The safety evaluation of the pVAX-ROP27 DNA vaccine against Eimeria tenella.

DNA vaccines are a promising against avian coccidiosis but they require comprehensive safety evaluation before clinical application. This study assessed the safety and environmental impact of pVAX-ROP27 DNA vaccine against Eimeria tenella in both chickens and mice. Chickens received intramuscular immunizations: single low dose at 1 day (100 μg), repeated doses (100 μg at 7, 14, 21 days), or a high dose (300 μg at 14 days) using three vaccine batches. Mice received a single dose or overdose. Clinical signs, body weight, and histopathology were evaluated. Distribution and persistence of EtROP27 and Kana genes in tissues, faeces, and water were detected by PCR. No adverse reactions or significant weight differences were observed (P > 0.05). Both genes were detected in all tested tissues (heart, liver, spleen, lung, kidney, blood, small intestine, testis, injection site muscle) at 0.5 months but became undetectable by 2 months, suggesting clearance within the detection limit of conventional PCR, with no evidence of genomic integration by this method. No histopathological lesions or environmental gene release (in faeces/water up to 8 weeks) were detected, confirming a favorable safety profile with no detectable tissue damage, integration, or environmental spread within the observation period.