DNA Immunogens A. DNA Based Induction of Autoimmune 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 autoimmune disease in various animal models. One advantage of this previously untested approach is that it allows for the rapid screening of candidate immunogens (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 are attempting 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?ve obtained in rats and extend them to the mouse. 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 Not long ago, HIV infection was an important cause of morbidity and mortality in the United States. The advent of highly active anti-retroviral therapy (HAART) is entirely responsible for the 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 are genetically engineering these so called peptide mimetope sequences into the HIV envelope gene and using gene therapy vectors to introduce the encoded altered HIV envelope protein into mouse B cells. The immune response to the altered HIV envelope can then be assessed after transfer of the transduced B cells to a syngenic host. To date we have generated peptide mimetope containing HIV envelope constructs and are in the process of introducing them into mouse B cells.
