Adaptive amino acid substitutions enable transmission of an H9N2 avian influenza virus in guinea pigs.

H9N2 is the most prevalent low pathogenic avian influenza virus (LPAIV) in domestic poultry in the world. Two distinct H9N2 poultry lineages, G1-like (A/quail/Hong Kong/G1/97) and Y280-like (A/Duck/Hong Kong/Y280/1997) viruses, are usually associated with binding affinity for both α 2,3 and α 2,6 sialic acid receptors (avian and human receptors), raising concern whether these viruses possess pandemic potential. To explore the impact of mouse adaptation on the transmissibility of a Y280-like virus A/Chicken/Hubei/214/2017(H9N2) (abbreviated as WT), we performed serial lung-to-lung passages of the WT virus in mice. The mouse-adapted variant (MA) exhibited enhanced pathogenicity and advantaged transmissibility after passaging in mice. Sequence analysis of the complete genomes of the MA virus revealed a total of 16 amino acid substitutions. These mutations distributed across 7 segments including PB2, PB1, PA, NP, HA, NA and NS1 genes. Furthermore, we generated a panel of recombinant or mutant H9N2 viruses using reverse genetics technology and confirmed that the PB2 gene governing the increased pathogenicity and transmissibility. The combinations of 340 K and 588 V in PB2 were important in determining the altered features. Our findings elucidate the specific mutations in PB2 contribute to the phenotype differences and emphasize the importance of monitoring the identified amino acid substitutions due to their potential threat to human health.

[Screening of proteins interacting with avian influenza virus nucleoprotein by yeast two-hybrid system in human brain cDNA library].

Avian influenza virus Nucleoprotein (NP) is important in viral transcription, replication and determining host specificity of influenza virus. Yeast two-hybrid technique was applied to screen for proteins interacting with virus nucleoprotein, so as to further elucidate the interaction between virus nucleoprotein and cellular proteins, as well as the interaction between virus and host. To explore new proteins interacted with NP protein, a human brain cDNA library was screened using yeast two-hybrid system with NP as the bait. DNA inserts of the positive AD/library plasmids were sequenced. By the BLAST analysis against the GenBank databases seven positive clones resulted in seven genes. Our results could help for the further study on the molecular mechanism of virus replication, transcription and protein-protein interaction. Further investigations were needed to characterize these interactions.

Identification of a surface protective antigen, HP0197 of Streptococcus suis serotype 2.

Streptococcus suis serotype 2 (SS2) is a porcine and human pathogen with adhesive and invasive properties. As traditional inactive vaccine has obvious shortcomings, to identify protective antigens would undoubtedly contribute to the development of novel vaccines. HP0197 has been identified as immunogenic protein in the previous study but its protective efficacy was not clear. In the present study, the purified recombinant HP0197 protein could elicit a significant humoral antibody response and could confer significant protection against challenge with lethal dose of SS2 in mice and pigs. In addition, the hyperimmune sera against HP0197 could efficiently kill the bacteria in the opsonized phagocytosis test and conferred significant protection against SS2 infection in the experiment of passive immunization. The present study suggests with strong evidence that the identified protective antigen would be a novel and an effective vaccine candidate for SS2.