INTRADERMAL IMMUNIZATION OF RATS WITH PLASMID DNA ENCODING SCHISTOSOMA-MANSONI 28 KDA GLUTATHIONE-S-TRANSFERASE

Direct administration of plasmid DNA encoding an antigen represents an attractive approach to vaccination against infectious diseases, parti cularly in developing countries where easy-to-handle and cost-effectiv e vaccines are needed. We have investigated the potential of DNA immun ization to induce a specific antibody response against Schistosoma man soni, using plasmid-DNA encoding the protective antigen, S. mansoni 28 kDa glutathione S-transferase (Sm28GST). Since S. mansoni parasite pe netrates into its host through the skin, this tissue was chosen for pl asmid DNA delivery. Following plasmid DNA administration into the skin of rats, the parasite antigen was detected in skin cells by immunohis tochemistry. Three administrations of 200 mu g plasmid at 14 day inter vals led to the induction of a long-lasting specific IgG antibody resp onse in the sera of immunized immunized rats, with a predominance of I gG2a and IgG2b subclasses. Sera of immunized animals were able to medi ate antibody-dependent cellular cytotoxicity in vitro, leading to the specific killing of parasite larvae. A parasite challenge performed on plasmid DNA-immunized animals induced a strong and rapid boosting eff ect on the specific IgG antibody response. These results demonstrate t he potential of genetic immunization via the skin with plasmid DNA enc oding Sm28GST for inducing immune responses with protective patterns a gainst an S. mansoni infection.