Refractile body antigens (designated SO7\sp′) are prominent in coccidian sporozoites. Different presentation methods on the immune response in chickens were assessed. SO7\sp′ was administered as viable oocysts, freeze-killed sporozoites, recombinant antigen (CheY-SO7\sp′) or naked DNA(pcDNA3-SO7\sp′). Protection (lesion scores, weight gain) and immunogenicity (lymphoproliferation assays, FACS analysis) were measured. Significant protection against lesions from E. tenella infection was noted in birds immunized with oocysts. Reduced lesion scores were seen in birds immunized with sporozoites or pcDNA3-SO7\sp′ (25 μg). Oocyst or pcDNA3-SO7\sp′ (25 μg)-treated birds had significant protection against weight loss. In vitro T-cell assays detected significant blastogenesis by splenic lymphocytes from birds immunized with oocysts, sporozoites or pcDNA3-SO7\sp′ (25 μg). FACS analysis suggests birds immunized with 25 μg pcDNA3-SO7\sp′ had increased CD4+ cells following primary injection and increased CD8+ cells following secondary treatment. Recombinant antigen (CheY-SO7\sp′) was non-protective. Response of pcDNA3-SO7\sp′-injected birds supports DNA immunization strategies for controlling avian coccidiosis.