Studies On The Determinants Of HIV Mutagenesis And Strategies For Its Enhancement

Abstract

Human immunodeficiency virus type-1 (HIV-1) is one of the fastest evolving entities on earth, due in part to a mutation rate that is at least 10,000-fold higher than that of eukaryotic genomic DNA. The adaptability of HIV-1 prevents clearance of the virus by the immune system, promotes drug resistance, and has impeded development of effective vaccines. The viral mutation rate is a composite result of mutations that are contributed by multiple host and viral enzymes involved in viral replication. However, the precise determinants of viral mutagenesis in HIV-1 and the degree of their contribution to HIV-1 genetic diversity remain incompletely understood. Furthermore, differences in viral mutagenesis among different HIV types (e.g., HIV-1 and human immunodeficiency virus type 2, HIV-2) and subtypes have not been explored to date. Lastly, the elimination of HIV-1 infectivity by increasing the viral mutation rate has not been extensively investigated – in terms of mechanism of action and in preclinical and clinical evaluations. Based upon these general observations, this dissertation research was conducted to test the following hypotheses: 1) HIV-1 and HIV-2 have different mutation rates; 2) decitabine, a HIV-1 mutagen, creates G-to-C transversion mutations in the absence of mutational hotspots; 3) 5-azacytidine causes HIV-1 mutagenesis after reduction to 5-aza-2’-deoxycytidine (i.e. decitabine); 4) the anti-HIV-1 activity of 5-azacytidine is antagonized by inhibitors of ribonucleotide reductase; 5) the anti-HIV-1 activity of ribonucleotide reductase inhibitors are potentiated by 5,6-dihydro-5-aza-2’-deoxycytidine. The studies conducted in this dissertation advance current understanding of the determinants for retroviral mutagenesis, the mechanisms by which small molecules promote mutations in HIV-1, and approaches for using combinations of small molecules to reduce viral infectivity by enhancing the mutagenesis of HIV-1. Supplementary data (figures, tables, and spreadsheets) associated with this thesis are available online.