The development of DNA vaccines containing genes expressing specific enterotoxigenic Escherichia coli antigens and cytokines for the enhancement of antibody production

Immunization using DNA vaccines, a promising new technology, has facilitated a powerful new approach to vaccinology as it offers a unique means of stimulating and enhancing immune responses. The objectives of this study were to develop DNA vaccines containing genes capable of expressing enterotoxigenic Escherichia coli (ETEC) virulence factors, antigens and specific cytokines, as genetic adjuvants, for the enhancement of antibody production in mice and chickens.; DNA vaccines were synthesized by insertion of the ETEC K88 fae G or K99 fanC genes into an expression plasmid. These vaccines, when injected into mice and chickens, induced an immune response. Also the injection of both the DNA vaccine and the corresponding protein injection greatly enhanced antibody titers in both mice and chickens compared to that obtained with DNA or protein alone.; A plasmid vector encoding both the K88 faeG antigen gene and a cytokine gene (Interleukin-4, IL-4) co-expressed both proteins and stimulated a high level of anti-K88 fimbriae antibody response, while the plasmid co-expressing both the K88 fimbriae and IL-2 suppressed anti-K88 fimbriae antibody response. Interestingly, the interleukins caused a shift in the type of immunoglobulin produced with IL-4 producing a greater concentration of the IgG1 isotype and IL-2 producing a greater concentration of the IgG2a isotype.; A new plasmid that encodes both the K88 fimbrial gene (faeG) and chicken Interleukin-6 (IL-6), as a genetic adjuvant, increased the production of specific antibodies against the K88 fimbriae antigen in chickens compared to that obtained with the vaccine encoding only the faeG. In addition, the vaccine containing both genes expressed both the K88 fimbriae and chIL-6 proteins yielding a positive immunochemical band at 32 kDa with the anti-K88 fimbriae antibody and positive bands at approximately 36 and 32 kDa with the anti-chIL-6 antibody.; These data demonstrate that a DNA vaccine alone can stimulate an antibody response to ETEC antigen and that this response can be enhanced by co-injection of an antigen or by immunization with a DNA vaccine containing the gene of interest and a genetic adjuvant such as the IL-4 gene in mice and IL-6 in chickens. DNA vaccines offer many advantages relative to protein immunization as they are also safer, less evasive, provide long lasting immunity and are less expensive.