The treatment of HIV infection in Latvia by using highly active antiretroviral therapy (HAART) was started in 1996. The prevalence and tendencies of HIV drug resistance among treated and treatment-naive patients in Latvia in the years 2006-2007 were evaluated in this study. Data of HIV genotyping, performed in 132 HIV-1 infected during years 2006-2007 by TRUGENE HIV-1 genotyping assay (BayerHealthCare-diagnostics) are included in the study.Analysis of data showed that in the group of treatment-naive individuals majority carried wild type virus. Prevalence of resistance-associated mutations (RAMs) in the treatment-naive group according to IAS list was 28%. In most cases it was NRTI mutation A62V that is associated with multinucleoside resistance caused by Q151M, its effect in the absence of Q151M is not known. By many authors A62V is supposed to be a result of polymorphism in RT gene and is excluded from the list of resistance mutations. High prevalence of A62V is typical for HIV-1 subtype A. As majority of treatment-naive cases (89%) in this study were with HIV-1 subtypes A or AE, we excluded A62V mutation and estimated RAMs prevalence in group of treatment-naive HIV-infected individuals as 7%. Minor PI mutations were not included in analyses. In Europe published rates generally very between 5% and 15%.In the group of treatment-experienced HIV infected people 25/75 were with HIV-1 subtype B, the rest part -with non-B subtypes: A/AE (35/75), CRF -01AE (7/75), B/AE (4/75) and others. In treatment-experienced patients RAMs prevalence was estimated as 58.6%. Most frequently RAMs were found for nucleoside reverse trans criptase inhibitors (NRTI) (49.3%) followed by non-nucleoside reverse transcriptase inhibitors (NNRTI) (22.6%) and protease inhibitors (PI) (16%).In the group of NRTI mutations M184V (26/75; 34.6%), A62V (12/75; 16.0%) and T215Y (8/75; 10.6%), in NNRTI mutations K103N (10/75; 13.3%), G190S (6/75; 8.0%), in PI group mutations L90M (6/75; 8.0%) and M461/L (6/75; 8.0%) occurred most frequently.The following drug susceptibility was predicted according to the Trugen expert interpretations: in 33/75 (44%) patients no evidence of resistance, in 21/75 (28%) patients resistance to 1 drug class (NRTI -16/75 NNRTI -4/75, PI -1/75), in 17 patients (22.6%) resistance to 2 drug classes (NRTI+NNRTI -9/75, NRTI+PI -7/75, NNRTI+PI -1/75) and in 3/75 (4%) patients resistance to all 3 classes of drugs (NRTI+NNRTI+PI).We conclude, that prevalence of RAMs in treatment-naive HIV infected persons in Latvia is comparable with prevalence in Europe. The origin of predominated mutation A62V associated with NRTI at present is not clear. In more than half of treated HIV infected patients HIV resistance to at least one HAART class was predicted. NRTI+NNRTI 12.0% no evidence of resistance 44.0% NRTI 21.3% NRTI+PI 9.3% 3 classes 4.0% NNRTI+PI 1.3% PI 1.3% NNRTI 5.3%

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