Eimeria maxima vaccination via Pichia pastoris recombinant vector for coccidia protection in broiler chickens

Coccidiosis remains one of the most devastating protozoal diseases faced by the global poultry industry, and multiple drug options for control are classified as antibiotics, which limits treatment options. Moreover, coccidiosis vaccines are known to contribute markedly to bacterial enteropathies such as necrotic enteritis. Many strategies, including vaccination, are used to control this illness, yet outcomes are variable. Here we describe the application of a novel recombinant vaccine targeting Eimeria spp. in Eimeria maxima (EM) inoculated broilers. A new Pichia pastoris vaccine-vector expressing thrombospondin-related adhesive protein (TRAP) family, rhomboid protease (ROM5) and high mobility group box 1 (HMGB1) protein has been previously developed. In experiment 1, we sought to compare live and killed forms of this vaccine. The comparison involved high (1x107 cell/mL) or low (1x106 cell/mL) doses using either oral or subcutaneous routes. Our previous vaccine with a Bacillus-vectored TRAP-ROM5-HMGB1 showed protection against EM M6 innoculation. Experiment 2 compared the Bacillus and Pichia-vector efficacy against EM M6 innoculation. In experiment 3, timing and the delivery of the vaccines were compared. However, this vaccine was carrying the zeocin gene as the marker. To evaluate the vaccine when this gene was removed, a fourth experiment was conducted. Results showed that there were no significant differences in body weight gain (BWG) or percent change in BWG (%ChangeBWG) relative to the positive control in experiments 1 or 2. In experiment 3, BWG was significantly higher in chickens that were vaccinated via drinking water at day-of-hatch or at d5 then boosted with the same vaccine via same route at d14. No differences were observed for lesion scores (LS) in any of the experiments. Most importantly, quantification of oocysts per gram (OPG) of feces was significantly lower in all groups vaccinated with a form of the Pichia-vectored vaccine especially at the level of accumulative oocysts shedding or oocysts shedding per bird in experiments 2 and 3. In experiment 4, the differences in BWG, %ChangeBWG, lesion scores and OPG were all non-significant. Overall, this approach to vaccination, or augmentation of live oocyst-based vaccines, appears promising.   
 
Keywords: Eimeria, recombinant, avirulent, vaccine, Pichia.

Abstract presented at the 3rd International Symposium on Alternatives to Antibiotics 2019.