Active immunization against Pneumocystis carinii with p55-v3 DNA vaccine in rats.

Pneumocystis pneumonia (PCP) occurs predominately in patients with impaired immunity. Because standard PCP chemoprophylaxis and chemotherapies have limitations, immunotherapy, particularly vaccination, offers an attractive alternative approach for PCP prevention and treatment. The goal of this study was to evaluate the potential of DNA vaccines targeting two closely related antigens, p55-v0 and p55-v3, in an immunosuppressed rat PCP model. We found that immunization with p55-v0 and p55-v3 DNA vaccines afforded a similar level of protection to rats against PCP, as evidenced by significant reductions in organism burdens, improved histological scores, and lower lung weight to body weight ratios. Additionally, vaccination elicited both cellular and humoral immunity in immunosuppressed rats. Our data suggest the potential of p55 DNA vaccines to protect against PCP in rats. Future work should focus on epitope mapping and identifying protective moieties in each gene.