Molecular Epidemiology Of Respiratory Syncytial Virus And Human Metapneumovirus In Children In Chongqing Area

PARTⅠ:epidemiology features of respiratory syncytial virus in children with acute respiratory tract infections in Chongqing areaObjective To investigate epidemiological features of respiratory syncytial virus (RSV) A and B in hospitalized children with acute respiratory tract infections (ARTIs) and to analyze the genetic characteristics of G protein gene of RSV in Chongqing area, especially for BA stians.Methods Nasopharyngeal secretions collected from 508 hospitalized children with ARTIs from April, 2008 to March,2009 were screened for RSV using RT-PCR. Full length G protein gene was amplified by RT-PCR from 10 RSV subtype A and 29 RSV subtype B strains.Results Out of the total 508 specimens ,126(24.8%) were revealed positive for RSV. RSV subtype A and B viruses accounted for 34.1% and 63.5% of the total positive specimens, respectively. The remaining 2.4% of the specimens were positive for both subtype A and B. At the nucleotide level, identities between the 10 subtype A virus G genes and that of the prototype strain A2 were 91.4%～92%, indicating genotype GA2. Identities of the 29 subtype B virus G genes and that of the CH18537 strain were 92.0%～93.0%. Nineteen out of 29 RSV subtype B isolates contained highly repeated 60 nucleotides insertion in G protein gene, namely BA strain. As compared to the prototypes, the RSV G protein gene included nucleotide deletion, insertion, substitutions, especially in the carboxy-terminal third of the G gene.Conclusion RSV has been the major cause of acute respiratory tract infections in children in Chongqing area. Subtype B strains, especially BA strains, were predominant during the study period. Whether the predominated circulation of BA strain is resulted from enhanced attachment function of G protein remains unknown.PARTⅡ:epidemiology features of human metapneumovirus in children with acute respiratory tract infections in Chongqing areaObjective To investigate epidemiological features of human metapneumovirus (hMPV) in hospitalized children with acute respiratory tract infections (ARTIs) and to analyze the genetic characteristics of G protein gene of hMPV in Chongqing area.Methods Nasopharyngeal secretions collected from 508 hospitalized children with ARTIs from April, 2008 to March,2009 were screened for hMPV using real-time reverse transcription-PCR. Full length G protein gene was amplified by RT-PCR from 12 strains hMPV.Results During the study period,out of the total 508 clinical specimens,60(11.8%) were revealed positive for hMPV.hMPV was detected almost in every month from April 2008 to March 2009 (except August and september,2008). A peak was noticed in April 2008 to July 2008, especially April 2008. Among 60 positive samples, 9 were also positive for other respiratory viruses,suggesting that these children were co-infected with hMPV and other respiratory viruses. The peak of hMPV prevalence did not overlap with that of RSV during this period. Fifty-six out of sixty positive (93.3%,56/60) specimens on hMPV were from children under 5 year olds, forty-six (76.6%,46/60) were younger than 2 years of age, and four (6.7%,4/60) were over 5 years of age. The clinical manifestations of hMPV and RSV infections had a similar symptoms. Phylogenetic tree analysis of nucleotide sequences revealed two different genotype and three subtypes circulating during the period. At the nucleotide level, identities between the 11 subtype A virus G gene and that of the prototype strain CAN97-83 were 82.6%～91.7%, and the amino acid identities were 69.5%～86.4%. The nucleotide identities between the one subtype B virus G gene and that of the CAN98-75 was 82.4% and the amino acid identities was 67.8%.Conclusion our findings suggested that hMPV had been one of the important agents causing acute respiratory infections in Chongqing area. Infants and young children under two years of age seemed to be more susceptible to hMPV. There were two different genotypes of hMPV in Chongqing area, and CAN97-83 was the dominant type in Chongqing area.