Development and Evaluation of an A aroA / A htrA Salmonella enteritidis Vector Expressing Eimeria maxima TRAP Family Protein EmTFP250 with CD 154 (CD 40L) as Candidate Vaccines against Coccidiosis in Broilers

Coccidiosis is caused by parasites of the genus Eimeria, belonging to phylum Apicomplexa. EmTFP250 is a high molecular mass, asexual stage antigen from Eimeria maxima (EM) strongly associated with maternal immunity in newly hatched chickens. Cloning and sequence analysis predict the antigen to be a novel member of the Thrombospondin-Related Adhesive Protein (TRAP) family. Three novel attenuated Salmonella enteritidis strains (ASE) expressing TRAP oligopeptides in association with a potential immune-enhancing CD 154 sequence, on the outer membrane protein lamB, were developed. Broiler chicks were grouped based on treatment and 108 cfu/chick of vectors expressing one of three sequences, or vehicle alone, was orally administered to each group. At 21 d of age, all groups were challenged with 104 sporulated oocysts/chick orally. Mortality at 5d post-challenge was markedly different (p<0.05) in chickens vaccinated with TRAP Upstream (US). To further evaluate the efficacy of TRAP US as a potential vaccine candidate, a similar study was conducted. Broilers were orally vaccinated with 108 cfu/chick vehicle with TRAP US and CD 154 or sham vaccinated with saline. Coccidia challenge was performed with 105 sporulated oocysts/chick at 22 d of age. Immunized chickens showed remarkable improvement in weight gain (p<0.05) and had reduced mortality (p = 0.055) when compared to non-immunized controls. These two studies underscore the potential of EmTFP250 as a potential candidate for a recombinant vaccine targeting coccidiosis in chickens.