DNA immunization by intramuscular injection or gene gun induces specific IgG antibodies against a Schistosoma japonicum 22 kDa antigen, Sj22, when fused to the murine Ig K-chain secretory leader sequence

The 22 kDa tegumental surface membrane-associated antigen of Schistosoma japonica, Sj22, is of recognized interest in schistosomiasis vaccine research. However, previous attempts to induce antibody responses against Sj22 by DNA immunization have been unsuccessful. In this report we demonstrate that fusing the Sj22 cDNA to the murine immunoglobulin Ig kappa-chain secretory leader sequence results in the generation of antigen-specific IgG antibodies following DNA immunization. Mice were immunized into the skin with DNA-coated gold microspheres using a gene-gun, or into the quadriceps muscle by intramuscular injection. Both methods of delivery generated antigen-specific IgG antibodies against the 22 kDa schistosome antigen. The use of a secretory leader sequence, such as the murine Ig-kappa chain used in this study, may facilitate the induction of host antibody responses following DNA immunization with other parasite cDNAs.