Interferon-Gamma Modulation of the Local T Cell Response to Alphavirus Encephalomyelitis

Infection of mice with Sindbis virus (SINV) provides a model for examining the role of the immune response to alphavirus infection of the central nervous system (CNS). Interferon-gamma (IFN-gamma) is an important component of this response, and we show that SINV-infected differentiated neurons respond to IFN-gamma in vitro by induction of antiviral genes and suppression of virus replication. To determine the in vivo effects of IFN-gamma on SINV clearance and T cell responses, C57BL/6 mice lacking IFN-gamma or IFN-gamma receptor-1 were compared to wild-type (WT) mice after intracranial SINV infection. In WT mice, IFN-gamma was first produced in the CNS by natural killer cells and then by CD4(+) and CD8(+) T cells. Mice with impaired IFN-gamma signaling initiated clearance of viral RNA earlier than WT mice associated with CNS entry of more granzyme B-producing CD8(+) T cells. However, these mice established fewer CD8(+) tissue-resident memory T (T-RM) cells and were more likely to experience reactivation of viral RNA synthesis late after infection. Therefore, IFN-gamma suppresses the local development of granzyme B-expressing CD8(+) T cells and slows viral RNA clearance but promotes CD8(+) T-RM cell establishment.