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The ongoing global spread of Newcastle disease underscores the crucial need for continued research on the efficacy of current vaccines against various circulating strains of Newcastle disease virus (NDV). The fusion gene of a representative Egyptian genotype VII.1.1 strain was used to substitute its corresponding gene in the K148/08 vaccinal strain after site directly mutating its cleavage site from 112RRQKRF117 to 112GKQGRL117. Fusion gene exchange between GVII and GI did not affect the thermostability of GI K148/08. Attenuation of the rescued virus was confirmed by mean death time 144 h with an intracerebral pathogenicity index of 0.00. Survival analysis after the challenge experiment confirmed that 107 EID50 was the protective dose of rK148/GVII-F. The haemagglutination inhibition level of antibodies required for full clinical protection was > 3.3 log2 for rK148/GVII-F and > 4.1 log2 for both K148/08 and LaSota. Oropharyngeal viral shedding was reduced on the 5th and 7th days post-challenge in the rK148/GVII-F vaccinated group. Replication and tropism investigations confirmed the respirotropic nature of LaSota, enterotropic nature of K148/08, and further attenuation of rK148/GVII-F. Altogether, rK148/GVII-F is a thermostable, safe, effective, and genetically stable vaccine candidate that could be adequate for use in countries that encounter GVII.1.1 and in those with tropical climate, such as most Middle Eastern countries. A thermostable, safe, and effective NDV GVII recombinant vaccine was generated. Fusion gene replacement with GVII did not affect GI K148/08 virus thermostability. Strain rK148/GVII-F provided adequate protection against a lethal NDV challenge. Oropharyngeal shedding was significantly reduced on post-challenge days 5 and 7. [ABSTRACT FROM AUTHOR]

In 2020, the Y280-lineage H9N2 low-pathogenic avian influenza virus (LPAIV) was introduced into South Korea for the first time. Current vaccines are focused on the control of Y439-like viruses; however, there are continuous reports of decrease in egg production and secondary infections caused by Y280-lineage H9N2 LPAI infection in chickens. Therefore, there is an urgent need to develop effective novel vaccines against Y280-lineage H9N2 LPAI. Most commercialized avian influenza vaccines are oil-adjuvanted inactivated vaccines, which are labour-intensive to administer and require higher dosage. In this study, rK148/Y280-HA, a novel recombinant Newcastle disease virus (NDV) vectored vaccine against Y280-lineage H9N2 LPAI, was developed and evaluated using two mass-applicable administration methods, spray vaccination and drinking water vaccination. Regardless of low serum antibody haemagglutination inhibition titres against NDV and Y280-lineage H9N2 LPAI after applying the rK148/Y280-HA vaccine, vaccination with either administration method protected chickens against virulent NDV and Y280-lineage H9N2 LPAIV after the challenge. Taken together, these results indicate that the rK148/Y280 vaccine can be administered using facile mass-application methods to provide protection against the Y280-lineage LPAI. RESEARCH HIGHLIGHTS NDV vectored vaccine harbouring Y280-lineage H9N2 HA protein was successfully generated. NDV vectored vaccine provides protection against NDV. NDV vectored vaccine with H9N2 HA protects against homologous H9N2 LPAIV. [ABSTRACT FROM AUTHOR]