Antigen-specific in vitro activation of T-lymphocyte subsets of cattle immunized with a modified live bovine herpesvirus 1 vaccine.

Bovine peripheral blood mononuclear cells from cattle immunized with a modified live virus bovine herpesvirus 1 (BHV1) vaccine and from BHV1-negative cattle were incubated in vitro with inactivated BHV1 for 6 days. Activation of T-lymphocyte subsets was measured by two-color flow cytometric analysis of T-cell phenotype and surface expression of CD25, the alpha-subunit of the high-affinity interleukin-2 receptor. Vaccinated animals, but not unvaccinated animals, had CD3+, CD4+, and gamma-delta T cells that significantly (p < 0.05) increased expression of CD25 when incubated with BHV1. CD8+ T cells from vaccinated animals did not consistently increase CD25 expression when incubated with inactivated BHV1.