Comparison of single 1-day-old chick vaccination using a Newcastle disease virus vector with a prime/boost vaccination scheme against a highly pathogenic avian influenza H5N1 challenge.

Avian influenza (AI) vaccines should be used as part of a whole comprehensive AI control programme. Vectored vaccines based on Newcastle disease virus (NDV) are very promising, but are so far licensed in only a few countries. In the present study, the immunogenicity and protection against a highly pathogenic H5N1 influenza challenge were evaluated after vaccination with an enterotropic NDV vector expressing an H5 haemagglutinin (rNDV-H5) in 1-day-old specific pathogen free chickens inoculated once, twice or once followed by a heterologous boost with an inactivated H5N9 vaccine (iH5N9). The heterologous prime/boost rNDV-H5/iH5N9 combination afforded the best level of protection against the H5N1 challenge performed at 6 weeks of age. Two rNDV-H5 administrations conferred a good level of protection after challenge, although only a cellular H5-specific response could be detected. Interestingly, a single administration of rNDV-H5 gave the same level of protection as the double administration but without any detectable H5-specific immune response. In contrast to AI immunity, a high humoral, mucosal and cellular NDV-specific immunity could be detected up to 6 weeks post vaccination after using the three different vaccination schedules. NDV-specific mucosal and cellular immune responses were slightly higher after double rNDV-H5 vaccination when compared with single inoculation. Finally, the heterologous prime/boost rNDV-H5/iH5N9 combination induced a broader detectable immunity including systemic, mucosal and cellular AI and NDV-specific responses.

Immune responses and protection against H5N1 highly pathogenic avian influenza virus induced by the Newcastle disease virus H5 vaccine in ducks.

Ducks play an important role in the epidemiology of avian influenza, and there is a need for new avian influenza vaccines that are suitable for mass vaccination in ducks. The immune responses as well as highly pathogenic avian influenza (HPAI) H5N1 protection induced by a Newcastle disease virus (NDV) vector expressing an H5N1 hemagglutinin (rNDV-H5) were investigated in mule ducks, a hybrid between Muscovy (Cairina moschata domesticus) males and Pekin (Anas platyrhynchos domesticus) females. Immunological tools to measure NDV and H5-specific serum antibody, mucosal, and cell-mediated immune (CMI) responses in ducks have been validated after infection with the vector NDV and an H5N1 low pathogenic avian influenza virus. The effect of maternally-derived antibodies (MDAs) to NDV on the humoral and CMI responses after NDV-H5 vaccination was also investigated. Our results showed the rNDV-H5 vaccine elicits satisfactory humoral and cellular responses in 11-day-old ducks correlating with a complete clinical and virological protection against the H5N1 strain. However, vaccination with rNDV-H5 in the presence of NDV MDA induced lower NDV-specific serum antibody, mucosal, and CMI responses than in ducks with no MDA, while interestingly the H5-specific serum antibody and duodenal IgY response were higher in ducks with NDV MDA. To our knowledge, this is the first report of the use of an NDV vector in ducks and of an HPAI H5N1 challenge in mule ducks, which appeared to be as resistant as Pekin ducks.

Development of specific enzyme-linked immunosorbent assays to evaluate the duck immune response after experimental infection with H5N1 and H7N1 low pathogenic avian influenza viruses.

The role of wild ducks as vectors of avian influenza viruses (AIVs) is well known but the immune response induced by AIV has different patterns according to the species of duck. The local antibody produced on the mucosal surface may play an important role not only in protection but also in limitation of the primary replication at the portal of entry and shedding of the virus. With this aim, specific enzyme-linked immunosorbent assays (ELISAs) for duck IgY, Ig light chain, IgY (heavy chain), IgA, and IgM were developed and used to evaluate the systemic and mucosal response induced in ducks after low pathogenic avian influenza (LPAI) infections. Two different species of ducks (Mule and Pekin), ages (1 wk and 3 wk), and virus strains (H7N1 and H5N1 low pathogenic viruses) were tested in two studies to evaluate the developed tools. In the two studies, systemic and mucosal AIV-specific duck IgY, Ig (light chain), IgY (heavy chain), IgA, and IgM were detected and followed. Therefore, the developed ELISAs proved to be efficient tools allowing the follow-up of the systemic and mucosal responses induced by LPAI infection in ducklings. These tools can be very helpful for the development and evaluation of AI vaccines for ducks.