The Retroviral Diseases Section of the HIV and AIDS Malignancy Branch conducts translational clinical and laboratory research aimed at the development of novel therapies for HIV infection and AIDS- related malignancies. It also conducts laboratory research focused on an understanding of these diseases. During the past year, the group has investigated the role of conserved cysteines at positions 67 and 95 on the activity of HIV protease. We have found that glutathiolation of Cys 95 (in the dimer interface) abolishes HIV-1 protease activity, while glutathiolation of Cys 67 can enhance activity. HIV virions with mutations of Cys 95 and Cys67 have been generated and we are studying the effects that these mutations have on the fitness of HIV under varying conditions. We are exploring the regulation of HIV-2 protease and have found that a methionine in position 95 of HIV-2 acts in a way similar to the cysteine in position 95 of HIV-1 in terms of regulating the protease activity. We are studying the mechanism for this regulation and assessing whether this is a general mechanism for regulation of retroviral proteases. HIV from some patients who have developed resistance to protease inhibitors have been also found to develop a mutation in Cys95, and we are trying to understand the evolutionary pressures leading to this mutation. This work on HIV protease has identified the dimer interface as a potential therapeutic target, and we are attempting to design inhibitors of HIV protease that act as this site. We are also investigating the role of a newly discovered herpesvirus, called Kaposi's sarcoma-associated herpesvirus (KSHV) or human herpesvirus-8 (HHV-8), in the pathogenesis of Kaposi's sarcoma (KS). We have found that hypoxia can activate latent KSHV to undergo lytic replication. We are currently exploring the mechanism for the effect, and have preliminary evidence that at least two genes of KSHV have functional hypoxia response elements (HRE) in their promoter regions that respond to increased cellular levels of hypoxia inducible factors (HIFs). We are also conducting several clinical trials to evaluate novel therapies for Kaposi's sarcoma with a focus on anti-angiogenesis approaches. We have recently found that the anti-herpes drug cidofovir, which has in vitro activity against KSHV, does not induce remissions in patients with KS. A separate clinical trial, however, provided evidence that the anti-angiogenesis agent thalidomide is active in a subset of patients with KS. We are also exploring the relationship between anti-HIV therapy and KS. We have found preliminary evidence that the cytokine IL-12 has long-acting activity in Kaposi's sarcoma have initiated a trial to study the combination of IL-12 and a liposomal anthracycline in patients with advanced KS. We are also studying infusional chemotherapy and IL-12 as therapy for AIDS-associated lymphoma. In regard to anti-HIV therapy, a clinical trial is under way to study two HIV envelope peptide vaccines in HIV-infected patients in combination with highly active antiretroviral therapy. Preliminary results indicate that the vaccine can boost proliferative T cell responses against HIV in a majority of patients. A study is planed to investigate a vaccinia-virus based HIV vaccine. 100% AIDS related