In vivo effects of CpG oligodeoxynucleotide on Eimeria infection in chickens.

Poultry coccidiosis is the major parasitic disease of poultry and, until now, no recombinant vaccine has been developed. Short oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs (CpG ODNs) have been shown to be effective immunoprotective agents and vaccine adjuvants in mammalian systems. Their use in poultry to protect against intracellular parasites has not been reported to date. The present work investigated the effects of CpG ODN treatment on host susceptibility to Eimeria infection in two chicken strains with different genetic background, SC and TK. The data show that CpG ODN enhanced the birds' resistance to coccidiosis in a normally susceptible chicken strain (TK), as shown by reduced oocyst shedding and improved weight gain. CpG treatment had a differential effect on body weight gains and serum antibody responses, depending on the chicken strain and ODN dose, delivery route, and backbone. This study shows for the first time that CpG ODNs could be used as immunoprotective agents in Eimeria-infected chickens to enhance resistance to the pathogen and improve performance. Future research is needed to optimize their use alone and as vaccine adjuvants that may lead to better and more efficient vaccine applications.