The virological and immunological consequences of structured treatment interruptions in chronic HIV-1 infection

Design of an optimal combination therapy with broadly neutralizing antibodies to suppress HIV-1

Infusion of broadly neutralizing antibodies (bNAbs) has shown promise as an alternative to anti-retroviral therapy against HIV. A key challenge is to suppress viral escape, which is more effectively achieved with a combination of bNAbs. Here, we propose a computational approach to predict the efficacy of a bNAb therapy based on the population genetics of HIV escape, which we parametrize using high-throughput HIV sequence data from bNAb-naive patients. By quantifying the mutational target size and the fitness cost of HIV-1 escape from bNAbs, we predict the distribution of rebound times in three clinical trials. We show that a cocktail of three bNAbs is necessary to effectively suppress viral escape, and predict the optimal composition of such bNAb cocktail. Our results offer a rational therapy design for HIV, and show how genetic data can be used to predict treatment outcomes and design new approaches to pathogenic control.

High rate of long-term clinical events after antiretroviral therapy resumption in HIV-positive patients exposed to antiretroviral therapy interruption

OBJECTIVE

We analyzed the incidence rate of long-term events in patients on antiretroviral therapy (ART) previously exposed to therapy interruption.

DESIGN

A single-center cohort study involving participants in ART interruptions (ARTI) clinical trials (n = 10) was conducted.

METHODS

Non-AIDS events after ART resumption were analyzed. A control group not exposed to ARTI was randomly selected from the same cohort and a propensity score of belonging to ARTI group was estimated based on age, sex, CD4+ nadir value, time from HIV diagnosis to ARTI, time from HIV diagnosis to starting ART and time of suppressed viral load, and used to adjust effect estimates.

RESULTS

One hundred and eighty-one patients were included, 136 in ARTI and 45 in the control arm. Median time of known HIV-1 infection was 21 years and median time from ART resumption to first non-AIDS event was 5.2 years. A significantly higher proportion of patients with ARTI had an event as compared with control group [raw percentages: 43% (n = 53) vs. 23% (n = 10), P = 0.015]. These differences were confirmed when only the non-AIDS events occurring after ART resumption were analyzed [adjusted hazard ratio (aHR) = 2.43, 95% confidence interval (CI) 1.15-5.12]. The logistic model adjusted for the propensity score indicated that patients with an ARTI had a four-fold higher risk of having at least one non-AIDS event (P = 0.002).

CONCLUSION

We found a higher risk of having at least one non-AIDS event years after ART resumption in HIV-infected patients exposed to ARTI as compared with controls. These data should be taken into consideration for future functional cure clinical trials.

A Classifier to Predict Viral Control After Antiretroviral Treatment Interruption in Chronic HIV-1-Infected Patients

OBJECTIVES

To construct a classifier that predicts the probability of viral control after analytical treatment interruptions (ATI) in HIV research trials.

METHODS

Participants of a dendritic cell-based therapeutic vaccine trial (DCV2) constituted the derivation cohort. One of the primary endpoints of DCV2 was the drop of viral load (VL) set point after 12 weeks of ATI (delta VL12). We classified cases as "controllers" (delta VL12 > 1 log10 copies/mL, n = 12) or "noncontrollers" (delta VL12 < 0.5 log10 copies/mL, n = 10) and compared 190 variables (clinical data, lymphocyte subsets, inflammatory markers, viral reservoir, ELISPOT, and lymphoproliferative responses) between the 2 groups. Naive Bayes classifiers were built from combinations of significant variables. The best model was subsequently validated on an independent cohort.

RESULTS

Controllers had significantly higher pre-antiretroviral treatment VL [110,250 (IQR 71,968-275,750) vs. 28,600 (IQR 18737-39365) copies/mL, P = 0.003] and significantly lower proportion of some T-lymphocyte subsets than noncontrollers: prevaccination CD4CD45RA+RO+ (1.72% vs. 7.47%, P = 0.036), CD8CD45RA+RO+ (7.92% vs. 15.69%, P = 0.017), CD4+CCR5+ (4.25% vs. 7.40%, P = 0.011), and CD8+CCR5+ (14.53% vs. 27.30%, P = 0.043), and postvaccination CD4+CXCR4+ (12.44% vs. 22.80%, P = 0.021). The classifier based on pre-antiretroviral treatment VL and prevaccine CD8CD45RA+RO+ T cells was the best predictive model (overall accuracy: 91%). In an independent validation cohort of 107 ATI episodes, the model correctly identified nonresponders (negative predictive value = 94%), while it failed to identify responders (positive predictive value = 20%).

CONCLUSIONS

Our simple classifier could correctly classify those patients with low probability of control of VL after ATI. These data could be helpful for HIV research trial design.

Assessing the impact of HIV treatment interruptions using stochastic cellular Automata

Chronic HIV infection causes a progressive decrease in the ability to maintain homeostasis resulting, after some time, in eventual break down of immune functions. Recent clinical research has shed light on a significant contribution of the lymphatic tissues, where HIV causes accumulation of collagen, (fibrosis). Specifically, where tissue is populated by certain types of functional stromal cells designated Fibroblastic Reticular Cells (FRCs), these have been found to play a crucial role in balancing out apoptosis and regeneration of naïve T-cells through 2-way cellular signaling. Tissue fibrosis not only impedes this signaling, effectively reducing T-cell levels through increased apoptosis of cells of both T- and FRC type but has been found to be irreversible by current HIV standard treatment (cART). While the therapy aims to block the viral lifecycle, cART-associated increase of T-cell levels in blood appears to conceal existing FRC impairment through fibrosis. This hidden impairment can lead to adverse consequences if treatment is interrupted, e.g. due to poor adherence (missing doses) or through periods recovering from drug toxicities. Formal clinical studies on treatment interruption have indicated possible adverse effects, but quantification of those effects in relation to interruption protocol and patient predisposition remains unclear. Accordingly, the impact of treatment interruption on lymphatic tissue structure and T-cell levels is explored here by means of computer simulation. A novel Stochastic Cellular Automata model is proposed, which utilizes all sources of clinical detail available to us (though sparse in part) for model parametrization. Sources are explicitly referenced and conflicting evidence from previous studies explored. The main focus is on (i) spatial aspects of collagen build up, together with (ii) collagen increase after repeated treatment interruptions to explore the dynamics of HIV-induced fibrosis and T-cell loss.

Virological Outcome Measures During Analytical Treatment Interruptions in Chronic HIV-1-Infected Patients

Background

Analytical treatment interruptions (ATIs) are essential in research on HIV cure. However, the heterogeneity of virological outcome measures used in different trials hinders the interpretation of the efficacy of different strategies.

Methods

We conducted a retrospective analysis of viral load (VL) evolution in 334 ATI episodes in chronic HIV-1-infected patients collected from 11 prospective studies. Quantitative (baseline VL, set point, delta set point, VL, and delta VL at given weeks after ATI, peak VL, delta peak VL, and area under the rebound curve) and temporal parameters (time to rebound [TtR], set point, peak, and certain absolute and relative VL thresholds) were described. Pairwise correlations between parameters were analyzed, and potential confounding factors (sex, age, time of known HIV infection, time on ART, and immunological interventions) were evaluated.

Results

The set point was lower than baseline VL (median delta set point, –0.26; P < .001). This difference was >1 log10 copies/mL in 13.9% of the cases. The median TtR was 2 weeks; no patients had an undetectable VL at week 12. The median time to set point was 8 weeks: by week 12, 97.4% of the patients had reached the set point. TtR and baseline VL were correlated with most temporal and quantitative parameters. The variables independently associated with TtR were baseline VL and the use of immunological interventions.

Conclusions

TtR could be an optimal surrogate marker of response in HIV cure strategies. Our results underline the importance of taking into account baseline VL and other confounding factors in the design and interpretation of these studies.

Clinical trials of antiretroviral treatment interruption in HIV-infected individuals

: Despite the benefits of antiretroviral therapy (ART) for people living with HIV, there has been a long-standing research interest in interrupting ART as a strategy to minimize adverse effects of ART as well as to test interventions aiming to achieve a degree of virological control without ART. We performed a systematic review of HIV clinical studies involving treatment interruption from 2000 to 2017 to describe the differences between treatment interruption in studies that contained and didn't contain an intervention. We assessed differences in monitoring strategies, threshold to restart ART, duration and adverse outcomes of treatment interruption, and factors aimed at minimizing transmission. We found that treatment interruption has been incorporated into 159 clinical studies since 2000 and is increasingly being included in trials to assess the efficacy of interventions to achieve sustained virological remission off ART. Great heterogeneity was noted in immunological, virological and clinical monitoring strategies, as well as in thresholds to recommence ART. Treatment interruption in recent intervention studies were more closely monitored, had more conservative thresholds to restart ART and had a shorter treatment interruption duration, compared with older treatment interruption studies that didn't include an intervention.

New challenges in therapeutic vaccines against HIV infection

INTRODUCTION

There is a growing interest in developing curative strategies for HIV infection. Therapeutic vaccines are one of the most promising approaches. We will review the current knowledge and the new challenges in this research field. Areas covered: PubMed and ClinicalTrial.gov databases were searched to review the progress and prospects for clinical development of immunotherapies aimed to cure HIV infection. Dendritic cells (DC)-based vaccines have yielded the best results in the field. However, major immune-virologic barriers may hamper current vaccine strategies. We will focus on some new challenges as the antigen presentation by DCs, CTL escape mutations, B cell follicle sanctuary, host immune environment (inflammation, immune activation, tolerance), latent reservoir and the lack of surrogate markers of response. Finally, we will review the rationale for designing new therapeutic vaccine candidates to be used alone or in combination with other strategies to improve their effectiveness. Expert commentary: In the next future, the combination of DCs targeting candidates, inserts to redirect responses to unmutated parts of the virus, adjuvants to redirect responses to sanctuaries or improve the balance between activation/tolerance (IL-15, anti-PD1 antibodies) and latency reversing agents could be necessary to finally achieve the remission of HIV-1 infection.

Polyfunctional HIV-Specific Antibody Responses Are Associated with Spontaneous HIV Control

Elite controllers (ECs) represent a unique model of a functional cure for HIV-1 infection as these individuals develop HIV-specific immunity able to persistently suppress viremia. Because accumulating evidence suggests that HIV controllers generate antibodies with enhanced capacity to drive antibody-dependent cellular cytotoxicity (ADCC) that may contribute to viral containment, we profiled an array of extra-neutralizing antibody effector functions across HIV-infected populations with varying degrees of viral control to define the characteristics of antibodies associated with spontaneous control. While neither the overall magnitude of antibody titer nor individual effector functions were increased in ECs, a more functionally coordinated innate immune-recruiting response was observed. Specifically, ECs demonstrated polyfunctional humoral immune responses able to coordinately recruit ADCC, other NK functions, monocyte and neutrophil phagocytosis, and complement. This functionally coordinated response was associated with qualitatively superior IgG3/IgG1 responses, whereas HIV-specific IgG2/IgG4 responses, prevalent among viremic subjects, were associated with poorer overall antibody activity. Rather than linking viral control to any single activity, this study highlights the critical nature of functionally coordinated antibodies in HIV control and associates this polyfunctionality with preferential induction of potent antibody subclasses, supporting coordinated antibody activity as a goal in strategies directed at an HIV-1 functional cure.

Molecular and cellular insights into T cell exhaustion

In chronic infections and cancer, T cells are exposed to persistent antigen and/or inflammatory signals. This scenario is often associated with the deterioration of T cell function: a state called 'exhaustion'. Exhausted T cells lose robust effector functions, express multiple inhibitory receptors and are defined by an altered transcriptional programme. T cell exhaustion is often associated with inefficient control of persisting infections and tumours, but revitalization of exhausted T cells can reinvigorate immunity. Here, we review recent advances that provide a clearer molecular understanding of T cell exhaustion and reveal new therapeutic targets for persisting infections and cancer.

Molecular and cellular insights into T cell exhaustion

In chronic infections and cancer, T cells are exposed to persistent antigen and/or inflammatory signals. This scenario is often associated with the deterioration of T cell function: a state called 'exhaustion'. Exhausted T cells lose robust effector functions, express multiple inhibitory receptors and are defined by an altered transcriptional programme. T cell exhaustion is often associated with inefficient control of persisting infections and tumours, but revitalization of exhausted T cells can reinvigorate immunity. Here, we review recent advances that provide a clearer molecular understanding of T cell exhaustion and reveal new therapeutic targets for persisting infections and cancer.

Human Immunodeficiency Virus-Type 1 Specific Cellular Immunity in Chronic Infected Patients on Prolonged Highly Active Antiretroviral Treatment and on Structured Treatment Interruption

We have followed 15 HIV-1 chronically infected patients during prolonged highly active antiretroviral treatment (HAART) and subsequent long term structured treatment interruption (STI). We analyzed Nef, Tat, and p24 specific cellular immunity using IFN-gamma enzyme-linked immunospot assays and T cell proliferation assays. Eight HAART patients showed IFN-gamma responses to at least one antigen, but no positive responses were seen during STI. We observed retained or increased p24 specific IFN-gamma responses in most patients during HAART with viral suppression. These results showed persisting HIV-1 specific cellular immunity during HAART; however, in prolonged STI with viral rebound this immunity declined.

No clinically significant drug-resistance mutations in HIV-1 subtype C-infected women after discontinuation of NRTI-based or PI-based HAART for PMTCT in Botswana

Risk of developing drug resistance after stopping antiretroviral regimens to prevent mother-to-child HIV-1 transmission is unknown. The Mma Bana Study randomized treatment-naive pregnant women with CD4 ≥200 cells per cubic millimeter to receive either abacavir/zidovudine/lamivudine [triple nucleoside reverse transcriptase inhibitor (NRTI) arm] or lopinavir/ritonavir/zidovudine/lamivudine [protease inhibitor (PI) arm]. Drugs were discontinued after 6 months of breastfeeding. One month after discontinuation, 29 NRTI arm samples and 25 PI arm samples were successfully genotyped. No clinically significant antiretroviral resistance mutations were detected. Eight minor resistance mutations were found among 11 (20%) women (3 from NRTI arm and 8 from PI arm), occurring at similar frequencies to those reported in HIV-1 subtype C treatment-naive cohorts.

Taking a break from chemotherapy to fight drug-resistance: The cases of cancer and HIV/AIDS

In this work, we present how optimized treatment interruptions during chemotherapy may be used to control drug-resistance, a major challenge for clinicians worldwide. Specifically, we examine resistance in cancer and HIV/AIDS. For each disease, we use mathematical models alongside real data to represent the respective complex biological phenomena and optimal control algorithms to design optimized treatment schedules aiming at controlling disease progression and patient death. In both diseases, it is shown that the key to controlling resistance is the optimal management of the frequency and magnitude of treatment interruptions as a way to facilitate the interplay between the competitive resistant/sensitive strains.

Association of early HIV viremia with mortality after HIV-associated lymphoma

OBJECTIVE

To examine the association between early HIV viremia and mortality after HIV-associated lymphoma.

DESIGN

Multicenter observational cohort study.

SETTING

Center for AIDS Research Network of Integrated Clinical Systems cohort.

PARTICIPANTS

HIV-infected patients with lymphoma diagnosed between 1996 and 2011, who were alive 6 months after lymphoma diagnosis and with at least two HIV RNA values during the 6 months after lymphoma diagnosis.

EXPOSURE

Cumulative HIV viremia during the 6 months after lymphoma diagnosis, expressed as viremia copy-6-months.

MAIN OUTCOME MEASURE

All-cause mortality between 6 months and 5 years after lymphoma diagnosis.

RESULTS

Of 224 included patients, 183 (82%) had non-Hodgkin lymphoma (NHL) and 41 (18%) had Hodgkin lymphoma. At lymphoma diagnosis, 105 (47%) patients were on antiretroviral therapy (ART), median CD4⁺ cell count was 148 cells/μl (interquartile range 54-322), and 33% had suppressed HIV RNA (<400 copies/ml). In adjusted analyses, mortality was associated with older age [adjusted hazard ratio (AHR) 1.37 per decade increase, 95% CI 1.03-1.83], lymphoma occurrence on ART (AHR 1.63, 95% CI 1.02-2.63), lower CD4⁺ cell count (AHR 0.75 per 100 cells/μl increase, 95% CI 0.64-0.89), and higher early cumulative viremia (AHR 1.35 per log₁₀ copies × 6-months/ml, 95% CI 1.11-1.65). The detrimental effect of early cumulative viremia was consistent across patient groups defined by ART status, CD4⁺ cell count, and histology.

CONCLUSION

Exposure to each additional 1-unit log₁₀ in HIV RNA throughout the 6 months after lymphoma diagnosis was associated with a 35% increase in subsequent mortality. These results suggest that early and effective ART during chemotherapy may improve survival.

Influence of episodes of intermittent viremia ("blips") on immune responses and viral load rebound in successfully treated HIV-infected patients

Presenting episodes of intermittent viremia (EIV) under combination antiretroviral therapy (cART) is frequent, but there exists some controversy about their consequences. They have been described as inducing changes in immune responses potentially associated with a better control of HIV infection. Conversely, it has been suggested that EIV increases the risk of virological failure. A retrospective analysis of a prospective, randomized double-blinded placebo-controlled study was performed. Twenty-six successfully treated HIV-infected adults were randomized to receive an immunization schedule or placebo, and after 1 year of follow-up cART was discontinued. The influence of EIV on T cell subsets, HIV-1-specific T cell immune responses, and viral load rebound, and the risk of developing genotypic mutations were evaluated, taking into account the immunization received. Patients with EIV above 200 copies/ml under cART had a lower proportion of CD4(+) and CD4(+)CD45RA(+)RO(-) T cells, a higher proportion of CD8(+) and CD4(+)CD38(+)HLADR(+) T cells, and higher HIV-specific CD8(+) T cell responses compared to persistently undetectable patients. After cART interruption, patients with EIV presented a significantly higher viral rebound (p=0.007), associated with greater increases in HIV-specific lymphoproliferative responses and T cell populations with activation markers. When patients with EIV between 20 and 200 copies/ml were included, most of the differences disappeared. Patients who present EIV above 200 copies/ml showed a lower CD4(+) T cell count and higher activation markers under cART. After treatment interruption, they showed greater specific immune responses against HIV, which did not prevent a higher virological rebound. EIV between 20 and 200 copies/ml did not have this deleterious effect.

In vitro effects of the CCR5 inhibitor maraviroc on human T cell function

BACKGROUND

Several potential immunological benefits have been observed during treatment with the CC chemokine receptor 5 (CCR5) antagonist maraviroc, in addition to its antiviral effect. Our objective was to analyse the in vitro effects of CCR5 blockade on T lymphocyte function and homeostasis.

METHODS

Peripheral blood mononuclear cells (PBMCs) from both HIV-negative (n=28) and treated HIV-positive (n=27) individuals were exposed in vitro to different concentrations of maraviroc (0.1-100 μM). Effects on T cell activation were analysed by measuring the expression of the CD69, CD38, HLA-DR and CD25 receptors as well as CCR5 density using flow cytometry. Spontaneous and chemokine-induced chemotaxis were measured by transwell migration assays, and polyclonal-induced proliferation was assessed by a lymphoproliferation assay and carboxyfluorescein succinimidyl ester staining.

RESULTS

Maraviroc increases CCR5 surface expression on activated T cells, even at low doses (0.1 μM). Slight differences were detected in the frequency and mean fluorescence intensity of activation markers at high concentrations of maraviroc. Expression of CD25, CD38 and HLA-DR tended to decrease in both CD4+ and CD8+ T lymphocytes, whereas expression of CD69 tended to increase. Maraviroc clearly inhibits T cell migration induced by chemokines in a dose-dependent manner. Moreover, at 100 μM, maraviroc tends to inhibit T cell proliferation.

CONCLUSIONS

These data showed that in vitro exposure to maraviroc decreases some activation expression markers on T lymphocytes and also migration towards chemoattractants. These results support the additional immunological effects of CCR5 blockade and suggest that maraviroc might have potential capacity to inhibit HIV-associated chronic inflammation and activation, both by directly affecting T cell activation and by reducing entrapment of lymphocytes in lymph nodes.

HIV-1 Tat B-cell epitope vaccination was ineffectual in preventing viral rebound after ART cessation: HIV rebound with current ART appears to be due to infection with new endogenous founder virus and not to resurgence of pre-existing Tat-dependent viremia

CD4 T cell activation, essential for productive HIV infection, is provided initially in acute HIV infection by innate immune system secretion of activating cytokines. This cytokine response wanes with time and long-term activation of CD4 cells is maintained by HIV Tat protein secreted by HIV infected cells. Structured treatment interruption (STI) in well-controlled antiretroviral-treated (ART) subjects was explored a decade ago with a consensus finding that, in most subjects, HIV levels rebounded within four weeks to pre-ART levels. Based on these observations we initiated a randomized placebo-controlled study of a universal anti-Tat epitope vaccine, TUTI-16, to determine if immunological blockade of Tat would prevent HIV rebound after ART cessation. TUTI-16 immunization was safe, with predominantly mild local and systemic injection-related adverse reactions. TUTI-16 was also immunogenic, with high levels of anti-Tat antibodies compared with levels previously shown to reduce HIV replication in vivo. Of 21 subjects analyzed, 13 (62%) had HIV rebounds vs. 8 (38%) that remained aviremia, but this distribution was not vaccine-related (p = 0.61 log-rank (Mantel-Cox) test), nullifying our hypothesis that anti-Tat antibodies would block rebound of Tat-dependent set-point HIV viremia after ART cessation. Our present findings are consistent with recent molecular findings that rebounding virus following STI is homogeneous and unrelated to previous circulating HIV, suggesting that rebounding HIV represents new founder virus, akin to the original acute HIV infection. We propose, therefore, that STI may have potential as a practical and economical approach to testing the safety and efficacy of candidate prophylactic HIV vaccines.

Standing genetic variation and the evolution of drug resistance in HIV

Drug resistance remains a major problem for the treatment of HIV. Resistance can occur due to mutations that were present before treatment starts or due to mutations that occur during treatment. The relative importance of these two sources is unknown. Resistance can also be transmitted between patients, but this process is not considered in the current study. We study three different situations in which HIV drug resistance may evolve: starting triple-drug therapy, treatment with a single dose of nevirapine and interruption of treatment. For each of these three cases good data are available from literature, which allows us to estimate the probability that resistance evolves from standing genetic variation. Depending on the treatment we find probabilities of the evolution of drug resistance due to standing genetic variation between and . For patients who start triple-drug combination therapy, we find that drug resistance evolves from standing genetic variation in approximately 6% of the patients. We use a population-dynamic and population-genetic model to understand the observations and to estimate important evolutionary parameters under the assumption that treatment failure is caused by the fixation of a single drug resistance mutation. We find that both the effective population size of the virus before treatment, and the fitness of the resistant mutant during treatment, are key-parameters which determine the probability that resistance evolves from standing genetic variation. Importantly, clinical data indicate that both of these parameters can be manipulated by the kind of treatment that is used.

For HIV patients who are treated with antiretroviral drugs, treatment usually works well. However, the virus can, and sometimes does, become resistant against one or more drugs. HIV drug resistance results from the acquisition of specific and well known mutations. It is currently unknown whether drug resistance mutations usually stem from standing genetic variation, i.e., they were already present at low frequency before treatment started, or whether they tend to occur during treatment. In the current manuscript, I make use of several large datasets and evolutionary modeling to estimate the probability that drug resistance mutations are present before treatment starts and lead to viral failure. I find that for the most common type of treatment with a combination of three drugs, drug resistance evolves from pre-existing mutations in 6% of the patients. With other types of treatment, this probability varies from 0 to 39%. I conclude that there is room for improvement in preventing the evolution of drug resistance from pre-existing mutations.

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.

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.

CD8 T-Cell Responses before and after Structured Treatment Interruption in Ugandan Adults Who Initiated ART with CD4 T Cells <200 Cell/μL: The DART Trial STI Substudy

Objective. To better understand attributes of ART-associated HIV-induced T-cell responses that might be therapeutically harnessed. Methods. CD8(+) T-cell responses were evaluated in some HIV-1 chronically infected participants of the fixed duration STI substudy of the DART trial. Magnitudes, breadths, and functionality of IFN-γ and Perforin responses were compared in STI (n = 42) and continuous treatment (CT) (n = 46) before and after a single STI cycle when the DART STI trial was stopped early due to inferior clinical outcome in STI participants. Results. STI and CT had comparable magnitudes and breadths of monofunctional CD8(+)IFNγ(+) and CD8(+)Perforin(+) responses. However, STI was associated with significant decline in breadth of bi-functional (CD8(+)IFNγ(+)Perforin(+)) responses; P = .02, Mann-Whitney test. Conclusions. STI in individuals initiated onto ART at <200 CD4(+) T-cell counts/μl significantly reduced occurrence of bifunctional CD8(+)IFNγ(+)/Perforin(+) responses. These data add to others that found no evidence to support STI as a strategy to improve HIV-specific immunity during ART.

Interruptions of antiretroviral therapy in human immunodeficiency virus infection: are they detrimental to neurocognitive functioning?

Because interruptions of antiretroviral treatment may entail clinical risks for human immunodeficiency virus (HIV)-infected individuals, we investigated their impact on neurocognitive functioning. Cross-sectional study was carried out, comparing HIV-infected persons who had interrupted antiretroviral therapy in the past (interruption group, IG) with persons who had never discontinued therapy (noninterruption group, NIG). Interruption was defined as the discontinuation of highly active antiretroviral therapy (HAART) for more than 15 days after previous treatment of at least 15 days. All the participants were on therapy. Demographic, clinical, and neurocognitive variables were assessed. The primary end point was the percentage of people with neurocognitive impairment. The score in different neurocognitive domains was a secondary end point. A total of 83 subjects participated in the study (IG: n = 27; NIG: n = 56). Demographic and clinical characteristics were balanced between the groups, except for years since HIV diagnosis (IG, 13.8; NIG, 10.2 [P = .003]). The percentage of people with neurocognitive impairment was significantly higher in the IG group (IG, 59.25%; NIG, 33.92% [P = 0.02]). As for scores in neurocognitive domains, individuals in the IG showed worse neurocognitive functioning, and significant differences in attention/working memory and information processing speed were found. The adjusted analysis supported the unadjusted analysis. In this study, a higher prevalence of neurocognitive impairment was detected in HIV-infected persons who had interrupted antiretroviral therapy in the past. Additionally, neurocognitive functioning was observed to be more impaired in the same individuals. Further studies should examine the potential negative effects of antiretroviral therapy interruptions on neurocognitive functioning.

[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.

Influence of a vaccination schedule on viral load rebound and immune responses in successfully treated HIV-infected patients

Vaccination is recommended for HIV-infected patients. Transient increases of viral load (VL) and risk of developing resistance to HAART have been described. In addition, VL rebounds could increase HIV-specific immune responses. Twenty-six successfully treated HIV-infected adults were randomized to receive a vaccination schedule or placebo during 12 months. Afterward, HAART was discontinued. Influences of vaccination over VL, genotypic mutations, different T cell subsets, and HIV-1-specific immune responses were evaluated. Patients did not present any secondary effect. No differences in incidence of detectable VL determinations were detected between groups [relative risk 0.54 (95% CI 0.23-1.26)]. No relevant resistance mutations were detected. The vaccinated group showed a significant drop in CD4(+) T cells (p = 0.046) associated with increases in activated T cells. HIV-1-specific lymphoproliferative responses increased more in the vaccinated group during the vaccination period. Viral rebound dynamics after interrupting HAART were similar in both groups. A vaccination schedule in successfully treated HIV patients was safe, was not associated with an increase in detectable VL, and did not increase the risk of developing resistance mutations. However, it induced an increase in T cell activation and a drop in CD4(+) T cells, although these changes did not influence the VL rebound dynamics after HAART interruption.

HIV dynamics and integrase inhibitors

The integrase inhibitor (INI) raltegravir has shown promising results in clinical trials to date, reducing second phase HIV RNA levels by 70% in comparison with standard regimens. These trial results have been limited by the 50 copies/ml detection limit of the HIV RNA assay and have not investigated the effect of an INI regimen on levels of latently infected cells. Mathematical models that duplicated previous raltegravir results were extended to estimate effects of an INI regimen on HIV RNA beyond second phase and on HIV DNA levels. Depending on assumptions underlying later phase HIV RNA generation and its interaction with latently infected cells, HIV RNA in later phases can be lower or show no difference with an INI, and similarly for HIV DNA. If latent infection is maintained by differentiation of stem cells with integrated HIV DNA, then an INI regimen will eventually have no added benefit. Other hypotheses that allow ongoing replication predict continually lower HIV RNA levels with an INI regimen, but this differential effect need not translate to a reduction in latent infection. Investigation of HIV RNA and HIV DNA levels with an INI will provide better understanding of how these components are generated and maintained under antiretroviral therapy.

Rates and determinants of virologic and immunological response to HAART resumption after treatment interruption in HIV-1 clinical practice

OBJECTIVE

To describe CD4 and HIV RNA changes during treatment resumption (TR) after treatment interruption (TI) compared with response to first highly active antiretroviral therapy (HAART) and to investigate predictors.

METHODS

Using Concerted Action on SeroConversion to AIDS and Death in Europe (CASCADE) data, we identified subjects who interrupted first HAART, not initiated during primary infection. We estimated rate of CD4 change during TR and time from TR to HIV RNA<500 copies per milliliter and subsequent rebound and factors associated with these outcomes.

RESULTS

Of 281 persons treated for median 18.4 months before interrupting, 259 resumed HAART. CD4 increases in the first 3 months on HAART were similar pre-TI and post-TI but after 3 months were significantly higher during pre-TI HAART, with median +106 and +172 cells per microliter at 3 and 18 months, respectively, during initial HAART compared with +99 and +142 cells per microliter during post-TI HAART, respectively. Subjects with lower CD4 counts at TI, aged older than 40 years, and those resuming the same HAART as their pre-TI regimen had lower CD4 increases during the first 3 months of TR. The majority (86%) of individuals reinitiating therapy achieved HIV RNA<500 copies per milliliter.

CONCLUSIONS

Immune reconstitution after TI is generally poorer than after first HAART, particularly for patients aged older than 40 years at TI and those with poorer immunological responses to pre-TI HAART. Reinitiation of the same HAART regimen as pre-TI also seems to have unfavorable outcomes.

Short Communication: Natural killer cells and expression of KIR receptors in chronic HIV type 1-infected patients after different strategies of structured therapy interruption

Few data evaluating the NK cell profile during structured therapy interruption (STI) in chronic HIV-1 infection are available. Changes in NK cell percentages and KIR and NKG2A receptors were analyzed at baseline and after 2 years of follow-up in 121 patients on ART with CD4(+) >450 cells/ml and VL <200 copies/ml randomized in three arms according to the criteria employed to resume ART during STI: virological arm (VA n = 47, VL >30,000 copies/ml or CD4 <350 cells/ml), immunological arm (IA n = 37, CD4< 350 cells/ml), and a control arm (n = 37) in which ART was maintained. After 2 years of follow-up, a decrease in CD3(-)CD56(+) CD16(+) cell percentages in VA and IA patients, but not in CA patients, was observed. Those patients with higher decrease in CD3(-)CD56(+)CD16(+) cells had a higher decrease in CD4(+) cells (r = 0.35, p = 0.001) and higher increase in PVL (r = -0.26, p = 0.02). KIR and NKG2A receptor expression tended to increase in CA and decreased in the other two arms (more in IA than in VA). Patients who displayed a greater decrease in CD4(+) T cells and a greater rise in PVL after 2 years of follow-up had a significantly higher decrease in KIR and NKG2A receptors expressed in CD3(-)CD56(+) cells. Patients who presented the lowest levels of total NK cells and KIR and NKG2A receptor expression after STI showed the poorest virology or immunology outcomes. This finding suggests that STI could decrease the number of NK subsets, which is related to the worst clinical development in these patients.

Cellular reservoirs of HIV-1 and their role in viral persistence

A major obstacle in human immunodeficiency virus type 1 (HIV-1) eradication is the ability of the virus to remain latent in a subpopulation of the cells it infects. Latently infected cells can escape the viral immune response and persist for long periods of time, despite the presence of successful highly active antiretroviral therapy (HAART). Given the appropriate stimulus, latently infected cells can reactivate and start producing infectious virions. The susceptibility of these cell populations to HIV-1, their life span, their proliferative capacity, and their ability to periodically produce infectious virus subsequent to alterations in cellular physiology and/or immunologic controls are critical issues which determine the contribution of these cells to viral persistence. Memory CD4+ T cells due to the long life span, which may be several years, and their ability to reactivate upon encounter with their cognate antigen or other stimulation, are considered a critical reservoir for maintenance of latent HIV-1 proviral DNA. Cells of the monocyte-macrophage lineage, which originate in the bone marrow (BM), are of particular importance in HIV-1 persistence due to their ability to cross the blood-brain barrier (BBB) and spread HIV-1 infection in the immunoprivileged central nervous system (CNS). Hematopoietic progenitor cells (HPCs) are also a potential HIV-1 reservoir, as several studies have shown that CD34+ HPCs carrying proviral DNA can be found in vivo in a subpopulation of HIV-1-infected patients. The ability of HPCs to proliferate and potentially generate clonal populations of infected cells of the monocyte-macrophage lineage may be crucial in HIV-1 dissemination. The contribution of these and other cell populations in HIV-1 persistence, as well as the possible strategies to eliminate latently infected cells are critically examined in this review.

NK-associated regulatory receptors in a structured HAART interruption of HIV-1-positive individuals

Since highly active antiretroviral therapy (HAART) was introduced a decade ago, it has been shown to be effective in keeping HIV-1 replication under control. Nevertheless, it is also known that HAART has certain limitations, such as its inability to completely inhibit the viral replication that maintains virus reservoirs, its high toxicity when the treatment is maintained for long periods of time, and the appearance of viral resistance to the therapy. These limitations have led to the introduction of structured treatment interruption (STI) of antiretroviral therapy, the principle of which is to reduce the clinical complications of HAART, and hypothetically to boost the cellular immune response of the patient host. The aim of this study was to analyze for the first time the impact of STI on the innate immune system. Specifically, we analyzed NK cells and their regulatory receptors (KIRs, NKG2, NCRs, and ILTs) and the cytokines that might control the NK response. Six months after the initiation of STI, the results revealed in most patients a significant increase in NK cells expressing ILT2 and NKp46 receptors. Slight or no changes were observed in other parameters studied, either during interruption or when HAART was reintroduced. Our data show that the STI strategy, irrespective of whether it improved the patients' clinical evolution, induced functional phenotype changes in NK cell subsets.

HLA class I-restricted T-cell responses may contribute to the control of human immunodeficiency virus infection, but such responses are not always necessary for long-term virus control

A rare subset of human immunodeficiency virus (HIV)-infected individuals maintains undetectable HIV RNA levels without therapy ("elite controllers"). To clarify the role of T-cell responses in mediating virus control, we compared HLA class I polymorphisms and HIV-specific T-cell responses among a large cohort of elite controllers (HIV-RNA < 75 copies/ml), "viremic" controllers (low-level viremia without therapy), "noncontrollers" (high-level viremia), and "antiretroviral therapy suppressed" individuals (undetectable HIV-RNA levels on antiretroviral therapy). The proportion of CD4(+) and CD8(+) T cells that produce gamma interferon (IFN-gamma) and interleukin-2 (IL-2) in response to Gag and Pol peptides was highest in the elite and viremic controllers (P < 0.0001). Forty percent of the elite controllers were HLA-B*57 compared to twenty-three percent of viremic controllers and nine percent of noncontrollers (P < 0.001). Other HLA class I alleles more common in elite controllers included HLA-B*13, HLA-B*58, and HLA-B*81 (P < 0.05 for each). Within elite and viremic controller groups, those with protective class I alleles had higher frequencies of Gag-specific CD8(+) T cells than those without these alleles (P = 0.01). Noncontrollers, with or without protective alleles, had low-level CD8(+) responses. Thus, certain HLA class I alleles are enriched in HIV controllers and are associated with strong Gag-specific CD8(+)IFN-gamma(+)IL-2(+) T cells. However, the absence of evidence of T cell-mediated control in many controllers suggests the presence of alternative mechanisms for viral control in these individuals. Defining mechanisms for virus control in "non-T-cell controllers" might lead to insights into preventing HIV transmission or preventing virus replication.

Clinical outcomes after an unstructured treatment interruption in children and adolescents with perinatally acquired HIV infection

OBJECTIVE

An unstructured treatment interruption in children with perinatally acquired HIV infection is an issue with unresolved significance. The objective of this study was to investigate the actual prevalence and clinical outcomes of a treatment interruption in children and adolescents with perinatally acquired HIV-1 infection.

METHODS

Clinical data were analyzed for 72 children and adolescents who had HIV-1 infection and stopped their medications at 4 academic centers in the United States between January 2000 and September 2004.

RESULTS

Among 405 patients with perinatal HIV-1 infection, 72 (17.8%) experienced a treatment interruption during the observation period. The mean age of patients at the time of the treatment interruption was 12.8 years, and the mean length of the treatment interruption was 14 months. Medication fatigue was the most common reason for a treatment interruption. The CD4+ T-cell percentage nadir before the treatment interruption did not predict CD4+ T-cell percentage declines during the treatment interruption; however, the CD4+ T-cell percentage gain from nadir to the time of the treatment interruption predicted CD4+ T-cell percentage declines during the treatment interruption. During the median follow-up of 19 months (range: 6-48 months), 48 (67%) patients resumed antiretroviral medications. As expected, there was a continuous CD4+ T-cell percentage decrease and plasma HIV-1 RNA increase during the observation period. Overall, 7 (10%) patients were admitted to the hospital; 2 (3%) patients experienced an AIDS-defining illness.

CONCLUSIONS

An unstructured treatment interruption seems to be a major issue for youth with perinatally acquired HIV-1 infection. Patients who experienced the greatest rise in CD4+ T-cell percentage on treatment had the largest CD4+ T-cell percentage decline after the treatment interruption. Close monitoring is required when a treatment interruption occurs in children and adolescents with HIV infection.

Planned multiple exposures to autologous virus in HIV type 1-infected pediatric populations increases HIV-specific immunity and reduces HIV viremia

We tested to determine if planned multiple exposures to autologous HIV in pediatric patients with HIV-1 infection will induce cellular immunity that controls viremia. A prospective multicenter study of aviremic pediatric patients on highly active antiretroviral therapy who underwent progressively longer antiretroviral treatment interruptions in cycles starting with 3 days, increasing by 2 days in length each consecutive cycle, was conducted. Eight individuals became viremic and reached Cycle 13 or greater with an "off-therapy" interval of >or=27 days. HIV-specific interferon-gamma (IFN-gamma) production to inactivated HIV and vaccinia vectors expressing gag, env, nef, and pol increased (>10-fold) from baseline in six of eight subjects. The HIV-specific lymphoproliferative response as measured by the median stimulation index (SI) increased in the treatment group from 1 at baseline to 16, 12, 4, and 3 at Cycles 7, 10, 13, and 17, respectively. Median plasma RNA levels peaked at Cycle 7 (4.45 log) and declined to levels <10(4) cp/ml after Cycle 10 (4.1, 3.5, and 3.4 at Cycles 10, 13, and 17). In a subset of five patients who reached Cycle 17, HIV-specific IFN-gamma frequencies were 4- to 30-fold higher and median RNA levels were 0.32-2.10 (median 1.3) log lower than at comparable days off treatment at Cycle 8 (17 days off therapy). A second group of children, not undergoing drug interruption, did not develop significant increases in either HIV-specific IFN-gamma production or SI. Increased HIV-specific immune responses and decreased HIV RNA were seen in those children who have had >10 cycles of antiretroviral discontinuations of increasing durations acting as autologous virus vaccinations. Other studies may have failed due to an insufficient number of exposures to HIV; most of the studies had fewer than six drug interruptions.

Full-length characterization of A1/D intersubtype recombinant genomes from a therapy-induced HIV type 1 controller during acute infection and his noncontrolling partner

To increase the understanding of mechanisms of HIV control we have genetically and immunologically characterized a full-length HIV-1 isolated from an acute infection in a rare case of undetectable viremia. The subject, a 43-year-old Danish white male (DK1), was diagnosed with acute HIV-1 infection after 1 year in Uganda. Following transient antiretroviral therapy DK1 maintained undetectable viral load for more than 10 years. His Ugandan wife (UG1) developed high viral load. HIV-1 sequences from both individuals were compared by bootscanning for recombination break points. Diversity plots and phylogenic trees were constructed and diversity and evolutionary distances were calculated. Intracellular IFN-gamma in CD8(+)CD3(+) T-lymphocyte reactions was investigated by intracellular flow cytometry (IC-FACS). Virus isolates from both patients were A1D intersubtype recombinants showing 98% sequence homology in shared regions. Four of seven crossover points were identical; however, the env gene from UG1 was subtype D, but A1 in DK1. Both viruses encoded proteins of the expected length and replicated equally well in vitro. DK1 and UG1 shared the HLA-A02 tissue type. HLA-A02-restricted CD8(+) T cell IFN-gamma IC-FACS response in DK1 was detected against only one (Pol(476)) of 23 conserved epitopes. Neutralizing antibodies were induced only to the homologous isolate. These results indicate an A1D intersubtype recombination or transmission of a minor variant. Transient early antiretroviral therapy may have induced full HIV-1 control in this individual mediated by a narrow specific cytotoxic T lymphocyte and neutralizing antibody response and/or other factors yet to be characterized.

A Prospective Randomized Controlled Trial of Structured Treatment Interruption in HIV-Infected Patients Failing Highly Active Antiretroviral Therapy (Canadian HIV Trials Network Study 164)

OBJECTIVE

To determine prospectively the impact of switching treatment-experienced patients with virologic failure to a salvage regimen with or without a 12-week structured treatment interruption (STI). The primary endpoint was the percentage of patients with a 3-month sustained HIV RNA level <50 copies/mL.

METHODS

A randomized, open-label, multicenter trial. At least 2 new antiretroviral (ARV) drugs, based on patient history, were included in the salvage regimen, as determined before randomization and guided by resistance testing.

RESULTS

A total of 147 patients were randomized: 79 to the immediate switch (IS) arm and 68 to the STI arm. Success was achieved by 64% in the IS arm and 51% in the STI arm (95% confidence interval for the difference from 5% in favor of STI to 30% in favor of IS). During the STI, the median decrease in CD4 count was 80 cells/mm and the increase in viral load was 0.8 log10 copies/mL. There were no differences in median CD4 cell counts or HIV RNA levels at week 60. Two unrelated deaths (1 in each arm) and 3 AIDS-defining events (in the STI arm) occurred.

CONCLUSION

A 12-week STI before the initiation of salvage ARV therapy did not increase the proportion of patients with 3 months of sustained suppression of HIV RNA to <50 copies/mL.

Virological characterization of patients treated early is able to control HIV-1 replication after multiple cycles of structured therapy interruption

This study aimed to define clinical and virological parameters associated with spontaneous control of HIV replication in patients having initiated HAART during primary HIV infection, who underwent structured therapy interruption by two protocols with either fixed or HIV viremia-guided scheme. At the end of the protocol all patients were changed to viremia-guided scheme and observed for 12 months (follow-up). Patients maintaining HIV viremia below the indications for resumption of HAART during the follow-up, were defined controllers, those who had to resume HAART were defined non-controllers. The following parameters were examined: pre-interruption therapy duration, CD4(+), HIV RNA, proviral DNA, evolution of viral quasispecies. No specific advantage was conferred by either interruption of structured therapy in the proportion of controllers and non-controllers. Pre-HAART and zenith CD4(+), pre-therapy interruption, HAART duration, but not pre-HAART HIV RNA, were significantly higher in controllers as compared to non-controllers. HIV RNA levels after the first interruption cycle of therapy were significantly lower in controllers than in non-controllers. Proviral DNA levels were also lower in controllers at this time point. HIV RNA and proviral DNA levels associated with the last interruption of therapy cycle were not different from those associated with the first cycle, and, in spite of multiple waves of virus rebound, very few gag quasispecies variants emerged in each patient. The data suggest that pre-treatment clinical parameters and virological events associated with the first viral rebound are crucial factors in determining the ability to control viral replication after multiple cycles of interruption of treatment.

Acutely dysregulated, chronically disabled by the enemy within: T-cell responses to HIV-1 infection

Human immunodeficiency virus (HIV) infection causes chronic progressive immunodeficiency and immune dysregulaton. Although simple depletion of the major target of HIV infection, the CD4+ T cell, can explain much of the immunosuppression seen, there are multiple other factors contributing to the immune dysregulation. CD4+ T-cell depletion induces a range of homeostatic mechanisms that contribute to immune activation and cell turnover, providing a milieu conducive to further viral replication and cell destruction, resulting in functional defects in various lymphoid organs. These changes are progressive and in turn compromise the homeostatic processes. Further, the infection, like any other viral infection, provokes an active immune response consisting of both CD4+ and CD8+ T-cell responses. Both appear compromised, displaying aberrant memory cell production. While some of these defects result from viral variation and the chronicity of antigen presentation, other defects of memory cell production appear very early during the primary immune response limiting the viral specific T-cell responses from the outset. This, combined with the ability of the virus to escape any successful immune responses, results in an attenuated immune response that eventually becomes exhausted, characterized by progressive deficits in T-cell repertoire. Furthermore, negative regulatory mechanisms that normally control the immune response may be aberrantly invoked, perhaps directly by the virus, further compromising the efficacy of the immune response. Rational design of effective immunotherapies depends on a clear understanding of the processes compromising the immune response to HIV.

Highly active antiretroviral therapy interruption: predictors and virological and immunologic consequences

OBJECTIVE

To characterize the magnitude and the predictors of highly active antiretroviral therapy (HAART) interruption (TI) and to investigate its immunologic and virological consequences.

METHODS

Using Concerted Action on Seroconversion to AIDS and Death in Europe data from 8,300 persons with well-documented seroconversion dates, we identified subjects with stable first HAART (for at least 90 days) not initiated during primary infection. A TI was defined as an interruption of all antiretroviral therapy drugs for at least 14 days.

RESULTS

Of 1,551 subjects starting HAART, 299 (19.3%) interrupted treatment. Median (interquartile range) duration of the TI was 189 (101-382) days. The cumulative probability (95% confidence interval) of TI at 2 years was 15.9% (14.0%-18.1%). Women were more likely to have a TI than men in the same exposure group (35.8% vs 24.2% among drug users, 22.1% vs 13.3% among heterosexuals; P < 0.05). Higher baseline viremia and poor immunologic response to HAART were associated with higher probabilities of TI. Median (interquartile range) individual CD4 cell loss during TI was 94 (1-220) cells/microL. Older age at HAART (>40 yr), lower pre-HAART nadir (<200 cells/microL), and lower CD4 at start of TI (<350 cells/microL) were significantly associated with greater relative CD4 loss during TI.

CONCLUSIONS

We estimate that almost 1 in 6 subjects on HAART interrupts treatment by 2 years. Further research is needed to investigate the reasons why TI is higher in women. We have identified characteristics of subjects with the greatest risk for CD4 loss in whom TI may have greater risks.

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.

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

BACKGROUND

Structured treatment interruptions (STI) of antiretroviral therapy (ART) have been investigated as part of novel treatment strategies, with different aims and objectives depending on the populations involved. These populations include: 1) patients who initiate ART during acute HIV infection; 2) patients with chronic HIV infection, on ART, with successfully suppressed viremia; and 3) patients with chronic HIV infection and treatment failure, with persistent viremia due to multi-drug resistant HIV (Hirschel 2001; Deeks 2002; Miller 2003). In an earlier Cochrane review (Pai 2005), we had summarized the evidence about the effects of STI in chronic suppressed HIV infection. In this review, we summarize the evidence on STI in patients with chronic unsuppressed HIV infection due to drug-resistant HIV. Unsuppressed HIV infection describes those patients who cannot suppress viremia, due to the presence of multi-drug-resistant virus. It is also referred to as treatment failure. Drug resistance is identified by the presence of resistant mutations at baseline.STI as a treatment strategy in HIV-infected patients with chronic unsuppressed viremia involves interrupting ART in controlled clinical settings, for a pre-specified duration of time. These interruptions have various aims, including the following: 1) to allow wild virus to re-emerge and replace the resistant mutant virus, with the hope of improving the efficacy of a subsequent ART regimen; 2) to halt development of drug resistance and to preserve subsequent treatment options; 3) to alleviate treatment fatigue and reduce drug-related adverse effects; and 4) to improve quality of life (Miller 2003; Montaner 2001; Vella 2000;).

OBJECTIVES

The objective of our systematic review was to synthesize the evidence on the effect of structured treatment interruptions in adult patients with chronic unsuppressed HIV infection.

SEARCH STRATEGY

We included all available intervention studies (randomized controlled trials and non-randomized trials) conducted in HIV-infected patients worldwide. We searched nine databases, covering the period from January 1996 to February 2006. We also scanned bibliographies of relevant studies and contacted experts in the field to identify unpublished research, abstracts and ongoing trials. In the first screen, a total of 3186 potentially eligible citations from nine databases and sources were identified, of which 2047 duplicate citations were excluded. The remaining 1139 citations were examined in detail, and we further excluded 951 citations that were modeling studies, animal studies, case reports, and opinion pieces. As shown in Figure 01, 188 citations were identified in the second screen as relevant for full-text screening. Of these, 60 basic science studies, editorials and abstracts were excluded and 128 full-text articles were retrieved. In the third screen, all full-text articles were examined for eligibility in our review. These were subclassified into three categories: 1) chronic suppressed HIV infection; 2) chronic unsuppressed HIV infection; and 3) acute HIV infection. Studies were further excluded if their abstracts did not contain enough information for inclusion in our reviews. A total of 62 studies were finally classified into chronic suppressed, acute, and chronic unsuppressed categories. Of these, 17 trials met the eligibility criteria for this review.

SELECTION CRITERIA

Inclusion criteriaAll available randomized or non-randomized controlled trials investigating planned treatment interruptions among patients with chronic unsuppressed HIV infection. Early pilot non-randomized prospective studies on treatment interruptions of fixed and variable durations were also included. Relevant abstracts on randomized controlled trials were also included if they contained sufficient information. Exclusion criteriaEditorials, reviews, modeling studies, and basic science studies were excluded. Studies on STI among patients with chronic suppressed HIV infection were summarized in a separate review. Studies on STI in primary HIV infection were beyond the scope of this review.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data, evaluated study eligibility and quality. Disagreements were resolved in consultation with a third reviewer.A total of seventeen studies on STI were included in our review. However, due to significant heterogeneity across studies (i.e. in study design, populations, baseline characteristics, and reported outcomes; and in reporting of measures of effect, hazard ratios, and risk ratios), we considered it inappropriate to perform a meta-analysis.

MAIN RESULTS

In early pilot non-randomized trials, a pattern was evident across studies. During treatment interruption, a decline in CD4 cell counts, increase in viral load, and a shift in the level of genotypic drug resistance towards more of a wild-type HIV virus was reported. This suggests that STI may be used to increase drug susceptibility to an optimized salvage regimen upon treatment re-initiation. These studies generated useful data and hypotheses that were later tested in randomized controlled trials. Randomized controlled trials rated high on quality. Of the eight randomized controlled trials reviewed, seven had been completed while one was ongoing and remains blinded. Of the seven completed randomized controlled trials, six have reported consistent virologic and immunologic patterns, and found no significant benefit in virologic response to subsequent ART in the STI arm, compared to the control arm. In addition, the largest completed randomized trial reported greater numbers of clinical disease progression events and evidence of prolonged negative impact on CD4 cell counts in the STI arm (Beatty 2005; Benson 2004; Deeks 2001; Lawrence 2003; Walmsley 2005; Ruiz 2003). The single RCT with divergent findings from the others (GigHAART), reporting a significant virologic and immunologic benefit due to STI, was different in prescribing a shorter STI duration and a salvage ART regimen of 8-9 drugs. There were also differences in the patient population characteristics with this study, targeting those with very advanced HIV disease (Katlama 2004). Although we await the unblinded results of the eighth RCT (OPTIMA), the evidence so far does not support STI in the setting of chronic unsuppressed HIV infection with antiretroviral treatment failure (Brown 2004; Holodniy 2004; Kyriakides 2002; Singer 2006).

AUTHORS' CONCLUSIONS

The current available evidence primarily supports a lack of benefit of STI before switching therapy in patients with unsuppressed HIV viremia despite ART. There is evidence of harm in attempting STI in patients with relatively advanced HIV disease, due to the associated CD4 cell decline and the increased risk of clinical disease progression. At this time, there is no evidence to recommend the use of STI in this clinical category of patients with treatment failure.

The effects of early antiretroviral therapy and its discontinuation on the HIV-specific antibody response

HIV-specific antibodies become detectable and continue to increase in frequency during primary infection. The effects of early antiretroviral treatment (ART) and its discontinuation on the evolution of this immune response have not been systematically analyzed. To investigate the associations between antibody titer, viral load, and ART, we used a less-sensitive enzyme-linked immunosorbant assay (LS-EIA) to measure changes in HIV-1-specific antibody levels in treated and untreated subjects undergoing primary infection. In this longitudinal study, antibody levels gradually increased in therapy-naive subjects, reaching a plateau approximately 40 weeks postinfection. In contrast, antibody titers remained low among subjects receiving ART. Subjects who discontinued ART exhibited a more rapid rise in antibody titers than therapy-naive subjects, suggesting the presence of an enhanced B cell response. These results demonstrate that early ART prevents the typical evolution of the HIV-1-specific antibody response and can alter the expected kinetics of this response in subjects discontinuing therapy.

Dynamics of T cells subsets and lymphoproliferative responses during structured treatment interruption cycles and after definitive interruption of HAART in early chronic HIV type-1-infected patients

Little is known about the consequences of short cycles of structured treatment interruption or definitive interruption of HAART for both T cell subset dynamics and T lymphoproliferative responses (LPR). Immunological follow-up was performed in 45 early chronical HIV-1-infected patients during short STI cycles during the first 12 weeks after the definitive interruption of HAART (DTI) and, thereafter, until VL reached a plateau. During STI cycles, CD8(+), CD8(+), CD28(+), activation markers and naive CD4(+) T cells increased significantly (p < 0.0001), while both naive CD8(+) and memory CD4(+) T cells decreased. During DTI, CD8(+) CD28(+) T cells fell and CD4(+) naive T cells stabilized and the rest of the T cell subsets presented changes similar to those during STI cycles. Despite a transient increase in LPR to recall antigens and HIV proteins during STI cycles, LPR to polyclonal stimuli and pathogens decreased over the study. Differences in T cell subset dynamics and LPR observed throughout the study suggest that multiple exposures to low levels of antigen could improve the immune system, mainly by driving T cell maturation. Conversely, higher and longer viral replication after cessation of HAART overwhelms the immune system. These data may help to guide future immune-based therapies.

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.