DNA Immunogens A. DNA Based Induction of Disease In the last several years it has been demonstrated that bacterial DNA itself is a potent adjuvant and that it can be used as a vaccine to induce immune responses (to protein antigens encoded by the DNA) that are sufficient to confer protective immunity against a number of pathogens. These observations suggest that so called DNA vaccines could also be used to induce diseases such as retinal degeneration or autoimmune uveitis in various animal models. One advantage of this previously untested approach is that it allows for the rapid screening of candidate disease targets (in their DNA form) by circumventing the need to isolate protein. This is particularly advantageous when it is very difficult to obtain sufficient quantities of purified human proteins to use as immunogens. As a first test of this approach we attempted to establish a DNA vaccine based model of experimental autoimmune uveitis. To date we have shown in rodents that a DNA vaccine encoding human IRBP administered via the SQ, ID, or IM routes elicits a good immune response to the encoded antigen and that the immunized rats, but interestingly not the mice, develop disease. We are presently working to improve the responses that we have obtained in rats and extend them to the mouse by altering the targeting and delivery of these DNA immunogens. Investigations into the basis of the dichotomy between immune response and disease pathogenesis in the mouse should lend further insight into the variables that are responsible for disease penetrance. B. HIV Vaccine The advent of highly active anti-retroviral therapy (HAART) has resulted in a dramatic decline in HIV associated disease in this country. However, there is already evidence that viral resistance to HAART has emerged, suggesting that we may see a return of AIDS. It is clear that the long term solution to HIV infection must include the development of an effective vaccine. For safety reasons, efforts to develop a vaccine have focused on using the recombinant protein subunit components of the virus. However, HIV is a heavily glycosylated virus and the complex carbohydrate structures that are present on its surface are likely to mask important epitopes. Along with investigators at the University of Pennsylvania, we are exploring an alternative strategy to generate immune responses against HIV associated carbohydrate antigens. Our collaborator has identified short peptide sequences that elicit humoral immune responses that strongly cross react with certain carbohydrates. To test whether such anti-carbohydrate responses can enhance an anti-HIV immune response, we have genetically engineered these so-called peptide mimetope sequences into the HIV envelope gene. We have found that the envelope constructs generated to date retain most of their biological activity. We intend to use gene therapy vectors to introduce the altered HIV envelope into mouse B cells and assess the immune response to the altered HIV envelope can then be assessed after transfer of the transduced B cells to a syngenic host. These studies are currently inactive due to a need to increase our efforts in other areas.
