Prevalence of primary antiretroviral resistance among HIV infected patients in Chile

Background: The main cause of virological failure during AIDS treatment is the resistance to antiretroviral medications (ARV). Aim: To search for mutations associated with ARV resistance in recently HIV-1 infected patients naive to treatment, in Chile. Material and Methods: Patients over 18 years old with HIV-1 infection, naive to anti-retroviral drugs before the study were included. Patients with CD4 cell counts less than 200 cells/mm(3), viral load below 2.000 copies/mL or any condition indicative of advanced AIDS were excluded. Criteria for diagnosis of recent infection (< 18 months) were a previous negative test for HIV antibodies or a history of an acute retroviral syndrome in the past 18 months. Resistance to drugs was analyzed using the TRUGENE (TM) HIV-1 assay from Bayer and the OpenGene DNA sequencing system. Results: Ninety nine percent of patients had at least one mutation, 27% had 4 or more mutations, but high level resistance to ARV was found only in 2.7% of cases. Point mutations for non nucleoside reverse transcriptase inhibitors (NNRTI) were detected in 4.1% of cases (K103N in 1 patient, V179D in 2 patients), for nucleoside reverse transcriptase inhibitors (NRTI) in 8.1% of cases (T215S in 1 patient, V118I in 4 patients, M41L in 1 patient) and for protease inhibitors (PI) in 1.3% of cases. All mutations detected in the protease gene were secondary. Of these, the most common were L63P/T (38 patients), L10I/V (27 patients) and V77I (26 patients). Resistance to two or more antiretroviral classes was not detected. Conclusions: This study supports that, by now, primary resistance has a low prevalence in Chile. Therefore, a genotyping test before starting anti retroviral therapy is not necessary. (Rev Med Chile 2010; 138: 669-676).