title: NK and NKT cell-independent contribution of interleukin-15 to innate protection against mucosal viral infection.
abstract: Interleukin-15 (IL-15) is essential for the development, maturation, and function of NK and NKT cells, which are critical components of the innate immune defense against viral infections. We recently showed that mice lacking IL-15 and/or NK/NKT cells are significantly more susceptible to intravaginal (IVAG) herpes simplex virus type 2 (HSV-2) infection than control mice. For this study, we examined whether IL-15 has any direct antiviral activity, independent of NK/NKT cells, in innate protection against HSV-2 infection. A sensitive enzyme-linked immunosorbent assay for murine IL-15 was developed and used to show that IVAG HSV-2 infection induces IL-15 in vaginal washes. Using immunohistochemistry, we detected IL-15-positive cells in the submucosa and vaginal epithelium following IVAG HSV-2 infection. Local, but not systemic, delivery of murine recombinant IL-15 (mrIL-15) to the genital mucosae of IL-15(-/-) and RAG-2(-/-) gamma(c)(-/-) mice, which both lack NK and NKT cells, resulted in significant reductions in HSV-2 titers in genital washes and 60% survival following IVAG HSV-2 challenge. Furthermore, we showed that IL-15 is important for CpG oligodeoxynucleotide (ODN)-induced innate protection against genital HSV-2 infection. While 100% of CpG ODN-treated RAG2(-/-) gamma(c)(-/-) mice, which are capable of producing IL-15 but lack NK/NKT cells, survived an IVAG HSV-2 challenge, only 60% of CpG ODN-treated IL-15(-/-) mice survived, and all of these mice had similar vaginal viral titers to those in control mice by day 3 postchallenge. Lastly, a treatment of RAW264.7 cells with mrIL-15 induced the production of tumor necrosis factor alpha and beta interferon (IFN-beta), but not IFN-alpha, and significantly protected them against HSV-2 infection in vitro. The results of these studies indicate that IL-15 can act independently of NK/NKT cells in mediating the innate defense against viral infection.
authors.affiliation: Centre for Gene Therapeutics, Department of Pathology and Molecular Medicine, McMaster University Health Sciences Centre, Hamilton, Ontario, Canada.
authors.forename: Navkiran
authors.initials: N
authors.lastname: Gill
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Rosenthal
authors.forename: Ali A
authors.initials: AA
authors.lastname: Ashkar
mesh_terms: D000276:Adjuvants, Immunologic; D000818:Animals; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006558:Herpes Genitalis / Q000276:immunology* / Q000821:virology; D018258:Herpesvirus 2, Human / Q000302:isolation & purification; D007113:Immunity, Innate; D018928:Immunity, Mucosal; D007150:Immunohistochemistry; D016898:Interferon-alpha / Q000096:biosynthesis; D016899:Interferon-beta / Q000096:biosynthesis; D019409:Interleukin-15 / Q000032:analysis / Q000235:genetics / Q000276:immunology*; D007694:Killer Cells, Natural / Q000276:immunology*; D016131:Lymphocyte Subsets / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology; D016019:Survival Analysis; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis; D014621:Vagina / Q000276:immunology / Q000821:virology; D014623:Vaginal Diseases / Q000276:immunology* / Q000821:virology; D010948:Viral Plaque Assay
chemical_list: D000276:Adjuvants, Immunologic; C408982:CPG-oligonucleotide; D016898:Interferon-alpha; D019409:Interleukin-15; D009838:Oligodeoxyribonucleotides; D014409:Tumor Necrosis Factor-alpha; D016899:Interferon-beta