The virological and immunological consequences of structured treatment interruptions in chronic HIV-1 infection. A prospective, randomized trial of structured treatment interruption for patients with chronic HIV type 1 infection. Virologic, immunologic, clinical, safety, and resistance outcomes from a long-term comparison of efavirenz-based versus nevirapine-based antiretroviral regimens as initial therapy in HIV-1-infected persons. Effect of prolonged discontinuation of successful antiretroviral therapy on CD4 T cells: a controlled, prospective trial. Randomized, controlled trial of therapy interruption in chronic HIV-1 infection. Virologic and immunologic consequences of discontinuing combination antiretroviral-drug therapy in HIV-infected patients with detectable viremia. Virological and immunological effects of treatment interruptions in HIV-1 infected patients with treatment failure. HIV therapy after treatment interruption in patients with multiple failure and more than 200 CD4+ T lymphocyte count. A prospective trial of structured treatment interruptions in human immunodeficiency virus infection.
Some individuals with chronic HIV-1 infection have discontinued their drug therapy with consequent plasma virus rebound. In a small number of patients, a delayed or absent rebound in plasma virus load has been noted after drug cessation, apparently associated with prior drug interruptions and autologous boosting of HIV-1 specific immune responses. We hypothesized that cyclic structured treatment interruptions structured treatment interruptions (STI) could augment HIV-1 specific immune responses in chronic HIV-1 infection, which might help to control HIV-1 replication off therapy.
                We initiated an STI pilot study in 10 antiretroviral treatment-naive HIV-1 chronically infected subjects with baseline CD4 T-cell counts > 500 x 10(6) cells/l and plasma viral load > 5000 copies/ml who received highly active antiretroviral therapy (HAART) for 1 year with good response (plasma viral load < 20 copies/ml for at least 32 weeks). Three cycles of HAART interruption were performed.
                In all of the patients viral load rebounded, but doubling times increased significantly between the first and third stops (P = 0.008), and by the third stop, six out of nine subjects had a virological set-point after a median 12 months off therapy that was lower than baseline before starting HAART (ranging from 0.6 log(10) to 1.3 log(10) lower than baseline) and in four it remained stable below 5000 copies/ml. Those subjects who controlled viral replication developed significantly stronger HIV-1 specific cellular immune responses than subjects lacking spontaneous decline (P < 0.05). During viral rebounds no genotypic or phenotypic changes conferring resistance to reverse trancriptase inhibitors or protease inhibitors was detected, but mean absolute CD4 T-cell counts declined significantly, although never below 450 x 10(6)/l and the mean value at 12 months off therapy was significantly higher than the pre-treatment level (P = 0.004).
                Our findings suggest that STI in chronic HIV-1 infection might augment HIV-1-specific cellular immune responses associated with a spontaneous and sustained drop in plasma viral load in some subjects but at the potential cost of lower CD4 T-cell counts. Structured treatment interruption was evaluated in 74 patients who had been pretreated with antiretrovirals, consisting of 2 nucleoside reverse-transcriptase inhibitors (NRTIs) for 1 year followed by 3 years of highly active antiretroviral therapy containing a protease inhibitor.
                Patients with a CD4 cell count of > or =350 cells/microL and a plasma viral load of <50 copies/mL were randomized to 3 therapy arms: (1) continuous therapy, (2) CD4 cell count-guided theory, and (3) week-on/week-off (WOWO) therapy. The efficacy and safety of structured treatment interruption and antiretroviral use were evaluated in human immunodeficiency type 1 (HIV-1)-infected patients. The study end points were percentage of patients who developed AIDS or who died and a CD4 cell count of > or =350 cells/microL. Intergroup differences were analyzed using analysis of variance and Kruskal-Wallis tests.
                Baseline characteristics at the start of the structured treatment interruption were similar. At week 48, no patient had died, and 1 patient in the WOWO group had an AIDS-defining condition. The proportions of patients with a CD4 cell count of > or =350 cells/microL were 100%, 87%, and 96% in treatment arms 1, 2, and 3, respectively. The percentages of weeks of antiretroviral use were 100%, 41.1%, and 69.8% in arms 1, 2, and 3, respectively. The adverse events were not significantly different among arms (P=.27). Thirty-one percent of patients in the WOWO group experienced virological failure.
                WOWO therapy maintained a CD4 cell count of > or =350 cells/microL in almost all patients but was associated with high virological failures rates (possibly resulting from previous dual-NRTI therapy), indicating that this strategy is less useful. Receipt of CD4 cell count-guided therapy resulted in comparable clinical outcomes to continuous therapy and may save antiretroviral-associated costs, but this needs to be confirmed by a larger trial. To compare long-term virologic, immunologic, and clinical outcomes in antiretroviral-naïve persons starting efavirenz (EFV)- versus nevirapine (NVP)-based regimens.
                The FIRST study randomized patients into three strategy arms: PI+NRTI, NNRTI+NRTI, and PI+NNRTI+NRTI. NNRTI was determined by optional randomization (NVP or EFV) or by choice. For this randomized substudy, the primary endpoint was HIV RNA >50 copies/mL after 8 months or death. Genotypic resistance testing was done at virologic failure (VF; HIV RNA >1,000 copies/mL at or after 4 months).
                228 persons (111 randomized to EFV, 117 to NVP) were followed for median 5 years. Rates per 100 person years for the primary endpoint were 41.2 (EFV) and 42.8 (NVP; p = .59). The percent of persons with HIV RNA <50 copies/mL was similar throughout follow-up (p = .24), as were average increases in CD4+ cells (p = .30). 423 persons declining the substudy chose EFV; 264 chose NVP. There were 915 persons in the combined cohort (randomized and choice). In the combined cohort, the risk of VF and VF with any NNRTI or NRTI resistance or resistance of any class was significantly less for EFV compared to NVP.
                EFV-based regimens as initial therapy resulted in a lower risk of VF and VF with resistance than did NVP-based regimens, although immunologic and clinical outcomes were similar. To compare continuous highly active antiretroviral therapy with a CD4 cell count-driven structured treatment interruption (STI) strategy. The primary end-point was the proportion of subjects maintaining CD4 cell count > 400 x 10 cells/l. Secondary end-points were to identify the dynamic and predictive variables of CD4 cell loss.
                The BASTA study is a randomized, controlled, prospective trial. Patients with CD4 cell counts > 800 x 10 cells/l were enrolled and the immunological threshold to resume therapy was set to the lower normal limit of CD4 cells for HIV-uninfected adults.
                Sixty-nine patients were randomized and followed for 64 weeks. At baseline, all had undetectable plasma HIV RNA and their mean CD4 cell count was 1077 x 10 cells/l. None of the patients showed a disease progression or any AIDS-defining event. At each time point, the proportion of subjects in the STI group that had a CD4 cell count < 400 x 10 cells/l was not statistically different from the control group. In all cases, the 95% confidence interval for this difference was smaller than +/-10%. However, 57% of patients with nadir CD4 cell count 200-350 x 10 cells/l reached a CD4 cell count < 400 x 10 cells/l. This was statistically different (P = 0.02) from the nearly 90% of patients with a nadir CD4 cell count 350-500 x 10 cells/l who maintained a CD4 cell count of > 400 x 10 cells/l.
                Prolonged STI in patients with fully suppressed virus and marked immune reconstitution is generally safe. The main predictor of CD4 cell decline is the nadir CD4 cell count. Pulse therapy warrants further careful prospective evaluation to investigate virological and clinical outcomes over a very long period. Approaches to limiting exposure to antiretroviral therapy (ART) drugs are an active area of HIV therapy research. Here we present longitudinal follow-up of a randomized, open-label, single-center study of the immune, viral, and safety outcomes of structured therapy interruptions (TIs) in patients with chronically suppressed HIV-1 infection as compared to equal follow-up of patients on continuous therapy and including a final therapy interruption in both arms.
                Forty-two chronically HIV-infected patients on suppressive ART with CD4 counts higher than 400 were randomized 1:1 to either (1) three successive fixed TIs of 2, 4, and 6 wk, with intervening resumption of therapy with resuppression for 4 wk before subsequent interruption, or (2) 40 wk of continuous therapy, with a final open-ended TI in both treatment groups. Main outcome was analysis of the time to viral rebound (>5,000 copies/ml) during the open-ended TI. Secondary outcomes included study-defined safety criteria, viral resistance, therapy failure, and retention of immune reconstitution. There was no difference between the groups in time to viral rebound during the open-ended TI (continuous therapy/single TI, median [interquartile range] = 4 [1-8] wk, n = 21; repeated TI, median [interquartile range] = 5 [4-8] wk, n = 21; p = 0.36). No differences in study-related adverse events, viral set point at 12 or 20 wk of open-ended interruption, viral resistance or therapy failure, retention of CD4 T cell numbers on ART, or retention of lymphoproliferative recall antigen responses were noted between groups. Importantly, resistance detected shortly after initial viremia following the open-ended TI did not result in a lack of resuppression to less than 50 copies/ml after reinitiation of the same drug regimen.
                Cycles of 2- to 6-wk time-fixed TIs in patients with suppressed HIV infection failed to confer a clinically significant benefit with regard to viral suppression off ART. Also, secondary analysis showed no difference between the two strategies in terms of safety, retention of immune reconstitution, and clinical therapy failure. Based on these findings, we suggest that further clinical research on the long-term consequences of TI strategies to decrease drug exposure is warranted. In many patients with human immunodeficiency virus (HIV) infection, therapy with potent antiretroviral drugs does not result in complete suppression of HIV replication. The effect of cessation of therapy in these patients is unknown.
                Sixteen patients who had a plasma HIV RNA level of more than 2500 copies per milliliter during combination antiretroviral-drug therapy were randomly assigned, in a 2:1 ratio, to discontinue or continue therapy. Plasma HIV RNA levels, CD4 cell counts, and drug susceptibility were measured weekly. Viral replicative capacity was measured at base line and at week 12.
                Discontinuation of therapy for 12 weeks was associated with a median decrease in the CD4 cell count of 128 cells per cubic millimeter and an increase in the plasma HIV RNA level of 0.84 log copies per milliliter. Virus from all patients with detectable resistance at entry became susceptible to HIV-protease inhibitors within 16 weeks after the discontinuation of therapy. Drug susceptibility began to increase a median of six weeks after the discontinuation of therapy and was temporally associated with increases in plasma HIV RNA levels and decreases in CD4 cell counts. Viral replicative capacity, measured by means of a recombinant-virus assay, was low at entry into the study and increased after therapy was discontinued. Despite the loss of detectable resistance in plasma, resistant virus was cultured from peripheral-blood mononuclear cells in five of nine patients who could be evaluated. Plasma HIV RNA levels, CD4 cell counts, and drug susceptibility remained stable in the patients who continued therapy.
                Despite the presence of reduced drug susceptibility, antiretroviral-drug therapy can provide immunologic and virologic benefit. This benefit reflects continued antiviral-drug activity and the maintenance of a viral population with a reduced replicative capacity. To analyse the immunological and virological effects of treatment interruptions in HIV-1-infected patients with treatment failure and multidrug-resistant virus.
                Drug susceptibility was assessed using Antivirogram and genotypic analysis was based on population and clonal sequencing for 48 patients who had interrupted treatment (> or = 2 months).
                Treatment interruption resulted in viral load increases (mean 0.7 log 10 copies/ ml; P = 0.0001) and CD4 cell count decreases (mean 89 x 10(6) cells/l; P = 0.0001). A complete shift to wild-type virus at the phenotypic, genotypic and clonal level was observed in 28/45 patients. These patients differed from those that did not show a shift to wild type in baseline CD4 cell counts (192 versus 59 x 10(6) cells/l; P= 0.007) and in the relationship between baseline viral load and CD4 cell count (no correlation versus a significant negative correlation; P= 0.008). Response to re-initiation of treatment fell with increasing viral load [relative hazard (RH) 0.33; P= 0.001] and with increasing total number of drugs with reduced susceptibility (RH 0.51; P = 0.0003); it improved with the number of new drugs received (RH 2.12; P = 0.0002) and a shift to wild type (RH 5.22, P = 0.006).
                Changes in surrogate markers suggest that treatment provided benefit in spite of virological failure and resistant virus. Although patients with a shift to wildtype virus responded better in the short term to treatment re-initiation, the long-term effects are not known and the risk of immune deterioration needs to be carefully considered. The aim of the study was to investigate the safety and efficacy of a salvage therapy initiated after interrupting treatment in patients with virological failure and more than 200 CD4(+) T lymphocyte count. In this prospective study, 77 patients who received failing regimens had stopped completely all medication for 3 months before starting an optimised regimen consisting of 3-5 drugs. Patients were tested for HIV resistance before and after treatment interruption. Discontinuation of therapy for 3 months was associated with a median increase in HIV RNA of 1.1 log(10), a median decrease in CD4(+) T cell count of 136 x 10(6)/L and five clinical events related to HIV, but no AIDS-defining event. Eighty-seven percent of patients showed a shift from a drug resistant genotype to a wild-type genotype based on the major resistance mutations. Forty-seven percent of patients with a genotype shift reached fewer than 200 HIV RNA copies/ml of plasma 6 and 12 months after treatment resumption whereas none of those without a genotype shift did so (P = 0.03). However, the genotypic shift was not associated with a sustained virological response by multivariate analysis. The use of a new therapeutic class of compound in the salvage regimen was the only predictor of the sustained virological response. Salvage therapy with 3-5 drugs after interrupting treatment for 3 months can be a safe and effective strategy provided the HIV disease is not too advanced. Randomised trials in this population are needed to assess the clinical benefit of this strategy. According to the "autovaccination hypothesis," reexposure to human immunodeficiency virus (HIV) during treatment interruptions may stimulate the HIV-specific immune response and lead to low viremia after withdrawal of highly active antiretroviral treatment (HAART). Many patients who started HAART earlier in their disease course than is currently recommended would like to discontinue, but it is unknown whether it is safe to do so.
                To determine whether repeated treatment interruptions of HAART (1) stimulated the cytotoxic HIV-specific immune response and whether such stimulation correlated with low viremia off treatment, and (2) were safe with respect to clinical complications, development of viral resistance, and decline in CD4 cell counts.
                Interventional study with before-after comparison.
                Outpatient clinics of university hospitals in Switzerland and Spain.
                A total of 133 patients receiving HAART, with a median CD4 cell count of 740/ microL, and whose viral load had been undetectable for a median of 21 months.
                HAART was interrupted for 2 weeks, restarted, and continued for 8 weeks. After 4 such cycles, treatment was indefinitely suspended 40 weeks after study entry.
                HIV-specific cytotoxic T-cell responses were evaluated by interferon gamma enzyme-linked immunospot analysis. The proportion of "responders" (viral load <5000 copies/mL) was measured at weeks 52 and 96. HIV-related diseases and CD4 cell counts were recorded.
                Seventeen percent of patients (95% confidence interval, 11%-25%) were responders at week 52, and 8% at week 96. Low pre-HAART viral load and lack of rebound during weeks 0 to 40 predicted response. HIV-specific CD8+ T cells increased between week 0 (median, 343 spot-forming cells per million peripheral blood lymphocytes [SFC/106 PBL]) and week 52 (median, 1930 SFC/106 PBL), but there was an inverse correlation between response and the number of spot-forming cells. Eighty-five (64%) of 133 patients stopped therapy for at least 12 weeks, and 55 (41%) for at least 56 weeks. The median CD4 cell count decreased from 792/ microL to 615/ microL during the first 12 weeks without treatment, but stabilized thereafter. One patient (0.75%) developed drug resistance necessitating salvage treatment. There were no AIDS-related clinical complications.
                Results of this study do not favor the autovaccination hypothesis. Treatment interruptions did not provoke clinical complications, and there was little drug resistance. Comparative trials will have to show what benefit, if any, is associated with intermittent, as opposed to continuous treatment.
A limited number of studies were available to address this topic, and, of the two randomized trials identified, both were in abstract form only. Observational studies also were limited in number and were of lesser quality. Although the quality of the evidence varied from the randomized trials, ranging from very low to moderate, there appeared to be substantial benefits for key outcomes (e.g. mortality, AIDS-defining illness and mortality as a composite endpoint, and unnecessary switches) favoring both immunologic and clinical monitoring or virologic, immunologic, and clinical monitoring versus clinical monitoring alone. Very low-quality evidence from observational studies suggested that virologic, immunologic, and clinical monitoring led to more frequent switching, earlier switching, and switching at higher CD4 counts compared with immunologic and clinical monitoring. Further information on the studies currently reported in abstract form will provide insight. Ongoing studies addressing this topic likely will provide information to further clarify optimal monitoring strategies for guiding when to switch first-line therapy. Additionally, studies looking at different virologic monitoring frequencies and/or virologic monitoring at different times after ART initiation (e.g. after 2-3 years) would be informative. Finally, cost-analysis studies will lend further insights into the applicability of these findings to low-resource settings.