All patients received ZDV + ddI, d4T + 3TC, or ZDV + 3TC (after drug substitution for toxicity) as the 2-NRTI backbone. NRTI resistance mutations were detected in 17 participants. The most common was M184V, found in 14 of 40 (35.0%) 3TC recipients. Four participants had at least 1 thymidine-associated mutation—2 recipients of ZDV + ddI had D67N + K70R, another ZDV + ddI recipient had K70R alone. One participant who received EFV + d4T + 3TC had 4 RT mutations (A62V, K65R, M184V, and K219E) in addition to 2 NNRTI-associated mutations.
No PR resistance mutations were detected in the 38 LPV/r recipients. Six of these individuals also received EFV before rebound. Of the 32 individuals who never received EFV, 6 (18.8%, CI: 7.2% to 36.4%) had NRTI-associated mutations; 5 had M184V and 1 with K70R.
Seventeen of 36 EFV recipients (47.2%) had NNRTI resistance mutations. K103N was the most commonly detected in 9 (25%) participants, V106M in 6 (16.7%), and G190S/A ± Y188C/L in 6 (16.7%). No Y181C mutation was detected. DRM to both NRTI and NNRTI were found in 11 of 36 (30.5%) of EFV recipients, with the combination of M184V and K103N being most prevalent. The N348I mutation of the connection domain of RT was detected in 2 participants; both also had NNRTI mutations. There was no statistical difference in the frequency of NRTI mutations between the group exposed to EFV and those never exposed to EFV (P = 0.4).
Comparison Between Participants With and Those Without RT Mutations
There was no statistically significant difference in the following baseline characteristics between the groups with and without RT mutations: age, hemoglobin, CD4 count, HIV RNA, BMI, gender, proportion with WHO Stage 3 or 4 diseases, and the time to viral rebound. Those with RT mutations had a smaller increase in CD4 counts (+139 vs. +155 cells/mm3, P = 0.05). The HIV RNA levels at rebound were similar between the 2 groups (3.9 vs. 3.6 log10 copies/mL, P = 0.25).
Our study is amongst the largest HIV cohort in South Africa who started PI/r as initial cART to date. Our data confirmed those of other studies that PI-associated DRM is much less common than NNRTI-associated or NRTI-associated DRM at failure. Compared with other reports from sub-Saharan Africa, a smaller proportion of our participants had DRM at confirmed rebound viremia. This could be due to only a quarter of our population being randomized to a regimen containing both 3TC and an NNRTI, the drugs most frequently associated with DRM at failure11; whereas in other cohorts, 94%–100% of patients were on these RT inhibitors in their first cART.5–7 As seen in other studies, M184V and the NNRTI-associated mutations were most prevalent in our cohort.5,6
Because our participants were enrolled in a randomized control trial, they were evaluated on a relatively frequent follow-up schedule of monthly for the first 3 months, then every 3 months thereafter. We performed genotype testing at viral rebound confirmed by the second viremia sample, a time point within 3 months of the first detection of viremia of >1000 copies per milliliter. As a consequence, patients were viremic on therapy for a relatively short period, which may explain the fewer DRM detected. Greater accumulation of DRM, especially NRTI-associated mutations, occurs the longer one remains on a failing regimen.5 In a Malawi study where treatment failure was not determined virologically, but clinically or immunologically, 93% of participants with viremia (on stored samples) had NNRTI mutations, 81% had M184V, and 56% harbored at least 1 thymidine-associated mutation along with M184V and NNRTI mutations.16
Two patients in our study developed the connection domain mutation N348I, identified previously as contributing to substantial increase in AZT resistance, including patients with nonsubtype B infection.17 N348I may emerge on NRTI or NNRTI exposure, both of our patients received EFV. The detection of N348I in patients with DRM resistance suggests that sequencing programs that include this portion of RT will be useful in deriving a comprehensive drug resistance evaluation.
The pre-cART samples of those with DRM at failure all had wild-type virus, suggesting that pretreatment transmitted drug resistance was not a reason for failure. However, as more patients in South Africa receive first-line NNRTI-based regimens and failure with NNRTI resistance increases, transmitted resistance will likely increase, which has already been reported in several African countries.18,19
Reasons for rebound viremia in our cohort are uncertain, but nonadherence most likely plays a key role. Adherence assessments were solely based on participants' adherence reports, which have limitations. Measures to improve adherence to cART, like continuous adherence support, using coformulations, and once-daily dosing of cART, may reduce virologic failure with or without DRM.
Our substudy has a few limitations. First, we only selected patients who demonstrated viral suppression at 6 months and then had viral rebound, to eliminate those who may have had transmitted HIV drug resistance at baseline. This is not representative of all the patients who either did not respond or fail to achieve viral suppression until a later time point. Second, as genotype testing was done on the second rebound samples, we cannot prove that PI-resistance mutations did not emerge at a later time point although the patients were viremic and continued to receive LPV/r. Despite these limitations, our findings are important to note as they confirm data from developed countries showing that PI/r has a greater genetic barrier to resistance than NNRTI-based regimens.
In many settings in sub-Saharan Africa, viral load testing is not available and antiretroviral failure is only recognized by CD4 decline or clinical progression. Based on this study and others, virologic failure with DRM precedes clinical or immunologic failure. Phidisa II utilized a relatively frequent viral RNA determination schedule, permitting early detection of rebound viremia. Development of affordable point of care viral load tests in resource-limited setting is critical to allow for early identification and management of treatment failure.
In conclusion, this study confirms the risk of selection of NNRTI and M184V mutations in patients who received EFV and 3TC in first-line cART. Phidisa II represents the largest cohort of adults who received PI/r as first-line cART in South Africa. In this subgroup analysis, no PI resistance mutations were detected at failure, demonstrating that a PI/r-containing regimen maybe a potential ART option in Africa. The relatively high cost of PI/r and lack of coformulations with other ARV drug classes, however, precludes their use as first-line regimen in this population. The absence of PI DRM noted here suggests, however, that the increased cost may be offset by durable efficacy of these antivirals. More affordable generic PI/r and coformulations available for initial cART options may reduce development of DRM and transmitted drug-resistant HIV in Africa.
We wish to express our gratitude to Phidisa II study participants, South African Military Health Service leadership and Units, Phidisa Executive Committee, and Phidisa staff.
1. National Department of Health SA. National Antiretroviral Treatment Guidelines. 2004 Pretoria, South Africa Jacana:1–93
2. Department of Health RSA. The South African Antiretroviral Treatment Guidelines. 2010 Pretoria, South Africa Department of Health RSA:1–8
3. Barth RE, Wensing AM, Tempelman HA, et al. Rapid accumulation of nonnucleoside reverse transcriptase inhibitor-associated resistance: evidence of transmitted resistance in rural South Africa. AIDS. 2008;22:2210–2212
4. El-Khatib Z, Ekstrom AM, Ledwaba J, et al. Viremia and drug resistance among HIV-1 patients on antiretroviral treatment: a cross-sectional study in Soweto, South Africa. AIDS. 2010;24:1679–1687
5. Hoffmann CJ, Charalambous S, Sim J, et al. Viremia, resuppression, and time to resistance in human immunodeficiency virus (HIV) subtype C during first-line antiretroviral therapy in South Africa. Clin Infect Dis. 2009;49:1928–1935
6. Wallis CL, Mellors JW, Venter WD, et al. Varied patterns of HIV-1 drug resistance on failing first-line antiretroviral therapy in South Africa. J Acquir Immune Defic Syndr. 2010;53:480–484
7. Marconi VC, Sunpath H, Lu Z, et al. Prevalence of HIV-1 drug resistance after failure of a first highly active antiretroviral therapy regimen in KwaZulu Natal, South Africa. Clin Infect Dis. 2008;46:1589–1597
8. Pillay V, Pillay C, Kantor R, et al. HIV type 1 subtype C drug resistance among pediatric and adult South African patients failing antiretroviral therapy. AIDS Res Hum Retroviruses. 2008;24:1449–1454
9. Orrell C, Walensky RP, Losina E, et al. HIV type-1 clade C resistance genotypes in treatment-naive patients and after first virological failure in a large community antiretroviral therapy programme. Antivir Ther. 2009;14:523–531
11. Hirsch MS, Gunthard HF, Schapiro JM, et al. Antiretroviral drug resistance testing in adult HIV-1 infection: 2008 recommendations of an International AIDS Society-USA panel. Clin Infect Dis. 2008;47:266–285
12. Ratsela A, Polis M, Dhlomo S, et al. A randomized factorial trial comparing 4 treatment regimens in treatment-naive HIV-infected persons with AIDS and/or a CD4 cell count <200 cells/μL in South Africa. J Infect Dis. 2010;202:1529–1537
13. Pillay V, Ledwaba J, Hunt G, et al. Antiretroviral drug resistance surveillance among drug-naive HIV-1-infected individuals in Gauteng Province, South Africa in 2002 and 2004. Antivir Ther. 2008;13(suppl 2):101–107
14. Johnson VA, Brun-Vezinet F, Clotet B, et al. Update of the drug resistance mutations in HIV-1: December 2009. Top HIV Med. 2009;17:138–145
15. Liu TF, Shafer RW. Web resources for HIV type 1 genotypic-resistance test interpretation. Clin Infect Dis. 2006;42:1608–1618
16. Hosseinipour MC, van Oosterhout JJ, Weigel R, et al. The public health approach to identify antiretroviral therapy failure: high-level nucleoside reverse transcriptase inhibitor resistance among Malawians failing first-line antiretroviral therapy. AIDS. 2009;23:1127–1134
17. Delviks-Frankenberry KA, Nikolenko GN, Boyer PL, et al. HIV-1 reverse transcriptase connection subdomain mutations reduce template RNA degradation and enhance AZT excision. Proc Natl Acad Sci U S A. 2008;105:10943–10948
18. Lihana RW, Khamadi SA, Lubano K, et al. HIV type 1 subtype diversity and drug resistance among HIV type 1-infected Kenyan patients initiating antiretroviral therapy. AIDS Res Hum Retroviruses. 2009;25:1211–1217
19. Price MA, Wallis CL, Lakhi S, et al. Transmitted HIV type 1 drug resistance among individuals with recent HIV infection in East and Southern Africa. AIDS Res Hum Retroviruses. 2011;27:5–12
Keywords:© 2011 Lippincott Williams & Wilkins, Inc.
antiretroviral naïve; genotypic resistance; HIV; nonnucleoside reverse transcriptase inhibitors; protease inhibitors; South Africa