Exquisite specificity of adoptive immunization in arenavirus-infected mice.

Lymphocytic choriomeningitis virus (LCMV)-infected mice can be adoptively immunized with T cells from immune mice sharing MHC compatibility in H-2K or D, suggesting direct cytotoxic effects of T cells in vivo. However, T cells, upon recognition of an appropriate target, secrete lymphokines which may be capable of mediating antiviral effects nonspecifically. In this report we show that LCMV-immune cells reduced LCMV spleen titers in mice infected with LCMV alone or with LCMV and Pichinde virus (PV), but had no effect on PV titers in these mice or in mice infected with PV alone. Titers of PV were reduced by PV-immune cells transferred into mice infected with PV alone or with PV and LCMV, while LCMV titers were not altered. PV and LCMV antigens were shown by fluorescence microscopy to be in proximity in the spleen prior to cell transfer. These data suggest that adoptive immunization against these arenaviruses involves direct cytotoxicity or an extremely localized effect of nonspecific soluble factors elaborated following antigen recognition, rather than generalized nonspecific antiviral effects of a more systemic nature.