Bovine herpesvirus-1 infection of cattle: kinetics of antibody formation after intranasal exposure and abortion induced by the virus.

The kinetics of antibody formation in Holstein heifers after primary and secondary intranasal inoculation of bovine herpesvirus-1 (BHV-1) and after BHV-1-induced abortion was determined. Sera were fractionated by gel filtration and ion-exchange chromatography. The antibody activity within serum immunoglobulin (Ig) isotypes was assessed, using a plaque-reduction neutralization assay. The primary immune response to BHV-1 infection was characterized by the appearance of IgM and IgG antibodies in serum by postinoculation day (PID) 7. Maximal IgG antibody activity occurred at PID 35 in nonpregnant heifers and at PID 14 in pregnant heifers. Thereafter, IgG antibody activity declined slowly in both groups of heifers. Maximal IgM antibody activity occurred at PID 14 in both groups of heifers and declined rapidly thereafter. The IgG antibody activity during primary immune responses was restricted to the IgG1 subclass. Secondary responses were characterized by anamnestic IgG antibody responses. Antibody activity was present within the IgG1 and IgG2 subclasses during secondary immune responses, but the increase in antibody activity during this period was primarily in the IgG2 subclass. Secondary IgM antibody formation was elicited by abortion induced by the intra-amniotic inoculation of BHV-1, but not by reexposure by the intranasal route. Abortion occurred in 1 heifer 28 days after intranasal BHV-1 inoculation. Abortion in this heifer was not associated with a secondary antibody response. The nature of BHV-1 antigenic exposure in the bovine determined the relative distribution of anti-BHV-1 antibody activity in serum IgM, IgG1, and IgG2. The formation of IgM antibody, with the exception of secondary intranasal exposure, indicated recent BHV-1 antigenic exposure.(ABSTRACT TRUNCATED AT 250 WORDS)