Evolutionary pattern of the G glycoprotein of human respiratory syncytial viruses from antigenic group B: the use of alternative termination codons and lineage diversification

Partial sequences of the G protein gene of 33 isolates from antigenic group B of human respiratory syncytial virus were determined. Phylogenetic analy sis indicated that the evolutionary pattern of group B viruses is similar t o that previously described for isolates of antigenic group A, including wo rldwide distribution of related viruses and co-circulation of viruses from different lineages during the same epidemic. Dominance of AG+GA over UC+CU transitions was observed when G sequences of group B viruses were compared, as previously found in viruses from antigenic group A. Interestingly, diff erences in protein length, determined by the usage of alternative terminati on codons, were more pronounced in group B than in group A viruses. Changes in protein length correlated with the classification of viruses in differe nt lineages. Thus, mutations that determined termination codon usage seem t o have played an important role in the diversification of group B viruses.