Expansion, purification, and functional assessment of XXXX peripheral blood NK cells.

@entity1 @entity3222 @entity5 @entity14114 @entity1531 @entity3138 @entity44085 @entity3207 @entity15787 @entity1199 @entity8252
Natural killer (NK) cells play an important role in immune surveillance against a variety of infectious microorganisms and @entity5 . Limited availability of NK cells and ability to expand in vitro has restricted development of NK cell immunotherapy. Here we describe a method to efficiently expand vast quantities of functional NK cells ex vivo using K562 cells expressing membrane-bound @entity15787 , as an artificial antigen-presenting cell (aAPC). NK cell adoptive therapies to date have utilized a cell product obtained by steady-state leukapheresis of the donor followed by depletion of T cells or positive selection of NK cells. The product is usually activated in @entity1199 overnight and then administered the following day. Because of the low frequency of NK cells in peripheral blood, relatively small numbers of NK cells have been delivered in clinical trials. The inability to propagate NK cells in vitro has been the limiting factor for generating sufficient cell numbers for optimal clinical outcome. Some expansion of NK cells (5-10 fold over 1-2 weeks) has be achieved through high-dose @entity1199 alone. Activation of autologous T cells can mediate NK cell expansion, presumably also through release of local cytokine. Support with mesenchymal stroma or artificial antigen presenting cells (aAPCs) can support the expansion of NK cells from both peripheral blood and cord blood. Combined @entity3222 and @entity3138 activation by antibody-coated beads is currently marketed for NK cell expansion (Miltenyi Biotec, Auburn CA), resulting in approximately 100-fold expansion in 21 days. Clinical trials using aAPC-expanded or -activated NK cells are underway, one using leukemic cell line @entity1 to prime and activate NK cells without significant expansion. A second trial utilizes EBV-LCL for NK cell expansion, achieving a mean 490-fold expansion in 21 days. The third utilizes a K562-based aAPC transduced with @entity44085 ( @entity44085 ) and membrane-bound IL-15 (mIL-15), which achieved a mean NK expansion 277-fold in 21 days. Although, the NK cells expanded using K562-41BBL-mIL15 aAPC are highly cytotoxic in vitro and in vivo compared to unexpanded NK cells, and participate in @entity14114 , their proliferation is limited by senescence attributed to telomere @entity3207 . More recently a 350-fold expansion of NK cells was reported using K562 expressing @entity1531 , @entity44085 and @entity8252 . Our method of NK cell expansion described herein produces rapid proliferation of NK cells without senescence achieving a median 21,000-fold expansion in 21 days.
