Studies on the Immune Response to Bovine Herpesvirus Type 4 (BHV-4) in Cattle

Systemic cell mediated, systemic antibody, and local antibody responses were evaluated in cattle inoculated with bovine herpesvirus type 4 (BHV-4). Experiment 1 was designed to evaluate an in vitro lymphocyte transformation assay to quantitate the response of peripheral blood leukocytes (PBL) from cattle to BHV-4 infected target cells. Three types of target cells, bovine embryonic lung, bovine skin fibroblast-13, and Vero, were inoculated with BHV-4 at different multiplicities of infection and fixed in glutaraldehyde to retain BHV-4 surface antigens. Optimum effector to target cell ratios and length of incubation for the assay were also determined. Vero cells infected at an MOI of 50 and incubated with PBL for 6 days was optimal for in vitro blastogenesis. Stimulation indices and net counts per minute which were significantly different from preinoculation values were noted following inoculation of adult cows in Experiment 1. Experiment 2 was designed to detect PBLs sensitized to BHV-4 membrane antigens as well as humoral and nasal antibody responses in calves inoculated by either the intranasal-intratracheal (IN, IT) or the intramuscular route (IM). Stimulation indices and net counts per minute obtained following inoculation with BHV-4 by either route were not significantly different from those obtained for uninoculated control calves. Local antibody to BHV-4 in the nasal cavities was measured by an indirect fluorescent antibody procedure and appeared 7 to 10 days after IN, IT inoculation only. Humoral antibody appeared 10 to 14 days after primary inoculation in both groups. Secondary challenge with BHV-4 by the same route resulted in a four-fold increase in humoral antibody for both IN, IT and 1M-inoculated calves at 2 to 4 days following reexposure. A four-fold increase in nasal antibody was only demonstrated after secondary IN, IT challenge