Molecular characterization of human respiratory syncytial virus subtype B: a novel genotype of subtype B circulating in China.

Human respiratory syncytial virus (HRSV) is major pathogen of lower respiratory tract infections in infants and young children worldwide. There have been many studies regarding HRSV subgroup A (HRSV-A) G protein genetic variability but little information about HRSV subtype B (HRSV-B) G protein genetic diversity and molecular evolution in China. Thus, a survey of the molecular epidemiology and evolution of the G protein in China is of high importance. In this study, the circulation and genetic diversity of HRSV in Chongqing, Southwestern China, from June 2009 to May 2013, were investigated. A total of 3,167 nasopharyngeal aspirates were obtained in this study, and it was found that HRSV-B predominated in the 2009-2010 and 2012-2013 epidemic seasons. This study identified the genetic variability of the glycoprotein G gene among 102 HRSV-B strains isolated by cell culture from Chongqing nasopharyngeal aspirates, and 68 Chinese HRSV-B sequences were deposited in GenBank. Genotyping and phylogenetic analysis revealed that the HRSV-B strains were clustered into three genotypes: BA (n = 111, 65.29%), GB3 (n = 5, 2.94%), and a new GB genotype (n = 54, 31.77%) named GB5. The GB5 strains varied from other genotypes in the central conserved region and N-glycosylation sites. The estimated evolutionary rate of Chinese HRSV-B was 2.01 × 10(-3) nucleotide substitutions/site/year, which is similar to the reports from Belgium and the Netherlands with 1.95 × 10(-3) and 2.78 × 10(-3) nucleotide substitutions/site/year, respectively. This study provides data on the circulating pattern and molecular characterization of HRSV-B genotypes in China during four consecutive years and may contribute to HRSV vaccine development.