Objective: To analyze the changes in the phylogenetic and antigenic characteristics of the hemagglutinin (HA) gene of influenza virus A(H3N2) [A(H3N2)] during the 2022-2024 influenza seasons in Beijing. Methods: The data of influenza-like cases and A(H3N2) strains from 17 network laboratories and their corresponding sentinel hospitals were collected during the 2022-2024 influenza seasons. The HA genes were amplified and sequenced after extracting nucleic acids of the chosen virus strains. BioEdit, the nucleotide and amino acid sequence identity were conducted, and the maximum likelihood method in MEGA 5.0 software was used to construct the phylogenetic tree of HA genes. Web Logo displayed the amino acid mutation, and the N-glycosylation sites of HA online were analyzed using the NetNGlyc1.0 Server online. The Datamonkey platform was utilized to analyze the positive selection pressure sites of the HA protein. Results: The 2022-2024 influenza season includes 2022-2023 and 2023-2024. During the influenza seasons of 2022-2024, the positive rates of A(H3N2) nucleic acid were 10.35% (2 127/20 543) and 10.47% (4 386/41 876), respectively. In the 2022-2023 influenza season, there were two peaks in the A(H3N2). The comparison of HA genes between all A(H3N2) strains studied with the 2022-2024 vaccine strain (A/Darwin/9/2021) revealed that all of the strains studied have the two amino acid mutations involving 186 and 225 receptor binding sites. There were 31 amino acid substitutions in the 2022-2023 influenza season, of which 18 variant sites involved antigenic determinants. There were 35 amino acid mutations during the 2023-2024 influenza season, of which 14 were related to antigenic determinants. There were changes in the genetic evolutionary subclades of A(H3N2) strains in two influenza seasons: from 2022 to 2023, three evolutionary subclades were co-prevalent together, with the 3C.2a1b.2a.2a.3a.1 accounting for 76.67% (23/30), the 3C.2a1b.2a.1a accounting for 20.00% (6/30), the 3C.2a1b.2a.2a.1 accounting for 3.33% (1/30); from 2023 to 2024, two subclades were prevalent, with 3C.2a1b.2a.2a.3a.1 accounting for 95.12% (39/41) and 3C.2a1b.2a.2a.1 accounting for 4.88% (2/41). The glycosylation site changes of the HA protein of A(H3N2) have been enhanced from 2023 to 2024. The 145 amino acid position of the HA protein of the A(H3N2) was the positive selection site for stress selection site analysis. Conclusions: The evolutionary subclades of the HA gene of A(H3N2) in Beijing showed changes from 2022 to 2024, and the glycosylation site polymorphism of the HA protein of A(H3N2) significantly increased from 2023 to 2024. Continuous monitoring of HA mutations in the A(H3N2) is crucial, providing a basis for developing influenza prevention and control strategies, as well as new strategic support for screening influenza vaccine components, vaccine design, and discovery of drug targets.
目的： 分析2022-2024流感季北京市A（H3N2）亚型流感病毒［A（H3N2）］血凝素（HA）基因特征的变化。 方法： 收集2022-2024流感季哨点医院流感样病例及网络实验室的A（H3N2）毒株数据，提取病毒核酸后PCR扩增HA基因、测序。应用BioEdit软件进行病毒HA基因的核苷酸和氨基酸变异分析，应用MEGA 5.0软件中的最大似然法构建HA基因的遗传进化树，在线应用Web Logo展示氨基酸变异结果，应用NetNGlyc1.0 Server平台在线分析HA的N-糖基化位点，应用Datamonkey平台在线分析HA的正向选择压力位点。 结果： 2022-2024流感季包含2022-2023和2023-2024共2个流感季，A（H3N2）流感阳性率分别为10.35%（2 127/20 543）和10.47%（4 386/41 876）；2022-2023流感季，A（H3N2）出现2个流行峰。与2022-2024流感季北半球流感疫苗A（H3N2）亚型组分株A/Darwin/9/2021HA基因相比较，2个流感季A（H3N2）毒株均有受体结合位点上186、225位氨基酸变异，其中2022-2023流感季有31个氨基酸位点变异，其中18个变异位点涉及抗原决定簇；2023-2024流感季有35个氨基酸位点变异，其中14个变异位点涉及抗原决定簇。2个流感季A（H3N2）毒株遗传进化分支出现变化，其中2022-2023流感季3个进化分支毒株共同流行，其中3C.2a1b.2a.2a.3a.1分支占76.67%（23/30），3C.2a1b.2a.1a分支占20.00%（6/30），3C.2a1b.2a.2a.1分支占3.33%（1/30）；2023-2024流感季2个进化分支毒株共同流行，其中3C.2a1b.2a.2a.3a.1分支占95.12%（39/41），3C.2a1b.2a.2a.1分支占4.88%（2/41）。2023-2024流感季A（H3N2）的HA蛋白糖基化位点变化增强；选择压力分析A（H3N2）的HA蛋白第145位氨基酸为正向选择位点。 结论： 北京市2022-2024流感季A（H3N2）的HA基因进化分支出现变化，其中2023-2024流感季A（H3N2）的HA蛋白糖基化位点多态性明显增强。持续监测A（H3N2）的HA变异至关重要，为流感防控策略的制定提供依据及流感疫苗组分株筛选，疫苗的设计、药物靶点的发现提供新的策略支持。.