TO THE EDITOR—Controversy exists about whether human immunodeficiency virus type 1 (HIV-1) replication persists in patients receiving effective antiretroviral therapy. Residual viremia can often be detected in such patients by sensitive quantitative polymerase chain reaction assays, but the source of this viremia is unknown [1]. Possibilities include ongoing cycles of HIV-1 replication, long-lived HIV-1–infected cells that continuously or intermittently produce virus, or both. If residual plasma viremia is derived from ongoing HIV-1 replication, intensification of an effective regimen with another potent antiretroviral drug should lower viremia. Such treatment intensification studies have been conducted with different classes of antiretroviral agents (nucleoside reverse-transcriptase inhibitors, nonnucleoside reverse-transcriptase inhibitors, protease inhibitors, and the integrase inhibitor raltegravir), and none has shown reduction in residual viremia [2–6]. However, Buzon et al [7] showed transient increases in episomal (2-Long Terminal Repeat [2-LTR] circle) HIV-1 DNA levels in 13 of 45 patients after raltegravir intensification, suggesting raltegravir blocked ongoing HIV-1 replication without affecting plasma viremia. Moreover, Yukl et al [5] showed reductions in unspliced HIV-1 RNA levels in CD4+ T cells from the terminal ileum in 5 of 7 patients after raltegravir intensification. To provide additional insight into the effects of raltegravir intensification, we analyzed total HIV-1 DNA and 2-LTR circle levels in peripheral blood mononuclear cells (PBMCs) obtained before and after 28 days of raltegravir intensification from a study of 10 patients, published by McMahon et al [4] in Clinical Infectious Diseases, that showed no effect of raltegravir on residual viremia. Total cellular DNA was extracted (Dynabeads) from 5 × 106 PBMCs and assayed for total HIV-1 DNA and 2-LTR HIV-1 DNA circle levels by quantitative, real-time polymerase chain reaction (limit of detection, 15 copies per 106 PBMCs for both assays).
HIV-1 DNA was detected in all subjects, ranging from 154 to 6,879 copies per 106 PBMCs and showing no consistent change between baseline (before intensification) and 28 days after intensification (Table 1). Levels of 2-LTR circles were detected in 3 of 10 patients at baseline, but only 2 still tested positive after intensification (range, 19–638 copies per 106 PBMCs). There was no increase in 2-LTR circles in these 2 patients after raltegravir intensification. There was also no change in the ratio of 2-LTR circles to total HIV-1 DNA level after intensification. Finally, none of the 7 patients who were negative for 2-LTR circles at baseline become positive after intensification.
Table 1.
Quantification of HIV-1 DNA and 2 Long Terminal Repeat Circles in Peripheral Blood Mononuclear Cells
| Patient ID, visit or study week | Total HIV DNA level, copies per 106 cellsa | 2-LTR circles, copies per106 cellsa | Ratio 2-LTR per HIV DNA |
| 1 | |||
| Entry | 1,570 | <15 | … |
| Week 4 | 1,805 | <15 | … |
| 2 | |||
| Entry | 578 | 19 | 0.03 |
| Week 4 | 680 | <15 | … |
| 3 | |||
| Entry | 1,098 | <15 | … |
| Week 4 | 728 | <15 | … |
| 4 | |||
| Entry | 4,517 | <15 | … |
| Week 4 | 2,886 | <15 | … |
| 5 | |||
| Entry | 3,760 | 308 | 0.08 |
| Week 4 | 2,889 | 168 | 0.06 |
| 6 | |||
| Entry | 3,560 | <15 | … |
| Week 4 | 6,879 | <15 | … |
| 7 | |||
| Entry | 1,862 | 638 | 0.34 |
| Week 4 | 1,106 | 249 | 0.23 |
| 8 | |||
| Entry | 2,074 | <15 | … |
| Week 4 | 2,430 | <15 | … |
| 9 | |||
| Entry | 409 | <15 | … |
| Week 4 | 605 | <15 | … |
| 10 | |||
| Entry | 618 | <15 | … |
| Week 4 | 154 | <15 | … |
Abbreviation: 2-LTR, 2-Long Terminal Repeat.
a Normalized for total cellular DNA quantified spectrophotometrically [A260].
These results do not support an effect of raltegravir intensification on 2-LTR HIV-1 DNA circles, which is contrary to the report by Buzon et al [7] that showed an increase in 2-LTR circles in 29% of patients 2–4 weeks after raltegravir intensification. Differences in patient characteristics, sampling time, antiretroviral regimens, duration of HIV-1 RNA suppression, and sample size may be responsible for the discrepancies between the 2 studies. Nevertheless, most evidence reported to date, including the results presented here, refute ongoing HIV-1 replication in patients receiving effective antiretroviral therapy as the source of residual viremia [2, 5, 6]. Additional studies are needed, however, to assess the impact of treatment intensification on HIV-1 replication in tissue compartments.
Notes
Acknowledgments.
We thank the patients who participated in the study.
Financial support.
This work was supported by a grant from the National Cancer Institute (SAIC contract 25XS119).
Potential conflicts of interest.
J. W. M. is a consultant for Gilead, Merck, and RFS Pharma and owns shares in RFS Pharma. All other authors report no potential conflicts.
All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.
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