title: Overexpression of interleukin-15 compromises CD4-dependent adaptive immune responses against herpes simplex virus 2.
abstract: Interleukin-15 (IL-15) is necessary for the development and function of NK/NKT cells and the maintenance of naive and memory CD8(+) T cells. In the absence of IL-15, protective innate immunity is not available; however, a functional adaptive immune response against vaginal herpes simplex virus 2 (HSV-2) is generated. Mice overexpressing IL-15 (IL-15tg mice) have higher numbers of NK cells, greater NK-derived gamma interferon, and more CD8(+) T cells. Here we examined the consequences of IL-15 overexpression for innate and adaptive immunity against genital HSV-2. Surprisingly, IL-15tg mice immunized against HSV-2 were not protected against genital HSV-2 challenge compared to control immunized mice. IL-15tg mice had a higher frequency of NK cells in the genital mucosa than control mice. However, immunized IL-15tg mice had significantly lower numbers of HSV-2-specific CD4(+) T cells than B6 mice. We then confirmed that CD4(+) T cells, but not CD8(+) T cells, are essential for protection against intravaginal HSV-2 challenge. Since we observed less protection in immunized IL-15tg mice, we then examined if the adaptive immune responses generated in an environment with overexpression of IL-15 could provide protection against HSV-2 in an environment with normal levels of IL-15 expression. We adoptively transferred immunized cells from IL-15tg and B6 mice into naive RAG-1(-/-) mice and found that the cells from immunized IL-15tg mice were able to provide protection in this IL-15-normal environment. Our data suggest that overexpression of IL-15 results in a reduced CD4(+) T cell-mediated adaptive immune response against genital HSV-2.
authors.affiliation: Department of Pathology and Molecular Medicine, Centre for Gene Therapeutics, McMaster University Health Sciences Centre, Hamilton, Ontario, Canada.
authors.forename: Navkiran
authors.initials: N
authors.lastname: Gill
authors.forename: Ali A
authors.initials: AA
authors.lastname: Ashkar
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D005260:Female; D005835:Genitalia / Q000166:cytology / Q000276:immunology; D006558:Herpes Genitalis / Q000276:immunology*; D018258:Herpesvirus 2, Human / Q000276:immunology*; D007116:Immunization, Passive; D019409:Interleukin-15 / Q000276:immunology*; D007694:Killer Cells, Natural / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009092:Mucous Membrane / Q000166:cytology / Q000276:immunology; D016019:Survival Analysis
chemical_list: D019409:Interleukin-15