重庆地区急性呼吸道感染患儿呼吸道合胞病毒流行特征及其G基因序列分析

Molecular epidemiology of respiratory syncytial virus in children with acute respiratory tract infections and sequence analysis of G gene in Chongqing area

目的分析重庆地区2008--2009年度急性呼吸道感染住院患儿呼吸道合胞病毒（respiratorysyncytialvirus，RSV）的亚型流行情况，并了解优势流行株BA株的G蛋白基因特征。方法采集2008年4月-2009年3月全年于重庆医科大学附属儿童医院因急性呼吸道感染住院的508例患儿鼻咽深部分泌物，用RT-PCR方法检测RSV并进行亚型鉴定，选取29例B亚型和10例A亚型RSV阳性标本，用RT-PCR的方法扩增全长G蛋白并测序。结果在508例标本中，RSV阳性126例（24．8％），其中检测出A亚型43例（34．1％），B亚型80例（63．5％），A、B亚型混合感染3例（2．4％）。所测的10株A亚型的G基因与标准株A2的核苷酸同源性为91．4％-92．0％，均属GA2基因型；29株B亚型的G基因与标准株CH18537的核苷酸同源性为92．0％～93．0％，其中19株均为具有60个高度重复核苷酸插入的BA株。B亚型流行株与CH18537标准株相比，G基因有多种核苷酸变异如缺失、插入等，尤其在G蛋白近c端1／3处的高变区。结论2008--2009年RSV仍是重庆地区儿童急性呼吸道感染的主要病原，与既往两年A亚型优势流行不同，2008--2009年度B亚型毒株流行占优；近年新发现的BA株可能已成为本地区优势流行株，BA株G基因变异是否导致G蛋白功能增强，进而促进其优势流行尚有待研究。

Objective To investigate the 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 strains. 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% -92.0%, 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.