climate change on health, and on children’s health in particular, have called for additional research to improve understanding of the relationships between climatic factors and health, quantification of the current impacts, and projections of future impacts. Such research, including surveillance and program evaluation, is essential to inform the prioritization of activities related to climate change adaptation in public health. Frameworks for prevention include incorporation of climate change actions into the 10 essential functions of public health  and the A reasonable public health strategy addresses present-day health problems while building adaptive capacity to respond to worsening future impacts from climate change. Although climate change is already creating a substantial global burden of disease, the current DALYs due to unsafe water, lack of sanitation and hygiene, urban air pollution, indoor smoke from solid fuels, and lead exposure dwarf the present-day effects of climate change on health .Numerous programs exist into which children’s environmental health platforms, with specific attention to climate change adaptation, could be incorporated . IntegraAnother area that integrates well with pediatric prevention efforts around climate change is the global demand from women for increased access to birth control . AlthougLast, children can play a role in adaptation, namely in building resilience. Children should attend school where opportunities exist for curriculum development that best prepares them for expected changes. There are international precedents for such action in the sustainable-school and health-promoting schools movements .New prevention projects should incorporate adaptations whose impacts have been carefully considered for unintended consequences so that they can simultaneously improve existing health disparities, build community resilience, and decrease climate-related impacts . Local pAn emerging tool to assess new policies, programs, and projects is the health impact assessment. In climate change work, health impact assessments are an emerging practice that strives to quantify the positive and negative health effects of an intervention . The cosThe health impacts of global climate change are expected to be widespread, geographically variable, and profoundly influenced by preexisting social and economic disparities. Effects on children and on other vulnerable populations are already—and are projected to continue to be—disproportionately heavy. The literature on proven and plausible health impacts of global climate change now covers virtually every organ system in the human body. More thorough quantification of child-specific health impacts of global climate change is urgently needed.The expectation that global climate change will produce wide-scale, but still inadequately quantified, increases in disease and death warrants a societal commitment that combines ongoing research with vigorous and thoughtful efforts to reverse health impacts and reduce worsening environmental injustice. Prevention efforts directed against the health effects of climate change should acknowledge the inherent vulnerabilities of children and seek to reduce both their exposures and susceptibility. Health projects that benefit adults while appropriately protecting children will have added benefits for the children by protecting their caregivers.Specific needs include enhanced monitoring of current children’s environmental health status, better incorporation of climate change adaptation into existing programs, and new climate-sensitive disease prevention programs that have short- and long-term health co-benefits.


Acid is fundamental to the immune mechanisms of eukaryotes. Therefore pathogens have evolved a myriad of strategies to evade, suppress, or exploit biological acids to gain access to host resources. Here, we describe several intracellular and extracellular pathogens to illustrate our current understanding of how acid plays central roles in animal and plant immunity, and also how it can be produced and exploited by microbes for pathogenic success.The pH of an aqueous solution constitutes one of its most fundamental properties. Cells and organisms are largely aqueous entities and have evolved sophisticated strategies for sensing, exploiting, and modifying the pH of their surrounding environments for assorted biological processes, including nutrient acquisition, intercellular communication, virulence, and defense against invading pathogens. At the same time, abnormal intracellular or extracellular pH values are found in several human and plant diseases, including cancer The endocytic and phagocytic pathways of eukaryotic cells contain acidic intracellular compartments that carry out diverse functions, including nutrient acquisition The pH of early endosomes, late endosomes, and lysosomes/vacuoles are approximately 6, 5.5, and below 5, respectively, although their pH varies with cell type, cultivation conditions, and biological context Considerable research, using yeast, insect, worm, plant, and mammalian model systems, has been performed to elucidate the mechanisms by which acidic pH is achieved within the organelles of eukaryotic cells. The acidification of organelles in the endocytic pathway has been shown to be mediated by the activity of vacuolar-type ATPase (V-ATPase) enzymes The task of measuring the pH of intracellular organelles presents several challenges. First, the subcellular organelles of eukaryotic cells are small (from 0.1 µm in fungi to 50 µm in plants) and provide no direct access to the outside environment once formed Early estimates of the pH of intracellular organelles of plants, animals, and microbes were based upon the use of acidotropic dyes Biological acids play central roles in both innate and adaptive immune systems that dictate host-pathogen interactions. All living things possess innate immune mechanisms, while vertebrates benefit from the classically defined, lymphocyte-mediated adaptive immunity as well.In animal innate immunity, acid functions extracellularly and intracellularly. Low pH plays an important role extracellularly in controlling the microbial flora at mucosal sites, particularly in tetrapod vertebrates. The gastric acid of the stomach limits the range of prokaryotes that can continue down the alimentary canal to join intestinal populations R gene products contain leucine-rich repeats (LRR) and nucleotide binding sites and belong to the CATERPILLAR/NOD/NLR family of proteins that mediate cytosolic PAMP surveillance in animals as well Plants rely on the innate immune system for defense by sensing pathogen-derived molecules for nonself recognition R gene products of plants. These include the hormone salicylic acid that mediates endogenous defense signals and transmits systemic responses that orchestrate systemic acquired resistance Organic acids are crucial messengers of effector-triggered immunity activated by The adaptive immune system shared by jawed vertebrates is mediated by lymphocytes and has hallmark characteristics of specificity and memory. The adaptive system enables the preemptive engineering of our lymphocyte repertoires through immunization, one of the most powerful tools for global public health in the face of infectious disease. Like the plant ETI, the adaptive system is a second line of defense behind the innate system. While slower in initial response in comparison to the innate, the adaptive system is plastic in its mitotic expansion and contraction capability, surgical in the fine molecular specificity of its targeting, and diverse in its effector mechanisms tailored to classes and locales of pathogen.The vertebrate adaptive immune system works in conjunction with the more ancient innate system. The adaptive system may have originally evolved to manage the vast populations of commensal  bacteria at mucosal surfaces where low pH was already in use Most adaptive immune responses require activation of specific helper T lymphocytes, and the low-pH phagolysosomal system is important for this activation. Unlike B cells that recognize free antigen, T cells recognize peptide antigen in the context of major histocompatibility complex (MHC) molecules. Two different classes of MHC molecules present peptide to two different classes of T cells The low pH of compartments of the phagolysosomal pathway is co-opted by the adaptive as well as the innate immune system for defensive purposes. We suggest that the cellular physiology of this pathway has evolved from functioning in recycling of cellular debris and tissue remodeling in early eukaryotes In the trans-Golgi, the MHC class II/invariant chain complex is diverted from the secretory pathway to the endocytic pathway . In the Cathepsins, related to papain, are the crucial acid-activated proteases that cleave the invariant chain and also degrade lysosomal contents to peptides appropriate for antigen to be loaded in MHC class II Thus, the acidic phagolysosomal system prepares peptide antigens for the initiation of most cellular adaptive immune responses, mediated by the MHC class II system of presentation to helper T cells.Coxiella burnetii and Brucella melitensis—which have evolved disparate strategies for adapting to life in acidic environments and avoiding killing by acidic organelles. Two extracellular mucosal pathogens—Helicobacter pylori and Escherichia coli—exemplify tactics used to colonize the extreme pH of the alimentary canal. In addition, we describe the way in which the plant pathogens Agrobacterium tumefaciens and Sclerotinia sclerotium exploit and produce acidic environments, respectively, to promote their pathogenic programs. These host-pathogen systems have been chosen both for their position as major models in which acid defense mechanisms have been elucidated as well as their importance in human, animal, and plant pathology.Given the role that acid plays in host defense and antigen presentation in animal pathosystems, it is perhaps not surprising that both plant and animal pathogens have evolved sophisticated systems for adapting to, avoiding, or subverting the threats that acidic environments and acid-mediated defense processes pose. We illustrate this point using two intracellular bacterial pathogens—Coxiella burnetii provides a compelling example of such an adaptation. The Gram-negative bacterium C. burnetii is the causative agent of Q fever. Its natural reservoir in the United States consists mainly of dairy cattle, sheep, and goats Many organisms generate and use acidic environments to thwart infection by pathogens. However, some pathogens have evolved elegant strategies to defeat these acidic defense mechanisms, including the ability to withstand or thrive in highly acidic environments. The intracellular pathogen C. burnetii replicates within phagolysosome-like Coxiella-containing vacuoles (CCVs) and is dependent on the low pH of this compartment to activate a developmental process that turns metabolically quiescent small cell variants (SCV) into their metabolically active, replicating large cell counterparts C. burnetii is taken up via complement receptor 3 and αvβ3 integrin-mediated mechanisms into macrophages C. burnetii replication. First, studies using ratiometric, pH-sensitive probes have demonstrated that C. burnetii replicates in vacuoles that possess an acidic pH C. burnetii replicative niche has an acidic pH, and raise many questions about the mechanisms by which Coxiella and other acid-adapted intracellular pathogens survive in the highly acidic environment of the CCV terminal compartment Several lines of investigation support the hypothesis that maintenance of the acidic pH of the spacious vacuole is essential for C. burnetii, and the development of axenic growth conditions and suicide plasmid-based targeted gene deletion methods is allowing identification of virulence mechanisms and genes in this model C. burnetii encodes an unusually high number of basic proteins. The average pI value for all predicted proteins in the genome of the Nine Mile reference strain is 8.25 C. burnetii proteins were found to have a pI value of ≥9, which is higher than the sequenced genomes of other intracellular bacterial pathogens RpoS genes of E. coli (pI 4.6) and C. burnetti (pH 9.6) serve as striking examples of the extreme acid adaptation of a protein while maintaining a conserved function. It is hypothesized that Coxiella's skew toward production of basic proteins provides a proton sink to buffer those protons that enter the cytoplasm Coxiella tolerates cathepsin and other acid protease action while thriving in this environment. Coxiella therefore illustrates how pathogens can adapt to acidic compartments.Several strategies have been proposed to contribute to acid tolerance of Brucella spp. provide excellent models to analyze this strategy for addressing the threat that intracellular acidic vacuoles pose to invading pathogens. Brucella spp. are causative agents of brucellosis, a zoonosis of global importance Brucella is highly infectious and can be readily transmitted in aerosolized form Brucella as a potential bioterror agent, and to the interest the biosecurity and world health communities have expressed in this organism.In an alternative strategy, intracellular bacterial pathogens can address the threat that acidic intracellular compartments pose by minimizing their interactions with them. The intracellular bacterial pathogen Brucella-containing vacuoles (BCVs) interact but avoid fusion with the host lysosome During their intracellular trafficking within host cells, E. coli (strain 0157:H7), Vibrio cholerae, Vibrio vulnifus, Shigella flexneri, and Salmonella typhimurium are found in neutral pH environments (on food products or in water). However, after ingestion by their mammalian hosts, these pathogens encounter the severe acidic environment of the stomach (pH = 2 or lower) or urogenital systems, which normally constitute important barriers to infection by non–acid-adapted organisms. These parasites, however, have evolved sophisticated and divergent strategies to tolerate these harsh acidic environments.Several notable microbial pathogens, including those that infect the gastrointestinal or urogenital tracts of humans and animals, exploit or create extracellular acidic environments to promote their pathogenic programs. For example, pathogenic Helicobacter pylori, the agent whose colonization is associated with chronic gastrointestinal diseases ranging from dyspepsia to gastric and duodenal ulcers to gastric carcinoma H. pylori maintains a periplasmic pH at ∼6.1, while the extracellular environment can be as low as 2.0. The reaction products of urease apoenzyme (ureA and ureB) are driven specifically to the periplasmic compartment by a protein (UreI) encoded in a gene cluster with urease. UreI is a pH-gated inner membrane urea channel allowing for efficient transit to the cytoplasm of substrate (urea) and periplasmic release of reactant NH3, which is rapidly converted to NH4 by membrane-bound α-carbonic anhydrase. The transcriptional expression control, post-transcriptional recruitment, and enzymatic activity of H. pylori urease is optimized to function in a microenvironment of pH 3.5–∼6.0 A significant human pathogen that provides an understanding of an alternative strategy by which an extracellular acidic niche can be occupied is H. pylori is specialized for the extreme pH of the stomach, but enteric species survive passage through the stomach for colonization of the lower gut. Many E. coli efficiently colonize the intestine, and provide a complementary window for understanding how pathogens address the challenge of acidic environments. The acid stress response systems of Gram-negative enteric pathogens are both enzyme and chaperone based, and include resistance pathways that exploit glutamate-, arginine-, and lysine-decarboxylase enzymes E. coli contains five acid resistance pathways (AR1–5), which work in concert to resist the highly acidic environment that the pathogen encounters in the gut E. coli, for example, the pyridoxal 5′ phosphate (PLP)-dependent GadA and GadB decarboxylases convert glutamate to gamma-amino butyric acid (GABA) and carbon dioxide (CO2) in a reaction that consumes a cytoplasmic proton Thus gut pathogens use a variety of active biochemical systems to maintain periplasmic and cytoplasmic pH at tolerable levels amidst the low luminal pH of the gastrointestinal tract.Agrobacterium tumefaciens and Erwinia amylovora, the causative agents of crown gall disease in diverse dicotyledenous plants and fire blight in apples, pears, and Rosaceous crops, respectively, induce disparate and nonoverlapping disease symptoms in plants. Nevertheless, these pathogens respond to environmental acids by modulating their virulence programs, and thus provide ideal illustrations of an important mechanism by which pathogens of both plants and animals respond to acidic extracellular environments in the context of the host-pathogen interaction.Analysis of interactions between plant pathogens and their host plants provides additional insights into the role of acid in host-pathogen interactions that cannot be fully appreciated by the exclusive analysis of animal systems. The bacterial pathogens Agrobacterium system, environmental acids drive the induction of the pathogen's virulence program. Specifically, the acidic environment created by wounded plant tissues, as well as plant-derived phenolic compounds present there, activate the expression of bacterial virulence genes (vir regulon) on the tumor-inducing (Ti) plasmid Agrobacterium-derived T-DNA from the bacterial pathogen to host cells. The T-DNA integrates into the host plant genome, triggering factors that mediate the generation of a tumor  in plants. Interestingly, the acidic conditions that initiate the T-DNA virulence program of Agrobacterium elicit two additional and distinct responses in the pathogen—a conserved response associated with the adaptation of the pathogen to environmental acidification, and the intricate response that regulates the establishment of a stable, long-term plant-pathogen interaction flaA and the heat-shock protein ibpA, are highly conserved and play corresponding roles in acid adaptation in other microbial systems, including in the bacterial pathogens of animals  Agrobacterium virulence program and activate the quorum-quenching machinery, which promotes the establishment of a stable host-pathogen interaction. However, signal input from one pathway  can inhibit the activation of another . The activation of quorum-sensing machinery as part of the process of establishing a stable host-pathogen interaction represents a conserved theme in the virulence programs of many bacterial pathogens In the Ustilago maydisFusarium oxysporumSclerotinia sclerotiorumFusarium wilt, and white mold diseases of all broadleaf plants, respectively.Extracellular acidic environments can also influence the virulence of fungal pathogens of plants, including Analogous to animal hormones, plant hormones play key roles in the control of development, growth, reproduction, and, of relevance for this discussion, the regulation of immune responses to microbial pathogens. Of the principal plant hormones, five are acids, including: salicylic acid (SA), jasmonic acid (JA), abscisic acid (ABA), indole acetic acid (IAA), and gibberellic acid (GA) npr1 locus were found to prevent SA signaling Systemic acquired resistance (SAR) is induced in the plant by SA following pathogen challenge. When established, SAR affords long-lasting and broad-spectrum resistance including uninfected tissue. SA levels increase following initial pathogen attack and are strongly correlated with establishment of SAR Coi1 mutants are more resistant to bacterial pathogens and show elevated SA levels coi1 plants are more susceptible to several, but not all, necrotrophic fungi. Exogenous application of JA induces broad changes in transcription patterns—in particular, of genes regulated by MYC2, a basic helix loop helix transcription factor in vitro, suggesting a possible mechanism for fine-tuning signaling responses COI1 promotes ubiquitination of JAZs leading to proteasome degradation, relieving repression of MYC2, and facilitating activation of JA-responsive genes The jasmonate family comprises lipid-derived metabolites synthesized via the oxylipin pathway Although JA is central to modulating defense against necrotrophic pathogens, it is increasingly important in other aspects of plant-pathogen interactions including SAR Sclerotinia sclerotiorum provides an informative model to illustrate acid-dependent pathogenic development. This fungus produces copious amounts of the dicarboxylic acid oxalic acid (OA) as part of its virulence arsenal, but also uses OA to reprogram host signaling and modulate programmed cell death to coordinate effective pathogenesis The phytopathogenic fungus Sclerotinia is an economically important necrotrophic fungal pathogen of plants with an extremely broad host range . The primary component for pathogenic success is the production and secretion of oxalic acid by the fungus S. sclerotiorum are nonpathogenic on all host plants tested and are also unable to develop sclerotia—highly melanized, durable overwintering structures. Oxalate secretion might enhance Sclerotinia virulence in several ways. Many fungal enzymes secreted during invasion of plant tissues  have maximal activities at acidic pH and have been shown to be activated by OA. A Sclerotinia MAP kinase has also been identified and characterized S. sclerotiorum. Gene expression of this Erk-like MAPK (SMK1) is triggered by acidic pH mediated by OA; if acidification does not occur, pathogenic development is blocked In fungi, this “simple” organic acid is remarkably multifunctional and contributes to numerous physiological and pathogenic processes 2+. Oxalic acid crystals are sequestered in vacuoles, and when decompartmentalized during infection, these crystals can plug the vascular system. Oxalic acid in and of itself is directly toxic, functioning as a non–host-specific phytotoxin. While these features are correlated with fungal disease development, they do not account for wild-type pathogenesis OA has several other deleterious effects upon the plant. It can degrade or weaken the plant cell wall via acidity and/or chelation of cell wall CaOA can function as an elicitor of apoptotic-like plant programmed cell death, involving the modulation of the host redox environment Sclerotinia (via OA) generates a reducing environment in host cells that suppresses host defense responses including the oxidative burst. Once infection is established, however, this necrotroph induces the generation of plant ROS leading to PCD of host tissue, the result of which is of direct and sole benefit to the pathogen. In contrast, a nonpathogenic, OA-deficient mutant failed to alter host redox status and induced autophagy and restricted growth. These results indicate active recognition of the mutant by the plant and further point to the importance of cell death control in mediating host-pathogen interactions.Conversely, during the initial stages of infection, OA also dampens the plant oxidative burst—an early host response generally associated with plant defense. Experiments using a transgenic redox-regulated GFP reporter show that, initially, Sclerotinia establishes reductive conditions that dampen the host oxidative burst and suppress defense responses Taken together, these data suggest that Helicobacter's urease system that keeps its periplasm close to neutral and E. coli's glutamate decarboxylase pathway that removes cytoplasmic protons as a component of its acid response. Acid is important in plant extracellular immunity as well and is a characteristic of wounding, but Agrobacterium senses this drop in pH and counters with acid-based signaling programs to ramp up and attenuate virulence effectors. Fungi such as Sclerotinia use OA to subvert host defense and co-opt host signaling pathways, triggering cell death via apoptosis of host cells. Thus fungal (OA) induced metabolic reprogramming of the host results in apoptosis, providing nutrients exclusively for the benefit of the necrotrophic organism.Just as pH is a fundamental property of living systems, acid is employed by both host and pathogen in their ever-escalating arms race. On the side of the host, acid is used in a variety of mechanisms, including extracellular innate immunity at mucosal surfaces and extreme pH in the case of the mammalian stomach. Yet some pathogens have evolved mechanisms to defeat the natural defense that the acidic environment provides, exemplified by Coxiella, while others have managed to reprogram the vesicle trafficking to mitigate interactions with harmful acidic organelles , as does Brucella. Ratiometric dyes have been crucial in facilitating the analysis of these intracellular organelles and the pathogenesis that occurs there. The adaptive immune system of vertebrates pirated the acidic phagolysosomal system for not only pathogen killing but also for antigen presentation to T cells. Vesicular acid and acid-activated proteases such as cathepsins are critical to antigen processing for MHC loading. But some microbes have evolved mechanisms to cope with the low pH of vacuoles, such as From the perspective of natural history, we see the mechanisms by which organisms exploit or subvert biological acids as central to their evolutionary success. Thus acid is one of a small, select number of fundamental biological arenas in which organic life has long fought. For example, membranes create a defined space for orderly biochemistry where metabolism and other necessities can occur protected from the chaos beyond the phospholipid bilayer. Naturally, immune systems evolve enzymes such as lysozyme, perforin, and the membrane attack complex of the complement cascade to disrupt the membranes, but pathogenic microbes evolve complex cell walls and capsules to protect and then elaborate secretion systems to breach these barriers. These are but a few of the many mechanisms and counter-mechanisms that operate at the theater of war that is the plasma membrane. Similarly, genomic integrity is also an important battleground; therefore, the simplest of organisms have elegant DNA repair systems, high-fidelity replication enzymes, and restriction endonucleases. Yet viruses still integrate, and even counter by exploiting the rapid evolution afforded by replication errors. In turn, the adaptive immune system employs somatic hypermutation of antibody genes in a Darwinian germinal center reaction to hone high-affinity receptors against ever-shifting pathogen antigens.Just as the plasma membrane and the genome are core components of life to be protected, exploited, and used in defense and offense, so is the pH of spaces large (stomach) and small (phagolysosome). It should come as no surprise that acids are used to great effect in signaling, killing, protecting, hiding, sampling, and evading by both host and microbe, and we should look to the trenches of protons and hydroxides for continued exploitation by both immune and pathogen systems.


Flavivirus genus. Indeed, most flavivirus antibodies are directed against the highly immunogenic envelope protein, which contains both flavivirus cross-reactive and virus-specific epitopes. Serological assay results should thus be interpreted with care and confirmed by comparative neutralization tests using a panel of viruses known to circulate in Europe. However, antibody cross-reactivity could be advantageous in efforts to control emerging flaviviruses because it ensures partial cross-protection. In contrast, it might also facilitate subsequent diseases, through a phenomenon called antibody-dependent enhancement mainly described for dengue virus infections. Here, we review the serological methods commonly used in WNV diagnosis and surveillance in Europe. By examining past and current epidemiological situations in different European countries, we present the challenges involved in interpreting flavivirus serological tests and setting up appropriate surveillance programs; we also address the consequences of flavivirus circulation and vaccination for host immunity.In Europe, many flaviviruses are endemic  or occasionally imported . Due to the temporal and geographical co-circulation of flaviviruses in Europe, flavivirus differentiation by diagnostic tests is crucial in the adaptation of surveillance and control efforts. Serological diagnosis of flavivirus infections is complicated by the antigenic similarities among the  Flaviviridae family and Flavivirus genus and is one of the most threatening flaviviruses in Europe (for a recent review see )Similar reasoning should be applied with respect to WNV diagnostic tools: Their validity in each specific WNV epidemiological situation should be verified to ensure that infections caused by varied WNV strains are detected . This prFlavivirus genus comprises 53 viruses (ICTV [The es (ICTV ). Many oes . Albeit imprecise, serological studies allowed different serocomplexes to be defined, including the JEV (WNV and USUV in Europe), YFV, DENV, and Ntaya virus (Bagaza virus—BAGV—in Europe) serocomplexes ,45. Moleogenesis . Culex-cdiseases ,48. The diseases . Many antigenically-related flaviviruses have been identified, and mosquito-borne flaviviruses have been found on every continent except Antarctica. Similarities in disease symptoms—only two syndromes, encephalitic and hemorrhagic, have been described in humans and animals—make it impossible to differentiate flavivirus infections clinically and precisely identify circulating flaviviruses. In the next subsection, we will describe flavivirus circulation and introduction risk in Europe .Ixodes ricinus and I. persulcatus; most cases have occurred in central Europe (Western subtype), Finland, and the European part of Russia (Western and Siberian subtypes) [I. ricinus ticks. OHFV, found in Russia, cycles between rodents  and Dermacentor reticulatus ticks in western Siberia, causing hemorrhagic diseases in humans and in some rodents  [Tick-borne flaviviruses are among the most medically important arboviruses in Europe. TBEV severely infects more than 10,000 humans every year and is transmitted by ubtypes)    that hasubtypes) ; it is tethicus) . Ornithodoros maritimus ticks among seabirds and was first identified in Brittany, France, is one such flavivirus [Several other tick-borne flaviviruses have thus far not been found to cause disease in humans or animals, and their potential pathogenicity in humans and animals is consequently unknown. Meaban virus (MEAV), which is transmitted by soft avivirus . Tyuleniavivirus . A wider diversity of tick-borne flaviviruses has been detected in Europe than in North America; the Powassan virus is the major tick-borne flavivirus found to be pathogenic in humans in North America. Mosquito-borne flaviviruses are similarly more diverse in Europe than in North America; specifically, WNV and USUV are widely distributed throughout Europe, and BAGV was identified in Spain . Of all the mosquito-borne flaviviruses, WNV has the most widespread geographical distribution and the largest vector and host range . It was Culex mosquitoes and was most probably introduced into Europe by migrant birds; retrospectively, it was first identified in cases of wild bird die-offs in 1996 in Tuscany, Italy [Turdus merula) in central Europe, starting in Austria in 2001 [USUV is a flavivirus that originated in Africa and is closely related to WNV. It is transmitted by y, Italy . In cont in 2001 ,68. USUV in 2001 ,73,74,75 in 2001 ,77.BAGV is identical to Israel turkey meningoencephalitis virus (ITMV), which was first described in Israel in 1960 based on samples taken from neurologically afflicted turkeys. It has more recently been found in infected partridges and pheasants in southern Spain . Anti-BACulex pipiens in northern Italy [Aedes-borne viruses, was identified in Finland [Aedes albopictus, which vectors DENV and Zika virus, provides a striking example of the successful invasion of new territories [Far more flaviviruses have been identified in recent years in Europe. For instance, flaviviruses that exclusively infect insects were discovered in Italy and Spain ,81, a JErn Italy , and Lam Finland . The mai Finland  and BAGV Finland . Future  Finland ,88,89,90ritories ,92; it writories ,94. In Europe, a few human vaccines against flaviviruses are available, specifically those against TBEV, JEV, and YFV see ; it is n® WNV, formerly Duvaxyn® WNV, Fort Dodge Animal Health/Pfizer) and the canarypox recombinant vaccine  have been commercialized in Europe . Immunization schedules involve administrating two doses of vaccine 3 to 6 weeks apart and annual boosters before the WNV transmission season . The emergence and pathogenicity of lineage 2 WNV strains in Europe has put into question the ability of existing WNV vaccines, which were developed from North American lineage 1 isolates, to provide protection against European WNV isolates. Both inactivated and canarypox vaccines have been shown to protect against virulent lineage 2 strains in immunochallenged mice and horses, respectively [In the case of WNV, only veterinary vaccines are currently used in Europe and have proven to be very effective in protecting horses from meningoencephalitis in North America . While fectively ,99. It sGymnogyps californianus) [Aphelocoma insularis) [Corvus brachyrhynchos and ossifragus) [Turdus migratorius) [Outside of Europe, WNV vaccination programs have been implemented to protect highly susceptible domestic bird species, e.g., geese (inactivated vaccine available in Israel ) and endrnianus)  or inactsularis) . DNA vacifragus) ,104 and atorius) , in the ® vaccine, based on the formalin-inactivated attenuated SA14-14-2 JEV strain grown in Vero cells, has demonstrated excellent safety and immunogenicity profiles; it is now the only JEV vaccine licensed in Europe, the U.S., or Australia [In humans, YFV and JEV vaccines are recommended for European travellers visiting areas in which the viruses are endemic, e.g., tropical and subtropical regions of Africa and South America or Southeast Asia, respectively. Vaccination against YFV is still based on the highly effective and relatively safe 17D live-attenuated vaccines initially developed in 1937 by Max Theiler ; protectustralia ,108. In ® or Encepur®, manufactured in Austria and Germany, respectively) and that are administered over the course of a comprehensive vaccination program that comprises multiple boosters. Their use varies widely in areas in which the virus is endemic, with high vaccination coverage in Austria (88%) and in the Sverdlovsk region of Russia, where a mass immunization program was initiated in 1996 [TBE can be effectively prevented in the field using purified inactivated whole virus vaccines that are produced in Europe and Russia from cell cultures  ,129. In ® WN) be handled in BSL-2 facilities. They have a higher level of specificity but are less sensitive than ELISAs [Overall, VNTs are time consuming and require that infectious virus be handled in Biosafety Level 3 (BSL-3) facilities or that a chimeric flavivirus such as the YFV/WNV recombinant virus  ELISA (The MAC-ELISA is suitable for detecting acute infections (8–60 days post-infection) in humans and horses; however, its usefulness in determining acute infections is questionable in humans, in whom WNV IgMs have been reported occasionally to persist for over a year . This teIndirect IgG ELISAs require the use of adapted anti-species conjugated antibodies ,138. BecDifferentiating Infected from Vaccinated Animals—DIVA—strategies) [The sensitivity and specificity of ELISAs are strongly influenced by the nature of the bound antigen. Attempts have been made to improve ELISA specificity using a recombinant version of the DIII of the E protein ,141 or bategies) ,142,143.Microsphere immunoassays are potentially useful tools because of their multiplexing capacity; they couple different flavivirus antigens to fluorescent and differentiable beads . NeverthIn conclusion, the specificity of many serological tests is still an issue of major concern. High-throughput screening tests that perform at high level of specificity are crucial, and recent improvements have been made in this field . The impSerological cross-reactivity may lead to the misinterpretation of diagnostic test results obtained from suspected clinical cases and samples collected during WNV epidemiological serosurveys. Awareness of possible cross-reactions is essential given that the aim of such investigations is to correctly identify the viruses responsible for the observed serological reactions. The nature and prevalence of cross-reactions differ depending on the target species and geographical location. Overall, the risk of cross-reactions exists wherever multiple flaviviruses co-circulate, including in Europe.The serological diagnosis of WNV infection is complicated by the fact that the patients or animals may have previously been exposed to or vaccinated against cross-reacting viruses. In this context, it is essential to use tests that are both sensitive enough to detect WNV infection and specific enough to distinguish an acute WNV infection from one caused by a closely related virus or remnants of prior WNV exposure. Here, we report the results of field and experimental studies that have compared diverse serological methods with the objective of optimizing the specificity of the serological diagnosis of WNV infection. ELISAs are the most commonly used diagnostic assays because of their simplicity and relatively low cost; they also require few specialized apparatus and facilities. When WNV first emerged on the North American continent in 1999, samples of serum and cerebrospinal fluid from the first eight patients hospitalized with viral encephalitis and meningitis tested positive for anti-SLEV antibodies based on IgM-capture and indirect IgG ELISAs; SLEV is a common flavivirus that is an enzootic of North America . Howeveret al. [Similar misinterpretations of serological results may occur in Europe because those being tested may have been exposed to co-circulating or newly emerging flaviviruses or have encountered flaviviruses while traveling. For example, although successive experimental infections in horses have suggested that WNV-specific competitive ELISAs using anti-NS1 MAb 3.1112G as a conjugate are highly specific for WNV , high raet al.  showed, et al. . Other methods, such as IFAs that detect IgMs or ELISAs that use virus-specific epitopes such as rEDIII, may prove to have greater specificity than above-mentioned ELISAs. However, studies consistently discourage basing a flavivirus serodiagnosis on single assay and only searching for a single virus . FurtherAs mentioned earlier, VNTs have a high degree of specificity for target flaviviruses, but cross-neutralization by antibodies against viruses within the same serocomplex is still observed. As a result, a thorough comparison of the end point titers obtained using other flaviviruses known to be endemic in the area should be performed ,153. VirAs a consequence, diagnostically differentiating among viruses may be hard in areas in which flaviviruses are hyperendemic . In partThe use of tests with high levels of specificity is even more important in WNV serological surveillance because the expected prevalence in the target population is lower and therefore the risk of obtaining false positives is higher. Another technical constraint is the necessity to rapidly and simultaneously screen large numbers of samples; this need makes ELISAs the method of choice since they are inexpensive and safe to perform under minimal biocontainment conditions. However, confirmation of sample seropositivity using VNTs is required to specifically identify the virus(es) responsible for the observed serological reactions. Because PRNT90 lacks sensitivity in weakly exposed populations, some authors have suggested that PRNT50 should be used in serological surveys; however, this latter test is not reliable enough to obtain robust conclusions ,156,157.In humans, serosurveys most often rely on sera collected from healthy blood donors whose vaccination and travel histories are unknown even though such factors may strongly affect the results of the serological tests used to detect WNV-specific antibodies. For example, in North Tyrol, initial ELISA results suggested that WNV seroprevalence was 46.2%; however, comparative neutralization tests revealed the existence of cross-reactions with anti-TBEV antibodies or other vaccine-associated flaviviral antibodies, which generated false positives. Accounting for these false positives, WNV seroprevalence was found to be 0.5% instead . In partEstimating the likelihood of encountering cross-reactions is particularly important in studies that use animal sentinels such as horses or captive birds to rapidly detect WNV circulation ,159,160.The results of serosurveys of free-ranging birds are particularly complex to interpret because some species are long-distance migrants that may encounter WNV and other flaviviruses at a large variety of exposure sites ,161. HowDetermining the age of seropositive hosts is of the utmost importance in WNV serosurveys, even if age can only be estimated, as is the case for wild animals. Younger animals should be excluded from immunological analyses because the presence of maternal antibodies in their systems could lead to a misinterpretation of the results. Maternal antibodies against WNV have been shown to remain detectable in the serum of horses for up to 120 days  and of bAs previously mentioned, the level of serological cross-reactivity frequently observed among flaviviruses can lead to diagnostic misinterpretation, but it could also have a beneficial effect by ensuring partial or complete cross-protection against serial flavivirus infections. On the other hand, it could also facilitate subsequent flavivirus infections via a mechanism called antibody-dependent enhancement (ADE), which has mainly been described for the dengue flavivirus but is possibly applicable to other flaviviruses.Few flavivirus vaccines are currently available for human use, and two in particular are lacking: those against the widespread DEN and WN viruses. It is therefore of utmost interest to evaluate the capacity of flavivirus vaccines to protect against heterologous flaviviruses. Cross-protection can most easily be assessed using vaccination trials that employ appropriate experimental conditions: experiments in which animal models have been chosen, appropriately controlled, and immunologically challenged after initial vaccination or infection with heterologous flaviviruses. Furthermore, using VNTs, the neutralizing capacities of sera obtained from vaccinated target species can be analysed and may also provide the scientific and medical community with valuable information. Haemorhous mexicanus) and red-winged black birds (Agelaius phoeniceus), as well as four mammal species, Syrian golden hamsters (Mesocricetus auratus), Swiss mice (Mus musculus), bonnet macaques (Macaca radiata) and pigs (Sus domesticus). The major results of studies addressing this topic are summarized in Several animal models have been used to assess the level of heterologous protection against flaviviruses; these models include two epidemiologically important bird species, house finches . This protective effect was readily observed for flaviviruses belonging to the same serocomplex.in vitro neutralization capacity of human sera sampled from vaccinated individuals. Mansfield et al. [Credible data on heterologous protection in the field have mainly been obtained by studying the d et al.  used PRN®) compared to that of live-attenuated JEV vaccines (the SA-14-14-2 strain used in China) stress the importance of adjuvant formulation in the induction of high-quality heterologous immunity by inactivated flavivirus vaccines [It was clear that, in humans, vaccination against TBEV and JEV could elicit an antibody response capable of limited WNV neutralization. Although this study did not control for variables such as the age of the subjects or the time between YFV vaccination and blood sampling, the results suggested that the additional vaccination against YFV enhanced the ability of sera to neutralize WNV . This fivaccines ,178. et al. [Most individuals vaccinated against TBEV demonstrated a LIV neutralizing response. There is currently no human vaccine available for tick-borne flaviviruses, apart from TBEV, but the results presented by Mansfield et al.  suggest et al. .Cross-reactivity among antibodies against flaviviruses could significantly contribute to the development of effective broad-spectrum human vaccines against WNV and other existing or emerging flaviviruses. ChimeriVax technology has utilized this cross-reactivity to its advantage in the development of vaccine candidates ,180. UltThe results of all of the studies presented in in vitro, and is still the subject of debate for a few viruses, including Flavivirus species such as DENV. The most severe form of the disease, dengue hemorrhagic fever or shock syndrome (DHF/DSS), mainly occurs after two or more consecutive infections with different DENV serotypes  [in vitro using rabbit hyperimmune antisera developed against a wide range of flaviviruses, including members of both the JEV and TBEV serocomplexes, whereas the ADE of TBEV infections is only elicited in vitro by members of its own serocomplex [In some instances, the presence of cross-reacting antibodies acquired during a primary infection could increase the infectivity and exacerbate the disease outcome of a second, antigenically-related virus. This phenomenon, called ADE, has been observed es, 1–4) ,182,183 ocomplex . On the ocomplex  and/or eocomplex  restrictocomplex . in vitro and in vivo [As previously mentioned, human vaccines against flaviviruses  could ensure partial cross-protection against heterologous flaviviruses within the same serocomplex. At the same time, there is limited experimental evidence of ADE subsequent to vaccination and virus challenge. In mice, antibodies elicited by inactivated-JEV vaccines could enhance pathogenesis via ADE when mice were challenged with a heterotypic flavivirus such as MVEV . Consequ in vivo .European countries are currently facing clinical outbreaks or silent circulation of a wide diversity of flaviviruses, and it is expected that circumstances will become even more complex in the coming years as human travel continues to intensify, the trade of animals and goods facilitate virus emergence through the importation of infected vectors and/or reservoir hosts ,186, and


PLOS Biology, a research article describes a multi-scale in vivo systems approach to determine precisely how the gut epithelium responds to an inflammatory cytokine, tumor necrosis factor-alpha (TNF-α), given by the intravenous route. This article reveals a previously unknown pathway in which several cell types and their secreted mediators work in unison to prevent epithelial cell death in the mouse small intestine. The results of this interesting study illustrate how in vivo systems biology approaches can be used to unravel the complex mechanisms used to protect the host from its environment.An intricate network of innate and immune cells and their derived mediators function in unison to protect us from toxic elements and infectious microbial diseases that are encountered in our environment. This vast network operates efficiently by use of a single cell epithelium in, for example, the gastrointestinal (GI) and upper respiratory (UR) tracts, fortified by adjoining cells and lymphoid tissues that protect its integrity. Perturbations certainly occur, sometimes resulting in inflammatory diseases or infections that can be debilitating and life threatening. For example, allergies in the eyes, skin, nose, and the UR or digestive tracts are common. Likewise, genetic background and environmental microbial encounters can lead to inflammatory bowel diseases (IBDs). This mucosal immune system (MIS) in both health and disease is currently under intense investigation worldwide by scientists with diverse expertise and interests. Despite this activity, there are numerous questions remaining that will require detailed answers in order to use the MIS to our advantage. In this issue of  The first view of the MIS is a single-layer epithelium covered by mucus and antimicrobial products and fortified by both innate and adaptive components of host defense  in order to protect the vast surfaces bathed by external secretions  are of central importance in host defense by providing both a physical barrier and innate immunity. For example, goblet cells secrete mucus, which forms a dense, protective covering for the entire epithelium . Perista+) B cells, and a subepithelial area with antigen-presenting cells (APCs), including dendritic cells (DCs) for the initiation of specific immune responses (4β7 and CCR9) on activated T cells for subsequent migration through the lymphatics, the bloodstream, and into the GI tract lamina propria The MIS, simply speaking, can be separated into inductive and effector sites based upon their anatomical and functional properties. The migration of immune cells from mucosal inductive to effector tissues via the lymphatic system is the cellular basis for the immune response in the GI, the UR, and female reproductive tracts . Mucosalesponses . The MALesponses . The DCsesponses . RetinoiGALT (gut-associated lymphoid tissues)Peyer's patches (PPs)Mesenteric lymph nodes (MLNs)Isolated lymphoid follicles (ILFs)NALT Tonsils/adenoidsInducible bronchus-associated lymphoid tissue (iBALT)Cervical lymph nodes (CLNs)Hilar lymph nodes (HLNs)+ T cell help (provided by both CD4+ Th2 or CD4+ Th1 cells), which supports the development of IgA-producing plasma cells  contain Ag-specific mucosal effector cells such as IgA-producing plasma cells, and memory B and T cells ma cells . Again, ma cells . Release+ Th1 and Th2, CD8+ cytotoxic T lymphocytes (CTLs), and Ab responses in the bloodstream, which are predominantly of the IgG isotype It should be emphasized that several unique vaccine strategies are being developed to induce protective mucosal immunity. In this regard, delivery of mucosal vaccines by oral, nasal, or other mucosal routes requires specific adjuvants or delivery systems to initiate an immune response in MALT PLOS Biology, Lau et al. used a multi-scale in vivo systems approach to assess how cells of the intestinal MIS communicate with intestinal ECs in response to an inflammatory signal In this issue of Several unexpected discoveries followed. First, both goblet and Paneth cells were the major sources of MCP-1, and not the lymphoid cell populations that normally produce this chemokine . Second,The model developed by Lau et al. Finally, the intriguing question arising from the Lau et al. study


Fusarium, Pythium, or Phytophthora are infamous for being vicious parasites that can devastate entire harvests  genes, which are expressed in both shoots and roots. Intriguingly, roots were susceptible to various H. arabidopsidis strains independent of the presence of R-genes, indicating that both organs utilize a distinct defense machinery which is independent of R-genes -thiadiazole-7-carbothioic acid S-methyl ester (BTH) had no protective effect against M. oryzae—in contrast to the BTH-treated foliage  and abscisic acid (ABA), and the pathogen-induced metabolomics profile of roots is different from shoots  protected against fungal pathogens? Using an evolutionary and ecological approach, organ-specific defense systems could be explained by positive or negative feedback mechanisms between the microbial communities and given plant species. The environment plants are exposed to is highly determinant for the outcome of ecological interactions; comparing soil and air, it becomes obvious that belowground and aboveground plant parts are confronted to completely disparate microbial conditions. The composition of these different conditions likely affects the evolutionary development of organ-specific plant-microbe interactions. For instance, due to the viscosity of the environment, soil microbes are usually highly spatially distributed, thus having likely an effect on the very same plant species on which they accumulate. This could explain why in most of the cases negative effects of soil pathogens are host specific (Bever et al., M. oryzae than leaves? Proteomic and metabolomic studies of roots under fungal attack corroborate the fact that roots often have higher levels of antimicrobial compounds. However, these higher levels do not necessarily mean a more efficient induction of defenses. In addition, pathogens are also subjected to an intimate co-evolution with their hosts, and the plant-soil feedback results in a spatial and ecological allocation of soil-born microbes. Fungi that are able to detoxify microbial compounds or even make use of them to target nutrient-rich root tissues are favored in a dynamic root community. Thus, to further study organ-specific plant immunity, it is inevitable to elucidate the dynamics of both plant and pathogens during above- and belowground infection incidents. For a research agenda of plant immunity, analyzing the whole plant and generating a concept of a “defense in depth” is an immediate task. An additional important future quest is the elucidation of systemic defenses upon local shoot and root pathogen attack. Extensive knowledge is available for root interactions with non-pathogenic microbes such as mycorrhizal fungi (Liu et al., vice versa. It was proposed that roots can act as dynamic storage organ for defensive compounds (Erb et al., vice versa communication, a phenomenon notably observed in herbivore defense signaling in maize, were aboveground caterpillar feeding induces the belowground accumulation of the cysteine protease Mir1-CP (Luthe et al., Dissecting complex soil-born microbe communities has become a more feasible task due to novel high-resolution root microbe profiling methods (Bulgarelli et al., vice versa communication during pathogen attack.Roots are a crucial organ, and uncovering belowground defense mechanisms has a great potential being exploited for aboveground plant defense. Therefore, it is time to dig much deeper into belowground plant defense mechanisms, to finally understand better why plant organs are so different, which mechanisms are mediating these differences, and what is the setup of above-belowground and


Cancer of the parotid gland is relatively rare, but carries poor prognosis owing to its prevailing distant metastases. In addition to the disease's basic epidemiology and pathology, we review some current discoveries of its tumorigenesis molecular mechanism. Based on published salivary gland cancer clinical trial data, non-surgical antitumor efficacies amongst a range of chemotherapy, radiation, and concurrent therapy regimens are compared. We also present the current development status of novel radiation therapy and targeted therapeutics, focusing on intensity-modulated radiation therapy (IMRT), and epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) blockages, which are showing promise for improving parotid gland cancer management. The salivary glands are important organs in organisms since they serve as exocrine glands in the secretion of saliva and the enzyme amylase into the oral cavity to facilitate mastication and swallowing. There are three pairs of major salivary glands: the sublingual glands that are located beneath the tongue, the submandibular glands that are located below the lower jaw, and the parotid glands that are located in front of the ears and extend to the area beneath the earlobe along the lower border of the jawbone. The parotid glands are the body's largest salivary glands  occur in the parotid glands, which are the largest among the three sets of major salivary glands, 10% arise in the submandibular glands, and 15% are located in minor salivary glands of the upper digestive tract, less than 1% present in the sublingual glands . Only ab5% occur Partly owning to the rarity of parotid gland cancer, its etiology has not been thoroughly studied and the factors responsible for its carcinogenesis are unclear. Exposures to tobacco smoke and alcohol intake have not been found consistently associated with its development. However, one of the well-established risk factors is exposure to ionizing radiation, as supported by studies on atomic bomb survivors . Linear Mucoepidermoid carcinoma is most common cancer in the parotid gland. Approximately 50% of submandibular gland cancers are adenoid cystic carcinomas. Minor salivary gland cancers are most often adenoid cystic carcinomas and adenocarcinomas, not otherwise classified . Table 1The origin of parotid and other salivary gland cancers is still debated. Possibly, they are derived from both epithelial and mesenchymal elements, which may explain their variable patterns  . This prIn humans, the epidermal growth factor receptor (EGFR) is a cell-surface receptor that is activated by binding of its specific ligands, including members of the epidermal growth factor (EGF) family of extracellular protein ligands ,18. UponGiven the essential role for VPS4B in MVB maturation, it is speculated that loss of VPS4 function might promote tumorigenesis through its effect of prolonging the duration of EGFR signaling  and of the tumor, including a cuff of histologically normal tissue for adequate margins, is the mainstay treatment for parotid gland tumors. When there is direct extension of the primary tumor into the neck, neck dissection is necessary. The surgery can be complicated because several important nerves are located in and around the gland including the facial nerve (VII), which controls most facial movements. Malignant deep lobe parotid gland tumors require postoperative radiotherapy (RT) owing to the limitations of surgical margins in their resection. RT and chemotherapy/RT can also be considered as an adjuvant setting for tumors of intermediate or high grades. Studies ,29 indicChemotherapy is usually for palliation or confined to advanced disease. Responses have been reported after single-agent chemotherapy and polychemotherapy. Various agents, such as cisplatin, paclitaxel, cyclo-phosphamide, doxorubicin, mitoxantrone, carboplatin, and vinorelbine, and combinations of these have been shown to be active for some malignant histologies . Table 2Although chemotherapy alone does not improve survival rates, the integration of radiation and chemotherapy has been shown to increase local control and represents an improvement in the management of parotid gland malignancies. Chemotherapy improves radiotherapy efficacy through its radio-sensitizing ability, and at the same time provides adjuvant systemic therapy against distant micro-metastasis . Some ofSimilar to those for other tumors, treatment selections for parotid gland tumor is largely dependent upon the extent and the pathology of the primary tumor as ascertained by clinical examination, pathology, and interpretation of appropriate radiographic images. According to the National Comprehensive Cancer Network (NCCN) 2011 Clinical Practice Guidelines in Oncology: Head and Neck Cancers , completFor parotid gland carcinomas T3 and above, further surgical evaluation of local invasion or regional lymph node metastasis has to be performed. In the case of carcinoma T4b, it is either no surgical resection would be possible, or surgical resection is not recommended. Definitive radiation therapy or radiation therapy with systemic chemotherapy is recommended.0  tumors, parotidectomy with complete excision of tumor with or without neck dissection for high-grade and high-stage tumors is suggested, while the clinical N+  require parotidectomy and neck dissection. In the case of incomplete excision with gross residual disease during surgery, definitive radiation therapy or chemoradiation therapy is recommended. Even for complete excision, adjuvant radiation or chemoradiation therapy should also be considered.Among the clinical NOne of the reported side effects of radiation as treatment for parotid gland cancer is hearing loss. Clinical trials have been underway to determine whether intensity-modulated radiation therapy (IMRT) that spares the cochlear is more effective than conventional three-dimensional conformal radiation therapy (3D-CRT) in reducing sensory-neural hearing loss in patients who have radiotherapy treatment in the parotid gland region. Data are still being collected before definitive clinical guidelines can be put in place. Compared with IMRT and 3D-CRT, the new radiation treatment method of intensity-modulated proton therapy (IMPT) allows for optimal dose distribution to the local target, resulting in a dose reduction and improved sparing of the organs at risk, while keeping similar target coverage results . Its potThanks to the advances in molecular biology and our better understanding of the molecular mechanisms underlying head and neck cancers, including parotid gland cancer, new targeted therapeutics and novel agents are also being developed for the systemic treatment to them. The epidermal growth factor receptor (EGFR) is one of the major targets under intensive investigation since it has been found to be overexpressed in head and neck squamous cell carcinoma. This overexpression has been linked to disease recurrence in which EGFR-dependent signaling pathways are activated, leading to tumor cell proliferation and anti-apoptosis. EGFR blockade has hence been proposed to inhibit tumor growth. Cetuximab , an immuAlthough parotid gland cancer is relatively rare, it still constitutes as a serious health hazard burdening our population because of its poor prognosis. Twenty percent of all patients will develop distant metastases despite its large variety of histologic types. Distant metastases usually correspond to a poor prognosis with a median survival of 4 · 3-7 · 3 months . Patient3D-CRT: Three-dimensional conformal radiation therapy; ATPase: Adenosine triphosphate enzyme; CRT: Chemoradiotherapy; EGF: Epidermal growth factor; EGFR: Epidermal growth factor receptor; ESCRT: Endosomal sorting complexes required for transport; IMPT: Intensity-modulated proton therapy; IMRT: Intensity-modulated radiation therapy; MVB: Multi-vesicular body; RT: Radiotherapy; VEGF: Vascular endothelial growth factor; VPS: Vacuolar protein sorting; VPS4B: Vacuolar protein sorting-associated protein 4B.The authors declare that they have no competing interests.KH did literature review and wrote the paper. HL and DA devised the proposed tumorigenesis mechanism. PC provided the pathology images. YY conceptualized and designed the paper. All authors read and approved the final manuscript.