Short-cycle structured intermittent treatment of chronic HIV infection with highly active antiretroviral therapy: effects on virologic, immunologic, and toxicity parameters

Multiple treatment interruptions and protecting HIV-specific CD4 T cells enable durable CD8 T cell response and viral control

Human Immunodeficiency Virus (HIV) remains a global health challenge, and novel approaches to improve HIV control are significantly important. The cell and gene therapy product AGT103-T was previously evaluated (NCT04561258) for safety, immunogenicity, and persistence in seven patients for up to 180 days post infusion. In this study, we sought to investigate the impact of AGT103-T treatment upon analytical treatment interruptions (ATIs). Six patients previously infused with AGT103-T were enrolled into an ATI study (NCT05540964), wherein they suspended their antiretroviral therapy (ART) until their viral load reached 100,000 copies/mL in two successive visits, or their CD4 count was reduced to below 300 cells/μL. During the ATI, all patients experienced viral rebound followed by a notable expansion in HIV specific immune responses. The participants demonstrated up to a five-fold increase in total CD8 counts over baseline approximately 1-2 weeks followed by the peak viremia. This coincided with a rise in HIV-specific CD8 T cells, which was attributed to the increase in antigen availability and memory recall. Thus, the protocol was amended to include a second ATI with the first ATI serving as an "auto-vaccination." Four patients participated in a second ATI. During the second ATI, the Gag-specific CD8 T cells were either maintained or rose in response to viral rebound and the peak viremia was substantially decreased. The patients reached a viral set point ranging from 7,000 copies/mL to 25,000 copies/mL. Upon resuming ART, all participants achieved viral control more rapidly than during the first ATI, with CD4 counts remaining within 10% of baseline measurements and without any serious adverse events or evidence of drug resistance. In summary, the rise in CD8 counts and the viral suppression observed in 100% of the study participants are novel observations demonstrating that AGT103-T gene therapy when combined with multiple ATIs, is a safe and effective approach for achieving viral control, with viral setpoints consistently below 25,000 copies/mL and relatively stable CD4 T cell counts. We conclude that HIV cure-oriented cell and gene therapy trials should include ATI and may benefit from designs that include multiple ATIs when induction of CD8 T cells is required to establish viral control.

D’un protocole de soin au succès d’un essai clinique

Les innovations pour traiter l’infection par le virus de l’immunodéficience humaine (VIH) n’ont pas cessé depuis les premières monothérapies et, en 1996, les premières trithérapies. L’une d’elles vient d’être validée par l’essai ANRS QUATUOR. Elle consiste à prendre deux fois moins de médicaments, en rendant le traitement intermittent. À la demande des patients non adhérents à sa prescription standard, Jacques Leibowitch a encadré cette pratique dès 2002, en s’appuyant sur une étude transgressant le dogme de l’adhésion stricte au traitement quotidien. Ce concept de traitement à temps partiel provenait des travaux du groupe d’Anthony Fauci, mais il le revisitera pour le pousser à son apogée avec la cohorte Iccarre. Son intention strictement thérapeutique s’inscrivit initialement dans le cadre du protocole de soin Iccarre qui, en 2020, comptait 96 patients, majoritairement en réduction médicamenteuse de 70 % grâce à l’ultra-intermittence thérapeutique. Il a posé les bases de l’essai contrôlé QUATUOR dont le résultat, récemment publié, montre la non infériorité des traitements intermittents à 4 jours/7 de médicaments par rapport au traitement standard.

Antiretroviral Drug-Resistance Mutations on the Gag Gene: Mutation Dynamics during Analytic Treatment Interruption among Individuals Experiencing Virologic Failure

We describe drug-resistance mutation dynamics of the gag gene among individuals under antiretroviral virologic failure who underwent analytical treatment interruption (ATI). These mutations occur in and around the cleavage sites that form the particles that become the mature HIV-1 virus. The study involved a 12-week interruption in antiretroviral therapy (ART) and sequencing of the gag gene in 38 individuals experiencing virologic failure and harboring triple-class resistant HIV strains. Regions of the gag gene surrounding the NC-p2 and p1-p6 cleavage sites were sequenced at baseline before ATI and after 12 weeks from plasma HIV RNA using population-based Sanger sequencing. Fourteen of the sixteen patients sequenced presented at least one mutation in the gag gene at baseline, with an average of 4.93 mutations per patient. All the mutations had reverted to the wild type by the end of the study. Mutations in the gag gene complement mutations in the pol gene to restore HIV fitness. Those mutations around cleavage sites and within substrates contribute to protease inhibitor resistance and difficulty in re-establishing effective virologic suppression. ART interruption in the presence of antiretroviral resistant HIV strains was used here as a practical measure for more adapted HIV profiles in the absence of ART selective pressure.

Fitness Cost of Antiretroviral Drug Resistance Mutations on the pol Gene during Analytical Antiretroviral Treatment Interruption among Individuals Experiencing Virological Failure

HIV cure studies require patients to enter an analytical treatment interruption (ATI). Here, we describe previously unanalyzed data that sheds light on ATI dynamics in PLHIV (People Living with HIV). We present drug resistance mutation dynamics on the pol gene among individuals with antiretroviral virological failure who underwent ATI. The study involved a 12-week interruption in antiretroviral therapy (ART), monitoring of viral load, CD4+/CD8+ T cell counts, and sequencing of the pol gene from 38 individuals experiencing virological failure and harboring 3-class resistant HIV strains: nucleoside reverse transcriptase inhibitors (NRTI) non-nucleoside inhibitors (NNRTI), and protease inhibitors (PI). Protease and reverse transcriptase regions of the pol gene were sequenced at baseline before ATI and every four weeks thereafter from PBMCs and at baseline and after 12 weeks from plasma HIV RNA using population-based Sanger sequencing. Average viral load increased 0.559 log₁₀ copies per milliliter. CD4+ T cell count decreased as soon as ART was withdrawn, an average loss of 99.0 cells/mL. Forty-three percent of the mutations associated with antiretroviral resistance in PBMCs disappeared and fifty-seven percent of the mutations in plasma reverted to wild type, which was less than the 100% reversion expected. In PBMC, the PI mutations reverted more slowly than reverse transcriptase mutations. The patients were projected to need an average of 33.7 weeks for PI to revert compared with 20.9 weeks for NRTI and 19.8 weeks for NNRTI. Mutations in the pol gene can cause virological failure and difficulty in re-establishing effective virological suppression.

Pharmacological data of a successful 4-days-a-week regimen in HIV antiretroviral therapy (ANRS 162-4D trial)

INTRODUCTION

Few data are available on plasma concentrations of antiretroviral therapy (ARV) during intermittent treatment.

OBJECTIVE

To compare plasma concentrations in OFF vs ON treatment periods at several time points during treatment.

METHODS

During a successful 48-week multicenter study (ANRS 162-4D trial) of 4 days with treatment (ON) followed by 3 days without treatment (OFF) in adults treated by two nucleoside analogues and a third agent belonging to a boosted protease-inhibitor (PI, darunavir [DRV], atazanavir [ATV], lopinavir [LPV]) or a non-nucleoside-reverse-transcriptase inhibitor (NNRTI, efavirenz [EFV], etravirine [ETR], rilpivirine [RPV]) conducted in 100 patients (96% success), we determined the plasma concentrations of ARV. Blood samples were collected for analysis at inclusion (W0, 7/7 strategy for all patients), W16 and W40 (ON) and at W4, W8, W12, W24, W32 and W48 (OFF).

RESULTS

A total of 866 samples was analysed. Plasma concentrations were not statistically lower after 4 days (ON) vs 7/7 days of treatment except for RPV (-30 ng/mL at 4/7, P = 0.003). Significant lower plasma concentrations were observed for OFF vs ON except for ETR (n = 5, P = 0.062). Overall, 87.1% of ON concentrations (ATV 92.1%, DRV 51.1%, LPV 62.5%, EFV 94.4%, ETR 100% and RPV 94.9%) and 21.8% of OFF concentrations (ATV 1.4%, DRV 0.0%, LPV 0.0%, EFV 16.0%, ETR 92.6% and RPV 39.0%) were above the theoretical limit of efficacy of the molecule. In the OFF period, 85.8% of PI concentrations were under the limit of quantification, while 98.0% of NNRTI concentrations were quantifiable.

CONCLUSION

Despite low/undetectable PI/NNRTI plasma concentrations in the OFF period, patients maintained an undetectable viral load. The mechanistic explanation should be investigated.

Health-related quality of life among adult HIV positive patients: assessing comprehensive themes and interrelated associations

Purpose

We selected and evaluated a comprehensive set of themes that encompass health-related quality of life (HRQOL) among HIV patients, which enables clinicians to tailor care to individual needs, follow changes over time and quantify returns on health care investments and interventions.

Methods

HIV patients (N = 250) of two Dutch HIV clinics were invited to complete an online survey comprised of a set of (adaptations of) validated questionnaires measuring eight themes, including general health (SF-12), stigma (short stigma scale), social support (SSL12-I), self-esteem (SISE), sexuality problems, anxiety and depression (HADS), sleeping difficulties (SCL90-Sleep) and perceived side-effects.

Results

Findings from 170 (response rate 68%) patients (Male = 159, 94.1%) showed that questionnaires had high internal consistency, and most themes significantly correlated (r’s .21 to − .69, p < .05) in the expected directions. Exploring cut-off scores shows that a significant proportion of patients score outside of the desired range on single themes (between 16.0 and 73.1%), and many patients on multiple themes simultaneously (8.9% on 5 or more themes). Regression analysis showed that social support, self-esteem and sexuality problems were associated with general health (R = .48, R² = .23, F(4,145) = 10.57, p < .001); adding anxiety and depression, sleeping difficulties and perceived side-effects explained 51.2% of the variance in total (R = .72, ∆R² = .29, F(3, 142) = 27.82, p < .001).

Conclusions

We succeeded in developing a questionnaire that comprehensively assesses HRQOL. HRQOL of the majority of Dutch HIV patients could be improved. The themes strongly influenced each other, therefore insights into any of the themes could inform interventions to improve HRQOL, and increase attention to these themes in routine consultations between patients and health care professionals.

Mechanistic Effect of NMSO3 on Replication of Human Immunodeficiency Virus

NMSO3, a sulphated sialyl lipid, was evaluated for its efficacy against human immunodeficiency virus type 1 (HIV-1). The compound exhibited concentration-dependent inhibition of HIV-1 replication in primary infection cell culture systems. Substantial inhibition was observed at concentrations of NMSO3 that showed little cytotoxicity. NMSO3 also exhibited anti HIV-1 activity in chronically HIV-1 infected cultures. The production of progeny viruses was completely abolished without cytotoxicity by continuous addition of NMSO3 to chronically infected U937 cells. Furthermore, in attempting to define the inhibitory mechanism of NMSO3, we investigated its effect on several steps of the HIV-1 replication cycle. NMSO3 competes with gp120 for binding to CD4 receptors on cells and inhibits the entry of HIV-1. By epitope analysis of the human CD4 molecule, NMSO3 inhibits the binding of antibodies, which recognize the D1 domain of CD4. Moreover, semi-quantitative reverse transcribed polymerase chain reaction (RT-PCR) showed that the integrated provirus is transcriptionally inactive in NMSO3-treated cells, supporting the lack of progeny in the culture supernatant of chronically HIV-1-infected cells treated with NMSO3. These findings indicate that NMSO3 has a unique mechanism of action against HIV-1 in both primary and chronic infection, and may be a valuable compound for the treatment of HIV-1 infection.

An IL-15 Dependent CD8 T Cell Response to Selected HIV Epitopes is Related to Viral Control in Early-Treated HIV-Infected Subjects

In some early-treated HIV+ patients, Structured Treatment Interruption (STI) is associated to spontaneous control of viral rebound. Thus, in this clinical setting, we analyzed the immunological parameters associated to viral control. Two groups of early treated patients who underwent STI were retrospectively defined, according to the ability to spontaneously control HIV replication (Controller and Non-controller). Plasma cytokine levels were analyzed by multiplex analysis. CD8 T cell differentiation was determined by polychromatic flow cytometry. Antigen-specific IFN-Γ production was analyzed by ELISpot and intracellular staining after stimulation with HIV-peptides. Long-term Elispot assays were performed in the presence or absence of IL-15. Plasma IL-15 was found decreased over a period of time in Non-Controller patients, whereas a restricted response to Gag (aa.167–202 and 265–279) and Nef (aa.86–100 and 111–138) immunodominant epitopes was more frequently observed in Controller patients. Interestingly, in two Non-Controller patients the CD8-mediated T cells response to immunodominant epitopes could be restored in vitro by IL-15, suggesting a major role of cytokine homeostasis on the generation of protective immunity. In early-treated HIV+ patients undergoing STI, HIV replication control was associated to CD8 T cell maturation and sustained IL-15 levels, leading to HIV-specific CD8 T cell responses against selected Gag and Nef epitopes.

Plasmacytoid dendritic cell and functional HIV Gag p55-specific T cells before treatment interruption can inform set-point plasma HIV viral load after treatment interruption in chronically suppressed HIV-1(+) patients

The identification of immune correlates of HIV control is important for the design of immunotherapies that could support cure or antiretroviral therapy (ART) intensification-related strategies. ART interruptions may facilitate this task through exposure of an ART partially reconstituted immune system to endogenous virus. We investigated the relationship between set-point plasma HIV viral load (VL) during an ART interruption and innate/adaptive parameters before or after interruption. Dendritic cell (DC), natural killer (NK) cell and HIV Gag p55-specific T-cell functional responses were measured in paired cryopreserved peripheral blood mononuclear cells obtained at the beginning (on ART) and at set-point of an open-ended interruption from 31 ART-suppressed chronically HIV-1(+) patients. Spearman correlation and linear regression modeling were used. Frequencies of plasmacytoid DC (pDC), and HIV Gag p55-specific CD3(+)  CD4(-)  perforin(+)  IFN-γ(+) cells at the beginning of interruption associated negatively with set-point plasma VL. Inclusion of both variables with interaction into a model resulted in the best fit (adjusted R(2)  = 0·6874). Frequencies of pDC or HIV Gag p55-specific CD3(+)  CD4(-)  CSFE(lo)  CD107a(+) cells at set-point associated negatively with set-point plasma VL. The dual contribution of pDC and anti-HIV T-cell responses to viral control, supported by our models, suggests that these variables may serve as immune correlates of viral control and could be integrated in cure or ART-intensification strategies.

Four days a week or less on appropriate anti-HIV drug combinations provided long-term optimal maintenance in 94 patients: the ICCARRE project

Short, intraweekly cycles of anti-HIV combinations have provided intermittent, effective therapy (on 48 patients) (1). The concept is now extended to 94 patients on treatment, 4 days per week or less, over a median of 2.7 discontinuous treatment years per patient. On suppressive combinations, 94 patients volunteered to treatment, 5 and 4 days per week, or reduced stepwise to 4, 3, 2, and 1 days per week in 94, 84, 66, and 12 patients, respectively, on various triple, standard, antiviral combinations, or nonregistered, quadruple, antiviral combinations. Ninety-four patients on treatment 4 days per week aggregated 165 intermittent treatment years; no viral breakthrough was observed over 87 average treatment weeks per patient, 63 of 94 having passed 2.5 intermittent treatment years on any of the antiviral combinations prescribed. On the hyperintermittent treatment of 3, 2, and 1 days per week, HIV RNA surged >50 copies, 4 weeks apart, in 18 instances (6.8 viral escapes/100 hyperdiscontinuous maintenance years). Viral escapes could have been a result of erratic adherence (EA) to regimen or follow-up (3 patients)--drug taken at half of the daily recommended dosage (8 patients) and/or overlooked archival-resistant HIVs from antecedent treatment failures (6 patients). Aside from the above circumstances, HIV unexpectedly rebounded in 3 patients on 2 days per week treatment and 1 patient on 1 day per week treatment, posting 2.2 intrinsic viral escapes/100 highly discontinuous treatment years. All 18 escapes were eventually reversed by 7 days per week salvage combinations, and 11 of 18 patients have been back for a second course of intermittent therapy, 4 days per week or less. Both cell-activation markers on the surface of T lymphocytes and cell-bound HIV DNA levels remained stable or declined. CD4/CD8 ratios rose to ≥1 in 35% of patients, whereas CD4 counts went ≥500/µl in 75%. These values were previously 7 and 40%, respectively, on 7 days per week therapy. In our aging, long, HIV-enduring, multitreated patient cohort, treatment 4 days per week and less over 421 intermittent treatment years reduced prescription medicines by 60%--equivalent to 3 drug-free/3 virus-free remission year per patient--actually sparing €3 million on just 94 patients at the cost of 2.2 intrinsic viral failure/100 hyperintermittent treatment years. At no risk of viral escape, maintenance therapy, 4 days per week, would quasiuniversally offer 40% cuts off of current overprescriptions.

A population model evaluating the consequences of the evolution of double-resistance and tradeoffs on the benefits of two-drug antibiotic treatments

The evolution of antibiotic resistance in microbes poses one of the greatest challenges to the management of human health. Because addressing the problem experimentally has been difficult, research on strategies to slow the evolution of resistance through the rational use of antibiotics has resorted to mathematical and computational models. However, despite many advances, several questions remain unsettled. Here we present a population model for rational antibiotic usage by adding three key features that have been overlooked: 1) the maximization of the frequency of uninfected patients in the human population rather than the minimization of antibiotic resistance in the bacterial population, 2) the use of cocktails containing antibiotic pairs, and 3) the imposition of tradeoff constraints on bacterial resistance to multiple drugs. Because of tradeoffs, bacterial resistance does not evolve directionally and the system reaches an equilibrium state. When considering the equilibrium frequency of uninfected patients, both cycling and mixing improve upon single-drug treatment strategies. Mixing outperforms optimal cycling regimens. Cocktails further improve upon aforementioned strategies. Moreover, conditions that increase the population frequency of uninfected patients also increase the recovery rate of infected individual patients. Thus, a rational strategy does not necessarily result in a tragedy of the commons because benefits to the individual patient and general public are not in conflict. Our identification of cocktails as the best strategy when tradeoffs between multiple-resistance are operating could also be extended to other host-pathogen systems. Cocktails or other multiple-drug treatments are additionally attractive because they allow re-using antibiotics whose utility has been negated by the evolution of single resistance.

On the role of resonance in drug failure under HIV treatment interruption

Background

The application of highly active antiretroviral therapy (HAART) against HIV can reduce and maintain viral load below detection limit in many patients. Continuous HAART, however, can have severe side effects. In this context, structured treatment interruptions (STI) were considered to be a promising strategy. However, using CD4 cell count to guide intermittent therapy starting and stopping points, the SMART study (strategies for management of antiretroviral therapy), revealed that STI were associated with increased risk of AIDS and other complications. Additionally, short-term periodic (e.g. one week on / one week off) interruption therapies have shown virus rebound exceeding a given “failure threshold”, without any evidence for the evolution of drug resistance. Currently, the only hypothesis explaining the failure of STI is the “resonance hypothesis”, which posits that treatment failure is due to a resonance effect between the drug treatment and the viral population. In the present study we used a mathematical model to analyse the parameters affecting the output of drug treatment interruption and the premises of the resonance hypothesis.

Methods

We used a population dynamic model of HIV infection. Simulations and analytical approximations of deterministic and stochastic versions of the model were studied.

Results and Conclusion

The present study examines the roles of the most important parameters affecting the viral rebound, responsible for drug failure. We related these findings to the resonance hypothesis, and showed that the degree of sustainability of damping oscillations present in the model after the acute phase is strongly linked to their amplitude, which determines the resonance level. Stochastic simulations of the same model even revealed sustained oscillations in virus population for small virus population sizes. Given that pronounced viral load oscillations have not been observed in HIV-1 patients, the link between oscillations and resonance level suggests that treatment failure due to a resonance effect is not plausible. Moreover, the failure threshold is attained before the virus population crosses the set point while growing. As the maximum virus population is reached even after the set point is crossed, the role of resonance effects in the context of treatment interruptions cannot explain drug failure.

Heteroclitic peptides enhance human immunodeficiency virus-specific CD8(+) T cell responses

The inability of human immunodeficiency virus (HIV)-specific CD8(+) T cells to durably control HIV replication due to HIV escape mutations and CD8(+) T cell dysfunction is a key factor in disease progression. A few HIV-infected individuals termed elite controllers (EC) maintain polyfunctional HIV-specific CD8(+) T cells, minimal HIV replication and normal CD4(+) T lymphocyte numbers. Thus, therapeutic intervention to sustain or restore CD8(+) T cell responses similar to those persisting in EC could relieve terminal dependence on antiretrovirals. Vaccination with HIV peptides is one approach to achieve this and our objective in this study was to determine whether certain HIV peptide variants display antigenic superiority over the reference peptides normally included in vaccines. Eight peptide sets were generated, each with a reference peptide and six variants harboring conservative or semi-conservative amino acid substitutions at positions predicted to affect T cell receptor interactions without affecting human class I histocompatibililty-linked antigen (HLA) binding. Recognition across peptide sets was tested with >80 HIV-infected individuals bearing the appropriate HLA alleles. While reference peptides were often the most antigenic, cross-reactivity with variants was common and in many cases, peptide variants were superior at stimulating interferon-γ production or selectively enhanced interleukin-2 production. Although such heteroclitic activity was not generalized for all individuals bearing the HLA class I allele involved, these data suggest that heteroclitic peptide variants could improve the efficacy of therapeutic peptide vaccines in HIV infection.

Piecewise HIV virus dynamic model with CD4(+) T cell count-guided therapy: I

The strategies of structured treatment interruptions (STIs) of antiretroviral therapies have been proposed for clinical management of HIV infected patients, but clinical studies on STIs failed to achieve a consistent conclusion for this strategy. To evaluate the STI strategies, in particular, CD4(+) T cell count-guided STIs, and explain these controversial conclusions from different clinical studies, in this paper we propose to use piecewise HIV virus dynamic models to quantitatively explore the STI strategies and investigate their dynamic behaviors. Our analysis results indicate that CD4(+) T cell counts can be maintained above a safe level using the STI with a single threshold or a threshold window. Numerical simulations show that the CD4(+) T cell counts either fluctuate or approach a stable level for a patient, depending on the prescribed upper or lower threshold values. In particular, the CD4(+) T cell counts can be stabilized at a desired level if the threshold policy control is applied. The durations of drug-on and drug-off are very sensitive to the prescribed upper or lower threshold levels, which possibly explains why the on-off strategy with fixed schedule or an STI strategy with frequent switches are associated with the high rate of failure. Our findings suggest that it is critical to carefully choose the thresholds of CD4(+) T cell count and individualize the STIs for each individual patient based on initial CD4(+) T cell counts.

HIV reservoirs and immune surveillance evasion cause the failure of structured treatment interruptions: a computational study

Continuous antiretroviral therapy is currently the most effective way to treat HIV infection. Unstructured interruptions are quite common due to side effects and toxicity, among others, and cannot be prevented. Several attempts to structure these interruptions failed due to an increased morbidity compared to continuous treatment. The cause of this failure is poorly understood and often attributed to drug resistance. Here we show that structured treatment interruptions would fail regardless of the emergence of drug resistance. Our computational model of the HIV infection dynamics in lymphoid tissue inside lymph nodes, demonstrates that HIV reservoirs and evasion from immune surveillance themselves are sufficient to cause the failure of structured interruptions. We validate our model with data from a clinical trial and show that it is possible to optimize the schedule of interruptions to perform as well as the continuous treatment in the absence of drug resistance. Our methodology enables studying the problem of treatment optimization without having impact on human beings. We anticipate that it is feasible to steer new clinical trials using computational models.

Computer simulation of structured treatment interruption for HIV infection

The use of highly active antiretroviral therapy (HAART) for suppression of measurable levels of virus in the body has greatly contributed to restoration and preservation of the immune system in HIV positive patients. However, short and long term problems associated with HAART have led to proposals for alternative treatment strategies for controlling HIV infection. In particular, structured treatment interruptions (STIs) that consist of therapy withdrawal and re-initiation according to specific criteria have been considered. The aim of these STIs was one or both of: (i) to stimulate the immune system to react to HIV, (ii) to allow re-emergence of wild-type virus and thereby reduce problems of drug resistance. However, a number of clinical trials of STIs have shown adverse outcomes for patients under discontinuous therapy, including serious health risks associated with treatment interruptions. In this paper we consider in some detail two of the larger clinical studies, namely, (a) strategies for management of anti-retroviral therapy (SMART); (b) Staccato study. For each of these studies we perform computer simulations of the treatment strategies. These simulations suggest several underlying reasons for the adverse outcomes during treatment interruption. In particular, HIV infection exhibits rapid dynamic load changes, and therefore measurement based treatment regimes need to be carefully designed to avoid large transients in healthy CD4+ T cell count. Furthermore, repeated treatment interruptions may accelerate the emergence of resistant mutant virus and may increase the infection of long term reservoirs such as macrophages which will accelerate progression to AIDS.

Nonlinear observer output-feedback MPC treatment scheduling for HIV

BACKGROUND

Mathematical models of the immune response to the Human Immunodeficiency Virus demonstrate the potential for dynamic schedules of Highly Active Anti-Retroviral Therapy to enhance Cytotoxic Lymphocyte-mediated control of HIV infection.

METHODS

In previous work we have developed a model predictive control (MPC) based method for determining optimal treatment interruption schedules for this purpose. In this paper, we introduce a nonlinear observer for the HIV-immune response system and an integrated output-feedback MPC approach for implementing the treatment interruption scheduling algorithm using the easily available viral load measurements. We use Monte-Carlo approaches to test robustness of the algorithm.

RESULTS

The nonlinear observer shows robust state tracking while preserving state positivity both for continuous and discrete measurements. The integrated output-feedback MPC algorithm stabilizes the desired steady-state. Monte-Carlo testing shows significant robustness to modeling error, with 90% success rates in stabilizing the desired steady-state with 15% variance from nominal on all model parameters.

CONCLUSIONS

The possibility of enhancing immune responsiveness to HIV through dynamic scheduling of treatment is exciting. Output-feedback Model Predictive Control is uniquely well-suited to solutions of these types of problems. The unique constraints of state positivity and very slow sampling are addressable by using a special-purpose nonlinear state estimator, as described in this paper. This shows the possibility of using output-feedback MPC-based algorithms for this purpose.

Treatment simplification in HIV-infected adults as a strategy to prevent toxicity, improve adherence, quality of life and decrease healthcare costs

Since the advent of highly active antiretroviral therapy (HAART), the treatment of human immunodeficiency virus (HIV) infection has become more potent and better tolerated. While the current treatment regimens still have limitations, they are more effective, more convenient, and less toxic than regimens used in the early HAART era, and new agents, formulations and strategies continue to be developed. Simplification of therapy is an option for many patients currently being treated with antiretroviral therapy (ART). The main goals are to reduce pill burden, improve quality of life and enhance medication adherence, while minimizing short- and long-term toxicities, reducing the risk of virologic failure and maximizing cost-effectiveness. ART simplification strategies that are currently used or are under study include the use of once-daily regimens, less toxic drugs, fixed-dose coformulations and induction-maintenance approaches. Improved adherence and persistence have been observed with the adoption of some of these strategies. The role of regimen simplification has implications not only for individual patients, but also for health care policy. With increased interest in ART regimen simplification, it is critical to study not only implications for individual tolerability, toxicity, adherence, persistence and virologic efficacy, but also cost, scalability, and potential for dissemination and implementation, such that limited human and financial resources are optimally allocated for maximal efficiency, coverage and sustainability of global HIV/AIDS treatment.

Changes in lipids and lipoprotein particle concentrations after interruption of antiretroviral therapy

BACKGROUND

The effect of interruption of antiretroviral therapy (ART) on lipoprotein particle subclasses has not been studied. We examined short-term changes in lipids and lipoprotein particles among 332 HIV-infected individuals randomized to interrupt or continue ART in the "Strategies for Management of Antiretroviral Therapy" trial.

METHODS

Lipids and lipoprotein particles measured by nuclear magnetic resonance spectroscopy were compared between randomized groups at month 1; associations with inflammatory and coagulation markers (high sensitivity C-reactive protein; interleukin 6; amyloid A; amyloid P; D-dimer; prothrombin fragment 1 + 2) were assessed.

RESULTS

Compared with continuation of ART, treatment interruption resulted in substantial declines in total, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol, and triglyceride, at month 1 but had little net effect on total/HDL cholesterol ratio [baseline-adjusted mean difference [95% confidence interval (CI)] interruption versus continuation arms: -0.10 (-0.59 to 0.38); P = 0.67]. ART interruption resulted in declines in total, large, and medium very low density lipoprotein (VLDL) particle concentrations (VLDL-p) and total and medium HDL-p. However, there was no change in small HDL-p [baseline-adjusted percentage difference between arms: -4.6% (-13.1%, +5.1% ); P = 0.35], small LDL-p [-5.0% (-16.9%, +8.6%); P = 0.45], or other LDL-p subclasses. Changes in lipid parameters on ART interruption did not differ according to baseline ART class (protease inhibitor versus non-nucleoside reverse transcriptase inhibitor) but were negatively associated both with changes in HIV viral load and with changes in inflammatory and coagulation markers, particularly D-dimer.

CONCLUSIONS

These results suggest that ART interruption does not favorably influence overall lipid profile: there was little net effect on total/HDL cholesterol ratio, and no change in small LDL-p or small HDL-p, the lipoprotein particle subclasses most consistently linked to coronary risk. Short-term declines in lipid parameters after ART interruption were not associated with class of ART and may be linked to increases in viral replication, inflammation and coagulation.

[AIDS Study Group/Spanish AIDS Plan consensus document on antiretroviral therapy in adults with human immunodeficiency virus infection (updated January 2010)]

OBJECTIVE

This consensus document is an update of antiretroviral therapy recommendations for adult patients with human immunodeficiency virus infection.

METHODS

To formulate these recommendations a panel made up of members of the Grupo de Estudio de Sida (Gesida, AIDS Study Group) and the Plan Nacional sobre el Sida (PNS, Spanish AIDS Plan) reviewed the advances in the current understanding of the pathophysiology of human immunodeficiency virus (HIV) infection, the efficacy and safety of clinical trials, and cohort and pharmacokinetic studies published in biomedical journals or presented at scientific meetings. Three levels of evidence were defined according to the data source: randomized studies (level A), cohort or case-control studies (level B), and expert opinion (level C). The decision to recommend, consider or not to recommend ART was established in each situation.

RESULTS

Currently, the treatment of choice for chronic HIV infection is the combination of three drugs of two different classes, including 2 nucleosides or nucleotide analogs (NRTI) plus 1 non-nucleoside (NNRTI) or 1 boosted protease inhibitor (PI/r), but other combinations are possible. Initiation of ART is recommended in patients with symptomatic HIV infection. In asymptomatic patients, initiation of ART is recommended on the basis of CD4 lymphocyte counts, plasma viral load and patient co-morbidities, as follows: 1) therapy should be started in patients with CD4 counts below 350 cells/microl; 2) When CD4 counts are between 350 and 500 cells/microl, therapy should be started in case of cirrhosis, chronic hepatitis C, high cardiovascular risk, HIV nephropathy, HIV viral load above 100,000 copies/ml, proportion of CD4 cells under 14%, and in people aged over 55; 3) Therapy should be deferred when CD4 are above 500 cells/microl, but could be considered if any of previous considerations concurs. Treatment should be initiated in case of hepatitis B requiring treatment and should be considered for reduce sexual transmission. The objective of ART is to achieve an undetectable viral load. Adherence to therapy plays an essential role in maintaining antiviral response. Therapeutic options are limited after ART failures but undetectable viral loads maybe possible with the new drugs even in highly drug experienced patients. Genotype studies are useful in these situations. Drug toxicity of ART therapy is losing importance as benefits exceed adverse effects. Criteria for antiretroviral treatment in acute infection, pregnancy and post-exposure prophylaxis are mentioned as well as the management of HIV co-infection with hepatitis B or C.

CONCLUSIONS

CD4 cells counts, viral load and patient co-morbidities are the most important reference factors to consider when initiating ART in asymptomatic patients. The large number of available drugs, the increased sensitivity of tests to monitor viral load, and the ability to determine viral resistance is leading to a more individualized therapy approach in order to achieve undetectable viral load under any circumstances.

The effects of intermittent, CD4-guided antiretroviral therapy on body composition and metabolic parameters

OBJECTIVE

To assess the effects of decreased antiretroviral therapy exposure on body fat and metabolic parameters.

DESIGN

Substudy of the Strategies for Management of Anti-Retroviral Therapy study, in which participants were randomized to intermittent CD4-guided [Drug Conservation (DC) group] or to continuous [Viral Suppression (VS) group] antiretroviral therapy.

METHODS

Participants at 33 sites were coenrolled in the Strategies for Management of Anti-Retroviral Therapy Body Composition substudy. Regional fat was assessed annually by whole-body dual-energy X-ray absorptiometry and abdominal computed tomography. Fasting metabolic parameters were assessed at months 4, 8, and annually. Treatment groups were compared for changes in fat and metabolic markers using longitudinal mixed models.

RESULTS

Two hundred and seventy-five patients were randomized to the DC (n = 142) or VS (n = 133) group and followed for a median of 2.0 years. By month 12, limb fat (DC-VS difference 9.8%, 95% confidence interval 3.5-16.1; P = 0.003) and subcutaneous abdominal fat (DC-VS difference 14.3 cm, 95% confidence interval -0.1 to 28.7; P = 0.05) increased in the DC group. There was no treatment difference in visceral abdominal fat (DC-VS difference -2.1%, 95% confidence interval -13.5 to 9.4; P = 0.72). Lipids significantly decreased in the DC group by month 4 and treatment differences persisted throughout follow-up (P < or = 0.001). By 12 months, hemoglobin A1C increased in the DC (+0.3%) and remained stable in the VS group (P = 0.003); the treatment difference remained significant throughout follow-up (P = 0.02).

CONCLUSION

After 12 months, intermittent antiretroviral therapy increased subcutaneous fat, had no effect on visceral abdominal fat, decreased plasma lipids, and increased hemoglobin A1C compared with continuous antiretroviral therapy.

Adherence to HAART: processes explaining adherence behavior in acceptors and non-acceptors

In order to explore and clarify the underlying processes which lead to (non)-adherence behavior in patients treated with highly active antiretroviral therapy (HAART), a qualitative study was conducted. Thirty-seven in-depth interviews were held with 30 Caucasian HIV-positive patients. Additional data were collected by diaries kept by some participants. The analysis took place in a cyclic process; selection of themes was alternated with input of new material. Adherence to HAART is mainly influenced by the experience of being HIV positive. Acceptance or non-acceptance of HIV leads to one of two basic stances toward adherence: "being determined to be adherent" or "medication is subordinate to other priorities in life". This stance determines the commitment to therapy and influences how patients cope with adherence. Patients who are determined to be adherent find solutions to adherence problems. Patients who are not determined to be adherent solve problems only if the solution does not compromise important aspects of their lives. Insight is provided into the manner in which prevalent themes; "start of HAART", "attitude toward medication", "HAART in daily life", "contextual factors", "health and HAART" and "being informed", influence adherence behavior. Before starting HAART the focus should be on helping the patient to accept HIV as a part of life. The findings need to be taken into account in adherence-promoting interventions.

Short-cycle therapy in adolescents after continuous therapy with established viral suppression: the impact on viral load suppression

This was a proof-of-principle study to evaluate the impact of short cycle therapy (SCT; 4 days on/3 days off) in adolescents and young adults with good viral suppression on a protease inhibitor-based antiretroviral regimen. Subjects were recruited by the Adolescent Trials Network for HIV/AIDS Interventions and the Pediatric AIDS Clinical Trials Group. Subjects were infected either through perinatal/early childhood transmission or later via risk behaviors. All subjects were required to have at least 6 months of documented viral suppression below 400 copies/ml plus a preentry value below 200 copies/ml and an entry CD4+ T cell count above 350 cells/mm3. Of the 32 subjects enrolled, 12 (37.5%) had confirmed viral load rebound >400 copies, with 18 subjects (56%) coming off for any reason. The majority of subjects resuppressed when placed back onto continuous therapy using the same agents. Although no difference was found in virologic rebound rates between the early and later transmission groups, those infected early in life had higher rates of coming off SCT for any reason. There was no impact of SCT on the CD4+ T cell counts in those who remained on study or those who came off SCT for any reason. Subjects demonstrated good adherence to the SCT regimen. This study suggests that further evaluation of SCT may be warranted in some groups of adolescents and young adults infected with HIV.

Simplification strategies to reduce antiretroviral drug exposure: progress and prospects

Current U.S. guidelines for initial therapy of HIV type-1 (HIV-1) infection recommend daily, lifelong treatment with a combination of three antiretroviral drugs consisting of two nucleoside analogue reverse transcriptase inhibitors and a non-nucleoside reverse transcriptase inhibitor or a protease inhibitor. Although this approach has been successful in reducing morbidity and mortality from HIV-1 infection, concerns remain about adverse events from chronic drug exposure, the requirement for daily medication adherence, the risk of HIV-1 drug resistance and high treatment costs. The availability of antiretrovirals that are coformulated and dosed once daily have reduced pill burden and have simplified dosing schedules, but have not lowered drug exposure or cost. These limitations have stimulated research into drug-sparing strategies including intermittent therapy and simplified maintenance regimens. Randomized clinical trials have shown greater mortality with intermittent therapy compared with continuous therapy leading to rejection of this strategy. Pilot studies of simplified maintenance therapy with a ritonavir-boosted protease inhibitor alone have shown more promise, although concerns remain. This article reviews progress in the simplification of antiretroviral therapy, recent clinical trial results and prospects for the future.

Simplification Strategies to Reduce Antiretroviral drug Exposure: Progress and Prospects

Current US guidelines for initial therapy of HIV type-1 (HIV-1) infection recommend daily, lifelong treatment with a combination of three antiretroviral drugs consisting of two nucleoside analogue reverse transcriptase inhibitors and a non-nucleoside reverse transcriptase inhibitor or a protease inhibitor. Although this approach has been successful in reducing morbidity and mortality from HIV-1 infection, concerns remain about adverse events from chronic drug exposure, the requirement for daily medication adherence, the risk of HIV-1 drug resistance and high treatment costs. The availability of antiretrovirals that are coformulated and dosed once daily have reduced pill burden and have simplified dosing schedules, but have not lowered drug exposure or cost. These limitations have stimulated research into drug-sparing strategies including intermittent therapy and simplified maintenance regimens. Randomized clinical trials have shown greater mortality with intermittent therapy compared with continuous therapy leading to rejection of this strategy. Pilot studies of simplified maintenance therapy with a ritonavir-boosted protease inhibitor alone have shown more promise, although concerns remain. This article reviews progress in the simplification of antiretroviral therapy, recent clinical trial results and prospects for the future.

Immunological responses and long-term treatment interruption after human immunodeficiency virus type 1 (HIV-1) lipopeptide immunization of HIV-1-infected patients: the LIPTHERA study

We studied the time course of immunological and virological markers after highly active antiretroviral therapy (HAART) interruption in chronically human immunodeficiency virus type 1 (HIV-1)-infected patients immunized with an HIV lipopeptide preparation. In a prospective open pilot study, 24 HIV-1-infected HAART-treated patients with undetectable plasma viral loads (pVLs) and CD4(+) T-cell counts above 350/mm(3) were immunized at weeks 0, 3, and 6 with a candidate vaccine consisting of six HIV lipopeptides. At week 24, patients with pVLs of <1.7 log(10) copies/ml were invited to stop taking HAART. Antiretroviral therapy was resumed if the pVL rose above 4.47 log(10) copies/ml and/or if the CD4(+) cell count fell below 250/mm(3). Immunological and virologic parameters were studied before and after HAART interruption. The median baseline and nadir CD4(+) cell counts were 482 (interquartile range [IQR], 195 to 826) and 313 (IQR, 1 to 481)/mm(3), respectively. New specific CD8(+) cell responses to HIV-1 epitopes were detected after immunization in 13 (57%) of 23 assessable patients. Twenty-one patients were evaluated 96 weeks after HAART interruption. The median time to pVL rebound was 4 weeks (IQR, 2 to 6), and the median peak pVL was 4.26 (IQR, 3 to 5) log(10) copies/ml. Thirteen of these 21 patients resumed HAART a median of 60 weeks after immunization (IQR, 9.2 to 68.4 weeks), when the median pVL was 4.8 (IQR, 2.9 to 5.7) log(10) copies/ml and the median CD4(+) cell count was 551 (IQR, 156 to 778)/mm(3). Eight patients were still off therapy at 96 weeks, with a median pVL of 4 (IQR, 1.7 to 4.6) log(10) copies/ml and a median CD4(+) cell count of 412 (IQR, 299 to 832)/mm(3). No clinical disease progression had occurred. Despite the lack of a control arm, these findings warrant a randomized study of therapeutic vaccination with HIV lipopeptides followed by long-term HAART interruption in AIDS-free chronically infected patients.

A randomised control trial of structured interrupted generic antiretroviral therapy versus continuous therapy in HIV-infected individuals in Southern India

This randomised control trial, conducted in Chennai, India, compared structured interrupted therapy (SIT) and continuous therapy (CT) in relation to immunologic and virologic outcomes, adverse events (AEs) and cost of therapy. ART-naïve adult HIV1-infected participants with CD4 counts 50-350 cells/mm(3), and plasma viral load (PVL)>5000 copies/mL were enrolled and placed on Indian-manufactured generic ART: zidovudine(AZT)/stavudine(d4T)+lamivudine(3TC)+efavirenz(EFV). After at least six months of continuous therapy, subjects were randomised to SIT (one-week-on/one-week-off cycles) or CT. The primary end-point was the proportion of subjects maintaining CD4>200 cells/mm(3) at six and 12 months after randomisation. Secondary end-points were effective viral suppression (PVL<400 copies/mL), AEs and cost. All analyses used intention-to-treat methodology. Of 40 participants (69% male; mean age 36+/-7; median baseline CD4 and PVL: 162 cell/mm(3)and 259,000 copies/mL), 17 were randomised to SIT and 18 to CT. At randomisation, median CD4s for SIT and CT were 378 cells/mm(3) and 357 cells/mm(3), respectively. All participants had PVL<400 copies/mL at time of randomisation. Median CD4 six months after randomisation was 498 cells/mm(3) and 417 cells/mm(3) for SIT and CT respectively. All participants had CD4>200 cells/mm(3). One participant on CT and two on SIT had sustained PVL>400 copies/mL. There were no serious AEs or deaths. Structured interrupted therapy cost was half of CT. Structured interrupted therapy was effective at maintaining CD4 above 200 cells/mm(3). Adverse events were comparable in both groups, with 50% reduction in cost for SIT. Further research on such strategies may benefit resource-constrained settings.

Physiological levels of virion-associated human immunodeficiency virus type 1 envelope induce coreceptor-dependent calcium flux

Human immunodeficiency virus (HIV) entry into target cells requires the engagement of receptor and coreceptor by envelope glycoprotein (Env). Coreceptors CCR5 and CXCR4 are chemokine receptors that generate signals manifested as calcium fluxes in response to binding of the appropriate ligand. It has previously been shown that engagement of the coreceptors by HIV Env can also generate Ca(2+) fluxing. Since the sensitivity and therefore the physiological consequence of signaling activation in target cells is not well understood, we addressed it by using a microscopy-based approach to measure Ca(2+) levels in individual CD4(+) T cells in response to low Env concentrations. Monomeric Env subunit gp120 and virion-bound Env were able to activate a signaling cascade that is qualitatively different from the one induced by chemokines. Env-mediated Ca(2+) fluxing was coreceptor mediated, coreceptor specific, and CD4 dependent. Comparison of the observed virion-mediated Ca(2+) fluxing with the exact number of viral particles revealed that the viral threshold necessary for coreceptor activation of signaling in CD4(+) T cells was quite low, as few as two virions. These results indicate that the physiological levels of virion binding can activate signaling in CD4(+) T cells in vivo and therefore might contribute to HIV-induced pathogenesis.

Immunological and virological effects of structured treatment interruptions following exposure to hydroxyurea plus didanosine

Both hydroxyurea (HU) and structured treatment interruptions (STI) have been investigated as therapeutic approaches to enhance immune responses in chronically HIV-infected individuals. HIV-specific T cell responses as well as T cell activation were analyzed longitudinally in 31 HIV-infected individuals who had been treated for the prior 12 months with didanosine (ddI) plus HU and thereafter completed three STI cycles consisting of 2 months off and 2 months on ddI-HU. Similar increases in plasma HIV-RNA were seen in each of the three cycles off therapy, whereas CD4 counts remained fairly stable along the study period. T cell activation paralleled the evolution of plasma HIV-RNA during the first STI cycle and waned afterward. At baseline most patients presented a high level of CD8+ responses to different HIV peptide pools and 23% of them had CD4+ responses to Gag and/or Env. The level of CD8+ responses against each pool was stable and did not increase during STI cycles, while CD4 responses tended to decline. However, the contribution of Nef-specific response to the total CD8 response tended to increase. In a multivariate model, both a higher baseline plasma HIV-RNA and a higher level of Nef-specific response contribution to the total CD8+ response were independently associated with lower plasma HIV-RNA increases during each of the three STI cycles. Nef-specific CD8+ responses might contribute to a better virological control of HIV replication following treatment interruptions in HIV-infected individuals and might be boosted by the immunomodulatory effect of HU.

A pilot study evaluating time to CD4 T-cell count <350 cells/mm(3) after treatment interruption following antiretroviral therapy +/- interleukin 2: results of ACTG A5102

BACKGROUND

Although an intermittent antiviral treatment (ART) strategy may limit long-term toxicity and cost, there is concern about the risk for virologic failure, selection of drug resistance mutations, and disease progression. By boosting CD4 T-cell counts, interleukin 2 (IL-2) could safely prolong the duration of treatment interruption (TI) in a CD4-driven strategy.

METHODS

The AIDS Clinical Trials Group (ACTG) study A5102 evaluated 3 cycles of IL-2 before TI, on clinical and immunologic outcomes, using a CD4 T-cell count of <350 cells/mm as the threshold for restarting ART. Forty-seven HIV-infected subjects on potent ART with CD4 T-cell counts of > or =500 cells/mm or more and HIV RNA levels of less than 200 copies/mL were randomized to arm A (ART + three 5-day cycles of IL-2 at 4.5 million U, Sc, BID every 8 weeks, n = 23) or arm B (ART alone, n = 24) for 18 weeks (step 1). At the end of step 1, subjects with a CD4 T-cell count of > or =500 cells/mm or more stopped ART until a CD4 count of <350 cells/mm (step 2). CD4 T-cell count, time to return of viremia, and the emergence of drug resistance mutations after TI were compared between study arms.

RESULTS

IL-2 recipients maintained higher CD4 counts during TI for 48 weeks with a waning of the CD4 effect by 72 weeks. A sustained CD4 T-cell count of more than 350 cells/mm and more durable TI were associated with a higher nadir CD4 T-cell count before ART and higher naive CD4 T-cell count at entry. After TI, a higher viral set point and drug resistance mutations at virologic rebound were associated with a shorter time to CD4 T-cell count of less than 350 cell/mm. There were no differences in the magnitude of virologic rebound (at week 8 of step 2, median log10 HIV RNA level was 4.23 for arm A and 4.21 for arm B) or the steady-state HIV-1 RNA level after week 8.

CONCLUSIONS

IL-2 before TI did not prolong time to CD4 of less than 350 cells/mm. A TI strategy utilizing a CD4 T-cell threshold of less than 350 cells/mm for restarting ART appears generally safe with most subjects in both arms remaining off ART for more than 1 year. Implications of our results for TI strategies include the potential advantage of starting ART at higher CD4 T-cell levels while avoiding any drug resistance and evaluating immunomodulators or drugs to reduce T-cell activation and HIV-1 RNA rebound during the TI.

The role of hydroxyurea in enhancing the virologic control achieved through structured treatment interruption in primary HIV infection: final results from a randomized clinical trial (Pulse)

BACKGROUND

Structured treatment interruptions (STIs) have been postulated to improve virologic control in primary HIV infection (PHI) by stimulating HIV-specific T-lymphocyte immunity. The addition of hydroxyurea (HU) may reduce viral production from activated CD4 cells.

METHODS

Patients with PHI received a standardized antiretroviral (ARV) regimen consisting of indinavir 800 mg twice daily (BID), ritonavir 100 mg BID, didanosine 400 mg (QD), and either stavudine 40 mg BID or lamivudine 150 mg BID, for up to 12 months and were randomized to HU 500 mg BID or not. If viral suppression (<50 copies/mL) was achieved, up to 3 STIs were undertaken. Two ARV cycles were allowed after each interruption if virologic rebound to more than 5000 RNA copies/mL occurred. Treatment success was defined as maintaining viral loads below 5000 copies/mL for 6 months after ARV interruption.

RESULTS

Sixty-eight male homosexual patients were randomized: 35 to ARV + HU and 33 to ARV-alone. Median baseline HIV RNA was 5.73 log10 copies/mL, and median CD4 T-lymphocyte count was 517 cells/microL. Treatment success was not significantly different between those receiving and not receiving HU, with 9 (26%) and 9 (27%), respectively, maintaining viral load at less than 5000 copies/mL in each group (P = 0.88). Virologic control was achieved by 11 (19%) of 59 after 1 STI, 1 (2%) of 41 after 2 STIs, and 6 (17%) of 36 after the third STI. Serious adverse events were recorded for 9 (26%) of 35 of patients using HU and 3 (9%) of 33 in the ARV-only group (P = 0.28). CD4 cell increases were significantly blunted for the HU group compared to the ARV-alone group after the initial treatment phase (+101 cells vs. +196 cells, respectively, P = 0.006).

CONCLUSIONS

Hydroxyurea was not found to be beneficial when used in association with STIs in patients during PHI.

Structured treatment interruptions with tenofovir monotherapy for simian immunodeficiency virus-infected newborn macaques

We demonstrated previously that prolonged tenofovir treatment of infant macaques, starting early during infection with virulent simian immunodeficiency virus (SIVmac251), can lead to persistently low or undetectable viremia even after the emergence of mutants with reduced in vitro susceptibility to tenofovir as a result of a K65R mutation in reverse transcriptase; this control of viremia was demonstrated to be mediated by the generation of effective antiviral immune responses. To determine whether structured treatment interruptions (STI) can induce similar immunologic control of viremia, eight newborn macaques were infected with highly virulent SIVmac251 and started on a tenofovir STI regimen 5 days later. Treatment was withdrawn permanently at 33 weeks of age. All animals receiving STI fared much better than 22 untreated SIVmac251-infected infant macaques. However, there was a high variability among animals in the viral RNA set point after complete drug withdrawal, and none of the animals was able to achieve long-term immunologic suppression of viremia to persistently low levels. Early immunologic and viral markers in blood (including the detection of the K65R mutation) were not predictive of the viral RNA set point after drug withdrawal. These results, which reflect the complex interactions between drug resistance mutations, viral virulence, and drug- and immune-mediated inhibition of virus replication, highlight the difficulties associated with trying to develop STI regimens with predictable efficacy for clinical practice.

CD4-guided structured antiretroviral treatment interruption strategy in HIV-infected adults in west Africa (Trivacan ANRS 1269 trial): a randomised trial

BACKGROUND

Structured treatment interruptions of highly-active antiretroviral therapy (HAART) might be particularly relevant for sub-Saharan Africa, where cost-saving strategies could help to increase the number of patients on HAART. We did a randomised trial of structured treatment interruption in Abidjan, Côte d'Ivoire.

METHODS

HIV-infected adults were randomised to receive continuous HAART (CT), CD4-guided HAART (CD4GT) with interruption and reintroduction thresholds at 350 and 250 cells per mm3, respectively, or 2-months-off, 4-months-on HAART. Primary endpoints were death and severe morbidity (any WHO stage 3 or 4 events and any events leading to death) at month 24. We report data from the CT and CD4GT groups until Oct 31, 2005, when the data safety monitoring board recommended to prematurely stop the CD4GT arm. Analyses were intention-to-treat. This study is registered at ClinicalTrials.gov, number NCT00158405.

RESULTS

326 adults (median CD4 count nadir 272 per mm3) were randomised to the CT or CD4GT groups and followed up for median of 20 months. Incidence of mortality (per 100 person-years) was not different between groups (CT 0.6, CD4GT 1.2; p=0.57). Incidence of severe morbidity (per 100 person-years) was higher in the CDG4T group (17.6) than in the CT group (6.7; p=0.001). The most frequent severe events were invasive bacterial diseases. 79% of severe morbidity episodes occurred in patients with CD4 count 200-500 per mm3.

CONCLUSION

Patients on CD4GT had severe morbidity rates 2.5-fold higher than those on CT. This difference was mainly due to high rates of common diseases in patients with CD4 count 200-500 per mm3. This CD4-guided structured treatment interruption strategy should not be recommended in Abidjan.

Immunological recovery and antiretroviral therapy in HIV-1 infection

Potent antiretroviral therapy has dramatically improved the prognosis of patients infected with HIV-1. Primary and secondary prophylaxis against Pneumocystis carinii, Mycobacterium avium, cytomegalovirus, and other pathogens can be discontinued safely once CD4 cell counts have increased beyond pathogen-specific thresholds. Approximately one-third of individuals receiving antiretroviral therapy will not reach CD4 cell counts above 500 cells per muL after 5 years despite continuous suppression of plasma HIV-1 RNA. Whether this failure represents a risk factor for the long-term incidence of opportunistic diseases--eg, tuberculosis or malignancies--remains uncertain. We describe the time course of CD4 cell concentrations in patients whose plasma HIV-1 RNA is durably suppressed by antiretroviral therapy, in patients with incomplete suppression of plasma HIV-1 RNA, and during treatment interruptions. In addition, immune reconstitution disease, an inflammatory syndrome associated with immunological recovery occurring days to weeks after the start of antiretroviral therapy, is briefly described.

Immunovirologic consequences and safety of short, non-structured interruptions of successful antiretroviral treatment

OBJECTIVES

The aim was to evaluate the safety of short antiretroviral treatment interruptions and their virologic and immunologic consequences in HIV-infected adults on highly active antiretroviral treatment (HAART) with suppressed viral replication. The viral efficacy upon reintroduction was also evaluated.

PATIENTS AND METHODS

All patients with undetectable viral load while on HAART were prospectively followed to detect any treatment interruption. We analysed viral and cellular kinetics, incidence of resistance mutations, clinical outcome and results after therapy resumption.

RESULTS

Twenty patients were included, mean time since HIV diagnosis was 95 months and time with undetectable viral load 16 months. Treatment was interrupted because of adverse effects, cancer, tuberculosis or patient will. Treatment was reintroduced after 4 weeks using, if possible, the same combination. HIV viral load was detectable on day 28 after interruption in 18 patients (90%). Median of CD4 cell count (p25-p75) decreased from 478/mm3 (96-716) to 257/mm3 (118-663) (p=0.5). Resistance mutations were found in 9 patients (45%) after interruptions. Treatment was reintroduced in 14 patients; all of them achieved viral suppression.

CONCLUSIONS

In patients receiving HAART who have undetectable viral load, an interruption, no longer than 4 weeks, due to any intercurrent problem seems to be safe. Response to resumption can usually be achieved. Due to the frequent development of resistance, a genotypic test during interruption might be helpful.

Role of parametric resonance in virological failure during HIV treatment interruption therapy

We present a novel hypothesis that could explain virological failure to structured treatment interruptions (STI). We analysed a classic mathematical model of HIV within-host viral dynamics and found that non-linear parametric resonance occurs when STI are added to the model; resonance is observed as virological failure. We simulated clinical trial data and calculated patient-specific resonant spectra. We gained two important insights. First, within an STI trial, patients who begin with similar viral loads can be expected to show very different virological responses as a result of resonance. Second, and more importantly, virological failure is not simply due to STI or patients' characteristics; instead it is the result of complex interaction between STI and the patient's viral dynamics. Hence, our analyses show that no universal regimen with periodic interruptions will be effective for all patients.

Effect of long-cycle structured intermittent versus continuous HAART on quality of life in patients with chronic HIV infection

OBJECTIVE

To examine the effect of repeated, long-cycle structured intermittent versus continuous HAART on health-related quality of life (HRQL) and symptom distress in patients with chronic HIV infection and plasma HIV RNA of less than 50 copies/ml.

DESIGN

Prospective survey of adult patients (n = 46) enrolled in a randomized clinical trial evaluating intermittent versus continuous HAART on immunological and virologic parameters. Patients (n = 23) randomized to structured intermittent therapy received serial cycles of 4 weeks on/8 weeks off HAART.

OUTCOME MEASURES

HRQL was measured by the physical and mental health summary scores of the Medical Outcomes Study HIV Health Survey (MOS-HIV). Symptom distress was measured by the Symptom Distress Scale. Patients completed initial questionnaires prior to randomization and at weeks 4, 12, and 40 of the trial via a touch screen computer in an outpatient clinic.

RESULTS

Baseline demographic and clinical characteristics were equivalent in both treatment groups. Although the mental health summary score declined significantly over time for the structured intermittent group, linear mixed modeling ANOVA indicated no significant difference across time for MOS-HIV summary and Symptom Distress Scale scores between the two treatment arms.

CONCLUSION

In this small sample, repeated long-cycle structured intermittent therapy may not provide HRQL or symptom distress advantage compared to continuous HAART in patients with chronic HIV infection over 10 months of treatment. Further research in a heterogenous chronic HIV population and longer follow-up period is warranted.

Structured intermittent interruption of chronic HIV infection treatment with highly active antiretroviral therapy: effects on leptin and TNF-alpha

The changes in nutritional parameters and adipocytokines after structured intermittent interruption of highly active antiretroviral treatment of patients with chronic HIV infection are analyzed. Twenty-seven patients with chronic HIV infection (median CD4+ T cell count/microl: nadir, 394; at the beginning of structured interruptions, 1041; HIV viral load: nadir, 41,521 copies/ml; at the beginning of structured interruptions <50 copies/ml; median time of previous treatment: 60 months) were evaluated during three cycles of intermittent interruptions of therapy (8 weeks on/4 weeks off). CD4+ T cell count, HIV viral load, anthropometric measures, and serum concentrations of triglycerides, cholesterol, leptin, and tumor necrosis factor and its soluble receptors I and II were determined. After the three cycles of intermittent interruptions of therapy, no significant differences in CD4+ T cell count/microl, viral load, or serum concentrations of cholesterol or triglycerides with reference to baseline values were found. A near-significant higher fatty mass (skinfold thicknesses, at the end, 121 mm, at the beginning, 100 mm, p = 0.100), combined with a significant increase of concentration of leptin (1.5 vs. 4.7 ng/ml, p = 0,044), as well as a decrease in serum concentrations of soluble receptors of tumor necrosis factor (TNFRI, 104 vs. 73 pg/ml, p = 0.022; TNFRII 253 vs. 195 pg/ml, p = 0.098) were detected. Structured intermittent interruption of highly active antiretroviral treatment of patients with chronic HIV infection induces a valuable positive modification in markers of lipid turnover and adipose tissue mass.

Evolutionary dynamics of HIV-1 and the control of AIDS

Human immunodeficiency viruses (HIV) have exhibited an extraordinary capacity for genetic change, exploring new evolutionary space after each transmission to a new host. This presents a great challenge to the prevention and management of HIV-1 infection. At the same time, the relentless diversification of HIV-1, developing as it does under the constraints imposed by the human immune system and other selective forces, contains within it information useful for understanding HIV epidemiology and pathogenesis. Comparing the sheer mutational potential of HIV with actual data representing viral lineages that can survive selection suggests that HIV does not have unlimited capacity for change. Rather, clinical and bioinformatic data suggest that, even in the most diverse gene of the most highly variable organism, natural selection places severe limits on the portion of amino acid sequence space that ensures viability. This suggests some optimism for those attempting to identify sets of antigens that can generate effective humoral and cellular immune responses against HIV.

High Thymic Volume Is Associated With Viral Replication and Immunologic Impairment Only Early After HAART Interruption in Chronic HIV Infection

One of the strategies that has been investigated to reduce antiretroviral treatment toxicity in patients infected with human immunodeficiency virus (HIV) is structured treatment interruption (STI). Our aim was to analyze early viral and immune dynamics after interruption of highly active antiretroviral therapy (HAART) and to determine whether thymic function-related markers play a role in preventing CD4 count decline caused by increased viral replication. This was a prospective study of an open cohort of 47 HIV-infected patients with a median 969 CD4 count and prolonged viral suppression. They were followed every 4 weeks though week 24. Thymic volume and TREC level were analyzed at baseline. Increased thymic volume was associated with higher plasma viral load and greater CD4 count decline early after interruption. Three virologic patterns were observed: rapid/high (RH), delayed/high (DH), and low/slow (LS) viral replication. RH correlated with higher thymic volume at baseline and with higher CD4 count decline at week 4. Patients with greater thymic volume was associated with an immune and virologic impairment only early after interruption, probably because of infection of the increased number of available target cells. As the long-term consequences of these observations are unknown, the safety of treatment interruption must be further studied.

Structured treatment interruptions (STI) in chronic suppressed HIV infection in adults

BACKGROUND

Although antiretroviral treatment (ART) has led to a decline in morbidity and mortality of HIV-infected patients in developed countries, it has also presented challenges. These challenges include increases in pill burden; adherence to treatment; development of resistance and treatment failure; development of drug toxicities; and increase in cost of HIV treatment and care. These issues stimulated interest in investigating the short-term and long-term consequences of discontinuing ART, thus providing support for research in structured treatment interruptions (STI). Structured treatment interruptions of antiretroviral treatment involve taking supervised breaks from ART. STI are defined as one or more planned, timing pre-specified, cyclical interruptions in ART. STI are attempted in monitored clinical settings in eligible participants. STI have generated hopes of reducing drug toxicities, decreasing costs and total time on treatment in HIV-positive patients. The first STI was attempted in the case of a patient in Germany, who later permanently discontinued treatment. This successful anecdotal case report led to several trials on STI worldwide.

OBJECTIVES

The objective of this systematic review was to assess the effects of structured treatment interruptions (STI) of antiretroviral therapy (ART) in the management of chronic suppressed HIV infection, using all available high-quality studies.

SEARCH STRATEGY

Nine databases covering the time period from January 1996 to March 2005 were searched. Bibliographies were scanned and experts contacted in the field to identify unpublished research and ongoing trials. Two reviewers independently extracted data, and evaluated study eligibility and quality. Disagreements were resolved in consultation with a third reviewer. Data from 33 studies were included in the review.

SELECTION CRITERIA

STI is a planned, timing pre-specified experimental intervention. In our review, we decided to include all available intervention trials in HIV-infected patients, with or without control groups. We reviewed evidence from 18 randomized and non-randomized controlled trials, and 15 single arm trials. Single arm trials were included because these pilot studies made significant contribution to the early development and refutation of hypotheses in STI.

DATA COLLECTION AND ANALYSIS

Trials included in this review varied in study participants, methodology and reported inconsistent measures of effect. Due to this heterogeneity, we did not attempt to meta-analyse them. Results were tabulated and a qualitative systematic review was done

MAIN RESULTS

For the purpose of this review, STI strategies were classified either as a timed-cycle STI strategy or a CD4-guided STI strategy. In timed-cycle STI strategy, a predetermined period of fixed duration (e.g. one week, one month) off ART was attempted followed by resumption of ART, while closely monitoring changes in CD4 levels and viral load levels. Predetermined criteria for interruption and resumption were laid out in this strategy. Timed-cycle STI fell out of favor due to reports of development of resistance in many studies. Moreover, there were no significant immunological and virological benefits, and no reduction in toxicities, reported in these studies. In CD4-guided STI strategy, ART was interrupted for variable durations guided by CD4 levels. Participants with high nadir CD4 levels qualified for this approach. A reduction in costs of ART, a reduction in mutation, and a better tolerability of this CD4-guided STI strategy was reported. However, concerns about long-term safety of this strategy on immunological, virological, and clinical outcomes were also raised.

AUTHORS' CONCLUSIONS

Timed-cycle STI have not been proven to be safe in the short term. Although CD4-guided STI strategy has reported favorable outcomes in the short term, the long-term safety, efficacy and tolerability of this strategy has not been fully investigated. Based on the studies we reviewed, the evidence to support the use of timed-cycle STI and CD4-guided STI cycles as a standard of care in the management of chronic suppressed HIV infection is inconclusive.

Discontinuation of antiretroviral therapy in patients with chronic HIV infection: clinical, virologic, and immunologic consequences

To investigate the clinical, virologic and immunologic consequences of planned treatment interruptions in chronically HIV-infected patients. One hundred forty-one patients with undetectable viral load for at least 6 months and CD4+ T cells count greater than 500 per microliter were recruited. Their antiretroviral therapy was stopped and clinical, analytic, virologic, and immunologic data were recorded at baseline, during discontinuation, and after restarting treatment. Viral load rebound after discontinuation in 137 (97%) patients, and was similar to prehighly active antiretroviral therapy (HAART) levels. A rapid decrease in CD4+ T-cell count (median, 240 cells per microliter), was observed in the first 3 months in all patients, with pronounced differences between them. After a median follow-up of 36 months, 45.5% patients were still without therapy. Factors related to a more severe decline were a prior lower CD4+ T nadir (<200 cells per microliter) before starting HAART, a greater increase (>500 cells per microliter) with it, a higher CD4+ T-cell count before interruption (>800 cells per microliter) and a higher viral load rebound after it. The increase in CD4+ T-cell counts after reinitiation was slower than the decline and only 55% of patients have regained the preinterruption levels at 12 months of follow- up. Twelve infectious events were registered. Treatment failure related to drug resistance was observed in two patients. Planned treatment interruptions may be safe in selected patients with previous CD4+ T cell nadir greater than 200 cells per microliter and pre-HAART VL less than 55.000 copies per milliliter, but should be not recommended in patients with the prognostic factors related to a rapid decline described in this study. Furthermore, there is a considerable concern about the development of drug resistance and the possibility of an incomplete immune reconstitution after the treatment interruption in some patients.

A model predictive control based scheduling method for HIV therapy

Recently developed models of the interaction of the human immune system and the human immunodeficiency virus (HIV) suggest the possibility of using interruptions of highly active anti-retroviral therapy (HAART) to simulate a therapeutic vaccine and induce cytotoxic lymphocyte (CTL) mediated control of HIV infection. We have developed a model predictive control (MPC) based method for determining optimal treatment interruption schedules for this purpose. This method provides a clinically implementable framework for calculating interruption schedules that are robust to errors due to measurement and patient variations. In this paper, we discuss the medical motivation for this work, introduce the MPC-based method, show simulation results, and discuss future work necessary to implement the method.

Retrospective analysis of suspending HAART in selected patients with controlled HIV replication

We sought to determine the consequences of stopping highly active antiretroviral therapy (HAART) in a group of 41 HIV-infected individuals with undetectable HIV viral loads and CD4+ counts greater than 500 cells per microliter for 6 months or more. Clinical and laboratory parameters were monitored, as was the time to HAART reinitiation. Three months after HAART interruption, the median CD4+ count declined by 162 cells per microliter and HIV viral load increased by 24,000 copies per milliliter. Over the next year, CD4+ counts continued to decrease by an average of 11 cells per microliter per 3-month intervals. In contrast, HIV viral loads remained stable over the same period. Five of 7 patients (71%) with elevated cholesterol levels and 6 of 13 patients (46%) with elevated triglyceride levels had these values normalize after stopping HAART. After a median of 21 months follow-up, 26 of 41 patients (63%) have restarted HAART. Patients with Centers for Disease Control (CDC) HIV/AIDS C classification were more likely to restart HAART than those with A or B classification (p = 0.008). Reasons for HAART restart included clinical events in 8 patients. Fifteen patients restarted HAART for immunologic reasons: CD4+ count less than 300 cells per microliter (n = 7); HIV viral load greater than 55,000 copies per milliliter (n = 3); or both (n = 5). Three patients restarted HAART because of personal preference. Within 4 months, all 26 patients who restarted HAART achieved HIV viral loads less than 50 copies per milliliter. Although patients were able to rapidly achieve nondetectable HIV viral loads after restarting HAART, the inability to foresee clinical events among 8 patients (20%) is disconcerting. We advise caution before HAART interruption, particularly for those patients with a preceding history of significant HIV-related complications.