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REVIEW

CURRENT OPINION Advancing the HIV cure agenda: the next 5 years

John Thornhill a,b,c, Sarah Fidlera,b,c,, and John Fraterb,d,e,f,

Purpose of review To explore how ethical considerations, improved diagnostics and data from clinical trials might see the lowering of some of the barriers blocking a cure for HIV infection over the next 5 years. Recent findings Despite the recent well publicized but eventually disappointing case reports, there remains only one successful HIV cure, the ‘Berlin patient’. We will review the data suggesting that more potent agents might achieve in-vivo viral activation and explore the tantalizing phenomenon of ‘posttreatment control’ following treatment in primary HIV infection. We will also explore how new assays and novel interventions might move the field forward. Summary There is a need for new agents that can be safely tested to impact the viral reservoir, a more meaningful understanding of how to assay patient samples, and research into mechanisms behind how the reservoir is established and impacted by therapy. With HIVþve individuals responding so well to antiretroviral therapy, new trials must be tested hand-in-hand with guidance from patient representatives, especially with respect to determining the acceptable risk. The road to a cure is going to be difficult, but it is vital that inevitable disappointments do not detract from the final goal, which remains worth striving for. Keywords cure, eradication, HIV, latency, reservoir

INTRODUCTION the reservoir incorporates numerous assays and The last 5 years has seen increased interest, invest- read-outs – a consensus will be needed. Once ment and engagement in a cure for HIV infection measured, we need to decide whether the drugs becoming a reality [1]. However, despite significant we have to hand, like the histone deacetylase inhibi- scientific and clinical advances, a number of key tors (HDACis), show genuine promise or are just questions remain unanswered and new hurdles have useful as proof of concept for the currently undis- arisen. This review will consider the long-term issues covered agents that may follow. Will monotherapy that may be important for the field to move forward. be adequate or will a second intervention be The prognosis for people living with HIV on required, for example, in the form of immunother- suppressive antiretroviral therapy (ART) is now apy, as in the ‘Kick and Kill’ [4] approach? And, excellent [2]. Accordingly, for those in the field of lastly, what other approaches might enter the arena HIV cure to test unproven and potentially toxic over the next 5 years, and how might technologies interventions [3] or stop successful therapy (especi- ally in the context of the effectiveness of ART to aDivision of Medicine, Wright Fleming Institute, Imperial College, London, prevent onward viral transmission), there needs to bCollaborative HIV Eradication of Reservoirs: UK BRC (CHERUB), be caution. We will evaluate the ethical concerns cImperial National Institute of Health Research Biomedical Research d that need to be considered when researching inter- Centre, London, Nuffield Department of Clinical Medicine, Peter Med- awar Building for Pathogen Research, eInstitute for Emerging Infections, ventions aimed at HIV cure in otherwise healthy The Oxford Martin School and fOxford National Institute of Health people living with HIV on ART. Research Biomedical Research Centre, Oxford, UK A better understanding of the biology and Correspondence to John Frater, Nuffield Department of Clinical Medi- pathogenesis of HIV will assist the design of inter- cine, Peter Medawar Building for Pathogen Research, Oxford, OX1 3SY, ventions aimed at HIV cure. For example, the obser- UK. E-mail: [email protected] vation of posttreatment control (PTC) in which Sarah Fidler and John Frater contributed equally to the writing of this some patients stopping ART show no sign of virae- article. mic relapse needs to be further clarified, including Curr Opin Infect Dis 2015, 28:000–000 the mechanisms and predictive markers. Measuring DOI:10.1097/QCO.0000000000000123

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HIV infections and AIDS

HIV Association and the Collaborative HIV Eradica- KEY POINTS tion of Reservoirs: UK BRC (CHERUB) collaboration As new interventions aimed at curing HIV move into [12] are excellent examples of this, with over 800 clinical trials, it is vital that research is planned and respondents and the results to be presented in late conducted in conjunction with the patient groups. 2014. Posttreatment control remains an exciting area of cure research, although much more data are needed. Is cure research a peccadillo of wealthier An algorithm of biomarkers to help identify individuals nations or can it have global impact? who could stop therapy to test for cure or virological A scalable, affordable solution for all people living remission is an important target. with HIV must be the goal of any cure strategy, A cure for HIV is likely to comprise a cocktail of particularly in resource-limited regions where the interventions and may involve significant toxicity. burden of HIV disease is greatest. In view of region- specific priorities, any diversion of funding from HIV prevention, vaccine development or ART roll- out must also be balanced appropriately. As – at least and knowledge from other fields be applied to cur- initially – most cure-related research is unlikely to ing HIV? Underpinning all of these issues is a need impact the vast majority of individuals living with for the field to agree on the definitions of the con- HIV, for example, in the sub-Saharan Africa, it is cepts of ‘latency’, the ‘reservoir’ and even ‘cure’. For vital that key priorities are not overlooked. How- example, latency might be considered as a state of ever, this should not replace the need for proof-of- transcriptional silence with no (or rare) viral trans- concept research, much of which will be conducted cripts and no virion production. The extent to where resources are available, and which might then which a latent cell can be activated to produce a be scaled up into more comprehensive studies. replication-competent varies, and ongoing basic research is still needed to understand these processes and the reversibility of latency. Is it safe or ethical to stop antiretroviral therapy? The only true test of HIV cure is to stop therapy and ETHICAL CONSIDERATIONS assay for the return of viraemia. However, the safety In light of the excellent prognosis for HIVþve indi- of this remains contentious. Not only might the viduals on ART, potential ethical implications need return of viral replication be pathogenic and risk to be considered when proposing any new trials onward transmission, but also it remains unclear as or interventions. to the extent to which rebound viraemia after treat- ment interruption might replenish the reservoir to such an extent that the participant may not be Investigating a healthy population eligible for further interventions for a prolonged Research into curing HIV infection engenders a period. One of the difficulties is the lack of predic- number of important ethical considerations [5,6]. tive assays that could identify individuals prior to Life expectancy for people living with HIV and viral rebound [13], which could also potentially receiving ART approaches that of the general popu- increase the risk of onward viral transmission. The lation [2,7]. This is despite potential lifelong ART- only safe option therefore for individuals enrolling related toxicities and the increased inflammation into cure approach trials with treatment interrup- and immune activation observed for individuals on tion is to include very frequent testing. suppressive therapy [8–10]. With this in mind, any How frequently viral load needs to be checked and clinical trials of potentially toxic interventions for how long after treatment interruption is assessing HIV cure must have strict safety and unknown, although it is clear that when viraemia acceptability safeguards in place. Furthermore, full returns it can do so abruptly and to high levels [13]. and transparent engagement with community and With these uncertainties in mind, significant coun- industry partners as well as policy makers in the selling of these risks and monitoring for rebound design of such trials will be paramount [11]. For will be needed in any stopping protocol. example, garnering opinion from those living with The data are mixed. In the SMART study, treat- HIV will help set the boundaries for what interven- ment interruption caused a significant increase in tions and trials might be considered acceptable – the risk of all-cause mortality amongst those in the questionnaires such as that run across the UK in discontinuation arm compared with controls who conjunction with Public Health England, the British remained on suppressive therapy [14]. The mean

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Advancing the HIV cure agenda Thornhill et al.

length of treatment interruption in SMART was insights they may provide for a scalable approach to 16.8 months, as restarting ART was guided primarily cure, particularly in the setting of changing WHO by CD4 T-cell count, rather than viral load as it ART initiation guidelines [20,21]. would be for a cure-based intervention. Although After treatment interruption, it is expected that SMART is widely cited as the counter-argument to most patients will experience rebound viraemia stopping ART, trials of treatment interruption in soon (within 12 weeks) off ART; however, in the primary infection have not revealed the same degree SPARTAC trial, there was evidence for a correlation of risk. For example, in Short-Course Antiretroviral between time on ART and the duration of virological Therapy in Primary HIV Infection (SPARTAC) [15], ‘remission’ following treatment interruption [22]. no significant clinical events were reported in On a note of caution, new data from Rhesus relation to stopping ART, including no impact on macaques have demonstrated rapid seeding of the the cardiovascular events. The ACTG 371 trial of reservoir during the ‘eclipse’ phase, prior to the treatment interruption in acute HIV infection had development of viraemia [23&]. In light of this, more frequent monitoring than SMART and found ART initiated extremely early and for extended no evidence for harm [16]. Treatment interruption durations may not be successful as a sole interven- at higher CD4 count thresholds than those used in tion, although PTC data indicates that animal SMART may explain why a lower incidence of AIDS- models may not always reflect human pathogenesis. defining opportunistic infections or deaths (based on observed incidence in SMART) was observed in the STACCATO trial [17]. Given the importance of Biomarkers to predict remission prompt detection of rebound viraemia in any cure As a part of understanding PTC, biomarkers to trial, the use of novel technology such as point-of- identify who to stop, and more importantly when care tests (POCTs) for HIV viral load may facilitate it is safe to stop, are needed. For example, in the easier timely detection of viral rebound in the treat- SPARTAC trial, HIV DNA at the time of treatment ment interruption protocols [18]. interruption was predictive of time to rebound [24&]. Other markers of viral latency (e.g., intracellular viral RNA transcript production) or immune func- FUTURE DIRECTIONS IN CLINICAL tion [e.g., activation markers like human leucocyte SCIENCE antigen DR and CD38 or exhaustion markers like As our understanding of the nature of the HIV programmed death receptor 1 (PD-1) or T cell immu- reservoir and latency improves, we will need to noglobulin mucin-3] might provide extra predictive apply the principles learnt to clinical studies. information. Simple measures like the CD4/CD8 ratio are easily measured from the standard clinical assays and may equally have a predictive role in Posttreatment control identifying possible posttreatment controllers [25]. PTC – reported in a small cohort [called Viro- The large number of biomarkers of interest will Immunological Sustained CONtrol after Treatment require a coordinated approach to ensure assays Interruption (‘VISCONTI’)] of patients stopping ART can be standardized and data can be compared after treatment since primary HIV infection (PHI) – across different PHI cohorts. provides evidence that some degree of functional cure or remission might be possible following early initiation of ART alone [19&]. Initially, 14 individuals Measuring the reservoir were described (but subsequently more have been There are now a number of laboratory assays which identified) who had remained aviraemic off therapy have been designed to quantify the reservoir, but as for a median of 89 months, having received a yet, their relevance to directing clinical decisions median of 36 months of ART. Further analyses of remains unclear and none have been validated for a larger ANRS cohort, comprising individuals treated use with clinical practice [26&&]. For example, output in PHI, indicated that viral remission was evident in from molecular assays of HIV DNA quantification approximately 15% of patients 2 years after stopping and viral culture approaches may vary by 1000-fold ART [19&]. No real mechanism has been described, [27]. Deciding which assays are most applicable apart from speculation on the impact of early ART depends on an agreed definition of what the target on the formation of the reservoir, based on low HIV of the assay – the HIV ‘reservoir’ (a term that causes DNA levels at and after treatment interruption. increasing levels of discomfort amongst some viro- Although the Berlin patient has received most atten- logists) – actually is. A reasonable definition – as tion, his case remains a one-off and these VISCONTI proposed by Mary Kearney at the CROI 2014 session patients are potentially more enticing in view of the on HIV Persistence [28] – is ‘those cells which contain

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replication competent HIV-1 and which contribute Extrapolation of innovative technologies used in to rebound viraemia on cessation of ART’. The con- studies [41], that include total body imaging, flict lies in the issue that over 90% of measureable are currently being explored, which may be less (or viral DNA by most standard assays may be replication more) intrusive to patients but could give a better incompetent and therefore not be part of the reser- handle on sites and total body quantification of voir, (as defined above) and yet markers such as total virus. For these to be HIV-specific, however, an or integrated DNA – which capture all this DNA – in-vivo cell marker of latent infection will need appear to have some clinical utility [24&,29]. Newer to be developed, and this remains a substantial assays which can address the discrepancies between challenge. viral outgrowth assays (VOAs) and PCR-based methods will be needed [26&&], such as the promising Tat/rev-induced limiting dilution assay (TILDA) [30], NEW INTERVENTIONS which may help bridge the gap between clinical A cure for HIV is very likely to require a combination utility and apparent virological inconsistencies. of innovative interventions, the development of There remains a question as to how best to assimilate which is key to achieving eventual success. these new assays into clinical management. In patients with suppressed viraemia as measured by Antiretroviral therapy intensification the standard viral load assays to less than 20 copies ART intensification strategies have yielded limited HIV RNA per ml on ART, what additional infor- success in suppressing low-level viral replication by mation could be gained from adding in results of ultrasensitive assays [43]; however, intensification ‘reservoir’ assays? At present, these data will be critical does lead to decreased levels of immune activation to inform endpoints from proof-of-concept interven- and inflammatory markers in some studies [44,45]. tion studies but may have little to add to standard A recent, randomized, open-label study of three care. versus five drugs (intensified with raltegravir and New sensitive assays of the reservoir are clearly a maraviroc) as ART in PHI showed no benefit in terms priority; however, current focus on the measure- of measures of reservoir or immune activation [46], ment of HIV DNA in the CD4þ T-cells in blood casting further doubt on the role of ART intensifica- neglects to assess the other potential anatomical tion in cure strategies. and cellular reservoirs. For example, cell types which may harbour latent infection include monocytes, Histone deacetylase inhibitors: proof of macrophages [31], naive CD4þ T cells [32], astro- concept or of clinical utility? cytes [33] and the recently described T-memory HDACis are epigenetic modifiers and have been stem cells [34]. Furthermore, the vast majority of investigated to purge the latent reservoir in early latently infected cells may also reside outside the pilot studies. Vorinostat has been shown to disrupt peripheral circulation within the lymphoid tissue of HIV latency [47], with evidence of increased cell- the gastrointestinal tract [35–37], central nervous associated RNA during dosing but without system (CNS), spleen and lymph nodes [38]. These reduction in the size of the HIV reservoir as sanctuary sites are likely to account for a significant measured by HIV DNA in PBMCs or in rectal tissue burden of the reservoir and new methods to identify biopsies [48]. The dosing interval of vorinostat (and these are needed. possibly other HDACis) may also be important, as Recent high profile cases such as the Mississippi there is recent evidence for a blunting of response if [39] and Milan Babies [40] and the Boston patients multiple doses are given too close together [49]. The [13], in which initial hopes of cure were dashed by optimum dosing schedule for HDACis to induce subsequent viral rebound, highlight that current maximum HIV expression remains unclear. measures of the reservoir – even when undetectable For a latency-activating intervention to be effec- as in the latter cases – may fail to quantify the tive, it is likely that it will need to induce the reservoir beyond peripheral blood mononuclear production of viral RNA, translation of this RNA cells (PBMCs). New methods are needed and may into viral and the eventual release of new involve imaging with radiopharmaceuticals [41] or virions, ideally with associated host cell death. use of novel molecular markers, for example, the Concerns regarding ‘post-transcriptional block’, in chromatin modifier BCL11B which may be associ- which viral RNA transcription does not lead to ated with latent infection in the CNS [42]. However, protein production, have arisen following data such the question remains as to whether some blood as those from a primary T-cell model in which assays can act as surrogate markers of these tissue vorinostat and disulfiram increased viral trans- reservoirs, thereby negating the need for more cription but failed to enhance translation into intensive biopsies and sampling in future studies. HIV protein [50]. In contrast, more potent HDACis

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Advancing the HIV cure agenda Thornhill et al. ve HIV-1 ¨ T cells of HIV-infected þ T cells þ ve acute HIV-1 ¨ count, inflammatory biomarkers and viral reservoir in treatment-naı þ T-cell HIV reservoir T-cells þ þ dose-escalation study to examine safety, tolerability, dose and pharmacokinetics of VRC01 interruption in chronic HIV-1 infected patients with a lowabsolute circulating CD4 HIV-DNA reservoir activity of 3BNC117 (broadlyuninfected neutralizing) volunteers monoclonal antibody in HIV-infected and HIV- by intravenous infusion), in HIV-infected people receiving cART viral load less than 50 impact on the decay of latently infected CD4 the CD4 combination with autologous HIV-1-specificposttreatment cytotoxic control T amongst lymphocyte treatment-naı (CTL) infusion achieve a HAART (TDF/FTC/EFV) or mega-HAARTare (TDF/FTC/EFV enrolled and in MVC SEARCH and 010 RAL) study for participants who controllers active antiretroviral therapy patients receiving stable antiretroviral therapy The primary hypothesis isin that CD4 3 days of disulfiram will result in an increase in HIV transcription USA I This is the first clinical trial of the VRC-HIVMAB060-00-AB (VRC01) monoclonal antibody. This is a France NA A pilot study evaluating the maintenance of viral suppression after 24 weeks of therapeutic USA I A phase 1, open-label, dose-escalation study of the safety, pharmacokinetics and antiretroviral Germany III A multicentre, open-label, nonrandomized trial to evaluate treatment with MDC HAART and its China III The purpose of this study is to assess the ability of the early initiation of cART or cART in Thailand III This is a protocol designed to randomize subjects with acute HIV infection to receive standard Spain II Pilot study of the effect of maraviroc on the latency and reservoir of HIV-1 in patients taking highly a a below also have an acute infection arm Current clinical trials in the field of HIV cure research a (NCT01950325) (NCT01876862) (NCT02018510) HIV-1 (NCT02231281) (NCT0079626) and reservoir of HIV-1 (NCT00795444) New era study: treatment with multidrug class (MDC) CHERUB 001 – intravenous immunoglobulin UK I A proof-of-concept study examining the effect of high dosage IVIG in ART-treated acute infection on ACTG A5308 (NCT01777997) USA IV Single-arm, open-label study to evaluate the effect of fixed-dose TDF/FTC/RPV on T-cell activation, BMS-936559 – anti-PD L1 (NCT02028403)VRC 601 – broadly neutralizing monoclonal antibody USA I This study will evaluate the safety, PK data, and immune response to BMS-936559 (administered Towards HIV functional cure – ULTRASTOP a 3BNC117 – broadly neutralizing monoclonal antibody a HAART in HIV-infected patients Early cART and cARTHIV-1-specific in CTL combination infusion with in autologous the treatment of acute Vorinostat: HDACi (NCT01365065)Vorinostat: HDACi (NCT01319383) Australia USA II I/II To assess safety and effect on HIV transcription of A vorinostat study in of patients the receiving effect suppressive of cART vorinostat on HIV RNA expression in resting CD4 Antiretroviral therapy for acute HIV infection Disulfiram (NCT01944371) USA I/II To determine the safety, pharmacology and bioactivity of disulfiram in treated HIV-infected adults. Effect of a CCR5 co-receptor antagonist on the latency Table 1. Trial (Clinicaltrials.gov identifier)Chronic HIV infection Location Phase Intervention Those with Antibody trials Latency reserving agents Acute HIV

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HIV infections and AIDS ed T-cell gains þ patients. þ zeta -changed T cells and IL-2 of PHI diagnosis on HIV-1 reservoir p24. By adding lenalidomide,might an be immunomodulator, enhanced. it is anticipated that the effect of Vacc-4x expressing the MazF endoribonuclease gene in HIV cells genetically modified atsphamide the conditioning. CCR5 gene by zinc finger nucleases following cyclopho- of autologous T cells transduced with VRX496 in HIV-infected individuals. rhuGM-CSF, and HIV-1 reactivationinfected using adults romidepsin, on on cART the viral reservoir in suppressed HIV-1- optimized ART with undetectable plasma HIV RNA safety, tolerability, and activation of HIV-1 expression 1), can inhibit HIVprotein infection named by C46. removing CCR5 from bone marrow and WBCs, and producing a vaccine (ChAdV63.HIVconsv and MVA.HIVconsv,HIV-1 and infected vorinostat adults on on viral 4 reservoir drug in cART) suppressed patients on combination antiretroviral therapy nucleases SB-278 in HIV-infected patients who have exhibited suboptimal CD4 during long-term cART. USAUK I/II To determine the safety and activity of an experimental anti-HIV treatment using autologous CD4- To investigate the impact of more than 1 year of suppressive ART in adults initiated within 3 months Germany I/II Vacc-4x is a peptide-based HIV immunotherapy aimed to strengthen the immune response to HIV USA I Evaluate the safety and immunogenicity of autologous CD4 T cells modified with a retroviral vector USA I/II The purpose of this study is to evaluate the safety and tolerability of repeat doses of autologous T- USA I/II An open-label study to evaluate the tolerability, trafficking and therapeutic effects of repeated doses Denmark I/II A study to evaluate the safety and effect of therapeutic HIV-1 immunization using Vacc-4x and USA IUSA Proof-of-principle study of pulse dosing of IL-15 to I/II deplete the reservoir in HIV-infected people on A study looking at whether an experimental gene transfer agent, LVsh5/C46 (also known as Cal- UK II An study to evaluate the safety and effect of therapeutic HIV-1 immunization using a prime boost USA I Dose-escalation study of autologous T-cells genetically modified at the CCR5 gene by zinc finger a ) Continued ( exogenous IL-2 in HIV patients antiretroviral therapy HIV-1-infected ART (NCT01704781) for HIV gene therapy (NCT01787994) after cyclophosphamide conditioning (NCT02225665) doses of autologous T(NCT00295477) cells with VRX496 in HIV and vaccine Vacc-4x forreservoir reduction (NCT02092116) of latent HIV interleukin-15 complex (NCT02191098) transfer construct Cal-1 toinfection treat (NCT01734850) HIV-1 prime boost vaccine genetically modified at thenucleases CCR5 (NCT01044654) gene by zinc finger RIVER: Research In Viral Eradication of HIV Reservoirs. CD4-ZETA gene-modified T cells with and without HEATHER: HIV reservoir targeting with early Vacc-4x and lenalidomide vs. vacc-4x and placebo in MazF-T: Redirected MazF CD4 autologous T cells Repeat doses of SB-728mR-T (zinc finger nucleases) Romidepsin: HDACi (NCT01933594)VRX496: Tolerability and therapeutic effects of repeated USA I/II A study of single-dose romidepsin in HIV-infected adults with suppressed viraemia on cART to assess REDUC: Safety and efficacy of the HDACi romidepsin ALT-803: recombinant human super agonist Cal-1: Safety study of a dual anti-HIV gene a Safety and efficacy of the HDACi vorinostat and a Poly-ICLC: TLR-3 agonist (NCT02071095) USA I/II Investigating the adjuvant, Poly-ICLC to establish if it is safe and well tolerated in HIV-1-infect SB-728-T: Dose-escalation study of autologous T-cells Table 1 Observational studies Gene therapy Trial (Clinicaltrials.gov identifier) Location Phase Intervention Novel combination therapies

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Advancing the HIV cure agenda Thornhill et al.

have shown promise in phase 1 trials. Romidepsin was well tolerated, with induction of HIV transcrip- tion resulting in plasma viraemia [51&]. Panobino- stat led to an increase in cell-associated unspliced (CA-US) RNA levels, an increased detection of plasma HIV RNA and a transient decrease in HIV DNA [52], providing some preliminary evidence that problems associated with post-transcriptional block might be surmountable. The negative downstream impact of new agents must also be considered. For example, HDACis may suppress the ability of cytotoxic T lymphocytes (CTLs) to kill HIV-infected cells, potentially limiting the role of native immunity or immunotherapy in cure strategies [53]. HDACis have also been associ- ated with prolonged nonspecific gene expression

favirenz; FTC, emtricitabine; HAART, highly active antiretrovial 84 days following administration [3]. More potent

l transplant research. Source: www.clinicaltrials.gov. Adapted from HDACis may be increasingly effective at reversing latency, but may have worse and potentially longer lasting side-effect profiles. Furthermore with new tenofovir. potential reservoir activators in the pipeline (reviewed elsewhere [54]), further development of accurate in-vitro T-cell models will be needed to characterize potential antilatency molecules [55]. Although it is clear that HDACis alone are not the answer to an HIV cure, if they can be used to establish proof-of-principle that ‘latent’ provirus can be activated and re-awakened, it will provide Reservoirs Cohort (AHRC) study undergoing chemotherapy infection be studied infection, either with an immunological control (ALT), either a virological control (HIV controllers) a springboard for further mechanistic studies and drug development. Accordingly, they remain an important drug class and arguably the best currently available in the pharmacy.

Combining interventions: a role for immunotherapy Activating the latent reservoir alone is unlikely to be USA Decay of HIV-1 reservoirs in individuals on long-term antiretroviral therapy: The ACTG HIV UK Prospective observational study of HIV-positive individuals on suppressive HAART with malignancy Thailand To describe clinical, immunological and virological characteristics of persons with acute HIV UgandaUSA To measure and learn about the latent HIV reservoir in Ugandans with HIV HIV-infected patients on long-term antiretroviral therapy, untreated patients and elite controllers will sufficient to eradicate HIV infection, and additional augmentation or restoration of immune function may be required. ‘Kick and kill’ describes this dual approach of activating the quiescent latent reservoir with agents such as HDACis (the ‘kick’), in conjunc- tion with augmenting or priming the immune response in order to eliminate the resulting replica- tion competent virus (the ‘kill’) [4]. Ex-vivo data demonstrate that stimulating HIV-specific CTLs prior to reactivating latent HIV may be essential for successful eradication efforts [56]. This strategy is currently under investigation in clinical trials. For

) example, the Medical Research Council and Research into Viral Eradication of HIV Reservoirs (MRC RIVER) trial in the UK which will evaluate the combination of the Vorinostat and vaccination Continued ( (Prime: ChAd.V63.HIVconsv; boost:MVA.HIV- consv), and a similar phase I/IIa study in Denmark (AHRC) study cohort study cohort in a high-risk population HIV reservoir in virally suppressed Ugandans studies ACTG A5321: The ACTG HIV Reservoirs Cohort CHERUB 003: prospective HIV chemotherapy Establish and characterize an acute HIV infection Quantitative measurement and correlates of the latent The use of leukapheresis to support HIV pathogenesis CODEX (the ‘Extreme’ cohort) HIV Controllers Francewhich will The main objectiveevaluate is to gather in common cohort patients with a particular resistance to HIV the safety and effect of thera- Table 1 Trial (Clinicaltrials.gov identifier) Location Phase Intervention Also has an acute infection arm. Only trials which arehttp://www.treatmentactiongroup.org/cure/trials. open or closeda but not yet reported have been included. This list excludes therapeutic vaccine trials, chemotherapy and stem cel cART, combination antiretroviral therapy;therapy; CCR5, ICLC, C-C polyinosinic-polycytidylic chemokine acid receptor stabilized type with 5; polylysine CHERUB, and Collaborative carboxymethylcellulose; HIV MVC, Eradication miraviroc; of RAL, Reservoirs:peutic raltegravir; UK TDF, BRC; EFV, e HIV immunization using Vacc-4x and

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HIV infections and AIDS

rhuGM-CSF, and romidepsin (EudraCT number further confirmed cases of HIV cure. However, one 2013-004747-23) [57]. might hope that the surge of interest in curing HIV In other approaches, broadly neutralizing anti- that has followed – from basic science to clinical bodies have shown efficacy in Rhesus monkeys trials of new agents – will eventually lead to further [58&&], with a first in human phase I study now breakthroughs. The next 5 years will be a critical test enrolling. Other modulators of immune function of this effort and investment. also look interesting as potential combination approaches. Blockade of PD-1 – a marker of T cell Acknowledgements exhaustion – partially restores immune function The authors wish to thank the Medical Research Council, [59], and in patients on ART there is a correlation the Oxford and Imperial College NIHR Biomedical between PD-1 expression and the frequency of cell- Research Centres and the Oxford Martin School for associated HIV RNA or DNA [60]. PD-1 has been used financial support. with some success in malignant melanoma [61] and is currently under investigation as a potential thera- Financial support and sponsorship peutic target for latent HIV. A number of clinical This work was supported by the ‘Collaborative HIV trials testing new interventions either alone or in Eradication of Viral Reservoirs: UK BRC.’ combination with strategies such as vaccination [62] are on-going and are summarized in Table 1. Conflicts of interest Horizon scanning: new interventions for HIV The authors have no conflicting interests. cure Many novel strategies have shown promise in proof- REFERENCES AND RECOMMENDED READING of-concept studies. Gene editing by zinc finger Papers of particular interest, published within the annual period of review, have nucleases of C-C chemokine receptor type 5 in been highlighted as: & of special interest autologous CD4 cells has been successful in early- && of outstanding interest stage clinical trials [63]. The use of potent, neutral- 1. Deeks SG. Towards an HIV cure: a global scientific strategy. Nat Rev Immunol izing, HIV-specific monoclonal antibodies (mAbs) 2012; 12:607–614. in simian/human immunodeficiency virus-infected 2. Nakagawa F, Lodwick RK, Smith CJ, et al. Projected life expectancy of people with HIV according to timing of diagnosis. AIDS 2012; 26:335–343. rhesus monkeys has shown promising results and 3. Elliot JH, Wightman F, Solomon A, et al. Activation of HIV transcription with suggests a role for mAb therapy for HIV in humans short-course vorinostat in HIV-infected patients on suppressive antiretroviral && therapy. PLoS Pathog 2014; 10:e1004473. doi:10.1371/journal.ppat. [58 ]. Radiolabelled antibodies to viral 1004473. have been investigated in mice; HIV-infected cells 4. Deeks SG. HIV: shock and kill. Nature 2012; 487:439–440. 5. Sugarman J. HIV cure research: expanding the ethical considerations. Ann were eliminated by targeting gp120 and gp41 viral Intern Med 2013; 159:490–491. proteins expressed on the surface of infected cells 6. Lo B, Grady C. Ethical considerations in HIV cure research: points to consider. Curr Opin HIV AIDS 2013; 8:243–249. with radiolabelled specific mAbs to these proteins 7. Samji H, Cescon A, Hogg RS, et al. Closing the gap: increases in life [64,65]. expectancy among treated HIV-positive individuals in the United States and Canada. PLoS One 2013; 8:e81355. In addition to this, a range of molecules such as 8. Valdez H, Connick E, Smith KY, et al. Limited immune restoration after 3 years’ those that act via protein kinase C (e.g., prostratin, suppression of HIV-1 replication in patients with moderately advanced dis- ease. AIDS 2002; 16:1859–1866. bryostatin), inhibitors of DNA methylation, and 9. Lederman MM, Calabrese L, Funderburg NT, et al. Immunologic failure agents (e.g., disulfiram) that target the protein despite suppressive antiretroviral therapy is related to activation and turnover of memory CD4 cells. J Infect Dis 2011; 204:1217–1226. kinase B are under investigation [66]. Early results 10. Hunt PW, Cao HL, Muzoora C, et al. Impact of CD8þ T-cell activation on suggest that a single agent or sole interventions will CD4þ T-cell recovery and mortality in HIV-infected Ugandans initiating anti- retroviral therapy. AIDS 2011; 25:2123–2131. not suffice for HIV eradication and given the large 11. Borok MZ, Busakhala N, Makadzange T, Hakim J. Setting the research agenda repertoire of agents in development, one of the key in a resource-limited setting – viewpoint. J Acquir Immune Defic Syndr 2014; 65 (Suppl. 1):S3–S4. questions for future clinical trials will be which 12. Fox J. Available at http://www.cherub.uk.net/survey-on-hiv-cure-research combination of interventions should be used. 2014. [Accessed 19 September 2014] 13. Henrich T, Hanhauser E, Sirignano MN, et al. HIV-1 rebound following We learnt very early in the HIV epidemic that allogeneic stem cell transplantation and treatment interruption. In: 21st monotherapy approaches were unlikely to be suc- Conference on Retroviruses and Opportunistic Infections; Boston, USA; 2014; abstract 144LB. cessful in halting viral replication – the same is 14. El-Sadr WM, Lundgren J, Neaton JD, et al. CD4þ count-guided interruption of likely to be even more pertinent for approaches to antiretroviral treatment. N Engl J Med 2006; 355:2283–2296. 15. Fidler S, Porter K, Ewings F, et al. Short-course antiretroviral therapy in primary HIV cure. HIV infection. N Engl J Med 2013; 368:207–217. 16. Volberding P, Demeter L, Bosch RJ, et al. Antiretroviral therapy in acute and recent HIV infection: a prospective multicenter stratified trial of intentionally interrupted treatment. AIDS 2009; 23:1987–1995. CONCLUSION 17. Ananworanich J, Gayet-Ageron A, Le Braz M, et al. CD4-guided scheduled treatment interruptions compared with continuous therapy for patients Since the publication of the cure of the Berlin infected with HIV-1: results of the STACCATO randomised trial. Lancet patient in February 2009 [67], there have been no 2006; 368:459–465.

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Advancing the HIV cure agenda Thornhill et al.

18. Haleyur Giri Setty MK, Hewlett IK. Point of care technologies for HIV. AIDS 43. McMahon D, Jones J, Wiegand A, et al. Short-course raltegravir intensification Res Treat 2014; 2014:497046. does not reduce persistent low-level viremia in patients with HIV-1 suppres- 19. Saez-Cirion A, Bacchus C, Hocqueloux L, et al. Posttreatment HIV-1 con- sion during receipt of combination antiretroviral therapy. Clin Infect Dis 2010; & trollers with a long-term virological remission after the interruption of early 50:912–919. initiated antiretroviral therapy ANRS VISCONTI Study. PLoS Pathogens 44. Buzon MJ, Massanella M, Llibre JM, et al. HIV-1 replication and immune 2013; 9:e1003211. dynamics are affected by raltegravir intensification of HAART-suppressed This study describes the virological and immunological characteristics in the subjects. Nat Med 2010; 16:460–465. posttreatment control VISCONTI cohort. 45. Hatano H, Strain MC, Scherzer R, et al. Increase in 2-long terminal repeat 20. WHO. Consolidated guidelines on the use of antiretroviral drugs for treating circles and decrease in D-dimer after raltegravir intensification in patients with and preventing HIV infection. Available at http://www.who.int/hiv/pub/guide treated HIV infection: a randomized, placebo-controlled trial. J Infect Dis lines/arv2013/download/en/2013. [Accessed 23 September 2014]. 2013; 208:1436–1442. 21. WHO. Consolidated guidelines on HIV prevention, diagnosis, treatment and 46. Markowitz M, Evering TH, Garmon D, et al. A randomized open-label study of care for key populations. Available at http://www.who.int/hiv/pub/guidelines/ 3- versus 5-drug combination antiretroviral therapy in newly HIV-1-infected keypopulations/en/2014. [Accessed 23 September 2014] individuals. J Acquir Immune Defic Syndr 2014; 66:140–147. 22. Stoehr W, Fidler S, McClure M, et al. Duration of HIV-1 viral suppression on 47. Archin NM, Liberty AL, Kashuba AD, et al. Administration of vorinostat disrupts cessation of antiretroviral therapy in primary infection correlates with time on HIV-1 latency in patients on antiretroviral therapy. Nature 2012; 487:482–485. therapy. PLoS One 2013; 8:e78287. 48. Elliott JS, Wightman A, Smith F, et al. The safety and effect of multiple doses of 23. Whitney JB, Hill AL, Sanisetty S, et al. Rapid seeding of the viral reservoir prior vorinostat on HIV transcription in HIVþ patients receiving cART. In: 20th & to SIV viraemia in rhesus monkeys. Nature 2014; 512:74–77. Conference on Retroviruses and Opportunistic Infections; 3–6 March 2013; This study shows that the viral reservoir is very rapidly established (within 3 days) in Atlanta, GA; 2013. Rhesus monkeys and is important in informing the strategies which may attempt to 49. Archin NM, Bateson R, Tripathy MK, et al. HIV-1 expression within resting minimize the seeding of the latent reservoir. CD4þ T cells after multiple doses of vorinostat. J Infect Dis 2014; 210:728– 24. Williams JP, Hurst J, Stohr W, et al. HIV-1 DNA predicts disease progression 735. & and posttreatment virological control. eLife 2014; e03821. 50. Mohammadi P,di Iulio J, MunozM, et al. Dynamics of HIVlatency and reactivation This study reports an association between HIV-1 DNA levels at the time of in a primary CD4þ T cell model. PLoS Pathog 2014; 10:e1004156. stopping antiretroviral therapy and the time taken for plasma viraemia to become 51. Søgaard OS, Graversen ME, Leth S, et al. The HDAC inhibitor romidepsin is detectable in those treated in acute HIV infection. & safe and effectively reverses HIV-1 latency in vivo as measured by standard 25. Thornhill J, Inshaw J, Oomeer S, et al. Enhanced normalisation of CD4/CD8 clinical assays. In: 20th International AIDS Conference; Melbourne, Australia; ratio with early antiretroviral therapy in primary HIV infection. 3 November 2014; abstract TUAA0106LB. 2014. In: HIV Drug Therapy Glasgow Congress; 2014. This abstract reports that the HDACi romidepsin induced plasma viraemia, 26. Eriksson S, Graf EH, Dahl V, et al. Comparative analysis of measures of viral supporting the proof of concept that in-vivo latency reversal is possible with a && reservoirs in HIV-1 eradication studies. PLoS Pathog 2013; 9:e1003174. single latency reversing agent. This study compares the currently used assay for quantifying latent HIV reservoir in 52. Rasmussen TA, Tolstrup M, Brinkmann CR, et al. Panobinostat, a histone HIV eradication studies and shows a lack of a correlation between culture and deacetylase inhibitor, for latent-virus reactivation in HIV-infected patients on PCR-based methods. suppressive antiretroviral therapy: a phase 1/2, single group, clinical trial. 27. Chun TW, Carruth L, Finzi D, et al. Quantification of latent tissue reservoirs Lancet HIV 2014; 1:e13–e21. and total body viral load in HIV-1 infection. Nature 1997; 387:183–188. 53. Jones RB, O’Connor R, Mueller S, et al. Histone deacetylase inhibitors impair 28. Kearney M. HIV persistence, oral presentation; CROI 2014. Available at the elimination of HIV-infected cells by cytotoxic T-lymphocytes. PLoS Pathog http://www.croiwebcasts.org/console/player/22272?mediaType=audio&. 2014; 10:e1004287. [Accessed 23 September 2014] 54. Battistini A, Sgarbanti M. HIV-1 latency: an update of molecular mechanisms 29. Rouzioux C, Hubert JB, Burgard M, et al. Early levels of HIV-1 DNA in and therapeutic strategies. 2014; 6:1715–1758. peripheral blood mononuclear cells are predictive of disease progression 55. Spina CA, Anderson J, Archin NM, et al. An in-depth comparison of latent HIV- independently of HIV-1 RNA levels and CD4þ T cell counts. J Infect Dis 2005; 1 reactivation in multiple cell model systems and resting CD4þ T cells from 192:46–55. aviremic patients. PLoS Pathog 2013; 9:e1003834. 30. Procopio F, Fromentin R, Kulpa D, et al. A novel assay that precisely measures 56. Shan L, Deng K, Shroff NS, et al. Stimulation of HIV-1-specific cytolytic T the size of the latent HIV reservoir reveals that ART-naı¨ve individuals harbour a lymphocytes facilitates elimination of latent viral reservoir after virus reactiva- large pool of latently infected CD4þ T cells. In: 20th International AIDS tion. Immunity 2012; 36:491–501. Conference; Towards a Cure Symposium; 2014; Melbourne, Australia; 57. Register ECT. An open phase I/IIa study to evaluate the safety and effect of abstract OA4-6 LB. therapeutic HIV-1 immunization using Vacc-4x þ rhuGM-CSF, and HIV-1 31. Kumar A, Abbas W, Herbein G. HIV-1 latency in monocytes/macrophages. reactivation using romidepsin, on the viral reservoir in virologically suppressed Viruses 2014; 6:1837–1860. HIV-1 infected adults on cART. 2014. [cited 13 August 2014]. Available at 32. Wightman F, Solomon A, Khoury G, et al. Both CD31(þ) and CD31() naive https://www.clinicaltrialsregister.eu/ctr-search/trial/2013-004747-23/ CD4(þ) T cells are persistent HIV type 1-infected reservoirs in individuals DK#A. [Accessed 19 September 2014]. receiving antiretroviral therapy. J Infect Dis 2010; 202:1738–1748. 58. Barouch DH, Whitney JB, Moldt B, et al. Therapeutic efficacy of potent 33. Churchill M, Nath A. Where does HIV hide? A focus on the central nervous && neutralizing HIV-1-specific monoclonal antibodies in SHIV-infected rhesus system. Curr Opin HIV AIDS 2013; 8:165–169. monkeys. Nature 2013; 503:224–229. 34. Buzon MJ, Sun H, Li C, et al. HIV-1 persistence in CD4þ T cells with stem cell- This study outlines the utility of broadly neutralizing antibodies (bNAbs) in the SIV like properties. Nat Med 2014; 20:139–142. with prolonged control of replication occurring in a subset in Rhesus monkeys. The 35. Mehandru S, Poles MA, Tenner-Racz K, et al. Primary HIV-1 infection is bNAbs were also associated with a decrease in SIV DNA in blood and tissues, associated with preferential depletion of CD4þ T lymphocytes from effector outlining their potential therapeutic use in HIV. sites in the gastrointestinal tract. J Exp Med 2004; 200:761–770. 59. Barber DL, Wherry EJ, Masopust D, et al. Restoring function in exhausted 36. Brenchley JM, Schacker TW, Ruff LE, et al. CD4þ T cell depletion during all CD8 T cells during chronic viral infection. Nature 2006; 439:682–687. stages of HIV disease occurs predominantly in the gastrointestinal tract. J Exp 60. Barouch DH, Deeks SG. Immunologic strategies for HIV-1 remission and Med 2004; 200:749–759. eradication. Science (New York, NY) 2014; 345:169–174. 37. Chun T-W, Nickle DC, Justement JS, et al. Persistence of HIV in gut- 61. Robert C, Ribas A, Wolchok JD, et al. Antiprogrammed-death-receptor-1 associated lymphoid tissue despite long-term antiretroviral therapy. J Infect treatment with pembrolizumab in ipilimumab-refractory advanced melanoma: Dis 2008; 197:714–720. a randomised dose-comparison cohort of a phase 1 trial. Lancet 2014; 38. North TW, Higgins J, Deere JD, et al. Viral sanctuaries during highly active 384:1109–1117. antiretroviral therapy in a nonhuman primate model for AIDS. J Virol 2010; 62. Fisher AK, Voronin Y, Jefferys R. Therapeutic HIV vaccines: prior setbacks, 84:2913–2922. current advances, and future prospects. Vaccine 2014; 32:5540–5545. 39. Giacomet V, Trabattoni D, Zanchetta N, et al. No cure of HIV infection in a 63. Tebas P, Stein D, Tang WW, et al. Gene editing of CCR5 in autologous CD4 child despite early treatment and apparent viral clearance. Lancet 2014; T cells of persons infected with HIV. N Engl J Med 2014; 370:901–910. 384:1320. 64. Dadachova E, Kitchen SG, Bristol G, et al. Preclinical evaluation of a 213Bi- 40. Persaud D. The path towards HIV-1 cure: lessons from the ‘Mississippi Child’. labeled 2556 antibody to HIV-1 gp41 glycoprotein in HIV-1 mouse models as In: 20th International AIDS Conference; Melbourne, Australia; 2014; abstract a reagent for HIV eradication. PLoS One 2012; 7:e31866. MOSY0501. 65. Dadachova E, Patel MC, Toussi S, et al. Targeted killing of virally infected cells 41. Lau CY, Maldarelli F, Eckelman WC, Neumann RD. Rational development of by radiolabeled antibodies to viral proteins. PLoS Med 2006; 3:e427. radiopharmaceuticals for HIV-1. Nucl Med Biol 2014; 41:299–308. 66. Kent SJ, Reece JC, Petravic J, et al. The search for an HIV cure: tackling latent 42. Desplats P, Dumaop W, Smith D, Adame A, et al. Molecular and pathologic infection. Lancet Infect Dis 2013; 13:614–621. insights from latent HIV-1 infection in the human brain. Neurology 2013; 67. Hutter G, Nowak D, Mossner M, et al. Long-term control of HIV by CCR5 Del- 80:1415–1423. ta32/Delta32 stem-cell transplantation. N Engl J Med 2009; 360:692–698.

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