An overview of the human immunodeficiency virus featuring laboratory testing for drug resistance.

1. Emil Scosyrev, MS[⇑][1] 1. is a PhD student in the Epidemiology Program in the Department of Community and Preventive Medicine, School of Medicine and Dentistry, University of Rochester, Rochester NY 1. Address for correspondence: Emil Scosyrev MS, Epidemiology Program, Department of Community and Preventive Medicine, University of Rochester, 601 Elmwood Avenue, Box 644, Rochester NY 14642. (256) 736-4454. emil{at}uab.edu. 1. Describe the main genetic properties of the human immunodeficiency virus (HIV). 2. Describe the major events in the life cycle of HIV. 3. Identify the primary functions of each of the following viral proteins: gp120, gp41, reverse transcriptase, integrase, protease. 4. List the three major stages in the natural course of the HIV infection. 5. Describe the changes in the viral loads and the CD4 counts during the natural course of the HIV disease. 6. List the four FDA-approved classes of antiretroviral drugs and identify the molecular targets of therapy for each class. 7. Describe benefits and limitations of antiretroviral therapy. 8. Describe the mechanisms of resistance in each of the four FDA-approved classes of antiretroviral drugs. 9. List the two fundamental approaches to HIV drug resistance testing. 10. Describe the principles of phenotypic resistance testing and list the main steps of the testing process. 11. Define IC50 and calculate the X-fold reduction in susceptibility using the IC50 values. 12. Describe the principles of sequencing-based genotypic resistance testing and list the main steps of the testing process. 13. Describe the principles of dideoxynucleotide sequencing. 14. Describe the principles and the limitations of hybridization-based resistance assays. 15. Discuss the clinical utility of HIV drug resistance testing. The human immunodeficiency virus (HIV) pandemic is unique in human history in its rapid spread, its persistence, and the depth of its impact. The Joint United Nations Programme on HIV/AIDS (UNAIDS) estimates that approximately 65 million people have been infected with HIV since the beginning of the epidemic. During this time, approximately 25 million people have died from acquired immune deficiency syndrome AIDS.1 HIV-associated morbidity and mortality was substantially reduced during the last decade following the introduction of highly active antiretroviral therapy (HAART). In spite of the striking success of HAART in treating HIV infection, many patients experience treatment failure as genetic changes emerge in the virus leading to drug resistance.2 Laboratory testing for drug resistance in HIV strains is now used in combination with other methods to guide antiretroviral therapy. The purpose of this report is to review the background information on HIV with the focus on the problem of drug resistance and to describe the laboratory methods of testing for drug resistance in HIV strains. Overview This section contains information on biological characteristics of HIV such as taxonomy, genetic properties, structural components, life cycle, pathogenesis, and the virulence factors. Taxonomy Human immunodeficiency virus type 1 (HIV-1) is assigned to genus Lentivirus, subfamily Orthoretrovirinae, family Retroviridae.3 Other human pathogens included in this family are HIV-2 (genus Lentivirus), HTLV-1, and HTLV-2 (genus Deltaretrovirus). Most cases of HIV infection worldwide are caused by HIV-1. The HIV-2 is endemic in West Africa, but cases are also reported in… ABBREVIATIONS: ABC = abacavir; AIDS = acquired immune deficiency syndrome; AZT = zidovudine; ddC = zalcitabine; ddI = didanosine; dNTP = deoxynucleotide triphosphate; ddNTP = dideoxynucleotide triphosphate chain terminator; d4T = stavudine; FDA = Food and Drug Administration; FTC = emtricitabine; HIV = human immunodeficiency virus; HAART = highly active antiretroviral therapy; LTR = long terminal repeats; NNRTI = non-nucleoside reverse transcriptase inhibitor; NRTI = nucleoside analogue reverse transcriptase inhibitor; PI = protease inhibitor; PR = protease; RT = reverse transcriptase; TAM = thymidine analogue mutations; TDF = tenofovir; 3TC = lamivudine. 1. Describe the main genetic properties of the human immunodeficiency virus (HIV). 2. Describe the major events in the life cycle of HIV. 3. Identify the primary functions of each of the following viral proteins: gp120, gp41, reverse transcriptase, integrase, protease. 4. List the three major stages in the natural course of the HIV infection. 5. Describe the changes in the viral loads and the CD4 counts during the natural course of the HIV disease. 6. List the four FDA-approved classes of antiretroviral drugs and identify the molecular targets of therapy for each class. 7. Describe benefits and limitations of antiretroviral therapy. 8. Describe the mechanisms of resistance in each of the four FDA-approved classes of antiretroviral drugs. 9. List the two fundamental approaches to HIV drug resistance testing. 10. Describe the principles of phenotypic resistance testing and list the main steps of the testing process. 11. Define IC50 and calculate the X-fold reduction in susceptibility using the IC50 values. 12. Describe the principles of sequencing-based genotypic resistance testing and list the main steps of the testing process. 13. Describe the principles of dideoxynucleotide sequencing. 14. Describe the principles and the limitations of hybridization-based resistance assays. 15. Discuss the clinical utility of HIV drug resistance testing. [1]: #corresp-1