Characterization of T cells expanded in vivo during primary mouse hepatitis virus infection in mice

After intraperitoneal infection with mouse hepatitis virus, strain JHM (JHMV), JHMV replicated in the spleen of C57BL/6 mice for a few days but cleared within a week. The acute viral clearance coincided with moderate expansion of CD8(+)T cells and modest expansion of CD4(+)T cells, and was impaired moderately in mice depleted of CD8(+)T cells and completely in mice depleted of both CD4(+) and CD8(+)T cell subsets. Flow cytometric analysis showed that expression of cell surface markers on the spleen T cells changed during JHMV infection. CD8(+)T cells expressing increased amounts of CD11a, CD43, CD44 and CD49d, and those expressing decreased levels of T cell receptor alpha beta, CD8, CD45RB and L-selectin were expanded in the spleen after JHMV infection. However, they did not express CD11b, CD25 or NK1.1. They used highly heterogenous V beta chains for their T cell receptors. In addition to CD11a(high)CD8(+)T cells, CD11 a(high)CD4(+)T cells were detected transiently after JHMV infection. The virus-specific cytotoxic T lymphocyte (CTL) activity was observed in both CD4(+) and CD8(+) spleen T cells from mice 7 days post-infection. The present study shows the dynamics of CD8(+) and CD4(+)T cells in the spleen during JHMV infection in mice and suggests that CD11a(high)T cells may be involved in JHMV clearance in vivo because their appearance was temporally correlated with T cell-mediated viral clearance in vivo and antiviral CTL activity in vitro.