CHRONIC HIV INFECTION: DEVELOPMENT AND CHARACTERIZATION OF CHRONIC INFECTION MODEL SYSTEMS FOR THE EVALUATION OF ANTIVIRAL AGENTS

Abstract

Millions of people worldwide are infected with human immunodeficiency virus (HIV). Latent HIV disease in infected patients is characterized as an asymptomatic phase which can last for over 10 years. Recent studies have shown that virus replication in lymphoid tissues from HIV-infected patients continues at a high level throughout the clinically latent phase. Useful model systems of the latent stage of HIV disease in vivo need to be developed to evaluate therapeutic agents which could be of help to the vast number of infected individuals. Several in vitro model systems of latent HIV-infection (i.e., U1, ACH2, OM10.1) have been developed and utilized in the study of chronic/latent HIV infection. Cell lines of this type have been used to investigate the role of inductive and inhibitory signals on HIV replication. However, a good model in vitro system for evaluating agents capable of reducing the infected cell population or inhibiting the spread of virus from cell to cell is currently unavailable. Such cell-based models could be of tremendous value in the study of chronic/latent HIV infection. Little is known about the biological characteristics of chronically infected cell lines. The purpose of this project was to develop model systems of chronically infected cell populations in order to characterize the chronic state of HIV infection in vitro. Once these model systems were established, a group of antiviral agents with diverse mechanisms of action were evaluated. This evaluation included their effect on virus production and their ability to inhibit virus spread by cell-to-cell transmission. Populations of chronically infected MT2, CEM-SS, H9, U937, and CEM-CCRF cells were derived as part of this study. These chronically infected cell populations were biologically and biochemically evaluated in order to define and characterize the infected cells and to compare them with parental uninfected cells. It was determined that the chronically infected cell populations derived from cytopathically infected MT2 and CEM-SS cells include a larger population of nonproductively infected cells than of productively infected cells. Cells derived from noncytopathically infected H9, U937, and CEM-CCRF cells yielded a population of cells which were predominantly productively infected. These chronically infected cells thus served as good models of chronic HIV infection since they continuously produce virus in the absence of any associated cytopathology. A panel of antiviral agents with diverse mechanisms of action was evaluated to determine their effects on chronic HIV infection and the cell-to-cell spread of virus using these cell-based model systems. One compound, SRI 7755, was identified in these studies that was capable of significantly reducing the number of infected cells in a chronically infected population as well of inhibiting the induction of virus expression in latently infected U1 cells. The major goal of this project was to develop and characterized chronically HIV infected cell lines. The identification of compounds effective in inhibiting or suppressing virus production in these chronically infected cell populations was also demonstrated.