Prior infection of chickens with H1N1 avian influenza virus elicits heterologous protection against highly pathogenic H5N2

A Well-Defined H9N2 Avian Influenza Virus Genotype with High Adaption in Mammals was Prevalent in Chinese Poultry Between 2016 to 2019

H9N2 subtype avian influenza virus (AIV) is widely prevalent in poultry, and the virus is becoming adaptive to mammals, which poses pandemic importance. Here, BALB/c mice were employed as a model to evaluate the adaption in mammals of 21 field H9N2 viruses isolated from avian species between 2016 to 2019 in China. The replication capacity of the viruses was evaluated in the lungs of mice. The pathogenicity of the viruses were compared by weight loss and lung lesions from infected mice. The whole genomic sequences of the viruses were further characterized to define the associated phenotypes of the H9N2 viruses in vitro and in vivo. The results showed that most viruses could replicate well and cause lesions in the mouse lungs. The propagation capacity in MDCK cells and damage to respiratory tissues of the infected mice corresponded to relative viral titers in the mouse lungs. Further genome analysis showed that all of the H9N2 viruses belonged to the same genotype, G57, and contained a couple of amino acid substitutions or deletions that have been demonstrated as avian-human markers. Additionally, nine amino acids residues in seven viral proteins were found to be correlated with the replication phenotypes of the H9N2 viruses in mammals. The study demonstrated that a well-defined H9N2 AIV genotype with high adaption in mammals was prevalent in China in recent years. Further investigations on the role of the identified residues and continuous surveillance of newly identified mutations associated with host adaption should be strengthened to prevent any devastating human influenza pandemics.

Comparison of the virulence of three H3N2 canine influenza virus isolates from Korea and China in mouse and Guinea pig models

Background

Avian-origin H3N2 canine influenza virus (CIV) has been the most common subtype in Korea and China since 2007. Here, we compared the pathogenicity and transmissibility of three H3N2 CIV strains [Chinese CIV (JS/10), Korean CIV (KR/07), and Korean recombinant CIV between the classic H3N2 CIV and the pandemic H1N1 virus (MV/12)] in BALB/c mouse and guinea pig models. The pandemic H1N1 (CA/09) strain served as the control.

Results

BALB/c mice infected with H1N1 had high mortality and obvious body weight loss, whereas no overt disease symptoms were observed in mice inoculated with H3N2 CIV strains. The viral titers were higher in the group MV/12 than those in groups JS/10 and KR/07, while the mice infected with JS/10 showed higher viral titers in all tissues (except for the lung) than the mice infected with KR/07. The data obtained in guinea pigs also demonstrated that group MV/12 presented the highest loads in most of the tissues, followed by group JS/10 and KR/07. Also, direct contact transmissions of all the three CIV strains could be observed in guinea pigs, and for the inoculated and the contact groups, the viral titer of group MV/12 and KR/07 was higher than that of group JS/10 in nasal swabs. These findings indicated that the matrix (M) gene obtained from the pandemic H1N1 may enhance viral replication of classic H3N2 CIV; JS/10 has stronger viral replication ability in tissues as compared to KR/07, whereas KR/07 infected guinea pigs have more viral shedding than JS/10 infected guinea pigs.

Conclusions

There exists a discrepancy in pathobiology among CIV isolates. Reverse genetics regarding the genomes of CIV isolates will be helpful to further explain the virus characteristics.

Association between Interferon Response and Protective Efficacy of NS1-Truncated Mutants as Influenza Vaccine Candidates in Chickens

Influenza virus mutants that encode C-terminally truncated NS1 proteins (NS1-truncated mutants) are attractive candidates for avian live attenuated influenza vaccine (LAIV) development because they are both attenuated and immunogenic in chickens. We previously showed that a high protective efficacy of NS1-truncated LAIV in chickens corresponds with induction of high levels of type I interferon (IFN) responses in chicken embryonic fibroblast cells. In this study, we investigated the relationship between induction of IFN and IFN-stimulated gene responses in vivo and the immunogenicity and protective efficacy of NS1-truncated LAIV. Our data demonstrates that accelerated antibody induction and protective efficacy of NS1-truncated LAIV correlates well with upregulation of IFN-stimulated genes. Further, through oral administration of recombinant chicken IFN alpha in drinking water, we provide direct evidence that type I IFN can promote rapid induction of adaptive immune responses and protective efficacy of influenza vaccine in chickens.

Veterinary influenza vaccines against avian influenza in China

ABSTRACT 

Avian influenza (AI) is an infectious viral illness that affects numerous species of birds, including chickens, ducks, turkeys and geese. Poultry vaccination plays an important role for control of the AI virus and effectively prevents the infection in domestic chickens. However, new, increasingly virulent strains are constantly emerging, for which no vaccines are available. Avian influenza is also responsible for sporadically infecting humans and causing a wide range of clinical outcomes. Here, we review the recent emergence of diverse strains of the AI virus and the use of veterinary vaccines for poultry in China.

Analysis of the phylogeny of Chinese H9N2 avian influenza viruses and their pathogenicity in mice

We isolated nineteen strains of H9N2 influenza virus from farms across five northern Chinese provinces between 2001 and 2012. Sequence analysis of the genes for the two surface glycoproteins revealed that residue 226 of the hemagglutinin (HA) of eight isolates was a leucine. A T300I mutation in three strains resulted in the loss of a potential glycosylation site. The P315S mutation in seven strains added a potential glycosylation site in HA. The isolates CK/HN/323/08 and CK/HN/321/08 had a full-length neuraminidase (NA) that differed from those seen in other isolates. Phylogenetic and molecular analysis revealed that the nineteen strains shared common ancestry with strains BJ/94 and G1. We examined eight gene sequences in the present study and concluded that the HA and NS genes appeared to be derived directly from BJ/94. The remaining six genes evolved from different reference strains. Specifically, the NA and PA genes of CK/HN/321/08 and CK/HN/323/08 clustered with the G9 and Y439 branch, respectively, and the PB2 genes of CK/SD/513/11 and CK/GS/419/12 were in an unknown lineage. We found evidence that seven new genotypes had undergone intra-subtype reassortment. A mouse infection experiment with six selected isolates showed that five of these isolates were able to replicate in mouse lungs without adaptation. Viral replication in infected mice resulted in minimal weight loss, suggesting that these H9N2 avian influenza viruses had low virulence in mammals. Our findings highlight the genetic and biological diversity of H9N2 avian influenza viruses circulating in China and emphasize the importance in continuing surveillance of these viruses so as to better understand the potential risks they pose to humans.