Evaluation of a Subunit H5 Vaccine and an Inactivated H5N2 Avian Influenza Marker Vaccine in Ducks Challenged with Vietnamese H5N1 Highly Pathogenic Avian Influenza Virus

Abstract

The protective efficacy of a subunit avian influenza virus H5 vaccine based on recombinant baculovirus expressed H5 haemagglutinin antigen and an inactivated H5N2 avian influenza vaccine combined with a marker antigen (tetanus toxoid) was compared with commercially available inactivated H5N2 avian influenza vaccine in young ducks. Antibody responses, morbidity, mortality, and virus shedding were evaluated after challenge with a Vietnamese clade 1 H5N1 HPAI virus [A/VN/1203/04 (H5N1)] that was known to cause a high mortality rate in ducks. All three vaccines, administered with water-in-oil adjuvant, provided significant protection and dramatically reduced the duration and titer of virus shedding in the vaccinated challenged ducks compared with unvaccinated controls. The H5 subunit vaccine was shown to provide equivalent protection to the other two vaccines despite the H5 antibody responses in subunit vaccinated ducks being significantly lower prior to challenge. Ducks vaccinated with the H5N2 marker vaccine consistently produced antitetanus toxoid antibody. The two novel vaccines have attributes that would enhance H5N1 avian influenza surveillance and control by vaccination in small scale and village poultry systems.

Protective Efficacy of a Single Dose of Baculovirus Hemagglutinin-Based Vaccine in Chickens and Ducks Against Homologous and Heterologous H5N1 Virus Infections

“…Our results suggest that the different doses of vaccine antigens against HP H5N1 influenza viruses may be needed to protect chickens or ducks. The previous studies with HA protein expressed by baculovirus could provide protective immunity to ducks (5,28,29). When the expressed HA protein by baculovirus encoding HA of A/Vietnam/1203/04 (H5N1) was inoculated into ducks with water-in-oil adjuvant, the immunized ducks were protected from the lethal infections of FIG.…”

“…A/Vietnam/1203/04 (H5N1) with the reduction of duration and titer of virus shedding (5). The triple baculovirus recombinant encoding H5, N3, and M protected ducks from the infection of homologous H5N3 low pathogenicity avian influenza virus (28,29).…”

Vaccine Control of Avian Influenza H5N1 in Poultry: Need for a Positive Marker

“…In our laboratory study, Peking ducks vaccinated with a commercially available inactivated H5N2 whole virus vaccine (Nobilis) produced detectable H5 HI antibodies by 3 weeks post-vaccination, which steadily increased in titre over a five-week period. Importantly, protection against HPAI H5N1 virus afforded by the avian influenza virus marker vaccine (TT/H5N2) was equal to the homologous avian influenza virus vaccine (H5N2) in ducks and did not interfere with antibody responses to influenza virus antigens contained in the vaccine [20]. Therefore, evaluation studies of the TT marker for avian influenza vaccination encompassed LPAI H6N2 and HPAI H5N1 vaccinated ducks in Australia and Hong Kong SAR, respectively [19,20].…”

“…Therefore, evaluation studies of the TT marker for avian influenza vaccination encompassed LPAI H6N2 and HPAI H5N1 vaccinated ducks in Australia and Hong Kong SAR, respectively [19,20]. Moreover, the TT marker has the potential to be used for detection of silent infection in vaccinated ducks, with the development of an anamnestic response to H5 in vaccinated ducks infected with HPAI H5N1 virus [20]. Eradication of H5N1 virus from ducks requires widespread vaccination, boosters of larger antigen doses, preferably before ducks are sent out to graze, and thus segregation of poultry species for control programs [21].…”

“…Importantly, protection against HPAI H5N1 virus afforded by the avian influenza virus marker vaccine (TT/H5N2) was equal to the homologous avian influenza virus vaccine (H5N2) in ducks and did not interfere with antibody responses to influenza virus antigens contained in the vaccine [20]. Therefore, evaluation studies of the TT marker for avian influenza vaccination encompassed LPAI H6N2 and HPAI H5N1 vaccinated ducks in Australia and Hong Kong SAR, respectively [19,20]. Moreover, the TT marker has the potential to be used for detection of silent infection in vaccinated ducks, with the development of an anamnestic response to H5 in vaccinated ducks infected with HPAI H5N1 virus [20].…”