Oligodeoxynucleotides containing CpG motifs (CpG-ODN) predominantly induce Th1-type immune response in neonatal chicks

Earlier, we demonstrated that intramuscular administration of oligodeoxynucleotides containing CpG motifs (CpG-ODN) induces protection in neonatal chicks against a lethal challenge of Escherichia coli. However, the mechanism of induction of the protection was not clear. In an attempt to elucidate the mechanism of induced protection, we determined the kinetics of expression of cytokines/chemokines in the spleen and bursa of Fabricius of newly hatched chicks that had received intramuscular administration of CpG-ODN or non-CpG ODN compared to saline-treated controls. SyBr green, real-time quantitative reverse transcription polymerase chain reaction (RT-PCR) analysis of the RNA demonstrated increased expression of IL-1 β, IL-6, IL-8, IL-10, IL-18, IFN- γ and MIP-3 α mRNAs in the spleen and; IL-10 and IFN- α in bursa of Fabricious of chicks that had received CpG-ODN. However, non-CpG ODN failed to induce any of the cytokine. The increased level of IL-18 and IFN- γ but not IL-4 mRNA suggests that the administration of CpG-ODN elicits a Th1 biased immune response, which may be important in inducing protection against infections in neonatal chicks. To our knowledge, this is the first report evaluating the induction of cytokines/chemokines in neonatal chicks following administration of CpG-ODN.