Cloning Of Chicken IL-18 CDNA And Its Enhancement To DNA Vaccine Against E. Tenella

The avian coccidiosis is a cytoplastic entozoic parasite disease and may cause severe economic loss of poultry industry. The clinical application of anticoccidial drugs and live vaccines played an immportant role in the control of avian coccidiosis. But the large and long use of chemicals to control coccidiosis in poultry has created problems. For example, chemical resistance has emgerged in certain strain of Eimeria, thereby rending them difficult to treat; the use of the live coccidial vaccines is not convenient and has lower protectivity. To control the coccidiosis better, the withdrawal of coccidiosistats is inevitable and the new methods had to be explored. The strategy of drug-free control and recombinant DNA vaccine have developed the new methods to control coccidiosis. Cytokines are a diverse family of proteins that play a crucial role in regulating the immune system. They determine both the type and extent of an immune response that is generated following infection with a pathogen or after vaccination. Depending on the combination of cytokines produced, a protective immune response can be generated as either an antibody-mediated (Th2) response or a cell-mediated (Th1) response. Interleukin-18(IL-18), produced by different type of cells, is a multifunctional immuno-regulatory cytokine able to induce IFN-γ, GM-CSF, TNF-a and IL-1 in immunocompetent cells, to activate lymphocytes, and to up-regulate the expression of certain chemokine receptors. It mainly participates in the Th1 response, primarily by its ability to induce IFN-γ production by T cells and natural killers, as well as in the immunoregulation of Th2 cells activities.The gene of chicken mature IL-18 was cloned from the total mRNA of chickens splenocytes stimulated by lipopolysaccharide(LPS) through RT-PCR. The IL-18 cDNA was inserted into plasmid vector pMD-18-T and then sequenced. The plasmid pBAD/myc-his-B-IL-18 transformed into E. coli Top 10 was induced by L-(+)-Arabinose and the expressed products were identified by SDS-PAGE. The results indicated that the chicken mature IL-18 cDNA, consisting of 510 nucleotides encoding 170 amino acids, was cloned and...