Evaluation of Adjuvant Effect of Cytosine-Guanosine-Oligodeoxynucleotide in Meat-Type Chickens Coadministered In Ovo with Herpesvirus of Turkey Vaccine

Herpesvirus of turkey (HVT) increases activation of T cells in 1-day-old chickens when administered in ovo. This study evaluated whether adding cytosine-guanosine oligodeoxynucleotides (CpG ODNs) to the HVT vaccine could enhance the adjuvant effect of HVT. We used a CpG ODN dose of 10 mu g per egg. The experimental groups were (1) diluent-only control (sham), (2) HVT, (3) HVT(+)CpG ODN, (4) HVT(+)non-CpG ODN, (5) CpG ODN, and (6) non-CpG ODN control. Cellular response evaluation included measuring the frequencies of macrophages (KUL01(+)MHC-II+), gamma delta T cells (gamma delta TCR+MHC-II+), CD4(+), and CD8(+) T cell subsets, including double-positive (DP) cells. In addition, CD4(+) and CD8(+) T cell activation was evaluated by measuring the cellular expression of major histocompatibility complex class II (MHC-II), CD44 or CD28 costimulatory molecules. An adjuvant effect was considered when HVT(+)CpG ODN, but not HVT(+)non CpG ODN, or CpG ODN, or non-CpG ODN, induced significantly increased effects on any of the immune parameters examined when compared with HVT. The findings showed that (1) HVT vaccination induced significantly higher frequencies of gamma delta+MHC-II+ and CD4(+)CD28(+) T cells when compared with sham chickens. Frequencies of DP and CD4(+)CD28(+) T cells in HVT-administered birds were significantly higher than those observed in the non-CpG ODN group. (2) Groups receiving HVT+CpG ODN or CpG ODN alone were found to have significantly increased frequencies of activated CD4(+ )and CD8(+) T cells, when compared with HVT. Our results show that CpG ODN administration in ovo with or without HVT significantly increased frequencies of activated CD4(+) and CD8(+) T cells.