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 100g of recombinant EtGam22 adjuvanted with Montanide ISA 71 VG at 7days of age and boosted 2weeks later. The immunized chickens were challenged individually with 1x10(4) sporulated oocysts of E. tenella 1week 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-, IL-2, TGF-, 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 +/- 36.9x10(6), 45.23% reduction) and a significantly higher weight gain (497.7 +/- 19.2g) 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.