ANTIBODY-RESPONSES AGAINST THE G-PROTEINS AND F-PROTEINS OF BOVINE RESPIRATORY SYNCYTIAL VIRUS AFTER EXPERIMENTAL AND NATURAL INFECTIONS

Antibodies against the two major surface glycoproteins of bovine respi ratory syncytial virus (BRSV), G and F, play a role in protection agai nst BRSV-associated disease, but only the antibody response against th e F protein has been well described, Therefore, me used a novel peptid e-based enzyme-linked immunosorbent assay (G peptide-ELISA) to compare immunoglobulin G (IgG) and IgG subclass antibody responses against th e G protein with the antibody response against the F protein, as measu red by a conventional BRSV ELISA (F-ELISA). Experimental infection of cattle induced significantly lower antibody titers than did natural in fection, After natural primary infection, G peptide-specific antibodie s declined more rapidly and to lower levels than the F protein-specifi c antibodies, As a consequence, the G peptide-ELISA detected more rein fections than did the F-ELISA. Ratios of G- and F-specific IgG1/IgG2 a ntibody titers did not differ markedly after infection or vaccination. Interestingly, after natural infection calves did not develop an IgG2 response to the complete G protein, Pn contrast, adult cattle had hig h IgG2 titers against this protein. Vaccination with a live vaccine in duced low antibody titers, similar to the titers after experimental in fection, whereas vaccination with an inactivated vaccine induced high titers, The results indicate that the kinetics of the G- and F-specifi c antibody responses differ, Furthermore, the IgG subclass response ag ainst the unglycosylated central region of the G protein is similar to the IgG subclass response to the F protein, but the IgG subclass resp onse differs from the response to the complete G protein.