Mass vaccination against H9N2 avian influenza A virus with a non-transmissible, reassortment-impaired modified live attenuated influenza virus vaccine

Authors: FACCIN, FLAVIO - University Of Georgia; CACERES, JOAQUIN - University Of Georgia; GAY, CLAIRE - University Of Georgia; SEIBERT, BRITTANY - University Of Georgia; BENTEM, NICK VAN - University Of Georgia; RODRIGUEZ, LUIS - University Of Georgia; FRAIHA, ANA - University Of Georgia; CARDENAS, MATIAS - University Of Georgia; GEIGER, GINGER - University Of Georgia; ORTIZ, LUCIA - University Of Georgia; CARNACCINI, SILVIA - University Of Georgia; Kapczynski, Darrell; RAJAO, DANIELA - University Of Georgia; PEREZ, DANIEL - University Of Georgia

Submitted to: Nature
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: The poultry industry is of huge economic and social importance throughout the world, providing a relatively cheap and efficient protein source. Avian influenza is a disease caused by infection with avian influenza virus (AIV). These viruses are naturally found in wild aquatic birds and can infect domestic poultry causing significant mortality and financial losses. Control strategies for poultry against AIV is dependent on biosecurity to keep the virus out and vaccine application when the virus is present. The objective of this collaborative study was to develop and compare modified live (MLV) AIV vaccines for use in poultry. In challenge studies, the MLV vaccines protected birds from H9N2 virus and significantly reduced virus shedding. Importantly, the vaccine can be applied in drinking water which is a major advantage for mass vaccination. Overall, this vaccine could be used as an intervention strategies to protect poultry from future AIV outbreaks.

Technical Abstract: Avian influenza poses a severe threat to poultry production and global food security, prompting the development of vaccination programs in numerous countries. Modified live virus (MLV) vaccines, with their potential for mass application, offer a distinct advantage over existing options. However, concerns surrounding reversion, recombination, and unintended transmission have hindered the progress of MLV development for avian influenza in poultry. To address these concerns, we engineered reassortment-impaired, non-transmissible, safe, immunogenic, and protective MLVs through the rearrangement of internal gene segments and additional modifications to the surface gene segments HA and NA. The unique DRPAVIAN peptide marker was incorporated into HA, while NA was modified to encode the chicken interleukin-18 (ckIL18) gene (MLV-H9N2-IL). In vitro, the MLV-H9N2 and MLV-H9N2-IL candidates demonstrated stability and virus titers comparable to the wild-type H9N2 strain. In chickens, the MLV-H9N2 and MLV-H9N2-IL candidates did not transmit via direct contact. Co-infection studies with wild-type virus confirmed that the altered HA and NA segments exhibited fitness disadvantages and did not reassort. Vaccinated chickens showed no clinical signs upon vaccination, all seroconverted, and the inclusion of ckIL18 in the MLV-H9N2-IL vaccine enhanced neutralizing antibody production. A significant decrease in viral loads post-challenge underscored the protective effect of the MLVs. The MLV-H9N2-IL vaccine, administered via drinking water, proved immunogenic in chickens in a dose-dependent manner, generating protective levels of neutralizing antibodies upon aggressive homologous virus challenge. In summary, this study lays the groundwork for novel and safe MLVs against avian influenza suitable for mass vaccination efforts.