Isotype-specific antibody responses in sera and mucosal secretions of calves experimentally infected with bovine herpesvirus 1.

Enzyme-linked immunosorbent assays (ELISAs) were developed for studying the kinetics of isotype-specific antibody responses in sera, nasal, ocular and genital secretions of calves infected with bovine herpesvirus 1 (BHV1). The BHV1-specific IgM and IgA antibodies were measured in antibody capture assays, and the IgG1 and IgG2 antibodies in indirect double antibody sandwich assays. The ELISAs were shown to be isotype-specific, sensitive and reproducible. Antibodies of all isotypes were able to neutralise the virus in vitro. Calves were infected intranasally with one of seven BHV1 field strains. Nine to 13 days after infection BHV1-specific antibodies of the IgM isotype appeared in serum, nasal and ocular secretions and these were detectable until four weeks after infection. The first IgA antibodies were detected a few days later than the IgM antibodies. In serum the IgA antibodies were no longer detectable after 3 weeks, but these did persist for prolonged periods in mucosal secretions. The calves developed a uniform IgG1 response from 13 days after infection, but the IgG2 response was quite variable; both persisted until the end of the experiment. No antibody responses were detected in genital secretions. There were no marked differences in isotype responses between calves infected with different strains of BHV1.