珠海市2011年连续发生5起乙型流感疫情的病毒HA1基因分析

Analysis on HA1 Gene of Influenza B Virus Isolated from 5 Consecutive Influenza Outbreaks in Zhuhai in 2011

目的分析珠海市2011年多起连续发生的流感疫情中分离的乙型流感毒株HA1基因特性,阐述流感暴发的原因。方法用MDCK细胞分离培养流感病毒,提取病毒核酸,采用RT-PCR扩增病毒HA基因并测定核苷酸序列,用ClustalX和MEGA4.1分析结果。结果珠海市2011年多起连续发生的流感疫情中分离的乙型流感病毒属Victoria系,与2011年流感监测分离株2011C-IN-0056-7相比,没有核苷酸的丢失和插入,没有糖基化位点的改变,核苷酸同源性在97.3%以上,氨基酸有1~3个位点发生了变异,属于同一变异株。与2010-2011年北半球乙型流感疫苗株B/Brisbane/60/2008相比较,核苷酸同源性在98.5%以上,氨基酸有1~4个位点发生变异,也属于同一变异株。结论引起本市流感连续暴发疫情的原因可能是本地流行株抗原漂移所致,与疫苗株B/Brisbane/60/2008核苷酸和氨基酸同源性都很高,吻合性较好,如果能够在儿童中普遍接种,应该能够起到很好的预防作用。

Objective To analyze the characteristics of the HA1 gene of the influenza B virus isolated from the 5 concesu- tive influenza outbreaks in Zhuhai in December 2011 and to explore the reason of the outbreaks. Methods The influenza virus was isolated from the specimens and cultured in MI^K cells. RNAs were extracted and HA gene was amplified by reverse tran- scription polymerase chain reaction （RT- PCR）. The PCR products were sequenced. The results were analyzed by the software ClustalX and MEGA4.1. Results The influenza B virus isolated from the influenza outbreaks in Zhuhai in December 2011 was Victoria- like strain. When it was compared with the HA1 gene of the strain obtained from the influenza surveillance in 2011, 2011C- IN- 0056- 7, it was found that no deletion or insertion occurred to the nucleotide acids, and the glycosylation site was not changed. The homology of the nucleotide acids was above 97.3 %. Mutation of amino acids occurred in 1 - 3 sites, and they belonged to the same variant. When it was compared with B/Brisbane/60/2008, the vaccine strain in the northern hemi- sphere in 2010 - 2011 recommended by WHO, the homology of the nucleotide acids was above 98.5 %, and there were mutationsof amino acids in 1 - 4 sites. They also belonged to the same variant. Conclusions The 5 eonsecutive influenza outbreaks in Zhuhai in December 2011 are attributed to antigenic drift in HA1 region. The nucleotide acids and amino acids of the influenza virus isolated from the outbreaks have high homology with those of the vaccine strain recommended by WHO, B[Brisbane]60/ 2008. The protective effect of the vaccine is promising if it is vaccinated in children extensively.