The immune responses of sheep after DNA immunization with, Toxoplasma gondii MAG1 antigen—with and without co-expression of ovine interleukin 6

The aim of this study is to compare the immune responses of sheep stimulated by the intramuscular injection of a liposome formulated—DNA plasmid encoding the Toxoplasma gondii MAG1 antigen only or co-expressed with ovine IL-6. Forty-five, 2-year-old sheep were divided into four groups. Group 1 received an empty pVAXIg plasmid, group 2 no treatment, group 3 liposome formulated plasmid pVAXIgMAG1 and group 4, pVAXIgMAG1 plus pVAXovIL-6 plasmids. All the animals were inoculated at weeks 0 and 4. The injection of sheep with a plasmid encoding for MAG1 only or a MAG1 plasmid co-expressed with a plasmid encoding for ovine IL-6 produced humoral immune responses. The plasmids containing MAG1 elevated significantly serum IgG1 and IgG2 levels 2 weeks and onwards after the first injection of the plasmids. Co-expression of IL-6 with MAG1 had no effect on IG1 or IG2 levels illustrating that IL-6 in the formulation used had no modulating effect on any measured immune response.