On the Usefulness of Circulating Bacterial 16S rDNA as a Marker of Microbial Translocation in HIV-1–Infected Patients

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.

Blood Bacterial Profiles Associated With Human Immunodeficiency Virus Infection and Immune Recovery

Human immunodeficiency virus (HIV) infection impairs mucosal immunity and leads to bacterial translocation, fueling chronic inflammation and disease progression. While this is well established, questions remain about the compositional profile of the translocated bacteria, and to what extent it is influenced by antiretroviral therapy (ART). Using 16S ribosomal DNA targeted sequencing and shotgun proteomics, we showed that HIV increases bacterial translocation from the gut to the blood. HIV increased alpha diversity in the blood, which was dominated by aerobic bacteria belonging to Micrococcaceae (Actinobacteria) and Pseudomonadaceae (Proteobacteria) families, and the number of circulating bacterial proteins was also increased. Forty-eight weeks of ART attenuated this phenomenon. We found that enrichment with Lactobacillales order, and depletion of Actinobacteria class and Moraxellaceae and Corynebacteriacae families, were significantly associated with greater immune recovery and correlated with several inflammatory markers. Our findings suggest that the molecular cross talk between the host and the translocated bacterial products could influence ART-mediated immune recovery.

Effects of Co-Trimoxazole on Microbial Translocation in HIV-1-Infected Patients Initiating Antiretroviral Therapy

Microbial translocation (MT) contributes to immune activation during HIV-1 infection, and persists after initiation of antiretroviral therapy (ART). We investigated whether levels of MT markers are influenced by the use of co-trimoxazole (TMP-SMX) in HIV-1 patients. Plasma samples were obtained from HIV-1-infected patients initiating ART with (n=13) or without (n=13) TMP-SMX prophylaxis. Markers of MT [lipopolysaccharide-binding protein (LBP), lipopolysaccharide (LPS), soluble CD14 (sCD14), and intestinal fatty acid binding protein (I-FABP)] were assessed at baseline (BL), at 1 month, and at 1 year by the Limulus Amebocyte Lysate Assay or ELISA. BL levels of LBP were elevated in both categories of patients; they were highest in patients starting ART and TMP-SMX (median, μg/ml: 36.7 vs. 4.3, respectively, p=0.001) and correlated inversely with CD4(+) T cell counts (ρ=-0.65; p=0.005). Patients receiving ART and TMP-SMX had a significant reduction in LBP between BL and 1 year (median, μg/ml: 36.7 vs. 11.1; p=0.003). In contrast, levels of LPS at BL were lower in patients starting ART and TMP-SMX compared to those without TMP-SMX (median, pg/ml: 221 vs. 303 respectively; p=0.002) and did not change at 1 year. The increased BL levels of sCD14 had declined in both groups at 1 year. No difference in I-FABP levels was found between BL and 1 year. Concomitant use of ART and TMP-SMX reduces microbial translocation markers LBP and sCD14, probably due to its impact on the gut microbiota. Effective ART for 1 year does not restore gut-blood barrier dysfunction.