How can the gut microbiota affect immune recovery in HIV-infected individuals?

Influence of HIV infection on cognition and overall intelligence in HIV-infected individuals: advances and perspectives

It is now well understood that HIV-positive individuals, even those under effective ART, tend to develop a spectrum of cognitive, motor, and/or mood conditions which are contemporarily referred to as HIV-associated neurocognitive disorder (HAND), and which is directly related to HIV-1 infection and HIV-1 replication in the central nervous system (CNS). As HAND is known to induce difficulties associated with attention, concentration, and memory, it is thus legitimate and pertinent to speculate upon the possibility that HIV infection may well influence human cognition and intelligence. We therefore propose herein to review the concept of intelligence, the concept of cells of intelligence, the influence of HIV on these particular cells, and the evidence pointing to differences in observed intelligence quotient (IQ) scores between HIV-positive and HIV-negative individuals. Additionally, cumulative research evidence continues to draw attention to the influence of the gut on human intelligence. Up to now, although it is known that HIV infection profoundly alters both the composition and diversity of the gut microbiota and the structural integrity of the gut, the influence of the gut on intelligence in the context of HIV infection remains poorly described. As such, we also provide herein a review of the different ways in which HIV may influence human intelligence via the gut-brain axis. Finally, we provide a discourse on perspectives related to HIV and human intelligence which may assist in generating more robust evidence with respect to this issue in future studies. Our aim is to provide insightful knowledge for the identification of novel areas of investigation, in order to reveal and explain some of the enigmas related to HIV infection.

Fecal Microbiota Transplantation for People Living with Human Immunodeficiency Virus: A Scoping Review

The aim of this scoping review was to determine the characteristics of studies evaluating fecal microbiota transplantation (FMT), as well as its effects and safety as a therapeutic intervention for people living with human immunodeficiency virus (HIV). We conducted a scoping review following the methodology of the Joanna Briggs Institute. We searched the following databases: PubMed, Web of Science, Scopus, Embase, Cochrane Library, and Medline until September 19, 2021. Studies that used FMT in people living with HIV and explored its effects on the health of these people were included. Two randomized and 2 uncontrolled clinical trials with a total of 55 participants were included. Participants were well-controlled HIV-infected people. Regarding microbiota changes, three studies found significant post-FMT increases in Fusobacterium, Prevotella, α-diversity, Chao index, and/or Shannon index, and/or decreases in Bacteroides. Regarding markers of intestinal damage, one study found a decrease in intestinal fatty acid binding protein post-FMT, and another study found an increase in zonulin. Other outcomes evaluated by the studies were as follows: markers of immune and inflammatory activation, markers of immunocompetence (CD4⁺, and CD8⁺ T lymphocytes), and HIV viral load; however, none showed significant changes. Clinical outcomes were not evaluated by these studies. Regarding the safety of FMT, only mild adverse events were appreciated. No serious adverse event was reported. The clinical evidence for FMT in people living with HIV is sparse. FMT appears to have good tolerability and, no serious adverse event has been reported so far. Further clinical trials and evaluation of clinically important biomedical outcomes for FMT in people living with HIV are needed.

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

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

Regulation of Gut Microbiota on Immune Reconstitution in Patients With Acquired Immunodeficiency Syndrome

Human immunodeficiency virus type 1 (HIV-1) infection of CD4⁺ T cells in the gut plays an insidious role in acquired immunodeficiency syndrome (AIDS) pathogenesis. Host immune function is closely related to gut microbiota. Changes in the gut microbiota cause a different immune response. Previous studies revealed that HIV-1 infection caused changes in gut microbiota, which induced immune deficiency. HIV-1 infection results in an abnormal composition and function of the gut microbiota, which may disrupt the intestinal epithelial barrier and microbial translocation, leading to long-term immune activation, including inflammation and metabolic disorders. At the same time, an abnormal gut microbiota also hinders the effect of antiviral therapy and affects the immune reconstruction of patients. However, studies on the impact of the gut microbiota on immune reconstitution in patients with HIV/AIDS are still limited. In this review, we focus on changes in the gut microbiota caused by HIV infection, as well as the impact and regulation of the gut microbiota on immune function and immune reconstitution, while we also discuss the potential impact of probiotics/prebiotics and fecal microbiota transplantation (FMT) on immune reconstitution.

Enrichment of gut-derived Fusobacterium is associated with suboptimal immune recovery in HIV-infected individuals

We explored the gut microbiota profile among HIV-infected individuals with diverse immune recovery profiles following long-term suppressive ART and investigated the relationship between the altered bacteria with markers of immune dysfunction. The microbiota profile of rectal swabs from 26 HIV-infected individuals and 20 HIV-uninfected controls were examined. Patients were classified as suboptimal responders, sIR (n = 10, CD4 T-cell <350 cells/ul) and optimal responders, oIR (n = 16, CD4 T-cell >500 cells/ul) after a minimum of 2 years on suppressive ART. Canonical correlation analysis(CCA) and multiple regression modelling were used to explore the association between fecal bacterial taxa abundance and immunological profiles in optimal and suboptimal responders. We found Fusobacterium was significantly enriched among the HIV-infected and the sIR group. CCA results showed that Fusobacterium abundance was negatively correlated with CD4 T-cell counts, but positively correlated with CD4 T-cell activation and CD4 Tregs. Multiple linear regression analysis adjusted for age, baseline CD4 T-cell count, antibiotic exposure and MSM status indicated that higher Fusobacterium relative abundance was independently associated with poorer CD4 T-cell recovery following ART. Enrichment of Fusobacterium was associated with reduced immune recovery and persistent immune dysfunction following ART. Modulating the abundance of this bacterial taxa in the gut may be a viable intervention to improve immune reconstitution in our setting.

Effects of HIV, antiretroviral therapy and prebiotics on the active fraction of the gut microbiota

OBJECTIVE

In a recent blinded randomized study, we found that in HIV-infected individuals a short supplementation with prebiotics (scGOS/lcFOS/glutamine) ameliorates dysbiosis of total gut bacteria, particularly among viremic untreated patients. Our study goal was to determine the fraction of the microbiota that becomes active during the intervention and that could provide additional functional information.

DESIGN

A total of six healthy individuals, and 16 HIV-infected patients comprising viremic untreated patients (n = 5) and antiretroviral therapy-treated patients that are further divided into immunological responders (n = 7) and immunological nonresponders (n = 4) completed the 6-week course of prebiotic treatment, including six patients receiving a placebo.

METHODS

Alpha and beta diversity of potentially active and total gut microbiota was evaluated using shotgun proteomics and 16S rRNA gene sequencing.

RESULTS

HIV infection decreased dormancy and increased alpha diversity of active bacteria in comparison with the healthy controls, whose richness was not further influenced by the prebiotic intervention. The effect of the prebiotics was most evident at the beta-diversity of active bacteria, particularly within viremic untreated patients. We found that the prebiotics did not only ameliorate dysbiosis of total bacteria in viremic untreated patients but also increased the abundance of active bacteria with strong immunomodulatory properties and amino acids metabolism, namely Bifidobacteriaceae, at similar levels to those in healthy individuals. This effect was attenuated in ART-treated individuals.

CONCLUSION

The effect of prebiotics was greater among ART-naive HIV-infected individuals than in ART-treated patients and healthy controls. This highlights the importance of therapies aimed at manipulating the microbiome in this group of patients.

Synbiotics for Improved Human Health: Recent Developments, Challenges, and Opportunities

Research on combining pro- and prebiotics as synbiotics to enhance human and animal health has accelerated in the past 10 years, including many clinical trials that have assessed a diverse range of synbiotic formulations. In this review, we summarize these studies as well as the commercial applications of synbiotics that are available. In particular, we critically assess the claimed health benefits of synbiotic applications and the ecological and therapeutic factors to consider when designing synbiotics and discuss the implications of these concepts for future research in this field.