Low nadir CD4+ T-cell counts predict gut dysbiosis in HIV-1 infection

Characterization of the gut microbiota in different immunological responses among PLWH

Despite gut microbial dysbiosis has been demonstrated in people living with HIV (PLWH), the association between gut microbial and inflammatory cytokines in PLWH with different immunoreaction to antiretroviral therapy (ART) is poorly understood. The purpose of this study is to explore between gut microbial and inflammatory cytokines in PLWH with different immunoreaction. 68 PLWH and 27 healthy controls(HCs) in Anhui Province were recruited from December 2021 to March 2022, including 35 immunological responders (IRs) (CD4+T-cell count ≥ 350 cells/µL) and 33 immunological non-responders (INRs) (CD4+T-cell count < 350 cells/µL) without comorbidities. Blood and stool samples were collected from all participants. Blood was used to detect microbial translocation biomarkers and inflammatory cytokines. Luminex Multifactor Detection Technology was performed to quantify plasma microbial translocation biomarkers and inflammation cytokines. Bacterial 16S rDNA sequencing was performed on stool samples. Microbiome sequencing revealed that the relative abundances of Fusobacteria, Actinobacteria, Verrucomicrobiaceae Acidaminococcaceae, Fusobacteriaceae and Megasphaera were greater, whereas Verrucomicrobia, Ruminococcaceae, Megamonas, Faecalibacterium, Roseburia and Dialister were more depleted in the HIV groups than those in the HCs (all P < 0.05). In the INRs group, the relative abundances of Actinomycetales, Micrococcaceae, Actinomyces, Intestinibacter, Rothia were greater (all P < 0.05), whereas Sutterellaceae, Parabacteroides, Veillonella, Butyricimonas resulted less abundant than in the IRs (all P < 0.05). TNF-ɑ are negatively correlated with the abundances of Dialiste (P = 0.022). CD54 are negatively correlated with Dialister and Subdoligranulum (P = 0.011). Recent and baseline CD4+T cells counts are directly proportional to Butyricimonas and Parabacteroides, while are inversely proportional with Veillonella and Rothia (all P < 0.05). Dysbiosis of the gut microbial might be one of the factors leading to the different immunoreaction and therapeutic effects of ART.

The rectal microbiome: understanding its role in HIV transmission

PURPOSE OF REVIEW

Condomless receptive anal intercourse stands out as the sexual practice with highest risk of HIV-1 infection. Recent studies have suggested that the gut microbiome influences susceptibility to HIV transmission. This review explores recent research on host risk factors, the rectal microbiome composition, local inflammation, and bacteria-derived mediators that may affect HIV transmission.

RECENT FINDINGS

Constitutive host factors such as rectal mucosal structure and immune cell populations in the rectum contribute to increased susceptibility. Changes in the composition of the rectal microbiota, influenced by sexual practices and HIV infection modulate immune activation and inflammation, impacting HIV susceptibility. Bacteria-derived mediators may further influence immune responses and HIV replication in the rectal mucosa.

SUMMARY

Understanding the role of the rectal microbiome in HIV transmission has important clinical implications. Targeted interventions that modulate the microbiome may reduce susceptibility to HIV transmission by regulating immune responses and inflammation. Further research into the host-microbiome interactions could lead to novel preventive and therapeutic strategies to mitigate HIV transmission.

Exploring potential associations between the human microbiota and reservoir of latent HIV

BACKGROUND

The rapid establishment and persistence of latent HIV-1 reservoirs is one of the main obstacles towards an HIV cure. While antiretroviral therapy supresses viral replication, it does not eradicate the latent reservoir of HIV-1-infected cells. Recent evidence suggests that the human microbiome, particularly the gut microbiome, may have the potential to modulate the HIV-1 reservoir. However, literature is limited and the exact mechanisms underlying the role of the microbiome in HIV immunity and potential regulation of the viral reservoir remain poorly understood.

RESULTS

Here, we review updated knowledge on the associations between the human microbiome and HIV reservoir across different anatomical sites, including the gut, the lungs and blood. We provide an overview of the predominant taxa associated with prominent microbiome changes in the context of HIV infection. Based on the current evidence, we summarize the main study findings, with specific focus on consistent bacterial and related byproduct associations. Specifically, we address the contribution of immune activation and inflammatory signatures on HIV-1 persistence. Furthermore, we discuss possible scenarios by which bacterial-associated inflammatory mediators, related metabolites and host immune signatures may modulate the HIV reservoir size. Finally, we speculate on potential implications of microbiome-based therapeutics for future HIV-1 cure strategies, highlighting challenges and limitations inherent in this research field.

CONCLUSIONS

Despite recent advances, this review underscores the need for further research to deepen the understanding of the complex interplay between the human microbiome and HIV reservoir. Further integrative multi-omics assessments and functional studies are crucial to test the outlined hypothesis and to identify potential therapeutic targets ultimately able to achieve an effective cure for HIV.

Alterations of the gut microbiome in HIV infection highlight human anelloviruses as potential predictors of immune recovery

BACKGROUND

HIV-1 infection is characterized by a massive depletion of mucosal CD4 T cells that triggers a cascade of events ultimately linking gut microbial dysbiosis to HIV-1 disease progression and pathogenesis. The association between HIV infection and the enteric virome composition is less characterized, although viruses are an essential component of the gut ecosystem. Here, we performed a cross-sectional analysis of the fecal viral (eukaryotic viruses and bacteriophages) and bacterial microbiome in people with HIV (PWH) and in HIV-negative individuals. To gain further insight into the association between the gut microbiome composition, HIV-associated immunodeficiency, and immune recovery, we carried out a longitudinal study including 14 PWH who initiated antiretroviral therapy (ART) and were followed for 24 months with samplings performed at baseline (before ART) and at 2, 6, 12, and 24 months post-ART initiation.

RESULTS

Our data revealed a striking expansion in the abundance and prevalence of several human virus genomic sequences (Anelloviridae, Adenoviridae, and Papillomaviridae) in stool samples of PWH with severe immunodeficiency (CD4 < 200). We also noted a decreased abundance of sequences belonging to two plant viruses from the Tobamovirus genus, a reduction in bacterial alpha diversity, and a decrease in Inoviridae bacteriophage sequences. Short-term ART (24 months) was linked to a significant decrease in human Anelloviridae sequences. Remarkably, the detection of Anellovirus sequences at baseline independently predicted poor immune recovery, as did low CD4 T cell counts. The bacterial and bacteriophage populations were unique to each PWH with individualized trajectories; we found no discernable pattern of clustering after 24 months on ART.

CONCLUSION

Advanced HIV-1 infection was associated with marked alterations in the virome composition, in particular a remarkable expansion of human anelloviruses, with a gradual restoration after ART initiation. In addition to CD4 T cell counts, anellovirus sequence detection might be useful to predict and monitor immune recovery. This study confirms data on the bacteriome and expands our knowledge on the viral component of the gut microbiome in HIV-1 infection. Video Abstract.

Translocating bacteria in SIV infection are not stochastic and preferentially express cytosine methyltransferases

Microbial translocation is a significant contributor to chronic inflammation in people living with HIV (PLWH) and is associated with increased mortality and morbidity in individuals treated for long periods with antiretrovirals. The use of therapeutics to treat microbial translocation has yielded mixed effects, in part, because the species and mechanisms contributing to translocation in HIV remain incompletely characterized. To characterize translocating bacteria, we cultured translocators from chronically SIV-infected rhesus macaques. Proteomic profiling of these bacteria identified cytosine-specific methyltransferases as a common feature and therefore, a potential driver of translocation. Treatment of translocating bacteria with the cytosine methyltransferase inhibitor decitabine significantly impaired growth for several species in vitro. In rhesus macaques, oral treatment with decitabine led to some transient decreases in translocator taxa in the gut microbiome. These data provide mechanistic insight into bacterial translocation in lentiviral infection and explore a novel therapeutic intervention that may improve the prognosis of PLWH.

Causal relationships between gut microbiota, plasma metabolites, and HIV infection: insights from Mendelian randomization and mediation analysis

OBJECTIVE

Gut dysbiosis and metabolic abnormalities have been implicated in HIV infection. However, the exact causal relationships among the gut microbiota, metabolites, and HIV infection remain poorly understood. Our study involving Mendelian randomization (MR) and mediation analysis aims to unveil these causalities.

METHODS

Genetic instrumental variables for the gut microbiota were retrieved from MiBioGen consortium (n = 18,340). Metabolism-related genetic variants were sourced from the CLSA cohort (n = 8299). GWAS summary statistics for symptomatic HIV infection were derived from the FinnGen study (n = 309,154), and the UK Biobank (n = 208,808). We performed the bidirectional two-sample MR to assess causalities with the inverse-variance weighted (IVW) method as the primary analysis. Moreover, we executed a mediation analysis using two-step MR methods.

RESULTS

Compared to the causal effects of HIV infection on gut microbiota (or metabolites), those of gut microbiota (or plasma metabolites) on the risk of HIV infection were more substantial. Phylum Proteobacteria (OR: 2.114, 95% CI 1.042-4.288, P = 0.038), and genus Ruminococcaceae UCG013 (OR: 2.127, 95% CI 1.080-4.191, P = 0.029) exhibited an adverse causal effect on HIV infection, whereas genus Clostridium sensu stricto 1(OR: 0.491, 95% CI 0.252-0.956, P = 0.036) and family Erysipelotrichaceae (OR: 0.399, 95% CI 0.193-0.827, P = 0.013) acted as significant protective factors for HIV. The salicyluric glucuronide level (OR = 2.233, 95% CI 1.120-4.453, P = 0.023) exhibited a considerably adverse causal effect on HIV infection. Conversely, the salicylate-to-citrate ratio (OR: 0.417, 95% CI 0.253-0.688, P = 0.001) was identified as a protective factor for HIV. We identified only one bidirectional causality between 1-palmitoyl-GPI and HIV infection. Mechanistically, genus Haemophilus mediated the causal effects of three phospholipids on HIV infection risk: 1-palmitoyl-GPI (mediation proportion = 33.7%, P = 0.018), 1-palmitoyl-2-arachidonoyl-GPI (mediation proportion = 18.3%, P = 0.019), and 1-linoleoyl-2-linolenoyl-GPC (mediation proportion = 20.3%, P = 0.0216). Additionally, 5-Dodecenoylcarnitine (C12:1) mediated the causal effect of genus Sellimonas on the risk of HIV infection (mediation proportion = 13.7%, P = 0.0348).

CONCLUSION

Our study revealed that gut microbiota and metabolites causally influence HIV infection risk more substantially than the reverse. We identified the bidirectional causality between 1-palmitoyl-GPI (16:0) and HIV infection, and elucidated four mediation relationships. These findings provide genetic insights into prediction, prevention, and personalized medicine of HIV infection.

Diagnosis and Risk Factors of Prediabetes and Diabetes in People Living With Human Immunodeficiency Virus: Evaluation of Clinical and Microbiome Parameters

Diabetes mellitus (DM) is more common among people living with human immunodeficiency virus (PLWH) compared with healthy individuals. In a prospective multicenter study (N = 248), we identified normoglycemic (48.7%), prediabetic (44.4%), and diabetic (6.9%) PLWH. Glycosylated hemoglobin (HbA1c) and fasting blood glucose (FBG) sensitivity in defining dysglycemia was 96.8%, while addition of oral glucose tolerance test led to reclassification of only 4 patients. Inclusion of 93 additional PLWH with known DM enabled identification of multiple independent predictors of dysglycemia or diabetes: older age, higher body mass index, Ethiopian origin, HIV duration, lower integrase inhibitor exposure, and advanced disease at diagnosis. Shotgun metagenomic microbiome analysis revealed 4 species that were significantly expanded with hyperglycemia/hyperinsulinemia, and 2 species that were differentially more prevalent in prediabetic/diabetic PLWH. Collectively, we uncover multiple potential host and microbiome predictors of altered glycemic status in PLWH, while demonstrating that FBG and HbA1c likely suffice for diabetes screening. These potential diabetic predictors merit future prospective validation.

From dysbiosis to defense: harnessing the gut microbiome in HIV/SIV therapy

BACKGROUND

Although the microbiota has been extensively associated with HIV pathogenesis, the majority of studies, particularly those using omics techniques, are largely correlative and serve primarily as a basis for hypothesis generation. Furthermore, most have focused on characterizing the taxonomic composition of the bacterial component, often overlooking other levels of the microbiome. The intricate mechanisms by which the microbiota influences immune responses to HIV are still poorly understood. Interventional studies on gut microbiota provide a powerful tool to test the hypothesis of whether we can harness the microbiota to improve health outcomes in people with HIV.

RESULTS

Here, we review the multifaceted role of the gut microbiome in HIV/SIV disease progression and its potential as a therapeutic target. We explore the complex interplay between gut microbial dysbiosis and systemic inflammation, highlighting the potential for microbiome-based therapeutics to open new avenues in HIV management. These include exploring the efficacy of probiotics, prebiotics, fecal microbiota transplantation, and targeted dietary modifications. We also address the challenges inherent in this research area, such as the difficulty in inducing long-lasting microbiome alterations and the complexities of study designs, including variations in probiotic strains, donor selection for FMT, antibiotic conditioning regimens, and the hurdles in translating findings into clinical practice. Finally, we speculate on future directions for this rapidly evolving field, emphasizing the need for a more granular understanding of microbiome-immune interactions, the development of personalized microbiome-based therapies, and the application of novel technologies to identify potential therapeutic agents.

CONCLUSIONS

Our review underscores the importance of the gut microbiome in HIV/SIV disease and its potential as a target for innovative therapeutic strategies.

Gut microbiome and cardiometabolic comorbidities in people living with HIV

BACKGROUND

Despite modern antiretroviral therapy (ART), people living with HIV (PLWH) have increased relative risk of inflammatory-driven comorbidities, including cardiovascular disease (CVD). The gut microbiome could be one of several driving factors, along with traditional risk factors and HIV-related risk factors such as coinfections, ART toxicity, and past immunodeficiency.

RESULTS

PLWH have an altered gut microbiome, even after adjustment for known confounding factors including sexual preference. The HIV-related microbiome has been associated with cardiometabolic comorbidities, and shares features with CVD-related microbiota profiles, in particular reduced capacity for short-chain fatty acid (SCFA) generation. Substantial inter-individual variation has so far been an obstacle for applying microbiota profiles for risk stratification. This review covers updated knowledge and recent advances in our understanding of the gut microbiome and comorbidities in PLWH, with specific focus on cardiometabolic comorbidities and inflammation. It covers a comprehensive overview of HIV-related and comorbidity-related dysbiosis, microbial translocation, and microbiota-derived metabolites. It also contains recent data from studies in PLWH on circulating metabolites related to comorbidities and underlying gut microbiota alterations, including circulating levels of the SCFA propionate, the histidine-analogue imidazole propionate, and the protective metabolite indole-3-propionic acid.

CONCLUSIONS

Despite recent advances, the gut microbiome and related metabolites are not yet established as biomarkers or therapeutic targets. The review gives directions for future research needed to advance the field into clinical practice, including promises and pitfalls for precision medicine. Video Abstract.

Gut resistome linked to sexual preference and HIV infection

BACKGROUND

People living with HIV (PLWH) are at increased risk of acquisition of multidrug resistant organisms due to higher rates of predisposing factors. The gut microbiome is the main reservoir of the collection of antimicrobial resistance determinants known as the gut resistome. In PLWH, changes in gut microbiome have been linked to immune activation and HIV-1 associated complications. Specifically, gut dysbiosis defined by low microbial gene richness has been linked to low Nadir CD4 + T-cell counts. Additionally, sexual preference has been shown to strongly influence gut microbiome composition in PLWH resulting in different Prevotella or Bacteroides enriched enterotypes, in MSM (men-who-have-sex-with-men) or no-MSM, respectively. To date, little is known about gut resistome composition in PLWH due to the scarcity of studies using shotgun metagenomics. The present study aimed to detect associations between different microbiome features linked to HIV-1 infection and gut resistome composition.

RESULTS

Using shotgun metagenomics we characterized the gut resistome composition of 129 HIV-1 infected subjects showing different HIV clinical profiles and 27 HIV-1 negative controls from a cross-sectional observational study conducted in Barcelona, Spain. Most no-MSM showed a Bacteroides-enriched enterotype and low microbial gene richness microbiomes. We did not identify differences in resistome diversity and composition according to HIV-1 infection or immune status. However, gut resistome was more diverse in MSM group, Prevotella-enriched enterotype and gut micorbiomes with high microbial gene richness compared to no-MSM group, Bacteroides-enriched enterotype and gut microbiomes with low microbial gene richness. Additionally, gut resistome beta-diversity was different according to the defined groups and we identified a set of differentially abundant antimicrobial resistance determinants based on the established categories.

CONCLUSIONS

Our findings reveal a significant correlation between gut resistome composition and various host variables commonly associated with gut microbiome, including microbiome enterotype, microbial gene richness, and sexual preference. These host variables have been previously linked to immune activation and lower Nadir CD4 + T-Cell counts, which are prognostic factors of HIV-related comorbidities. This study provides new insights into the relationship between antibiotic resistance and clinical characteristics of PLWH.

Longitudinal analysis of microbiome composition in Ghanaians living with HIV-1

Human immunodeficiency virus (HIV) 1 infection is known to cause gut microbiota dysbiosis. Among the causes is the direct infection of HIV-1 in gut-resident CD4+ T cells, causing a cascade of phenomena resulting in the instability of the gut mucosa. The effect of HIV infection on gut microbiome dysbiosis remains unresolved despite antiretroviral therapy. Here, we show the results of a longitudinal study of microbiome analysis of people living with HIV (PLWH). We contrasted the diversity and composition of the microbiome of patients with HIV at the first and second time points (baseline_case and six months later follow-up_case, respectively) with those of healthy individuals (baseline_control). We found that despite low diversity indices in the follow-up_case, the abundance of some genera was recovered but not completely, similar to baseline_control. Some genera were consistently in high abundance in PLWH. Furthermore, we found that the CD4+ T-cell count and soluble CD14 level were significantly related to high and low diversity indices, respectively. We also found that the abundance of some genera was highly correlated with clinical features, especially with antiretroviral duration. This includes genera known to be correlated with worse HIV-1 progression (Achromobacter and Stenotrophomonas) and a genus associated with gut protection (Akkermansia). The fact that a protector of the gut and genera linked to a worse progression of HIV-1 are both enriched may signify that despite the improvement of clinical features, the gut mucosa remains compromised.

In vitro antibacterial activity of antiretroviral drugs on key commensal bacteria from the human microbiota

Introduction

Antiretroviral therapy has improved life expectancy in HIV-infected patients. However, people living with HIV under antiretroviral therapy are at higher risks of developing chronic complications and acquiring multidrug resistant bacteria than healthy population. These factors have been associated with shifts in gut microbiome composition and immune activation. It is unclear how antiretroviral drugs affect gut microbiota composition, but it has been observed that antiretroviral treatment is not able to fully restore gut health after HIV infection. Additionally, some antiretroviral drugs have shown antibacterial activity suggesting that these drugs could have a direct impact on the human microbiome composition.

Methods

We determined the in vitro antibacterial activity of 16 antiretroviral drugs against a set of key clinically relevant and human commensal bacterial strains.

Results

Our results demonstrate that 5 antiretroviral drugs have in vitro antibacterial activity against gut and vaginal human commensal bacteria. Zidovudine has antibacterial activity against Escherichia coli, Klebsiella pneumoniae and Prevotella bivia, abacavir against Gardnerella vaginalis, efavirenz against G. vaginalis and P. bivia and bictegravir against Enterococcus spp. and G. vaginalis. Moreover, we describe for the first time that elvitegravir has antibacterial activity against G. vaginalis and P. bivia and, most importantly, against vancomycin-resistant Enterococcus spp. and methicillin-resistant Staphylococcus aureus strains with MIC values of 4-16 and 4 µg/mL, respectively showing high level of effectiveness against the tested multidrug-resistant bacteria.

Discussion

Our results underscore that some antiretroviral drugs may influence the human microbiota composition. In addition, we report the potential use of elvitegravir to treat multidrug-resistant Gram-positive bacteria warranting the need of clinical studies to repurpose this antiretroviral drug.

Association between the gut microbiome and organic acid profiles in a Japanese population with HIV infection

INTRODUCTION

An increased incidence of metabolic syndrome has been observed in human immunodeficiency virus (HIV)-infected individuals. In contrast, gut dysbiosis is involved in various pathogeneses, including vascular endothelial disorders. Organic acids, including short-chain fatty acids (SCFAs), are essential for maintaining gut homeostasis. Therefore, this study aimed to explore the gut microbiome profile and organic acids in a Japanese population infected with HIV.

METHODS

Forty-nine patients with HIV infection on combination antiretroviral therapy (cART) were enrolled and divided into the high and low CD4 groups based on a CD4 cutoff of 350 cells/μL. Stool samples were analyzed by 16S ribosomal RNA next-generation sequencing and high-performance liquid chromatography. The association between the gut microbiome, including bacterial taxa and organic acids, was statistically analyzed.

RESULTS

The fecal microbial community composition was significantly different between HIV patients with CD4 counts above and below 350 cells/μL. The relative abundance of Roseburia, Prevotella, Prevotella_9, and [Clostridium]_methylpentosum_group were significantly enriched in the high CD4 group. Fecal succinic acid tended to be more abundant in the low CD4 group, and acetic, propionic, and butyric acids tended to be more abundant in the high CD4 group. Roseburia was positively correlated with butyric acid levels. Prevotella_9 and Prevotella were negatively correlated with succinic acid levels and positively correlated with acetic and propionic acid levels.

CONCLUSIONS

This study showed intestinal dysbiosis bordering on a CD4 count of 350 in patients with HIV infection undergoing cART. These findings might help in understanding intestinal damage and systemic inflammation in HIV infection.

The long-term gut bacterial signature of a wild primate is associated with a timing effect of pre- and postnatal maternal glucocorticoid levels

BACKGROUND

During development, elevated levels of maternal glucocorticoids (GCs) can have detrimental effects on offspring morphology, cognition, and behavior as well as physiology and metabolism. Depending on the timing of exposure, such effects may vary in strength or even reverse in direction, may alleviate with age, or may concern more stable and long-term programming of phenotypic traits. Maternal effects on gut bacterial diversity, composition, and function, and the persistence of such effects into adulthood of long-lived model species in the natural habitats remain underexplored.

RESULTS

In a cross-sectional sample of infant, juvenile, and adult Assamese macaques, the timing of exposure to elevated maternal GCs during ontogeny was associated with the gut bacterial community of the offspring. Specifically, naturally varying maternal GC levels during early but not late gestation or lactation were associated with reduced bacterial richness. The overall effect of maternal GCs during early gestation on the gut bacterial composition and function exacerbated with offspring age and was 10 times stronger than the effect associated with exposure during late prenatal or postnatal periods. Instead, variation in maternal GCs during the late prenatal or postnatal period had less pronounced or less stable statistical effects and therefore a weaker effect on the entire bacterial community composition, particularly in adult individuals. Finally, higher early prenatal GCs were associated with an increase in the relative abundance of several potential pro-inflammatory bacteria and a decrease in the abundance of Bifidobacterium and other anti-inflammatory taxa, an effect that exacerbated with age.

CONCLUSIONS

In primates, the gut microbiota can be shaped by developmental effects with strong timing effects on plasticity and potentially detrimental consequences for adult health. Together with results on other macaque species, this study suggests potential detrimental developmental effects similar to rapid inflammaging, suggesting that prenatal exposure to high maternal GC concentrations is a common cause underlying both phenomena. Our findings await confirmation by metagenomic functional and causal analyses and by longitudinal studies of long-lived, ecologically flexible primates in their natural habitat, including developmental effects that originate before birth. Video Abstract.

Oral and anal microbiome from HIV-exposed individuals: role of host-associated factors in taxa composition and metabolic pathways

Evidence indicates that the microbiome plays a significant role in HIV immunopathogenesis and associated complications. This study aimed to characterize the oral and anal microbiome of Men who have Sex with Men (MSM) and Transgender Women (TGW), with and without HIV. One hundred and thirty oral and anal DNA-derived samples were obtained from 78 participants and subjected to shotgun metagenomics sequencing for further microbiome analysis. Significant differences in the microbiome composition were found among subjects associated with HIV infection, gender, sex behavior, CD4+ T-cell counts, antiretroviral therapy (ART), and the presence of HPV-associated precancerous anal lesions. Results confirm the occurrence of oncogenic viromes in this high HIV-risk population. The oral microbiome in HIV-associated cases exhibited an enrichment of bacteria associated with periodontal disease pathogenesis. Conversely, anal bacteria showed a significant decrease in HIV-infected subjects (Coprococcus comes, Finegoldia magna, Blautia obeum, Catenibacterium mitsuokai). TGW showed enrichment in species related to sexual transmission, which concurs that most recruited TGW are or have been sex workers. Prevotella bivia and Fusobacterium gonidiaformans were positively associated with anal precancerous lesions among HIV-infected subjects. The enrichment of Holdemanella biformis and C. comes was associated with detectable viral load and ART-untreated patients. Metabolic pathways were distinctly affected by predominant factors linked to sexual behavior or HIV pathogenesis. Gene family analysis identified bacterial gene signatures as potential prognostic and predictive biomarkers for HIV/AIDS-associated malignancies. Conclusions: Identified microbial features at accessible sites are potential biomarkers for predicting precancerous anal lesions and therapeutic targets for HIV immunopathogenesis.

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.

Elevated inflammatory fecal immune factors in men who have sex with men with HIV associate with microbiome composition and gut barrier function

Introduction

People living with HIV infection (PLWH) exhibit elevated levels of gastrointestinal inflammation. Potential causes of this inflammation include HIV infection and associated immune dysfunction, sexual behaviors among men who have sex with men (MSM) and gut microbiome composition.

Methods

To better understand the etiology of gastrointestinal inflammation we examined levels of 28 fecal soluble immune factors (sIFs) and the fecal microbiome in well-defined cohorts of HIV seronegative MSM (MSM-SN), MSM with untreated HIV infection (MSM-HIV) and MSM with HIV on anti-retroviral treatment (MSMART). Additionally, fecal solutes from these participants were used to stimulate T-84 colonic epithelial cells to assess barrier function.

Results

Both MSM cohorts with HIV had elevated levels of fecal calprotectin, a clinically relevant marker of GI inflammation, and nine inflammatory fecal sIFs (GM-CSF, ICAM-1, IL-1β, IL-12/23, IL-15, IL-16, TNF-β, VCAM-1, and VEGF). Interestingly, four sIFs (GM-CSF, ICAM-1, IL-7 and IL-12/23) were significantly elevated in MSM-SN compared to seronegative male non-MSM. Conversely, IL-22 and IL-13, cytokines beneficial to gut health, were decreased in all MSM with HIV and MSM-SN respectively. Importantly, all of these sIFs significantly correlated with calprotectin, suggesting they play a role in GI inflammation. Principal coordinate analysis revealed clustering of fecal sIFs by MSM status and significant associations with microbiome composition. Additionally, fecal solutes from participants in the MSM-HIV cohort significantly decreased colonic transcellular fluid transport in vitro, compared to non-MSM-SN, and this decrease associated with overall sIF composition and increased concentrations of eight inflammatory sIFs in participants with HIV. Lastly, elevated levels of plasma, sCD14 and sCD163, directly correlated with decreased transcellular transport and microbiome composition respectively, indicating that sIFs and the gut microbiome are associated with, and potentially contribute to, bacterial translocation.

Conclusion

Taken together, these data demonstrate that inflammatory sIFs are elevated in MSM, regardless of HIV infection status, and are associated with the gut microbiome and intestinal barrier function.

Metagenomic next-generation sequencing shotgun for the diagnosis of infection in connective tissue diseases: A retrospective study

Objective

Patients with connective tissue diseases (CTDs) are at high risk of infection due to various reasons. The purpose of the study was to investigate the infection diagnosis value of metagenomic next-generation sequencing (mNGS) shotgun in CTDs to guide the use of anti-infective therapy more quickly and accurately.

Methods

In this retrospective study, a total of 103 patients with CTDs admitted with suspected infection between December 2018 and September 2021 were assessed using mNGS as well as conventional microbiological tests (CMT).

Results

Among these 103 patients, 65 were confirmed to have an infection (Group I) and 38 had no infection (Group II). mNGS reached a sensitivity of 92.31% in diagnosing pathogens in Group I. Moreover, mNGS showed good performance in identifying mixed infection. In all infection types, lung infection was the most common. mNGS also played an important role in detecting Pneumocystis jirovecii, which was associated with low CD4+ T-cell counts inextricably.

Conclusion

mNGS is a useful tool with outstanding diagnostic potential in identifying pathogens in patients with CTDs and conduce to provide guidance in clinical practice.

Immune-Related Gene Profile in HIV-Infected Patients with Discordant Immune Response

Background

Background: In spite of many reports on persistent low CD4 T cell counts and change in immune-related gene expression level in patients with HIV infection, there is still uncertainty about significant association between gene expression level and HIV infection in patients with and without discordant immune response (DIR). The aim of this study was to compare the expression level of CD4, CCL5, IFN-γ, STAT1, APOBEC3G, CD45, and ICAM-1 genes in HIV-1-positive patients with and without DIR.

Methods

Methods: In this study, 30 HIV-1-positive patients (15 patients with and 15 patients without DIR [control group]) were included. PBMCs of the patients were collected through density radient centrifugation with Ficoll-Hypaque. RNeasy Plus Mini kit was used to extract RNA. Relative expression levels of CD4, CCL5, IFN-γ, STAT1, APOBEC3G, CD45, and ICAM-1 genes were evaluated by real-time PCR. The data were analyzed using one-way ANOVA.

Results

Results: CD4 T cell counts were significantly lower in DIR patients than the control group (p < 0.01). While there was no significant difference in the relative expression levels of CD4, CCL5, IFN-γ, STAT1, CD45, and ICAM-1 between patients with DIR and control group, APOBEC3G expression level was significantly higher in the patients with DIR as compare to the control group (p < 0.01).

Conclusion

Conclusion: Our findings suggest a significantly higher APOBEC3G expression level in patients with DIR, suggesting the potential role of APOBEC3G in patients with immunological discordance besides its suppressing role in HIV-1 infection. Confirmation of this hypothesis requires further research.

Improved induced innate immune response after cART initiation in people with HIV

Introduction

Impairment of the innate immune function may contribute to the increased risk of bacterial and viral infections in people with HIV (PWH). In this study we aimed to investigate the induced innate immune responses in PWH prior to and after initiation of combinational antiretroviral therapy (cART). Furthermore, we aimed to investigate if the induced innate immune responses before initiation of cART were associated with CD4+ T-cell recovery one year after initiating cART.

Material and method

The induced innate immune response was assessed by the TruCulture® whole blood technique in 32 PWH before cART initiation and after 1, 6 and 12 months. To mimic bacterial and viral infections we used a panel of three stimuli (lipopolysaccharide (LPS), resiquimod (R848), and polyinosinic:polycytidylic acid (Poly I:C)) to stimulate the extracellular Toll-like receptor (TLR) 4 and the intracellular TLR7/8 and TLR3, respectively. The following cytokine responses were analyzed by Luminex 200: Tumor Necrosis Factor (TNF)-α, Interleukin (IL)-1b, IL-6, IL-8, IL-10, IL-12p40, IL17A, Interferon (IFN)-α, and IFN-γ.

Results

At baseline PWH with nadir CD4+ T-cell count <350 cell/µL had lower levels of LPS-, R848-, and Poly I:C-induced IL-6 and IFN-γ, LPS- and R848-induced TNF-α and IL-12, LPS induced IL-1b, and R848-induced IL-10 than PWH with nadir CD4+ T-cell count >350 cells/µL. The majority (>50%) had induced cytokine concentrations below the reference intervals at baseline which was most pronounced for the LPS- and Poly I:C-induced responses. The induced responses in the whole population improved after 12 months of cART, and more PWH had induced cytokine concentrations within the reference intervals after 12 months. However, the majority of PWH still had LPS-induced INF-α, INF-γ and Poly I:C-induced TNF-α and IL-6 below the reference interval. The induced innate immune responses before cART initiation were not associated with the CD4+ T-cell recovery after 12 months of cART.

Conclusion

The innate immune response was impaired in PWH, with a more pronounced impairment in PWH with low nadir CD4+ T-cell count. Initiation of cART improved the innate immune response, but compared to the reference intervals, some impairment remained in PWH without viral replication.

I've looked at gut from both sides now: Gastrointestinal tract involvement in the pathogenesis of SARS-CoV-2 and HIV/SIV infections

The lumen of the gastrointestinal (GI) tract contains an incredibly diverse and extensive collection of microorganisms that can directly stimulate the immune system. There are significant data to demonstrate that the spatial localization of the microbiome can impact viral disease pathogenesis. Here we discuss recent studies that have investigated causes and consequences of GI tract pathologies in HIV, SIV, and SARS-CoV-2 infections with HIV and SIV initiating GI pathology from the basal side and SARS-CoV-2 from the luminal side. Both these infections result in alterations of the intestinal barrier, leading to microbial translocation, persistent inflammation, and T-cell immune activation. GI tract damage is one of the major contributors to multisystem inflammatory syndrome in SARS-CoV-2-infected individuals and to the incomplete immune restoration in HIV-infected subjects, even in those with robust viral control with antiretroviral therapy. While the causes of GI tract pathologies differ between these virus families, therapeutic interventions to reduce microbial translocation-induced inflammation and improve the integrity of the GI tract may improve the prognoses of infected individuals.

The Effect of protease inhibitors-based antiretroviral therapy on serum/plasma interleukin-6 levels among PLHIV: a systematic review and meta-analysis

INTRODUCTION

Recommended treatment regimen for HIV infection includes protease inhibitors/ritonavir (PIs/r) combined with two nucleoside reverse transcriptase inhibitors (2NRTIs), that enable to achieve and maintain viral suppression, restore and preserve immune function. However, there were inconsistent findings on the levels of interleukin-6 levels (IL-6).

METHODOLOGY

Systematic review and meta-analysis were performed to quantify the pooled effects of PIs/r-based ART on serum/plasma IL-6 levels in PLHIV. PubMed, Web of Science, and Embase were searched from the earliest record to November 4, 2020. Data analysis was conducted on Stata version 16 and Review Manager 5.3. A random-effect model was used to compute a pooled effect size and weighted mean difference (WMD) was considered the summary effect size. Heterogeneity between studies was estimated by Cochrane's Q test (chi-square test) and I-square statistic and subgroup analysis were performed to explore the source of heterogeneity.

RESULT

Initial search identified 3098 records and five studies (seven trials) met inclusion criteria. The pooled mean difference in serum/plasma IL-6 levels from baseline to follow-up was 0.534 pg/ml (95% CI: -0.012, 1.08, P=0.05, I² =76.4%). In subgroup analysis, there was a significant association between increased serum/plasma IL-6 levels, and age group ≥35 years old, baseline CD4⁺ counts <350 cell/mm³ , and mean viral load ≥ 4.5 log10 copies/ml.

CONCLUSION

We found that serum/plasma IL-6 levels increased after combined anti-retroviral therapy (cART) among treatment-naïve individuals who initiated a successful combination of PIs/r with 2NRTIs. This result also highlights the need to monitor serum/plasma IL-6 levels during antiviral therapy, which may aid in the effective future treatment of systemic inflammation and related disorders following elevated IL-6 levels. This article is protected by copyright. All rights reserved.

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.

A Summary of the Sixth International Workshop on Microbiome in HIV Pathogenesis, Prevention, and Treatment

In October of 2020, researchers from around the world met online for the sixth annual International Workshop on Microbiome in HIV Pathogenesis, Prevention, and Treatment. New research was presented on the roles of the microbiome on immune response and HIV transmission and pathogenesis and the potential for alterations in the microbiome to decrease transmission and affect comorbidities. This article presents a summary of the findings reported.

16S rDNA sequencing analyzes differences in intestinal flora of human immunodeficiency virus (HIV) patients and association with immune activation

To clarify the influence of HIV on the intestinal flora and the interrelationship with CD4 T cells, the present study collected stool specimens from 33 HIV patients and 28 healthy subjects to compare the differences in the intestinal flora and CD4 T cells in a 16S rDNA-sequencing approach. ELISA was used to detect the expressions of interleukin 2 (IL-2), IL-8, and tumor necrosis factor-α (TNF-α). Meanwhile, correlation analysis with the different bacterial populations in each group was carried out. The results revealed that Alpha diversity indices of the intestinal flora of HIV patients were markedly lower than that of the healthy group (p < 0.05). The top five bacterial species in the HIV group were Bacteroides (23.453%), Prevotella (19.237%), Fusobacterium (12.408%), Lachnospira (3.811%), and Escherichia-Shigella (3.126%). Spearman correlation analysis results indicated that Fusobacterium_mortiferum, Fusobacterium, and Gammaproteobacteria were positively correlated with TNF-α (p < 0.05), whereas Ruminococcaceae, Bacteroidales was negatively correlated with TNF-α (p < 0.05). Additionally, Agathobacter was positively correlated with contents of IL-2 and IL-8 (p < 0.05), whereas Prevotellaceae, and Prevotella were negatively correlated with IL-8 content (p < 0.05). Furthermore, the top five strains in the CD4 high group (≥350/mm³) included Bacteroides (23.286%), Prevotella (21.943%), Fusobacterium (10.479%), Lachnospira (4.465%), and un_f_Lachnospiraceae (2.786%). Taken together, the present study identified that Fusobacterium and Escherichia-Shigella were specific and highly abundant in the HIV group and a correlation between the different bacterial flora and the contents of IL-2, IL-8, and TNF-α was revealed.

Roseburia intestinalis: A Beneficial Gut Organism From the Discoveries in Genus and Species

Roseburia intestinalis is an anaerobic, Gram-positive, slightly curved rod-shaped flagellated bacterium that produces butyrate in the colon. R. intestinalis has been shown to prevent intestinal inflammation and maintain energy homeostasis by producing metabolites. Evidence shows that this bacterium contributes to various diseases, such as inflammatory bowel disease, type 2 diabetes mellitus, antiphospholipid syndrome, and atherosclerosis. This review reveals the potential therapeutic role of R. intestinalis in human diseases. Patients with inflammatory bowel disease exhibit significant changes in R. intestinalis abundance, and they may benefit a lot from modulations targeting R. intestinalis. The data reviewed here demonstrate that R. intestinalis plays its role in regulating barrier homeostasis, immune cells, and cytokine release through its metabolite butyrate, flagellin and other. Recent advancements in the application of primary culture technology, culture omics, single-cell sequencing, and metabonomics technology have improved research on Roseburia and revealed the benefits of this bacterium in human health and disease treatment.

A Randomized, Placebo-Controlled Trial Assessing the Effect of VISBIOME ES Probiotic in People With HIV on Antiretroviral Therapy

BACKGROUND

A5350, a phase II, randomized, double-blind study, evaluated the safety and tolerability of the probiotic Visbiome Extra Strength (ES) over 24 weeks and measured effects on inflammation and intestinal barrier function.

METHODS

The primary outcome was change in soluble CD14 (sCD14) levels; secondary outcomes included safety and tolerability, markers of inflammation and cellular activation, and microbiome. In a substudy, gut permeability was assessed by paired colonic biopsies measuring the area of lamina propria occupied by CD4+ cells, interleukin (IL)-17+ cells, and myeloperoxidase (MPO). Changes between arms were compared with the 2-sample t test with equal variance or the Wilcoxon rank-sum test. For safety, the highest graded adverse events (AEs) were compared between arms using the Fisher exact test.

RESULTS

Overall, 93 participants enrolled: 86% male, median age 51 years, median CD4 count 712 cells/mm3. Visbiome ES was safe and well tolerated. There was no difference in mean change in sCD14 from baseline to week 25/26 between placebo (mean change, 92.3 µg/L; 95% CI, -48.5 to 233 µg/L) and Visbiome ES (mean change, 41.0 µg/L; 95% CI, -94.1 to 176.2 µg/L; P=.60). Similarly, no statistically significant differences between arms in inflammatory marker changes were identified. In substudy participants, no statistical differences between arms for change in cellular marker expression or gut permeability were observed (P>.05 for all). The microbiome demonstrated increased probiotic species and a significant decrease in Gammaproteobacteria (P=.044) in the Visbiome ES arm.

CONCLUSIONS

Visbiome ES was safe and altered the microbiome but demonstrated no effect on systemic inflammatory markers, pathology, or gut permeability in antiretroviral therapy-treated people with HIV.

Microbiome Studies in Non-human Primates

Purpose of Review

Observations of differing bacterial, intestinal microbiomes in people living with HIV have propelled interest in contributions of the microbiome to HIV disease. Non-human primate (NHP) models of HIV infection provide a controlled setting for assessing contributions of the microbiome by standardizing environmental confounders. We provide an overview of the findings of microbiome contributions to aspects of HIV disease derived from these animal models.

Recent Findings

Observations of differing bacterial, intestinal microbiomes are inconsistently observed in the NHP model following SIV infection. Differences in lentiviral susceptibility and vaccine efficacy have been attributed to variations in the intestinal microbiome; however, by-and-large, these differences have not been experimentally assessed.

Summary

Although compelling associations exist, clearly defined contributions of the microbiome to HIV and SIV disease are lacking. The empirical use of comprehensive multi-omics assessments and longitudinal and interventional study designs in NHP models is necessary to define this contribution more clearly.

A randomized, blinded, placebo-controlled trial of De Simone formulation probiotic during HIV-associated suboptimal CD4+ T cell recovery

OBJECTIVE

To assess whether probiotic supplementation may reduce disease-linked systemic immune activation in people living with HIV with the immunologic non-responder (INR) phenotype.

DESIGN

Phase 2b, randomized, double-blind, placebo-controlled pilot trial.

METHODS

HIV-positive individuals with blood CD4+ T cell counts <350/mm3 despite viral suppression were randomized 2:1 to receive De Simone Formulation Probiotic (DSFP; "Visbiome" commercially) or placebo for 48 weeks; target enrolment was 36 patients. The primary endpoint was change in blood CD8+ T cell co-expression of HLA-DR and CD38 ("CD8 activation"). Secondary endpoints included biomarkers of inflammation, immune reconstitution, bacterial translocation, and gut permeability. Adjusted linear regression and linear mixed methods regression evaluated the differences between study arms from baseline to week 48. Study monitoring was done by the CIHR Canadian HIV Trials Network Data Safety Monitoring Committee.

RESULTS

Nineteen patients received DSFP, while 10 received placebo. One probiotic-arm patient withdrew early. Blood CD8 activation increased 0.82 percentage points (pp) in the probiotic arm (95% confidence interval [CI];-1.23,2.87;) and decreased by 2.06pp in the placebo arm (-4.81,0.70; between arms p=0.097). CD4+ T cell activation (%HLA-DR+) decreased in the placebo arm (-3.79pp [-7.32,-0.26]) but increased in the probiotic arm (1.64 [-0.98,4.26]; between arms p=0.018). No differences were observed in plasma or urine biomarkers of inflammation or microbial translocation.

CONCLUSIONS

Blood immune activation markers in INR individuals on effective ART were not reduced by supplementation with DSFP; CD4+ T cell activation may have been increased.

Translocated microbiome composition determines immunological outcome in treated HIV infection

The impact of the microbiome on HIV disease is widely acknowledged although the mechanisms downstream of fluctuations in microbial composition remain speculative. We detected rapid, dynamic changes in translocated microbial constituents during two years after cART initiation. An unbiased systems biology approach revealed two distinct pathways driven by changes in the abundance ratio of Serratia to other bacterial genera. Increased CD4 T cell numbers over the first year were associated with high Serratia abundance, pro-inflammatory innate cytokines, and metabolites that drive Th17 gene expression signatures and restoration of mucosal integrity. Subsequently, decreased Serratia abundance and downregulation of innate cytokines allowed re-establishment of systemic T cell homeostasis promoting restoration of Th1 and Th2 gene expression signatures. Analyses of three other geographically distinct cohorts of treated HIV infection established a more generalized principle that changes in diversity and composition of translocated microbial species influence systemic inflammation and consequently CD4 T cell recovery.

Luminal microvesicles uniquely influence translocating bacteria after SIV infection

Microbial translocation contributes to persistent inflammation in both treated and untreated HIV infection. Although translocation is due in part to a disintegration of the intestinal epithelial barrier, there is a bias towards the translocation of Proteobacteria. We hypothesized that intestinal epithelial microvesicle cargo differs after HIV infection and contributes to biased translocation. We isolated gastrointestinal luminal microvesicles before and after progressive simian immunodeficiency virus (SIV) infection in rhesus macaques and measured miRNA and antimicrobial peptide content. We demonstrate that these microvesicles display decreased miR-28-5p, -484, -584-3p, and -584-5p, and let-7b-3p, as well as increased beta-defensin 1 after SIV infection. We further observed dose-dependent growth sensitivity of commensal Lactobacillus salivarius upon co-culture with isolated microvesicles. Infection-associated microvesicle differences were not mirrored in non-progressively SIV-infected sooty mangabeys. Our findings describe novel alterations of antimicrobial control after progressive SIV infection that influence the growth of translocating bacterial taxa. These studies may lead to the development of novel therapeutics for treating chronic HIV infection, microbial translocation, and inflammation.

Whole-Genome Metagenomic Analysis of the Gut Microbiome in HIV-1-Infected Individuals on Antiretroviral Therapy

Gut microbiome plays a significant role in HIV-1 immunopathogenesis and HIV-1-associated complications. Previous studies have mostly been based on 16S rRNA gene sequencing, which is limited in taxonomic resolution at the genus level and inferred functionality. Herein, we performed a deep shotgun metagenomics study with the aim to obtain a more precise landscape of gut microbiome dysbiosis in HIV-1 infection. A reduced tendency of alpha diversity and significantly higher beta diversity were found in HIV-1-infected individuals on antiretroviral therapy (ART) compared to HIV-1-negative controls. Several species, such as Streptococcus anginosus, Actinomyces odontolyticus, and Rothia mucilaginosa, were significantly enriched in the HIV-1-ART group. Correlations were observed between the degree of immunodeficiency and gut microbiome in terms of microbiota composition and metabolic pathways. Furthermore, microbial shift in HIV-1-infected individuals was found to be associated with changes in microbial virulome and resistome. From the perspective of methodological evaluations, our study showed that different DNA extraction protocols significantly affect the genomic DNA quantity and quality. Moreover, whole metagenome sequencing depth affects critically the recovery of microbial genes, including virulome and resistome, while less than 5 million reads per sample is sufficient for taxonomy profiling in human fecal metagenomic samples. These findings advance our understanding of human gut microbiome and their potential associations with HIV-1 infection. The methodological assessment assists in future study design to accurately assess human gut microbiome.

Rectal microbiota diversity in Kenyan MSM is inversely associated with frequency of receptive anal sex, independent of HIV status

OBJECTIVE

Both HIV infection and identifying as MSM have been linked to altered rectal microbiota composition, but few studies have studied sexual behavioural associations with rectal microbiota within MSM. In addition, most rectal microbiota studies in MSM have been limited geographically to Europe and North America, and replication of findings in lower and middle-income countries is lacking.

DESIGN

A cross-sectional study.

METHODS

We enrolled MSM from Nairobi, Kenya, and determined their HIV/sexually transmitted infection status. Rectal specimens were obtained for 16s rRNA sequencing of the rectal microbiota, and sexual behaviour was characterized using a standardized questionnaire. Microbiome differences were modelled using nonparametric statistics, Bray-Curtis ecological distance metrics and analyses of differential taxa abundance. Multivariable linear regression was used to model HIV status and recent sexual activity as predictors of alpha diversity, controlling for a range of covariates.

RESULTS

Alpha diversity was consistently lower in Kenyan HIV-infected MSM (n = 80), including those on antiretroviral therapy (ART) compared with HIV-uninfected MSM. A statistical trend was observed for clustering of HIV status by Prevotella or Bacteroides dominance (P = 0.13). Several taxa were enriched in HIV-positive men, including Roseburia, Lachnospira, Streptococcus and Granulicatella. Receptive anal sex with several types of sexual partners (paying, regular, casual) was associated with lower Chao1 and Simpson diversity, independent of HIV status, while HIV infection was associated lower Chao1 (P = 0.030) but not Simpson diversity (P = 0.49).

CONCLUSION

Both HIV infection and sexual behaviour were associated with rectal microflora alpha diversity, in particular richness, but not Prevotella spp. dominance, in Kenyan MSM. Associations were more robust for sexual behaviour.

Systems Analysis of Gut Microbiome Influence on Metabolic Disease in HIV-Positive and High-Risk Populations

Poor metabolic health, characterized by insulin resistance and dyslipidemia, is higher in people living with HIV and has been linked with inflammation, antiretroviral therapy (ART) drugs, and ART-associated lipodystrophy (LD). Metabolic disease is associated with gut microbiome composition outside the context of HIV but has not been deeply explored in HIV infection or in high-risk men who have sex with men (HR-MSM), who have a highly altered gut microbiome composition. Furthermore, the contribution of increased bacterial translocation and associated systemic inflammation that has been described in HIV-positive and HR-MSM individuals has not been explored. We used a multiomic approach to explore relationships between impaired metabolic health, defined using fasting blood markers, gut microbes, immune phenotypes, and diet. Our cohort included ART-treated HIV-positive MSM with or without LD, untreated HIV-positive MSM, and HR-MSM. For HIV-positive MSM on ART, we further explored associations with the plasma metabolome. We found that elevated plasma lipopolysaccharide binding protein (LBP) was the most important predictor of impaired metabolic health and network analysis showed that LBP formed a hub joining correlated microbial and immune predictors of metabolic disease. Taken together, our results suggest the role of inflammatory processes linked with bacterial translocation and interaction with the gut microbiome in metabolic disease among HIV-positive and -negative MSM.IMPORTANCE The gut microbiome in people living with HIV (PLWH) is of interest since chronic infection often results in long-term comorbidities. Metabolic disease is prevalent in PLWH even in well-controlled infection and has been linked with the gut microbiome in previous studies, but little attention has been given to PLWH. Furthermore, integrated analyses that consider gut microbiome, together with diet, systemic immune activation, metabolites, and demographics, have been lacking. In a systems-level analysis of predictors of metabolic disease in PLWH and men who are at high risk of acquiring HIV, we found that increased lipopolysaccharide-binding protein, an inflammatory marker indicative of compromised intestinal barrier function, was associated with worse metabolic health. We also found impaired metabolic health associated with specific dietary components, gut microbes, and host and microbial metabolites. This study lays the framework for mechanistic studies aimed at targeting the microbiome to prevent or treat metabolic endotoxemia in HIV-infected individuals.

Gut Microbiota Diversity in HIV-Infected Patients on Successful Antiretroviral Treatment is Linked to Sexual Preferences but not CD4 Nadir

The effects of HIV infection and antiretroviral therapy (ART) on the gut microbiome are poorly understood and the literature data are inconsistent. The aim of this study was to assess the alpha and beta diversity of the fecal microbiota in HIV-infected patients on successful antiretroviral therapy with regard to sexual preferences and CD4 nadir. Thirty-six HIV-infected ART-treated patients with HIV viremia below 20 copies/ml and CD4 > 500 cells/μl were divided into two subgroups based on CD4 nadir. The composition of the intestinal microbiota was assessed by 16SrRNA sequencing (MiSeq Illumina). The alpha and beta diversity were analyzed according to CD4 nadir count and sexual preference. Several alpha diversity indexes were significantly higher in the MSM group than in heterosexual patients. The alpha diversity did not differ significantly between patients with CD4 nadir > 500 cells/μl and CD4 nadir < 200 cells/μl. Beta diversity was also associated with sexual preference. A significant difference in Weighted Unifrac was observed between all MSM and all non-MSM participants (p = 0.001). The MSM group was more diverse and demonstrated greater distances in Weighted Unifrac than the non-MSM group. The relative abundance of the Prevotella enterotype was higher in the MSM than the non-MSM group. Sexual preferences demonstrated a stronger influence on alpha and beta diversity in HIV-infected patients following successful antiretroviral treatment than HIV infection itself. The observed lack of association between CD4 nadir and alpha and beta diversity may be caused by the restoration of the faecal microbiota following antiretroviral treatment.

The Gut Microbiota and Unhealthy Aging: Disentangling Cause from Consequence

The gut microbiota changes with age, but it is not clear to what degree these changes are due to physiologic changes, age-associated inflammation or immunosenescence, diet, medications, or chronic health conditions. Observational studies in humans find that there are profound differences between the microbiomes of long-lived and frail individuals, but the degree to which these differences promote or prevent late-life health is unclear. Studies in model organisms demonstrate that age-related microbial dysbiosis causes intestinal permeability, systemic inflammation, and premature mortality, but identifying causal relationships have been challenging. Herein, we review how physiological and immune changes contribute to microbial dysbiosis and the degree to which microbial dysbiosis contributes to late-life health conditions. We discuss the features of the aging microbiota that make it more amenable to diet and pre- and probiotic interventions. Health interventions that promote a diverse microbiome could influence the health of older adults.

Probiotics to manage inflammation in HIV infection

PURPOSE OF REVIEW

To evaluate the current scientific basis for administering probiotics to people living with HIV (PLHIV) to alleviate chronic inflammation and subsequently improve their prognosis.

RECENT FINDINGS

The gut microbiome is a potential contributing factor to low-grade inflammation in HIV infection, and there is a scientific rationale for attempting to attenuate inflammation by administering probiotics. Sixteen reports from clinical studies in antiretroviral therapy (ART)-treated PLHIV assessing inflammation after probiotic intervention have been identified; half of them randomized control trials (RCT). Some of the studies report improvement in some parameters of inflammation, but results are inconsistent. No studies report improvement of CD4 counts. None of the RCTs report improvements in any markers of inflammation when analyzed according to protocol.

SUMMARY

Current scientific evidence does not support the use of probiotics to alleviate inflammation in HIV infection. The potential effect of probiotic intervention in ART-treated PLHIV with high risk for inflammation remains to be investigated.

Long-Term Suppressive cART Is Not Sufficient to Restore Intestinal Permeability and Gut Microbiota Compositional Changes

Background: We explored the long-term effects of cART on markers of gut damage, microbial translocation, and paired gut/blood microbiota composition, with a focus on the role exerted by different drug classes.

Methods: We enrolled 41 cART naïve HIV-infected subjects, undergoing blood and fecal sampling prior to cART (T0) and after 12 (T12) and 24 (T24) months of therapy. Fifteen HIV-uninfected individuals were enrolled as controls. We analyzed: (i) T-cell homeostasis (flow cytometry); (ii) microbial translocation (sCD14, EndoCab, 16S rDNA); (iii) intestinal permeability and damage markers (LAC/MAN, I-FABP, fecal calprotectin); (iv) plasma and fecal microbiota composition (alpha- and beta-diversity, relative abundance); (v) functional metagenome predictions (PICRUSt).

Results: Twelve and twenty four-month successful cART resulted in a rise in EndoCAb (p = 0.0001) and I-FABP (p = 0.039) vis-à-vis stable 16S rDNA, sCD14, calprotectin and LAC/MAN, along with reduced immune activation in the periphery. Furthermore, cART did not lead to substantial modifications of microbial composition in both plasma and feces and metabolic metagenome predictions. The stratification according to cART regimens revealed a feeble effect on microbiota composition in patients on NNRTI-based or INSTI-based regimens, but not PI-based regimens.

Conclusions: We hereby show that 24 months of viro-immunological effective cART, while containing peripheral hyperactivation, exerts only minor effects on the gastrointestinal tract. Persistent alteration of plasma markers indicative of gut structural and functional impairment seemingly parallels enduring fecal dysbiosis, irrespective of drug classes, with no effect on metabolic metagenome predictions.

Residual immune dysfunction under antiretroviral therapy

The usage of combination antiretroviral therapy in people with HIV (PWH) has incited profound improvement in morbidity and mortality. Yet, PWH may not experience full restoration of immune function which can manifest with non-AIDS comorbidities that frequently associate with residual inflammation and can imperil quality of life or longevity. In this review, we discuss the pathogenesis underlying chronic inflammation and residual immune dysfunction in PWH, as well as potential therapeutic interventions to ameliorate them and prevent incidence or progression of non-AIDS comorbidities. Current evidence advocates that early diagnosis and prompt initiation of therapy at high CD4 counts may represent the best available approach for an improved immune recovery in PWH.

Therapeutic avenues for restoring the gut microbiome in HIV infection

The interplay between the gut microbiota, the intestinal barrier and the mucosal immune system is profoundly altered in Human Immunodeficiency Virus (HIV) infection. An HIV-associated microbial dysbiotic signature has been difficult to define due to the strong impact of confounders that are intimately linked with HIV infection, namely HIV risk behaviors. When controlling for sexual preference and gender, HIV-associated microbial dysbiotic signatures are characterized by an increase in deleterious taxa and a decrease in beneficial bacteria and their respective metabolic end-products. First attempts to restore the gut microbiota of HIV subjects on Antiretroviral Therapy using Fecal Microbiota Transplantation proved to be safe and reported mild transient engraftment of donor microbiota and no effect on markers of HIV disease progression. This review focuses on the current evidence supporting a role for microbial dysbiosis in HIV pathogenesis, and reviews current microbiome-based therapeutics for restoring the gut microbiota in HIV infection.

Shifts in microbial diversity, composition, and functionality in the gut and genital microbiome during a natural SIV infection in vervet monkeys

BACKGROUND

The microbiota plays an important role in HIV pathogenesis in humans. Microbiota can impact health through several pathways such as increasing inflammation in the gut, metabolites of bacterial origin, and microbial translocation from the gut to the periphery which contributes to systemic chronic inflammation and immune activation and the development of AIDS. Unlike HIV-infected humans, SIV-infected vervet monkeys do not experience gut dysfunction, microbial translocation, and chronic immune activation and do not progress to immunodeficiency. Here, we provide the first reported characterization of the microbial ecosystems of the gut and genital tract in a natural nonprogressing host of SIV, wild vervet monkeys from South Africa.

RESULTS

We characterized fecal, rectal, vaginal, and penile microbiomes in vervets from populations heavily infected with SIV from diverse locations across South Africa. Geographic site, age, and sex affected the vervet microbiome across different body sites. Fecal and vaginal microbiome showed marked stratification with three enterotypes in fecal samples and two vagitypes, which were predicted functionally distinct within each body site. External bioclimatic factors, biome type, and environmental temperature influenced microbiomes locally associated with vaginal and rectal mucosa. Several fecal microbial taxa were linked to plasma levels of immune molecules, for example, MIG was positively correlated with Lactobacillus and Escherichia/Shigella and Helicobacter, and IL-10 was negatively associated with Erysipelotrichaceae, Anaerostipes, Prevotella, and Anaerovibrio, and positively correlated with Bacteroidetes and Succinivibrio. During the chronic phase of infection, we observed a significant increase in gut microbial diversity, alterations in community composition (including a decrease in Proteobacteria/Succinivibrio in the gut) and functionality (including a decrease in genes involved in bacterial invasion of epithelial cells in the gut), and partial reversibility of acute infection-related shifts in microbial abundance observed in the fecal microbiome. As part of our study, we also developed an accurate predictor of SIV infection using fecal samples.

CONCLUSIONS

The vervets infected with SIV and humans infected with HIV differ in microbial responses to infection. These responses to SIV infection may aid in preventing microbial translocation and subsequent disease progression in vervets, and may represent host microbiome adaptations to the virus. Video Abstract.

Impact of Human Immunodeficiency Virus-Related Gut Microbiota Alterations on Metabolic Comorbid Conditions

BACKGROUND

We aimed to identify a human immunodeficiency virus (HIV)-related microbiota signature, independent of sexual preferences and demographic confounders, in order to assess a possible impact of the microbiome on metabolic comorbid conditions.

METHODS

Bacterial 16S ribosomal RNA analyses were performed on stool samples from 405 HIV-infected and 111 uninfected participants of the Copenhagen Comorbidity in HIV Infection (COCOMO) study. Individuals were stratified according to sexual behavior (men who have sex with men [MSM] vs non-MSM).

RESULTS

After excluding MSM-associated microbiota traits and adjusting for confounders, we identified an HIV-related microbiota signature, consisting of lower biodiversity, increased relative abundance of the bacterial clades Gammaproteobacteria and Desulfovibrionaceae and decrease in several Clostridia. This microbiota profile was associated with a 2-fold excess risk of metabolic syndrome, driven by increase in Desulfovibrionaceae and decrease in Clostridia (Butyrivibrio, Coprococcus 2, Lachnospiraceae UCG-001 and CAG-56). This association was accentuated (5-fold excess risk) in individuals with previous severe immunodeficiency, which also modified the association between HIV-related microbiota signature and visceral adipose tissue (VAT) area (P for interaction = .01). Accordingly, HIV-related microbiota was associated with 30-cm2 larger VAT in individuals with history of severe immunodeficiency, but not in those without.

CONCLUSION

The HIV-related microbiota was associated with increased risk of metabolic syndrome and VAT accumulation, particularly in individuals with previous severe immunodeficiency, driven by increased Desulfovibrionaceae and lower abundance of several Clostridia. Our findings suggest a potential interplay between HIV-related microbiota, immune dysfunction and metabolic comorbid conditions. Interventions targeting the gut microbiome may be warranted to reduce cardiovascular risk, particularly in individuals with previous immunodeficiency.

Association of intestinal and systemic inflammatory biomarkers with immune reconstitution in HIV+ patients on ART

Background

HIV infection is characterized by CD4⁺ T-cells depletion related to gut damage, microbial translocation, immune activation and intestinal and systemic low-grade inflammation. With the use of antiretroviral treatment, these alterations in HIV+ patients reach similar levels to HIV- controls. However, almost 20% patients have deficient immune reconstitution of CD4⁺ T-cells, which make them more susceptible to develop non-AIDS and AIDS comorbidities.

Methods

HIV+ patients on ART, with sustained virologic control were grouped according to their immune reconstitution as: immunological responders (n = 18) and immunological non-responders (n = 18); also, HIV- controls were enrolled (n = 14). CD4⁺ and CD8⁺ T-cell activation (HLA-DR⁺ and CD38⁺ single and co-expression) were measured by flow cytometry. Serum levels of sCD14, sCD163, lipopolysaccharide, I-FABP, sST2, as well as fecal levels of calprotectin, lactoferrin and secretory IgA were evaluated by ELISA. Levels of C-reactive protein were determined by a high sensibility singleplex bead-based immunoassay. Serum and fecal concentrations of proinflammatory cytokines were quantified by multiplex bead-based immunoassay.

Results

HLA-DR⁺ and CD38⁺ co-expression, as well as median fluorescence intensity in CD4⁺ and CD8⁺ T-cells subpopulations was greater in immunological non-responders group, after normalization and fold change calculation. Similarly, this group presented higher levels of sCD14, C-reactive protein, as well as fecal calprotectin and lactoferrin. Furthermore, both HIV+ groups showed elevated levels of proinflammatory cytokines in stool.

Conclusions

Our data suggests that despite the virologic control, HIV+ patients under treatment with deficient immune reconstitution showed elevation of both innate and T-cells immune activation, as well as intestinal and systemic inflammation. However, some patients with CD4⁺ T-cells count above 350 cells/μL also presented these alterations. Future studies are necessary to evaluate the dynamics of multiple systemic and intestinal biomarkers in diverse types of HIV+ patients, as such as their clinical impact.

Gut Microbiome Changes Associated With HIV Infection and Sexual Orientation

Background: Many studies have explored changes in the gut microbiome associated with HIV infection, but the consistent pattern of changes has not been clarified. Men who have sex with men (MSM) are very likely to be an independent influencing factor of the gut microbiome, but relevant research is still lacking.

Methods: We conducted a meta-analysis by screening 12 published studies of 16S rRNA gene amplicon sequencing of gut microbiomes related to HIV/AIDS (six of these studies contain data that is relevant and available to MSM) from NCBI and EBI databases. The analysis of gut microbiomes related to HIV infection status and MSM status included 1,288 samples (HIV-positive (HIV+) individuals, n = 744; HIV-negative (HIV–) individuals, n = 544) and 632 samples (MSM, n = 328; non-MSM, n = 304), respectively. The alpha diversity indexes, beta diversity indexes, differentially enriched genera, differentially enriched species, and differentially enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) functional pathways related to gut microbiomes were calculated. Finally, the overall trend of the above indicators was evaluated.

Results: Our results indicate that HIV+ status is associated with decreased alpha diversity of the gut microbiome. MSM status is an important factor that affects the study of HIV-related gut microbiomes; that is, MSM are associated with alpha diversity changes in the gut microbiome regardless of HIV infection, and the changes in the gut microbiome composition of MSM are more significant than those of HIV+ individuals. A consistent change in Bacteroides caccae, Bacteroides ovatus, Bacteroides uniformis, and Prevotella stercorea was found in HIV+ individuals and MSM. The differential expression of the gut microbiome may be accompanied by changes in functional pathways of carbohydrate metabolism, amino acid metabolism, and lipid Metabolism.

Conclusions: This study shows that the changes in the gut microbiome are related to HIV and MSM status. Importantly, MSM status may have a far greater impact on the gut microbiome than HIV status.

Mitochondrial Dysfunction and Insulin Resistance in Pubertal Youth Living with Perinatally Acquired HIV

Mitochondrial dysfunction (MD) is linked to cardiometabolic complications, such as obesity and insulin resistance (IR), the frequencies of which are higher in adults living with HIV infection and receiving combination antiretroviral therapies (ARV). ARV-treated youth living with perinatally acquired HIV infection (YLPHIV) may be especially susceptible to IR due to long-term exposure to both factors. Medical histories, fasting blood chemistry panels, and mitochondrial function in banked peripheral blood mononuclear cells (PBMCs) were assessed in eligible YLPHIV from the Pediatric HIV/AIDS Cohort Study (PHACS)/Adolescent Master Protocol (AMP) Mitochondrial Determinants Component cohort, stratified by Homeostatic Model Assessment of IR (HOMA-IR) score: case (score ≥4, n = 39) or control (score <4, n = 105). PBMCs were sources for mitochondrial (mt) DNA copies/cell; mtRNA transcript levels of oxidative phosphorylation (OXPHOS) subunits NADH dehydrogenases 1 and 6, and cytochrome B; and enzymatic activities of OXPHOS Complexes I (CI) and IV (CIV). Logistic regression models were fit to estimate the odds of IR case diagnosis, adjusted for sex, race/ethnicity, body mass index (BMI) z-score, and Tanner stage. IR cases were similar to controls by age, sex, and race/ethnicity. Cases had higher median levels of peak HIV viral load, lactate, pyruvate, triglycerides, and BMI z-scores. OXPHOS CI enzymatic activity was lower in cases (log₁₀ 1.62 vs. 1.70) and inversely correlated with HOMA-IR score (r = -0.157, p = .061), but did not associate with IR in adjusted models. Fully adjusted models indicated associations of nadir CD4% [odds ratio (OR) = 0.95, 95% confidence intervals (CIs) = 0.90-1.00] or peak HIV load (OR = 3.48, 95% CIs = 1.70-10.79) with IR. IR in YLPHIV was strongly associated with morphometrics, but early virologic and immunologic factors may also influence MD.

Immunometabolism and HIV-1 pathogenesis: food for thought

Antiretroviral therapies efficiently block HIV-1 replication but need to be maintained for life. Moreover, chronic inflammation is a hallmark of HIV-1 infection that persists despite treatment. There is, therefore, an urgent need to better understand the mechanisms driving HIV-1 pathogenesis and to identify new targets for therapeutic intervention. In the past few years, the decisive role of cellular metabolism in the fate and activity of immune cells has been uncovered, as well as its impact on the outcome of infectious diseases. Emerging evidence suggests that immunometabolism has a key role in HIV-1 pathogenesis. The metabolic pathways of CD4⁺ T cells and macrophages determine their susceptibility to infection, the persistence of infected cells and the establishment of latency. Immunometabolism also shapes immune responses against HIV-1, and cell metabolic products are key drivers of inflammation during infection. In this Review, we summarize current knowledge of the links between HIV-1 infection and immunometabolism, and we discuss the potential opportunities and challenges for therapeutic interventions.

Effect of a Nutritional Intervention on the Intestinal Microbiota of Vertically HIV-Infected Children: The Pediabiota Study

AIMS

The gut microbiota exerts a critical influence in the immune system. The gut microbiota of human virus immunodeficiency (HIV)-infected children remains barely explored. We aimed to characterize the fecal microbiota in vertically HIV-infected children and to explore the effects of its modulation with a symbiotic nutritional intervention.

METHODS

a pilot, double blind, randomized placebo-controlled study including HIV-infected children who were randomized to receive a nutritional supplementation including prebiotics and probiotics or placebo for four weeks. HIV-uninfected siblings were recruited as controls. The V3-V4 region of the 16S rRNA gene was sequenced in fecal samples.

RESULTS

22 HIV-infected children on antiretroviral therapy (ART) and with viral load (VL) <50/mL completed the follow-up period. Mean age was 11.4 ± 3.4 years, eight (32%) were male. Their microbiota showed reduced alpha diversity compared to controls and distinct beta diversity at the genus level (Adonis p = 0.042). Patients showed decreased abundance of commensals Faecalibacterium and an increase in Prevotella, Akkermansia and Escherichia. The nutritional intervention shaped the microbiota towards the control group, without a clear directionality.

CONCLUSIONS

Vertical HIV infection is characterized by changes in gut microbiota structure, distinct at the compositional level from the findings reported in adults. A short nutritional intervention attenuated bacterial dysbiosis, without clear changes at the community level.

SUMMARY

In a group of 24 vertically HIV-infected children, in comparison to 11 uninfected controls, intestinal dysbiosis was observed despite effective ART. Although not fully effective to restore the microbiota, a short intervention with pre/probiotics attenuated bacterial dysbiosis.

The gut microbiome and frailty

The human microbiome is constituted by an extensive network of organisms that lie at the host/environment interface and transduce signals that play vital roles in human health and disease across the lifespan. Frailty is a critical aging-related syndrome marked by diminished physiological reserve and heightened vulnerability to stress, predictive of major adverse clinical outcomes including death. While recent studies suggest the microbiome may impact key pathways critical to frailty pathophysiology, direct evaluation of the microbiome-frailty relationship remains limited. In this article, we review the complex interplay of biological, behavioral, and environmental factors that may influence shifts in gut microbiome composition and function in aging populations and the putative implications of such shifts for progression to frailty. We discuss HIV infection as a key prototype for elucidating the complex pathways via which the microbiome may precipitate frailty. Finally, we review considerations for future research efforts.

HIV-associated gut dysbiosis is independent of sexual practice and correlates with noncommunicable diseases

Loss of gut mucosal integrity and an aberrant gut microbiota are proposed mechanisms contributing to chronic inflammation and increased morbidity and mortality during antiretroviral-treated HIV disease. Sexual practice has recently been uncovered as a major source of microbiota variation, potentially confounding prior observations of gut microbiota alterations among persons with HIV (PWH). To overcome this and other confounding factors, we examine a well-powered subset of AGEhIV Cohort participants comprising antiretroviral-treated PWH and seronegative controls matched for age, body-mass index, sex, and sexual practice. We report significant gut microbiota differences in PWH regardless of sex and sexual practice including Gammaproteobacteria enrichment, Lachnospiraceae and Ruminococcaceae depletion, and decreased alpha diversity. Men who have sex with men (MSM) exhibit a distinct microbiota signature characterized by Prevotella enrichment and increased alpha diversity, which is linked with receptive anal intercourse in both males and females. Finally, the HIV-associated microbiota signature correlates with inflammatory markers including suPAR, nadir CD4 count, and prevalence of age-associated noncommunicable comorbidities.

Can gut microbiota of men who have sex with men influence HIV transmission?

Gaining a complete understanding of transmission risk factors will assist in efforts to reduce new HIV infections, especially within the disproportionally affected population of men who have sex with men (MSM). We recently reported that the fecal microbiota of MSM elevates immune activation in gnotobiotic mice and enhances HIV infection in vitro over that of fecal microbiota from men who have sex with women. We also demonstrated elevation of the gut homing marker CD103 (integrin αE) on CD4⁺ T cells by MSM-microbiota. Here we provide additional evidence that the gut microbiota is a risk factor for HIV transmission in MSM by showing elevated frequencies of the HIV co-receptor CCR5 on CD4⁺ T cells in human rectosigmoid colon biopsies. We discuss our interest in specific MSM-associated bacteria and propose the influx of CD103⁺ and CCR5⁺ CD4⁺ T cells into the colon as a potential link between the MSM microbiota and HIV transmission.