Etiological and molecular characteristics of pandemic influenza A (H1N1) virus during 2009-2010 in Shandong Province / 病毒学报

ABSTRACT

To isolate and identify the influenza virus in Shandong Province in 2009-2010 and analyze the genetic characteristics of hemagglutinin and neuraminidase gene, further study the variation of gene. A total of 17 126 nasopharyngeal swabs from fever patients were collected and detected by real time quantitative RT-PCR method. The results showed 4004 samples were pandemic influenza A (H1N1) virus positive, with an overall positive rate as 23.38%. The positive samples were incubated and cultured in MDCK cells. The HA and NA genes of isolated pandemic influenza A(H1N1) virus were sequenced, the homology analysis of the HA and NA genes showed an average of 96.9%-99.3% and 99.1%-99.6% sequence identity, respectively, compared with WHO-recommended vaccine strain. The genetic evolution and amino acid substitutions were performed with Mega 4.0 Software. Twenty one amino acids were changed in HA protein, of which 11 were located in the antigenic site; Sixteen amino acids were changed in NA protein, which didn't lead to the changes of enzyme sites. Furthermore, one glycosylation site of HA protein and NA protein were changed respectively. No H275Y mutation in NA protein was found. The results showed that the HA and NA genes of the epidemic strains were highly homologous, some mutations in the HA and NA proteins were found, the antigenic site and glycosylation site of some strains were changed during the epidemic process. All the strains were sensitive to oseltamivir.