Analysis of hemagglutinin gene characteristics of influenza A H3N2 virus in Changzhou, 2017 -2018 / 公共卫生与预防医学

ABSTRACT

Objective To understand the epidemiological characteristics and variation of H3N2 influenza virus hemagglutinin (HA) gene in Changzhou from 2017 to 2018. Methods Throat swab specimens of the influenza-like cases were collected from Changzhou Influenza Monitoring Sentinel Hospital from April 2017 to March 2018. RNA was extracted from the specimens for influenza diagnosing and genotyping using real-time RT-PCR．H3N2 positive samples were isolated, and extracted RNA was used for amplification, sequencing and phylogenetic analysis of HA gene. Results From April 2017 to March 2018, 28 strains of influenza A (H3N2) virus were isolated. After gene sequencing, a phylogenetic tree was constructed. It was found that all of the strains belonged to Group3C.2a, which was similar to the vaccine strain A/Hong Kong/4801/2014. The HA amino acid sequence difference was analyzed and compared between the H3N2 influenza virus strains isolated in Changzhou and the vaccine strain A/Hong Kong/4801/2014. It was found that the epidemic strain isolated in Changzhou was in the HA epitope (A-E) region. Ten amino acid site mutations in the HA epitope (A-E) region and two amino acid site mutations in the stem region of HA antigen were found. Conclusion From April 2017 to March 2018, the influenza virus H3N2 prevalent in Changzhou was distributed on the same evolutionary branch with the vaccine strain A/Hong Kong/4801/2014 (group 3C.2a), rendering the popular trend of one subgroup. However, some amino acid sites of the HA epitope had variations, suggesting that mutations may occur, which may affect the immune effect of the vaccine. Monitoring needs to be strengthened in the future work.