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Factors Associated with Post-treatment Control of Viral Load in HIV-Infected Patients: A Systematic Review and Meta-analysis

  • Author Footnotes
    † These authors contributed equally to this work
    Chi Zhou
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    † These authors contributed equally to this work
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    Department of Dermatology, The Affiliated Hospital of Qingdao University, Qingdao, China

    Clinical and Research Center for Infectious Disease, Beijing Youan Hospital, Capital Medical University, Beijing, China
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    † These authors contributed equally to this work
    Yaxin Wu
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    Clinical and Research Center for Infectious Disease, Beijing Youan Hospital, Capital Medical University, Beijing, China
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  • Author Footnotes
    † These authors contributed equally to this work
    Yang Zhang
    Footnotes
    † These authors contributed equally to this work
    Affiliations
    Clinical and Research Center for Infectious Disease, Beijing Youan Hospital, Capital Medical University, Beijing, China

    Beijing Key Laboratory for HIV/AIDS Research, Clinical and Research Center for Infectious Diseases, Beijing Youan Hospital, Capital Medical University, Beijing, China
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  • Yingying Wang
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    Clinical and Research Center for Infectious Disease, Beijing Youan Hospital, Capital Medical University, Beijing, China
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  • Hao Wu
    Affiliations
    Clinical and Research Center for Infectious Disease, Beijing Youan Hospital, Capital Medical University, Beijing, China

    Beijing Key Laboratory for HIV/AIDS Research, Clinical and Research Center for Infectious Diseases, Beijing Youan Hospital, Capital Medical University, Beijing, China
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  • Tong Zhang
    Correspondence
    Correspondence author.
    Affiliations
    Clinical and Research Center for Infectious Disease, Beijing Youan Hospital, Capital Medical University, Beijing, China

    Beijing Key Laboratory for HIV/AIDS Research, Clinical and Research Center for Infectious Diseases, Beijing Youan Hospital, Capital Medical University, Beijing, China
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  • Guanzhi Chen
    Correspondence
    Correspondence author.
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    Department of Dermatology, The Affiliated Hospital of Qingdao University, Qingdao, China
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  • Xiaojie Huang
    Correspondence
    Correspondence author.
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    Clinical and Research Center for Infectious Disease, Beijing Youan Hospital, Capital Medical University, Beijing, China
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  • Author Footnotes
    † These authors contributed equally to this work
Open AccessPublished:January 24, 2023DOI:https://doi.org/10.1016/j.ijid.2023.01.025

      Abstract

      Background

      This study aimed to investigate the factors associated with maintenance of viral suppression after antiretroviral therapy (ART) discontinuation.

      Methods

      Databases were searched for studies published between 1 January, 2011, and 1 July, 2022 that correlated the time of virus rebound with treatment interruption (TI). The corresponding data were extracted from these studies. A fixed-effects model was used to calculate pooled estimates.

      Results

      Thirty-one studies were included in this analysis. Results showed that patients who started ART during acute or early infection had longer viral control than those who started ART during chronic infection. It has been reported that some broadly neutralising HIV-1-specific antibodies can significantly prolong viral inhibition. The study also found that approximately 7.2% of patients achieved post-treatment control (PTC) approximately a year after TI.

      Conclusion

      ART initiation in the acute or early phases can delay viral rebound after TI. Cell-associated (CA) HIV RNA and HIV DNA have been difficult to prove as able to predict viral rebound time. Many vaccines and antibodies have also been shown to be effective in prolonging viral control in people without PTC, and more research is needed to develop alternative ART therapies that can effectively inhibit or even eliminate HIV.

      Keywords

      Introduction

      Human immunodeficiency virus (HIV) infection is becoming manageable and chronic owing to the widespread use of antiretroviral therapy (ART). Antiretroviral drugs are highly effective in inhibiting HIV replication and reducing morbidity and mortality [1]. The continuous use of combination antiretroviral drugs can result in sustained viral suppression in people living with HIV (PLWH), and some people can even get viral suppression while on drugs for life [2]. However, a small pool of resting memory CD4+ T cells that harbor transcriptionally inactive, replication-competent HIV-1 proviruses in PLWH are known as reservoirs. Reservoirs are resistant to ART, and ART cannot eradicate the virus or cure HIV infections [3]. Considering the side effects of medication, risk of drug resistance, stigma, and high costs, although researchers have been searching for a cure for HIV, there has been an increasing focus on achieving sustained HIV remission without lifelong dependency on ART, also known as a functional cure [4, 5].
      In most individuals, ART interruption causes the virus to rebound quickly [6]. However, a very small number of patients who have received ART, known as post-treatment controllers (PTCs), can suppress the virus for a long time after the discontinuation of ART [7, 8]. These PTCs are considered potential models for a functional cure. A small percentage of PLWH have not received ART, can spontaneously inhibit viral replication for a long time; thus, plasma HIV RNA can be maintained at a very low level in these PLHIV, who are known as elite controllers (ECs). The presence of ECs suggests that HIV infection can be controlled without medication. The main difference between PTCs and ECs is whether ART has been used. Other aspects, including the frequency of reaching PTC, are higher than those of EC, and the HIV-specific CD8+T cell responses in PTCs are lower than those in ECs, making PTCs and ECs easier to distinguish. The mechanisms of long-term virologic control in PTC and EC are still being explored [9-11].
      Previous studies have found that the time for viral rebound after treatment interruption (TI) varies greatly between individuals, ranging from three weeks [6] to 89 months [8], suggesting that various virological and immunological factors may influence this process [12, 13]. HIV reservoirs are established before peak viraemia (approximately 2-4 weeks after infection), and ART is initiated in the early stages (≤6 months after the estimated date of infection), which could also limit the size of the reservoir [14-17]. In addition, we considered that viral loads, CD4+T cell count, nadir CD4+T cell count before ART, and the CD4+T cell count, and CD4/CD8 ratio before TI may be related to viral suppression after TI. It has also been suggested that factors such as the type of ART, length of time on ART, and duration of suppression of HIV viraemia before ART interruption may be related to viral suppression [18-21]. HIV clade and patient's age may also be relevant. Continued viral replication, reactivation of different viral reservoirs, HIV superinfection, etc., may be the cause of viral rebound in PTCs [9]. Currently, there is no unified definition of PTC. The definition of the viral load threshold of PTC, criteria for restarting ART after TI, and frequency of viral load measurements during analytical treatment interruption vary from study to study, and can have an impact on the determination of PTC [13].
      Researchers are searching for interventions to achieve sustained virological remission without ART. Two main strategies are being implemented: 1) replacing daily ART with intermittent or continuous non-ART intervention, and 2) inducing continuous immune-mediated HIV control without further intervention [22]. The first approach, using broad neutralising antibodies (bNAbs) against HIV, replaces ART with injections of antibodies at fixed intervals. The second approach, a therapeutic vaccine, is ideally designed to induce an HIV-specific immune response after one or more doses that can permanently control the virus. To explore the common characteristics of patients who can maintain long-term virological remission, trial data from TI-related studies were reviewed and assessed for factors that could delay viral rebound. The objectives were to find effective predictors of PTC and to provide the basis for screening patients for studies on TI and the clinical need for long-term ART discontinuation. We describe the current interventions that can positively impact time-to-rebound to summarise the current achievements to date and suggest the possible developmental direction of a functional cure in the future.

      Materials and Methods

      The study was registered with PROSPERO, the International Prospective Register of Systematic Reviews, under the identification number CRD42022251929.

      Search Strategy

      Articles published between 1 January, 2011, and 1 July, 2022 were searched. Specific search strategies are provided in the Supplementary Material (Table S1), but limited to articles published in the English language.

      Data Sources

      The search was conducted using PubMed, EMBASE, Web of Science, and the Cochrane Library for journal articles. Google Scholar was used as a supplement.

      Studies Sections

      The search results were imported into EndNote X9 to screen titles and abstracts. Full-text articles were read and judged qualified or unqualified according to the inclusion criteria. Two authors independently screened all titles, abstracts, and full texts and extracted relevant data, with differences being reconciled by a third reviewer.
      The inclusion criteria for the articles were: 1) focused on adults living with HIV previously treated with ART, 2) clinician or investigator-directed TI, and 3) presented the TI design, pre- and post-interruption data, and time to viral rebound/rate of PTCs. Reviews, comments, case reports, conference abstracts, animal studies, and studies with overlapping samples were excluded. Studies with patients with comorbidities were excluded. Studies that involved therapeutic interventions other than ART before or after TI were not included, but for some two-arm/three-arm clinical studies, blank groups without any intervention were also included. Selected articles meeting the inclusion criteria after reading the full text, were included in the study. Our systematic review and meta-analysis followed the recommendations of the PRISMA statement [23] (Table S2).
      Quality Assessment and Data Extraction
      The quality and risk of bias assessments in randomized controlled trials (RCTs) were conducted using the Cochrane Risk of Bias Assessment Tool, and a modified Newcastle Ottawa scale was used to assess non-randomised and observational studies (Table S3).
      The extracted data included basic study information (title, author's name, and year of publication), number of participants who completed the study, age, sex, the proportion of men who had sex with men, clades of HIV, study design, pre-ART and pre-TI viral load, HIV-DNA, CD4+/CD8+ ratio, CD4+ T-cell nadir and CD4+ T-cell count thresholds, the period of ART initiation, types of antiretroviral drugs, duration of ART, duration of suppressed HIV viraemia, duration of TI, and time to viral rebound and/or rate of PTCs after TI. Acute HIV-1 infection was defined as a lack of anti-HIV antibodies and a positive p24 antigen and/or detectable plasma HIV-1 RNA (approximately ≤ 2-4 weeks after HIV infection). Early infection was defined as ≤6 months after infection, including the stage of acute HIV infection and the stage at which anti-HIV antibodies were detectable. Viral rebound was defined as detectable plasma viraemia, with specific HIV RNA thresholds differing between studies. In human studies, PTC was defined in accordance with the original study in terms of the viral load, which ranged from 50 to 400 copies/mL, and by selecting the proportion of PTCs discontinued for one year or nearly one year in terms of time, with a difference of no more than three months.

      Data Analysis

      The patterns of study characteristics among the study designs are described, and detailed tables providing evidence and summary reports based on factors related to viral rebound are generated. The researchers attempted to describe the correlation between the time to viral rebound and different study factors (including pre-ART and pre-interruption characteristics) and elucidate the association between PTCs and virological and immunological indicators before treatment discontinuation. The first of the two meta-analyses evaluated the factors affecting viral inhibition after TI. In this meta-analysis, the outcomes were the proportion of PLWH who had viral loads that remained undetectable for more than 12 weeks after the interruption of ART. The second regards the factors related to PTC, with outcomes the rates of PTC in PLWH. The included studies were divided into subgroups.
      Meta-analytical methods were applied to studies with available data. For the meta-analysis, fixed-effects models were used to combine the data. Considering the high occurrence frequency of zero events in the first meta-analysis, the generalized linear mixed model method, which has good statistical performance and robustness for sparse data in the study of single group rate, was used for the analysis in R language. The I2 statistic was used to estimate the proportion of heterogeneity. Stratified analyses were conducted to identify the sources of heterogeneity. Funnel plots and Egger's regression asymmetry tests were used to assess publication bias. The number of patients whose time to viral rebound was ≥ 12 weeks and the proportion of PTCs who remained in virologic suppression for nearly a year was calculated. In both cases, the proportion (based on a single arm) was used as the effect estimate (ES), and significance was determined using the Z-test. R language 4.2.1, Stata version 16.0 (Stata Corporation, College Station, TX) and Excel version 2019 (Microsoft) were used for the meta-analysis.

      Results

      Study Selection and Characteristics

      The search identified 11,479 published journal articles, of which 5,239 were duplicates. After excluding duplicates, 6,240 screening records were identified. Since the Strategies for Management of Antiretroviral Therapy trial [24] and reviews have demonstrated increased risk of non-AIDS-defining events, opportunistic infections, and death after CD4 count-guided TIs or the structured treatment interventions (STI) method for TI, and the 2011 guidelines [25] show that STI are currently discouraged for the management of HIV-infected patients, studies published after 2011 were selected for this meta-analysis. After browsing the full texts, 31 articles that met the inclusion criteria were selected (Figure 1). Tables 1 and 2 summarise the characteristics of the included articles.
      Figure 1
      Figure 1PRISMA flow diagram of the literature search.
      Table 1Characteristics of the included studies related to time to virus control after TI (in the studies that included other therapeutic interventions except ART, the control groups without therapeutic interventions were selected for meta-analysis).
      BEFORE ARTDURING ARTBEFORE TI
      First AuthorPublication YearStudy DesignIncluded in meta-analysisinterventionNStages of HIV infection before initiated ARTTime to viral rebound median (weeks)Definition of virus rebound (HIV-1 RNA, copies per mL)Age (median)Sex (male%)Transmission group (MSM%)Nadir CD4 count, cells per Μl (median)HIV-1 RNA, log10 copies per mL (median)CD4 count, cells per μL (median)Duration of ART (years,median)Duration of suppressed HIV viremia (years,median)CD4 count, cells per μL (median)CD4/CD8 ratio (median)
      Calin2016Interventional10chronic440041.57070494.53.95NA5.34.8510462.1
      Lodi2012Observational259early6.85034NA67.2NA4.55561.3NANANA
      Castagna2019Interventional9chronic35050.790NA346NANANA11.747481.19
      Le2019Observational1076NA2undetectable280NANANANA0.42NANANA
      Gianella2015Observational16acute/early3.650–400NA10093.754064.75524.52.041.75743.51.1
      Gianella2016Observational14chronic5.950–40041100100293NANA4NANANA
      Colby2018Interventional8acute3.6202987.575NA4.25412.52.75NA5771.15
      Pannus2020Interventional16chronic45043.593.7575440.5NANA43.4758NA
      Giron2021Interventional24NA3.9NA4591.67NANANANANNA678.5NA
      Maenza2015observational22acute/early8.6850035100NAN5.085762.37NANANA
      Bartsch2021Observational23chronic4.35037.2947.83NANANANA1.46NA483NA
      Cirio´n2013Observational14acute400NA71.43NANA4.955023NA926.5NA
      Sneller2020Observational22chronic1.9405190.9NANANANANA7.7767NA
      Pasternak2020RCT51acute/early550NANANANANANA1.2NANANA
      Li2016Observational31acute32003697NANANANANANA852NA
      45early32003794NANANANANANA827NA
      137chronic32004288NANANANANANA800NA
      Colby2020RCTAd26+MVA17acute32024100NANA63291.92NA637NA
      Placebo*9acute2.12025100NANA6.42271.92NA531NA
      Mothe2015RCTMVA-B10NA230NANANANANANANANANANA
      Placebo*6NA130NANANANANANANANANANA
      MVA-B, Modified vaccinia Ankara-based HIV-1 vaccine.
      MVA-B + disulfiram
      8NA130NANANANANANANANANANA
      Angel2011RCT
      ALVAC 1452, a canarypox-based vaccine; Remune, a whole, killed HIV immunogen.
      ALVAC with Remune
      16chronic3.550NANANA347NANA3.61NA771NA
      ALVAC with Remune placebo18chronic3.35041.572.22NA3264NA5.15NA658NA
      Placebo*14chronic1.950NANANA3684.2NA5.18NA848NA
      Sneller2017RCT
      HIV-MAG, a HIV-multiantigen DNA vaccine with encoding multiple HIV proteins. f
      HIV-MAG
      14acute/early440040100NANANANANANANANA
      Placebo*16acute/early440042100NANANANANANANANA
      Jong2019RCT
      HTI-TriMix, HIVACAT T cell Immunogen-TriMix vaccine.
      HTI-TriMix
      15NA250NANANANANANANANANANA
      TriMix9NA2504610089NA4.784406.93NA815NA
      Water for Injection*8NA2504010088NA4.934026.73NA837NA
      Crowell2019RCTVRC0113acute4.15032100100NA5.83883.1NA7691.1
      Placebo*5acute25025100100NA62862.7NA5620.9
      Kroon2020RCT
      VHM, vorinostat/hydroxychloroquine/maraviroc. *: Groups included in the Meta-analysis. ART, antiretroviral therapy; TI, treatment interruption; NA, not avaliable; MSM, men who have sex with men; RCT, randomized controlled trial.
      VHM
      9acute3202890NANA6.13974.3NANANA
      ART only*5acute3.1202680NA2745.65323NANANA
      Sneller2022RCT3BNC117 and 10-10747acute/early33.420040100NANANANA3.7NA799NA
      Placebo*7acute/early3.420034100NANANANA2.9NA612NA
      Leal2021RCTVaccine8NA2.72049100100NANANANANA790NA
      Placebo*7NA2.7204710071.4NANANANANA739NA
      a MVA-B, Modified vaccinia Ankara-based HIV-1 vaccine.
      b ALVAC 1452, a canarypox-based vaccine; Remune, a whole, killed HIV immunogen.
      c HIV-MAG, a HIV-multiantigen DNA vaccine with encoding multiple HIV proteins. f
      d HTI-TriMix, HIVACAT T cell Immunogen-TriMix vaccine.
      e VHM, vorinostat/hydroxychloroquine/maraviroc.*: Groups included in the Meta-analysis.ART, antiretroviral therapy; TI, treatment interruption; NA, not avaliable; MSM, men who have sex with men; RCT, randomized controlled trial.
      Table 2Characteristics of studies related to the incidence of PTC included in the meta-analysis.
      BEFORE ARTDURING ARTBEFORE TIBEFORE VR
      First AuthorTitle of Research StudyPublication YearStudy DesignNStages of HIV infection before initiated ARTPTC proportion at 1 year after TIDefinition of PTC viral load (HIV-1 RNA, copies per mL)Age (median)Sex (male%)Transmission group (MSM%)Nadir CD4 count, cells per mL (median)HIV-1 RNA, log10 copies per mL (median)CD4 count, cells per μL (median)Duration of ART (years,median)HIV-1 RNA, log10 copies per mL (median)CD4 count, cells per μL (median)CD4/CD8 ratio (median)CD4 count, cells per μL (median)
      Che´retOptiprim2015RCT63PHI3.2%400NANANANANANANANANANANA
      StöhrSpartac2013RCT86PHI4.0%400336056NA4.25430.23NANANANA
      7914.0%400347367NA4.76000.92NANANANA
      Cirio´nVISCONTI2013ObservationalNAPHI15.3%50NANANANANANANANANANANA
      GianellaSwiss2011Interventional32PHI9.0%503987.565.6NA4.84981.5NANANANA
      GrijsenPrimo-SHM2012RCT40(24W of ART)PHI5.0%10040(mean)9078NA5.1(mean)584(mean)0.46<1.7NANANA
      39(60W of ART)10039(mean)9787NA4.9(mean)483(mean)1.15<1.7NANANA
      GoujardANRS CO6 PRIMO2012Observational164PHI11.0%503364NANA4.85821.675<1.79721.4NA
      LodiCASCADE2012Observational259PHI8.2%5042NA67%NA4.55561.3<1.7NANA762
      PerkinsNHS2017Observational95chronic infection4.2%400NA89.5NA462(PTCs) 320(RV)NANANANANANANA
      AssoumouANRS 116 SALTO2015Interventional95chronic infection7.4%400406349.50%3824,34545.3y<2.6813NANA
      CalinULTRASTOP2016Interventional10chronic infection10.0%40041.57704954NA5.3Y<110462.1744
      ART, antiretroviral therapy; TI, treatment interruption; PTCs, post treatment controls; NA, not avaliable; MSM, men who have sex with men; PHI, primary HIV infection; RCT, randomized controlled trial; VR, viral rebound.
      The median time to viral rebound without intervention after TI was three weeks, ranging from 1 [26] to 8.68 [27] weeks. Nearly one year after TI, the median proportion of PTCs was 8.1%, ranging from 3.2% [28] to 15.3% [8]. Two studies [29, 30] included duplicate cohorts but analysed different aspects, and these studies could not be analysed at the same time. Only studies that did not use other interventions except ART were included in the meta-analysis. Although studies that included other interventions were included, only the group without intervention was selected for meta-analysis. The main features of the included studies related to the time to viral control after TI are shown in Table 1, whereas the main features of the included studies related to the incidence of PTC are listed in Table 2. Table 3 describes the findings for each cell-associated (CA) HIV RNA and HIV DNA-related study.
      Table 3Summary of results for published studies of the relationship between CA HIV-1 RNA, HIV DNA and PTC in HIV-infected adults.
      StudyResults
      Li JZ 2016Factors significantly associated with earlier timing of viral rebound included CA-RNA [OR 2.3, P < 0.01]. No significant association was seen between CA-DNA levels and timing of viral rebound, regardless of the timing of ART initiation.
      Pannus P 2020Although HIV-1 reservoir markers such as total-DNA and cell-associated HIV-1 unspliced RNA have been correlated with PTC status, we show here that their predictive power is too weak to prospectively identify PTCs from the general patient population on ART.
      Pasternak AO 2020We demonstrate substantial predictive value of CA RNA for (a) the virological and immunological response to early ART, (b) the magnitude and time to viral rebound after discontinuation of early ART, and (c) disease progression in the absence of treatment. No other marker, including HIV-1 DNA or the therapy regimen, was shown to be predictive for time to viral rebound in our study
      Sneller MC 2020Frequencies at baseline of CD4+ T cells carrying total HIV DNA but not cell-associated HIV RNA nor replication-competent virus correlated with time to viral rebound >200 copies/ml.
      Bartsch YC 2021Integrated CA-DNA levels were below the detection limit for all patients in the delayed rebounders but not the early rebounder group (adjusted P = 0.18), and CA-RNA was higher in early rebounders (adjusted P = 0.0008)
      Sáez-Cirión A 2013The cell subsets of all the PTCs analyzed ex vivo carried very low levels of HIV DNA.
      Calin R 2016The strict inclusion criterion of low HIV-DNA levels seemed to have no effect either on the time to rebound, or on the magnitude of plasma viral load relapse.
      Colby DJ 2018There was no association between pre-ATI total HIV DNA and time to viral load rebound.
      Castagna A 2019The total amount of HIV-DNA is significantly affected by prolonged suppressive therapy, it does not itself represent a predictor of delayed viral rebound during ATI.
      Assoumou L 2015Only HIV-DNA level at treatment interruption was independently predictive of time to loss of viral control.
      ART, antiretroviral therapy; PTCs, post treatment controls; CA HIV-1 RNA, cell-associated HIV-1 RNA; ATI, analytical treatment interruption
      Meta-analysis of the proportion of PTCs
      Among the 18 available studies [6, 26, 29, 31-45], the pooled proportion for which the time to viral rebound was more than 12 weeks was 5.1% (95% CI, 3.5%–7.6%), with a total variance of I2 = 0% among all included studies in the fixed effects meta-analysis (Figure 2).
      Figure 2
      Figure 2The proportion of patients who maintained viral suppression for 12 weeks after TI estimates.
      Fixed-effects meta-analysis results for the proportion of patients with a viral suppression duration of up to 12 weeks after TI. Studies were identified by the name of the first author and years of publication. ES=effect estimates, 95%CI=95% confidence interval. Weights (%) were obtained from fixed-effect analysis.
      The funnel plot (Figure S1) and Egger's test (P = 0.51 > 0.05) showed no significant publication bias.
      In the meta-analysis, the impact of 12 factors associated with the proportion of the viral load that remained undetectable after 12 weeks of TI was assessed (Table 4).
      Table 4Association between factors and rates of viral suppression lasting more than 12 weeks after TI.
      Number of studiesproportion

      (95% CI)
      z valuep value
      Stages of HIV infection before ART14
      In one study, patients were stratified by the time ART was started, and in this analysis, they were analyzed as two studies.
      2.660.01
      acute/early phase90.087(0.055,0.135)
      chronic phase60.027(0.020,0.058)
      Median viral loads before ART70.210.83
      <105 copies per mL40.071(0.023,0.199)
      ≥105 copies per mL30.053(0.007,0.294)
      Median CD4+T cell count before ART60.700.49
      <500 cells/μL40.033(0.005,0.202)
      ≥500 cells/μL20.095(0.024,0.311)
      Median nadir CD4+T cell count before ART60.420.68
      <350 cells/µL20.026(0.004,0.165)
      ≥350 cells/µL40.060(0.010,0.285)
      Median length of time on ART111.110.27
      < 3 years50.079(0.026,0.218)
      ≥3 years60.017(0.002,0.109)
      The percentage of people who use NNRTI0.220.82
      <10%20.000(0.000,1.000)
      ≥10%40.057(0.034,0.092)
      The percentage of people who use INSTI0.380.70
      <10%30.043(0.006,0.252)
      ≥10%40.017(0.002,0.109)
      Median length of time on suppressed HIV viremia50.270.78
      <5 years30.071(0.023,0.199)
      ≥5 years20.000(0.000,1.000)
      Median CD4+T cell count before TI141.210.23
      <800 cells/μL100.033(0.013,0.085)
      ≥800 cells/μL40.060(0.037,0.096)
      Median rate of CD4/CD8 before TI50.500.62
      <110.000(0.000,0.522)
      ≥140.070(0.023,0.195)
      Median ages140.430.67
      <4050.029(0.004,0.181)
      ≥4090.049(0.031,0.078)
      Clade
      Clade was selected for the subtype of HIV that infected more than 70% of the patients in the study. ART, antiretroviral therapy; TI, treatment interruption; NNRTI, non-nucleoside reverse transcriptase inhibitor; INSTI, Integrase strand transfer inhibitor; CI, confidence interval.
      0.140.89
      CRF01_AE40.037(0.005,0.221)
      B20.000(0.000,1.000)
      a In one study, patients were stratified by the time ART was started, and in this analysis, they were analyzed as two studies.
      b Clade was selected for the subtype of HIV that infected more than 70% of the patients in the study.ART, antiretroviral therapy; TI, treatment interruption; NNRTI, non-nucleoside reverse transcriptase inhibitor; INSTI, Integrase strand transfer inhibitor; CI, confidence interval.
      In the subgroup analysis of studies at different stages of ART initiation, patients were divided into treatment started in the acute/early phase and treatment started in the chronic phase (Figure 3). Fourteen studies provided information on the infection period of individuals at ART initiation [6, 31-37, 39]. Individuals who started ART during the acute or early stages of HIV infection (8.7%; 95% CI, 5.5–13.5%) were found to have significantly higher rates of maintaining viral suppression for more than 12 weeks after TI than those who started ART during the chronic stage of HIV infection (2.7%; 95% CI, 1.2%– 5.8%) (Figure 3). The Z-test was used to compare the proportions of the combined estimates, resulting in P=0.01, a significant difference.
      Figure 3
      Figure 3Efficacy of initiating ART in different phases (acute/early phase vs. chronic phase) on the rate of viral suppression lasting more than 12 weeks after TI.
      Forest plots of the proportion of patients with a viral suppression duration of up to 12 weeks after TI in studies with ART initiation in the acute or early phase, comparing studies with ART initiation in the chronic phase. Studies were identified by the name of the first author and years of publication. ES=effect estimates, 95%CI=95% confidence interval. Weights (%) were obtained from fixed-effect analysis.
      In this study, no association was found between the pre-ART viral load, CD4+ cell count, nadir CD4+T cell count, duration of ART, duration of viral suppression before ART, utilisation rate of NNRTI and INSTI, and time to viral rebound after ART interruption (Table 4).
      Fourteen studies reported CD4 count before TI [6, 31-33, 35-38, 40-45]. In studies with a median CD4 count of 800 or more before TI, the proportion of patients with a viral suppression duration of up to 12 weeks after TI was 6.0% (95% CI, 3.7%–9.6%). In studies with a median CD4 count of less than 800, 3.3% (95% CI, 1.3%–8.5%) (Figure 4). The Z-test revealed no significant difference between the groups (P= 0.23). No significant association was found between CD4/CD8 ratio and viral suppression (Table 4).
      Figure 4
      Figure 4Efficacy of different levels of median CD4+T cell count (<800 cells/μL vs. ≥800 cells/μL) before TI on the rate of viral suppression lasting more than 12 weeks after TI.
      Forest plots of the proportion of patients with a viral suppression duration of up to 12 weeks after TI in studies with a median CD4+T cell count of 800 or more before TI compared to studies with a median CD4+T cell count of less than 800. Studies were identified by the name of the first author and years of publication. ES=effect estimates, 95%CI=95% confidence interval. Weights (%) were obtained from fixed-effect analysis.
      No correlation was found between age and viral suppression among the 13 studies that reported age.
      Of the ten studies which described PTC ratios [8, 18, 28, 30, 33, 46-50], the percentage of PTCs was approximately 7.2% (95% CI, 5.6%–8.7%), with a total variance of I2 = 35.8% in individuals who had completed a TI study in fixed-effects meta-analysis (Figure 5).
      Figure 5
      Figure 5The proportion of PTCs estimates in HIV-1 infected individuals.
      Fixed-effects meta-analysis results for the percentage of PTCs. Studies were identified by the name of the first author and years of publication. ES=effect estimates, 95%CI=95% confidence interval. Weights (%) were obtained from fixed-effect analysis.
      No publication bias was observed in funnel plots. Egger's test detected no statistical significance for publication bias (P = 0.371>0.05) (Figure S2).
      In the meta-analysis, the impact of seven factors that might be associated with PTC rates was assessed (Table 5), and none showed a significant correlation with the proportion of PTC.
      Table 5Association between factors and PTCs rates.
      Number of studiesproportion

      (95% CI)
      z valuep value
      Stages of HIV infection before ART101.190.23
      PHI70.077(0.059,0.095)
      chronic phase30.055(0.024,0.087)
      Median viral loads before ART60.050.96
      <4.5 log10 copies/mL30.080(0.052,0.108)
      ≥4.5 log10 copies/mL30.081(0.049,0.113)
      Median CD4+T cell count before ART50.380.71
      <500 cells/μL20.078(0.031,0.124)
      ≥500 cells/μL30.088(0.065,0.111)
      Median nadir CD4+T cell count before ART30.460.65
      <400 cells/µL20.054(0.022,0.086)
      ≥400 cells/µL10.010(-0.086,0.286)
      Median length of time on ART90.710.48
      < 2 years50.081(0.061,0.101)
      ≥2 years40.068(0.038,0.098)
      Median ages70.050.96
      <4040.081(0.055,0.106)
      ≥4030.080(0.052,0.108)
      Sex(male%)71.300.19
      <7030.093(0.062,0.164)
      ≥7040.055(0.029,0.081)
      ART, antiretroviral therapy; TI, treatment interruption; CI, confidence interval.

      Discussion

      To the best of our knowledge, this is the first systematic review and meta-analysis of the duration of viral suppression after ART interruption and the proportion of patients with PTC. Available data from 31 studies were reviewed, and the factors related to the duration of viral suppression in HIV-1 infected patients and the proportion of those with PTC were evaluated. Twelve factors related to the duration of viral suppression and seven factors related to the proportion of PTC were identified. The percentage of PLWH with viral suppression for ≥ 12 weeks after ART discontinuation was approximately 5.1%, and the proportion of PTC in patients with interrupted ART was 7.2%. Initiating ART in the acute or early stages of HIV infection is more beneficial for viral suppression after TI than initiating ART in the chronic stages.
      This systematic review further confirmed the association between the stages of HIV infection before ART and PTC. PTCs are most common among patients who started ART in the acute/early phase of HIV infection [8, 21, 34, 47] or during early infancy [51, 52]. Initiating ART as early as possible may significantly limit the number of persistently infected cells and reduce reservoir size [53]. However, Colby et al. documented that Fiebig I-initiated ART did not delay viral load rebound in eight participants [35]. This might be because treatment if too early, blocks the production of effective HIV-specific T-cell memory [54].
      We aimed to identify additional viral markers to assess disease progression and predict the time for the virus to rebound after TI, helping to determine when patients can safely discontinue treatment. There is consensus that the persistence of the viral reservoir is the main reason why HIV-1 infection is difficult to cure [55]. PTC duration has been shown to directly reflect the size of the viral reservoir [56]. Cell associated (CA) HIV-1 RNA and total HIV DNA can still be detected in PLWH, with plasma HIV RNA suppressed to below the limit of quantification of commercial assays [57]. Total HIV-1 DNA can determine the size of the viral reservoir, whereas CA HIV-1 RNA can determine its transcriptional activity of the viral reservoir.
      Five studies discussed the relationship between CA HIV-1 RNA and viral rebound. Three studies reported that high CA RNA levels were significantly associated with shorter viral rebound times [6, 29, 58]. One study found that baseline levels of CA HIV RNA were not associated with time to viral rebound [41]; another found that CA RNA was associated with PTC status as a reservoir marker for HIV-1, however, the predictive power was too weak to prospectively identify PTC [40]. Ten studies reported a correlation between HIV DNA levels and viral suppression. Two of these supported the association between HIV DNA and time to viral rebound [41, 50]. One study found that cell subsets in PTCs carried very low levels of HIV DNA in vitro [8]. One study found that patients with delayed time to viral rebound had CA-DNA levels below the detection limit [58]. However, six studies reported the total amount of HIV DNA did not predict delayed viral rebound during TI [6, 29, 33, 35, 36, 40]. In the current studies, we cannot confirm whether CA HIV RNA and HIV DNA can be reliable predictors of viral rebound. Viral rebound is a complex process, and existing single factors cannot accurately predict the time or probability of viral rebound after TI. It may be necessary to combine multiple viral and host biomarkers and select personalized medical approaches as predictors of viral rebound [59].
      Some types of vaccines have been found to extend the duration of viral control after stopping ART compared to controls [26, 31, 38, 45]. The efficacy of therapeutic vaccines in prolonging viral suppression is also relatively limited compared with that of HIV-specific antibodies [60-64]. The combined application of antibodies has a more significant effect on the duration of viral suppression than a single application [63].
      Although many therapeutic vaccines have improved the response of HIV-specific T-cells, no therapeutic vaccine candidate has been successful in achieving durable suppression of HIV replication [34, 65, 66]. Some vaccines have shown a delay in the time to viral rebound, but no exact link has been found between the delay and immune response to vaccination [26, 38].
      Compared to ART, HIV-1-specific bNAbs may have the potential therapeutic advantage of promoting HIV remission, since bNAbs can bind to the virus and promote the elimination of infected cells [67]. They may also enhance host humoral [68] and cellular [69] immune responses to HIV. Monotherapy 3BNC117 has shown a stronger ability to delay the time to viral rebound by eight weeks compared to placebo controls [61]. Combined administration of 3BNC117 and 10-1074 showed a more robust effect, extending the duration of viral suppression by approximately 20 weeks, with no emergence of observed new resistance [45, 63]. Further 13 of 17 individuals who received seven doses of 3BNC117 and 10-1074 maintained viral suppression for at least 20 weeks after ART [70]. suggesting that a combination of two or more potent bNAbs may maximise the therapeutic effect and reduce the risk of viral escape.
      Our study synthesises the literature on previous treatment discontinuation, provides a comprehensive analysis of the factors that influence viral suppression, and explores interventions that can extend the duration of viral control. The project was limited by the small sample size of the included studies. Given the significant increase in viral load in most PLWH who discontinue ART, and the limitations of research ethics, very few individuals discontinue stable ART. Due to the small sample sizes, it was difficult to draw definitive conclusions regarding immunological and virological indicators and viral suppression. The identification of PTCs is difficult. In clinical studies, it is difficult for both patients and physicians to continue to interrupt ART, and some PTCs restarted ART before it was discovered. In most clinical studies, ART interruption is often accompanied by other interventions, which also interferes with the identification of PTCs. Further studies with larger sample sizes are needed to validate the predictors of HIV rebound after ART interruption. In the present study, the two outcomes differed significantly between the two viral control calculations after TI. This may be largely due to some patients with PTC experiencing early viral rebound before regaining viral control, while some with PTC show sustained viral suppression [7]. In the meta-analysis, viral suppression was defined as the arrival of HIV RNA in an undetectable state, which meant that PTCs with a large and rapid viral rebound before viral suppression were excluded. Different PTC definitions also affect the sensitivity and specificity of PTC identification [13]. PTC mechanism and related factors have attracted increasing attention as a source of inspiration for achieving a functional cure. In our review, because the existing studies on PTCs were still limited, we were unable to identify the factors that significantly increase the rate of PTC. Simultaneously, our work also provides clues regarding the factors which can predict PTCs and inspire other treatments that induce the formation of PTCs.

      Conclusion

      In summary, this study provides further evidence that initiating ART in the acute or early stage can positively impact time-to-rebound after TI compared to initiating ART in the chronic stage. At the same time, this study also explored whether CA HIV RNA and HIV DNA could be used as predictors of viral rebound. Owing to the large differences between the studies, a meta-analysis could not be conducted. We found no consistent support for either, especially HIV DNA, in predicting viral rebound. We consider that one of the existing factors is difficult to explain the complex viral rebound mechanism. Other non-ART interventions, especially HIV-specific bNAbs used in combination, have shown strong effectiveness in delaying viral rebound after ART interruption. These findings provide clues to achieving long-term viral control without ART.

      Ethical Approval

      This study did not require ethical approval.

      Author Contributions

      XH, GC and TZ designed this study. CZ and YW performed literature search and screening. CZ collected and, analysed the data, drafted the manuscript, and revised it. YW, YZ, TZ, HW, XH, GC and, TZ made the major revisions to the manuscript. All the authors have read and approved the final version of the manuscript.

      Funding

      This work was supported by the National Natural Science Foundation of China (No. 81701984), Fund for Capital Health Development Research (2022-2-2185;2022-1G-3011), Beijing Talent Project in the New Millennium (2020A35), National Science and Technology Major Project of China during the 13th Five-year Plan Period (Grant No. 2017ZX10201101), and the Natural Science Foundation of Capital Medical University (PYZ21127).

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      Declaration of interests

      The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

      Appendix. Supplementary materials