Antibody responses of children to the C‐terminal peptide of the SH protein of respiratory syncytial virus and the immunological characterization of this protein

The SH protein of RSV, a small integrated hydrophobic membrane protein, consists of 64 amino acid residues in the polypeptide of subgroup A and 65 amino acid residues in the polypeptide of subgroup B. We synthesized five peptides, representing the SH protein of each RSV subgroup comprised of the following amino acid residues: 2–16, 12–26, 35–49, 45–60, and for subgroup A, 51–64 and for subgroup B, 51–65. Peptides 2–16 and 51–64/65 represented the N‐terminal and C‐terminal ends of the protein, respectively. In RIPA, under reducing conditions with mercaptoethanol, hyperimmune guinea pig (GP) serum against C‐terminal peptide of the two subgroups precipitated the homologous 7.5 kDa and 21–30 kDa SH proteins. Under nonreducing conditions, the GP antipeptide sera precipitated all three SH proteins, suggesting that the 13–15 kDa protein exists as a dimer. The subgroup A 7.5 and 13–15 kDa proteins had apparent molecular weights about 1–2 kDa higher than the corresponding subgroup B proteins. The C‐terminal peptides of subgroups A and B were used to characterize the immune response of 11 children, age 1 month to 1 year, with presumed primary RSV infection. Three of 4 children with subgroup A infection and 4 of 7 children with subgroup B infection developed homologous 4‐fold rises in antibody to C‐terminal peptide (aa 51–64/65) during convalescence. Except for one child with subgroup A and one child with subgroup B infection, the other 5 children developed heterologous rises also. The antibody levels to C‐terminal peptide were low suggesting that the SH protein was a weak stimulus of antibody in children with naturally acquired infection. Thus, it appears that the C‐terminal peptides of the SH protein are not useful as ELISA antigens in characterizing the subgroup‐specific immune responses to RSV infection.