Development of HIV with drug resistance after CD4 cell count-guided structured treatment interruptions in patients treated with highly active antiretroviral therapy after dual-nucleoside analogue treatment. Structured treatment interruption in chronically HIV-1 infected patients after long-term viral suppression. HIV RNA in plasma rebounds within days during structured treatment interruptions. HIV dynamics and T-cell immunity after three structured treatment interruptions in chronic HIV-1 infection. Changes in CD4+ T-cell differentiation phenotype during structured treatment interruption in patients with chronic HIV-1 infection. Effect of prolonged discontinuation of successful antiretroviral therapy on CD4 T cells: a controlled, prospective trial. Structured antiretroviral treatment interruptions in chronically HIV-1-infected subjects. Influence of prior structured treatment interruptions on the length of time without antiretroviral treatment in chronically HIV-infected subjects. Relevance of HIV-1-specific CD4+ helper T-cell responses during structured treatment interruptions in patients with CD4+ T-cell nadir above 400/mm3. Stimulation of HIV-specific cellular immunity by structured treatment interruption fails to enhance viral control in chronic HIV infection. Emergence of minor populations of human immunodeficiency virus type 1 carrying the M184V and L90M mutations in subjects undergoing structured treatment interruptions.
For patients with human immunodeficiency virus (HIV) infection, structured treatment interruption (STI) is an attractive alternative strategy to continuous treatment, particularly in resource-restrained settings, because it reduces both side effects and costs. One major concern, however, is the development of resistance to antiretroviral drugs that can occur during multiple cycles of starting and stopping therapy.
                HIV genotypic drug resistance was investigated in 20 HIV-infected Thai patients treated with highly active antiretroviral therapy (HAART) and CD4 cell count-guided STI after dual nucleoside reverse-transcriptase inhibitor (NRTI) treatment. Resistance was tested at the time of the switch from dual-NRTI treatment to HAART and when HAART was stopped during the last interruption.
                After STI, one major drug-resistance mutation occurred (T215Y), and, in the 4 samples with preexisting major mutations (D67N [n=2], K70R [n=2], T215Y [n=2], and T215I [n=1]), the mutations disappeared. All mutations in the HIV protease gene were minor mutations already present, in most cases, before STI was started, and their frequency was not increased through STI, whereas the frequency of reverse-transcriptase gene mutations significantly decreased after the interruptions. After the 48-week study period, no patients had virological failure. Long-term follow-up (108 weeks) showed 1 case of virological failure in the STI arm and 1 in the continuous arm. No virological failure was seen in patients with major mutations.
                Major HIV drug-resistance mutations were not induced through CD4 cell count-guided treatment interruptions in HIV-infected patients successfully treated with HAART after dual-NRTI therapy. To investigate the virological and immunological impact of a structured treatment interruption (STI) in a cohort of HIV-1 chronically infected patients with a further long-lasting effective virus suppression.
                Twelve HIV-1 chronically infected adults who had maintained viral suppression (< 20 copies/ml) for more than 2 years, as well as a CD4:CD8 ratio > 1 for a median time of 22 months, were included in the study. Participants interrupted their antiretroviral treatment during a maximum period of 30 days or until a viral load rebound > 3000 copies/ml was detected. The same prior antiretroviral regimen was resumed after STI. Kinetics of plasma viral rebound was evaluated every 2 days during the treatment interruption period. Flow cytometry and cell proliferation assays were performed before and after STI. Genotypic resistance was assessed at the time of treatment resumption.
                No adverse events occurred during the interruption period. In two patients no viral rebound was detected after 30 days of treatment interruption. In the remaining 10 patients, viral load became detectable (> 20 copies/ml) at a median time of 14 days after treatment interruption. Afterwards, viral load increased exponentially with a mean t1/2 of 1.6 days. Treatment was successfully resumed in all patients. No resistance-conferring mutations associated with the pre-interruption antiretroviral regimen were detected. The percentage of CD4 and CD8 lymphocytes did not vary during the STI period; however, the level of expression of T-cell activation antigen CD38 on CD8 T cells increased significantly in response to viral rebound. Four patients gained T-helper cell responses to recall antigens (tuberculin and tetanus toxoid), two of who developed an HIV-specific response to p24.
                STI in chronically HIV-1-infected patients is not associated with reductions in CD4 T lymphocytes or to clinical complications in this group of patients after 2 years of effective plasma viral suppression. Viral load rebounds in most but not all patients, without evidence of selection of resistance-conferring mutations. Thereafter, viraemia can be effectively controlled by antiretroviral agent reintroduction. HIV-specific T-helper cell responses may be achieved after one cycle of treatment interruption suggesting some degree of immune-stimulation. These data do not discard consecutive cycles of STI as a therapeutic strategy to boost HIV-specific immunity in order to maintain viral replication under effective control. To evaluate time to viral rebound in patients undergoing repeated structured treatment interruptions (STI).
                Fourteen chronically HIV-infected patients enrolled in the Swiss-Spanish Intermittent Treatment Trial (SSITT) underwent frequent blood sampling. Patients underwent four cycles of 2-week STI, followed by 8-week retreatment with the identical antiretroviral treatment (HAART) used before STI. At the fifth cycle, treatment was stopped for a longer period. Before each new STI, plasma viral load (VL) had to reach < 50 copies/ml. VL was measured during day 0 (last day on HAART) and on days 4, 8 and 14 during all five STI.
                During the first cycle, plasma HIV RNA increased to > 50 copies/ml (range, 67-88) in five patients at day 4, in eight patients (> 100 copies/ml) at day 8 and in 12 patients (> 100 copies/ml) at day 14. Cumulative analysis of the frequency of detectable HIV RNA at days 4, 8 and 14 compared with day 0 for all five cycles revealed nine patients with VL > 50 copies/ml [13 of 54 samples tested (24.1%); = 0.14] at day 4, 11 patients [33 of 58 samples tested (56.9%); < 0.0001] at day 8 and 12 patients [53 of 65 samples tested (81.5%); < 0.0001] at day 14.
                Significant viral replication can be induced during 1 week STI, and this may increase the risk of the emergence of drug resistance during long-term cycling. Therefore, short-term cycling strategies such as 1-week-on, 1-week-off treatment, although conceptually intriguing, should still be regarded as investigational and should be restricted to rigorously controlled clinical trials ideally involving patients who have never failed treatment before. To evaluate whether controlled re-exposures to autologous HIV-1 could boost HIV-specific immunity and limit virus replication in patients with chronic HIV-1 infection.
                Subjects with at least 2 years virus suppression during antiretroviral therapy and a CD4 : CD8 ratio > 1 were randomly assigned to interrupt highly active antiretroviral treatment (HAART) three times (n = 12) or to continue their previous HAART (n = 14).
                In 10/12 interrupter patients a rebound of HIV-1 RNA was detected in all three structured treatment interruptions (STI). Plasma virus doubling time was shorter during the first STI than in the second and third STI, corresponding to an average 13% reduction in viral basic reproductive rate. However, the mean time before plasma viral load rose to > 50 copies/ml was significantly shorter in the second and third STI. The average frequency of HIV-specific CD8 T cells in the interrupter patients at the end of the third STI cycle was significantly higher compared with the baseline and the end of the first STI. A substantial increase in HIV-specific CD8 T cell frequencies was found in four interrupter patients, whereas there were no changes in all 14 non-interrupter individuals. A weak p24-specific T helper response developed in 5/12 interrupter patients compared with no response in non-interruptors, but these responses were transient and disappeared rapidly.
                The increase in the control of viral replication, and positive effects of STI on immune responses in this population should encourage the further development of HIV-specific immune-based therapeutic strategies. Markers of maturation and activation were measured on peripheral CD4+ T cells in chronically HIV-1-infected patients in a randomized, controlled pilot study of structured treatment interruption (STI). Eight subjects underwent 2 cycles of 1 month off and 1 month on highly active antiretroviral therapy (HAART), followed by a final 3-month interruption. During STI, CD4+ T-cell percentage remained relatively stable in 4 of 8 subjects. The remaining 4 STI subjects had significant rapid decline in CD4+ T-cell percentage during STI, followed by return to pre-STI baseline while on HAART. Changes in overall CD4+ T-cell percentage corresponded with fluctuations in the CD45RA+CCR7+ naive and CD45RA-CCR7+ central memory subsets. Subjects with variable CD4+ T-cell percentages tended to have higher pre-HAART plasma HIV-1 RNA set-points and experienced higher levels of plasma HIV-1 RNA rebound during STI. These results suggest that interruptions should be avoided whenever possible in patients on HAART with high plasma HIV-1 RNA set-points. 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. The risks and benefits of structured treatment interruption (STI) in HIV-1-infected subjects are not fully understood. A pilot study was performed to compare STI with continuous highly active antiretroviral therapy (HAART) in chronic HIV-1-infected subjects with HIV-1 plasma RNA levels (VL) <400 copies per ml and CD4(+) T cells >400 per microl. CD4(+) T cells, VL, HIV-1-specific neutralizing antibodies, and IFN-gamma-producing HIV-1-specific CD8(+) and CD4(+) T cells were measured in all subjects. STIs of 1-month duration separated by 1 month of HAART, before a final 3-month STI, resulted in augmented CD8(+) T cell responses in all eight STI subjects (P = 0.003), maintained while on HAART up to 22 weeks after STI, and augmented neutralization titers to autologous HIV-1 isolate in one of eight subjects. However, significant decline of CD4(+) T cell count from pre-STI level, and VL rebound to pre-HAART baseline, occurred during STI (P = 0.001 and 0.34, respectively). CD4(+) T cell counts were regained on return to HAART. Control subjects (n = 4) maintained VL <400 copies per ml and stable CD4(+) T cell counts, and showed no enhancement of antiviral CD8(+) T cell responses. Despite increases in antiviral immunity, no control of VL was observed. Future studies of STI should proceed with caution. The influence of previous structured treatment interruptions (STIs) on the length of time off therapy when highly active antiretroviral treatment (HAART) is discontinued in chronically HIV-infected subjects was assessed. A comparative, retrospective clinical cohort study included patients with plasma viral load (VL) <50 copies/ml and CD4 cell count >500 cells/mm(3) who interrupted HAART. Fifteen patients interrupted HAART after six 2-weeks-off-/4-weeks-on therapy cycles (STI group) and 30 subjects discontinued HAART without previous STIs (NSTI group). The criteria for treatment resumption were development of AIDS-defining clinical events, VL >100,000 copies/ml or CD4 <350 cells/mm(3). Median (IQR) time off therapy was 48 (29-56) weeks in the STI group and 31 (8-77) weeks in the NSTI group (p < 0.15). After 48 weeks, 46% of the patients in the STI group and 40% in the NSTI group remained off HAART (p < 0.74). No patient developed AIDS-defining events and all but one achieved virological control after treatment resumption. The CD4 nadir was 341 (298-464) cells/mm(3) among patients who reinitiated HAART and 560 (364-682) cells/mm(3) in those who remained off therapy by week 48 (p <0.01). Likewise, CD4 count prior to treatment interruption was 902 (806-1040) cells/mm(3) and 1123 (924-1234) cells/mm(3) in subjects resuming and remaining off HAART, respectively (p = 0.03). No relationship between treatment resumption and pre-ART VL or with the time with undetectable VL before enrollment was found. CD4 nadir was a significant predictor for treatment reinitiation in a multivariate analysis. Previous STIs do not influence time off therapy when HAART is definitively discontinued in chronically HIV-infected subjects. CD4 nadir is an important factor in the treatment discontinuation decision. To analyze the dynamics of both HIV-1-specific CD4 and CD8 T-cell responses during structured treatment interruptions (STIs) in chronically HIV-1-infected (CHI) patients and to correlate them with the viral set point achieved.
                Forty-five early-stage CHI patients who were on highly active antiretroviral therapy (HAART) for at least 1 year and underwent STI were included. Plasma viral load (VL), peripheral blood mononuclear cell (PBMC) lymphoproliferative (LPR) response to HIV p24 protein, and HIV-1 epitope-specific interferon-gammarelease from CD8 T cells were measured over a minimum study period of 2 years.
                VL set point during final STI was both significantly lower than, and positively correlated to, baseline VL (P < 0.0001: mean VL reduction 0.77 log10, and r = 0.42, P = 0.004, respectively). CD4 LPRs to p24 increased significantly (P = 0.001) between day 0 of the first STI cycle and 4th STI but decreased thereafter. VL set point during final STI was significantly and negatively correlated with LPRs to p24 at both 2nd STI and 4th STI. Nevertheless, at week 52, 12 weeks after the end of the last STI, LPRs were weak and transient in all patients and were not correlated with VL set point. Moreover, the magnitude and breadth of HIV-1-specific CD8 T-cell responses increased significantly (P < 0.0001) between day 0 and week 52. The largest increases occurred during the final STI. Even though VL reached set point by week 12 of the final STI, HIV-1-specific CD8 T-cell responses did not stabilize but rather increased until the end of the follow-up and did not correlate with plasma VL (r = 0.01, P = 0.88).
                STIs do not lead to control of viral replication in CHI patients, probably due to the fact that boosted CTL responses lack strong and durable helper T-cell responses. To reset the VL set point, new approaches that effectively augment and preserve helper T-cell responses should be investigated. Potent antiretroviral therapy (ART) suppresses HIV-1 viral replication and results in decreased morbidity and mortality. However, prolonged treatment is associated with drug-induced toxicity, emergence of drug-resistant viral strains, and financial constraints. Structured therapeutic interruptions (STIs) have been proposed as a strategy that could boost HIV-specific immunity, through controlled exposure to autologous virus over limited time periods, and subsequently control viral replication in the absence of ART. Here, we analyzed the impact of repeated STIs on virological and immunological parameters in a large prospective STI study. We show that: (i) the plateau virus load (VL) reached after STIs correlated with pretreatment VL, the amount of viral recrudescence during the treatment interruptions, and the off-treatment viral rebound rate; (ii) the magnitude and the breadth of the HIV-specific CD8(+) T lymphocyte response, despite marked interpatient variability, increased overall with STI. However, the quantity and quality of the post-STI response was comparable to the response observed before any therapy; (iii) individuals with strong and broad HIV-specific CD8(+) T lymphocyte responses at baseline retained these characteristics during and after STI; (iv) the increase in HIV-specific CD8(+) T lymphocyte frequencies induced by STI was not correlated with decreased viral set point after STI; and (v) HIV-specific CD4(+) T lymphocyte responses increased with STI, but were subsequently maintained only in patients with low pretreatment and plateau VLs. Overall, these data indicate that STI-induced quantitative boosting of HIV-specific cellular immunity was not associated with substantial change in viral replication and that STI was largely restoring pretherapy CD8(+) T cell responses in patients with established infection. The use of structured treatment interruption (STI) in human immunodeficiency virus (HIV)-infected subjects is currently being studied as an alternative therapeutic strategy for HIV-1. The potential risk for selection of drug-resistant HIV-1 variants during STI is unknown and remains a concern. Therefore, the emergence of drug resistance in sequential plasma samples obtained from 28 subjects with chronic HIV infection was studied. They underwent 4 cycles of 2-week STI, followed by 8-week retreatment with highly active antiretroviral therapy identical to that used before STI, and they had never failed treatment before undergoing STI. At week 40, treatment was stopped for a longer period. Minor populations of drug-resistant variants were detected by quantitative real-time polymerase chain reaction, by use of allele-discriminating oligonucleotides for 2 key resistance mutations: L90M (protease) and M184V (reverse transcriptase). The approximate discriminative power was 0.1%. In 14 of 25 and in 3 of 25 subjects, the M184V and the L90M mutations, respectively, were detected as minor populations, at different times during STI. Overall, these results indicate that, in subjects undergoing multiple STIs, HIV-1 variants carrying drug-resistance mutations can emerge during periods of increased HIV-1 replication.
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.