cART Interruption Research Articles

Oral Combinational Antiretroviral Treatment in HIV-1 Infected Humanized Mice.

The human immunodeficiency virus (HIV-1) pandemic continues to spread unabated worldwide, and currently, there is no vaccine available against HIV. Although combinational antiretroviral therapy (cART) has been successful in suppressing viral replication, it cannot completely eradicate the reservoir from HIV-infected individuals. A safe and effective cure strategy for HIV infection will require multipronged methods, and therefore the advancements of animal models for HIV-1 infection are pivotal for the development of HIV cure research. Humanized mice recapitulate key features of HIV-1 infection. The humanized mouse model can be infected by HIV-1 and viral replication can be controlled with cART regimens. Moreover, cART interruption results in a prompt viral rebound in humanized mice. However, administration of cART to the animal can be ineffective, difficult, or toxic, and many clinically relevant cART regimens are unable to be optimally utilized. Along with being potentially unsafe for researchers, administration of cART by a commonly used intensive daily injection procedure induces stress by physical restraint of the animal. The novel oral cART method to treat HIV-1 infected humanized mice described in this article resulted in suppression of viremia below the detection level, increased rate of CD4+ restoration, and improved overall health in HIV-1 infected humanized mice.

Oral Combinational Antiretroviral Treatment in HIV-1 Infected Humanized Mice

The human immunodeficiency virus (HIV-1) pandemic continues to spread unabated worldwide, and currently, there is no vaccine available against HIV. Although combinational antiretroviral therapy (cART) has been successful in suppressing viral replication, it cannot completely eradicate the reservoir from HIV-infected individuals. A safe and effective cure strategy for HIV infection will require multipronged methods, and therefore the advancements of animal models for HIV-1 infection are pivotal for the development of HIV cure research. Humanized mice recapitulate key features of HIV-1 infection. The humanized mouse model can be infected by HIV-1 and viral replication can be controlled with cART regimens. Moreover, cART interruption results in a prompt viral rebound in humanized mice. However, administration of cART to the animal can be ineffective, difficult, or toxic, and many clinically relevant cART regimens are unable to be optimally utilized. Along with being potentially unsafe for researchers, administration of cART by a commonly used intensive daily injection procedure induces stress by physical restraint of the animal. The novel oral cART method to treat HIV-1 infected humanized mice described in this article resulted in suppression of viremia below the detection level, increased rate of CD4+ restoration, and improved overall health in HIV-1 infected humanized mice.

Past HIV-1 Medications and the Current Status of Combined Antiretroviral Therapy Options for HIV-1 Patients.

Combined antiretroviral therapy (cART) is treatment with a combination of several antiretroviral drugs that block multiple stages in the virus replication cycle. An estimated 60% of the 38 million HIV-1 patients globally receive some form of cART. The benefits of cART for controlling HIV-1 replication, transmission, and infection rates have led to its universal recommendation. Implementation has caused a substantial reduction in morbidity and mortality of persons living with HIV-1/AIDS (PLWHA). More specifically, standard cART has provided controlled, undetectable levels of viremia, high treatment efficacy, reduction in pill burden, and an improved lifestyle in HIV-1 patients overall. However, HIV-1 patients living with AIDS (HPLA) generally show high viral loads upon cART interruption. Latently infected resting CD4+ T cells remain a major barrier to curing infected patients on long-term cART. There is a critical need for more effective compounds and therapies that not only potently reactivate latently infected cells, but also lead to the death of these reactivated cells. Efforts are ongoing to better control ongoing viral propagation, including the identification of appropriate animal models that best mimic HIV-1 pathogenesis, before proceeding with clinical trials. Limited toxicity profiles, improved drug penetration to certain tissues, and extended-release formulations are needed to cover gaps in existing HIV-1 treatment options. This review will cover past, current, and new cART strategies recently approved or in ongoing development.

The Current Status of Latency Reversing Agents for HIV-1 Remission.

Combinatory antiretroviral therapy (cART) reduces human immunodeficiency virus type 1 (HIV-1) replication but is not curative because cART interruption almost invariably leads to a rapid rebound of viremia due to the persistence of stable HIV-1-infected cellular reservoirs. These reservoirs are mainly composed of CD4+ T cells harboring replication-competent latent proviruses. A broadly explored approach to reduce the HIV-1 reservoir size, the shock and kill strategy, consists of reactivating HIV-1 gene expression from the latently infected cellular reservoirs (the shock), followed by killing of the virus-producing infected cells (the kill). Based on improved understanding of the multiple molecular mechanisms controlling HIV-1 latency, distinct classes of latency reversing agents (LRAs) have been studied for their efficiency to reactivate viral gene expression in in vitro and ex vivo cell models. Here, we provide an up-to-date review of these different mechanistic classes of LRAs and discuss optimizations of the shock strategy by combining several LRAs simultaneously or sequentially.

The challenging of HIV care 1 year after of coronavirus disease 2019 pandemic: results from a Brazilian cohort.

The challenging of HIV care 1 year after of coronavirus disease 2019 pandemic: results from a Brazilian cohort.

Platelets in HIV: A Guardian of Host Defence or Transient Reservoir of the Virus?

The immune and inflammatory responses of platelets to human immunodeficiency virus 1 (HIV-1) and its envelope proteins are of great significance to both the treatment of the infection, and to the comorbidities related to systemic inflammation. Platelets can interact with the HIV-1 virus itself, or with viral membrane proteins, or with dysregulated inflammatory molecules in circulation, ensuing from HIV-1 infection. Platelets can facilitate the inhibition of HIV-1 infection via endogenously-produced inhibitors of HIV-1 replication, or the virus can temporarily hide from the immune system inside platelets, whereby platelets act as HIV-1 reservoirs. Platelets are therefore both guardians of the host defence system, and transient reservoirs of the virus. Such reservoirs may be of particular significance during combination antiretroviral therapy (cART) interruption, as it may drive viral persistence, and result in significant implications for treatment. Both HIV-1 envelope proteins and circulating inflammatory molecules can also initiate platelet complex formation with immune cells and erythrocytes. Complex formation cause platelet hypercoagulation and may lead to an increased thrombotic risk. Ultimately, HIV-1 infection can initiate platelet depletion and thrombocytopenia. Because of their relatively short lifespan, platelets are important signalling entities, and could be targeted more directly during HIV-1 infection and cART.

Extracellular vesicle-mediated intercellular communication in HIV-1 infection and its role in the reservoir maintenance

HIV-1 infection is efficiently controlled by combination anti-retroviral therapy (cART). However, despite preventing disease progression, cART does not eradicate virus infection which persists in a latent form for an individual’s lifetime. The latent reservoir comprises memory CD4+ T lymphocytes, macrophages, and dendritic cells; however, for the most part, the reservoir is generated by virus entry into activated CD4+ T lymphocytes committed to return to a resting state, even though resting CD4+ T lymphocytes can be latently infected as well. The HIV-1 reservoir is not recognized by the immune system, is quite stable, and has the potential to re-seed systemic viremia upon cART interruption. Viral rebound can occur even after a long period of cART interruption. This event is most likely a consequence of the extended half-life of the HIV-1 reservoir, the maintenance of which is not clearly understood. Several recent studies have identified extracellular vesicles (EVs) as a driving force contributing to HIV-1 reservoir preservation. In this review, we discuss recent findings in the field of EV/HIV-1 interplay, and then propose a mechanism through which EVs may contribute to HIV-1 persistence despite cART. Understanding the basis of the HIV-1 reservoir maintenance continues to be a matter of great relevance in view of the limitations of current strategies aimed at HIV-1 eradication.

Predictors of SIV recrudescence following antiretroviral treatment interruption.

There is currently a need for proxy measures of the HIV rebound competent reservoir (RCR) that can predict viral rebound after combined antiretroviral treatment (cART) interruption. In this study, macaques infected with a barcoded SIVmac239 virus received cART beginning between 4- and 27 days post-infection, leading to the establishment of different levels of viral dissemination and persistence. Later treatment initiation led to higher SIV DNA levels maintained during treatment, which was significantly associated with an increased frequency of SIV reactivation and production of progeny capable of causing rebound viremia following treatment interruption. However, a 100-fold increase in SIV DNA in PBMCs was associated with only a 2-fold increase in the frequency of reactivation. These data suggest that the RCR can be established soon after infection, and that a large fraction of persistent viral DNA that accumulates after this time makes relatively little contribution to viral rebound.

Recombinant Human Interleukin-15 and Anti-PD-L1 Combination Therapy Expands a CXCR3+PD1-/low CD8 T-Cell Subset in Simian Immunodeficiency Virus-Infected Rhesus Macaques.

The PD1/PD-L1 pathway contributes to the pathogenesis of human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) infection, and blockade of this pathway may have potential to restore immune function and promote viral control or elimination. In this study, we combined a checkpoint inhibitor anti-PD-L1 (Avelumab) and recombinant human interleukin-15 (rhIL-15) in SIV-infected rhesus macaques (RM). The rhIL-15 was administered as continuous infusion in 2 cycles of 10 days in the context of weekly administration of anti-PD-L1 (Avelumab) in SIV-infected RM receiving combination antiretroviral therapy (cART). Safety, immunological parameters, and viral loads were monitored during the study. Administration of rhIL-15/anti-PD-L1 was safe and well tolerated. Treatment resulted in transient increases in proliferating (Ki67+) natural killer and CD8 T cells. In addition, treatment expanded a CXCR3+PD1-/low CD8 T-cell subset with the ability to secrete cytokines. Despite these effects, no changes in plasma viremia were observed after cART interruption. Expansion of the CXCR3+PD1-/low CD8 T-cell subset with functional capacity and potential to traffic to sites of viral reservoirs in SIV-infected rhesus macaques had no demonstrable effect on plasma viremia after cART interruption.

Genital reservoir: a barrier to functional cure?

HIV functional cure requires the elimination or a major reduction of HIV reservoir pool including male and female genital HIV reservoirs. A comprehensive understanding of HIV dynamics in these compartments is mandatory. Data from chronically HIV-infected therapy-naïve individuals or fully suppressed on combined antiretroviral therapy (cART) or undergoing ART interruptions are now available. Using paired blood/genital samples, HIV-RNA/DNA quantification and sequencing provide new insights on HIV dynamics in genital reservoirs. In the absence of cART, HIV shedding in semen and cervicovaginal secretions is frequent, resulting most likely from passive transfer of HIV strains that originates from bloodborne virions or infected blood cells. Partial and intermittent HIV compartmentalization in the male and female genital tracts can occur not only in chronically infected ART-naïve individuals but also when cART is used to prevent active blood replication. This transient autonomous HIV replication in the genital reservoir in a few individuals originates from recent transfer of virions or infected blood cells. cART interruption studies showed that blood and genital quasispecies are closely related, in agreement with a passive transfer. Altogether these data suggest that HIV genital reservoirs seem not to be a significant barrier to achieve HIV cure.

Dendritic cell immunotherapy followed by cART interruption during HIV-1 infection induces plasma protein markers of cellular immunity and neutrophil recruitment.

ObjectivesTo characterize the host response to dendritic cell-based immunotherapy and subsequent combined antiretroviral therapy (cART) interruption in HIV-1-infected individuals at the plasma protein level.DesignAn autologous dendritic cell (DC) therapeutic vaccine was administered to HIV-infected individuals, stable on cART. The effect of vaccination was evaluated at the plasma protein level during the period preceding cART interruption, during analytical therapy interruption and at viral reactivation. Healthy controls and post-exposure prophylactically treated healthy individuals were included as controls.MethodsPlasma marker (‘analyte’) levels including cytokines, chemokines, growth factors, and hormones were measured in trial participants and control plasma samples using a multiplex immunoassay. Analyte levels were analysed using principle component analysis, cluster analysis and limma. Blood neutrophil counts were analysed using linear regression.ResultsPlasma analyte levels of HIV-infected individuals are markedly different from those of healthy controls and HIV-negative individuals receiving post-exposure prophylaxis. Viral reactivation following cART interruption also affects multiple analytes, but cART interruption itself only has only a minor effect. We find that Thyroxine-Binding Globulin (TBG) levels and late-stage neutrophil numbers correlate with the time off cART after DC vaccination. Furthermore, analysis shows that cART alters several regulators of blood glucose levels, including C-peptide, chromogranin-A and leptin. HIV reactivation is associated with the upregulation of CXCR3 ligands.ConclusionsChronic HIV infection leads to a change in multiple plasma analyte levels, as does virus reactivation after cART interruption. Furthermore, we find evidence for the involvement of TBG and neutrophils in the response to DC-vaccination in the setting of HIV-infection.

Efficient activation of latent HIV reservoir in human memory T cells by depletion of regulatory T cells in humanized mice in vivo

Abstract Regulatory T (Treg) cells play an important role in modulating immune activation and human immunodeficiency virus type 1 (HIV-1) infection. However, the role of Treg cells in HIV-1 latency establishment or maintenance in vivo remains unknown because of the lack of a robust model. We have established a humanized mouse model that supports long-term stable HIV-1 replication. When treated with combination antiretroviral therapy (cART), HIV-1 infection was stably suppressed to undetectable levels. Upon cART interruption, HIV-1 replication rebounded rapidly to pre-treatment levels. Interestingly, HIV-1 viral replication was significantly increased upon Treg cell depletion under effective cART. The HIV-1 reactivation during cART was mainly through increased gene expression from T cells. The rebound viruses during cART did not acquire drug resistance mutations. We found that most activated HIV-1 reservoir target cells were CD4 memory T cells in all lymphoid organs. These findings demonstrate that Treg cells suppress HIV-1 replication and its reactivation from latently infected T cells in vivo. Treg cell depletion provides an efficient way to reverse latency and reactivate HIV-1 reservoirs in vivo.

Loss of immune homeostasis dictates SHIV rebound after stem-cell transplantation.

The conditioning regimen used as part of the Berlin patient's hematopoietic cell transplant likely contributed to his eradication of HIV infection. We studied the impact of conditioning in simian-human immunodeficiency virus-infected (SHIV-infected) macaques suppressed by combination antiretroviral therapy (cART). The conditioning regimen resulted in a dramatic, but incomplete depletion of CD4+ and CD8+ T cells and CD20+ B cells, increased T cell activation and exhaustion, and a significant loss of SHIV-specific Abs. The disrupted T cell homeostasis and markers of microbial translocation positively correlated with an increased viral rebound after cART interruption. Quantitative viral outgrowth and Tat/rev-induced limiting dilution assays showed that the size of the latent SHIV reservoir did not correlate with viral rebound. These findings identify perturbations of the immune system as a mechanism for the failure of autologous transplantation to eradicate HIV. Thus, transplantation strategies may be improved by incorporating immune modulators to prevent disrupted homeostasis, and gene therapy to protect transplanted cells.

Kinetics of Myeloid-Derived Suppressor Cell Frequency and Function during Simian Immunodeficiency Virus Infection, Combination Antiretroviral Therapy, and Treatment Interruption.

During chronic lentiviral infection, poor clinical outcomes correlate both with systemic inflammation and poor proliferative ability of HIV-specific T cells; however, the connection between the two is not clear. Myeloid-derived suppressor cells (MDSC), which expand during states of elevated circulating inflammatory cytokines, may link the systemic inflammation and poor T cell function characteristic of lentiviral infections. Although MDSC are partially characterized in HIV and SIV infection, questions remain regarding their persistence, activity, and clinical significance. We monitored MDSC frequency and function in SIV-infected rhesus macaques. Low MDSC frequency was observed prior to SIV infection. Post-SIV infection, MDSC were elevated in acute infection and persisted during 7 mo of combination antiretroviral drug therapy (cART). After cART interruption, we observed MDSC expansion of surprising magnitude, the majority being granulocytic MDSC. At all stages of infection, granulocytic MDSC suppressed CD4+ and CD8+ T cell proliferation in response to polyclonal or SIV-specific stimulation. In addition, MDSC frequency correlated significantly with circulating inflammatory cytokines. Acute and post-cART levels of viremia were similar, however, the levels of inflammatory cytokines and MDSC were more pronounced post-cART. Expanded MDSC during SIV infection, especially during the post-cART inflammatory cytokine surge, likely limit cellular responses to infection. As many HIV curative strategies require cART interruption to determine efficacy, our work suggests treatment interruption-induced MDSC may especially undermine the effectiveness of such strategies. MDSC depletion may enhance T cell responses to lentiviral infection and the effectiveness of curative approaches.

Failure to achieve immunological recovery in HIV-infected patients with clinical and virological success after 10 years of combined ART: role of treatment course.

We assessed factors, including treatment course, associated with failure to obtain a 10 year immunological response after starting first-generation PI-containing combined ART (cART). In the prospective COPILOTE cohort of HIV-infected patients started on a first-generation PI-containing regimen in 1997-99, the impact of cART history on the failure to achieve immunological response measured at 10 years was assessed by multivariate logistic regression models in the 399 patients with clinical and virological success of cART. Failure of CD4 response (CD4 >500/mm3) was associated with age ≥40 years at baseline (P < 0.001), CD4 cell counts ≤500/mm3 at month 4 (P = 0.016) or month 12 (P < 0.001) and ≥3 months of cART interruption (P = 0.016). Factors associated with failure to achieve complete immunological response (CD4 >500/mm3 and CD4:CD8 ratio >1) were CD4:CD8 ratio ≤0.8 at month 8 (P < 0.001) or month 12 (P < 0.001), ≥3 months of cumulative cART interruption (P = 0.011), ≥3 antiretroviral regimens (P = 0.009) and ≤4 treatment lines (P = 0.015). Baseline CD4 and CD4:CD8 ratio were not predictors of the 10 year immunological outcomes. In this therapeutic cohort of patients starting first-generation PI-containing cART in 1997-99, poor initial immunological response had a negative impact on 10 year CD4 and CD4 plus CD4:CD8 ratio response, despite prolonged virological success. Lack of treatment interruption may improve long-term immunological outcome in HIV infection.

HIV-1 Reservoir Dynamics after Vaccination and Antiretroviral Therapy Interruption Are Associated with Dendritic Cell Vaccine-Induced T Cell Responses.

HIV-1-specific immune responses induced by a dendritic cell (DC)-based therapeutic vaccine might have some effect on the viral reservoir. Patients on combination antiretroviral therapy (cART) were randomized to receive DCs pulsed with autologous HIV-1 (n = 24) (DC-HIV-1) or nonpulsed DCs (n = 12) (DC-control). We measured the levels of total and integrated HIV-1 DNA in CD4 T cells isolated from these patients at 6 time points: before any cART; before the first cART interruption, which was at 56 weeks before the first immunization to isolate virus for pulsing DCs; before and after vaccinations (VAC1 and VAC2); and at weeks 12 and 48 after the second cART interruption. The vaccinations did not influence HIV-1 DNA levels in vaccinated subjects. After the cART interruption at week 12 postvaccination, while total HIV-1 DNA increased significantly in both arms, integrated HIV-1 DNA did not change in vaccinees (mean of 1.8 log10 to 1.9 copies/10(6) CD4 T cells, P = 0.22) and did increase in controls (mean of 1.8 log10 to 2.1 copies/10(6) CD4 T cells, P = 0.02) (P = 0.03 for the difference between groups). However, this lack of increase of integrated HIV-1 DNA observed in the DC-HIV-1 group was transient, and at week 48 after cART interruption, no differences were observed between the groups. The HIV-1-specific T cell responses at the VAC2 time point were inversely correlated with the total and integrated HIV-1 DNA levels after cART interruption in vaccinees (r [Pearson's correlation coefficient] = -0.69, P = 0.002, and r = -0.82, P < 0.0001, respectively). No correlations were found in controls. HIV-1-specific T cell immune responses elicited by DC therapeutic vaccines drive changes in HIV-1 DNA after vaccination and cART interruption. (This study has been registered at ClinicalTrials.gov under registration no. NCT00402142.) There is an intense interest in developing strategies to target HIV-1 reservoirs as they create barriers to curing the disease. The development of therapeutic vaccines aimed at enhancing immune-mediated clearance of virus-producing cells is of high priority. Few therapeutic vaccine clinical trials have investigated the role of therapeutic vaccines as a strategy to safely eliminate or control viral reservoirs. We recently reported that a dendritic cell-based therapeutic vaccine was able to significantly decrease the viral set point in vaccinated patients, with a concomitant increase in HIV-1-specific T cell responses. The HIV-1-specific T cell immune responses elicited by this therapeutic dendritic cell vaccine drove changes in the viral reservoir after vaccinations and significantly delayed the replenishment of integrated HIV-1 DNA after cART interruption. These data help in understanding how an immunization could shift the virus-host balance and are instrumental for better design of strategies to reach a functional cure of HIV-1 infection.

Establishment and Replenishment of the Viral Reservoir in Perinatally HIV-1-infected Children Initiating Very Early Antiretroviral Therapy.

Combination antiretroviral therapy (cART) generally suppresses the replication of the human immunodeficiency virus type 1 (HIV-1) but does not cure the infection, because proviruses persist in stable latent reservoirs. It has been proposed that low-level proviral reservoirs might predict longer virologic control after discontinuation of treatment. Our objective was to evaluate the impact of very early initiation of cART and temporary treatment interruption on the size of the latent HIV-1 reservoir in vertically infected children. This retrospective study included 23 perinatally HIV-1-infected children who initiated very early treatment within 12 weeks after birth (n = 14), or early treatment between week 12 and 1 year (n = 9). We measured the proviral reservoir (CD4(+) T-cell-associated HIV-1 DNA) in blood samples collected beyond the first year of sustained virologic suppression. There is a strong positive correlation between the time to initiation of cART and the size of the proviral reservoir. Children who initiated cART within the first 12 weeks of life showed a proviral reservoir 6-fold smaller than children initiating cART beyond this time (P < .01). Rapid virologic control after initiation of cART also limits the size of the viral reservoir. However, patients who underwent transient treatment interruptions showed a dramatic increase in the size of the viral reservoir after discontinuation. Initiation of cART during the first 12 weeks of life in perinatally HIV-1-infected children limits the size of the viral reservoir. Treatment interruptions should be undertaken with caution, as they might lead to fast and irreversible replenishment of the viral reservoir.

Can HIV Be Cured and Should We Try?

An estimated 35.0 million persons live with HIV; 2.1 million new infections occurred and 1.5 million persons died of HIV in 2013 (World Health Organization, http://www.who.int/hiv/data/epi_core_dec2014.png?ua=1). Despite effective combination antiretroviral therapy (cART), less than one-quarter of patients can access these life-prolonging medications; and despite its effectiveness, cART does not normalize life expectancy, as premature aging, metabolic complications and chronic inflammation complicate HIV therapy. HIV is incurable due to the presence of a latent viral reservoir. During the life cycle of the virus, HIV integrates into the host DNA. A subset of integrated HIV provirus remains transcriptionally silent, producing neither viral proteins nor viral progeny, until reactivation by various physiologic stimuli. This latency of HIV allows some infected cells to escape immune detection and elimination, and these latently infected cells constitute the viral reservoir. The latent viral reservoir allows viral rebound within weeks of interruption of cART, 1,2 where the magnitude of viral replication approaches that present pre-therapy. Although it was once thought that viral rebound occurred universally following therapy interruption, several recent reports challenge that paradigm. The “Berlin patient” successfully cleared HIV after two allogeneic transplants from a donor with homozygous CCR5Δ32 mutation,3 and he has not rebounded HIV after nearly seven years. This case likely represents a cure from HIV; yet other cases have been described where HIV rebound has been attenuated, or delayed. The “Mississippi” baby was a perinatally HIV-infected infant who initiated cART within hours of birth, and when interrupted eighteen months later, viremia remained undetectable for nearly two years.4 The Harvard BMT cases underwent allogeneic BMT, developed undetectable HIV DNA, yet rebounded viremia within only eight months after cART discontinuation.5 Together these cases demonstrate that control of viremia in the absence of cART is possible, if not durable.4 The VISCONTI cohort of 14 HIV-infected adults who initiated antiretroviral therapy during acute infection, and in whom high level rebound viremia had not occurred several years after cessation of therapy,6 similarly demonstrated that viral rebound following cART interruption can be attenuated. These cases have reinvigorated research toward finding a cure for HIV, which certainly will require an exceptional investment of time, talent and resources. Thus it is prudent to question whether such resources would be better devoted to more proximate needs with proven results (such as supplying cART to those without access to it, or supplying pre/post exposure prophylaxis to reduce the rate of new infections).

Effects of different antigenic stimuli on thymic function and interleukin-7/CD127 system in patients with chronic HIV infection.

We tested if an increase in immune activation and a decrease in CD4⁺ T cells induced by different antigenic stimuli could be associated with changes in the thymic function and the interleukin (IL)-7/CD127 system. Twenty-six HIV-infected patients under combined antiretroviral therapy (cART) were randomized to receive, during 12 months, a complete immunization schedule (7 vaccines and 15 doses) or placebo. Thereafter, cART was interrupted during 6 months. Changes in the thymic function and the IL-7/CD127 system after 3 different antigenic stimuli (vaccines, episodes of low-level intermittent viremia before cART interruption, or viral load rebound after cART interruption) were assessed. During the period on cART, neither vaccines nor low-level viremia influenced thymic function or IL-7/CD127 system parameters. By analyzing the cohort as a whole while on cART, a significant improvement was observed in the thymic function as measured by an increase in the thymic volume (P = 0.024), T-cell receptor excision circle-bearing cells (P = 0.012), and naive CD4⁺ and CD8⁺ T cells (P = 0.069 both). No significant changes were observed in the IL-7/CD127 system. After cART interruption, a decrease in T-cell receptor excision circles (P < 0.001) and naive CD8⁺ T cells (P < 0.001), an increase in IL-7 and expression of CD127 on naive and memory CD4⁺ T cells (P = 0.028, P = 0.088, and P = 0.04, respectively), and a significant decrease in CD127 on naive and memory CD8⁺ T cells (P = 0.01, P = 0.006, respectively) were observed. Low-level transient antigenic stimuli during cART were not associated with changes in the thymic function or the IL-7/CD127 system. Conversely, viral load rebound very early after cART interruption influenced the thymic function and the IL-7/CD127 system. Clinical Trials.gov number NCT00329251.

Lack of Detectable HIV-1 Molecular Evolution during Suppressive Antiretroviral Therapy

A better understanding of changes in HIV-1 population genetics with combination antiretroviral therapy (cART) is critical for designing eradication strategies. We therefore analyzed HIV-1 genetic variation and divergence in patients' plasma before cART, during suppression on cART, and after viral rebound. Single-genome sequences of plasma HIV-1 RNA were obtained from HIV-1 infected patients prior to cART (N = 14), during suppression on cART (N = 14) and/or after viral rebound following interruption of cART (N = 5). Intra-patient population diversity was measured by average pairwise difference (APD). Population structure was assessed by phylogenetic analyses and a test for panmixia. Measurements of intra-population diversity revealed no significant loss of overall genetic variation in patients treated for up to 15 years with cART. A test for panmixia, however, showed significant changes in population structure in 2/10 patients after short-term cART (<1 year) and in 7/10 patients after long-term cART (1–15 years). The changes consisted of diverse sets of viral variants prior to cART shifting to populations containing one or more genetically uniform subpopulations during cART. Despite these significant changes in population structure, rebound virus after long-term cART had little divergence from pretherapy virus, implicating long-lived cells infected before cART as the source for rebound virus. The appearance of genetically uniform virus populations and the lack of divergence after prolonged cART and cART interruption provide strong evidence that HIV-1 persists in long-lived cells infected before cART was initiated, that some of these infected cells may be capable of proliferation, and that on-going cycles of viral replication are not evident.