Efficacy of Two Licensed Avian Influenza H5 Vaccines Against Challenge with a 2015 U.S. H5N2 clade 2.3.4.4 Highly Pathogenic Avian Influenza Virus in Domestic Ducks

Abstract

Highly pathogenic avian influenza (HPAI) clade 2.3.4.4 viruses from the H5 goose/Guangdong lineage caused a major outbreak in poultry in the United States in 2015. Although the outbreak was controlled, vaccines were considered as an alternative control method, and new vaccines were approved and purchased by the U.S. Department of Agriculture National Veterinary Stockpile for emergency use. In this study, we evaluated the efficacy of two of these vaccines in protecting Pekin ducks (Anas platyrhynchos var. domestica) against challenge with a H5N2 HPAI poultry isolate. A recombinant alphavirus-based vaccine and an inactivated adjuvanted reverse genetics vaccine, both expressing the hemagglutinin gene of a U.S. H5 clade 2.3.4.4 isolate (A/Gyrfalcon/Washington/41088-6/2014 H5N8), were used to immunize the ducks. The vaccines were given either as single vaccination at 2 days of age or in a prime-boost strategy at 2 and 15 days of age. At 32 days of age, all ducks were challenged with A/turkey/Minnesota/12582/15 H5N2 HPAI virus clade 2.3.4.4. All ducks from the nonvaccinated challenge control group became infected and shed virus; one duck in this group presented mild ataxia, and a second duck died. No mortality or clinical signs were observed in vaccinated and challenged ducks, with the exception of one duck presenting with mild ataxia. Both vaccines, regardless of the vaccination strategy used, were immunogenic in ducks and reduced or prevented virus shedding after challenge. In conclusion, good protection against H5Nx infection was achieved in ducks vaccinated with the vaccines examined, which were homologous to the challenge virus, with prime-boost strategies conferring the best protection against infection.

Widespread detection of highly pathogenic H5 influenza viruses in wild birds from the Pacific Flyway of the United States

“…Laboratory studies suggest that these viruses were well-adapted to the waterfowl host, with experimentally infected mallards remaining asymptomatic while easily transmitting the virus to conspecifics. This is in contrast to the less efficient transmission to contacts seen in infected chickens 32 . These differences may play a role in the different patterns seen in wild birds versus domestic poultry.…”

Chimeric H5 influenza virus-like particle vaccine elicits broader cross-clade antibody responses in chickens than in ducks

“…Given their significant contribution to the epidemiology of HPAI, it is imperative to mitigate the risk of virus infection in domestic ducks through vaccination in order to control the spread of HPAI. Antigenically-matching vaccination has proven effective in protecting domestic ducks against infection and clinical signs following a homologous HPAI H5 virus challenge ( 16 ). Currently developed vaccines, however, have shown suboptimal protective efficacy in domestic ducks, allowing morbidity, mortality, and prolonged viral shedding upon challenges with antigenically distant HPAI H5 viruses ( 11 , 13 ).…”