Altered gut microbiota correlate with different immune responses to HAART in HIV-infected individuals

Exercise to Prevent Accelerated Vascular Aging in People Living With HIV

Given advances in antiretroviral therapy, the mortality rate for HIV infection has dropped considerably over recent decades. However, people living with HIV (PLWH) experience longer life spans coupled with persistent immune activation despite viral suppression and potential toxicity from long-term antiretroviral therapy use. Consequently, PLWH face a cardiovascular disease (CVD) risk more than twice that of the general population, making it the leading cause of death among this group. Here, we briefly review the epidemiology of CVD in PLWH highlighting disparities at the intersections of sex and gender, age, race/ethnicity, and the contributions of social determinants of health and psychosocial stress to increased CVD risk among individuals with marginalized identities. We then overview the pathophysiology of HIV and discuss the primary factors implicated as contributors to CVD risk among PLWH on antiretroviral therapy. Subsequently, we highlight the functional evidence of premature vascular dysfunction as an early pathophysiological determinant of CVD risk among PLWH, discuss several mechanisms underlying premature vascular dysfunction in PLWH, and synthesize current research on the pathophysiological mechanisms underlying accelerated vascular aging in PLWH, focusing on immune activation, chronic inflammation, and oxidative stress. We consider understudied aspects such as HIV-related changes to the gut microbiome and psychosocial stress, which may serve as mechanisms through which exercise can abrogate accelerated vascular aging. Emphasizing the significance of exercise, we review various modalities and their impacts on vascular health, proposing a holistic approach to managing CVD risks in PLWH. The discussion extends to critical future study areas related to vascular aging, CVD, and the efficacy of exercise interventions, with a call for more inclusive research that considers the diversity of the PLWH population.

Alterations in the Gut Microbiome Composition of People Living with HIV in the Asia-Pacific Region: A Systematic Review

Human immunodeficiency virus (HIV) infection continues to present a global health issue. Recent studies have explored the potential role of the gut microbiome in HIV infection for novel therapeutic approaches. We investigated the gut microbiome composition of people living with HIV (PLHIV) in the Asia-Pacific region. This review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. An electronic search was conducted in the PubMed/MEDLINE, Scopus, and ScienceDirect databases using keywords such as "HIV", "PLHIV", "AIDS", "gut microbiome", "gut dysbiosis", and "metagenomics". Only peer-reviewed and full-text studies published in English were included. A total of 15 studies from the Asia-Pacific region were included for analysis. Compared to healthy controls, PLHIV showed an increased abundance of Proteobacteria and its genera, which may be considered pathobionts, and decreased abundances of Bacteroidetes and several genera under Firmicutes with known short-chain fatty acid and immunoregulatory activities. Predominant taxa such as Ruminococcaceae and Prevotellaceae were also associated with clinical factors such as CD4 count, the CD4/CD8 ratio, and inflammatory cytokines. This review highlights gut microbiome changes among PLHIV in the Asia-Pacific region, indicating potential bacterial signatures for prognostication. The partial restoration of the microbiome toward beneficial taxa may ensure the long-term success of treatment, promoting immune recovery while maintaining viral load suppression.

Peripheral-central network analysis of cancer cachexia status accompanied by the polarization of hypothalamic microglia with low expression of inhibitory immune checkpoint receptors

While the excessive inflammation in cancer cachexia is well-known to be induced by the overproduction of inflammatory mediators in the periphery, microflora disruption and brain dysfunction are also considered to contribute to the induction of cancer cachexia. Hypothalamic microglia play a crucial role in brain inflammation and central-peripheral immune circuits via the production of inflammatory mediators. In the present study, we evaluated possible changes in excessive secretion of gut microbiota-derived endotoxin and the expression timeline of several inflammation-regulatory mediators and their inhibiting modulators in hypothalamic microglia of a mouse model of cancer cachexia following transplantation of pancreatic cancer cells. We demonstrated that the plasma level of lipopolysaccharide (LPS) was significantly increased with an increase in anaerobic bacteria, especially Firmicutes, in the gut at the late stage of tumor-bearing mice that exhibited dramatic appetite loss, sarcopenia and severe peripheral immune suppression. At the early stage, in which tumor-bearing mice had not yet displayed "cachexia symptoms", the mRNA expression of pro-inflammatory cytokines, but not of the neurodegenerative and severe inflammatory modulator lipocalin-2 (LCN2), was significantly increased, whereas at the late "cachexia stage", the level of LCN2 mRNA was significantly increased along with significant decreases in levels of inhibitory immune checkpoint receptors programmed death receptor-1 (PD-1) and CD112R in hypothalamic microglia. In addition, a high density of activated neurons in the paraventricular nucleus (PVN) of the hypothalamus region and a significant increase in corticosterone secretion were found in cachexia model mice. Related to the cachexia state, released corticosterone was clearly increased in normal mice with specific activation of PVN neurons. A marked decrease in the natural killer cell population was also observed in the spleen of mice with robust activation of PVN neurons as well as mice with cancer cachexia. On the other hand, in vivo administration of LPS in normal mice induced hypothalamic microglia with low expression of inhibitory immune checkpoint receptors. These findings suggest that the induction of cancer cachexia may parallel exacerbation of the hypothalamic inflammatory status with polarization to microglia expressed with low levels of inhibitory immune checkpoint receptors following LPS release from the gut microflora.

Could the gut microbiota be capable of making individuals more or less susceptible to environmental toxicants?

Environmental toxicants are chemical substances capable to impair environmental quality and exert adverse effects on humans and other animals. The main routes of exposure to these pollutants are through the respiratory tract, skin, and oral ingestion. When ingested orally, they will encounter trillions of microorganisms that live in a community - the gut microbiota (GM). While pollutants can disrupt the GM balance, GM plays an essential role in the metabolism and bioavailability of these chemical compounds. Under physiological conditions, strategies used by the GM for metabolism and/or excretion of xenobiotics include reductive and hydrolytic transformations, lyase and functional group transfer reactions, and enzyme-mediated functional transformations. Simultaneously, the host performs metabolic processes based mainly on conjugation, oxidation, and hydrolysis reactions. Thus, due to the broad variety of bacterial enzymes present in GM, the repertoire of microbial transformations of chemicals is considered a key component of the machinery involved in the metabolism of pollutants in humans and other mammals. Among pollutants, metals deserve special attention once contamination by metals is a worldwide problem, and their adverse effects can be observed even at very low concentrations due to their toxic properties. In this review, bidirectional interaction between lead, arsenic, cadmium, and mercury and the host organism and its GM will be discussed given the most recent literature, presenting an analysis of the ability of GM to alter the host organism's susceptibility to the toxic effects of heavy metals, as well as evaluating the extent to which interventions targeting the microbiota could be potential initiatives to mitigate the adverse effects resulting from poisoning by heavy metals. This study is the first to highlight the overlap between some of the bacteria found to be altered by metal exposure and the bacteria that also aid the host organism in the metabolism of these metals. This could be a key factor to determine the beneficial species able to minimize the toxicity of metals in future therapeutic approaches.

Distinct intestinal microbial signatures linked to accelerated systemic and intestinal biological aging

BACKGROUND

People living with HIV (PLWH), even when viral replication is controlled through antiretroviral therapy (ART), experience persistent inflammation. This inflammation is partly attributed to intestinal microbial dysbiosis and translocation, which may lead to non-AIDS-related aging-associated comorbidities. The extent to which living with HIV - influenced by the infection itself, ART usage, sexual orientation, or other associated factors - affects the biological age of the intestines is unclear. Furthermore, the role of microbial dysbiosis and translocation in the biological aging of PLWH remains to be elucidated. To investigate these uncertainties, we used a systems biology approach, analyzing colon and ileal biopsies, blood samples, and stool specimens from PLWH on ART and people living without HIV (PLWoH) as controls.

RESULTS

PLWH exhibit accelerated biological aging in the colon, ileum, and blood, as measured by various epigenetic aging clocks, compared to PLWoH. Investigating the relationship between microbial translocation and biological aging, PLWH had decreased levels of tight junction proteins in the intestines, along with increased microbial translocation. This intestinal permeability correlated with faster biological aging and increased inflammation. When investigating the relationship between microbial dysbiosis and biological aging, the intestines of PLWH had higher abundance of specific pro-inflammatory bacteria, such as Catenibacterium and Prevotella. These bacteria correlated with accelerated biological aging. Conversely, the intestines of PLWH had lower abundance of bacteria known for producing the anti-inflammatory short-chain fatty acids, such as Subdoligranulum and Erysipelotrichaceae, and these bacteria were associated with slower biological aging. Correlation networks revealed significant links between specific microbial genera in the colon and ileum (but not in feces), increased aging, a rise in pro-inflammatory microbe-related metabolites (e.g., those in the tryptophan metabolism pathway), and a decrease in anti-inflammatory metabolites like hippuric acid.

CONCLUSIONS

We identified specific microbial compositions and microbiota-related metabolic pathways that are intertwined with intestinal and systemic biological aging. This microbial signature of biological aging is likely reflecting various factors including the HIV infection itself, ART usage, sexual orientation, and other aspects associated with living with HIV. A deeper understanding of the mechanisms underlying these connections could offer potential strategies to mitigate accelerated aging and its associated health complications. Video Abstract.

Gut Microbiota and Other Factors Associated With Increased Regulatory T Cells in Hiv-exposed Uninfected Infants

HIV-exposed uninfected infants (HEU) have higher infectious morbidity than HIV-unexposed infants (HUU). HEU have multiple immune defects of unknown origin. We hypothesized that HEU have higher regulatory T cells (Treg) than HUU, which may dampen their immune defenses against pathogens. We compared 25 Treg subsets between HEU and HUU and sought the factors that may affect Treg frequencies. At birth, 3 Treg subsets, including CD4 + FOXP3 + and CD4 + FOXP3 + CD25+, had higher frequencies in 123 HEU than 117 HUU and 3 subsets were higher in HUU. At 28 and 62 weeks of life, 5 Treg subsets were higher in HEU, and none were higher in HUU. The frequencies of the discrepant Treg subsets correlated at birth with differential abundances of bacterial taxas in maternal gut microbiome and at subsequent visits in infant gut microbiomes. In vitro, bacterial taxa most abundant in HEU expanded Treg subsets with higher frequencies in HEU, recapitulating the in vivo observations. Other factors that correlated with increased Treg were low maternal CD4 + T cells in HEU at birth and male sex in HUU at 28 weeks. We conclude that maternal and infant gut dysbiosis are central to the Treg increase in HEU and may be targeted by mitigating interventions.

Association of gut microbiota with the pathogenesis of SARS-CoV-2 Infection in people living with HIV

BACKGROUND

People living with HIV (PLWH) with chronic inflammation may have an increasing risk for coronavirus disease 2019 (COVID-19) severity; however, the impact of their gut microbiota on COVID-19 is not fully elucidated. Here, we analyzed the temporal changes in the gut microbiota composition of hospitalized severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected PLWH (PLWH-CoV) and their correlation with COVID-19 severity.

RESULT

The 16S rRNA analysis results using stool samples (along the timeline from disease onset) from 12 hospitalized PLWH-CoV, whose median CD4 + T cell count was 671 cells/µl, were compared to those of 19 healthy people and 25 PLWH. Bacterial diversity in PLWH-CoV is not significantly different from that of healthy people and SARS-CoV-2 non-infected PLWH, but a significant difference in the microbiota diversity was observed in the classification according to the disease severity. Immediately after the disease onset, remarkable changes were observed in the gut microbiota of PLWH-CoV, and the changing with a decrease in some short-chain fatty acid-producing bacteria and an increase in colitis-related pathobiont. In the second week after disease onset, relative amounts of specific bacteria distinguished between disease severity. One month after the disease onset, dysbiosis of the gut microbiota persisted, and the number of Enterobacteriaceae, mainly Escherichia-Shigella, which is potentially pathogenic, increased and were enriched in patients who developed post-acute sequelae of COVID-19 (PASC).

CONCLUSION

The changes in the gut microbiota associated with SARS-CoV-2 infection observed in PLWH in this study indicated a persistent decrease in SCFA-producing bacteria and an intestinal environment with an increase in opportunistic pathogens associated with enteritis. This report demonstrates that the intestinal environment in PLWH tends to show delayed improvement even after COVID-19 recovery, and highlights the importance of the dysbiosis associated with SARS-CoV-2 infection as a potential factor in the COVID-19 severity and the PASC in PLWH.

Integrated analysis of gut and oral microbiome in men who have sex with men with HIV Infection

IMPORTANCE

Our longitudinal integrated study has shown the marked alterations in the gut and oral microbiome resulting from acute and chronic HIV infection and from antiretroviral therapy. Importantly, the relationship between oral and gut microbiomes in people living with acute and chronic HIV infection and "healthy" controls has also been explored. These findings might contribute to a better understanding of the interactions between the oral and gut microbiomes and its potential role in HIV disease progression.

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.

Distinct Intestinal Microbial Signatures Linked to Accelerated Biological Aging in People with HIV

Background

People with HIV (PWH), even with controlled viral replication through antiretroviral therapy (ART), experience persistent inflammation. This is partly due to intestinal microbial dysbiosis and translocation. Such ongoing inflammation may lead to the development of non-AIDS-related aging-associated comorbidities. However, there remains uncertainty regarding whether HIV affects the biological age of the intestines and whether microbial dysbiosis and translocation influence the biological aging process in PWH on ART. To fill this knowledge gap, we utilized a systems biology approach, analyzing colon and ileal biopsies, blood samples, and stool specimens from PWH on ART and their matched HIV-negative counterparts.

Results

Despite having similar chronological ages, PWH on ART exhibit accelerated biological aging in the colon, ileum, and blood, as measured by various epigenetic aging clocks, compared to HIV-negative controls. Investigating the relationship between microbial translocation and biological aging, PWH on ART had decreased levels of tight junction proteins in the colon and ileum, along with increased microbial translocation. This increased intestinal permeability correlated with faster intestinal and systemic biological aging, as well as increased systemic inflammation. When investigating the relationship between microbial dysbiosis and biological aging, the intestines of PWH on ART had higher abundance of specific pro-inflammatory bacterial genera, such as Catenibacterium and Prevotella. These bacteria significantly correlated with accelerated local and systemic biological aging. Conversely, the intestines of PWH on ART had lower abundance of bacterial genera known for producing short-chain fatty acids and exhibiting anti-inflammatory properties, such as Subdoligranulum and Erysipelotrichaceae, and these bacteria taxa were associated with slower biological aging. Correlation networks revealed significant links between specific microbial genera in the colon and ileum (but not in feces), increased aging, a rise in pro-inflammatory microbial-related metabolites (e.g., those in the tryptophan metabolism pathway), and a decrease in anti-inflammatory metabolites like hippuric acid and oleic acid.

Conclusions

We identified a specific microbial composition and microbiome-related metabolic pathways that are intertwined with both intestinal and systemic biological aging in PWH on ART. A deeper understanding of the mechanisms underlying these connections could potentially offer strategies to counteract premature aging and its associated health complications in PWH.

Therapeutically targeting the consequences of HIV-1-associated gastrointestinal dysbiosis: Implications for neurocognitive and affective alterations

Approximately 50 % of the individuals living with human immunodeficiency virus type 1 (HIV-1) are plagued by debilitating neurocognitive impairments (NCI) and/or affective alterations. Sizeable alterations in the composition of the gut microbiome, or gastrointestinal dysbiosis, may underlie, at least in part, the NCI, apathy, and/or depression observed in this population. Herein, two interrelated aims will be critically addressed, including: 1) the evidence for, and functional implications of, gastrointestinal microbiome dysbiosis in HIV-1 seropositive individuals; and 2) the potential for therapeutically targeting the consequences of this dysbiosis for the treatment of HIV-1-associated NCI and affective alterations. First, gastrointestinal microbiome dysbiosis in HIV-1 seropositive individuals is characterized by decreased alpha (α) diversity, a decreased relative abundance of bacterial species belonging to the Bacteroidetes phylum, and geographic-specific alterations in Bacillota (formerly Firmicutes) spp. Fundamentally, changes in the relative abundance of Bacteroidetes and Bacillota spp. may underlie, at least in part, the deficits in γ-aminobutyric acid and serotonin neurotransmission, as well as prominent synaptodendritic dysfunction, observed in this population. Second, there is compelling evidence for the therapeutic utility of targeting synaptodendritic dysfunction as a method to enhance neurocognitive function and improve motivational dysregulation in HIV-1. Further research is needed to determine whether the therapeutics enhancing synaptic efficacy exert their effects by altering the gut microbiome. Taken together, understanding gastrointestinal microbiome dysbiosis resulting from chronic HIV-1 viral protein exposure may afford insight into the mechanisms underlying HIV-1-associated neurocognitive and/or affective alterations; mechanisms which can be subsequently targeted via novel therapeutics.

Increased Microbial Translocation is a Prognostic Biomarker of Different Immune Responses to ART in People Living with HIV

Background

Microbial translocation (MT) is a characteristic of human immunodeficiency virus (HIV) infection. Whether MT is also a biomarker of different immune responses to antiretroviral therapy (ART) received by people living with HIV (PLWH) is not known.

Methods

We examined the presence of MT in a cohort of 33 HIV-infected immunological responders (IRs) and 28 immunological non-responders (INRs) (≥500 and <200 cluster of differentiation (CD)4+ T-cell counts/µL after 2 years of HIV-1 suppression, respectively) with no comorbidities. Plasma samples were used to measure the circulating levels of MT markers. All enrolled study participants had received 2 years of viral-suppression therapy.

Results

Levels of lipopolysaccharide (P = 0.0185), LPS-binding protein (P < 0.0001), soluble-CD14 (P < 0.0001), and endogenous endotoxin-core antibody (P < 0.0001) at baseline were significantly higher in INRs than in IRs and were associated with an increased risk of an immunological non-response, whereas the level of intestinal fatty acid-binding protein did not show this association. Analysis of receiver operating characteristic (ROC) curves demonstrated the utility of these individual microbial markers in discriminating INRs after ART in people living with HIV with high sensitivity, specificity, and area under the ROC curve.

Conclusion

INRs in HIV infection are characterized by increased MT at baseline. These markers could be used as a rapid prognostic tool for predicting immune responses in people infected with the HIV.

Associations of HIV and iron status with gut microbiota composition, gut inflammation and gut integrity in South African school-age children: a two-way factorial case-control study

BACKGROUND

Human immunodeficiency virus (HIV) and iron deficiency (ID) affect many African children. Both HIV and iron status interact with gut microbiota composition and related biomarkers. The study's aim was to determine the associations of HIV and iron status with gut microbiota composition, gut inflammation and gut integrity in South African school-age children.

METHODS

In this two-way factorial case-control study, 8- to 13-year-old children were enrolled into four groups based on their HIV and iron status: (1) With HIV (HIV+) and ID (n = 43), (2) HIV+ and iron-sufficient nonanaemic (n = 41), (3) without HIV (HIV-) and ID (n = 44) and (4) HIV- and iron-sufficient nonanaemic (n = 38). HIV+ children were virally suppressed (<50 HIV RNA copies/ml) on antiretroviral therapy (ART). Microbial composition of faecal samples (16S rRNA sequencing) and markers of gut inflammation (faecal calprotectin) and gut integrity (plasma intestinal fatty acid-binding protein [I-FABP]) were assessed.

RESULTS

Faecal calprotectin was higher in ID versus iron-sufficient nonanaemic children (p = 0.007). I-FABP did not significantly differ by HIV or iron status. ART-treated HIV (redundancy analysis [RDA] R2  = 0.009, p = 0.029) and age (RDA R2  = 0.013 p = 0.004) explained the variance in the gut microbiota across the four groups. Probabilistic models showed that the relative abundance of the butyrate-producing genera Anaerostipes and Anaerotruncus was lower in ID versus iron-sufficient children. Fusicatenibacter was lower in HIV+ and in ID children versus their respective counterparts. The prevalence of the inflammation-associated genus Megamonas was 42% higher in children with both HIV and ID versus HIV- and iron-sufficient nonanaemic counterparts.

CONCLUSIONS

In our sample of 8- to 13-year-old virally suppressed HIV+ and HIV- children with or without ID, ID was associated with increased gut inflammation and changes in the relative abundance of specific microbiota. Moreover, in HIV+ children, ID had a cumulative effect that further shifted the gut microbiota to an unfavourable composition.

Enteropathy and gut dysbiosis as obstacles to achieve immune recovery in undetectable people with HIV: a clinical view of evidence, successes, and projections

Immune performance following antiretroviral therapy initiation varies among patients. Despite achieving viral undetectability, a subgroup of patients fails to restore CD4+ T-cell counts during follow-up, which exposes them to non-AIDS defining comorbidities and increased mortality. Unfortunately, its mechanisms are incompletely understood, and no specific treatment is available. In this review, we address some of the pathophysiological aspects of the poor immune response from a translational perspective, with emphasis in the interaction between gut microbiome, intestinal epithelial dysfunction, and immune system, and we also discuss some studies attempting to improve immune performance by intervening in this vicious cycle.

HIV-Associated Microbial Translocation May Affect Cytokine Production of CD56bright NK Cells via Stimulation of Monocytes

The mechanisms involved in HIV-associated natural killer (NK) cell impairment are still incompletely understood. We observed HIV infection to be associated with increased plasma levels of IFABP, a marker for gut epithelial barrier dysfunction, and LBP, a marker for microbial translocation. Both IFABP and LBP plasma concentrations were inversely correlated with NK cell interferon-γ production, suggesting microbial translocation to modulate NK cell functions. Accordingly, we found lipopolysaccharide to have an indirect inhibitory effect on NK cells via triggering monocytes' transforming growth factor-β production. Taken together, our data suggest increased microbial translocation to be involved in HIV-associated NK cell dysfunction.

The Gut Microbiome, Microbial Metabolites, and Cardiovascular Disease in People Living with HIV

PURPOSE OF REVIEW

To synthesize recent evidence relating the gut microbiome and microbial metabolites to cardiovascular disease (CVD) in people living with HIV (PLWH).

RECENT FINDINGS

A few cross-sectional studies have reported on the gut microbiome and cardiovascular outcomes in the context of HIV, with no consistent patterns emerging. The largest such study found that gut Fusobacterium was associated with carotid artery plaque. More studies have evaluated microbial metabolite trimethylamine N-oxide with CVD risk in PLWH, but results were inconsistent, with recent prospective analyses showing null effects. Studies of other microbial metabolites are scarce. Microbial translocation biomarkers (e.g., lipopolysaccharide binding protein) have been related to incident CVD in PLWH. Microbial translocation may increase CVD risk in PLWH, but there is insufficient and/or inconsistent evidence regarding specific microbial species and microbial metabolites associated with cardiovascular outcomes in PLWH. Further research is needed in large prospective studies integrating the gut microbiome, microbial translocation, and microbial metabolites with cardiovascular outcomes in PLWH.

Unraveling the Complex Interconnection between Specific Inflammatory Signaling Pathways and Mechanisms Involved in HIV-Associated Colorectal Oncogenesis

The advancement of HIV treatment has led to increased life expectancy. However, people living with HIV (PLWH) are at a higher risk of developing colorectal cancers. Chronic inflammation has a key role in oncogenesis, affecting the initiation, promotion, transformation, and advancement of the disease. PLWH are prone to opportunistic infections that trigger inflammation. It has been documented that 15-20% of cancers are triggered by infections, and this percentage is expected to be increased in HIV co-infections. The incidence of parasitic infections such as helminths, with Ascariasis being the most common, is higher in HIV-infected individuals. Cancer cells and opportunistic infections drive a cascade of inflammatory responses which assist in evading immune surveillance, making them survive longer in the affected individuals. Their survival leads to a chronic inflammatory state which further increases the probability of oncogenesis. This review discusses the key inflammatory signaling pathways involved in disease pathogenesis in HIV-positive patients with colorectal cancers. The possibility of the involvement of co-infections in the advancement of the disease, along with highlights on signaling mechanisms that can potentially be utilized as therapeutic strategies to prevent oncogenesis or halt cancer progression, are addressed.

Alterations in circulating markers in HIV/AIDS patients with poor immune reconstitution: Novel insights from microbial translocation and innate immunity

After long-term anti-retroviral therapy (ART) treatment, most human immunodeficiency virus (HIV)/Acquired Immure Deficiency Syndrome (AIDS) patients can achieve virological suppression and gradual recovery of CD4⁺ T-lymphocyte (CD4⁺ T cell) counts. However, some patients still fail to attain normal CD4⁺ T cell counts; this group of patients are called immune non-responders (INRs), and these patients show severe immune dysfunction. The potential mechanism of poor immune reconstitution (PIR) remains unclear and the identification of uniform biomarkers to predict the occurrence of PIR is particularly vital. But limited information is available on the relationship between circulating markers of INRs and immune recovery. Hence, this review summarises alterations in the intestine microbiota and associated markers in the setting of PIR to better understand host-microbiota-metabolite interactions in HIV immune reconstitution and to identify biomarkers that can predict recovery of CD4⁺ T cell counts in INRs.

Effects of viremia and CD4 recovery on gut “microbiome-immunity” axis in treatment-naïve HIV-1-infected patients undergoing antiretroviral therapy

BACKGROUND

Human immunodeficiency virus type 1 (HIV-1) infection is characterized by persistent systemic inflammation and immune activation, even in patients receiving effective antiretroviral therapy (ART). Converging data from many cross-sectional studies suggest that gut microbiota (GM) changes can occur throughout including human immunodeficiency virus (HIV) infection, treated by ART; however, the results are contrasting. For the first time, we compared the fecal microbial composition, serum and fecal microbial metabolites, and serum cytokine profile of treatment-naïve patients before starting ART and after reaching virological suppression, after 24 wk of ART therapy. In addition, we compared the microbiota composition, microbial metabolites, and cytokine profile of patients with CD4/CD8 ratio < 1 (immunological non-responders [INRs]) and CD4/CD8 > 1 (immunological responders [IRs]), after 24 wk of ART therapy.

AIM

To compare for the first time the fecal microbial composition, serum and fecal microbial metabolites, and serum cytokine profile of treatment-naïve patients before starting ART and after reaching virological suppression (HIV RNA < 50 copies/mL) after 24 wk of ART.

METHODS

We enrolled 12 treatment-naïve HIV-infected patients receiving ART (mainly based on integrase inhibitors). Fecal microbiota composition was assessed through next generation sequencing. In addition, a comprehensive analysis of a blood broad-spectrum cytokine panel was performed through a multiplex approach. At the same time, serum free fatty acid (FFA) and fecal short chain fatty acid levels were obtained through gas chromatography-mass spectrometry.

RESULTS

We first compared microbiota signatures, FFA levels, and cytokine profile before starting ART and after reaching virological suppression. Modest alterations were observed in microbiota composition, in particular in the viral suppression condition, we detected an increase of Ruminococcus and Succinivibrio and a decrease of Intestinibacter. Moreover, in the same condition, we also observed augmented levels of serum propionic and butyric acids. Contemporarily, a reduction of serum IP-10 and an increase of IL-8 levels were detected in the viral suppression condition. In addition, the same components were compared between IRs and INRs. Concerning the microflora population, we detected a reduction of Faecalibacterium and an increase of Alistipes in INRs. Simultaneously, fecal isobutyric, isovaleric, and 2-methylbutyric acids were also increased in INRs.

CONCLUSION

Our results provided an additional perspective about the impact of HIV infection, ART, and immune recovery on the “microbiome-immunity axis” at the metabolism level. These factors can act as indicators of the active processes occurring in the gastrointestinal tract. Individuals with HIV-1 infection, before ART and after reaching virological suppression with 24 wk of ART, displayed a microbiota with unchanged overall bacterial diversity; moreover, their systemic inflammatory status seems not to be completely restored. In addition, we confirmed the role of the GM metabolites in immune reconstitution.

Microbiota-Meditated Immunity Abnormalities Facilitate Hepatitis B Virus Co-Infection in People Living With HIV: A Review

Hepatitis B virus (HBV) co-infection is fairly common in people living with HIV (PLWH) and affects millions of people worldwide. Identical transmission routes and HIV-induced immune suppression have been assumed to be the main factors contributing to this phenomenon. Moreover, convergent evidence has shown that people co-infected with HIV and HBV are more likely to have long-term serious medical problems, suffer more from liver-related diseases, and have higher mortality rates, compared to individuals infected exclusively by either HIV or HBV. However, the precise mechanisms underlying the comorbid infection of HIV and HBV have not been fully elucidated. In recent times, the human gastrointestinal microbiome is progressively being recognized as playing a pivotal role in modulating immune function, and is likely to also contribute significantly to critical processes involving systemic inflammation. Both antiretroviral therapy (ART)-naïve HIV-infected subjects and ART-treated individuals are now known to be characterized by having gut microbiomic dysbiosis, which is associated with a damaged intestinal barrier, impaired mucosal immunological functioning, increased microbial translocation, and long-term immune activation. Altered microbiota-related products in PLWH, such as lipopolysaccharide (LPS) and short-chain fatty acids (SCFA), have been associated with the development of leaky gut syndrome, favoring microbial translocation, which in turn has been associated with a chronically activated underlying host immune response and hence the facilitated pathogenesis of HBV infection. Herein, we critically review the interplay among gut microbiota, immunity, and HIV and HBV infection, thus laying down the groundwork with respect to the future development of effective strategies to efficiently restore normally diversified gut microbiota in PLWH with a dysregulated gut microbiome, and thus potentially reduce the prevalence of HBV infection in this population.

Composition of the Gut Microbiota in Attention Deficit Hyperactivity Disorder: A Systematic Review and Meta-Analysis

BACKGROUND

The latest research accumulates information to explore the correlation between gut microbiota and neurodevelopmental disorders, which may lead to new approaches to treat diseases such as attention deficit/hyperactivity disorder (ADHD). However, the conclusions of previous studies are not completely consistent. The objective of the systematic review and meta-analysis was to identify evidence on the dysbiosis of gut microbiota in ADHD and find potential distinctive traits compared to healthy controls.

METHODS

Electronic databases, including PubMed, Embase, Web of Science, Cochrane Library, and PsycINFO, were searched up to August 24, 2021, using predetermined terms. Meta-analysis was performed to estimate the comparison of microbiota profiles (alpha and beta diversity) and the relative abundance of gut microbiota in ADHD patients and healthy controls.

RESULTS

A total of eight studies were included in the meta-analysis, containing 316 ADHD patients and 359 healthy controls. There was a higher Shannon index in ADHD patients than in healthy controls (SMD = 0.97; 95% CI, 0.13 to 1.82; P = 0.02; I²  = 96%), but the significance vanished after sensitivity analysis because of high heterogeneity. No significant differences in other alpha diversity indexes were found. Regarding the relative abundance of gut microbiota, the genus Blautia was significantly elevated in ADHD patients compared with controls (SMD = 0.34; 95% CI, 0.06 to 0.63; P = 0.02; I²  = 0%).

CONCLUSIONS

Patients with ADHD had gut microbiome alterations compared to healthy controls. Though more studies with strict methodology are warranted due to the high heterogeneity, further studies to translate the findings of gut microbiota dysbiosis to clinical application in ADHD patients are needed and may guide targeted therapies.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=273993], identifier PROSPERO (CRD42021273993).

Correlation Between Gut Microbiota and Testosterone in Male Patients With Type 2 Diabetes Mellitus

OBJECTIVE

This study aimed at investigating the association between testosterone levels and gut microbiota in male patients with type 2 diabetes mellitus (T2DM) and providing a new strategy to elucidate the pathological mechanism of testosterone deficiency in T2DM patients.

METHODS

In an observational study including 46 T2DM male patients, the peripheral venous blood and fecal samples of all subjects were collected. The V3-V4 regions of bacterial 16S rDNA were amplified and sequenced. Alpha and beta diversities were calculated by QIIME software. The possible association between gut microbial community and clinical indicators was assessed using the Spearman correlation coefficient. The association between the relative abundance of bacteria and testosterone levels was discovered using linear regression analysis in R language.

RESULTS

There was no substantial difference in alpha and beta diversity. Blautia and Lachnospirales were significantly much higher in the testosterone deficiency group. Linear regression analysis showed that the abundance of Firmicutes at the phylum level and Lachnospirales at the order level were negatively correlated with testosterone level. After correcting for C-reactive protein (CRP) and homeostatic model assessment of insulin resistance (HOMA-IR), the relative abundance of Lachnospirales still had a significant negative correlation with testosterone level. Meanwhile, at the genus level, Lachnoclostridium, Blautia, and Bergeyella had a statistically significant negative association with testosterone level, respectively. Blautia was positively associated with FPG and total cholesterol level. Streptococcus was found positively associated with insulin, connecting peptide, and index of homeostatic model assessment of insulin resistance.

CONCLUSION

T2DM patients with testosterone deficiency have different gut microbiota compositions compared with T2DM patients alone. Low serum testosterone patients tend to have an increased abundance of opportunistic pathogens, which may be related to the occurrence and development of testosterone deficiency.

Oral Microbiota Is Associated With Immune Recovery in Human Immunodeficiency Virus-Infected Individuals

The role of the oral microbiota in HIV-infected individuals deserves attention as either HIV infection or antiretroviral therapy (ART) may have effect on the diversity and the composition of the oral microbiome. However, few studies have addressed the oral microbiota and its interplay with different immune responses to ART in HIV-infected individuals. Salivary microbiota and immune activation were studied in 30 HIV-infected immunological responders (IR) and 34 immunological non-responders (INR) (≥500 and < 200 CD4 + T-cell counts/μl after 2 years of HIV-1 viral suppression, respectively) with no comorbidities. Metagenome sequencing revealed that the IR and the INR group presented similar salivary bacterial richness and diversity. The INR group presented a significantly higher abundance of genus Selenomonas_4, while the IR group manifested higher abundances of Candidatus_Saccharimonas and norank_p_Saccharimonas. Candidatus_Saccharimonas and norank_p_Saccharimonas were positively correlated with the current CD4 + T-cells. Candidatus_Saccharimonas was positively correlated with the markers of adaptive immunity CD4 + CD57 + T-cells, while negative correlation was found between norank _p_Saccharimonas and the CD8 + CD38 + T-cells as well as the CD4/CD8 + HLADR + CD38 + T-cells. The conclusions are that the overall salivary microbiota structure was similar in the immunological responders and immunological non-responders, while there were some taxonomic differences in the salivary bacterial composition. Selenomona_4, Candidatus_Saccharimonas, and norank _p_Saccharimonas might act as important factors of the immune recovery in the immunodeficiency patients, and Candidatus_Saccharimonas could be considered in the future as screening biomarkers for the immune responses in the HIV-infected individuals.