Viral rebound and emergence of drug resistance in the absence of viral load testing: a randomized comparison between zidovudine-lamivudine plus Nevirapine and zidovudine-lamivudine plus Abacavir.

BACKGROUND: We investigated virological response and the emergence of resistance in the Nevirapine or Abacavir (NORA) substudy of the Development of Antiretroviral Treatment in Africa (DART) trial. METHODS: Six hundred symptomatic antiretroviral-naive human immunodeficiency virus (HIV)-infected adults (CD4 cell count, <200 cells/mm(3)) from 2 Ugandan centers were randomized to receive zidovudine-lamivudine plus abacavir or nevirapine. Virology was performed retrospectively on stored plasma samples at selected time points. In patients with HIV RNA levels >1000 copies/mL, the residual activity of therapy was calculated as the reduction in HIV RNA level, compared with baseline. RESULTS: Overall, HIV RNA levels were lower in the nevirapine group than in the abacavir group at 24 and 48 weeks (P < .001), although no differences were observed at weeks 4 and 12. Virological responses were similar in the 2 treatment groups for baseline HIV RNA level <100,000 copies/mL. The mean residual activity at week 48 was higher for abacavir in the presence of the typically observed resistance pattern of thymidine analogue mutations (TAMs) and M184V (1.47 log(10) copies/mL) than for nevirapine with M184V and nonnucleoside reverse-transcriptase inhibitor mutations, whether accompanied by TAMs (0.96 log(10) copies/mL) or not (1.18 log(10) copies/mL). CONCLUSIONS: There was more extensive genotypic resistance in both treatment groups than is generally seen in resource-rich settings. However, significant residual activity was observed among patients with virological failure, particularly those receiving zidovudine-lamivudine plus abacavir.

Evolution of drug resistance during 48 weeks of zidovudine/lamivudine/tenofovir in the absence of real-time viral load monitoring.

OBJECTIVES: To describe the resistance mutations selected by a first-line regimen of zidovudine/lamivudine/tenofovir in the absence of real-time viral load monitoring. DESIGN: A substudy of 300 participants from the Development of Antiretroviral Therapy in Africa trial in Uganda and Zimbabwe, which compared managing antiretroviral therapy with and without laboratory monitoring. METHODS: Stored plasma samples from selected time points were assayed retrospectively for HIV-1 RNA. The pol gene in all baseline samples and those with HIV RNA >1000 copies per milliliter at weeks 24 and 48 were sequenced. RESULTS: The proportion with HIV RNA >1000 copies per milliliter increased from 15% at 24 weeks to 24% at 48 weeks. Eighteen of 31 (58%) genotyped samples at 24 weeks had ≥ 1 major nucleoside reverse transcriptase inhibitor-associated mutations compared with 41 of 47 (87%) at 48 weeks. Excluding 1 nonadherent patient, a mean of 2.0 (95% confidence interval: 1.3 to 2.8) thymidine analogue mutations (TAMs) developed between weeks 24 and 48 among 14 patients with HIV RNA >1000 copies per milliliter at both time points. K65R was detected in 8 of 63 (13%) patients and was negatively associated with number of TAMs (P = 0.01) but not viral subtype (P = 0.30). CONCLUSIONS: A high rate of acquisition of TAMs, but not of K65R, among patients with prolonged viraemia was observed. However, most patients were virologically suppressed at 48 weeks, and long-term clinical and immunological outcomes in the Development of Antiretroviral Therapy in Africa trial were favorable.

In vivo HIV-1 compartmentalisation: drug resistance-associated mutation distribution.

Four patients who had received highly active antiretroviral therapy (HAART), and had postmortem samples stored, were tested for genotypic resistance using consensus sequencing. One patient was further investigated using single-copy sequencing. Patients 1, 3, and 4 showed a relatively uniform distribution of resistance-associated mutations, with only a small number (one to three) of protease mutations detectable. Patient 2 had a number of detectable mutations (four to eight, depending on the tissue) with similar distributions between the tissues. The exception was viruses detected in the esophagus, which were more diverse. Plasma was a moderately representative tissue of the viruses circulating in these individuals. However, some mutations detectable in some tissues were not seen in plasma (e.g., M46I and D30N in the protease). Single-copy sequencing revealed a wide distribution of quasi-species and a number of defective viruses in the proviral DNA and RNA. This study supports the concept that a wide variety of quasi-species circulate in each individual and that there may be viruses evolving independently in different body compartments.