Short-course raltegravir intensification does not increase 2 long terminal repeat episomal HIV-1 DNA in patients on effective antiretroviral therapy

Prevalence and risk of residual viremia after ART in low- and middle-income countries: A cross-sectional study

ABSTRACT

In order to design effective strategies to eradicate the HIV, an understanding of persistent viral reservoirs is needed. Many studies have demonstrated HIV residual viremia prevalence in high income countries, data from low- and middle-income countries (LMIC) are limited. We assessed the prevalence, and factors associated with residual viremia in people with HIV (PWH), who were virally-suppressed on antiretroviral therapy (ART) in LMIC. We also compared residual viremia prevalence between the LMIC and US.This is a cross-sectional, retrospective study that utilized stored specimen samples from the AIDS clinical trials group (ACTG) studies A5175 and A5208. The last available sample among participants with plasma HIV RNA < 400 copies/mL for ≥3 years were tested by the HIV molecular and monitoring core gag (HMMCgag) single copy assay (SCA). Residual viremia was defined as detectable if ≥1 copy/mL. Spearman's correlation and multivariable stepwise logistic regression were used to assess associations of various factors with SCA.A total of 320 participants, 246 (77%) from LMIC and 74 (23%) from US, were analyzed. Median (IQR) age was 33 (2840) years; baseline CD4 166 (88,230) cells/mm3; HIV RNA 5.0 (4.5, 5.3) log10 copies/mL; duration of viral suppression 3.4 (3.1, 4.0) years and 48% were male. In 85 participants with information available, 53% were subtype C, 42% subtype B and 5% other subtypes. Overall prevalence of residual viremia was 57% [95% CI, 52-63] with 51% [40-63] in US and 59% [53-65] in LMIC. Among participants with detectable SCA, the median (IQR) HIV RNA was 3.8 (2.2, 8.1) copies/mL. The multivariable model conducted in LMIC participants showed that higher baseline HIV RNA was associated with detectable residual RNA (OR 2.9, 95% CI 1.8, 4.6 for every log10 increase, P < .001). After including both US and LMIC in the final model, baseline HIV RNA remained significant. No difference in SCA detestability was found between US and LMIC sites (OR 1.1 [0.6, 2.0], P = .72) after adjusting for baseline RNA and parent study.The prevalence of residual viremia between both groups were not different and more than half of the participants had detectable viremia. Higher baseline HIV RNA was independently associated with residual viremia.

Differences in HIV Markers between Infected Individuals Treated with Different ART Regimens: Implications for the Persistence of Viral Reservoirs

In adherent individuals, antiretroviral therapy (ART) suppresses HIV replication, restores immune function, and prevents the development of AIDS. However, ART is not curative and has to be followed lifelong. Persistence of viral reservoirs forms the major obstacle to an HIV cure. HIV latent reservoirs persist primarily by cell longevity and proliferation, but replenishment by residual virus replication despite ART has been proposed as another potential mechanism of HIV persistence. It is a matter of debate whether different ART regimens are equally potent in suppressing HIV replication. Here, we summarized the current knowledge on the role of ART regimens in HIV persistence, focusing on differences in residual plasma viremia and other virological markers of the HIV reservoir between infected individuals treated with combination ART composed of different antiretroviral drug classes.

Reduction of Immune Activation and Partial Recovery of Staphylococcal Enterotoxin B-Induced Cytokine Production After Switching to an Integrase Strand Transfer Inhibitor-Containing Regimen: Results from an Observational Cohort Study

Background and Objective

Despite integrase strand transfer inhibitor (INSTI)-containing regimens now being considered a preferred option for both initial therapy and switching strategies in virologically suppressed patients, their effects on lymphocyte phenotypes and functions in the course of effective combination antiretroviral therapy (cART) are still unclear. Thus, we investigated the effect of a 24-week elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil fumarate (EVG/c/FTC/TDF) regimen on the T cell compartment and HIV reservoirs in HIV-infected patients switching from a suppressive protease inhibitor-based regimen.

Methods

Thirty HIV-positive patients receiving suppressive tenofovir disoproxil fumarate/emtricitabine (TDF + FTC) (for a median of 5 years) in association with either darunavir/ritonavir (DVR/r) (47%) or atazanavir/ritonavir (ATV/r) (53%) were followed up for 24 weeks after switching to EVG/c/FTC/TDF. At baseline (week 0 [W0]) and after 12 (W12) and 24 (W24) weeks we analyzed HLA-DR (human leukocyte antigen–DR isotype)/CD38/Ki67/CCR7 (C-C chemokine receptor type 7)/CD45RA/CD127/PD-1 (programmed cell death-1) on CD4/CD8, interferon (IFN)-γ/interleukin (IL)-2 after HIV/Staphylococcal enterotoxin B (SEB) exposure (flow cytometry); total, integrated, and unintegrated HIV-DNA; and residual low-level HIV viremia (quantitative polymerase chain reaction [qPCR]).

Results

While EVG/c/FTC/TDF introduction resulted in a stable CD4+ and CD8+ count, residual low-level HIV-RNA viremia, and HIV reservoirs, we observed a significant reduction in both activated CD4+ (p = 0.016) and CD8+ (p = 0.048) T cells, coupled with an increase in IL-2 and IFN-γ release by CD4+ and CD8+ effector memory T cells, and a decrease in cytokine production by terminally differentiated CD8+ T cells following SEB exposure. Furthermore, the magnitude of the reduction of activated HLA-DR + CD38 + CD8+ T cells (r = − 0.63, p = 0.014) inversely correlates with the amount of total HIV-DNA at W24.

Conclusions

Our data show a favorable effect of EVG/c/FTC/TDF switch to preserve immune activation-driven damage to T cell homeostasis, restore the multifunctional properties of effector T cells, and possibly contain cell-associated HIV viral burden in already virologically suppressed patients.

Structure-guided drug design identifies a BRD4-selective small molecule that suppresses HIV

HIV integrates its provirus into the host genome and establishes latent infection. Antiretroviral therapy (ART) can control HIV viremia, but cannot eradicate or cure the virus. Approaches targeting host epigenetic machinery to repress HIV, leading to an aviremic state free of ART, are needed. Bromodomain and extraterminal (BET) family protein BRD4 is an epigenetic reader involved in HIV transcriptional regulation. Using structure-guided drug design, we identified a small molecule (ZL0580) that induced epigenetic suppression of HIV via BRD4. We showed that ZL0580 induced HIV suppression in multiple in vitro and ex vivo cell models. Combination treatment of cells of aviremic HIV-infected individuals with ART and ZL0580 revealed that ZL0580 accelerated HIV suppression during ART and delayed viral rebound after ART cessation. Mechanistically different from the BET/BRD4 pan-inhibitor JQ1, which nonselectively binds to BD1 and BD2 domains of all BET proteins, ZL0580 selectively bound to BD1 domain of BRD4. We further demonstrate that ZL0580 induced HIV suppression by inhibiting Tat transactivation and transcription elongation as well as by inducing repressive chromatin structure at the HIV promoter. Our findings establish a proof of concept for modulation of BRD4 to epigenetically suppress HIV and provide a promising chemical scaffold for the development of probes and/or therapeutic agents for HIV epigenetic silencing.

Expanded cellular clones carrying replication-competent HIV-1 persist, wax, and wane

The latent reservoir for HIV-1 in resting CD4⁺ T cells is a major barrier to cure. Several lines of evidence suggest that the latent reservoir is maintained through cellular proliferation. Analysis of this proliferative process is complicated by the fact that most infected cells carry defective proviruses. Additional complications are that stimuli that drive T cell proliferation can also induce virus production from latently infected cells and productively infected cells have a short in vivo half-life. In this ex vivo study, we show that latently infected cells containing replication-competent HIV-1 can proliferate in response to T cell receptor agonists or cytokines that are known to induce homeostatic proliferation and that this can occur without virus production. Some cells that have proliferated in response to these stimuli can survive for 7 d while retaining the ability to produce virus. This finding supports the hypothesis that both antigen-driven and cytokine-induced proliferation may contribute to the stability of the latent reservoir. Sequencing of replication-competent proviruses isolated from patients at different time points confirmed the presence of expanded clones and demonstrated that while some clones harboring replication-competent virus persist longitudinally on a scale of years, others wax and wane. A similar pattern is observed in longitudinal sampling of residual viremia in patients. The observed patterns are not consistent with a continuous, cell-autonomous, proliferative process related to the HIV-1 integration site. The fact that the latent reservoir can be maintained, in part, by cellular proliferation without viral reactivation poses challenges to cure.

Episomal HIV-1 DNA and its relationship to other markers of HIV-1 persistence

Reverse transcription of HIV-1 results in the generation of a linear cDNA that serves as the precursor to the integrated provirus. Other classes of extrachromosomal viral cDNA molecules can be found in acutely infected cells including the 1-LTR and 2-LTR circles of viral DNA, also referred as episomal HIV-1 DNA. Circulating CD4⁺ T-cells of treatment-naïve individuals contain significant levels of unintegrated forms of HIV-1 DNA. However, the importance of episomal HIV-1 DNA in the study of viral persistence during antiviral therapy (ART) is debatable. 2-LTR circles are preferentially observed in the effector memory CD4⁺ T cell subset of long-term treated subjects. Treatment intensification of standard regimens has been used to determine if more potent ART can impact viral reservoir activity. Adding a potent antiretroviral drug to a stable triple-drug regimen has no measurable impact on plasma HIV-1 RNA levels, suggesting that ongoing cycles of HIV-1 replication are not a major mechanism driving persistent plasma viremia during triple-drug ART. However, in randomized clinical trials of HIV-1-infected adults on apparently effective ART, the addition of an integrase inhibitor (raltegravir) to stable regimens resulted in a transient increase in 2-LTR circles in some patients, suggesting a pre-intensification steady-state in which the processes of virion generation and de novo infection were occurring. Mathematical modeling of 2-LTR production during integrase inhibitor intensification suggests the coexistence, at different levels, of ongoing de novo infection and de novo replication mechanisms, specifically in inflamed lymphoid drug sanctuaries. Most reports looking into potential changes in 2-LTR circles in interventional clinical studies have simultaneously assessed other potential surrogate markers of viral persistence. Transient increases in 2-LTR circles have been correlated to decreases in CD8⁺ T-cell activation, transient CD45RA⁻CD4⁺ T-cell redistribution, and decreases in the hypercoagulation biomarker D-dimer in ART-intensified individuals. It is difficult, however, to establish a systematic association because the level of correlation with different types of markers differs significantly among studies. In conclusion, despite suppressive ART, a steady-state of de novo infection may persist in some infected individuals and that this may drive immune activation and inflammation changes reflecting residual viral reservoir activity during otherwise apparently suppressive ART.

Exploring viral reservoir: The combining approach of cell sorting and droplet digital PCR

Combined antiretroviral therapy (cART) blocks different steps of HIV replication and maintains plasma viral RNA at undetectable levels. The virus can remain in long-living cells and create a reservoir where HIV can restart replicating after cART discontinuation. A persistent viral production triggers and maintains a persistent immune activation, which is a well-known feature of chronic HIV infection, and contributes either to precocious aging, or to the increased incidence of morbidity and mortality of HIV positive patients. The new frontier of the treatment of HIV infection is nowadays eradication of the virus from all host cells and tissues. For this reason, it is crucial to have a clear and precise idea of where the virus hides, and which are the cells that keep it silent. Important efforts have been made to improve the detection of viral reservoirs, and new techniques are now giving the opportunity to characterize viral reservoirs. Among these techniques, a strategic approach based upon cell sorting and droplet digital PCR (ddPCR) is opening new horizons and opportunities of research. This review provides an overview of the methods that combine cell sorting and ddPCR for the quantification of HIV DNA in different cell types, and for the detection of its maintenance.

How to Define the Latent Reservoir: Tools of the Trade

HIV is a devastating worldwide epidemic that has had substantial social and economic impacts throughout the globe. Due to the presence of a small pool of latently infected cells that persists during antiretroviral therapy (ART), HIV is not curable. Because of the high cost of ART and the lack of reliable accessibility across the globe, life-long ART is unfortunately not a feasible solution for the epidemic. Therefore, new strategies need to be developed and implemented to address HIV-1 infection. Several approaches toward this end are currently under investigation (Ebina et al. in Sci Rep 3:2510, 2013; Archin et al. in Nature 487:482–5, 2012; Elliott et al. in PLoS Pathog 10:e1004473, 2014; Rasmussen et al. in Lancet HIV 1:e13–e21, 2014; Tebas et al. in N Engl J Med 370:901–10, 2014; Archin et al. in Nat Rev Microbiol 12:750–64, 2014; Barton et al. in PLoS One 9:e102684, 2014; Sogaard et al. in PLoS Pathog 11:e1005142, 2015). Initial studies have proven promising, but have highlighted the need for sensitive and accurate assays to detect changes in very low concentrations of virus to allow confident interpretation of the success of curative approaches. This review will focus on assays that are currently available and the advantages and limitations of each.

Influence of raltegravir intensification on viral load and 2-LTR dynamics in HIV patients on suppressive antiretroviral therapy

Antiretroviral therapy can suppress HIV-1 plasma viral load to below the detection limit but cannot eradicate the virus. Whether residual ongoing viral replication persists during suppressive therapy remains unclear. A few clinical studies showed that treatment intensification with an additional drug led to a lower viral load or an increase in 2-LTR (long terminal repeat), a marker for ongoing viral replication. However, some other studies found no change in the viral load and 2-LTR. In this paper, we developed multi-stage models to evaluate the influence of treatment intensification with the integrase inhibitor raltegravir on viral load and 2-LTR dynamics in HIV patients under suppressive therapy. We analyzed one model and obtained the local and global stability of the steady states. The model and its variation predict that raltegravir intensification induces a very minor decrease in the viral load and a minor increase in 2-LTR. We also compared modeling prediction with the 2-LTR data in a raltegravir intensification study. To achieve the 2-LTR increase observed in some patients, the level of viral replication needs to be substantially high, which is inconsistent with the sustained viral suppression in patients during treatment intensification. These modeling results, together with the theoretical estimate of the upper bound of the 2-LTR increase, suggest that treatment intensification with raltegravir has a minor effect on the plasma viremia and 2-LTR in patients under suppressive therapy. Other treatment strategies have to be developed for the cure or functional control of the infection.

Prolonged persistence of a novel replication-defective HIV-1 variant in plasma of a patient on suppressive therapy

BACKGROUND

Cell-free residual HIV-1 virions (RVs) persist in plasma below 20-50 vRNA copies/ml in most patients on suppressive antiretroviral therapy (ART). How RVs are produced in the body during therapy is not fully clear. In this study, we have attempted to characterize these viruses of an ART-treated patient in vitro in order to gain insights into the mechanism of their production in vivo.

METHODS

We have reconstructed almost the entire genomes of RVs as DNA forms using the patient's residual plasma vRNA by an overlapping RT-nested PCR method, and then sequence-analyzed the cloned genomes and tested them for their biological activities in vitro.

RESULTS

We found that the reconstructed molecular clones of RVs lacked antiretroviral drug-resistant mutations, as well as G-to-A hypermutations. The vDNA clones, when transfected into TZM-bl cells, released HIV-p24 into the culture media at extremely low levels. This low-level virus production was found to be due to the presence of a unique mutation (GU-to-GC) in the conserved 5'-major splice donor (MSD) motif of the corresponding vRNAs. We found that the incorporation of this point mutation by itself could cause defects in the replication of a standard HIV strain (JRCSF) in vitro. However, this novel viral variant was intermittently detected at 5 of 7 time-points in the patient's plasma over a period of 39 months during therapy.

CONCLUSIONS

This is the first identification of a natural point mutation (GU-to-GC) in the conserved 5'-MSD motif of HIV genomic RNA. The intermittent but prolonged detection of this replication-defective HIV variant in the patient's plasma among other viral populations strongly suggests that this variant is released from highly stable productively infected cells present in vivo during therapy. The potential implication of this observation is that the elimination of such productively infected cells that contribute to residual viremia during suppressive therapy could be an important first step towards achieving a cure for HIV.

A Pilot Study of Raltegravir Plus Combination Antiretroviral Therapy in Early Human Immunodeficiency Virus Infection: Challenges and Lessons Learned

Availability of integrase strand transfer inhibitors created interest in determining whether their use would decrease persistently infected cell numbers. This study hypothesized that adding raltegravir (RAL) to standard antiretroviral therapy (ART) would decrease human immunodeficiency virus (HIV)-infected CD4⁺ T cells more than standard combination ART. This was a pilot, randomized study comparing open-label standard triple ART to standard triple ART plus RAL over 96 weeks in ART-naive adults with early HIV infection. The primary objective was to compare quantity and trajectory of HIV DNA. Eighty-two persons were referred. A diverse set of reasons precluded the enrollment of all but 10. Those who enrolled and completed the study had an estimated median duration of HIV infection of 74 days at ART start. The groups had similar baseline characteristics. The RAL group had more rapid first phase plasma HIV RNA decay (0.67 log₁₀ copies/mL/day) than with combination ART (0.34 log₁₀copies/mL/day), p = 0.037. Second phase HIV RNA decay, residual viremia, cell-associated RNA, HIV DNA, CD4⁺ T-cells with replication-competent virus, and 2LTR circle levels did not differ between groups. Among those with entry plasma HIV RNA levels above the median, 2LTR circles were significantly lower over time than in those with lower entry HIV RNA levels (p = 0.02). Our results suggest homogeneity of responses in cell-associated RNA, HIV DNA, CD4⁺ T-cells with replication-competent virus, and 2LTR circles with early HIV in both ART groups. The kinetics of 2LTR DNA did not reflect the kinetics of plasma HIV RNA decline following ART initiation.

The Tat Inhibitor Didehydro-Cortistatin A Prevents HIV-1 Reactivation from Latency

Antiretroviral therapy (ART) inhibits HIV-1 replication, but the virus persists in latently infected resting memory CD4⁺ T cells susceptible to viral reactivation. The virus-encoded early gene product Tat activates transcription of the viral genome and promotes exponential viral production. Here we show that the Tat inhibitor didehydro-cortistatin A (dCA), unlike other antiretrovirals, reduces residual levels of viral transcription in several models of HIV latency, breaks the Tat-mediated transcriptional feedback loop, and establishes a nearly permanent state of latency, which greatly diminishes the capacity for virus reactivation. Importantly, treatment with dCA induces inactivation of viral transcription even after its removal, suggesting that the HIV promoter is epigenetically repressed. Critically, dCA inhibits viral reactivation upon CD3/CD28 or prostratin stimulation of latently infected CD4⁺ T cells from HIV-infected subjects receiving suppressive ART. Our results suggest that inclusion of a Tat inhibitor in current ART regimens may contribute to a functional HIV-1 cure by reducing low-level viremia and preventing viral reactivation from latent reservoirs.

Antiretroviral therapy (ART) reduces HIV-1 replication to very low levels, but the virus persists in latently infected memory CD4⁺ T cells, representing a long-lasting source of resurgent virus upon ART interruption. Based on the mode of action of didehydro-cortistatin A (dCA), a Tat-dependent transcription inhibitor, our work highlights an alternative approach to current HIV-1 eradication strategies to decrease the latent reservoir. In our model, dCA blocks the Tat feedback loop initiated after low-level basal reactivation, blocking transcriptional elongation and hence viral production from latently infected cells. Therefore, dCA combined with ART would be aimed at delaying or halting ongoing viral replication, reactivation, and replenishment of the latent viral reservoir. Thus, the latent pool of cells in an infected individual would be stabilized, and death of the long-lived infected memory T cells would result in a continuous decay of this pool over time, possibly culminating in the long-awaited sterilizing cure.

Early antiretroviral therapy with raltegravir generates sustained reductions in HIV reservoirs but not lower T-cell activation levels

OBJECTIVE

The initiation of antiretroviral therapy (ART) during primary infection may offer clinical benefits for HIV-infected individuals by reducing HIV DNA reservoir size and chronic T-cell activation. Current evidence for the advantages of early ART, however, are mostly derived from cross-sectional studies, with the long-term benefits yet to be ascertained.

DESIGN/METHODS

We conducted an open-label, nonrandomized study, monitoring for 3 years: plasma viral load (pVL), T-cell phenotypes, and peripheral CD4(+) T-cell associated total, integrated and 2-long terminal repeat HIV DNA species. The study included 16 treatment-naive individuals initiating ART with raltegravir and Truvada during either primary (PHI, n = 8) or chronic (CHI, n = 8) HIV infection.

RESULTS

ART initiated during PHI compared with CHI generated significant reductions of peripheral CD4(+) T-cell HIV DNA reservoirs that were sustained for 3 years of therapy. Median log10 HIV DNA copies/10(6) CD4(+) T cells at the final visit: total; CHI = 3.23 > PHI = 2.72, P < 0.01; integrated; CHI = 2.64 > PHI = 1.77, P < 0.01. Similar trends were observed for pVL, however, did not reach significance: log10 HIV RNA copies/ml plasma at the final visit: CHI = 1.3 ≥ PHI = 0.39, P = 0.08. Both cohorts displayed similar and elevated levels of CD38/HLA-DR coexpression on CD4(+) and CD8(+) T cells relative to uninfected healthy controls.

CONCLUSION

The reduction in HIV DNA reservoirs generated by the early initiation of ART was sustained for 3 years of therapy. Although the PHI cohort trended to lower levels of pVL, and pVL was associated with CD8(+) T-cell activation, no differences in T-cell activation were observed between the PHI and CHI groups.

Towards an HIV-1 cure: measuring the latent reservoir

The latent reservoir (LR) of HIV-1 in resting memory CD4(+) T cells serves as a major barrier to curing HIV-1 infection. While many PCR- and culture-based assays have been used to measure the size of the LR, correlation between results of different assays is poor and recent studies indicate that no available assay provides an accurate measurement of reservoir size. The discrepancies between assays are a hurdle to clinical trials that aim to measure the efficacy of HIV-1 eradication strategies. Here we describe the advantages and disadvantages of various approaches to measuring the LR.

Effect of therapeutic intensification followed by HIV DNA prime and rAd5 boost vaccination on HIV-specific immunity and HIV reservoir (EraMune 02): a multicentre randomised clinical trial

BACKGROUND

Achievement of a cure for HIV infection might need reactivation of latent virus and improvement of HIV-specific immunity. As an initial step, in this trial we assessed the effect of antiretroviral therapy intensification and immune modulation with a DNA prime and recombinant adenovirus 5 (rAd5) boost vaccine.

METHODS

In this multicentre, randomised, open-label, non-comparative, phase 2 clinical trial, we enrolled eligible adults 18-70 years of age with chronic HIV-1 infection on suppressive antiretroviral therapy with current CD4 count of at least 350 cells per μL and HIV DNA between 10 and 1000 copies per 10(6) peripheral blood mononuclear cells. After an 8 week lead-in of antiretroviral intensification therapy (standard dose raltegravir and dose-adjusted maraviroc based on baseline antiretroviral therapy), patients were randomly assigned (1:1) to receive antiretroviral therapy intensification alone or intensification plus injections of HIV DNA prime vaccine (4 mg VRC-HIVDNA016-00-VP) at weeks 8, 12, and 16, followed by HIV rAd5 boost vaccine (10(10) particle units of VRC-HIVADV014-00-VP) at week 32. Randomisation was computer generated in permuted blocks of six and was stratified by study site. The primary endpoint was a 0·5 log10 or greater decrease in HIV DNA in peripheral blood mononuclear cells at week 56. This study is registered with ClinicalTrials.gov, number NCT00976404.

FINDINGS

Between Nov 29, 2010, and Oct 28, 2011, we enrolled 28 eligible patients from three academic HIV clinics in the USA. After the 8 week lead-in of antiretroviral intensification therapy, 14 patients were randomly assigned to continue antiretroviral therapy intensification alone and 14 to intensification plus vaccine. Enrolled participants had median CD4 count of 636 cells per μL, median HIV DNA 170 copies per 10(6) peripheral blood mononuclear cells, and duration of antiretroviral therapy of 13 years. The median amount of HIV DNA did not change significantly between baseline and week 56 in the antiretroviral therapy intensification plus vaccine group. One participant in the antiretroviral therapy intensification alone group reached the primary endpoint, with 0·55 log10 decrease in HIV DNA in peripheral blood mononuclear cells. Both treatments were well tolerated. No severe or systemic reactions to vaccination occurred, and five serious adverse events were recorded during the study, most of which resolved spontaneously or were judged unrelated to study treatments.

INTERPRETATION

Antiretroviral therapy intensification followed by DNA prime and rAd5 boost vaccine did not significantly increase HIV expression or reduce the latent HIV reservoir. A multifaceted approach that includes stronger activators of HIV expression and novel immune modulators will probably be needed to reduce the latent HIV reservoir and allow for long-term control in patients off antiretroviral therapy.

FUNDING

Objectif Recherche Vaccin SIDA (ORVACS).

Potential implication of residual viremia in patients on effective antiretroviral therapy

The current antiretroviral therapy (ART) has suppressed viremia to below the limit of detection of clinical viral load assays; however, it cannot eliminate viremia completely in the body even after prolonged treatment. Plasma HIV-1 loads persist at extremely low levels below the clinical detection limit. This low-level viremia (termed "residual viremia") cannot be abolished in most patients, even after the addition of a new class of drug, i.e., viral integrase inhibitor, to the combined antiretroviral regimens. Neither the cellular source nor the clinical significance of this residual viremia in patients on ART remains fully clear at present. Since residual plasma viruses generally do not evolve with time in the presence of effective ART, one prediction is that these viruses are persistently released at low levels from one or more stable but yet unknown HIV-1 reservoirs in the body during therapy. This review attempts to emphasize the source of residual viremia as another important reservoir (namely, "active reservoir") distinct from the well-known latent HIV-1 reservoir in the body, and why its elimination should be a priority in the effort for HIV-1 eradication.

Quantification of HIV-1 latency reversal in resting CD4+ T cells from patients on suppressive antiretroviral therapy

Reversal of proviral latency is being pursued as a curative strategy for HIV-1 infection. Recent clinical studies of in vivo administration of the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA; vorinostat) show increases in unspliced cellular HIV-1 RNA levels in resting CD4(+) T cells. A critical unknown, however, is the proportion of latent proviruses that can be transcriptionally reactivated by SAHA or T-cell activation. In this study, we quantified the fraction of HIV-1 proviruses in resting CD4(+) T cells from patients on suppressive antiretroviral therapy that were reactivated ex vivo with SAHA or antibodies to CD3/CD28. At concentrations of SAHA achieved clinically, only 0.079% of proviruses in resting CD4(+) T cells were reactivated to produce virions, compared with 1.5% of proviruses in cells treated with anti-CD3/CD28 antibodies after correcting for spontaneous virion production in the medium control. A significant positive correlation (ρ = 0.67, P < 0.001) was found between levels of virions in the supernatant and unspliced cellular HIV-1 RNA following anti-CD3/CD28 treatment, but not following SAHA treatment (ρ = 0.21, P = 0.99). These results reveal that the majority of HIV-1 proviruses are not reactivated by current therapeutic approaches and that more effective means of reversing proviral latency will likely be required to deplete HIV-1 reservoirs.

HIV cure research: advances and prospects

Thirty years after the identification of HIV, a cure for HIV infection is still to be achieved. Advances of combined antiretroviral therapy (cART) in recent years have transformed HIV infection into a chronic disease when treatment is available. However, in spite of the favorable outcomes provided by the newer therapies, cART is not curative and patients are at risk of developing HIV-associated disorders. Moreover, universal access to antiretroviral treatment is restricted by financial obstacles. This review discusses the most recent strategies that have been developed in the search for an HIV cure and to improve life quality of people living with HIV.

Switch to raltegravir decreases soluble CD14 in virologically suppressed overweight women: the Women, Integrase and Fat Accumulation Trial

OBJECTIVES

Soluble CD14 (sCD14) is a monocyte activation marker associated with increased mortality in HIV infection. We assessed 48-week changes in sCD14 and other inflammatory biomarkers in virologically suppressed, HIV-infected women switching to raltegravir (RAL) from a protease inhibitor (PI) or nonnucleoside reverse transcriptase inhibitor (NNRTI).

METHODS

HIV-infected women with central adiposity and HIV-1 RNA < 50 HIV-1 RNA copies/mL continued their thymidine-sparing nucleoside reverse transcriptase inhibitor (NRTI) backbone and were randomized to switch to open-label RAL at week 0 (immediate) or 24 (delayed). In an exploratory analysis, inflammatory biomarkers were measured on stored fasting plasma.

RESULTS

Of the 37 evaluable subjects, 78% were non-White; the median age was 43 years, the median body mass index (BMI) was 32 kg/m(2) and the median CD4 count was 558 cells/μL. At baseline, biomarker values were similar between groups. After 24 weeks, median sCD14 significantly declined in subjects switching to RAL [-21% (P < 0.001) vs. PI/NNRTI -5% (P = 0.49); between-group P < 0.01]. After 48 weeks, immediate-switch subjects maintained this decline and delayed-switch subjects experienced a similar decline following the switch to RAL (-10%; within-group P < 0.01). Immediate-switch subjects also experienced an initial increase in tumour necrosis factor (TNF)-α that was neither maintained after 48 weeks nor seen in delayed-switch subjects. After adjustment for multiple testing, only declines in sCD14 remained significant.

CONCLUSIONS

In this randomized trial of women with central adiposity, a switch to RAL from a PI or NNRTI was associated with a statistically significant decline in sCD14. Further studies are needed to determine whether integrase inhibitors have improved monocyte activation profiles compared with PIs and/or NNRTIs, and whether measured differences between antiretroviral agents translate to demonstrable clinical benefit.

Plasma viremia and cellular HIV-1 DNA persist despite autologous hematopoietic stem cell transplantation for HIV-related lymphoma

A cure of HIV-1 has been achieved in one individual through allogeneic stem cell transplantation with a CCR5[INCREMENT]32 homozygous donor. Whether myeloablation and autologous stem cell transplantation for lymphoma in patients on suppressive antiretroviral therapy can eliminate HIV-1 reservoirs is unknown. Low-level plasma viremia and total HIV-1 DNA and 2-LTR circles in blood mononuclear cells were quantified after autologous transplantation in 10 patients on suppressive antiretroviral therapy using quantitative polymerase chain reaction assays capable of single-copy nucleic acid detection. Plasma viremia was detectable in 9 patients, whereas HIV-1 DNA was detectable in all 10 patients, indicating that HIV-1 had not been eliminated.

Increase in 2-long terminal repeat circles and decrease in D-dimer after raltegravir intensification in patients with treated HIV infection: a randomized, placebo-controlled trial

BACKGROUND

The degree to which human immunodeficiency virus (HIV) continues to replicate during antiretroviral therapy (ART) is controversial. We conducted a randomized, double-blind, placebo-controlled study to assess whether raltegravir intensification reduces low-level viral replication, as defined by an increase in the level of 2-long terminal repeat (2-LTR) circles.

METHODS

Thirty-one subjects with an ART-suppressed plasma HIV RNA level of <40 copies/mL and a CD4(+) T-cell count of ≥350 cells/mm(3) for ≥1 year were randomly assigned to receive raltegravir 400 mg twice daily or placebo for 24 weeks. 2-LTR circles were analyzed by droplet digital polymerase chain reaction at weeks 0, 1, 2, and 8.

RESULTS

The median duration of ART suppression was 3.8 years. The raltegravir group had a significant increase in the level of 2-LTR circles, compared to the placebo group. The week 1 to 0 ratio was 8.8-fold higher (P = .0025) and the week 2 to 0 ratio was 5.7-fold higher (P = .023) in the raltegravir vs. placebo group. Intensification also led to a statistically significant decrease in the D-dimer level, compared to placebo (P = .045).

CONCLUSIONS

Raltegravir intensification resulted in a rapid increase in the level of 2-LTR circles in a proportion of subjects, indicating that low-level viral replication persists in some individuals even after long-term ART. Intensification also reduced the D-dimer level, a coagulation biomarker that is predictive of morbidity and mortality among patients receiving treatment for HIV infection.

Dynamics of CD8 T-cell activation after discontinuation of HIV treatment intensification

BACKGROUND

Detection of episomal HIV cDNA has been associated with greater levels of CD8 and CD4 T-cell activation in HIV-1-infected highly active antiretroviral therapy (HAART)-suppressed individuals. However, HAART intensification exclusively reduced CD8 T-cell activation.

METHODS

We evaluated activation markers 12 weeks after raltegravir withdrawal in a previously described 48-week raltegravir intensification study. The subjects (n = 34) were subgrouped into 2-LTR(+) (n = 12) or 2-LTR(-) (n = 22) subgroups according to delectability of 2-LTR episomes during the intensification period.

RESULTS

The initial differences in CD8 T-cell activation between subgroups were lost after intensification. Linear mixed models revealed significant reductions in CD8 T-cell activation in both 2-LTR(-) and 2-LTR(+) subgroups, suggesting that raltegravir impacts subjects irrespective of 2-LTR detection. Remarkably, a partial rebound in CD8 activation markers after raltegravir discontinuation was observed in the 2-LTR(+) subgroup. This restored the differences between subgroups observed at study entry, particularly in terms of CD38 expression within CD8 memory T-cells. Conversely, CD4 T-cell activation remained unchanged in both subgroups during the study period, although an early and transient CD45RA(-) CD4 T-cell redistribution from tissues was apparent.

CONCLUSIONS

CD8 T-cell activation undergoes reversible changes during raltegravir intensification and discontinuation in patients showing detectable 2-LTR circles. The general decrease in CD8 T-cell activation and a transient CD45RA(-) CD4 T-cell redistribution in intensified individuals may reflect residual viral replication during apparently suppressive HAART.

Modelling HIV-1 2-LTR dynamics following raltegravir intensification

A model of reservoir activation and viral replication is introduced accounting for the production of 2-LTR HIV-1 DNA circles following antiviral intensification with the HIV integrase inhibitor raltegravir, considering contributions of de novo infection events and exogenous sources of infected cells, including quiescent infected cell activation. The model shows that a monotonic increase in measured 2-LTR concentration post intensification is consistent with limited de novo infection primarily maintained by sources of infected cells unaffected by raltegravir, such as quiescent cell activation, while a transient increase in measured 2-LTR concentration is consistent with significant levels of efficient (R0 > 1) de novo infection. The model is validated against patient data from the INTEGRAL study and is shown to have a statistically significant fit relative to the null hypothesis of random measurement variation about a mean. We obtain estimates and confidence intervals for the model parameters, including 2-LTR half-life. Seven of the 13 patients with detectable 2-LTR concentrations from the INTEGRAL study have measured 2-LTR dynamics consistent with significant levels of efficient replication of the virus prior to treatment intensification.

Cell-associated HIV RNA: a dynamic biomarker of viral persistence

In most HIV-infected individuals adherent to modern antiretroviral therapy (ART), plasma viremia stays undetectable by clinical assays and therefore, additional virological markers for monitoring and predicting therapy responses and for measuring the degree of HIV persistence in patients on ART should be identified. For the above purposes, quantitation of cell-associated HIV biomarkers could provide a useful alternative to measurements of viral RNA in plasma. This review concentrates on cell-associated (CA) HIV RNA with the emphasis on its use as a virological biomarker. We discuss the significance of CA HIV RNA as a prognostic marker of disease progression in untreated patients and as an indicator of residual virus replication and the size of the dynamic viral reservoir in ART-treated patients. Potential value of this biomarker for monitoring the response to ART and to novel HIV eradication therapies is highlighted.

Do HIV-specific CTL continue to have an antiviral function during antiretroviral therapy? If not, why not, and what can be done about it?

Pharmacological reactivation of human immunodeficiency virus (HIV) expression from latent proviruses coupled with fully suppressive antiretroviral therapy (ART) has been suggested as a strategy to eradicate HIV infection. In order for this strategy to be effective, latently infected cells must be killed either by the cytopathic effect of reactivated HIV gene expression, or by HIV-specific cytotoxic T lymphocyte (CTL). However, a review of current data reveals little evidence that CTL retain an antiviral effector capacity in patients on fully suppressive ART, implying that the HIV-specific CTL present in these patients will not be able to eliminate HIV-infected CD4(+) T cells effectively. If this is due to functional impairment or a quantitative deficit of HIV-specific CTL during ART, then therapeutic vaccination may improve the prospects for eradicating latent reservoirs. However, data from the macaque simian immunodeficiency virus (SIV) model indicate that in vivo, SIV-specific CTL are only effective during the early stages of the viral replication cycle, and this constitutes an alternative explanation why HIV-specific CTL do not appear to have an impact on HIV reservoirs during ART. In that case, immunotoxins that target HIV-expressing cells may be a more promising approach for HIV eradication.

Human immunodeficiency virus (HIV) latency: the major hurdle in HIV eradication

Failure of highly active antiretroviral therapy to eradicate the human immunodeficiency virus (HIV), even in patients who suppress the virus to undetectable levels for many years, underscores the problems associated with fighting this infection. The existence of persistent infection in certain cellular and anatomical reservoirs appears to be the major hurdle in HIV eradication. The development of therapeutic interventions that eliminate or limit the latent viral pools or prevent the reemergence of the viruses from producing cells will therefore be required to enhance the effectiveness of current antiretroviral strategies. To achieve this goal, there is a pressing need to understand HIV latency at the molecular level to design novel and improved therapies to either eradicate HIV or find a functional cure in which patients could maintain a manageable viral pool without AIDS in the absence of antiretroviral therapy. The integrated proviral genome remains transcriptionally silent for a long period in certain subsets of T cells. This ability to infect cells latently helps HIV to establish a persistent infection despite strong humoral and cellular immune responses against the viral proteins. The main purpose of this report is to provide a general overview of the HIV latency. We will describe the hurdles being faced in eradicating latent HIV proviruses. We will also briefly discuss the ongoing strategies aimed toward curing HIV infection.

Developing strategies for HIV-1 eradication

Highly active antiretroviral therapy (HAART) suppresses HIV-1 replication, transforming the outlook for infected patients. However, reservoirs of replication-competent forms of the virus persist during HAART, and when treatment is stopped, high rates of HIV-1 replication return. Recent insights into HIV-1 latency, as well as a report that HIV-1 infection was eradicated in one individual, have renewed interest in finding a cure for HIV-1 infection. Strategies for HIV-1 eradication include gene therapy and hematopoietic stem cell transplantation, stimulating host immunity to control HIV-1 replication, and targeting latent HIV-1 in resting memory CD4(+) T cells. Future efforts should aim to provide better understanding of how to reconstitute the CD4(+) T cell compartment with genetically engineered cells, exert immune control over HIV-1 replication, and identify and eliminate all viral reservoirs.

No effect of raltegravir intensification on viral replication markers in the blood of HIV-1-infected patients receiving antiretroviral therapy

BACKGROUND

Controversy continues regarding the extent of ongoing viral replication in HIV-1-infected patients on effective antiretroviral therapy (ART). Adding an additional potent agent, such as raltegravir, to effective ART in patients with low-level residual viremia may reveal whether there is ongoing HIV-1 replication.

METHODS

We previously reported the outcome of a randomized placebo-controlled study of raltegravir intensification in patients on ART with HIV-1 RNA <50 copies per milliliter that showed no effect on residual viremia measured by single copy assay. We now report the effects of raltegravir intensification in that trial on other potential measures of ongoing HIV-1 replication as follows: 2-LTR HIV-1 circles, total cellular HIV-1 DNA, and T-cell activation.

RESULTS

Of 50 patients tested, 12 (24%) had 2-LTR circles detected at baseline. Patients who were 2-LTR-positive had higher plasma HIV-1 RNA and HIV-1 DNA levels than 2-LTR-negative individuals. At week 12 of raltegravir intensification, there was no change from baseline in 2-LTR circles, in total HIV-1 DNA or in the ratio of 2-LTR circles to total HIV-1 DNA. There was also no change in markers of T-cell activation.

CONCLUSIONS

In HIV-1-infected individuals on effective ART, we find no evidence of ongoing viral replication in the blood that is suppressible by raltegravir intensification. The results imply that raltegravir intensification alone will not eradicate HIV-1 infection.