GENETIC-HETEROGENEITY OF THE ATTACHMENT GLYCOPROTEIN-G AMONG GROUP-A RESPIRATORY SYNCYTIAL VIRUSES

Fifteen independent group A respiratory syncytial virus (RSV) isolates were compared by sequencing a 300-nucleotide interval encoding a vari able region of the attachment glycoprotein G. The viruses compared inc luded the reference strains Long (USA 1956), A2 (Australia 1961), and 669 (Sweden 1959), along with 13 clinical isolates obtained at differe nt times and locations throughout the United States. Representatives o f all six antigenic subgroups, recognized by reactivity patterns with monoclonal antibodies, were compared. The maximum sequence heterogenei ty within the G glycoprotein region compared was 15.7% of nucleotide s equences and 26% of amino acid sequences, more than twice the differen ce observed between Long and A2. Half of the nucleotide changes encode d amino acid substitutions, possibly indicating that the protein inter val compared was subject to immune selection. Because the ratio of nuc leotide to amino acid substitutions was nearly constant for all degree s of genetic divergence, the potential range of sequence divergence am ong group A RSV has probably not yet been attained. There was little c orrelation between the patterns of reactivity against a panel of monoc lonal antibodies and sequence relationships among the 15 isolates. The sequence information showed multiple genotypes circulating simultaneo usly in the same community and very similar genotypes circulating in w idely separated communities and during different years. Genetic analys es of RSV strains can provide important information about the relation ships between RSV infections.