RESUMEN
We investigated the occurrence of HIV-1 antiretroviral resistance in individuals failing to respond to highly active antiretroviral therapy (HAART) attended by RENAGENO from 2001-2004. One hundred and seventeen patients were selected for this study; their plasma viral RNA was extracted and the PR and RT genes sequenced to examine subtype, genetic polymorphisms and mutations associated with resistance to antiretroviral drugs. HIV-1 sequence analysis showed that 86/100 (86 percent) were infected with subtype B, 7/100 (7 percent) with subtype F and 7/100 (7 percent) with RT/PR hybrid forms (2 D/B, 2 F/B, 2 B/F and 1 D/F). In 14 (12 percent) of the samples, the subtype was not determined. The prevalence of resistance mutations was high (93.1 percent), mainly in the RT gene. The most prevalent resistance mutations were: M184V (60.7 percent), T215Y (49.6 percent) and M41L (46.7 percent) in the RT gene and L90M (19.6 percent), M46I (16.2 percent) and D30N (12.8 percent) in the PR gene. The frequency of resistance mutations tended to increase from the first to the second therapeutic scheme failure (p=0.079); but it stabilized after subsequent failures (p=0.875). Our finding of a high frequency of drug resistant HIV-1 samples supports the need for continuous genotypic monitoring of patients failing HAART.