HIV, AIDS and Virus Pathogenesis: Throughout evolution, humans have been challenged by pathogens new to the species. For the most part, our immune system mounts an adequate response that protects us from the fatal consequences of infection. However, in some instances viruses can circumvent the immune system and cause fatal diseases such as hemorrhagic fever (Ebola virus) and AIDS (HIV). Understanding the host pathogen relationship at a molecular level provides rational approaches to therapy and vaccine development. In addition, it also provides a better understanding of human biology. We are interested in how the HIV causes AIDS and why the immune system is not able to control this infection. Our working hypothesis is that the ancillary genes of HIV, nef, vpu, vpr, and vif, are the determinants of HIV pathogenesis. To evaluate the role of these genes in disease progression, we have developed in vitro and in vivo models that recapitulate HIV infection. Our emphasis has been placed on the Nef gene because of its ability to enhance virus replication in vivo. We have demonstrated that Nef is a multifunctional protein that 1) downregulates cell surface expression of CD4 and MHC I; 2) binds and activates PAK, a serine/threonine kinase; and 3) enhances the intrinsic infectivity of HIV particles. Our long-term goals are to elucidate the molecular basis of Nef function and to develop specific inhibitors with clinical applications.
Cell and Gene Therapy: Mutations in the human genome can cause alterations in gene expression that result in inherited diseases such as cystic fibrosis, hemophilia, sickle cell disease, inborn errors of metabolism etc. Currently, there are no cures for many of these diseases. We therefore have been exploring the possible correction of defective phenotypes by gene addition. This approach, generally known as somatic gene therapy, consists of introducing the correct gene into the patient cells. Our laboratory has developed highly efficient gene transfer systems that permit the introduction of genetic material into a variety of human cell types. Our primary target has been the human hematopoietic stem cell. This cell has very high differentiation and proliferative potential in vivo. Using our gene transfer vectors and human hematopoietic stem cells we have developed a xenograft model in which we can reconstitute the human hematopoietic system in immune deficient mice. This system provides an excellent way to evaluate gene therapy approaches prior to clinical implementation. These gene transfer vectors have also allowed us to address fundamental questions such as intrathymic T cell differentiation, B cell homeostasis, and the regulation of signal transduction pathways in human primary hematopoietic cells.
