Comparative analysis of selected innate immune-related genes following infection of immortal DF-1 cells with highly pathogenic (H5N1) and low pathogenic (H9N2) avian influenza viruses.

H5N1 and H9N2 viruses are important causes of avian influenza in China. H5N1 is typically associated with severe to fatal disease in poultry, while H9N2 is usually associated with mild disease. Differences in viral virulence prompted us to investigate whether innate immune responses would be differentially regulated following infection by H5N1 and H9N2 viruses. To address this hypothesis, expression of a panel of innate immune-related genes including IFN-α, IFN-ß, Mx1, OASL, ISG12, IFIT5, IRF7, USP18, SST, and KHSRP in immortal DF-1 cells following H5N1 and H9N2 infection was analyzed and compared by real-time quantitative RT-PCR. Cells infected by either virus overall exhibited a similar expression profile for four ISGs (Mx1, OASL, ISG12, and IFIT5), IFN-α, IFN-ß, and SST gene. However, two immune-regulatory genes (IRF7 and KHSRP) were not responsive to highly pathogenic H5N1 infection but were strongly up-regulated in DF-1 cells infected with low pathogenic H9N2 infection. The subtype-dependent host response observed in this study offers new insights into the potential roles of IRF7 and KHSRP in control and modulation of the replication and virulence of different subtypes or strains of avian influenza A virus.

Isolation and genetic characterization of avian influenza virus H4N6 from ducks in China.

An avian influenza virus (AIV) strain belonging to the H4 subtype and provisionally designated as A/duck/China/J1/2012(H4N6) was isolated from diseased ducks with respiratory disease at a commercial poultry farm in Shandong, China, in 2012. The genomic coding sequences of all eight segments of this J1 isolate were determined and used for subsequent analysis. Phylogenetic analysis of all eight segments showed that this duck H4N6 virus was of Eurasian lineage and not American lineage. The results show that the virus probably emerged because of a reassortment event involving other avian H4N6 and H6N1 viruses. Interestingly, this H4N6 virus had all the conserved features common to low-pathogenic AIVs, including the HA cleavage sequence, receptor-binding sequences for the 2,3-linked sialic acid receptor in avian species, and the PB2 627E motif. These results suggest that the duck H4N6 isolate could not cross the species barrier to infect and replicate in mammals, including humans. In addition, screening of the duck serum samples showed that only 0.57 % (2/352) of the individuals had weak but measurable hemagglutination inhibition (HI) antibody titers. The low antibody prevalence data were also supported by the failure to detect H4N6 virus (0/56) in clinical nasal swabs of the ducks. These data indicate an alternate reservoir for the H4N6 virus.

[Molecular evolution and correlation of HN and P gene among the field Newcastle disease viruses].

The goal of this study is to research the genetic characteristics and relationship between HN and P genes of NDV. The nucleotide sequence and deduced amino acid sequence were analyzed for the Hemagglutinin-neuramindase (HN) and Phosphoprotein (P) gene of twelve field isolates of Newcastle disease virus (NDV) during 1997-2005 in China. The HN and P gene sequences of fifteen NDV reference strains from GenBank were also used in this study. The molecular evolution distance of nucleotides and amino acids were calculated by MEGA 4.0 software, and analysis of variance and correlations were analyzed by SPSS11.0 software among different length sequences of the HN gene or P gene. The nucleotide and amino acids correlation of HN and P gene were analyzed respectively. The correlation of evolution distance and isolation year were also calculated. The results indicated that there were difference and good correlation of nucleotide and amino acid among different length sequences of the HN gene or P gene. These results revealed that the HN and P gene of NDV have the different response to selective pressure to adopt to landscape and closely relationship on heredity mutations. Nucleotide variations of HN and P gene have relationship with isolation year of strains.