Genetic variability of the fusion protein and circulation patterns of genotypes of the respiratory syncytial virus

Although antigenic and genetic variations were shown to occur both in the G and F protein of respiratory syncytial virus (RSV), few studies looked at the variation of F gene. The F genotypes were determined by the evaluation of clustering patterns, via the phylogenetic analysis of the nucleotide sequences of a variable region in the F gene. One hundred seventy-nine strains obtained from a children's hospital in Korea over nine consecutive epidemics were included. The relationship between the F and G genotypes was analyzed with the G genotypes previously published by the authors. The phylogenetic analysis of the variable region from the F gene revealed 9 genotypes among 129 group A RSVs and 4 genotypes among 50 group B RSVs. In each of the epidemics, the dominant genotypes were replaced with new genotypes in consecutive epidemics. In each of the epidemics of group B RSVs, the predominant genotype alternated between genotypes. Most of the strains which clustered to a particular F genotype were assigned to particular G genotype(s). By determining the nearly entire sequences of the F genes, we revealed the percentage of the nucleotide differences which resulted in amino acid coding changes was determined to be much great in two distinct variable regions of the F gene. Our results indicated that the F gene of the RSVs may be continuously evolving under selective pressure in a distinct pattern, and that the genetic variability of the F protein is associated with that of the G protein.