利用ENU突變鼠發現IL-15異構體能影響HSV-1感染後皮膚的發炎反應與CD8+ T細胞的生成

Abstract

Interleukin-15 (IL-15) is a pleiotropic cytokine that plays an important role in mediating innate and adaptive immunity in the host. The pedigree 191 (P191) of the ENU-mutagenized mice, generated by the Mouse Mutagenesis Program Core Facility (MMPCF) has been identified and predominantly express an alternatively spliced IL-15 mRNA called IL-15 ∆E7. Infection of P191 mutant mice via flank skin with herpes simplex virus-1 (HSV-1) showed a much more severely disrupted lesional skin than in B6 wildtype mice accompanied with enhanced HSV viral protein expression as well as elevated expressions of IL-1β and IL-6 in P191 lesional skin by cDNA microarray and real-time PCR analysis. How the function of IL-15 is affected and/or regulated by IL-15 ∆E7 and thus results in the altered inflammatory response against HSV-1 infection will be further investigated. Consistent with the depressed CD44 expression on CD8+ T cells in P191, we also found that the percentages of CD8+ T cells from lymph nodes, spleen and peripheral blood expressing CD44hiCD122hi were reduced in P191 mice by flow cytometric analysis. Using Kb-HSV-gB498-505 tetramer reagent, we found that gB-specific CD8+ T cells were generated in a delayed kinetics in P191 as compared to wildtype mice. However, these gB-specific CD8+ T cells significantly expanded in the spleen of P191 on day 10 after infection and the absolute numbers of gB-specific CD8+ T cells were higher than these in B6 mice, indicating that these cells efficiently proliferated in P191 spleen on early times of infection. In proliferation experiment, CFSE-labeled T cells were stimulated with gB498-505 peptide in rIL-2 and rIL-15. Whereas HSV-primed CD8+ T cells from B6 mice proliferated to gB antigen in vitro, proliferation of HSV-primed CD8+ T cells from P191 was significantly reduced given with sufficient IL-15. This suggested that gB-specific CD8+ T cells generated in P191 were poorly responsive to recall antigen. Using FlowCytomix to profile cytokine expression in B6 and P191 mice after HSV-1 infection, we have found that the level of IFN-γ in spleen was significantly reduced in P191 as compared to B6 spleen. How the reduced production of IFN-γ is associated with less proliferation of antigen-specific CD8+ T cells from P191 requires further investigation. Results from current experiments have shown that inflammatory response in skin and the properties of antigen-specific CD8+ T cells induced by HSV-1 infection are both altered in P191. How expression of IL-15 splice variant is involved in the control of these phenotypes remains to be clarified.