Immunoprophylactic evaluation of recombinant gametocyte 22 antigen of Eimeria tenella in broiler chickens
Gametocyte proteins are being explored as potential vaccine candidates against Eimeria sp. in chicken since they are the components of the resilient oocyst wall. The aim of this study was to investigate the immunoprophylactic efficacy of recombinant Eimeria tenella gametocyte antigen 22 (EtGam22) in chickens against homologous oocyst challenge. Broiler chicks were subcutaneously immunized individually with 100 μg of recombinant EtGam22 adjuvanted with Montanide ISA 71 VG at 7 days of age and boosted 2 weeks later. The immunized chickens were challenged individually with 1 × 104 sporulated oocysts of E. tenella 1 week post-booster immunization. The anti-EtGam22 IgY and serum cytokine response was measured post-immunization. The results showed that the anti-EtGam22 IgY antibody, serum IFN-γ, IL-2, TGF-β, and IL-4 levels in chickens vaccinated with recombinant protein were significantly increased post-immunization as compared to unimmunized challenged controls (P < 0.05). The peripheral blood lymphocyte proliferation activity was also found significantly higher in EtGam22-immunized group on day 28, i.e., pre-challenge (P < 0.05). Upon homologous oocyst challenge, chickens immunized with rEtGam22 exhibited a significant drop in the total oocyst output per bird (246.78 ± 36.9 × 106, 45.23% reduction) and a significantly higher weight gain (497.7 ± 19.2 g) as compared to unimmunized challenged controls. Taken together, these data indicate that EtGam22 is a potent immunogen for use as a subunit vaccine against cecal coccidiosis in chickens as it induces a diverse and robust immune response involving multiple cytokines and strong antibody titers.
KeywordsCoccidiosis Eimeria tenella Gametocyte antigen Gam22 Immune response
The authors express sincere thanks to the Director, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, India, for providing the necessary facilities to conduct the study.
Compliance with ethical standards
All animal studies were carried out in the Experimental Animal Shed of the Division of Parasitology, ICAR-Indian Veterinary Research Institute, Izatnagar, India. Prior approval for experimental trials and procedures to be used on chickens was obtained from the Institutional Animal Ethics Committee, IVRI (registered with the Committee for the Purpose of Control and Supervision of Experiments on Animals, Ministry of Environment, Forest and Climate Change, Government of India). Permission for the use of recombinant proteins in the experiment was also obtained from the Institutional Biosafety Committee, IVRI, as per the norms of Department of Biotechnology, Government of India.
Conflict of interest
The authors declare that they have no conflict of interest.
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