ISOTYPE-SPECIFIC ANTIBODY-RESPONSES TO BOVINE HERPESVIRUS-1 IN SERA AND MUCOSAL SECRETIONS OF CALVES AFTER EXPERIMENTAL REINFECTION AND AFTER REACTIVATION

Isotype-specific antibody responses to bovine herpesvirus 1 (BHV1) wer e measured in sera, nasal, ocular and genital secretions of calves tha t were reinfected with BHV1 and 6 weeks later treated with corticoster oids to reactivate putative latent virus. After reinfection and after reactivation, no BHV1-specific IgM antibody response was detected. The serum IgA response was only transiently detectable after reinfection and again appeared rapidly after reactivation in most calves. Most cal ves showed an increase in nasal and ocular IgA titres after reinfectio n and reactivation; some calves also had IgA antibodies in genital sec retions. A salient finding was that after reinfection and reactivation more calves showed a serum IgA response than virus shedding or an inc rease in serum IgG1 or IgG2 titres. This suggests that the serum IgA r esponse would be the most sensitive indicator to detect BHV1 reinfecti on and reactivation. No correlation was found between nasal IgA titre at the time of reinfection or corticosteroid treatment and the period of virus shedding, suggesting that nasal IgA does not play a major rol e in protection against reinfection with BHV1.