Resistance-Associated Mutation Prevalence According to Subtypes B and Non-B of HIV Type 1 in Antiretroviral-Experienced Patients in Minas Gerais, Brazil Mateus R. Westin, 1 Fernando M. Biscione, 1 Marise Fonseca, 1 Monique Ordones, 1 Mirian Rodrigues, 1 Dirceu B. Greco, 2 and Unai Tupinambas 2 Abstract The emergence of resistance-associated mutations to the antiretroviral agents and the genetic variability of HIV-1 impose challenges to therapeutic success. We report the results of genotype testing assays performed between 2002 and 2006 in 240 antiretroviral-experienced patients followed up in an HIV reference center in Brazil. Drug resistance mutations and viral subtypes were assessed through the algorithms from the Brazilian Genotyping Network (RENAGENO—Brazil) and from Stanford University. Mutation 184VI was the most prevalent (70%) and the thymidine analogue mutations that appeared most frequently were 215FY, 41L, 67N, and 210W, in this order. Among nonnucleoside reverse transcriptase inhibitor mutations, 103NS (32.5%) stood out. HIV subtype B was identified in 184 patients (76.7%). A significant increasing trend in the prevalence of non-B subtypes was observed during the study period ( p = 0.004). The main differences in prevalence of mutations among HIV-1 subtypes were related to viral protease, with 20MRI, 36I, and 89IMT more prevalent among non-B subtypes, and 84V, 10FR, 63P, 71LTV, and 77I more common in subtype B ( p < 0.05). Most mutations to etravirine had a prevalence lower than 10%, but at least one mutation to this drug was observed in 45% of the patients. In only 11 patients (4.6%) three mutations to etravirine were verified. Regional surveillance of the resistance profile and HIV-1 subtypes is crucial in the context of public health, to prevent the transmission of resistant strains and to guide the introduction of new drugs in a specific population. Introduction W ith the advent of highly active antiretroviral thera- py (HAART) for the treatment of HIV infection, there has been an expressive reduction in AIDS-related morbidity and mortality in countries with extensive access to treatment. 1,2 The Brazilian Ministry of Health provides universal free of charge access to antiretroviral drugs to all who need them. 3 However, therapeutic success is threatened by several factors, such as inadequate adherence to the treatment, drug toxicity, subin- hibitory concentrations in viral reservoirs, and HIV-1 genetic variability, which may lead to resistance to antiretroviral drugs. HIV-1 variant strains with resistance mutations to all classes of available antiretrovirals have been reported. 4 The emergence of resistance to antiretroviral drugs should be understood as the cause and effect of virological and therapeutic failure. 5 In 2001, the Brazilian Genotyping Network (RENAGENO) 3 was established with the main objective of providing clini- cians with decision-making tools to guide therapeutic rescue of antiretroviral-experienced patients. RENAGENO is also a national network that monitors the prevalence of viral drug resistance and HIV-1 genetic variability across Brazilian states. Our service is a member of this program. In this study, we sought to analyze the prevalence of antiretroviral drug resistance mutations by HIV-1 subtypes B and non-B in pa- tients failing antiretroviral therapy for whom information related to previous antiretroviral exposure was available and who had a genotype testing assay between 2002 and 2006 at a HIV reference center in Minas Gerais, Brazil. Material and Methods In this study, we analyze the results of genotype testing assays performed between January 2002 and December 2006 on HIV-infected patients aged 18 years or older in instances of failing HAART, followed at the Training and Reference 1 Infectious Diseases and Tropical Medicine Post-Graduate Course, School of Medicine, Federal University of Minas Gerais (UFMG), Minas Gerais, Brazil. 2 Training and Reference Center for Infectious and Parasitic Diseases (CTR/DIP), Hospital das Clinicas University Hospital (UFMG) and Belo Horizonte Health Secretary, Minas Gerais, Brazil. AIDS RESEARCH AND HUMAN RETROVIRUSES Volume 27, Number 9, 2011 ª Mary Ann Liebert, Inc. DOI: 10.1089/aid.2010.0260 981