sCD14 is not a bona-fide biomarker of microbial translocation in HIV-1-infected Africans living in Belgium

Immune activation and inflammation in lactating women on combination antiretroviral therapy: role of gut dysfunction and gut microbiota imbalance

Introduction

Combination antiretroviral therapy (cART) effectively controls HIV; however, chronic low-level viremia and gut microbiota dysbiosis remain significant drivers of gut and systemic inflammation. In this study, we explored the relationship between gut microbiota composition, intestinal inflammation, microbial translocation, and systemic inflammation in women on cART in Sub-Saharan Africa.

Methods

We conducted a study in HIV-infected and HIV-uninfected lactating women followed up at 6 weeks and 6 months postpartum in Harare, Zimbabwe. We used 16S ribosomal Ribonucleic Acid (rRNA) sequencing and MesoScale Discovery V-Plex assays to examine the gut microbiome and to quantify plasma inflammatory biomarkers, respectively. In addition, we measured fecal calprotectin, plasma lipopolysaccharide-binding protein (LBP), and soluble cluster of differentiation 14 (sCD14) by enzyme-linked immunosorbent assay to assess gut inflammation, microbial translocation, and monocyte/macrophage activation.

Results

A group of 77 lactating women were studied, of which 35% were HIV-infected. Fecal calprotectin levels were similar by HIV status at both follow-up time points. In the HIV-infected group at 6 weeks postpartum, fecal calprotectin was elevated: median (interquartile range) [158.1 µg/g (75.3-230.2)] in women who had CD4+ T-lymphocyte counts <350 cells/µL compared with those with ≥350 cells/µL [21.1 µg/g (0-58.4)], p = 0.032. Plasma sCD14 levels were significantly higher in the HIV-infected group at both 6 weeks and 6 months postpartum, p < 0.001. Plasma LBP levels were similar, but higher levels were observed in HIV-infected women with elevated fecal calprotectin. We found significant correlations between fecal calprotectin, LBP, and sCD14 with proinflammatory cytokines. Gut microbial alpha diversity was not affected by HIV status and was not affected by use of antibiotic prophylaxis. HIV significantly affected microbial beta diversity, and significant differences in microbial composition were noted. The genera Slackia and Collinsella were relatively more abundant in the HIV-infected group, whereas a lower relative abundance of Clostriduim sensu_stricto_1 was observed. Our study also found correlations between gut microbial taxa abundance and systemic inflammatory biomarkers.

Discussion and conclusion

HIV-infected lactating women had increased immune activation and increased microbial translocation associated with increased gut inflammation. We identified correlations between the gut inflammation and microbial composition, microbial translocation, and systemic inflammation. The interplay of these parameters might affect the health of this vulnerable population.

Coordination of inflammatory responses in children with perinatally-acquired HIV infection

OBJECTIVE

We investigated dynamics of inflammatory biomarkers in children with perinatally-acquired HIV (PHIV) who started antiretrovirals at age <3 years and achieved sustained virologic control (HIV plasma RNA<400 copies/mL).

DESIGN

This was a retrospective analysis of inflammatory biomarkers in children enrolled in a randomized trial of early (<3 years of age) PI-based versus NNRTI-based regimens (P1060), who achieved sustained virologic control and participated in a neurodevelopmental follow-up study (P1104 s) between ages 5-11 years.

METHODS

We measured 20 inflammatory biomarkers using ELISA or chemiluminescence at onset of sustained virologic control (Tc) and at P1104 s entry (Te).

RESULTS

The 213 participants had median ages of 1.2, 1.9, and 7.0 years at antiretroviral initiation, Tc, and Te, respectively, with 138 on PI-based and 74 on NNRTI-based regimens at Tc. Eighteen markers decreased and two increased from Tc to Te (Te-Tc). Biomarker subsets, particularly cytokines, the chemokine IP-10, and adhesion molecules sICAM-1 and sVCAM-1, correlated at Tc, Te, and Te-Tc. At Tc, higher biomarker levels were associated with younger age, female sex, HIV plasma RNA ≥750,000 copies/mL, lower nadir CD4+%, lower nadir weight z-scores, and NNRTI-based treatment. Greater Te-Tc biomarker declines were associated with younger age, male sex, higher Tc biomarker levels, lower nadir CD4+%, and NNRTI-based treatment. Duration of controlled viremia and nadir height Z-scores showed mixed associations.

CONCLUSIONS

Biomarker expression showed substantial coordination. Most markers decreased after virologic control. Demographic and clinical variables associated with biomarker patterns were identified. Mechanistic studies of these biomarker patterns are needed to inform interventions to control inflammation.

Plasma biomarker factors associated with neurodevelopmental outcomes in children with perinatal HIV infection and controlled viremia

OBJECTIVE

We examined relationships between plasma biomarkers and neurodevelopment in children from sub-Saharan Africa with perinatal HIV (PHIV) with controlled viremia on antiretroviral therapy (ART).

DESIGN

Longitudinal retrospective cohort study of children with controlled blood HIV replication.

METHODS

Children (N = 213; 57% girls) started ART at less than 3 years of age, had neurodevelopmental assessments (cognition, attention/impulsivity, motor proficiency, global executive functions) at 5-11 years, and achieved controlled viremia (HIV-1 RNA <400 copies/ml for ≥9 months before initial assessment). Twenty-three plasma biomarkers were measured at onset of controlled viremia, week 0 (first neurodevelopmental assessment), and week 48 (second neurodevelopmental assessment). Factor analysis was conducted at each time point. Multivariable linear regressions assessed associations between factors and neurodevelopmental scores.

RESULTS

Median age at week 0 was 7.0 years. Eighteen biomarkers loaded on six factors: a (L-10, IFNγ, IFNα2, IL-1β, IL-6, IP-10, TNFα); B (sCD163, sICAM-1, sVCAM-1, CRP); C (sE-selectin, sP-selectin); D [MIP-1β, vascular endothelial growth factor (VEGF)-A]; E (sCD14, CRP); and F (CX3CL1, MCP-1). Higher factor B scores were consistently associated with worse cognition and attention/impulsivity, and higher factor D scores with better attention/impulsivity.

CONCLUSION

These results suggest a detrimental effect of increased endothelial cell activation (sICAM-1, sVCAM-1) and monocyte/macrophage scavenger function (sCD163) and a beneficial effect of increased CCR5 ligand and HIV entry blocker MIP-1β and angiogenesis stimulant-VEGF concentrations on the neurodevelopment of children with PHIV. The model that emerges is of vascular inflammation leading to neurodevelopmental deficits. The role of persistent HIV replication in the central nervous system also needs to be further explored.

Dysregulation of IL-17/IL-22 Effector Functions in Blood and Gut Mucosal Gamma Delta T Cells Correlates With Increase in Circulating Leaky Gut and Inflammatory Markers During cART-Treated Chronic SIV Infection in Macaques

HIV-associated inflammation has been implicated in the premature aging and increased risk of age-associated comorbidities in cART-treated individuals. However, the immune mechanisms underlying the chronic inflammatory state of cART-suppressed HIV infection remain unclear. Here, we investigated the role of γδT cells, a group of innate IL-17 producing T lymphocytes, in the development of systemic inflammation and leaky gut phenotype during cART-suppressed SIV infection of macaques. Plasma levels of inflammatory mediators, intestinal epithelial barrier disruption (IEBD) and microbial translocation (MT) biomarkers, and Th1/Th17-type cytokine functions were longitudinally assessed in blood and gut mucosa of SIV-infected, cART-suppressed macaques. Among the various gut mucosal IL-17/IL-22-producing T lymphocyte subsets including Th17, γδT, CD161+ CD8+ T, and MAIT cells, a specific decline in the Vδ2 subset of γδT cells and impaired IL-17/IL-22 production in γδT cells significantly correlated with the subsequent increase in plasma IEBD/MT markers (IFABP, LPS-binding protein, and sCD14) and pro-inflammatory cytokines (IL-6, IL-1β, IP10, etc.) despite continued viral suppression during long-term cART. Further, the plasma inflammatory cytokine signature during long-term cART was distinct from acute SIV infection and resembled the inflammatory cytokine profile of uninfected aging (inflammaging) macaques. Overall, our data suggest that during cART-suppressed chronic SIV infection, dysregulation of IL-17/IL-22 cytokine effector functions and decline of Vδ2 γδT cell subsets may contribute to gut epithelial barrier disruption and development of a distinct plasma inflammatory signature characteristic of inflammaging. Our results advance the current understanding of the impact of chronic HIV/SIV infection on γδT cell functions and demonstrate that in the setting of long-term cART, the loss of epithelial barrier-protective functions of Vδ2 T cells and ensuing IEBD/MT occurs before the hallmark expansion of Vδ1 subsets and skewed Vδ2/Vδ1 ratio. Thus, our work suggests that novel therapeutic approaches toward restoring IL-17/IL-22 cytokine functions of intestinal Vδ2 T cells may be beneficial in preserving gut epithelial barrier function and reducing chronic inflammation in HIV-infected individuals.

Biomarkers of Cellular Stress Do Not Associate with sCD14 in Progressive HIV and SIV Infections in Vivo

Background

Microbial translocation occurs after damage to the structural and/or immunological barrier of the gastrointestinal (GI) tract into circulation. Microbial components that trans-locate from the lumen of the GI tract directly stimulate the immune system and contribute to inflammation. When microbial translocation becomes chronic, the inflammation has detrimental consequences. Given that microbial translocation is an important phenomenon in many diseases, defining biomarkers that reliably reflect microbial translocation is critical. Measurement of systemic microbial products is difficult since: 1) robust assays to measure microbial antigens simultaneously are lacking; 2) confounding factors influence assays used to detect microbial products; and 3) biological clearance mechanisms limit their detection in circulation. Thus, host proteins produced in response to microbial stimulation are used as surrogates for microbial translocation; however, many of these proteins are also produced in response to host proteins expressed by dying cells.

Methods

We measured plasma levels of biomarkers associated with GI tract damage, immune responses to microbial products, and cell-death in people living with HIV before and after antiretroviral administration, and in macaque nonhuman primates before and after SIV infection.

Results

Proteins secreted during cellular stress (receptor for advanced glycation endproducts-RAGE and high motility group box 1-HMGB1), which can induce sCD14 production in vitro and in vivo, do not associate with elevated levels of biomarkers associated with microbial translocation in progressively HIV-infected individuals and SIV-infected NHPs.

Conclusions

Bystander cell death and generalized inflammation do not contribute to elevated levels of sCD14 observed in HIV/SIV-infected individuals.

The effect of pyridostigmine on small intestinal bacterial overgrowth (SIBO) and plasma inflammatory biomarkers in HIV-associated autonomic neuropathies

Small intestinal bacterial overgrowth (SIBO) is common among patients with HIV-associated autonomic neuropathies (HIV-AN) and may be associated with increased bacterial translocation and elevated plasma inflammatory biomarkers. Pyridostigmine is an acetylcholinesterase inhibitor which has been used to augment autonomic signaling. We sought preliminary evidence as to whether pyridostigmine could improve proximal gastrointestinal motility, reduce SIBO, reduce plasma sCD14 (a marker of macrophage activation and indirect measure of translocation), and reduce the inflammatory cytokines IL-6 and TNFα in patients with HIV-AN. Fifteen participants with well-controlled HIV, HIV-AN, and SIBO were treated with 8 weeks of pyridostigmine (30 mg PO TID). Glucose breath testing for SIBO, gastric emptying studies (GES) to assess motility, plasma sCD14, IL-6, and TNFα, and gastrointestinal autonomic symptoms were compared before and after treatment. Thirteen participants (87%) experienced an improvement in SIBO following pyridostigmine treatment; with an average improvement of 50% (p = 0.016). There was no change in gastrointestinal motility; however, only two participants met GES criteria for gastroparesis at baseline. TNFα and sCD14 levels declined by 12% (p = 0.004) and 19% (p = 0.015), respectively; there was no significant change in IL-6 or gastrointestinal symptoms. Pyridostigmine may ameliorate SIBO and reduce levels of sCD14 and TNFα in patients with HIV-AN. Larger placebo-controlled studies are needed to definitively delineate how HIV-AN affects gastrointestinal motility, SIBO, and systemic inflammation in HIV, and whether treatment improves clinical outcomes.

Vagal dysfunction and small intestinal bacterial overgrowth: novel pathways to chronic inflammation in HIV

OBJECTIVE

Chronic inflammation in HIV-infected individuals drives disease progression and the development of comorbidities, despite viral suppression with combined antiretroviral therapy. Here, we sought evidence that vagal dysfunction, which occurs commonly as part of HIV-associated autonomic neuropathy, could exacerbate inflammation through gastrointestinal dysmotility, small intestinal bacterial overgrowth (SIBO), and alterations in patterns of soluble immune mediators.

DESIGN

This is a cross-sectional observational study.

METHODS

Forty participants on stable combined antiretroviral therapy with gastrointestinal symptoms, and no causes for vagal or gastrointestinal dysfunction other than HIV, underwent autonomic testing, hydrogen/methane breath testing for SIBO, and gastric emptying scintigraphy. A panel of 41 cytokines, high-mobility group box 1, and markers of bacterial translocation (lipopolysaccharide) and monocyte/macrophage activation (sCD14 and sCD163) were tested in plasma.

RESULTS

We found that participants with vagal dysfunction had delayed gastric emptying and higher prevalence of SIBO. SIBO was associated with IL-6, but not sCD14; lipopolysaccharide could not be detected in any participant. We also found alteration of cytokine networks in participants with vagal dysfunction, with stronger and more numerous positive correlations between cytokines. In the vagal dysfunction group, high mobility group box 1 was the only soluble mediator displaying strong negative correlations with other cytokines, especially those cytokines that had numerous other strong positive correlations.

CONCLUSION

The current study provides evidence that the vagal component of HIV-associated autonomic neuropathy is associated with changes in immune and gastrointestinal function in individuals with well treated HIV. Further study will be needed to understand whether therapies targeted at enhancing vagal function could be of benefit in HIV.

Soluble CD14 levels in plasma and breastmilk of Malawian HIV+ women: Lack of association with morbidity and mortality in their exposed infants

PROBLEM

Data on soluble CD14 (sCD14) during pregnancy and lactation are scarce. We assessed the levels of sCD14 in plasma and breastmilk of Malawian HIV-positive women and evaluated the possible association with morbidity and mortality in the HIV-exposed children.

METHOD OF STUDY

One hundred and forty-nine mother/child pairs were studied. Women received antiretroviral therapy from 26 weeks of gestation to at least 6 months of exclusive breastfeeding. sCD14 concentrations were determined using an enzyme-linked immunosorbent assay.

RESULTS

sCD14 levels measured at 26 weeks of pregnancy (median: 1418 ng/mL, IQR: 1086-1757) were inversely correlated to maternal CD4+ cell count (r = -.283, P = .001) and to neonatal birthweight (r = -.233, P = .008). At 6 months, sCD14 plasma levels were significantly higher compared to baseline (1993 ng/mL, IQR: 1482-2604, P < .001), and breastmilk sCD14 levels (7668 ng/mL, IQR: 5495-10207) were 4-fold higher than in plasma (although the concentrations in the two compartments were not correlated). No association was found between sCD14 levels in plasma or breastmilk and morbidity or mortality in children.

CONCLUSION

Higher sCD14 levels in HIV-positive women were associated with a more compromised maternal immunological status and to a lower neonatal birthweight, but not to poorer clinical outcomes in the HIV-exposed children.

Exploring the link between innate immune activation and thymic function by measuring sCD14 and TRECs in HIV patients living in Belgium

Microbial translocation is now viewed as a central event in the pathogenesis of chronic inflammation during HIV infection. Thymic function failure is another crucial factor involved in HIV disease progression. The goal of this study was to explore the hypothesis of potential links between microbial translocation and thymic function in HIV-1 patients living in Belgium. The extent of microbial translocation was assessed through the measurement of soluble CD14 (sCD14). T-cell receptor excision circles (sjTRECs and dβTRECs) were used as a measure of thymic function. Data were collected from 75 HIV-infected patients. Simple and complex linear regressions were done to analyze the link between these two processes. We found a statistically relevant negative correlation between thymopoiesis (sjTREC) and sCD14 level (p = 0.004). These results suggest a link between thymic function failure, microbial translocation and innate immune activation.

Higher CD163 levels are associated with insulin resistance in hepatitis C virus-infected and HIV-infected adults

OBJECTIVES

HIV/hepatitis C virus (HCV) coinfection is associated with insulin resistance, but the mechanism is unclear. We hypothesized that intestinal epithelial damage and the consequent monocyte/macrophage activation and inflammation explain this perturbation.

DESIGN

Cross-sectional study of 519 adults (220 HIV+/HCV-; 64 HIV-/HCV+; 89 HIV+/HCV+; 146 HIV-/HCV-).

METHODS

We used multivariable linear regression to evaluate associations of HIV and HCV with the homeostasis model assessment of insulin resistance (HOMA-IR) and if intestinal fatty (FA) acid binding protein (I-FABP, a marker of gut epithelial integrity), soluble CD14 (sCD14) and soluble CD163 (sCD163) (markers of monocyte/macrophage activation), and IL-6 (an inflammatory cytokine) mediated this association.

RESULTS

HIV+/HCV+ and HIV-/HCV+ had greater demographic-adjusted HOMA-IR [mean (95% confidence interval (CI)): 1.96 (1.51, 2.54) and 1.65 (1.22, 2.24)] than HIV+/HCV- and HIV-/HCV-[1.41 (1.18, 1.67) and 1.44 (1.17, 1.75), respectively]. After additional adjustment for lifestyle and metabolic factors, HIV+/HCV+ remained associated with 36% (95% CI: 4, 80%) greater HOMA-IR relative to HIV-/HCV-, whereas HIV-/HCV+ and HIV+/HCV- had smaller differences. Adjustment for sCD163 substantially attenuated the difference between HIV+/HCV+ and HIV-/HCV-; adjustment for I-FABP, sCD14, and IL-6 had little effect. Higher sCD163 was independently associated with 19% (95% CI: 7, 33%), 26% (95% CI: 15, 39%), 25% (95% CI: 14, 37%), and 23% (95% CI: 11, 36%) greater HOMA-IR in HIV+/HCV+, HIV-/HCV+, HIV+/HCV-, and HIV-/HCV- (all estimates per doubling of sCD163). I-FABP, sCD14, and IL-6 were not associated with HOMA-IR.

CONCLUSION

HIV/HCV coinfection is associated with greater HOMA-IR, even after controlling for demographic, lifestyle, and metabolic factors. sCD163, which appears independent of intestinal epithelial damage and inflammation, partly explains this association. Our findings that the association of sCD163 with HOMA-IR occurred even in the absence of HIV and HCV, indicate that viral and nonviral factors affect sCD163 levels. Its role in insulin resistance needs elucidation.

Curing HIV: Moving Forward Faster

There is enormous enthusiasm in the scientific community for finding a cure for HIV. Although much remains to be discovered regarding the mechanisms of viral persistence and how it may be disrupted, some assumptions regarding the goals of a cure, applicability to target populations, and what is required of the assays we employ, may lead to missed opportunities and discoveries and hamper the discovery of a product that will safely cure tens of millions of HIV-infected people around the world. The field will benefit from an awareness and critical interrogation of assumptions that may be implicit in their scientific pursuits.