[Study on molecular epidemiological characteristics of influenza H1N1 viruses circulating in Shenzhen, China from 2005 to 2007].

ABSTRACT

OBJECTIVE: To study the genetic and epidemiological characteristics of HA1 of influenza H1N1 viruses circulating in Shenzhen from 2005 to 2007. METHODS: The HA1 region was analyzed by RT-PCR and subsequently sequenced to analyze the HA1 genetic evolution. Phylogenetic analysis was confirmed on the homology of nucleotide comparing with the reference viruses of vaccines recommended by WHO and representative virus confirmed by China CDC. Relationship between isolation rates and genetic evolutions was explored. RESULTS: The average isolation rate from 2005 to 2007 was 7.16%. Of the isolates, the proportions of influenza H1N1 viruses in 2005, 2006 and 2007 were 56.14%, 66.03%, 3.61%, respectively. Data from HA1 phylogenetic analysis showed that there were at least three clades circulated in Shenzhen. Different viruses isolated during January to April were clustered with A/New Caledonia/20/1999 viruses isolated in the latter months of 2005 clustered with A/Solomon Island/3/2006 and viruses from 2006 to 2007 were in the same clade with A/GDLH/219/2006. Results showed that most viruses had a deletion of lysine at position 130. Compared with A/New Caledonia/20/1999, the virus isolated after May of 2005 occurred T82K, Y94H, R146K, R209K, T267N amino acid substitution, while some virus isolated after May 2006 took place the amino acid substitutions of A190T, H193Y, E195D (located at antigenic site B) and R146K (antigenic site A). The sequences at the receptor-binding sites and glycosylation sites were conserved. Compared with referring viruses, A/SZ/68/2007 had 50 amino acid substitutions in the HA1 region. Of these, eleven and six were located at antigenic sites and receptor-binding sites, respectively. Four amino acid substitution resulted in the deletion of glycosylation site. CONCLUSION: Three different genetic lineages of influenza H1N1 virus were circulated in the population in Shenzhen during 2005 - 2007. The special virus named A/SZ/68/2007 should be paid further attention on its antigenic and epidemiological characteristics.