T cell-mediated restriction of intracerebral murine cytomegalovirus infection displays dependence upon perforin but not interferon-γ

The authors have previously reported that adoptive transfer of splenocytes suppresses murine cytomegalovirus (MCMV) brain infection following intracerebroventricular injection of immunodeficient mice and that depletion of Thy 1.2(+) T lymphocytes abolishes this suppressive effect. Here the authors report that splenocytes depleted of CD4(+) T lymphocytes prior to adoptive transfer retained their ability to control viral expression in the brain. In sharp contrast, depletion of the CD8(+) T-cell population prior to transfer abolished the suppressive effect, with sixfold greater expression in the brain than when undepleted splenocytes were used. The authors went on to examine the contributions of cytokine- and perforin-mediated mechanisms in controlling MCMV brain infection using splenocytes from major histocompatibility (MHC)-matched IFN-γ-knockout (GKO), and perforin-knockout (PKO) mice. When used in adoptive transfer studies, splenocytes from GKO mice controlled viral expression; however, cells from PKO mice could not control reporter gene expression or viral DNA replication in brain tissues. The authors have previously reported that the levels of the T-cell chemoattractant CXCL10 are highly elevated in the brains of MCMV-infected mice. Here the authors found that the receptor for this ligand, CXCR3, was not essential in mediating the suppressive effects of adoptive transfer. These data indicate that peripheral CD8(+) T cells control MCMV brain infection through a perforin-mediated mechanism and that neither IFN-γ nor CXCR3 play a critical role in this neuroprotective response.