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A safe, convenience, and effective vaccine for controlling avian influenza virus infection is crucial in scale poultry production. Yeasts are considered useful vaccine vehicles for the delivery of antigens, which has been used to protect human and animal health. We report here the development of H9N2 strain hemagglutinin (HA)-based recombinant protein vaccines (rH9HA) and DNA-RNA-combined vaccine (rH9-DNA-RNA) in Saccharomyces cerevisiae for the first time. The immunogenicity assay indicated that both rH9HA and rH9-DNA-RNA could induce robust production of serum IgG, mucosal sIgA, and cellular immune responses. The reshape and diversification of gut microbiota and an enriched Lactobacillus, Debaryomyces were observed after oral immunization with rH9HA or rH9-DNA-RNA yeast vaccine, which might contribute to modulate the intestinal mucosal immunity and antiviral process. Oral immunized birds with either rH9HA or rH9-DNA-RNA were effectively protected from H9N2 virus challenge. Our findings suggested that yeast-derived H9N2 HA-based recombinant protein vaccines and DNA-RNA-combined nucleic acid vaccines are feasible and efficacious, opening up a new avenue for rapid and cost-effective production of avian influenza vaccines to achieve good protection effect. [ABSTRACT FROM AUTHOR]

H9N2 avian influenza has been prevalent in chicken flocks of China for years. In the first half year of 2018, clinical cases of suspected H9N2 infection were collected from chicken flocks in Shandong province. Nine strains of H9N2 influenza virus were isolated. The pathological changes of the dead chickens were mainly respiratory inflammation, renal swelling, and secondary infection. The microscopic lesions were consistent with the pathogenic characteristics of H9N2 influenza virus. From November 2017 to June 2018, a total of 3,380 serum samples were randomly collected from commercial laying hens in Shandong Province. The H9 antibody levels were tested with the isolated strain (CK/SD/231/17) as the antigen. It showed that the average of antibody titers of H9 avian influenza was 9.24 1og2. Hemagglutination inhibition experiments were conducted on chicken serum with the vaccine virus and the isolated virus (CK/SD/231/17) as the antigens. It was found that the antibody titer measured with the vaccine virus was 1 or 2 titers higher than the isolated strain. It indicated that the antigenicity of H9N2 circulating strain was different from that of vaccine strain. The nucleotide sequences of HA gene of these recent H9N2 avian influenza virus isolates shared homologies from 93.8 to 99.9%. Phylogenetic analysis revealed that the eight gene segments of the viruses were in the same clades with G57 gene reference strain. The amino acid site analysis of influenza resistance showed that the virus was sensitive to neuraminidase inhibitors and resistant to amantadine. Highlights : The protection rate of the H9N2 AIV vaccine almost reached 100% before 2016, but the antibody level of serum samples showed high diversity in this study, which means the poultry were infected. The antigenicity of isolated H9N2 strains was different from that of vaccine strain. Current available vaccines may provide only limited protection. [ABSTRACT FROM AUTHOR]

Avian leukosis virus subgroup J has been found to infect many types of chickens with various genetic backgrounds. The ALV-J strain NX0101, which was isolated from broiler breeders in 2001, mainly induces the formation of myeloid cell tumors. However, strain HN10PY01, which was recently isolated from laying hens, mainly induces the formation of myeloid cell tumors and hemangioma. In order to determine the difference in pathogenicity of the 2 strains in broiler chickens, 2 groups of chicken embryos were infected with NA0101 and HN10PY01 separately. A comparison was made of the mortality, oncogenicity, body weights, indexes for immune organs, levels of ALV group-specific antigen p27, and mRNA expression levels of the tumor-related gene, p53 , in ALV-J-infected birds and immune organs of theses chickens in response to Newcastle Disease Virus (NDV) and avian influenza virus subtype H9 (AIV-H9) vaccination. The results indicated that strain NX0101 was highly pathogenic in broiler chickens and led to a 30% mortality rate and 45% oncogenicity, compared with the HN10PY01-infected birds. Weight of chickens was also significantly lower after 15 wk (P < 0.05). In addition, the mRNA expression levels of tumor-related p53 in medulla, liver, and lung in broilers infected with strain NX0101 were significantly higher than those infected with strain HN10PY01 (P < 0.05). These results indicated that strain NX0101 had a higher replication ability in broiler chickens. The findings of this study will contribute to further elucidating the mechanisms underlying host susceptibility and tumor classification in ALV-J-infected chickens. [ABSTRACT FROM AUTHOR]