David M. Rekosh
Primary AppointmentProfessor, Microbiology, Immunology, and Cancer Biology
- PhD, Massachusetts Institute of Technology
Jordan Hall 7-88
Charlottesville, VA 22908
Human Immunodeficiency; Virus Gene Expression
The centerpiece of our HIV research is focused on the elucidation of the function of the HIV Rev protein. A primary function of this protein is to facilitate the nucleo-cytoplasmic export of mRNAs that retain complete introns. Cellular mRNAs with retained introns are usually restricted by the cell from exiting the nucleus and since many HIV mRNAs have this property , Rev is essential for HIV replication. To perform its export function , Rev binds to a specific element present in some HIV mRNAs called the Rev Response Element. This RNA-protein complex then interacts , through the leucine-rich nuclear export signal in Rev , with cellular factors such as CRM1 and Ran-GTP to facilitate mRNA export. In addition , we have recently shown that Rev promotes the translation of intron-containing RNA.
Many details about Rev function remain unexplored , and our recent experiments focus on some of these issues. In particular , we are studying how small variations in the sequence of Rev and the RRE can modulate HIV infection. We also are studying the basis for the efficient inhibition of HIV replication by an antisense RNA that is directed against the HIV env gene region. An RNA , very similar to the one we are studying , is in clinical trials , and our recent studies show that the trafficking of this molecule through the Rev pathway is essential for it to be a potent inhibitor of HIV replication.
We are also using cell-based screening assays to identify compounds that specifically target HIV Rev function. A recent screen of 40,000 compounds has led to the identification of two small molecules that inhibit HIV replication by interfering with Rev function. These compounds provide proof of principle that the targeting of Rev by small molecules could lead to the development of a novel class of HIV therapeutics.
The Emergence of Drug Resistance among non Clade B Human Immunodeficiency Viruses
HIV-1 drug resistance assays have become essential parts of monitoring in antiretroviral therapy , as they are useful in designing the selection of appropriate treatment regiments for AIDS patients. The genotypic DNA sequencing method has its limitation in that the algorithms defining drug resistance have only been developed for HIV clade B non-complex mutations and they are only an indrect measure of resistance. However, direct phenotypic methods overcome this problem. Based on a lentivirus Gag-Pol packaging system, we are developing systems using a luciferase reporter gene to easily allow drug resistance to be measured in non Clade B viruses.
Using these assays , as well as genotypic sequencing methods , in collaboration with Dr. Pascal Bessong , of the University of Venda in South Africa we have been defining the prevalence of HIV resistance in the non-treated population in selected areas in Limpopo Province , a rural province in northern South Africa. We are also investigating the impact of polymorphisms on baseline resistance , resistance development and the resistance evolutionary patterns in HIV-1-C infected patients who are undergoing treatment.