Submitted to: Molecular Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2007
Publication Date: 4/20/2007
Citation: He, H., Genovese, K.J., Nisbet, D.J., Kogut, M.H. 2007. Synergy of CpG oligodeoxynucleotide and double-stranded RNA (poly I:C) on nitric oxide induction in chicken peripheral blood monocytes. Molecular Immunology. 44:3234-3242. Interpretive Summary: DNA and RNA are nucleic acids that make up genetic blueprint of life and control chemical reactions in all cells. Monocytes are one type of white blood cell found in chickens. These monocytes can recognize bacterial DNA and viral RNA and produce chemicals that can kill bacteria and viruses. These bacteria- and virus-killing chemicals help birds fight infections and therefore stay healthy. CpG-ODN and poly I:C are two synthetic chemicals that are similar to the bacterial DNA and viral RNA, respectively. We have performed experiments to see if chicken monocytes produce bacteria-and virus-killing chemicals when they are exposed to CpG-ODN and poly I:C. We found that chicken monocytes are able to recognize CpG-ODN and poly I:C and produce bacteria-and virus-killing chemicals, such as nitric oxide. We have also found that chicken monocytes can produce more nitric oxide when they are exposed to both CpG-ODN and poly I:C at the same time. This information is important to the pharmaceutical and poultry industries in the United States because it may offer a new method of producing healthy chickens and reduce the use for antibiotics.
Technical Abstract: Toll-like receptors (TLRs) recognize microbial components and initiate the innate immune responses that control microbial infections. We have investigated the innate immune response of chicken monocytes to ligands of TLR3 and TLR9, poly I:C, the analog of viral double-stranded RNA, and CpG-ODN, bacterial CpG-motif containing oligodeoxydinucleotide, by measuring the induction of nitric oxide (NO) synthesis. Our results show that poly I:C and CpG-ODN synergized the induction of NO in chicken monocytes. When stimulated separately, CpG-ODN induced significant NO production in the chicken monocytes; whereas, poly I:C stimulated very little NO production. In combination, CpG-ODN and poly I:C induced significantly higher level of NO in chicken monocytes than either agonist alone. The addition of poly I:C prior to or simultaneously with CpG-ODN was required for the synergy. No synergistic effects on NO production were observed when monocytes were stimulated with combinations of CpG-ODN or poly I:C with other TLR agonists. Unlike chicken monocytes, cells of a chicken macrophage cell line HD11 were readily stimulated to produce NO by both CpG-ODN and poly I:C with no synergism on NO induction when HD11 cells were stimulated by a combination of CpG-ODN and poly I:C. Using a pharmacological inhibitor, we also demonstrated that double-stranded RNA-dependent protein kinase (PKR) is indispensable for stimulation of NO production by CpG-ODN alone or in combination with poly I:C in both chicken monocytes and HD11 cells. Our results show that a combination of bacterial DNA and dsRNA induces an enhanced inflammatory immune response that has both antiviral and antibacterial activity in primary chicken monocytes.