摘要:
目的 了解2011—2018年青岛市人群B型流感病毒(IBV)流行株基因进化变异趋势.方法 2011—2018年间青岛市流感样病例标本12236份,提取病毒RNA,采用IAV/IBV多重荧光RT-PCR方法鉴定流感病毒及型别,使用B/Victoria系和B/Yamagata系分型核酸检测试剂盒检测IBV两个谱系;选取IBV 182株,RT-PCR扩增血凝素(HA)和神经氨酸酶(NA)基因,并进行序列测定,进行系统发育分析及氨基酸位点变异分析.结果 2011—2018年青岛市几乎每年都会检出IBV,阳性率(4.99%)仅比IAV(6.21%)略低.B/Victoria和B/Yamagata分别出现了2个(2011—2012年,2015—2016年)和3个显著流行年份(2013—2014年,2014—2015年,2017—2018年).感染人群以10岁以下儿童为主,两系具有相似的年龄特征.基于HA进化,B/Victoria系分离株分属于Vic-1A和Vic-1B,B/Yamagata系分离株分属于Yam-2和Yam-3.B/Yamagata在HA上的氨基酸变异位点多于B/Victoria,表现出更大的遗传多样性.B/Yamagata系在抗原决定簇上已发生了12个氨基酸位点变异,在受体结合位点上发生了2个氨基酸位点变异;B/Victoria系则分别已发生7个和3个氨基酸位点变异.青岛市IBV基因重配频繁,系内重配26株,多发生在B/Victoria系内;系间重配23株,多发生在HA-B/Yamagata与NA-B/Victoria之间.发现了1株可能的NA抑制剂耐药株.结论 IBV在季节性流感中的地位不容忽视.氨基酸替换、插入-缺失和基因片段重配是IBV自然进化的主要策略.流感监测十分重要,流感疫苗株需要及时更新.%Objective To investigate the molecular epidemiological characteristics of hemaggluti-nin (HA) and neuraminidase (NA) of influenza B viruses (IBV) isolated in Qingdao from 2011 to 2018. Methods A total of 12236 samples of influenza-like cases in Qingdao from 2011 to 2018 were collected to extract viral RNAs. All samples were screened for influenza A viruses ( IAV) and IBV by one-step multiplex real-time RT-PCR. Lineages of IBV were identified. One hundred and eighty-two strains of IBV were select-ed to amplify HA and NA genes by RT-PCR and then analyzed by sequencing. Phylogenetic analysis and variation analysis of genes and amino acids were carried out. Results IBV was detected almost every year in Qingdao from 2011 to 2018. The positive rate was only slightly lower than that of IAV ( 4. 99% vs 6. 21%). B/Victoria linkage had two prominent epidemic years (2011-2012, 2015-2016), while B/Yama-gata linkage had three (2013-2014, 2014-2015, 2017-2018). Most of the infected people were children un-der 10 years old, and the people infected with the two lineages had similar age characteristics. Phylogenetic analysis of HA genes showed clusters in Victoria clades of 1A and 1B and Yamagata clades of 2 and 3. IBV of Yamagata lineage had more amino acid mutation sites than those of Victoria lineage in HA genes with grea-ter genetic diversity. The B/Yamagata strains had 12 amino acid mutations and the B/Victoria strains had seven in four major epitopes. In the receptor binding sites, two amino acid mutations were detected in the B/Yamagata strains and three in the B/Victoria strains. In Qingdao, 26 strains of IBV were intra-lineage reas-sortments, mostly of the B/Victoria lineage, and 23 strains were inter-lineage reassortments, mostly between HA-B/Yamagata and NA-B/Victoria strains. A possible resistant strain to NA inhibitor was found. Conclu-sions The significance of IBV in seasonal influenza should not be neglected. Amino acid substitution, in-sertion/deletion and gene reassortment were the main strategies for the natural evolution of IBV. Influenza surveillance was of great importance and influenza vaccine strains needed to be updated in time.