Amino acid variations of the immuno-dominant domain of respiratory syncytial virus attachment glycoprotein (G) affect the antibody responses In BALB/c mice.

Respiratory syncytial virus (RSV) is the leading cause of respiratory illness in ruminants and infants. The G glycoprotein of RSV serves as the viral attachment ligand. Despite currently available vaccines, RSV immunity is insufficient, and re-infections occur. Vaccine studies employing the G-protein's 174-187 amino acids, representing the immunodominant domain, have protected mice and calves against infections. To investigate the causes of vaccination failure, we designed four synthetic peptides for the ruminant RSV isolates (391-2, Maryland-BRSV, European-BRSV, and ORSV) using the immune-dominant sequence and vaccinated mice groups with them. The produced antibodies targeting each peptide were evaluated using ELISA and flow cytometry to determine their reactivity against the linear antigen and the native form of the G protein, respectively. Antibodies responded to homologous and heterologous peptides as determined by ELISA. Using flow cytometry-analysis targeting the natively folded protein, most generated antibodies reacted only with their homologous strain. However, antibodies raised to 391-2 peptide reacted with homologous and heterologous Maryland-BRSV viral epitopes. Accordingly, inadequate immunity and recurring RSV infections might be attributed to variations of antibodies targeting the immunodominant region of the G-protein.