Comparison of antibody and protective immune responses against Trypanosomacruzi infection elicited by immunization with a parasite antigen deliveredas naked DNA or recombinant protein

Immunization with naked DNA represents an attractive strategy for developme nt of vaccines against a variety of infections including those caused by pr otozoan parasites. Recently, we have described that immunization with a pla smid containing the trans-sialidase (TS) gene induced protective immunity a gainst Trypanosoma cruzi infection in BALB/c mice. The present study was ai med at examining and comparing the effectiveness of immunization using eith er plasmid or recombinant delivered antigens in a mouse strain highly susce ptible to infection (A/Sn). Two plasmids were generated containing the codi ng region for the catalytic domain of TS. TS gene was inserted into pcDNA3 vector with or without the coding region for TS signal peptide. These two p lasmids were found to be equally immunogenic at inducing antibodies to TS o r inhibition of T. cruzi infection. A third plasmid, in which the TS gene w as inserted into the vector VR1012, was as immunogenic as the two others. I mmunization with a TS recombinant protein in alum generated a significantly higher antibody response as measured by ELISA or inhibition of TS enzymati c activity. Most relevant, this immunization reduced the mortality due to a cute infection.