Abstract
Cheap, easy-to-produce oral vaccines are needed for control of coccidiosis in chickens to reduce the impact of this disease on welfare and economic performance. Saccharomyces cerevisiae yeast expressing three Eimeria tenella antigens were developed and delivered as heat-killed, freeze-dried whole yeast oral vaccines to chickens in four separate studies. After vaccination, E. tenella replication was reduced following low dose challenge (250 oocysts) in Hy-Line Brown layer chickens (p<0.01). Similarly, caecal lesion score was reduced in Hy-Line Brown layer chickens vaccinated using a mixture of S. cerevisiae expressing EtAMA1, EtIMP1 and EtMIC3 following pathogenic-level challenge (4,000 E. tenella oocysts; p<0.01). Mean body weight gain post-challenge with 15,000 E. tenella oocysts was significantly increased in vaccinated Cobb500 broiler chickens compared to mock-vaccinated controls (p<0.01). Thus, inactivated recombinant yeast vaccines offer cost-effective and scalable opportunities for control of coccidiosis, with relevance to broiler production and chickens reared in low-and middle-income countries (LMICs).
Highlights
Coccidiosis, a disease of the gastrointestinal tract caused by Eimeria parasites, is a considerable burden to the poultry industry economically, estimated to cost over £10 billion per year [1], and in terms of chicken health and welfare, causing diarrhoea and ill-thrift
Three E. tenella (Houghton strain) antigens were selected for surface expression on S. cerevisiae; the ectodomain of Apical Membrane Antigen 1 (EtAMA1), Immune Mapped Protein 1 (EtIMP1) and repeat 3 from Microneme Protein 3 (EtMIC3), one of three identical Microneme Adhesive Region (MAR) domains contained within the ectodomain [16]
Confirmation of protein expression by S. cerevisiae 24 h postinduction was provided by antibody staining and flow cytometry, indicating inducible expression of the E. tenella antigens EtAMA1, EtIMP1 or E. tenella MIC3 R3 (EtMIC3) based upon detection of the 3’ V5 epitope tag
Summary
Coccidiosis, a disease of the gastrointestinal tract caused by Eimeria parasites, is a considerable burden to the poultry industry economically, estimated to cost over £10 billion per year [1], and in terms of chicken health and welfare, causing diarrhoea and ill-thrift. Existing vaccines that consist of controlled oral doses of live or live-attenuated parasites are efficacious and widely used in egg-laying and breeder chicken populations. Despite achieving levels of protection comparable to anticoccidial drugs [2, 3], uptake in the broiler chicken sector has been limited, at least in part because the cost of vaccines is relatively high [1]. Even if demand for existing vaccines increases, it is unlikely that the production of live-attenuated vaccines could be scaled up sufficiently to supply the entire broiler sector. Novel oral vaccines against coccidiosis in chickens would provide a much-needed alternative to these current vaccines as well as in-feed anticoccidial drugs
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