Sequence Note Low Prevalence of Drug Resistance Transmitted Virus in HIV Type 1-Infected ARV-Naive Patients in Cambodia Janin Nouhin, 1 Sopheak Ngin, 1 P. Regis Martin, 2 Olivier Marcy, 3 Leangsim Kruy, 4 Frederic Ariey, 5 Martine Peeters, 6 Marie-Laure Chaix, 7 Ahidjo Ayouba, 6 and Eric Nerrienet 1 Abstract Between November 2006 and June 2007, HIV-1 reverse transcriptase (RT) and protease (PR) genes of 67 ARV- naive Cambodian patients were amplified and sequenced. At inclusion, the median age and duration of HIV infection were 28 and 1.1 years, respectively. The median CD4 and HIV-1 RNA were 611 cells=ml [IQR: 525–759] and 4.0 log 10 copies=ml [IQR: 3.4–4.6]. Among 67 HIV-1 strains, 95.5% were CRF 01_AE viruses (n ¼ 64) whereas three clustered with subtype B. RT analysis indicated that only 1 patient out of 67, presenting K103N and M184V mutations, was resistant to NVP=EFV and 3TC=FTC. No primary resistance to protease inhibitors was detected in 59 amplified protease genes. The 1.49% (IC 95%: 0.04–8.04%) prevalence of transmitted drug-resistant strains in drug-naive patients was low in our study. Surveys of drug-resistant transmitted viruses should be regularly performed regarding the increasing access to HAART in Cambodia. A ccess to antiretroviral (ARV) therapy in resource- limited settings has increased dramatically in the last few years, with over 1.3 million patients currently estimated to be receiving treatment (http:==www.who.int=hiv=progre port2006_en.pdf ). Increased access to antiretroviral drugs has implications for the quality of life of people living with HIV=AIDS as well as prevention of horizontal and vertical transmission. However, incomplete adherence to ARV therapy has been documented to be a primary contributing factor for treatment failure and the emergence and trans- mission of ARV-resistant virus strains. 1 In the context of increasing access to ARV drugs in resource-limited coun- tries, studies addressing the prevalence of primary muta- tions associated with ARV resistance among treatment-naive individuals infected with HIV-1 are therefore of major interest. Cambodia initiated a program offering ARV treatment at no cost to persons with HIV infection in 2001. In 2003, with the support of NGOs and the national program, hundreds of patients in cohorts accessed ARV treatment. 2,3 The first line regimen included a combination of two nucleoside reverse transcriptase inhibitors (NRTI), stavudine (D4T) or zido- vudine (ZDV) plus lamivudine (3TC), and one nonnucleoside reverse transcriptase inhibitor (NNRTI), nevirapine (NVP) or efavirenz (EFV). In 2005, WHO=UNAIDS estimated that 35,000 HIV Cam- bodian patients needed ARV therapy (http:==www.who.int= hiv=HIVCP_KHM.pdf). The same year, the National Center for HIV=AIDS, Dermatology and STD (NCHADS) reported that Cambodia reached the World Health Organization (WHO) ‘‘3 by 5’’ objective as 12,355 patients were on HAART. According to NCHADS, the number of patients on HAART reached 20,131 in 2006 and nearly 30,000 at the end of 2007. Therefore, the number of patients on HAART has increased exponentially in the past 5 years in Cambodia. A baseline study conducted between February 2003 and December 2004 among 144 ARV-naive patients (22 sero- converters and 124 pregnant women) showed a 4.9% (7=144) prevalence of transmitted resistant HIV-1. 4 Since that period, HAART became more widely available in the country. Therefore, it was important to repeat the HIV Drug Resistance (DR) survey among the ARV-naive population to further appreciate the evolution of the prevalence of resistance in ARV-naive patients. 1 HIV=Hepatitis Laboratory, Pasteur Institute of Cambodia, 2 Me ´decins du monde, 3 French Red Cross, 4 Calmette Hospital, Maternity Ward, and 5 Molecular Epidemiology Unit, Pasteur Institute of Cambodia, Phnom Penh, Cambodia. 6 UMR145, IRD and University of Montpellier 1, Montpellier, France. 7 Universite ´ Paris-Descartes, EA 3620, AP-HP, Virologie, CHU Necker-Enfants Malades, Paris, France. AIDS RESEARCH AND HUMAN RETROVIRUSES Volume 25, Number 5, 2009 ª Mary Ann Liebert, Inc. DOI: 10.1089=aid.2008.0305 543