Protection of turkeys against Chlamydophila psittaci challenge by parenteral and mucosal inoculations and the effect of turkey interferon-gamma on genetic immunization

Plasmid DNA (pcDNA1::MOMP A) expressing the major outer membrane protein of an avian Chlamydophila psittaci serovar A strain was tested for its abilit y to induce protective immunity against challenge with the same C. psittaci serovar. A combined parenteral (intramuscular injection) and mucosal route (DNA drops administered to the nares) of DNA inoculation was compared to t hree other, different routes of administration (intramuscular inoculation, DNA drops administered to the nares and aerosol immunization). In addition, the effect of turkey interferon gamma (tIFN-gamma) on intramuscular immuni zation was evaluated by co-expressing pCIneo::tIFN-gamma. A significant lev el of protection was observed in turkeys immunized via the combined parente ral/mucosal route, the intramuscular route or by aerosol. Severe clinical s igns and lesions were observed in the nonvaccinated control groups, in 80% of turkeys inoculated with a mixture of pcDNA1::MOMP A and pCIneo::tIFN-gam ma and in 60% of turkeys vaccinated with DNA drops administered to the nare s. The use of MOMP-based DNA Vaccination as a means of preventing severe cl inical signs and lesions in a turkey model of C. psittaci infection was dem onstrated, as was down-regulation of the immune response by co-expression o f tIFN-gamma.