Antiretroviral therapy in HIV-infected elite controllers: impact on gut immunology, microbial translocation, and biomarkers of serious non-AIDS conditions

Increased biomarkers of cardiovascular risk in HIV-1 viremic controllers and low persistent inflammation in elite controllers and art-suppressed individuals

HIV controllers (HICs) are models of HIV functional cure, although some studies have shown persistent inflammation and increased rates of atherosclerosis in HICs. Since immune activation/inflammation contributes to the pathogenesis of cardiovascular diseases (CVD), we evaluated clinical data and inflammation markers in HIV-1 viremic controllers (VC), elite controllers (EC), and control groups (HIV positive individuals with virological suppression by antiretroviral therapy—cART; HIV negative individuals—HIVneg) to assess whether they presented elevated levels of inflammation markers also associated with CVD. We observed the highest frequencies of activated CD8⁺ T cells in VCs, while EC and cART groups presented similar but slightly altered frequencies of this marker when compared to the HIVneg group. Regarding platelet activation, both HICs groups presented higher expression of P-selectin in platelets when compared to control groups. Monocyte subset analyses revealed lower frequencies of classical monocytes and increased frequencies of non-classical and intermediate monocytes among cART individuals and in EC when compared to HIV negative individuals, but none of the differences were significant. For VC, however, significant decreases in frequencies of classical monocytes and increases in the frequency of intermediate monocytes were observed in comparison to HIV negative individuals. The frequency of monocytes expressing tissue factor was similar among the groups on all subsets. In terms of plasma markers, VC had higher levels of many inflammatory markers, while EC had higher levels of VCAM-1 and ICAM-1 compared to control groups. Our data showed that VCs display increased levels of inflammation markers that have been associated with CVD risk. Meanwhile, ECs show signals of lower but persistent inflammation, comparable to the cART group, indicating the potential benefits of alternative therapies to decrease inflammation in this group.

Gut microbiome signatures linked to HIV-1 reservoir size and viremia control

BACKGROUND

The potential role of the gut microbiome as a predictor of immune-mediated HIV-1 control in the absence of antiretroviral therapy (ART) is still unknown. In the BCN02 clinical trial, which combined the MVA.HIVconsv immunogen with the latency-reversing agent romidepsin in early-ART treated HIV-1 infected individuals, 23% (3/13) of participants showed sustained low-levels of plasma viremia during 32 weeks of a monitored ART pause (MAP). Here, we present a multi-omics analysis to identify compositional and functional gut microbiome patterns associated with HIV-1 control in the BCN02 trial.

RESULTS

Viremic controllers during the MAP (controllers) exhibited higher Bacteroidales/Clostridiales ratio and lower microbial gene richness before vaccination and throughout the study intervention when compared to non-controllers. Longitudinal assessment indicated that the gut microbiome of controllers was enriched in pro-inflammatory bacteria and depleted in butyrate-producing bacteria and methanogenic archaea. Functional profiling also showed that metabolic pathways related to fatty acid and lipid biosynthesis were significantly increased in controllers. Fecal metaproteome analyses confirmed that baseline functional differences were mainly driven by Clostridiales. Participants with high baseline Bacteroidales/Clostridiales ratio had increased pre-existing immune activation-related transcripts. The Bacteroidales/Clostridiales ratio as well as host immune-activation signatures inversely correlated with HIV-1 reservoir size.

CONCLUSIONS

The present proof-of-concept study suggests the Bacteroidales/Clostridiales ratio as a novel gut microbiome signature associated with HIV-1 reservoir size and immune-mediated viral control after ART interruption. Video abstract.

Antiretroviral Therapy Reduces T-cell Activation and Immune Exhaustion Markers in Human Immunodeficiency Virus Controllers

BACKGROUND

Despite low plasma human immunodeficiency virus (HIV) RNA, HIV controllers have evidence of viral replication and elevated inflammation. We assessed the effect of antiretroviral therapy (ART) on HIV suppression, immune activation, and quality of life (QoL).

METHODS

A5308 was a prospective, open-label study of rilpivirine/emtricitabine/tenofovir disoproxil fumarate in ART-naive HIV controllers (N = 35), defined as having HIV RNA <500 copies/mL for ≥12 months. The primary outcome measured change in %CD38+HLA-DR+ CD8+ T cells. Residual plasma viremia was measured using the integrase single-copy assay. QoL was measured using the EQ-5D questionnaire. Outcomes were evaluated using repeated measures general estimating equations models.

RESULTS

Before ART, HIV controllers with undetectable residual viremia <0.6 HIV-1 RNA copies/mL had higher CD4+ counts and lower levels of T-cell activation than those with detectable residual viremia. ART use was effective in further increasing the proportion of individuals with undetectable residual viremia (pre-ART vs after 24-48 weeks of ART: 19% vs 94%, P < .001). Significant declines were observed in the %CD38+HLA-DR+CD8+ T cells at 24-48 (-4.0%, P = .001) and 72-96 (-7.2%, P < .001) weeks after ART initiation. ART use resulted in decreases of several cellular markers of immune exhaustion and in a modest but significant improvement in self-reported QoL. There were no significant changes in CD4+ counts or HIV DNA.

CONCLUSIONS

ART in HIV controllers reduces T-cell activation and improves markers of immune exhaustion. These results support the possible clinical benefits of ART in this population.

Antiretroviral Treatment for HIV Elite Controllers?

In most HIV-infected persons, the natural history of untreated infection is one of sustained viremia, progressive CD4 T cell depletion with resultant morbidity and mortality. The advent of effective combination antiretroviral therapy (ART) that controls HIV replication has altered this landscape dramatically. Yet a rare population of HIV-infected persons-elite controllers (EC)-can control HIV replication such that plasma levels of virus are "undetectable" without ART. The EC phenotype is heterogeneous, with some subjects durably controlling the virus-persistent elite controllers-and some eventually losing viral control-transient elite controllers. Overall, EC tend to have robust HIV-specific T cell responses and in some cases, mainly in transient elite controllers, elevated activation and inflammation indices that diminish with ART suggesting that endogenous defenses against this persistent pathogen come at the cost of heightened activation/inflammation. A limited data set suggests that cardiovascular disease risk as well as the occur-rence of other morbid events may be greater in the overall EC population than in treated HIV infection. ART in EC decreases activation indices but does not appear to increase circulating CD4 T cell numbers nor do we know if it alters clinical outcomes. Thus, it is difficult to recommend or discourage a decision to start ART in the EC population but the authors lean toward treatment particularly in those EC whose activation indices are high and those who are progressively losing circulating CD4 T cell numbers. Biomarkers that can reliably predict loss of virologic control and immune failure are needed.

Immune effects of Lactobacillus casei Shirota in treated HIV-infected patients with poor CD4+ T-cell recovery

BACKGROUND

HIV infection leads to depletion of intestinal CD4+ T cells, mucosal barrier dysfunction, increased gut permeability and microbial translocation even among patients on suppressive ART. Previous studies suggest probiotics may help restore intestinal function.

METHODS

In this double-blind, placebo-controlled pilot study, we enrolled HIV-infected patients on suppressive ART with poor CD4+ recovery to address the effect of daily oral use of Lactobacillus casei Shirota (LcS) on CD4+ T-cell count and CD4+/CD8+ ratio at 6 and 12 weeks after treatment initiation; immune activation and intestinal microbiome composition were addressed as secondary outcomes.

RESULTS

From January 2015 to July 2016, 48 patients were randomized (1 : 1) to active intervention or placebo. Groups had comparable demographic and clinical characteristics; only CD4+ T-cell nadir was statistically different between groups. All participants were virologically suppressed under ART. At week 6, the increment in CD4+ T-cell count was 17 cells/μl [interquartile range (IQR) -33 to 74] in the active intervention arm and 4 cells/μl (IQR -43 to 51) in the placebo arm (P = 0.291); at week 12, the change in CD4+ T-cell count was 8 cells//μl (IQR -30 to 70) in the active arm and 10 cells//μl (IQR -50 to 33) among participants allocated to placebo (P = 0.495). Median change in CD4+/CD8+ ratio at week 6 compared with baseline was 0 (IQR -0.04 to 0.05) in the active intervention arm and -0.01 in the placebo arm (IQR -0.06 to 0.03; P = 0.671). At week 12, the change in CD4+/CD8+ ratio was higher in the active product group compared with placebo (respectively 0.07 and 0.01), but this difference failed to reach statistical significance (P = 0.171). We found no significant effects of LcS on immune activation markers, CD4+ and CD8+ subpopulations, sCD14 levels or NK cells at week 12. Finally, we found no statistically significant differences between groups in the change of enteric microbiome at week 12.

CONCLUSION

In this pilot study, we found no statistically significant effect of LcS probiotic on CD4+ T-cell counts, CD4+/CD8+ ratio, immune activation or intestinal microbiome among HIV-infected patients on suppressive ART with poor CD4+ recovery.

HIV controllers: to treat or not to treat? Is that the right question?

The term HIV controller refers to the small proportion of individuals infected with HIV who can spontaneously control viraemia to maintain very low viral loads. One major unresolved question is whether HIV controllers should receive antiretroviral therapy, given that international guidelines recommend treatment for all individuals who are infected with HIV. Differences in the definitions of a controller (in terms of the viral-load cutoff and the duration of viral control) and contrasting reports on CD4 T-cell decline, chronic immune activation, the cardiovascular risk, and loss of viral control in controllers have prevented the development of a consensus view.

The microbiome and HIV persistence: implications for viral remission and cure

PURPOSE OF REVIEW

This article discusses the interaction between HIV infection, the gut microbiome, inflammation and immune activation, and HIV reservoirs, along with interventions to target the microbiome and their implications for HIV remission and cure.

RECENT FINDINGS

Most studies show that HIV-infected adults have a gut microbiome associated with decreased bacterial richness and diversity, and associated systemic inflammation and immune activation. A unique set of individuals, elite controllers, who spontaneously control HIV replication, have a similar microbiome to HIV-uninfected individuals. Conversely, exposure to maternal HIV in infants was shown to alter the gut microbiome, even in infants who escaped perinatal infection. Emerging research highlights the importance of the metabolomics and metaproteomics of the gut microbiome, which may have relevance for HIV remission and cure. Together, these studies illustrate the complexity of the relationship between HIV infection, the gut microbiome, and its systemic effects.

SUMMARY

Understanding the association of HIV with the microbiome, metabolome, and metaproteome may lead to novel therapies to decrease inflammation and immune activation, and impact HIV reservoir size and vaccine responses. Further research in this area is important to inform HIV remission and cure treatments.

Deciphering natural control of HIV-1: A valuable strategy to achieve antiretroviral therapy termination

Antiretroviral therapy (ART) has dramatically reduced HIV-1-associated morbidity and mortality, and has transformed HIV-1 infection into a manageable chronic condition by suppressing viral replication. However, despite recent patient care improvements, ART still fails to cure HIV-1 infection due to the inability to counteract immune defects and metabolic disturbances that are associated with residual inflammation alongside viral persistence. Life-long drug administration also results in multiple side-effects in patients including lipodystrophy and insulin resistance. Thus, it is critical to find new ways to reduce the length of treatment and facilitate the termination of ART, for example by boosting protective immunity. The rare ability of some individuals to naturally control HIV-1 infection despite residual inflammation could be exploited to identify molecular mechanisms involved in host protection that may function as potential therapeutic targets. In this review, we highlight evidence illustrating the molecular and metabolic advantages of HIV-1 controllers over ART treated patients that contribute to the maintenance of effective antiviral immunity.

Stimulation of PBMC and Monocyte-Derived Macrophages via Toll-Like Receptor Activates Innate Immune Pathways in HIV-Infected Patients on Virally Suppressive Combination Antiretroviral Therapy

In HIV-infected, combination antiretroviral therapy (cART)-treated patients, immune activation and microbial translocation persist and associate with inadequate CD4 recovery and morbidity/mortality. We analyzed whether alterations in the toll-like receptor (TLR) pathway could be responsible for the immune hyperactivation seen in these patients. PBMC/monocyte-derived macrophages (MDMs) of 28 HIV+ untreated and 35 cART-treated patients with HIV-RNA < 40 cp/mL [20 Full Responders (FRs): CD4 ≥ 350; 15 Immunological Non-Responders (INRs): CD4 < 350], as well as of 16 healthy controls were stimulated with a panel of TLR agonists. We measured: CD4/CD8/CD14/CD38/HLA-DR/Ki67/AnnexinV/CD69/TLR4/8 (Flow Cytometry); PBMC expression of 84 TLR pathway genes (qPCR); PBMC/MDM cytokine release (Multiplex); and plasma lipopolysaccharide (LPS)/sCD14 (LAL/ELISA). PBMC/MDM from cART patients responded weakly to LPS stimulation but released high amounts of pro-inflammatory cytokines. MDM from these patients were characterized by a reduced expression of HLA-DR+ MDM and failed to expand activated HLA-DR+ CD38+ T-lymphocytes. PBMC/MDM from cART patients responded more robustly to ssRNA stimulation; this resulted in a significant expansion of activated CD38 + CD8 and the release of amounts of pro-inflammatory cytokines comparable to those seen in untreated viremic patients. Despite greater constitutive TLR pathway gene expression, PBMC from INRs seemed to upregulate only type I IFN genes following TLR stimulation, whereas PBMC from full responders showed a broader response. Systemic exposure to microbial antigens drives immune activation during cART by triggering TLRs. Bacterial stimulation modifies MDM function/pro-inflammatory profile in cART patients without affecting T-lymphocytes; this suggests translocating bacteria as selective stimulus to chronic innate activation during cART. High constitutive TLR activation is seen in patients lacking CD4 recovery, suggesting an exhausted immune milieu, anergic to further antigen encounters.

Gut barrier structure, mucosal immunity and intestinal microbiota in the pathogenesis and treatment of HIV infection

Over the past 10 years, extensive work has been carried out in the field of microbial translocation in HIV infection, ranging from studies on its clinical significance to investigations on its pathogenic features. In the present work, we review the most recent findings on this phenomenon, focusing on the predictive role of microbial translocation in HIV-related morbidity and mortality, the mechanisms by which it arises and potential therapeutic approaches. From a clinical perspective, current work has shown that markers of microbial translocation may be useful in predicting clinical events in untreated HIV infection, while conflicting data exist on their role in cART-experienced subjects, possibly due to the inclusion of extremely varied patient populations in cohort studies. Results from studies addressing the pathogenesis of microbial translocation have improved our knowledge of the damage of the gastrointestinal epithelial barrier occurring in HIV infection. However, the extent to which mucosal impairment translates directly to increased gastrointestinal permeability remains an open issue. In this respect, novel work has established a role for IL-17 and IL-22-secreting T cell populations in limiting microbial translocation and systemic T-cell activation/inflammation, thus representing a possible target of immune-therapeutic interventions shown to be promising in the animal model. Further, recent reports have not only confirmed the presence of a dysbiotic intestinal community in the course of HIV infection but have also shown that it may be linked to mucosal damage, microbial translocation and peripheral immune activation. Importantly, technical advances have also shed light on the metabolic activity of gut microbes, highlighting the need for novel therapeutic approaches to correct the function, as well as the composition, of the gastrointestinal microbiota.

Post-treatment control: a functional cure for HIV

Controlled plasma viral load to levels below limits of detection off antiretroviral therapy (ART), referred to as a functional cure, or remission, is an aspiration for people living with HIV avoiding the need for daily ART while preserving immunological function. For the majority of people, stopping suppressive ART is associated with virological rebound. Spontaneous viral control is reported among rare individuals in the absence of ART. More recently, strategic use of transient ART, initiated close to the time of HIV acquisition, has been associated with a phenotype of viral control after stopping therapy termed post-treatment control. We explore the phenotype of post-treatment viral control, potential underlying mechanisms, and how this area of research can inform HIV cure research.