Characterization of Highly Pathogenic Avian Influenza H5N1 Viruses Isolated from Domestic Poultry in China

The highly pathogenic avian influenza （HPAI） H5N1 virus has caused several outbreaks in domestic poultry. Despite great efforts to control the spread of this virus, it continues to evolve and poses a substantial threat to public health because of a high mortality rate. In this study, we sequenced whole genomes of eight H5N1 avian influenza viruses isolated from domestic poultry in eastern China and compared them with those of typical influenza virus strains. Phylogenetic analyses showed that all eight genomes belonged to clade 2.3.2.1 and clade 7.2, the two main circulating clades in China. Viruses that clustered in clade 2.3.2.1 shared a high degree of homology with H5N1 isolates located in eastern Asian. Isolates that clustered in clade 7.2 were found to circulate throughout China, with an east-to-west density gradient. Pathogenicity studies in mice showed that these isolates replicate in the lungs, and clade 2.3.2.1 viruses exhibit a notably higher degree of virulence compared to clade 7.2 viruses. Our results contribute to the elucidation of the biological characterization and pathogenicity of HPAI H5N1 viruses.

International chicken trade and increased risk for introducing or reintroducing highly pathogenic avian influenza A (H5N1) to uninfected countries

Every year billions of chickens are shipped thousands of miles around the globe in order to meet the ever increasing demands for this cheap and nutritious protein source.Unfortunately,transporting chickens internationally can also increase the chance for introducing zoonotic viruses,such as highly pathogenic avian influenza A(H5N1)to new countries.Our study used a retrospective analysis of poultry trading data from 2003 through 2011 to assess the risk of H5N1 poultry infection in an importing country.We found that the risk of infection in an importing country increased by a factor of 1.3(95%CI:1.1e1.5)for every 10-fold increase in live chickens imported from countries experiencing at least one H5N1 poultry case during that year.These results suggest that the risk in a particular country can be significantly reduced if imports from countries experiencing an outbreak are decreased during the year of infection or if biosecurity measures such as screening,vaccination,and infection control practices are increased.These findings show that limiting trade of live chickens or increasing infection control practices during contagious periods may be an important step in reducing the spread of H5N1 and other emerging avian influenza viruses.

The interaction of influenza H5N1 viral hemagglutinin with sialic acid receptors leads to the activation of human γδT cells

Highly pathogenic avian influenza H5N 1 epidemics are a significant public health hazard. Genetically engineered H5N 1 viruses with mammalian transmission activity highlight the potential risk of a human influenza H5N 1 pandemic. Understanding the underlying principles of the innate immune system in response to influenza H5N 1 viruses will lead to improved prevention and control of these potentially deadly viruses, γδT cells act as the first line of defense against microbial infection and help initiate adaptive immune responses during the early stages of viral infection. In this study, we investigated the molecular mechanisms of γδ T cells in response to influenza H5N1 viral infection, We found that recombinant hemagglutinin （rHA） derived from three different strains of influenza H5N 1 viruses elicited the activation of γδ T cells cultured in peripheral blood mononuclear cells （PBMCs）. Both the cell surface expression of CD69, an early activation marker on γδ T cells, and the production of interferon-y （IFN-y） were significantly increased. Notably, the rHA protein-induced γδ T-cell activation was not mediated by TCRγδ, NKG2D or pattern recognition receptors （PRRs） or NKp46 receptors. The interaction of rHA proteins with sialic acid receptors may play a critical role in γδ T-cell activation. Our data may provide insight into the mechanisms underlyingγδT-cell activation in response to infection with H5N1 viruses.