Influence of dose and route of inoculation on responses of chickens to recombinant fowlpox virus vaccines.

The influence of dose and route of inoculation on responses of chickens to vaccination with recombinant fowlpox viruses (rFPVs) expressing an influenza haemagglutinin (HA) (FPV-HA) and the infectious bursal disease virus (IBDV) VP2 antigen (FPV-VP2) has been evaluated. Antibody responses to influenza and fowlpox virus were generated following vaccination via the wing web by subcutaneous inoculation or skin scarification. Intranasal and conjunctival inoculation failed to induce antibodies to FPV or influenza. Following direct intratracheal inoculation antibodies developed to influenza but not FPV. Dose response studies with the FPV-HA and FPV-VP2 recombinants showed that good responses to FPV and the vaccine antigen could be generated over a wide (10000 fold) dose range following wing web inoculation. The responses generated by the FPV-VP2 recombinant over this vaccine dose range protected against IBDV infection of the bursae following challenge with the Australian IBDV 002/73 isolate. These data suggest that effective application of rFPVs for poultry vaccination may be restricted to wing web and parenteral routes of inoculation.