Cross-reactive and group-specific immune responses to a neutralizing epitope of the human respiratory syncytial virus fusion protein.

Immune responses to a synthetic peptide corresponding to amino-acids 205-225 of the fusion protein from group B respiratory syncytial (RS) virus, were studied in mice and rabbits, and compared to a similar peptide from group A RS virus. Peptide 205-225 (B) was recognized by monoclonal antibody RS-348, and was immunogenic in both mice and rabbits, as was peptide 205-225 from the fusion protein of a group A strain. Peptide 205-225 (B) induced a proliferative T-cell response, demonstrating the existence of a T-cell epitope in this region of the fusion protein of group B viruses. Both peptides were able to induce a T-cell cross-reactive proliferation when mice were primed with either the homologous or the heterologous peptide. ELISA were performed using synthetic peptides or whole virus (from group A and B) as antigens. Mice anti-peptide sera recognized both homologous and heterologous peptides. A similar pattern was observed with RS virus strains. In indirect immunofluorescence assays, both anti-peptide rabbit sera recognized human nasal epithelial cells infected with A or B strains of RS virus. In contrast, while anti-peptide 205-225 rabbit serum from group A neutralized group A and B strains of RS virus, anti-peptide 205-225 rabbit serum from group B was unable to neutralize a group A virus, although it neutralized a group B strain. These results are similar to the immune response observed in children following primary RS virus infection.