Detection And Analysis Of Human Respiratory Syncytial Virus In Hospitalized Children With Acute Lower Respiratory Tract Infection In Fuzhou

Objective:The aim of this study is through investigating the epidemiological data of human respiratory syncytial virus(RSV)infection in hospitalized children with acute lower respiratory tract infection and analyzing nucleotide and Amino Acid variability of G protein and F protein in the predominant strains in Fuzhou area,to provide new information for the prevention and control of RSV infection and the development of anti-RSV drugs and related vaccinesMethods:We collected nasopharyngeal secretions samples from hospitalized children with acute lower respiratory tract infection in Fuzhou during the period of Jan.2016 to Dec.2017.The specimens were tested by direct immunofluorescent assay(DIFA)using D~3Ultra DFA Respiratory Virus Screening&ID Kit.During the period of Jun.2016 to May.2017,39 RSV positive specimens were randomly selected for RT-PCR,used for detection and identification of RSV subgroup followed by Sanger sequencing to display nucleotide sequences of G protein gene and F protein gene in B subtype strains.DNAMAN software was used to align the multiple sequences and calculate homology.MEGA7.0 software was employed to calculate genetic distance,construct phylogenetic tree and analyze variation of nucleotide and amino acids.Results:During the period of Jan.2016 to Dec.2017,a total of 577 samples were collected and 113 cases of RSV specimens were detected(19.6%).Among 113cases of RSV specimens,the age of the infected children was from 20 days to 6years,the median age was 8 months.Among them,there were 72 males and 41females,and the proportion of males:females was 1.8:1.There were 4 peaks of infection,eg from Jan.2016 to Mar.2016,July.2016 to Sep.2016,Jan.2017 to Mar.2017,and Sep.2017 to Nov.2017,with the highest positive rate(42.9%)in Oct.2017.During the period of Jun.2016 to May.2017,39 RSV positive samples were randomly selected for RT-PCR and virus isolation.2 RSV-A and 24 RSV-B were detected from 26 samples obtained by electrophoretic analysis.In RSV-B G protein gene C-terminal second highly variable region(HVR2)nucleotide(amino acid)homology was 88.2%-100%(81.5%-100%),and the total genetic distance between isolates was 0.033+0.004(0.050+0.008).There was a duplication of 60nucleotides in the C-terminal portion of G gene in the RSV-B strains,which were closely related to the BA11 genotype.RSV-B F protein nucleotide(amino acid)homology was 98.8%-100%(99.0%-100%),and the total genetic distance of nucleotide(amino acid)is 0.005+0.001(0.003+0.001).Some amino acid substitutions observed by comparing F protein with the standard strain(CH-18537).R202Q,I206M and Q209R were located at the antigenic site?,M115V was located at HLA-A*01,N124S was located in HLA-B 57.None of the antigenic site II of Palivizumab monoclonal antibody,antigen site IV and HLA-Cw*12 had an amino acid variation.Conclusion:From Jan.2016 to Dec.2017,the RSV positive rate of hospitalized children with acute lower respiratory infection in Fuzhou was 19.6%.The peak of RSV infection appeared twice every year.During the period of Jun.2016 to May.2017,RSV-B wasthe predominant subtype in Fuzhou,the genotype of which was closely related to BA11.Compared with the prototype strain,the variation of G protein is significant and there are some variations in the F protein antigenic site region.This study provides the epidemiological data of RSV in our region,and provides new and useful information for the prevention and control of RSV and the development of antiviral drugs and related vaccines.