The effect of vaccination on the response to experimental infection with bovine respiratory syncytial virus infection in calves

by West, Keith Henry

Bovine respiratory syncytial virus (BRSV) is an important respiratory pathogen of cattle. Both inactivated and modified live virus (MLV) BRSV vaccines are currently in use. Vaccine eficacy, the significance of qualitative differences in antibody responses, and the correlates of immunity to BRSV infection, remain unexarnined by a virulent experimental challenge. This thesis addressed these issues. The functional properties of antibodies induced by a MLV and 3 inactivated BRSV vaccines were compared in feedtot calves (n=10 per group)(trial 1). A challenge mode1 that induces severe clinical disease and pulrnonary pathology was developed by serially passing a field isolate of BRSV in newbom calves, using lung washing as the challenge inoculum. The effect of vaccination on BRSV infection was investigated. In trial 2, BRSV naïve calves were vaccinated twice with a formalin inactivated (FI) vaccine, 1 O' ph MLV or sham vaccinated (n=4 per group). In trial 3, calves were vaccinated with either 2 doses of MLV intramuscularly (IM) or intradermally. with a single dose IM of MLV or MLV with an adjuvant (four groups, n = 6 per group), or were unvaccinated (n = 9). Calves were challenged 34 days (trial 2) or 3 weeks (trial 3) after the second or only vaccination.