RESEARCH ON THE DIFFERENCE OF HA1 REGION BETWEEN ISOLATION STRAINS AND VACCINE STRAINS OF INFLUENZA VIRUSES SUBTYPE A1 IN JIANGXI PROVINCE FROM 2005 TO 2006

Objective To analyze the difference of HA1 region between isolation strains and vaccine strains of influenza viruses subtype A1 in Jiangxi province from 2005 to 2006,and investigate the mutation of influenza viruses in Jiangxi province and the protection effect of the vaccine strains recommended by WHO. Methods The specimens of nasopharyngeal swabs were collected from suspected cases of influenza in monitor hospitals and influenza epidemic areas. RNA of the influenza viruses subtype A1 isolated was extracted,followed by amplifying the HA1 genes by reverse transcription polymerase chain reaction(RT-PCR),and nucleotide sequencing was performed. The results of sequencing were analyzed with DNAStar5.0,BioEdit(Version5.0)and Mage software. Results Nucleotide sequence of HA1 region in 20 strains of influenza viruses subtype A1 were 960 bp,no deletion and insertion were found in the nucleotides. Accordingly,the average rate of point mutation was 2.94%.When compared with vaccine strains of northern hemisphere recommended by WHO(A/New caledonia/20/99(H1N1)),the influenza viruses subtype A1 strains isolated in 2005 showed 96.9% to 98.1% and 95.3% to 97.2% homology in amino acid. 6-10 amino acids changed and involved 2-3 antigenic determinant sites in which the variant amino acids was 2.33. When compared with HA1 region of vaccine strains recommended,the influenza viruses subtype A1 strains isolated in 2006 revealed 95.3% to 97.2%,9-15 amino acids changed and involved 4 antigenic determinant sites in which the variant amino acids was 6.0. This study had shown difference of amino acids in HA1 region and in antigenic determinant between the influenza viruses subtype A1 isolated in 2006 and vaccine strains recommended by WHO was significantly higher that difference between influenza viruses subtype A1 isolated in 2005 and vaccine strains recommended by WHO(P﹤0.000 5). Conclusion The vaccine produced according to the influenza A1 vaccine strains recommended by WHO in 2005 have shown effectively protective effect for the influenza viruses subtype A1 in Jiangxi province,while the vaccine produced according to the influenza A1 vaccine strains recommended by WHO in 2006 was present inadequate protective effect to the influenza viruses subtype A1.