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.