In Vivo Regulation of Murine Cytomegalovirus Infections: The Role of Cell Surface Molecules and Mechanisms of Control by Natural Killer Cells: A Dissertation

The overall aim of this thesis was to determine how natural killer (N) cells regulate virus infections in vivo. Anti-viral mechanisms by which NK cells control murine cytomegalovirus (MCMV) infection in the spleens and livers of adult C57BL/6 mice were first studied, revealing different mechanisms of control in different organs. Three days post-infection, MCMV titers in the spleens of perf orin-deficient (perforin 0/0) mice were higher than in wild type controls, but no elevation of liver titers was found in perf orin 0/0 mice. NK cell depletion in MCMV -infected perf orin % mice resulted only in an increase in liver viral titers but not in spleen titers. Depletion of IFin adult C57BL/6 mice by injections with mAbs to IFresulted in an increase in viral titers in the liver but not in the spleen. Analyses using IF-y-receptor-deficient (IF0/o mice, rendered chimeric with C57BL/6 bone marrow cells, indicated that even though the donor spleen cells could respond to IFy, the depletion ofNK cells in a recipient environment where the host cells could not respond to IFcaused an increase in MCMV titers in the spleens but had little effect in the liver. IFhas the ability to induce a variety of cells to produce nitric oxide (NO), and administrating the nitric oxide synthase (NOS) inhibitor -monomethylarginine (L-NMA) into MCMV-infected adult C57BL/6 mice resulted in MCMV titer increases in the liver but not in the spleen. These data indicate that in adult C57BL/6 mice there is a dichotomy in the mechanisms utilized by NK cells in the regulation ofMCMV in different organs. In the spleen NK cells exert their effects in a perf orin-dependent manner suggesting a cytotoxic mechanism, whereas in the liver the production of IFby NK cells may be a predominant mechanism in the regulation of MCMV synthesis. These results may explain why the Cmv-r (CmvJ-resistant) locus, which maps closely to genes regulating NK cell cytotoxic function, confers an NK cell-dependent resistance to MCMV infection in the spleen but not in the liver. The ability of adoptively transferred cells to protect suckling mice ITom MCMV was another model used to study the mechansms utilized by NK cells in the regulation ofMCMV. Adoptive transfers of 129, C57BL/6 and perfori spleen cells or lymphokine-activated kier (LAK) cells into 4 6 day old MCMV-infected C57BL/6 suckling mice signcantly lowered the splenic MCMV titers in these mice compared to the inected controls. Adoptive transfers ofC57BL/6 spleen cells into MCMV-inected 129 suckling mice also decreased the amount of MCMV in the 129 suckling mice, but C57BL/6 spleen cells could not regulate MCMV synthesis when adoptively transferred into 129/I0/0 suckling mice. These results suggest that, in the sucklg mouse model, the regulation of MCMV by the adoptively transferred NK cells is via an IFdependent, perf orin-independent Cmvindependent mechansm. The CmvJ gene locus resides within the NK gene complex, in close proximity to the Ly49 NK cell receptor famy. Analyses were cared out to determne if any of the 4 known Ly49 NK cell receptors (Ly49A, C, D and G2) played a role in the control ofMCMV synthesis by NK cells. Studies comparg the expression of the different Ly49 NK cell subsets in the