ANTIGEN-SPECIFICITY OF THE OVINE CYTOTOXIC T-LYMPHOCYTE RESPONSE TO BLUETONGUE VIRUS

Bluetongue virus (BTV), an arbovirus transmitted by midges, can cause serious disease in sheep. Both virus neutralizing antibody and cytotox ic T lymphocytes (CTL) have been shown to have a role in protective im munity. In this study, the antigen specificity of CTL from BTV-immune sheep has been determined using recombinant vaccinia viruses expressin g individual BTV antigens. The results show that, in the sheep studied thus far, the serotype-specific outer coat protein, VP2, and the non- structural protein, NS1 are major immunogens for CTL, with VP5 (an out er coat protein) and NS3 being minor immunogens. No VP7 (a major group -reactive inner coat protein) specific CTL were detected. The CTL from sheep immunized with serotype 1 were cross-reactive and able to recog nize target cells infected with other BTV serotypes. Further work demo nstrated that the cross-reactive CTL recognized NS1, but not VP2.