title: Differential drug resistance acquisition in HIV-1 of subtypes B and C.
abstract: BACKGROUND
  Subtype C is the most prevalent HIV-1 subtype in the world, mainly in countries with the highest HIV prevalence. However, few studies have evaluated the impact of antiretroviral therapy on this subtype. In southern Brazil, the first developing country to offer free and universal treatment, subtypes B and C co-circulate with equal prevalence, allowing for an extensive evaluation of this issue.
  
  
  RESULTS
  Viral RNA of 160 HIV-1+ patients was extracted, and the protease and reverse transcriptase genes were sequenced, subtyped and analyzed for ARV mutations. Sequences were grouped by subtype, and matched to type (PI, NRTI and NNRTI) and time of ARV exposure. Statistical analyses were performed to compare differences in the frequency of ARV-associated mutations. There were no significant differences in time of treatment between subtypes B and C groups, although they showed distinct proportions of resistant strains at different intervals for two of three ARV classes. For PI, 26% of subtype B strains were resistant, compared to only 8% in subtype C (p = 0.0288, Fisher's exact test). For NRTI, 54% of subtype B strains were resistant versus 23% of subtype C (p = 0.0012). Differences were significant from 4 years of exposure, and remained so until the last time point analyzed. The differences observed between both subtypes were independent of time under rebound viremia in cases of virologic failure and of the number of HAART regimens used by treated patients.
  
  
  CONCLUSIONS
  Our results pointed out to a lower rate of accumulation of mutations conferring resistance to ARV in subtype C than in subtype B. These findings are of crucial importance for current initiatives of ARV therapy roll-out in developing countries, where subtype is C prevalent.
authors: Departamento de Genética, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Esmeralda A J M
authors: EA
authors: Soares
authors: André F A
authors: AF
authors: Santos
authors: Thatiana M
authors: TM
authors: Sousa
authors: Eduardo
authors: E
authors: Sprinz
authors: Ana M B
authors: AM
authors: Martinez
authors: Jussara
authors: J
authors: Silveira
authors: Amilcar
authors: A
authors: Tanuri
authors: Marcelo A
authors: MA
authors: Soares
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000627:therapeutic use*; D023241:Antiretroviral Therapy, Highly Active; D001938:Brazil; D024882:Drug Resistance, Viral; D005260:Female; D015658:HIV Infections / Q000188:drug therapy*; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D019562:Viral Load; D014766:Viremia
chemical_list: D019380:Anti-HIV Agents; D012367:RNA, Viral
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