HIV-1 control after transient antiretroviral treatment initiated in primary infection: role of patient characteristics and effect of therapy

Energy demanding RNA and protein metabolism drive dysfunctionality of HIV-specific T cell changes during chronic HIV infection

Antiretroviral treatment of HIV infected individuals cannot eliminate the HIV reservoir and immune control of HIV is rarely seen upon treatment interruption. In long-term non-progressors (LTNP), an effective CD8 T cell response is thought to contribute to be immune control of HIV. Here we studied the transcriptional profile of virus specific CD8 T cells during the asymptomatic phase of disease, to gain molecular insights in CD8 T cell functionality in HIV progressors and different groups of LTNP: HLA-B*57 LTNP, non-HLA-B*57 LTNP and individuals carrying the MAVS minor genotype (rs7262903/rs7269320). Principal component analysis revealed distinct overall transcriptional profiles between the groups. The transcription profile of HIV-specific CD8 T cells of LTNP groups was associated with increased cytokine/IL-12 signaling and protein/RNA metabolism pathways, indicating an increased CD8 T cell functionality. Although the transcription profile of CMV-specific CD8 T cells differed from that of HIV-specific CD8 T cells, with mainly an upregulation of gene expression in progressors, similar affected pathways were identified. Moreover, CMV-specific CD8 T cells from progressors showed increased expression of genes related to effector functions and suggests recent antigen exposure. Our data shows that changes in cytokine signaling and the energy demanding RNA and protein metabolism are related to CD8 T cell dysfunction, which may indicate that mitochondrial dysfunction is an important driver of T cell dysfunctionality during chronic HIV infection. Indeed, improvement of mitochondrial function by IL-12 and mitoTempo treatment, enhanced in vitro IFNγ release by PBMC from PWH upon HIV gag and CMV pp65 peptide stimulation. Our study provides new insights into the molecular pathways associated with CD8 T cell mediated immune control of chronic HIV infection which is important for the design of novel treatment strategies to restore or improve the HIV-specific immune response.

"Block and lock" viral integration sites in persons with drug-free control of HIV-1 infection

PURPOSE OF REVIEW

Elite controllers (ECs) and Posttreatment controllers (PTCs) represent a small subset of individuals who are capable of maintaining drug-free control of HIV plasma viral loads despite the persistence of a replication-competent viral reservoir. This review aims to curate recent experimental studies evaluating viral reservoirs that distinguish EC/PTC and may contribute to their ability to maintain undetectable viral loads in the absence of antiretroviral therapy.

RECENT FINDINGS

Recent studies on ECs have demonstrated that integration sites of intact proviruses in EC/PTC are markedly biased towards heterochromatin regions; in contrast, intact proviruses in accessible and permissive chromatin were profoundly underrepresented. Of note, no such biases were noted when CD4 + T cells from EC were infected directly ex vivo, suggesting that the viral reservoir profile in EC is not related to altered integration site preferences during acute infection, but instead represents the result of immune-mediated selection mechanisms that can eliminate proviruses in transcriptionally-active euchromatin regions while promoting preferential persistence of intact proviruses in nonpermissive genome regions. Proviral transcription in such "blocked and locked" regions may be restricted through epigenetic mechanisms, protecting them from immune-recognition but presumably limiting their ability to drive viral rebound. While the exact immune mechanisms driving this selection process remain undefined, recent single-cell analytic approaches support the hypothesis that HIV reservoir cells are subject to immune selection pressure by host factors.

SUMMARY

A "blocked and locked" viral reservoir profile may constitute a structural virological correlate of a functional cure of HIV-1 infection. Further research into the immunological mechanism promoting HIV-1 reservoir selection and evolution in EC/PTC is warranted and could inform foreseeable cure strategies.

Early antiretroviral therapy favors post-treatment SIV control associated with the expansion of enhanced memory CD8+ T-cells

HIV remission can be achieved in some people, called post-treatment HIV controllers, after antiretroviral treatment discontinuation. Treatment initiation close to the time of infection was suggested to favor post-treatment control, but the circumstances and mechanisms leading to this outcome remain unclear. Here we evaluate the impact of early (week 4) vs. late (week 24 post-infection) treatment initiation in SIVmac251-infected male cynomolgus macaques receiving 2 years of therapy before analytical treatment interruption. We show that early treatment strongly promotes post-treatment control, which is not related to a lower frequency of infected cells at treatment interruption. Rather, early treatment favors the development of long-term memory CD8+ T cells with enhanced proliferative and SIV suppressive capacity that are able to mediate a robust secondary-like response upon viral rebound. Our model allows us to formally demonstrate a link between treatment initiation during primary infection and the promotion of post-treatment control and provides results that may guide the development of new immunotherapies for HIV remission.

Higher HIV-1 Env gp120-Specific Antibody-Dependent Cellular Cytotoxicity (ADCC) Activity Is Associated with Lower Levels of Defective HIV-1 Provirus

A cure for HIV-1 (HIV) remains unrealized due to a reservoir of latently infected cells that persist during antiretroviral therapy (ART), with reservoir size associated with adverse health outcomes and inversely with time to viral rebound upon ART cessation. Once established during ART, the HIV reservoir decays minimally over time; thus, understanding factors that impact the size of the HIV reservoir near its establishment is key to improving the health of people living with HIV and for the development of novel cure strategies. Yet, to date, few correlates of HIV reservoir size have been identified, particularly in pediatric populations. Here, we employed a cross-subtype intact proviral DNA assay (CS-IPDA) to quantify HIV provirus between one- and two-years post-ART initiation in a cohort of Kenyan children (n = 72), which had a median of 99 intact (range: 0-2469), 1340 defective (range: 172-3.84 × 104), and 1729 total (range: 178-5.11 × 104) HIV proviral copies per one million T cells. Additionally, pre-ART plasma was tested for HIV Env-specific antibody-dependent cellular cytotoxicity (ADCC) activity. We found that pre-ART gp120-specific ADCC activity inversely correlated with defective provirus levels (n = 68, r = -0.285, p = 0.0214) but not the intact reservoir (n = 68, r = -0.0321, p-value = 0.800). Pre-ART gp41-specific ADCC did not significantly correlate with either proviral population (n = 68; intact: r = -0.0512, p-value = 0.686; defective: r = -0.109, p-value = 0.389). This suggests specific host immune factors prior to ART initiation can impact proviruses that persist during ART.

Factors associated with post-treatment control of viral load in HIV-infected patients: a systematic review and meta-analysis

OBJECTIVES

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 January 01, 2011, and July 01, 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 neutralizing 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 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.

CD8+ cells and small viral reservoirs facilitate post-ART control of SIV in Mauritian cynomolgus macaques

Sustainable HIV remission after antiretroviral therapy (ART) withdrawal, or post-treatment control (PTC), remains a top priority for HIV treatment. We observed surprising PTC in an MHC-haplomatched cohort of MHC-M3+ SIVmac239+ Mauritian cynomolgus macaques (MCMs) initiated on ART at two weeks post-infection (wpi). For six months after ART withdrawal, we observed undetectable or transient viremia in seven of eight MCMs. In vivo depletion of CD8α+ cells induced rebound in all animals, indicating the PTC was mediated, at least in part, by CD8α+ cells. We found that MCMs had smaller acute viral reservoirs than a cohort of identically infected rhesus macaques, a population that rarely develops PTC. The mechanisms by which unusually small viral reservoirs and CD8α+ cell-mediated virus suppression enable PTC can be investigated using this MHC-haplomatched MCM model. Further, defining the immunologic mechanisms that engender PTC in this model may identify therapeutic targets for inducing durable HIV remission in humans.

Transcriptomic Signatures of Human Immunodeficiency Virus Post-Treatment Control

Posttreatment controllers (PTCs) are rare HIV-infected individuals who can limit viral rebound after antiretroviral therapy interruption (ATI), but the mechanisms of this remain unclear. To investigate these mechanisms, we quantified various HIV RNA transcripts (via reverse transcription droplet digital PCR [RT-ddPCR]) and cellular transcriptomes (via RNA-seq) in blood cells from PTCs and noncontrollers (NCs) before and two time points after ATI. HIV transcription initiation did not significantly increase after ATI in PTCs or in NCs, whereas completed HIV transcripts increased at early ATI in both groups and multiply-spliced HIV transcripts increased only in NCs. Compared to NCs, PTCs showed lower levels of HIV DNA, more cell-associated HIV transcripts per total RNA at all times, no increase in multiply-spliced HIV RNA at early or late ATI, and a reduction in the ratio of completed/elongated HIV RNA after early ATI. NCs expressed higher levels of the IL-7 pathway before ATI and expressed higher levels of multiple cytokine, inflammation, HIV transcription, and cell death pathways after ATI. Compared to the baseline, the NCs upregulated interferon and cytokine (especially TNF) pathways during early and late ATI, whereas PTCs upregulated interferon and p53 pathways only at early ATI and downregulated gene translation during early and late ATI. In NCs, viral rebound after ATI is associated with increases in HIV transcriptional completion and splicing, rather than initiation. Differences in HIV and cellular transcription may contribute to posttreatment control, including an early limitation of spliced HIV RNA, a delayed reduction in completed HIV transcripts, and the differential expression of the IL-7, p53, and TNF pathways. IMPORTANCE The findings presented here provide new insights into how HIV and cellular gene expression change after stopping ART in both noncontrollers and posttreatment controllers. Posttreatment control is associated with an early ability to limit increases in multiply-spliced HIV RNA, a delayed (and presumably immune-mediated) ability to reverse an initial rise in processive/completed HIV transcripts, and multiple differences in cellular gene expression pathways. These differences may represent correlates or mechanisms of posttreatment control and may provide insight into the development and/or monitoring of therapeutic strategies that are aimed at a functional HIV cure.

Long-term antiretroviral therapy initiated in acute HIV infection prevents residual dysfunction of HIV-specific CD8+ T cells

Background

Harnessing CD8⁺ T cell responses is being explored to achieve HIV remission. Although HIV-specific CD8⁺ T cells become dysfunctional without treatment, antiretroviral therapy (ART) partially restores their function. However, the extent of this recovery under long-term ART is less understood.

Methods

We analyzed the differentiation status and function of HIV-specific CD8⁺ T cells after long-term ART initiated in acute or chronic HIV infection ex vivo and upon in vitro recall.

Findings

ART initiation in any stage of acute HIV infection promoted the persistence of long-lived HIV-specific CD8⁺ T cells with high expansion (P<0·0008) and cytotoxic capacity (P=0·02) after in vitro recall, albeit at low cell number (P=0·003). This superior expansion capacity correlated with stemness (r=0·90, P=0·006), measured by TCF-1 expression, similar to functional HIV-specific CD8⁺ T cells found in spontaneous controllers. Importanly, TCF-1 expression in these cells was associated with longer time to viral rebound ranging from 13 to 48 days after ART interruption (r =0·71, P=0·03). In contrast, ART initiation in chronic HIV infection led to more differentiated HIV-specific CD8⁺ T cells lacking stemness properties and exhibiting residual dysfunction upon recall, with reduced proliferation and cytolytic activity.

Interpretation

ART initiation in acute HIV infection preserves functional HIV-specific CD8⁺ T cells, albeit at numbers too low to control viral rebound post-ART. HIV remission strategies may need to boost HIV-specific CD8⁺ T cell numbers and induce stem cell-like properties to reverse the residual dysfunction persisting on ART in people treated after acute infection prior to ART release.

Funding

U.S. National Institutes of Health and U.S. Department of Defense.

Acute HIV-1 infection viremia associate with rebound upon treatment interruption

BACKGROUND

Analytic treatment interruption (ATI) studies evaluate strategies to potentially induce remission in people living with HIV-1 but are often limited in sample size. We combined data from four studies that tested three interventions (vorinostat/hydroxychloroquine/maraviroc before ATI, Ad26/MVA vaccination before ATI, and VRC01 antibody infusion during ATI).

METHODS

The statistical validity of combining data from these participants was evaluated. Eleven variables, including HIV-1 viral load at diagnosis, Fiebig stage, and CD4+ T cell count were evaluated using pairwise correlations, statistical tests, and Cox survival models.

FINDINGS

Participants had homogeneous demographic and clinical characteristics. Because an antiviral effect was seen in participants who received VRC01 infusion post-ATI, these participants were excluded from the analysis, permitting a pooled analysis of 53 participants. Time to viral rebound was significantly associated with variables measured at the beginning of infection: pre-antiretroviral therapy (ART) viral load (HR = 1.34, p = 0.022), time to viral suppression post-ART initiation (HR = 1.07, p < 0.001), and area under the viral load curve (HR = 1.34, p = 0.026).

CONCLUSIONS

We show that higher viral loads in acute HIV-1 infection were associated with faster viral rebound, demonstrating that the initial stage of HIV-1 infection before ART initiation has a strong impact on viral rebound post-ATI years later.

FUNDING

This work was supported by a cooperative agreement between the Henry M. Jackson Foundation for the Advancement of Military Medicine and the US Department of the Army (W81XWH-18-2-0040). This research was funded, in part, by the US National Institute of Allergy and Infectious Diseases (AAI20052001) and the I4C Martin Delaney Collaboratory (5UM1AI126603-05).

Towards a molecular profile of antiretroviral therapy-free HIV remission

PURPOSE OF REVIEW

To summarize the current status and highlight recent findings on predictive biomarkers for posttreatment HIV control (PTC) and virological remission. While historically, many studies focused on virological markers, there is an increasing tendency to enter immune and metabolic factors into the equation.

RECENT FINDINGS

On the virological side, several groups reported that cell-associated HIV RNA could predict time to viral rebound. Recent data hints at the possible importance of the genic location and chromatin context of the integrated provirus, although these factors still need to be assessed in relation to PTC and virological remission. Evidence from immunological studies highlighted innate and humoral immunity as important factors for prolonged HIV remission. Interestingly, novel metabolic markers have emerged, which offer additional angles to our understanding of latency and viral rebound.

SUMMARY

Facilitating PTC and virological remission remain top priorities for the HIV cure research. We advocate for clear and precise definitions for both phenomena in order to avoid misconceptions and to strengthen the conclusions that can be drawn. As no one-size-fits-all marker has emerged yet, more biomarkers are on the horizon, and viral rebound is a complex and heterogeneous process, it is likely that a combination of various biomarkers in cohesion will be necessary for a more accurate prediction of antiretroviral therapy-free HIV remission.

Elite and posttreatment controllers, two facets of HIV control

PURPOSE OF REVIEW

The quest for HIV-1 cure could take advantage of the study of rare individuals that control viral replication spontaneously (elite controllers) or after an initial course of antiretroviral therapy (posttreatment controllers, PTCs). In this review, we will compare back-to-back the immunological and virological features underlying viral suppression in elite controllers and PTCs, and explore their possible contributions to the HIV-1 cure research.

RECENT FINDINGS

HIV-1 control in elite controllers shows hallmarks of an effective antiviral response, favored by genetic background and possibly associated to residual immune activation. The immune pressure in elite controllers might select against actively transcribing intact proviruses, allowing the persistence of a small and poorly inducible reservoir. Evidence on PTCs is less abundant but preliminary data suggest that antiviral immune responses may be less pronounced. Therefore, these patients may rely on distinct mechanisms, not completely elucidated to date, suppressing HIV-1 transcription and replication.

SUMMARY

PTCs and elite controllers may control HIV replication using distinct pathways, the elucidation of which may contribute to design future interventional strategies aiming to achieve a functional cure.

Impact of antiretroviral therapy in primary HIV infection on natural killer cell function and the association with viral rebound and HIV DNA following treatment interruption

Natural Killer (NK) cells play a key role in controlling HIV replication, with potential downstream impact on the size of the HIV reservoir and likelihood of viral rebound after antiretroviral therapy (ART) cessation. It is therefore important to understand how primary HIV infection (PHI) disrupts NK cell function, and how these functions are restored by early ART. We examined the impact of commencing ART during PHI on phenotypic and functional NK cell markers at treatment initiation (baseline), 3 months, 1 year, and 2 years in seven well-characterised participants in comparison to HIV seronegative volunteers. We then examined how those NK cell properties differentially impacted by ART related to time to viral rebound and HIV DNA levels in 44 individuals from the SPARTAC trial who stopped ART after 48 weeks treatment, started during PHI. NK cell markers that were significantly different between the seven people with HIV (PWH) treated for 2 years and HIV uninfected individuals included NKG2C levels in CD56dim NK cells, Tim-3 expression in CD56bright NK cells, IFN-γ expressed by CD56dim NK cells after IL-12/IL-18 stimulation and the fraction of Eomes-/T-bet+ in CD56dim and CD56bright NK cells. When exploring time to viral rebound after stopping ART among the 44 SPARTAC participants, no single NK phenotypic marker correlated with control. Higher levels of IL-12/IL-18 mediated NK cell degranulation at baseline were associated with longer times to viral rebound after treatment interruption (P=0.028). Additionally, we found higher fractions of CD56dim NK cells in individuals with lower levels of HIV DNA (P=0.048). NKG2A and NKp30 levels in CD56neg NK cells were higher in patients with lower HIV DNA levels (p=0.00174, r=-0.49 and p=0.03, r= -0.327, respectively) while CD27 levels were higher in those with higher levels of HIV DNA (p=0.026). These data show NK cell functions are heterogeneously impacted by HIV infection with a mixed picture of resolution on ART, and that while NK cells may affect HIV DNA levels and time to viral rebound, no single NK cell marker defined delayed viral rebound.

Viral and Host Biomarkers of HIV Remission Post Treatment Interruption

PURPOSE OF REVIEW

HIV rebound/remission after antiretroviral therapy (ART) interruption is likely influenced by (a) the size of the inducible replication-competent HIV reservoir and (b) factors in the host environment that influence immunological pressures on this reservoir. Identifying viral and/or host biomarkers of HIV rebound after ART cessation may improve the safety of treatment interruptions and our understanding of how the viral-host interplay results in post-treatment control. Here we review the predictive and functional significance of recently suggested viral and host biomarkers of time to viral rebound and post-treatment control following ART interruption.

RECENT FINDINGS

There are currently no validated viral or host biomarkers of viral rebound; however, several biomarkers have been recently suggested. A combination of viral and host factors will likely be needed to predict viral rebound and to better understand the mechanisms contributing to post-treatment control of HIV, critical steps to developing a cure for HIV infection.

Contribution of Sex Differences to HIV Immunology, Pathogenesis, and Cure Approaches

Approximately 38 million people were living with human immunodeficiency virus (HIV) in 2020 and 53% of those infected were female. A variety of virological and immunological sex-associated differences (sexual dimorphism) in HIV infection have been recognized in males versus females. Social, behavioral, and societal influences play an important role in how the HIV pandemic has affected men and women differently. However, biological factors including anatomical, physiologic, hormonal, and genetic differences in sex chromosomes can each contribute to the distinct characteristics of HIV infection observed in males versus females. One striking example of this is the tendency for women to have lower HIV plasma viral loads than their male counterparts early in infection, though both progress to AIDS at similar rates. Sex differences in acquisition of HIV, innate and adaptive anti-HIV immune responses, efficacy/suitability of specific antiretroviral drugs, and viral pathogenesis have all been identified. Sex differences also have the potential to affect viral persistence, latency, and cure approaches. In this brief review, we summarize the major biological male/female sex differences in HIV infection and their importance to viral acquisition, pathogenesis, treatment, and cure efforts.

Cure and Long-Term Remission Strategies

The majority of virally suppressed individuals will experience rapid viral rebound upon antiretroviral therapy (ART) interruption, providing a strong rationale for the development of cure strategies. Moreover, despite ART virological control, HIV infection is still associated with chronic immune activation, inflammation, comorbidities, and accelerated aging. These effects are believed to be due, in part, to low-grade persistent transcription and trickling production of viral proteins from the pool of latent proviruses constituting the viral reservoir. In recent years there has been an increasing interest in developing what has been termed a functional cure for HIV. This approach entails the long-term, durable control of viral expression in the absence of therapy, preventing disease progression and transmission, despite the presence of detectable integrated proviruses. One such strategy, the block-and-lock approach for a functional cure, proposes the epigenetic silencing of proviral expression, locking the virus in a profound latent state, from which reactivation is very unlikely. The proof-of-concept for this approach was demonstrated with the use of a specific small molecule targeting HIV transcription. Here we review the principles behind the block-and-lock approach and some of the additional strategies proposed to silence HIV expression.

OUP accepted manuscript

Background

Methods

Results

Conclusions

Challenges and Promise of Human Immunodeficiency Virus Remission

Antiretroviral therapy effectively controls human immunodeficiency virus (HIV) replication but it is unable to fully eradicate the HIV reservoir and treatment must be life-long. Progress toward a strategy for HIV remission will require overcoming key hurdles to fill gaps in our understanding of HIV persistence, but the identification of individuals who have attained sterilizing or functional HIV cure show that such a goal is achievable. In this review, we first outline challenges in targeting the HIV reservoir, including difficulties identifying HIV-infected cells, ongoing work elucidating the complex intracellular environment that contribute to HIV latency, and barriers to reactivating and clearing the HIV reservoir. We then review reported cases of HIV sterilizing cure and explore natural models of HIV remission and the promise that such HIV spontaneous and posttreatment controllers may hold in our search for a broadly-applicable strategy for the millions of patients living with HIV.

Viral, inflammatory, and reservoir characteristics of posttreatment controllers

PURPOSE OF REVIEW

To provide an overview of studies to date that have identified posttreatment controllers (PTCs) and to explore current evidence around clinical characteristics, immune effector function, and inflammatory and viral reservoir characteristics that may underlie the control mechanism.

RECENT FINDINGS

PTCs are broadly defined as individuals capable of maintaining control of HIV replication after cessation of antiretroviral therapy (ART). While starting ART early after HIV infection is associated with PTC, genetic disposition or CD8+ T-cell function do not appear to explain this phenomenon, but these features have not been exhaustively analyzed in PTCs. A lower frequency of latently infected cells prior to stopping ART has been associated with achieving PTC, including a lower level of intact HIV DNA, but more studies are needed to map the genetic location, epigenetic characteristics, and tissue distribution of the intact HIV reservoir in PTCs.

SUMMARY

Current studies are small and heterogeneous and there is a significant need to agree on a uniform definition of PTC. Many aspects of PTC are still unexplored including whether specific features of genetic disposition, immune effector functions, and/or viral reservoir characteristics play a role in PTC. A large multisite international cohort study could aide in providing the important insights needed to fully understand PTC.

Non-invasive plasma glycomic and metabolic biomarkers of post-treatment control of HIV

Non-invasive biomarkers that predict HIV remission after antiretroviral therapy (ART) interruption are urgently needed. Such biomarkers can improve the safety of analytic treatment interruption (ATI) and provide mechanistic insights into the host pathways involved in post-ART HIV control. Here we report plasma glycomic and metabolic signatures of time-to-viral-rebound and probability-of-viral-remission using samples from two independent cohorts. These samples include a large number of post-treatment controllers, a rare population demonstrating sustained virologic suppression after ART-cessation. These signatures remain significant after adjusting for key demographic and clinical confounders. We also report mechanistic links between some of these biomarkers and HIV latency reactivation and/or myeloid inflammation in vitro. Finally, machine learning algorithms, based on selected sets of these biomarkers, predict time-to-viral-rebound with 74% capacity and probability-of-viral-remission with 97.5% capacity. In summary, we report non-invasive plasma biomarkers, with potential functional significance, that predict both the duration and probability of HIV remission after treatment interruption.

Provirus reactivation is impaired in HIV-1 infected individuals on treatment with dasatinib and antiretroviral therapy

The latent viral reservoir formed by HIV-1, mainly in CD4 + T cells, is responsible for the failure of antiretroviral therapy (ART) to achieve a complete elimination of the virus in infected individuals. We previously determined that CD4 + T cells from individuals with chronic myeloid leukemia (CML) on treatment with dasatinib are resistant to HIV-1 infection ex vivo. The main mechanism for this antiviral effect is the preservation of SAMHD1 activity. In this study, we aimed to evaluate the impact of dasatinib on the viral reservoir of HIV-infected individuals with CML who were on simultaneous treatment with ART and dasatinib. Due to the low estimated incidence of HIV-1 infection and CML (1:65,000), three male individuals were recruited in Spain and Germany. These individuals had been on treatment with standard ART and dasatinib for median 1.3 years (IQR 1.3-5.3 years). Reservoir size and composition in PBMCs from these individuals was analyzed in comparison with HIV-infected individuals on triple ART regimen and undetectable viremia. The frequency of latently infected cells was reduced more than 5-fold in these individuals. The reactivation of proviruses from these cells was reduced more than 4-fold and, upon activation, SAMHD1 phosphorylation was reduced 40-fold. Plasma levels of the homeostatic cytokine IL-7 and CD4 effector subpopulations TEM and TEMRA in peripheral blood were also reduced. Therefore, treatment of HIV-infected individuals with dasatinib as adjuvant of ART could disturb the reservoir reactivation and reseeding, which might have a beneficial impact to reduce its size.

How elite controllers and posttreatment controllers inform our search for an HIV-1 cure

A small percentage of people living with HIV-1 can control viral replication without antiretroviral therapy (ART). These patients are called elite controllers (ECs) if they are able to maintain viral suppression without initiating ART and posttreatment controllers (PTCs) if they control HIV replication after ART has been discontinued. Both types of controllers may serve as a model of a functional cure for HIV-1 but the mechanisms responsible for viral control have not been fully elucidated. In this review, we highlight key lessons that have been learned so far in the study of ECs and PTCs and their implications for HIV cure research.

Predicting Post-treatment HIV Remission: Does Size of the Viral Reservoir Matter?

Combination antiretroviral therapy (ART) suppresses human immunodeficiency virus (HIV) replication and improves immune function. However, due to the persistence of long-lived HIV reservoirs, therapy interruption almost inevitably leads to a fast viral rebound. A small percentage of individuals who are able to control HIV replication for extended periods after therapy interruption are of particular interest because they may represent a model of long-term HIV remission without ART. These individuals are characterized by a limited viral reservoir and low reservoir measures can predict post-treatment HIV remission. However, most individuals with a low reservoir still experience fast viral rebound. In this Perspective, we discuss the possible reasons behind this and propose to develop an integral profile, composed of viral and host biomarkers, that could allow the accurate prediction of post-treatment HIV remission. We also propose to incorporate information on the chromatin context of the proviral integration sites into the characterization of the HIV reservoir, as this likely influences the reactivation capacity of latent proviruses and, together with the actual number of intact proviruses, contributes to the replication competence of the reservoir.

Sex Differences in the Treatment of HIV

PURPOSE OF REVIEW

Biological and societal influences are different for men and women leading to different HIV outcomes and related infectious and non-infectious complications. This review evaluates sex differences in the epidemiology and immunological response to HIV and looks at major complications and coinfections, as well as care delivery systems focusing on low- and middle-income countries (LMICs) where most people with HIV live.

RECENT FINDINGS

More women than men access testing and treatment services in LMIC; women are more likely to be virologically suppressed in that environment. There is a growing recognition that the enhanced immunological response to several pathogens including HIV may result in improved outcomes for infectious comorbidities but may result in a greater burden of non-communicable diseases. Men and women have different requirements for HIV care. Attention to these differences may improve outcomes for all.

Initiation of Antiretroviral Therapy during Primary HIV Infection: Effects on the Latent HIV Reservoir, Including on Analytic Treatment Interruptions

Antiretroviral therapy (ART) inhibits HIV replication but does not eradicate the latent reservoir. The previous research suggests that earlier ART initiation provides benefit on limiting reservoir size, but timing and extent of this effect remain unclear. Analytic treatment interruption (ATI) may be used to demonstrate HIV remission, but whether early ART also improves likelihood or duration of even temporary virologic remission is unclear. This review seeks to answer both questions. We performed a systematic review and analysis following Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines and included 21 interventional or observational studies with sufficient HIV reservoir outcomes. We also aggregated reservoir outcomes and transformed data into approximate measurements of total HIV DNA per million peripheral blood mononuclear cells and analyzed the correlation between timing of ART initiation and reservoir size. People living with HIV who initiate ART in primary infection maintain smaller reservoirs on suppressive ART than those who initiate treatment during chronic infection. The reduction of reservoir is most pronounced when ART is started within 2 weeks of HIV acquisition. Across studies, we found a moderately strong association between longer time to ART initiation and reservoir size, which was strongest when measured after 1 year on ART (Pearson's r = 0.69, p = 0.0003). After ATI, larger pre-ATI reservoir size predicts shorter time to viral rebound. Early ART may also facilitate long-term control of viremia. Although achieving sustained HIV remission will require further interventions, initiating ART very early in infection could limit the extent of the reservoir and also lead to post-ATI control in rare cases.

Optimal control modulation of HIV reservoir formation rate by antigen infusion

The Human Immunodeficiency Virus (HIV) infects helper-T cells, and takes advantage of the naturally occurring quiescent phenotype of T cells to persist even under effective treatment conditions. If an infected cell does not produce virus and enters this quiescent state, it forms a natural reservoir that is not targeted by either the existing antiretroviral drugs or the immune system. These quiescent cells intermittently switch to an activated phenotype and begin to produce virus, and are the primary source of viral rebound following treatment cessation. Recent experimental results have shown that, despite this reservoir having a years-long half-life under treatment, most of the cells in the reservoir were infected in a few weeks prior to the start of treatment. This can only be explained by assuming that this reservoir has a short half-life off treatment and a very long half-life on treatment. In this paper, we introduce a novel model of reservoir formation and turnover explaining this difference as a result of antigen-dependent activation. We introduce a second control input through infusion of HIV antigen, mimicking the non-infection pseudovirus (PV) produced by protease inhibitor therapy. This model is coupled to an existing model of immune response to HIV. We fit the parameters of this model to the existing clinical observations of latency. We show that the use of antigen infusion therapy can result in order-of-magnitude decrease in the size of the quiescent reservoir, and that this may provide a way to rapidly stabilize a post-treatment control state in treated HIV infected individuals.

Virologic and Immunologic Features of Simian Immunodeficiency Virus Control Post-ART Interruption in Rhesus Macaques

Antiretroviral therapy (ART) cannot eradicate human immunodeficiency virus (HIV) and a rapid rebound of virus replication follows analytical treatment interruption (ATI) in the vast majority of HIV-infected individuals. Sustained control of HIV replication without ART has been documented in a subset of individuals, defined as posttreatment controllers (PTCs). The key determinants of post-ART viral control remain largely unclear. Here, we identified 7 SIV_mac239-infected rhesus macaques (RMs), defined as PTCs, who started ART 8 weeks postinfection, continued ART for >7 months, and controlled plasma viremia at <10⁴ copies/ml for up to 8 months after ATI and <200 copies/ml at the latest time point. We characterized immunologic and virologic features associated with post-ART SIV control in blood, lymph node (LN), and colorectal (RB) biopsy samples compared to 15 noncontroller (NC) RMs. Before ART initiation, PTCs had higher CD4 T cell counts, lower plasma viremia, and SIV-DNA content in blood and LN compared to NCs, but had similar CD8 T cell function. While levels of intestinal CD4 T cells were similar, PTCs had higher frequencies of Th17 cells. On ART, PTCs had significantly lower levels of residual plasma viremia and SIV-DNA content in blood and tissues. After ATI, SIV-DNA content rapidly increased in NCs, while it remained stable or even decreased in PTCs. Finally, PTCs showed immunologic benefits of viral control after ATI, including higher CD4 T cell levels and reduced immune activation. Overall, lower plasma viremia, reduced cell-associated SIV-DNA, and preserved Th17 homeostasis, including at pre-ART, are the main features associated with sustained viral control after ATI in SIV-infected RMs.IMPORTANCE While effective, antiretroviral therapy is not a cure for HIV infection. Therefore, there is great interest in achieving viral remission in the absence of antiretroviral therapy. Posttreatment controllers represent a small subset of individuals who are able to control HIV after cessation of antiretroviral therapy, but characteristics associated with these individuals have been largely limited to peripheral blood analysis. Here, we identified 7 SIV-infected rhesus macaques that mirrored the human posttreatment controller phenotype and performed immunologic and virologic analysis of blood, lymph node, and colorectal biopsy samples to further understand the characteristics that distinguish them from noncontrollers. Lower viral burden and preservation of immune homeostasis, including intestinal Th17 cells, both before and after ART, were shown to be two major factors associated with the ability to achieve posttreatment control. Overall, these results move the field further toward understanding of important characteristics of viral control in the absence of antiretroviral therapy.

CD8+ T cells in HIV control, cure and prevention

HIV infection can be effectively treated by lifelong administration of combination antiretroviral therapy, but an effective vaccine will likely be required to end the HIV epidemic. Although the majority of current vaccine strategies focus on the induction of neutralizing antibodies, there is substantial evidence that cellular immunity mediated by CD8⁺ T cells can sustain long-term disease-free and transmission-free HIV control and may be harnessed to induce both therapeutic and preventive antiviral effects. In this Review, we discuss the increasing evidence derived from individuals who spontaneously control infection without antiretroviral therapy as well as preclinical immunization studies that provide a clear rationale for renewed efforts to develop a CD8⁺ T cell-based HIV vaccine in conjunction with B cell vaccine efforts. Further, we outline the remaining challenges in translating these findings into viable HIV prevention, treatment and cure strategies.

Recently, antibody-mediated control of HIV infection has received considerable attention. Here, the authors discuss the importance of CD8⁺ T cells in HIV infection and suggest that efforts to develop vaccines that target these cells in conjunction with B cells should be renewed.

On the Road to a HIV Cure: Moving Beyond Berlin and London

The Berlin patient, a famous example for human immunodeficiency virus (HIV) cure, had received a bone marrow transplantation with an HIV resistance mutation. The authors describe his case and others that had shown HIV control, like the Mississippi baby who was started on antiretroviral therapy very early after birth, and posttreatment controllers, like the VISCONTI cohort. Moreover, the authors outline various strategies, oftentimes informed by these individuals, that have been tried in vitro, in animal models, or in human trials, to deplete the latent reservoir, which is considered the basis of HIV persistence and the obstacle to cure.

Learning From the Exceptions: HIV Remission in Post-treatment Controllers

Among the top priorities of the HIV field is the search for therapeutic interventions that can lead to sustained antiretroviral therapy (ART)-free HIV remission. Although the majority of HIV-infected persons will experience rapid viral rebound after ART interruption, there are rare individuals, termed post-treatment controllers (PTCs), who demonstrate sustained virologic suppression for months or years after treatment cessation. These individuals are considered an ideal example of durable HIV control, with direct implications for HIV cure research. However, understanding of the mechanisms behind the capacity of PTCs to control HIV remains incomplete. This is in part due to the scarcity of PTCs identified through any one research center or clinical trial, and in part because of the limited scope of studies that have been performed in these remarkable individuals. In this review, we summarize the results of both clinical and basic research studies of PTCs to date, explore key differences between PTCs and HIV spontaneous controllers, examine potential mechanisms of post-treatment control, and discuss unanswered questions and future research directions in this field.

Predictions of time to HIV viral rebound following ART suspension that incorporate personal biomarkers

Antiretroviral therapy (ART) effectively controls HIV infection, suppressing HIV viral loads. Suspension of therapy is followed by rebound of viral loads to high, pre-therapy levels. However, there is significant heterogeneity in speed of rebound, with some rebounds occurring within days, weeks, or sometimes years. We present a stochastic mathematical model to gain insight into these post-treatment dynamics, specifically characterizing the dynamics of short term viral rebounds (≤ 60 days). Li et al. (2016) report that the size of the expressed HIV reservoir, i.e., cell-associated HIV RNA levels, and drug regimen correlate with the time between ART suspension and viral rebound to detectable levels. We incorporate this information and viral rebound times to parametrize our model. We then investigate insights offered by our model into the underlying dynamics of the latent reservoir. In particular, we refine previous estimates of viral recrudescence after ART interruption by accounting for heterogeneity in infection rebound dynamics, and determine a recrudescence rate of once every 2-4 days. Our parametrized model can be used to aid in design of clinical trials to study viral dynamics following analytic treatment interruption. We show how to derive informative personalized testing frequencies from our model and offer a proof-of-concept example. Our results represent first steps towards a model that can make predictions on a person living with HIV (PLWH)'s rebound time distribution based on biomarkers, and help identify PLWH with long viral rebound delays.

Lessons learned from HIV antiretroviral treatment interruption trials

PURPOSE OF REVIEW

Clinical trials with an antiretroviral therapy (ART) interruption remains indispensable for assessing strategies for ART-free HIV remission. This review highlights the lessons learned from ART interruption studies so far, including the risks to the participants and implications for HIV remission.

RECENT FINDINGS

Historically, analytic HIV treatment interruption (ATI) studies were commonly designed with a prolonged duration of ART interruption and with viral load set point as the primary outcome. For a variety of reasons, including participant risk, recent treatment interruption trials have frequently used time to viral rebound as the primary endpoint and have restarted ART once a predetermined viral load threshold is reached. Through treatment interruption trials, investigators have tested the efficacy of therapeutic and curative strategies that showed promise in preclinical trials, including therapeutic vaccines, latency-reversing agents, and broadly neutralizing antibodies. In most populations, ATI trials have been well tolerated, with few adverse clinical events and no significant changes to the reservoir. Several reservoir predictors of HIV-rebound timing have been reported, with a subset of trials uncovering posttreatment controllers who can maintain HIV remission despite ART discontinuation.

SUMMARY

Treatment interruption trials are a vital tool, but their optimal design remain uncertain and must balance participant risks with scientific rigor. The ability to predict the timing or extent of HIV rebound and identify mechanisms of posttreatment control may accelerate the development of novel therapeutics for sustained HIV remission.

Post-treatment and spontaneous HIV control

PURPOSE OF REVIEW

The aim of the current review is to explore the evidence around virological remission in ART-treated and untreated individuals living with HIV. With increasing evidence and interest in post-treatment control within the HIV-cure field, it is now increasingly important to agree on definitions to allow different 'controller' phenotypes to be clearly distinguished and mechanisms compared.

RECENT FINDINGS

This review explores recent data on potential predictors and mechanisms driving spontaneous and post-treatment control. We explore data on the role of the reservoir as a determinant of control and the challenges associated with its study, including the safety of treatment interruption. We explore options around deriving a consensus on how to define different forms of control and the longer term utility of achieving remission.

SUMMARY

Post-treatment control and remission following treatment interruption are becoming increasingly common measures of intervention efficacy in cure trials. As well as a need to show treatment interruption protocols are well tolerated and acceptable, for these measures to be robust and comparable between studies, clear and consensual definitions need to be agreed.

Clinical trials of antiretroviral treatment interruption in HIV-infected individuals

: Despite the benefits of antiretroviral therapy (ART) for people living with HIV, there has been a long-standing research interest in interrupting ART as a strategy to minimize adverse effects of ART as well as to test interventions aiming to achieve a degree of virological control without ART. We performed a systematic review of HIV clinical studies involving treatment interruption from 2000 to 2017 to describe the differences between treatment interruption in studies that contained and didn't contain an intervention. We assessed differences in monitoring strategies, threshold to restart ART, duration and adverse outcomes of treatment interruption, and factors aimed at minimizing transmission. We found that treatment interruption has been incorporated into 159 clinical studies since 2000 and is increasingly being included in trials to assess the efficacy of interventions to achieve sustained virological remission off ART. Great heterogeneity was noted in immunological, virological and clinical monitoring strategies, as well as in thresholds to recommence ART. Treatment interruption in recent intervention studies were more closely monitored, had more conservative thresholds to restart ART and had a shorter treatment interruption duration, compared with older treatment interruption studies that didn't include an intervention.

Clinical pharmacology in HIV cure research - what impact have we seen?

Introduction: Combined antiretroviral therapy (cART) has transformed an inexorably fatal disease into a chronic pathology, shifting the focus of research from the control of viral replication to the possibility of HIV cure. Areas covered: The present review assesses the principal pharmacological strategies that have been tested for an HIV cure starting from the in vitro proof of concept and the potential rationale of their in vivo applicability. We evaluated the possible pharmacological procedures employed during the early-stage HIV infection and the possibility of cART-free remission. We then analyzed the shock and kill approach from the single compounds in vitro mechanism of action, to the in vivo application of single or combined actions. Finally, we briefly considered the novel immunological branch through the discovery and development of broadly neutralizing antibodies in regard to the current and future in vivo therapeutic strategies aiming to verify the clinical applicability of these compounds. Expert opinion: Despite an incredible effort in HIV research cure, the likelihood of completely eradicating HIV is unreachable within our current knowledge. A better understanding of the mechanism of viral latency and the full characterization of HIV reservoir are crucial for the discovery of new therapeutic targets and novel pharmacological entities.

The Control of HIV After Antiretroviral Medication Pause (CHAMP) Study: Posttreatment Controllers Identified From 14 Clinical Studies

Background

HIV posttreatment controllers are rare individuals who start antiretroviral therapy (ART), but maintain HIV suppression after treatment interruption. The frequency of posttreatment control and posttreatment interruption viral dynamics have not been well characterized.

Methods

Posttreatment controllers were identified from 14 studies and defined as individuals who underwent treatment interruption with viral loads ≤400 copies/mL at two-thirds or more of time points for ≥24 weeks. Viral load and CD4+ cell dynamics were compared between posttreatment controllers and noncontrollers.

Results

Of the 67 posttreatment controllers identified, 38 initiated ART during early HIV infection. Posttreatment controllers were more frequently identified in those treated during early versus chronic infection (13% vs 4%, P < .001). In posttreatment controllers with weekly viral load monitoring, 45% had a peak posttreatment interruption viral load of ≥1000 copies/mL and 33% had a peak viral load ≥10000 copies/mL. Of posttreatment controllers, 55% maintained HIV control for 2 years, with approximately 20% maintaining control for ≥5 years.

Conclusions

Posttreatment control was more commonly identified amongst early treated individuals, frequently characterized by early transient viral rebound and heterogeneous durability of HIV remission. These results may provide mechanistic insights and have implications for the design of trials aimed at achieving HIV remission.

HIV control: Is getting there the same as staying there?

In this brief review and perspective, we address the question of whether the immune responses that bring about immune control of acute HIV infection are the same as, or distinct from, those that maintain long-term viral suppression once control of viremia has been achieved. To this end, we describe the natural history of elite and post-treatment control, noting the lack of data regarding what happens acutely. We review the evidence suggesting that the two clinical phenotypes may differ in terms of the mechanisms required to achieve and maintain control, as well as the level of inflammation that persists once a steady state is achieved. We then describe the evidence from longitudinal studies of controllers who fail and studies of biologic sex (male versus female), age (children versus adults), and simian immunodeficiency virus (SIV) (pathogenic/experimental versus nonpathogenic/natural infection). Collectively, these studies demonstrate that the battle between the inflammatory and anti-inflammatory pathways during acute infection has long-term consequences, both for the degree to which control is maintained and the health of the individual. Potent and stringent control of HIV may be required acutely, but once control is established, the chronic inflammatory response can be detrimental. Interventional approaches designed to bring about HIV cure and/or remission should be nuanced accordingly.

CD8+ lymphocyte control of SIV infection during antiretroviral therapy

CD8⁺ lymphocytes play an important role in suppressing in vivo viral replication in HIV infection. However, both the extent to which and the mechanisms by which CD8⁺ lymphocytes contribute to viral control are not completely understood. A recent experiment depleted CD8⁺ lymphocytes in simian immunodeficiency virus (SIV)-infected rhesus macaques (RMs) on antiretroviral treatment (ART) to study the role of CD8⁺ lymphocytes. CD8⁺ lymphocytes depletion resulted in temporary plasma viremia in all studied RMs. Viral control was restored when CD8⁺ lymphocytes repopulated. We developed a viral dynamic model to fit the viral load (VL) data from the CD8 depletion experiment. We explicitly modeled the dynamics of the latent reservoir and the SIV-specific effector cell population including their exhaustion and their potential cytolytic and noncytolytic functions. We found that the latent reservoir significantly contributes to the size of the peak VL after CD8 depletion, while drug efficacy plays a lesser role. Our model suggests that the overall CD8⁺ lymphocyte cytolytic killing rate is dynamically changing depending on the levels of antigen-induced effector cell activation and exhaustion. Based on estimated parameters, our model suggests that before ART or without ART the overall CD8 cytolytic killing rate is small due to exhaustion. However, after the start of ART, the overall CD8 cytolytic killing rate increases due to an expansion of SIV-specific CD8 effector cells. Further, we estimate that the cytolytic killing rate can be significantly larger than the cytopathic death rate in some animals during the second phase of ART-induced viral decay. Lastly, our model provides a new explanation for the puzzling findings by Klatt et al. and Wong et al. that CD8 depletion done immediately before ART has no noticeable effect on the first phase viral decay slope seen after ART initiation Overall, by incorporating effector cells and their exhaustion, our model can explain the effects of CD8 depletion on VL during ART, reveals a detailed dynamic role of CD8⁺ lymphocytes in controlling viral infection, and provides a unified explanation for CD8 depletion experimental data.

CD8⁺ lymphocytes play an important role in suppressing in vivo viral replication in HIV infection. However, both the extent to which and the mechanisms by which CD8⁺ lymphocytes contribute to viral control are not completely understood. By mathematically modeling data from a recent CD8 depletion experiment done in antiretroviral (ART) treated animals, our results suggest that the overall CD8⁺ lymphocyte cytolytic killing rate is dynamically changing depending on the levels of antigen-induced effector cell activation and exhaustion, i.e. before ART or without ART the overall CD8 cytolytic killing rate is small due to exhaustion. However, after the start of ART, the overall CD8 cytolytic killing rate increases due to an expansion of SIV-specific CD8 effector cells. By incorporating effector cells and their exhaustion, our model explains the effects on viral load of CD8 depletion done before ART or during ART, reveals a detailed dynamic role of CD8⁺ lymphocytes in controlling viral infection, and provides a unified explanation for CD8 depletion experimental data.

HIV-1 proviral landscapes distinguish posttreatment controllers from noncontrollers

HIV posttreatment controllers (PTCs) represent a natural model of sustained HIV remission, but they are rare and little is known about their viral reservoir. We obtained 1,450 proviral sequences after near-full-length amplification for 10 PTCs and 16 posttreatment noncontrollers (NCs). Before treatment interruption, the median intact and total reservoir size in PTCs was 7-fold lower than in NCs, but the proportion of intact, defective, and total clonally expanded proviral genomes was not significantly different between the 2 groups. Quantification of total but not intact proviral genome copies predicted sustained HIV remission as 81% of NCs, but none of the PTCs had a total proviral genome greater than 4 copies per million peripheral blood mononuclear cells (PBMCs). The results highlight the restricted intact and defective HIV reservoir in PTCs and suggest that total proviral genome burden could act as the first biomarker for identifying PTCs. Total and defective but not intact proviral copy numbers correlated with levels of cell-associated HIV RNA, activated NK cell percentages, and both HIV-specific CD4+ and CD8+ responses. These results support the concept that defective HIV genomes can lead to viral antigen production and interact with both the innate and adaptive immune systems.

Inhibition of p38 MAPK in combination with ART reduces SIV-induced immune activation and provides additional protection from immune system deterioration

Differences in immune activation were identified as the most significant difference between AIDS-susceptible and resistant species. p38 MAPK, activated in HIV infection, is key to induction of interferon-stimulated genes and cytokine-mediated inflammation and is associated with some of the pathology produced by HIV or SIV infection in AIDS-susceptible primates. As small molecule p38 MAPK inhibitors are being tested in human trials for inflammatory diseases, we evaluated the effects of treating SIV-infected macaques with the p38 MAPK inhibitor PH-797804 in conjunction with ART. PH-797804 had no side effects, did not impact negatively the antiviral immune response and, used alone, had no significant effect on levels of immune activation and did not reduced the viremia. When administered with ART, it significantly reduced numerous immune activation markers compared to ART alone. CD38⁺/HLA-DR⁺ and Ki-67⁺ T-cell percentages in blood, lymph node and rectal CD4⁺ and CD8⁺ T cells, PD-1 expression in CD8⁺ T cells and plasma levels of IFNα, IFNγ, TNFα, IL-6, IP-10, sCD163 and C-reactive protein were all significantly reduced. Significant preservation of CD4⁺, CD4⁺ central memory, CD4⁺/IL-22⁺ and CD4⁺/IL-17⁺ T-cell percentages and improvement of Th17/Treg ratio in blood and rectal mucosa were also observed. Importantly, the addition of PH-797804 to ART initiated during chronic SIV infection reduced immune activation and restored immune system parameters to the levels observed when ART was initiated on week 1 after infection. After ART interruption, viremia rebounded in a similar fashion in all groups, regardless of when ART was initiated. We concluded that the inhibitor PH-797804 significantly reduced, even if did not normalized, the immune activation parameters evaluated during ART treatment, improved preservation of critical populations of the immune system targeted by SIV, and increased the efficacy of ART treatment initiated in chronic infection to levels similar to those observed when initiated in acute infection but did not affect positively or negatively viral reservoirs.

The hallmark of Human Immunodeficiency Virus and Simian Immunodeficiency Virus infection in disease-susceptible species is the progressive decline of the CD4+ T cell population and heightened immune activation, which by itself can contribute to CD4+ T-cell death. The cellular pathway regulated by p38 MAPK, which is activated in HIV and SIV infection, can contribute significantly to immune activation. We tested in SIV-infected macaques a p38 MAPK inhibitor in combination with anti-retroviral therapy. This drug is already being evaluated in humans for treatment of immune activation associated with other diseases. We found that, when combined with antiretroviral therapy, the inhibitor PH-797804 significantly reduced a few parameters of SIV-induced immune activation and improved preservation of critical populations of the immune system targeted by SIV, but did not modulate viral reservoirs. Importantly, the addition of the inhibitor to anti-retroviral therapy during the chronic phase of the infection, which is the time when most HIV-infected individuals initiate treatment, permitted a more significant preservation of the immune system compared to antiretroviral therapy alone that was similar to that observed when anti-retroviral therapy was initiated in the acute phase of the infection, which rarely occurs in HIV infection.

Sex Differences in HIV Infection: Mystique Versus Machismo

Biological sex is a determinant of both susceptibility to and pathogenesis of multiple infections, including HIV. These differences have effects on the spectrum of HIV disease from acquisition to eradication, with diverse mechanisms including distinct chromosomal complements, variation in microbiota composition, hormonal effects on transcriptional profiles, and expression of different immunoregulatory elements. With a comparative biology approach, these sex differences can be used to highlight protective and detrimental immune activation pathways, to identify strategies for effective prevention, treatment, and curative interventions.

Mathematical Analysis of Viral Replication Dynamics and Antiviral Treatment Strategies: From Basic Models to Age-Based Multi-Scale Modeling

Viral infectious diseases are a global health concern, as is evident by recent outbreaks of the middle east respiratory syndrome, Ebola virus disease, and re-emerging zika, dengue, and chikungunya fevers. Viral epidemics are a socio-economic burden that causes short- and long-term costs for disease diagnosis and treatment as well as a loss in productivity by absenteeism. These outbreaks and their socio-economic costs underline the necessity for a precise analysis of virus-host interactions, which would help to understand disease mechanisms and to develop therapeutic interventions. The combination of quantitative measurements and dynamic mathematical modeling has increased our understanding of the within-host infection dynamics and has led to important insights into viral pathogenesis, transmission, and disease progression. Furthermore, virus-host models helped to identify drug targets, to predict the treatment duration to achieve cure, and to reduce treatment costs. In this article, we review important achievements made by mathematical modeling of viral kinetics on the extracellular, intracellular, and multi-scale level for Human Immunodeficiency Virus, Hepatitis C Virus, Influenza A Virus, Ebola Virus, Dengue Virus, and Zika Virus. Herein, we focus on basic mathematical models on the population scale (so-called target cell-limited models), detailed models regarding the most important steps in the viral life cycle, and the combination of both. For this purpose, we review how mathematical modeling of viral dynamics helped to understand the virus-host interactions and disease progression or clearance. Additionally, we review different types and effects of therapeutic strategies and how mathematical modeling has been used to predict new treatment regimens.

Sex Differences in HIV Infection

PURPOSE OF REVIEW

This review will outline the multilevel effects of biological sex on HIV acquisition, pathogenesis, treatment response, and prospects for cure. Potential mechanisms will be discussed along with future research directions.

RECENT FINDINGS

HIV acquisition risk is modified by sex hormones and the vaginal microbiome, with the latter acting through both inflammation and local metabolism of pre-exposure prophylaxis drugs. Female sex associates with enhanced risk for non-AIDS morbidities including cardiovascular and cerebrovascular disease, suggesting different inflammatory profiles in men and women. Data from research on HIV cure points to sex differences in viral reservoir dynamics and a direct role for sex hormones in latency maintenance. Biological sex remains an important variable in determining the risk of HIV infection and subsequent viral pathogenesis, and emerging data suggest sex differences relevant to curative interventions. Recruitment of women in HIV clinical research is a pathway to both optimize care for women and to identify novel therapeutics for use in both men and women.

Post-treatment controllers after treatment interruption in chronically HIV-infected patients

OBJECTIVE

Control HIV replication requires continuous combined antiretroviral therapy (cART) as discontinuation of cART results in a rapid viral rebound. However, a few individuals exist who took cART for several years and did not show the expected viral rebound after treatment cessation. Most post-treatment controllers (PTCs) are early treated individuals. We report three cases who started cART during chronic infection.

DESIGN

Patients were treated and monitored according to Italian guidelines. For the description of cases, the percentage of CD8CD38HLA*DR cells, CD8CD38HLA*DR cells, major histocompatibility complex genotyping, total HIV-DNA and plasma levels of anti-retroviral (ARV) drugs were performed.

RESULTS

Patients started therapy during chronic infection. Patient 26636 started her first ARV drug two years after diagnosis and patients 93016 and 50293 started cART with high viral loads and low CD4 cell counts. Time without cART was 13, 11 and 1.5 years, respectively. None presented any of the protective class I HLA alleles and patient 93016 has the HLA-B*35 allele that appears to be enriched in PTCs. Patients 93016 and 50293 had very low levels of CD8CD38HLA*DR cells (<5%) much lower than those of patient 26636 (27%). T-cell-associated HIV-DNA was 3.78, 3.48 and 3.13 log copies/10 CD4, respectively.

CONCLUSION

Patients like ours may advance our understanding of the characteristics for which individuals may be more likely to achieve ART-free remissions. Furthermore, our patients are among the few so far described who started cART during chronic infection extending the hope that a functional cure is possible even in this setting.

Wake me up before you go: a strategy to reduce the latent HIV reservoir

In the quest to eliminate or reduce the HIV reservoir, shock and kill strategies require the combined administration of a latency reversing agent (LRA) to reactivate the latent reservoir and an intervention to boost effector functions to clear this reservoir. Both parts of this strategy are quite inefficient when LRAs are administered to HIV-infected individuals on suppressive ART for several years, possibly due to low levels of induced antigen expression, negative impact of LRAs on clearance mechanisms, and very low number of effective cytotoxic T cells (CTLs). Here we provide rationale for an approach that would require only the administration of an LRA at the time of ART initiation to significantly reduce the HIV reservoir. The advantage of this strategy is an efficient reactivation of the latent HIV reservoir when high numbers of HIV-specific CD8+ T cells are present. This strategy may also potentiate more effective CTL responses and the establishment of a longer period of immune surveillance. This “window of opportunity” has been validated in silico , can be tested in preclinical non-human primate (NHP) models and translated rapidly in the clinic.

Barriers to HIV Cure

Since the beginning of the epidemic, more than 70 million people have been infected with human immunodeficiency virus (HIV) and about 38 million have died from acquired immune deficiency syndrome (AIDS)-related illnesses. While the discovery of highly active antiretroviral therapy (HAART) in the mid 90's has saved millions of lives, a complete eradication of HIV is still not possible as HIV can persist for decades in a small reservoir of latently infected cells. Once reactivated, these latently infected cells can actively produce viral particles. Recent studies suggest that several sanctuaries exist within infected individuals where HIV can remain undetected by the immune system. These cellular, anatomical and microanatomical viral reservoirs represent a major obstacle for the eradication of HIV. Here we review recent findings on potential sanctuaries of HIV and address potential avenues to overcome these immunological barriers.

BISTABILITY ANALYSIS OF AN HIV MODEL WITH IMMUNE RESPONSE

Some HIV-infected patients (the so-called post-treatment controllers) can control the virus after cessation of antiretroviral therapy. A small fraction of patients can even naturally maintain undetectable viral load without therapy (they are called elite controllers). The immune response may play an important role in viral control in these patients. In this paper, we analyze a within-host model including immune response to study the virus dynamics in HIV-infected patients. We derived two threshold values for the immune cell proliferation parameter. Below the lower immune proliferation rate, the model has a stable immune-free steady state, which predicts that patients have a high viral load. Above the higher immune proliferation rate, the model has a stable low infected steady state, which indicates that patients are under elite control. Between the two immune thresholds, the model exhibits the dynamic behavior of bistability, which suggests that patients either undergo viral rebound after treatment termination or achieve the post-treatment control. These results may explain the different virus dynamics in HIV-infected patients.

A randomized controlled safety/efficacy trial of therapeutic vaccination in HIV-infected individuals who initiated antiretroviral therapy early in infection

Despite substantial clinical benefits, complete eradication of HIV has not been possible using antiretroviral therapy (ART) alone. Strategies that can either eliminate persistent viral reservoirs or boost host immunity to prevent rebound of virus from these reservoirs after discontinuation of ART are needed; one possibility is therapeutic vaccination. We report the results of a randomized, placebo-controlled trial of a therapeutic vaccine regimen in patients in whom ART was initiated during the early stage of HIV infection and whose immune system was anticipated to be relatively intact. The objectives of our study were to determine whether the vaccine was safe and could induce an immune response that would maintain suppression of plasma viremia after discontinuation of ART. Vaccinations were well tolerated with no serious adverse events but produced only modest augmentation of existing HIV-specific CD4+ T cell responses, with little augmentation of CD8+ T cell responses. Compared with placebo, the vaccination regimen had no significant effect on the kinetics or magnitude of viral rebound after interruption of ART and no impact on the size of the HIV reservoir in the CD4+ T cell compartment. Notably, 26% of subjects in the placebo arm exhibited sustained suppression of viremia (<400 copies/ml) after treatment interruption, a rate of spontaneous suppression higher than previously reported. Our findings regarding the degree and kinetics of plasma viral rebound after ART interruption have potentially important implications for the design of future trials testing interventions aimed at achieving ART-free control of HIV infection.

Human Immunodeficiency Virus Playing Hide-and-Seek: Understanding the TFH Cell Reservoir and Proposing Strategies to Overcome the Follicle Sanctuary

Human immunodeficiency virus (HIV) infects millions of people worldwide, and new cases continue to emerge. Once infected, the virus cannot be cleared by the immune system and causes acquired immunodeficiency syndrome. Combination antiretroviral therapeutic regimen effectively suppresses viral replication and halts disease progression. The treatment, however, does not eliminate the virus-infected cells, and interruption of treatment inevitably leads to viral rebound. The rebound virus originates from a group of virus-infected cells referred to as the cellular reservoir of HIV. Identifying and eliminating the HIV reservoir will prevent viral rebound and cure HIV infection. In this review, we focus on a recently discovered HIV reservoir in a subset of CD4⁺ T cells called the follicular helper T (T_FH) cells. We describe the potential mechanisms for the emergence of reservoir in T_FH cells, and the strategies to target and eliminate this viral reservoir.