Lymphocyte Proliferative Responses to Recombinant Bovine Herpes Virus Type 1 (BHV-1) Glycoprotein gD (gIV) in Immune Cattle: Identification of a T Cell Epitope

The lymphocyte proliferative response to BHV-1 in immune cattle was compared to recombinant wild-type gD and truncated gD produced from recombinant vaccinia viruses. The response exhibited by recombinant proteins was comparable to the response induced by BHV-1 suggesting that gD is the major target structure for stimulation of bovine lymphocytes. Analysis of the proliferative response using vaccinia virus vectors expressing various modified forms of gD identified a region between residues 165 and 216 recognized by T-lymphocytes of immune cattle. Further analysis by overlapping peptides in this region localized the T cell epitope to residues 161–172. Antibody-blocking studies demonstrated that lymphocytes responding to this epitope are CD4⁺. In addition, lymphocytes stimulated with gD or peptide 77 (residues 161–172) also produced IFN-γ and IL-2.