Development of an Inactivated Avian Influenza Virus Vaccine against Circulating H9N2 in Chickens and Ducks

Abstract

Avian influenza virus (AIV) subtype H9N2 is the most widespread AIV in poultry worldwide, causing great economic losses in the global poultry industry. Chickens and ducks are the major hosts and play essential roles in the transmission and evolution of H9N2 AIV. Vaccines are considered an effective strategy for fighting H9N2 infection. However, due to the differences in immune responses to infection, vaccines against H9N2 AIV suitable for use in both chickens and ducks have not been well studied. This study developed an inactivated H9N2 vaccine based on a duck-origin H9N2 AIV and assessed its effectiveness in the laboratory. The results showed that the inactivated H9N2 vaccine elicited significant haemagglutination inhibition (HI) antibodies in both chickens and ducks. Virus challenge experiments revealed that immunization with this vaccine significantly blocked virus shedding after infection by both homogenous and heterologous H9N2 viruses. The vaccine was efficacious in chicken and duck flocks under normal field conditions. We also found that egg-yolk antibodies were produced by laying birds immunized with the inactivated vaccine, and high levels of maternal antibodies were detected in the serum of the offspring. Taken together, our study showed that this inactivated H9N2 vaccine could be extremely favourable for the prevention of H9N2 in both chickens and ducks.

Evolution of prevalent H9N2 subtype of avian influenza virus during 2019 to 2022 for the development of a control strategy in China

“…Our immune protection experiments confirmed that the self-developed vaccine showed better resistance to infection by epidemic strains, significantly reducing the morbidity rate, decreasing pathological damage, reducing shedding, and virus loads in tissues. Our vaccine was similar to other strains in that high titers of virus were still detected in the lungs and trachea on the fifth day after challenge and 75% of chicken throat swabs still contained virus ( Liu et al, 2023 ), which led to nonimmune chickens in the same house being infected by the shedding virus. However, it is worth noting that our vaccine can prevent chickens from shedding viruses through the cloacal cavity (the separation rate of the cloacal swabs is 0%), which may be that the vaccine can reduce or eliminate virus replication in the intestine.…”

Epidemiology, biosafety, and biosecurity of Avian Influenza: Insights from the East Mediterranean region

“…Poultry vaccination is highly valuable in combating avian influenza and controlling the spread of the virus. 132 Vaccinated chickens were found to have high antibody titres after a single dose only, suggesting that protective immunity can be induced with one single dose in chicken. In contrast, ducks and geese produced a drastically low antibody titre compared to chickens after the first vaccine shot.…”

“…Aside from biosecurity, as mentioned earlier, vaccination is the most essential scheme. Poultry vaccination is highly valuable in combating avian influenza and controlling the spread of the virus 132 . Vaccinated chickens were found to have high antibody titres after a single dose only, suggesting that protective immunity can be induced with one single dose in chicken.…”