Development and Evaluation of an Δ aroA / Δ htrA Salmonella enteritidis Vector Expressing Eimeria maxima TRAP Family Protein EmTFP250 with CD 154 (CD 40L) as Candidate Vaccines against Coccidiosis in Broilers
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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. Asian Network for Scientific Information, 2010.