Structured treatment interruptions in HIV/AIDS therapy

Socioeconomic and clinical factors explaining the risk of unstructured antiretroviral therapy interruptions among Kenyan adult patients

A cross-sectional study was conducted to assess the extent of unstructured HIV treatment interruptions (TIs) and investigate the effects of socioeconomic, socio-demographic, HIV treatment-related and clinical factors on the magnitude and rate of the same among adult patients at a Kenyan regional referral center. Four hundred and twenty-one adult patients actively receiving antiretroviral therapy at Nyeri County Referral Hospital since 2003 were randomly selected to complete a health survey questionnaire. Electronic records were used to obtain their HIV treatment utilization history. The marginal effects of selected determinants on prevalence and rate of TI were assessed by fitting multiple Poisson log-linear regression models. In total, 392 patients participated in the study. HIV TI was prevalent with 64.5% having had at least one TI of 3 months or more during treatment. The risk of TI was significantly higher in those longer on treatment (prevalence ratio = 1.2, 95% confidence interval [CI] 1.12-1.28). Greater risk of TI was also associated with lower income (prevalence rate ratio [PRR] = 0.9, 95% CI 0.83-1.00), low medication adherence (PRR = 0.3, 95% CI 0.13-0.72), inconsistent treatment engagement (PRR = 0.4, 95% CI 0.19-0.75) and, contrarily, fewer adverse drug reactions (PRR = 0.9, 95% CI 0.90-0.97). Unstructured HIV TIs appear to be fairly common at the study site. The results suggest that efforts to minimize HIV TI could benefit from treatment-continuity monitoring strategies that target the high-risk sub-samples identified.

Screening Experiments for Developing Dynamic Treatment Regimes

Dynamic treatment regimes are time-varying treatments that individualize sequences of treatments to the patient. The construction of dynamic treatment regimes is challenging because a patient will be eligible for some treatment components only if he has not responded (or has responded) to other treatment components. In addition there are usually a number of potentially useful treatment components and combinations thereof. In this article, we propose new methodology for identifying promising components and screening out negligible ones. First, we define causal factorial effects for treatment components that may be applied sequentially to a patient. Second we propose experimental designs that can be used to study the treatment components. Surprisingly, modifications can be made to (fractional) factorial designs - more commonly found in the engineering statistics literature -for screening in this setting. Furthermore we provide an analysis model that can be used to screen the factorial effects. We demonstrate the proposed methodology using examples motivated in the literature and also via a simulation study.

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.

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.

Anti-CD3/28 mediated expansion of macaque CD4+ T cells is polyclonal and provides extended survival after adoptive transfer

BACKGROUND

Our lab has previously shown that adoptive transfer of in vitro expanded autologous purified polyclonal CD4(+) T cells using anti-CD3/CD28 coated beads induced antiviral responses capable of controlling simian immunodeficiency virus (SIV) replication in vivo.

RESULTS

Expansion on anti-CD3/28 coated beads was found to induce a true polyclonal expansion as CFSE labeled cells uniformly showed dilution of the dye over several days of culture, in contrast to aliquots of the same cells subjected to mitogen stimulation. Of interest was the finding that CD4(+) T cells collected before and during early chronic SIV infection or AIDS stage did not show any or only modest differences in proliferative response or expansion kinetics. The reason for such excellent expansion properties was analyzed by the quantitation of telomerase activity in aliquots of expanding CD4(+) T cells from sample collected at various times post-infection. First, anti-CD3/28 expanded CD4(+) T cells exhibited telomerase levels 2- to 20-fold higher than the starting population of CD4(+) T cells. Moreover, while telomerase activity in ex vivo tested CD4(+) T cells was found to decrease following SIV infection and disease progression, anti-CD3/28 expansion appeared to restore significant levels of telomerase activity as no difference was noted in telomerase expression between CD4(+) T cells expanded from samples collected before or during the chronic SIV infection. When such expanded and CFSE labeled T cells were autologously transferred to monkeys, evidence for extended survival in vivo was provided as CFSE labeled cells were detected to relatively high levels in blood and spleen at 1 week post-infection.

CONCLUSION

In summary, the data suggest that anti-CD3/28 mediated expansion of CD4(+) T cells retains its immunotherapeutic potential not only during the early stages of lentiviral infection but also at more advanced stages of disease.

In Silico Modeling in Infectious Disease

Infectious disease has witnessed the emergence of mathematical modeling a tool of synthesizing data of growing complexity now available to clinicians and basic scientists alike. The purpose of this review is to introduce mathematical tools commonly used to model infectious disease. We will illustrate the use of equation-based, agent-based or statistical modeling approaches to a variety of examples pertaining to acute inflammation, bacterial dynamics, viral dynamics, and signaling pathways, focusing of host-pathogen interactions rather than population models. We will discuss the strengths and weaknesses of these approaches and offer future perspectives for this rapidly evolving field.

Trevor Trust – AstraZeneca R&D Boston, 35 Gatehouse Drive, Waltham, MA 02451, USA

Drug-Sparing Regimens for HIV Combination Therapy: Benefits Predicted for “Drug Coasting”

Structured Treatment Interruptions (STI) during HIV drug therapy were thought to potentially reduce side effects and toxicity, boost immune involvement, and possibly lower the viral set-point. Clinical trials of STI regimens, however, have had mixed results. We use an established mathematical model of HAART to estimate possible therapeutic outcomes for STI and for other, similar patterns in HIV combination therapy. We perform an exhaustive search of patterns of up to 60 days, for triple-drug combinations involving accurate pharmacokinetics for 12 specific antiviral drugs. The results of this analysis are consistent with recent clinical trials which have demonstrated that STI-type patterns, involving therapy interruption of weeks or months, are rarely optimal. Our analysis predicts, however, that the benefit of treatment can often be improved by including very short drug-free periods, during which the patient effectively "coasts" for a day or two on adequate drug concentrations due to the long half-life of some pharmaceuticals. Our analysis predicts many cases in which this may be achieved without increasing the risk of drug-resistance. This suggests that "drug coasting" patterns, significantly shorter than STI patterns, may merit further clinical investigation in efforts to find drug-sparing regimens for HIV.

Optimization of in vitro expansion of macaque CD4 T cells using anti-CD3 and co-stimulation for autotransfusion therapy

BACKGROUND

Our laboratory has previously shown that adoptive transfer of in vitro-expanded autologous purified polyclonal CD4(+) T cells using anti-CD3/CD28-coated beads induced antiviral responses capable of controlling SIV replication in vivo.

METHODS

As CD4(+) T cells comprise several phenotypic and functional lineages, studies were carried out to optimize the in vitro culture conditions for maximal CD4(+) T-cell expansion, survival and delineate the phenotype of these expanded CD4(+) T cells to be linked to maximal clinical benefit.

RESULTS AND CONCLUSIONS

The results showed that whereas anti-monkey CD3gamma/epsilon was able to induce T-cell proliferation and expansion in combination with antibodies against multiple co-stimulatory molecules, monkey CD3epsilon cross reacting antibodies failed to induce proliferation of macaque CD4(+) T cells. Among co-stimulatory signals, anti-CD28 stimulation was consistently superior to anti-4-1BB, CD27 or ICOS while the use of anti-CD154 failed to deliver a detectable proliferation signal. Increasing the relative anti-CD28 co-stimulatory signal relative to anti-CD3 provided a modest enhancement of expansion. Additional strategies for optimization included attempts to neutralize free radicals, enhancement of glucose uptake by T cells or addition of T-cell stimulatory cytokines. However, none of these strategies provided any detectable proliferative advantage. Addition of 10 autologous irradiated feeder cells/expanding T cell provided some enhancement of expansion; however, given the high numbers of T cell needed, this approach was deemed impractical and costly, and lower ratios of feeder to expanding T cells failed to provide such benefit. The most critical parameter for efficient expansion of purified CD4(+) T cells from multiple monkeys was the optimization of space and culture conditions at culture inception. Finally, anti-CD3/28-expanded CD4(+) T cells uniformly exhibited a central memory phenotype, absence of CCR5 expression, marked CXCR4 expression in vitro, low levels of caspase 3 but also of Bcl-2 expression.

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.

Immunological and virological consequences of patient-directed antiretroviral therapy interruption during chronic HIV-1 infection

Increasing numbers of patients are choosing to interrupt highly active antiretroviral therapy (HAART). We describe the effect of patient-directed treatment interruption (PDTI) on plasma viral loads (pVL), proviral DNA (pDNA), lymphocyte subsets and immune responses in 24 chronically HIV-1 infected individuals. Patients were divided into group A with pVL > 50 copies/ml and group B with pVL < 50 copies/ml, prior to the PDTI. pVL rose significantly in group B during the first month off HAART and was associated with a significant decrease in CD4 T-cell count. At baseline there was a significant difference in HIV-1 pDNA levels between groups A and B, however, levels significantly increased in group B, but not in group A during PDTI becoming equivalent after 1 month PDTI. We have previously shown no increase in pDNA over the time of substitution in patients switching HAART regimens despite a small rebound in pVL. These observations indicate that to protect low pDNA levels PDTI should be discouraged and that changing regimen at the first sign of failure should be advised where possible. Only transient, no longer than 4 week, HIV-1-specific responses were observed during PDTI in 5/24 patients, 2 from group A and 3 from group B. The low numbers of responders and the transient nature of the anti-HIV-1 immune responses do not favour the auto-vaccination hypothesis.

Interruption thérapeutique chez des patients infectés par le virus de l'immunodéficience humaine : évolution clinique et biologique

OBJECTIVE

The authors had for aim to evaluate the clinical and biological evolution in HIV-infected patients with viraemia lower than 30,000 copies/mL having decided to interrupt their treatment.

PATIENTS AND METHODS

Patients with highly active antiretroviral therapy (HAART) for more than 3 months followed by treatment interruption longer than 1 month were included in a retrospective analysis.

RESULTS

Forty-six patients having stopped treatment between November 1999 and July 2003 were included. The median duration of treatment interruption was 9.5 months. During the study, no clinical event occurred for 21 patients, and at least 1 clinical event occurred for the 25 others. The median CD4(+) cell counts (CD4) before and at the end of treatment interruption were 597/mm(3) and 437/mm(3), respectively (P<0.001). The median values of viral load before and at the end of treatment interruption were <50 and 23749 copies/mL, respectively (P<0.001). Among the 26 patients having started a new HAART, pre-treatment interruption and post-new HAART median CD4 (with a median delay after HAART of 9.7 months) were 548 and 432.5/mm(3) (P=0.02). Pre-treatment interruption and post-new HAART median viral load were 131.5 and 94.5 copies/mL (NS).

CONCLUSIONS

Treatment interruption must be used with caution in spite of the absence of virological impact, because CD4 cell count after new HAART is lower than CD4 preceding treatment interruption. Treatment interruption is contraindicated for patients with AIDS. Physicians must carefully follow other patients who decide on a treatment interruption.

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.

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.

Novel peptide-based HIV-1 immunotherapy

Therapeutic immunisation of human immunodeficiency virus type 1-infected individuals should be actively pursued in the first instance to augment highly active antiretroviral therapy regimens. Peptide-based immunotherapeutic strategies offer considerable advantages over conventional approaches, particularly regarding safety. Peptide design itself is becoming increasingly sophisticated, with the rapid evolution of bioinformatics tools that can analyse not only T cell epitopes, but also their potential for successful presentation on diverse human leukocyte antigen (HLA) class I or II following intracellular processing by antigen-presenting cells (APCs). By targeting conserved viral domains, peptides acquire improved reactivity to diverse viral strains. Dendritic cells represent a powerful route of administration, as they are the most potent APCs and can present exogenous peptides on both HLA class I and II through the process of cross-presentation. In this way, soluble peptides can thereby stimulate both CD4+ and CD8+ T cells.

Drug resistance and adherence to HIV/AIDS antiretroviral treatment: against a double standard between the north and the south

Here we review the available evidence on adherence to highly active antiretroviral therapy (HAART) and its relationship with the risk of the dissemination of HIV-resistant viral strains in both developed and developing countries. We argue that referring to these issues of resistance and adherence to withhold or delay access to HAART in developing countries implicitly imposes a double standard of thinking that is unacceptable. Scaling-up access to HAART to succeed in low-resource settings, however, requires the long-term monitoring of adherence as well as the clarification of the complex trade-offs between minimizing the costs of therapeutic regimens and minimizing the risks of non-adherence and resistance.

An open-label randomized clinical trial of novel therapeutic strategies for HIV-infected patients in whom antiretroviral therapy has failed: rationale and design of the OPTIMA Trial

OPTIMA (OPTions In Management with Antiretrovirals) is a clinical trial with a factorial randomization to evaluate the hypotheses that mega-antiretroviral therapy (ART) consisting of five or more anti-HIV drugs compared to standard-ART consisting of four or fewer anti-HIV drugs and a 3-month antiretroviral drug-free period (ARDFP) compared to no ARDFP will delay the occurrence of new or recurrent acquired immunodeficiency syndrome events or death, and prove to be more cost-effective in treating human immunodeficiency virus-infected individuals previously exposed to ART drugs from the current three main classes. The aim is to randomize 1,700 participants to four treatment strategy arms: (1) ARDFP+standard-ART; (2) ARDFP+mega-ART; (3) no ARDFP+standard-ART; (4) no ARDFP+mega-ART. The planned study duration is 3.5 years with 2.5 years of intake and a minimum 1 year of follow-up. The OPTIMA Trial was initiated in June 2001 at 30 U.S. Department of Veterans' Affairs hospitals, 22 hospitals in Canada, and 25 hospitals in the United Kingdom. This is the first large-scale, multicenter, randomized controlled trial to compare the relative efficacy of these different therapeutic strategies. We discuss the rationale behind the OPTIMA Trial design as well as the issues arising from the conduct of a trial that involves three national clinical trial agencies.

Management of severely immunocompromised human immunodeficiency virus type 1-infected African orphans with structured treatment interruption: another kind of salvage therapy

Without an effective therapeutic human immunodeficiency virus (HIV)-1 vaccine, providing cost-effective, minimally toxic antiretroviral therapy to the many individuals already infected with HIV-1 is a global priority. Implementation of a structured treatment interruption (STI) regimen may be a promising intervention for HIV-1 infection. We adopted this approach out of necessity for 3 severely immunocompromised African children naive to therapy, and increases in the T lymphocyte count and improved quality and sustainability of life 2 years after initiation of the STI regimen were noted.

HIV type 1 DNA development during long-term supervised therapy interruption

We studied the pattern of HIV-1 DNA development and the association to other HIV-related factors during long-term supervised therapy interruption (LT-STI). Fifteen patients were treated with long-time protease inhibitor-based antiretroviral therapy (PI-ART). They had HIV-1 RNA at <50 copies/ml over 33.4 (SD 9.5) months and CD4(+) cell counts of 875 (SD 415) x 10(6)/liter. A real-time polymerase chain reaction, amplifying fragments of the HIV-1 pol gene and the human albumin gene simultaneously, was used to quantify HIV-1 DNA molecules in CD4(+) cells. The quantity of HIV-1 DNA in CD4(+) cells increased during LT-STI in all 15 patients, with an average doubling time of 2 months. Tentatively, three patterns were observed: rapid initial increase with subsequent stabilizing levels, rapid continuous increase, and slow increase. The HIV-1 DNA slope was positively related to the HIV-1 RNA maximum and steady state level and the baseline HIV-1 DNA value. It was inversely related to the decrease in CD4(+) cells both before the start of PI-ART and during the LT-STI. To conclude, HIV-1 DNA persists in infected CD4(+) cells despite long-term effective PI-ART and will increase after therapy interruption. The most important clinical predictor of long-term STI failure was the rapid CD4(+) cell decline before PI-ART. In patients with a steep pre-PI-ART slope it may be prudent to continue treatment and not initiate therapy interruption.

Boosting immunity by antiviral drug therapy: a simple relationship among timing, efficacy, and success

Drug therapies against persistent human infections such as hepatitis C virus, hepatitis B virus, and HIV fail to consistently eradicate the infection from the host. Hence, recent emphasis has shifted to the study of antiviral therapy aimed at boosting specific immune responses. It was argued that structured therapy interruptions were required to achieve this, because such regimes have shown promising results in early HIV infection. Using mathematical models, we show that, contrary to this notion, a single phase of drug therapy can result in the establishment of sustained immunity. We present a simple relationship between timing of therapy and efficacy of the drugs required for success. In the presence of strong viral suppression, we show that therapy should be stopped relatively early, and that a longer duration of treatment leads to failure. On the other hand, in the presence of weaker viral suppression, stopping treatment too early is detrimental, and therapy has to be continued beyond a time threshold. We discuss our modeling results primarily in the context of HCV therapy during chronic infection. Although the therapy regimes explored here also have implications for HIV, virus-mediated destruction of specific immune cells renders success unlikely during the chronic phase of the infection.

Mathematical models of HIV pathogenesis and treatment

We review mathematical models of HIV dynamics, disease progression, and therapy. We start by introducing a basic model of virus infection and demonstrate how it was used to study HIV dynamics and to measure crucial parameters that lead to a new understanding of the disease process. We discuss the diversity threshold model as an example of the general principle that virus evolution can drive disease progression and the destruction of the immune system. Finally, we show how mathematical models can be used to understand correlates of long-term immunological control of HIV, and to design therapy regimes that convert a progressing patient into a state of long-term non-progression.