MOLECULAR EVOLUTION OF THE F-GLYCOPROTEIN OF HUMAN PARAINFLUENZA VIRUS TYPE-1

Human parainfluenza virus type 1 (hPIV1) is a major cause of upper and lower respiratory tract infections among children. Immunity is mediat ed at least in part by antibody to the fusion (F) surface glycoprotein . Thus, genetic variation in the F gene could influence host range, vi rulence, and immunity. To examine the genetic diversity among hPIV1 is olates, the F genes of hPIV1 isolates from a single geographic locatio n were sequenced and compared with the F gene of a strain isolated in 1957. Genetic variation was 2.2%-3.4%, averaging 0.8 amino acid change s per year. Changes were progressive over time, and virus evolution wa s dominated by a single lineage. Three of 7 isolates tested did not in duce syncytium formation in tissue culture. This phenotype could not b e ascribed to a single unique mutation in the F gene, but these 3 isol ates had mutations in the transmembrane region of the HN gene. It is u nlikely that the limited genetic evolution of the F gene will be an ob stacle to vaccine development.