2013—2014年南京市流感病原监测系统分离到31株流感病毒H3N2亚型毒株，通过提取病毒RNA，反转录-聚合酶链反应(reverse transcriptase-polymerase chain reaction，RT-PCR)扩增血凝素(hemagglutinin，HA)基因片段，进行PCR产物纯化、测序并分析其遗传进化特征。结果显示，31株分离株与疫苗株A/Texas/50/2012之间的核苷酸和氨基酸进化距离分别为0.010 2和0.012 1，核苷酸和氨基酸的同源性分别为97.9%～99.6%和97.2%～99.3%。遗传进化分析表明，分离株的HA基因分属不同的进化分支，3株2013年分离株属3B基因型，3株2014年分离株属3C.1基因型，2株2014年分离株属3C.2b基因型，其余23株属3C.3a基因型。与疫苗株相比，分离株的分子特征表现为发生N128A/T和P198S/A(去信号肽排列)氨基酸位点变异，均位于抗原决定簇B；分离株抗原决定簇上发生变异的位点共计24个；7株分离株出现126 NWT糖基化位点，3株分离株糖基化位点45NSS和144NNS消失。结果提示， 2013—2014年南京市流感病毒H3N2亚型的HA基因较疫苗株发生了较大变异，疫苗对病毒的预防效果需重新评估。

A total of 31 representative strains of influenza A virus H3N2 subtype isolated at different time and regions in Nanjing between 2013 and 2014 through influenza pathogen monitoring system were selected for this study. The genetic distance between the vaccine strain A/Texas/50/2012 and the isolated group at nucleotide and amino acid levels were 0.010 2 and 0.012 1, respectively. The similarities of nucleotide and amino acid sequence were 97.9%-99.6% and 97.2%-99.3%, respectively. The phylogenetic analysis showed that hemagglutinin (HA) gene of 31 isolates could be divided into several groups. Three 2013 strains belonged to 3B, three 2014 strains belonged to 3C.1, two 2014 strains belonged to 3C.2b and the other 23 strains belonged to 3C.3a. Compared with the vaccine strain, the accumulated mutations on epitopes reached 24. The amino acid substitutions of N128A/T and P198S/A on HA in 31 isolates were observed. A new glycosylation site 126 NWT occurred in 7 isolates, and 45NSS and 144NNS glycosylation sites disappeared in 3 isolates. The results suggest that HA gene of H3N2 has a significant variation compared to the vaccine strain, and this may be related to the vaccine prevention program in Jiangsu Province during 2013-2014.