title: Implications for gene therapy-limiting expression of IL-2R gamma c delineate differences in signaling thresholds required for lymphocyte development and maintenance.
abstract: X-linked SCID patients are deficient in functional IL-2Rgamma(c) leading to the loss of IL-2/IL-4/IL-7/IL-9/IL-15/IL-21 signaling and a lack of NK and mature T cells. Patients treated with IL-2Rgamma(c) gene therapy have T cells develop; however, their NK cell numbers remain low, suggesting antiviral responses may be compromised. Similarly, IL-2Rgamma(c)(-/-) mice reconstituted with IL-2Rgamma(c) developed few NK cells, and reconstituted T cells exhibited defective proliferative responses suggesting incomplete recovery of IL-2Rgamma(c) signaling. Given the shift toward self-inactivating long terminal repeats with weaker promoters to control the risk of leukemia, we assessed NK and T cell numbers and function in IL-2Rgamma(c)(-/-) mice reconstituted with limiting amounts of IL-2Rgamma(c). Reconstitution resulted in lower IL-2/-15-mediated STAT5 phosphorylation and proliferation in NK and T cells. However, TCR costimulation restored cytokine-driven T cell proliferation to wild-type levels. Vector modifications that improved IL-2Rgamma(c) levels increased cytokine-induced STAT5 phosphorylation in both populations and increased NK cell proliferation demonstrating that IL-2Rgamma(c) levels are limiting. In addition, although the half-lives of both NK and T cells expressing intermediate levels of IL-2Rgamma(c) are reduced compared with wild-type cells, the reduction in NK cell half-live is much more severe than in T cells. Collectively, these data indicate different IL-2Rgamma(c) signaling thresholds for lymphocyte development and proliferation making functional monitoring imperative during gene therapy. Further, our findings suggest that IL-2Rgamma(c) reconstituted T cells may persist more efficiently than NK cells due to compensation for suboptimal IL-2Rgamma(c) signaling by the TCR.
authors.affiliation: Cancer and Inflammation Program, National Cancer Institute-Frederick, Frederick, MD 21702, USA.
authors.forename: Selinda J
authors.initials: SJ
authors.lastname: Orr
authors.forename: Stephen
authors.initials: S
authors.lastname: Roessler
authors.forename: Laura
authors.initials: L
authors.lastname: Quigley
authors.forename: Tim
authors.initials: T
authors.lastname: Chan
authors.forename: Jill W
authors.initials: JW
authors.lastname: Ford
authors.forename: Geraldine M
authors.initials: GM
authors.lastname: O'Connor
authors.forename: Daniel W
authors.initials: DW
authors.lastname: McVicar
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology*; D049109:Cell Proliferation; D005786:Gene Expression Regulation / Q000276:immunology*; D015316:Genetic Therapy / Q000379:methods*; D053631:Interleukin Receptor Common gamma Subunit / Q000096:biosynthesis* / Q000172:deficiency / Q000235:genetics*; D019409:Interleukin-15 / Q000037:antagonists & inhibitors / Q000502:physiology; D007376:Interleukin-2 / Q000037:antagonists & inhibitors / Q000502:physiology; D007694:Killer Cells, Natural / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016513:Mice, SCID; D010766:Phosphorylation / Q000235:genetics / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D050799:STAT5 Transcription Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D016511:Severe Combined Immunodeficiency / Q000235:genetics / Q000276:immunology / Q000628:therapy; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D014161:Transduction, Genetic
chemical_list: D053631:Interleukin Receptor Common gamma Subunit; D019409:Interleukin-15; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell; D050799:STAT5 Transcription Factor