Changes in CD4+ T-cell differentiation phenotype during structured treatment interruption in patients with chronic HIV-1 infection

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.

Large number of rebounding/founder HIV variants emerge from multifocal infection in lymphatic tissues after treatment interruption

Antiretroviral therapy (ART) suppresses HIV replication in most individuals but cannot eradicate latently infected cells established before ART was initiated. Thus, infection rebounds when treatment is interrupted by reactivation of virus production from this reservoir. Currently, one or a few latently infected resting memory CD4 T cells are thought be the principal source of recrudescent infection, but this estimate is based on peripheral blood rather than lymphoid tissues (LTs), the principal sites of virus production and persistence before initiating ART. We, therefore, examined lymph node (LN) and gut-associated lymphoid tissue (GALT) biopsies from fully suppressed subjects, interrupted therapy, monitored plasma viral load (pVL), and repeated biopsies on 12 individuals as soon as pVL became detectable. Isolated HIV RNA-positive (vRNA+) cells were detected by in situ hybridization in LTs obtained before interruption in several patients. After interruption, multiple foci of vRNA+ cells were detected in 6 of 12 individuals as soon as pVL was measureable and in some subjects, in more than one anatomic site. Minimal estimates of the number of rebounding/founder (R/F) variants were determined by single-gene amplification and sequencing of viral RNA or DNA from peripheral blood mononuclear cells and plasma obtained at or just before viral recrudescence. Sequence analysis revealed a large number of R/F viruses representing recrudescent viremia from multiple sources. Together, these findings are consistent with the origins of recrudescent infection by reactivation from many latently infected cells at multiple sites. The inferred large pool of cells and sites to rekindle recrudescent infection highlights the challenges in eradicating HIV.

A cure for AIDS: a matter of timing?

Despite the huge clinical success of antiretroviral therapy, several factors such as side effects, requirement of life-long adherence, high cost, incomplete access to therapies and development of drug resistance make the quest for an ultimate cure of HIV/AIDS a worldwide priority of biomedical research. In this respect, several sterilizing or functional cures have been reported in the last years in both non-human primates and humans. This review provides a summary of the main results achieved so far, outlining their strengths as well as their limitations. A synthetic interpretation of these results could be pivotal in order to develop an effective and widely available cure.

The immunological and virological consequences of planned treatment interruptions in children with HIV infection

OBJECTIVES

To evaluate the immunological and viral consequences of planned treatment interruptions (PTI) in children with HIV.

DESIGN

This was an immunological and virological sub-study of the Paediatric European Network for Treatment of AIDS (PENTA) 11 trial, which compared CD4-guided PTI of antiretroviral therapy (ART) with continuous therapy (CT) in children.

METHODS

HIV-1 RNA and lymphocyte subsets, including CD4 and CD8 cells, were quantified on fresh samples collected during the study; CD45RA, CD45RO and CD31 subpopulations were evaluated in some centres. For 36 (18 PTI, 18 CT) children, immunophenotyping was performed and cell-associated HIV-1 DNA analysed on stored samples to 48 weeks.

RESULTS

In the PTI group, CD4 cell count fell rapidly in the first 12 weeks off ART, with decreases in both naïve and memory cells. However, the proportion of CD4 cells expressing CD45RA and CD45RO remained constant in both groups. The increase in CD8 cells in the first 12 weeks off ART in the PTI group was predominantly due to increases in RO-expressing cells. PTI was associated with a rapid and sustained increase in CD4 cells expressing Ki67 and HLA-DR, and increased levels of HIV-1 DNA.

CONCLUSIONS

PTI in children is associated with rapid changes in CD4 and CD8 cells, likely due to increased cell turnover and immune activation. However, children off treatment may be able to maintain stable levels of naïve CD4 cells, at least in proportion to the memory cell pool, which may in part explain the observed excellent CD4 cell recovery with re-introduction of ART.

Phenotypic and functional profiling of CD4 T cell compartment in distinct populations of healthy adults with different antigenic exposure

Background

Multiparameter flow cytometry has revealed extensive phenotypic and functional heterogeneity of CD4 T cell responses in mice and humans, emphasizing the importance of assessing multiple aspects of the immune response in correlation with infection or vaccination outcome. The aim of this study was to establish and validate reliable and feasible flow cytometry assays, which will allow us to characterize CD4 T cell population in humans in field studies more fully.

Methodology/Principal Findings

We developed polychromatic flow cytometry antibody panels for immunophenotyping the major CD4 T cell subsets as well as broadly characterizing the functional profiles of the CD4 T cells in peripheral blood. We then validated these assays by conducting a pilot study comparing CD4 T cell responses in distinct populations of healthy adults living in either rural or urban Kenya. This study revealed that the expression profile of CD4 T cell activation and memory markers differed significantly between African and European donors but was similar amongst African individuals from either rural or urban areas. Adults from rural Kenya had, however, higher frequencies and greater polyfunctionality among cytokine producing CD4 T cells compared to both urban populations, particularly for “Th1” type of response. Finally, endemic exposure to malaria in rural Kenya may have influenced the expansion of few discrete CD4 T cell populations with specific functional signatures.

Conclusion/Significance

These findings suggest that environmentally driven T cell activation does not drive the dysfunction of CD4 T cells but is rather associated with greater magnitude and quality of CD4 T cell response, indicating that the level or type of microbial exposure and antigenic experience may influence and shape the functionality of CD4 T cell compartment. Our data confirm that it is possible and mandatory to assess multiple functional attributes of CD4 T cell response in the context of infection.

Central memory CD4 cells are an early indicator of immune reconstitution in HIV/AIDS patients with anti-retroviral treatment

The number of central memory cells among the CD4+ T cells and the of activation of CD8+ T cells is believed to be a better indicator of immune restoration in patients on antiretroviral therapy (ART) than the absolute numbers of CD4(+) and CD8+ T cells alone. In the current study, we investigated the changes in the CD4(+) T cell subsets and their association with immune reconstitution and immune activation at early stages of ART. A prospective study was performed in 21 asymptomatic treatment-naive HIV-infected patients with CD4(+) T cells less than 350 cells/μl. Blood samples were evaluated at base line, and at 2, 4, 8 and 12 weeks' post antiretroviral therapy (ART). A biphasic increase of CD4(+) T cells, central memory CD4 cells (CD4 CM) and CD4 naïve cells were observed after ART, with a rapid increase before week 4. Change in CD4 CM at week 4 positively correlated with the change in CD4(+) T cells at weeks 12 post ART, and negatively correlated with the change in CD8(+)CD38(+) T cells at weeks 12 post ART. We conclude that CD4 CM cells are a major contributor to early immune reconstitution in treatment-naive HIV-infected patients with delayed ART, and might be an early indicator for immune reconstitution.

Immunological analysis of treatment interruption after early highly active antiretroviral therapy

We longitudinally evaluated HIV-specific T-cell immunity after discontinuation of highly active antiretroviral therapy (HAART). After treatment interruption (TI), some individuals could maintain a low plasma viral load (<15,000 copies/mL), whereas others could not (>50,000 copies/mL). Before HAART was initiated, plasma viral load was similar. After TI, the numbers of CD8(+) T cells increased more in individuals without viral control, whereas individuals maintaining a low viral load showed a more pronounced increase in HIV-specific CD8(+) T-cell numbers. No differences were seen in the number or percentage of cytokine-producing HIV-1-specific CD4(+) T cells, or in proliferative capacity of T cells. Four weeks after TI, the magnitude of the total HIV-1-specific CD8(+) T-cell response (IFN-γ(+) and/or IL-2(+) and/or CD107a(+)) was significantly higher in individuals maintaining viral control. Degranulation contributed more to the overall CD8(+) T-cell response than cytokine production. Whether increased T-cell functionality is a cause or consequence of low viral load remains to be elucidated.

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.

Evaluation of a simplified dual-platform flow cytometric method for measurement of lymphocyte subsets and T-cell maturation phenotypes in the population of Nouna, Burkina Faso

In the context of a larger clinical study in Nouna, Burkina Faso, we evaluated a simplified dual-platform (DP) flow cytometric (FCM) method that allows the determination of major lymphocyte subsets in a single test tube. We compared the phenotyping of lymphocytes with DP FCM and simultaneous measurements with standard single-platform (SP) FCM for samples from 177 individuals. Analysis of the comparative measurements revealed that DP FCM systematically underestimates the proportion of NK cells, overestimates the percentage of CD3(+) CD8(+) lymphocytes, and yields proportions of B cells and CD4(+) T cells comparable with the results from SP FCM. Bland-Altman analysis showed a low bias between both methods and an acceptable precision for percent values of CD4(+) T cells (bias +/- precision, -1% +/- 6%) and CD8(+) T cells (-3% +/- 6%). The absolute cell numbers of all lymphocyte subpopulations, however, were systematically biased towards lower values being obtained by DP FCM. Reference values for the distribution of T-cell maturation phenotypes in 177 healthy adults were calculated using DP FCM. The mean +/- standard deviation (SD) CD4(+)-to-CD8(+) T-cell ratio was 1.61 +/- 0.61, the mean percentage +/- SD of CD4(+) T cells was 42% +/- 7%, and that of CD8(+) T cells 29% +/- 7%. Among CD4(+) lymphocytes, 28% +/- 7% were classified as central memory (CD45RA(low) CCR7(+)), 22% +/- 10% as naïve (CD45RA(high) CCR7(+)), 45% +/- 12% as effector memory (CD45RA(low) CCR7(-)); and 5% +/- 3% as terminally differentiated effector memory expressing CD45RA (CD45RA(high) CCR7(-)). Among CD8(bright) lymphocytes, 3% +/- 2% had a central memory phenotype, 27% +/- 13% were naïve, 37% +/- 13% had an effector memory phenotype, and 34% +/- 12% were terminally differentiated effector memory cells expressing CD45RA.

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.

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.

Functional regulatory T cells are collected in stem cell autografts by mobilization with high-dose cyclophosphamide and granulocyte colony-stimulating factor

High-dose cyclophosphamide (Cy) and G-CSF are widely used to mobilize hemopoietic stem cells for treating patients with high-dose chemotherapy and autologous stem cell transplantation (ASCT). Because lymphocyte count in the graft collected after Cy-G-CSF treatment is an independent survival factor after ASCT for patients with multiple myeloma, our purpose was to study how Cy-G-CSF treatment affects the phenotype and function of T cells in patients with multiple myeloma. Cy induced a 3-fold decrease of T cell counts with a slow and partial T cell recovery of one-third at the time of hemopoietic stem cell collection. Cy-G-CSF treatment did not affect the relative ratios of central memory, effector memory, and late effector CD4+ or CD8+ T cells, but a decrease in the percentage of naive CD4+ cells was observed. The percentages of CD25+ cells increased 2- to 3-fold in CD4+ and CD8+ T cells, the former including both activated CD25low and CD25high cells. CD4+CD25high cells were regulatory T cells (Treg) that expressed high levels of FOXP3, CTLA-4, and GITR and displayed in vitro suppressive properties. The recovery of Treg absolute counts after Cy-G-CSF treatment was higher than the recovery of other lymphocyte subpopulations. In conclusion, Cy-G-CSF treatment induces a severe T cell count decrease without deleting Treg, which are potent inhibitors of antitumor response. The present data encourage novel therapeutic strategies to improve T cell recovery following ASCT while limiting Treg expansion.

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.

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.

Distinct patterns of HIV-specific memory T lymphocytes in HIV-exposed uninfected individuals and in HIV-infected patients

BACKGROUND

Repeated exposure to HIV is not always associated with infection and multiple cohorts of HIV-exposed but seronegative individuals (ESN) have been described. HIV-specific CD4 and CD8 T lymphocytes are detected both in HIV patients and in ESN; we verified whether different patterns of HIV-specific memory T lymphocytes would be detected in individuals in whom exposure to HIV results or does not result in infection.

METHODS

Gag-specific T cells were analysed in 15 ESN, 14 HIV patients, and 15 healthy controls using extensive flow cytometry analysis.

RESULTS

Data confirmed that gag-specific T lymphocytes are present in ESN. Gag-specific T cells mainly secrete interleukin-2 in ESN and interferon-gamma in HIV patients. In addition the CD4/CD8 and the memory/naive ratios are altered, central memory (45RA-/CCR7+) CD4 and CD8 T lymphocytes are more abundant, and terminally differentiated (45RA+/CCR7- and 27-/28-) CD8 T lymphocytes are augmented in ESN individuals.

CONCLUSIONS

Exposure to HIV occurs in high risk seronegative individuals; the observation that naive cells and CM are skewed in ESN indicate that this exposure is robust enough to modulate the CM/EM ratio. The increase in late effectors and in natural killer cells seen in ESN suggests a role for these cells in preventing actual infection.

Interrupting highly active antiretroviral therapy in patients with HIV

Scheduled treatment interruptions are preplanned interruptions of antiretroviral treatment, which may be directed by time (e.g., cycles of 8 weeks on treatment and 8 weeks off treatment); the concentration of CD4+ lymphocytes (the CD4 count); HIV-1 RNA concentration (viral load); or other factors. This review covers the rationale of scheduled treatment interruptions and the different strategies that have been explored. It examines the issue of autovaccination, resistance and other risks and benefits. Scheduled-treatment-interruption studies in three populations are discussed: patients who initiated highly active antiretroviral therapy during acute HIV infection; patients with successfully treated chronic HIV infection; and patients with highly active antiretroviral therapy failure.

Mitochondrial Abnormalities in HIV-Infected Lipoatrophic Patients Treated With Antiretroviral Agents

BACKGROUND

Lipodystrophy is now widely described in HIV infected patients under antiretroviral regimen with important psychological impact. But physiopathology of loss of fat mass is still debated and the role of mitochondrial impairment is not clearly defined.

OBJECTIVE

To correlate clinical lipoatrophy (LA) in HIV patients with long-term treatment by nucleoside reverse transcriptase inhibitors (NRTIs) and muscular impairment related to mitochondrial dysfunction.

METHODS

Ten consecutive patients with clinical LA and 10 nonlipodystrophic (NLD) individuals on antiretroviral therapy were included. Patients underwent the following investigations: dual-energy x-ray absorptiometry (DEXA) scanning and lactate kinetics during standardized exercise. The mitochondrial respiratory complex activity (III and IV) and histoenzymatic abnormalities (classified as none, mild, or severe) were evaluated on muscle tissue obtained by biopsy in deltoid muscle.

RESULTS

Mean NRTI exposure was longer in the LA group than in the NLD group (81 +/- 30 months vs. 59 +/- 15 months), but mean protease inhibitor exposure was identical in both groups. Mean fat mass distribution for leg in the LA and NLD groups was 860 +/- 381 g versus 1895 +/- 999 g, respectively. The lactic acidosis threshold during exercise was reached in the LA group at lower workloads (mean: 45 +/- 17 W in the LA group vs. 68 +/- 11 W in the NLD group), and maximum power output exercise was restricted in LA patients (mean: 115 +/- 30 W vs. 153 +/- 28 W). Total complex activities in muscular tissue were lower in LA patients: the median (range) for complex III was 67 (1-128) versus 112 (28-143), and the median (range) for complex IV was 28 (1-70) versus 42 (1-75). Six patients had severe histoenzymatic abnormalities in the LA group versus none in the NLD group.

CONCLUSION

Clinical LA, confirmed by DEXA, in long-term NRTI-treated patients was associated with muscular mitochondrial dysfunction as shown by rapid lactic acidemia increase, impairment of respiratory chain activity for complexes III and IV, and mitochondrial histoenzymatic abnormalities.