Genetic Characteristics Of Human Respiratory Syncytial Virus Circulating In China Febrile Respiratory Syndrome

Human respiratory syncytial virus(HRSV)is one of the leading causes of acute respiratory tract infection in young children(?5 years old).Currently,no safe vaccine available or effective treatment measure was used in the world,except Palivizumab has been used for prevention among the premature infants and other high-risk infants in America and Europe.Attachment(G)protein and Fusion(F)protein are the most important antigens;many studies on the vaccine and antibody were based on these two glycoproteins.However,some basic knowledge about virology of HRSV circulating in China was not clear,which limits the development of Chinese proprietary vaccine and antibody.In this study,we investigated molecular epidemiology,genotypes distributions,genotype replacement and the molecular evolution of Chinese HRSV,and further analyzed the genetic characteristics and natural polymorphisms of F and G protein.This study will provide the basic scientific data and foundation for the development of vaccine and antibody,and the control and prevention of HRSV infection.Through the laboratory identification of HRSV from the Nasopharyngeal/throat swabs collected from Dongbei,Huabei,Xibei,Huazhong,Huanan regions of China during 2008 and 2015,the genetic characteristic of HRSV and the clinical manifestations of HRSV infectious cases were analyzed systematically.The results were as follows:1?In this study,705 out of 4246(16.60%)samples collected between 2008 and 2015 in China were tested positive for HRSV using double-channel real-time RT-PCR.Both subgroup A and B were identified in different regions of China.Alternate circulation style was found between subgroups.HRSVB was the predominant subgroup from 2008 to 2010,while HRSVA was prevalent from 2010 to 2013.However,both HRSVA and HRSVB co-circulated in China from 2013 to 2014,whereas HRSVA subsequently became the predominant subgroup in 2015.We found that HRSVA and HRSVB occasionally co-circulated in the same HRSV season,but more often,one predominant subgroup was observed in each season and subgroup A and B circulated alternately every 2-3 years.Six genotypes(GA2,GA5,NA1,NA3,NA4 and ON1 genotypes)of Chinese HRSVA were identified and there were genotype replacement during the epidemic of HRSV A viruses,e.g.:NA1 genotype was found to be replaced by the new genotype ON1 after 2013.Nine genotypes were detected among HRSVB:GB(GB2,GB3),SAB4,CB1 and BA(BA9,BA10,A7,BAc and BA)genotypes.BA9 genotype was the most predominant genotypes in China.2.Phylogenetic analysis comparison of G gene and the second hypervariable region of G gene showed the high consistence of the genotype identification.Amino acid analysis showed that the mutations mostly occurred in the second hypervariable region of HRSV G protein.Different mutation types were found:insertion,deletion,glycosylation site changes,etc.Both Chinese HRSVA and HRSVB showed high identity in the neutralization sites and CX3C motif region(binding with CX3C receptor and mediating immune response).3?Sequence analysis showed that the F protein sequences from China and other countries were highly conserved.The homology of Chinese F protein was over 99.00%and the homology of world F protein was>98.00%.Sequence of all Chinese samples was 100%conserved at the binding site of the neutralizing antibody palivizumab,predicting the susceptibility of these endemic Chinese HRSV strains to the neutralization by palivizumab.4?Evolutionary analysis showed that the evolutionary rates of the second hypervariable region was high.The evolutionary rates of ON1 and BA9 genotypes nucleotide sequences were 1.80(1.46,2.66)× 10-3 and 4.38(2.81,6.12)× 10-3 substitution/site/year,respectively.Lower evolutionary rate was found in F gene.The evolutionary rates of the whole F gene was 0.53-0.70×10-3 substitution/site/year.The BSP analyses showed that HRSV F gene was highly conserved.In summary,the genetic characteristics of Chinese HRSV circulating in all 7 representative regions of China from 2008 to 2015 were' analyzed systematically.The circulation of HRSV and the temporal and geographical distributions of HRSV subgroups/genotypes were analyzed comprehensively.The understanding of the genetic characteristics of Chinese G gene,the conservatism of HRSV F gene,and the trend of genetic evolution was analyzed.The endemic HRSV isolates and sequences databases were gathered and established,which would provide the scientific research foundation for the HRSV diagnosis methods,the screening of the vaccine candidate,antibody and other therapies for HRSV infection.