Cytotoxic T cell responses in lambs experimentally infected with Border disease virus.

Mononuclear cells cytotoxic to a noncytopathic strain of Border disease virus (BDV) but not to uninfected cells were detected in the peripheral blood of experimentally infected lambs, 10 days after experimental infection, reaching peak levels of cytotoxicity 15 days post-inoculation. The specificity of the cytotoxic activity to BDV-infected cells was tested by including autologous targets infected with another virus (bovine respiratory syncytial virus, BRSV) and normal uninfected autologous targets. The cytotoxic T cells were virus-specific, as only autologous BDV-infected targets were lysed, whereas autologous targets infected with BRSV and uninfected targets were not lysed. The present results also suggest that the cytotoxic activity was largely MHC-restricted as the specific release from BDV-infected autologous targets was significantly higher than that of BDV-infected heterologous targets (P < 0.001) and the cytotoxicity against BDV-infected homologous targets was significantly reduced by the selective depletion of OvCD8+ T cells (P < 0.001).