ANTIBODY-RESPONSES AGAINST EPITOPES ON THE F-PROTEIN OF BOVINE RESPIRATORY SYNCYTIAL VIRUS DIFFER IN INFECTED OR VACCINATED CATTLE

The fusion protein F of bovine respiratory syncytial virus (BRSV) is a n important target for humoral and cellular immune responses, and anti bodies against the F protein have been associated with protection. How ever, the F protein can induce antibodies with different biological ac tivity, possibly related to distinct antigenic regions on the protein. Therefore, epitopes were mapped on the F protein using monoclonal ant ibodies. Two epitopes (A and B) were identified that induced neutraliz ing antibodies, and one epitope (C) that did not elicit neutralizing a ntibodies. Subsequently, antibody responses were analysed against thes e epitopes in cattle sera after natural infection, experimental infect ion or vaccination. After natural infection or reinfection, the antibo dy titres against epitope A were significantly higher than those again st epitope B or C. After experimental infection and after vaccination with an inactivated vaccine, antibody titres against epitope B and C w ere significantly higher than after natural infection. Conversely, vir us neutralizing antibody titres were significantly lower in these anim als with higher antibody titres against epitopes B and C than in natur ally infected cattle. Because after natural infection the epitope-spec ific-antibody titres against epitope A, B or C differed markedly betwe en the cattle, the magnitude of the antibody titres against epitope A, B or C in relation to the major histocompatibility complex (MHC) gene s of cattle (BoLA) was studied. The magnitude of the antibody response s against epitope A of the F protein, but not against the G protein, a ppeared to be associated with the bovine lymphocyte antigen (BoLA) hap lotype.