Genotype and phenotype resistance: an overview

Abstract

Drug resistance is a major factor contributing to the failure of antiretroviral therapy. The rapid turnover of the human immunodeficiency virus type 1 (HIV-1) and the error-prone reverse transcriptase both contribute to the extensive emergence of resistant variants. The understanding of resistance and cross-resistance patterns is essential for the appropriate selection of treatment regimens for HIV-infected individuals. Although genotypic and phenotypic assays of drug resistance are not currently recommended for routine use, preliminary data has emphasized the role of resistance testing in guiding the choice of initial antiretroviral therapy, in explaining reasons for failure, and in selecting subsequent therapy for patients failing their current regimen. This article reviews the advantages and disadvantages of currently available resistance assays, as well as mechanisms and patterns of resistance and cross-resistance.