Protection against Eimeria intestinalis infection in rabbits immunized with the recombinant elongation factors EF1α and EFG.

Eimeria intestinalis is the most pathogenic species of rabbit coccidiosis, causing weight loss, diarrhea, and even acute death. The currently used anticoccidial drugs against E. intestinalis in rabbits are associated with drug resistance and residues. Immunological control might be a potential alternative. We cloned and expressed the E. intestinalis recombinant EF1α and EFG (r Ei -EF1α and r Ei -EFG, respectively). Rabbits were immunized subcutaneously every 14 days with 100 µg of r Ei -EF1α and r Ei -EFG and followed by 5 × 10 4 E. intestinalis sporulated oocysts orally challenge. Serum samples were collected every 7 days to measure the levels of specific antibodies and cytokines. On post-challenge day 14, rabbits were sacrificed and the anticoccidial index was evaluated. The rabbits of PBS challenged groups exhibited anorexia, diarrhea, marked intestinal wall thickening, and white nodules that formed patches, while rabbits from the r Ei -EF1α or r Ei -EFG challenged group exhibited milder symptoms. The r Ei -EF1α group showed a 75.18% oocyst reduction and 89.01%wt gain; the r Ei -EFG group had a 60.58% oocyst reduction and 56.04%wt gain. After vaccination, specific IgG levels increased and stayed high ( P < 0.05). The IL-4 and IL-2 levels of r Ei -EF1α immunized groups showed a significant increase after immunization ( P < 0.05). Both r Ei -EF1α and r Ei -EFG could induce humoral and cellular immune responses. In contrast, rabbits immunized with r Ei -EF1α were better protected from challenge by E. intestinalis than r Ei -EFG.