Protection of BALE/c mice from respiratory syncytial virus infection by immunization with a synthetic peptide derived from the G glycoprotein

A synthetic peptide homologous to amino acids 174-187 of the G glycoprotein of the A2 strain of human respiratory syncytial (RS) virus (G/174-187) was shown to induce protection from live virus challenge of BALB/c mice after immunization with three doses of 50 micrograms of peptide coupled to keyhole limpet hemocyanin. Immunized mice showed high levels of circulating RS-specific antibodies as detected by ELISA assay; however, no neutralizing antibodies were found. Moreover, an important short-term cytotoxic T-cell response was observed with lymphocytes isolated from the lungs but not from the spleen of immunized mice. This response was lost 24 weeks after immunization; however, mice remained protected against challenge with live RS virus. In addition, a monoclonal antibody that specifically binds to peptide G/174-187 was found efficient in conferring passive protection from challenge: this data further supports our results on the importance of the 174-187 region in protection. Another peptide, spanning amino acids 144 to 159, was shown to induce neutralizing antibodies but did not confer protection.