Reseacrh Of H9N2Avian Influenza Virus Horizontal Transmission Capacity Between The Guinea Pig Model And Construction Of Reverse Genetic System

In this study，we performed the evolutionary analysis of partial gene fragments of5H9N2avianinfluenza virus（AIV）and evaluated their replication ability and horizontal transmission capacity inguinea pig model. We also explored whether virus would obtain the transmission capacity after adaptivepassaged in guinea pig models.The phylogenetic analysis of HA, NA and M genes showed that all5virus strains belonged toCK/Beijing-like lineage, which showed that the lineage of H9N2AIV didn’t happen variation in China’sNorthern provinces. And NS gene phylogenetic analysis showed that three of them belonged to G1-likelineage and the other two belonged to CK/Beijing-like lineage and Korean-like lineage, which containedNS gene of H6N1AIV and H5N1AIV. Five virus strains were all low pathogenic avian influenzaaccording to the HA cleavage site. Three of them only bonded to SAα2,6Gal receptor, while the othertwo only bonded to SAα2,3Gal receptor.Five virus strains could replicate well in lung of mice without pre-adaption, the virus titers rangingfrom4.3⁵.2LogEID₅₀/mL post-infected3days. Three of them were detected in brain with the virustiters from1.5².25LogEID₅₀/mL. During14d observation period, the mice didn’t show obviousclinical symptoms and mental status and appetite were all normal.All virus strains could be detected in respiratory tract and mucosal turbinate of experimentalinfected guinea pigs with average virus titers ranging2.01⁴.5LogEID₅₀/mL. Among virus stains tested,virus could be detected in nasal wash of all inoculated guinea pigs, however, virus was not detected innasal wash of all contact guinea pigs.The result of adaptive passage in guinea pigs for A/Chicken/Jinan/Li-2/2010（H9N2）strain showedthat the ninth adaptive strain obtained the contact transmission capacity in the guinea pig models.Sequence analysis showed, compared to parent virus, the adaptive virus had two amino acid mutationsin HA protein, however, we didn’t find differences in NS,M,NA,NP and PA protein. The P9passagedvirus strain was still binding SAα2,6Gal receptors.To further study of the molecular mechanisms of the spread of influenza virus, we rescued andidentified the A/Chicken/Jinan/Li-2/2010（H9N2）strain by reverse genetics technology.Our results showed that H9N2subtype AIV possessing human-like influenza virus receptorbinding ability can replicate efficiently in mammalian model such as mice and guinea pigs, but fail totransmit between guinea pigs. But H9N2subtype AIV could acquire the contact transmission capacity inguinea pig model through adaption passage in the animals. These results indicated that H9N2subtypeAIV possesses the transmissibility by adaptation in mammal, which have the public health significance.