Objective To characterize the molecular characteristics of hemagglutinin (HA) and neuraminidase (NA) of influenza B viruses isolated in Jiangsu province,2011.Methods Thirteen strains of influenza B virus in different areas and epidemic period in Jiangsu province,2011 were selected for whole-genome sequencing,and analysis of molecule epidemic characteristics for HA and NA was carried out by bioinformatics method.Results Of the 13 randomly selected influeuza B strains,10 strains were assorted to Victoria lineage strains with NA genes from Yamagata lineage,and 3 strains belong to Yamagata lineage.Compared nucleotide and amino acid sequences of HA and NA genes with their vaccine strains respectiuely,196/197 glycosylation site appeared on HA1 gene in Yamagata/Victoria isolates virus.Conclusion Both B/Victoria and B/Yamagata lineage viruses co-circulated in Jiangsu province,and reassortant virus of Victoria lineage were predominant virus.

BACKGROUNDPB1-F2 protein has been proven to increase the pathogenicity of influenza A virus (IAV) strains in primary infection and in secondary bacterial infection. It can also regulate the activity of viral polymerase. However, it was shown in another retrospective study that a portion of IAVs do not express full-length PB1-F2 protein during virus development; different kinds of stop codons cause exits in the open reading frames and form PB1-F2 gene products with the corresponding genotypes. Truncated PB1-F2 in human H3N2 IAVs has long been detected in North America but its evolution in China is still unclear.

METHODSInfluenza-like illnesses (ILIs) from the whole of Jiangsu Province were collected and inspected to determine the type and subtype of the viruses. A portion of isolates collected in the epidemic period were selected as samples for later whole-genome sequencing, and the exact sequences were determined and analyzed.

RESULTSH3N2 influenza virus was one of the epidemical strains which had been prevalent during 2009-2010, in Jiangsu. Five H3N2 isolates with truncated PB1-F2 protein (25aa) were detected in influenza samples from Nanjing and Xuzhou, while seven similar H3N2 isolates were also reported in Niigata, Japan.

CONCLUSIONThis emergence indicates the possibility that there has been transmission of the H3N2 virus between the two countries.

China ; epidemiology ; Humans ; Influenza A Virus, H3N2 Subtype ; genetics ; metabolism ; Influenza, Human ; virology ; Viral Proteins ; chemistry ; genetics ; metabolism