Papillomavirus infection in XXXX : viral and chemical cofactors in naturally occurring and experimentally induced @entity5 .

@entity500 @entity5 @entity1185 @entity957 @entity5426 @entity5905 @entity10368 @entity189 @entity420 @entity281 @entity150 @entity15882 @entity652 @entity291 @entity5772
Six different types of @entity291 papillomavirus ( @entity10368 to @entity15882 -6) have been identified and classified into two subgroups: subgroup A, which induce fibropapillomas, and subgroup B, which induce true @entity1185 . @entity5905 , a member of subgroup B, is the aetiological agent of @entity1185 of the upper alimentary canal, which can become a focus for transformation to @entity957 in animals feeding on bracken fern. Strong circumstantial evidence suggests that the progression to @entity5 is due to the interplay between @entity5905 and carcinogen(s) present in the fern. The @entity189 of the upper alimentary canal are often accompanied by @entity652 and @entity420 of the lower bowels, and by @entity189 and @entity5426 of the urinary bladder. Bracken-grazing animals are also heavily immunosuppressed. Florid @entity1185 of the @entity5 of the urinary bladder have been experimentally reproduced in animals either kept on a diet of bracken or immunosuppressed with @entity500 . Several @entity150 contained multiple episomal copies of @entity10368 DNA, suggesting that this virus, or its genome, can be present in a latent form, and that it can be implicated in malignant transformation. Further indication of @entity281 is provided by the onset of skin warts in @entity1185 -free animals. These warts developed at sites of damaged skin and harboured either @entity10368 or @entity10368 . @entity5905 DNA has not been found in the naturally occurring @entity5 of the upper alimentary canal and of the lower bowels, except in one @entity5772 and one @entity1185 , indicating that the viral genome is not required for the maintenance of the malignant state in the alimentary canal.
