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.

Background CD4+ T cell counts in certain human immunodeficiency virus (HIV)-infected patients called immunological non-responders (INRs) could not return to a normal level even with sustained antiretroviral therapy (ART) because of persistent immune activation, which is associated with pro-inflammatory cytokines production and an altered intestinal microbiome profile. Changes in gut bacterial composition have been linked to low CD4+ T cell counts in HIV-infected individuals. However, the association between CD4+ T cell counts and gut microbiota community composition and cytokines levels in INRs (CD4+ T cell counts < 500 cells/μL) from Yunnan Province, China, has not been previously investigated. Methods To address this issue, we carried out a cross-sectional study of 34 HIV-infected INRs. The patients were divided into CD4 count > 200 cells/μL group and CD4 count < 200 cells/μL group. The gut microbiota composition of each subject was analyzed by 16S rRNA gene sequencing. We also compared CD8+ T cell counts, pro-inflammatory cytokines levels, and nutritional status between the two groups. Results Compared to INRs with CD4 count > 200 cells/μL, those with CD4 count < 200 cells/μL had a lower CD4/CD8 ratio, lower nutritional status and higher serum levels of tumor necrosis factor (TNF)-α, interferon-γ-inducible protein (IP)-10 and interleukin (IL)-1α. Ruminococcaceae was less abundant in the CD4 count < 200 cells/μL group than in the CD4 count > 200 cells/μL group, and difference in alpha diversity was observed between the two groups. Moreover, CD4+ T cell counts were negatively associated with TNF-α and IL-1α levels and positively associated with the relative abundance of Ruminococcaceae. Conclusions Our study demonstrated that lower CD4+ T cell counts in INRs are associated with a reduced abundance of Ruminococcaceae in the gut and elevated serum pro-inflammatory cytokines levels. Thus, interventions targeting gut microbiota to increase CD4+ T cell counts are a potential strategy for promoting immune reconstitution in HIV-infected INRs.

Gastrointestinal probiotics play an important role in maintaining intestinal bacteria homeostasis. They might benefit people with human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), which remains a global health challenge. However, there is a controversy regarding the efficacy of probiotics for the treatment of AIDS. This study systematically reviewed the evidence of the effects of existing probiotic interventions on AIDS and sought to provide information on the role of probiotics in the treatment of HIV/AIDS patients. A meta-analysis of studies identified by screening multiple databases was performed using a fixed-effects model in Review Manager 5.2 software. The meta-analysis showed that probiotics could reduce the incidence of AIDS-related diarrhea (RR = 0.60 (95% CI: 0.44–0.82), p = 0.001). The short-term use of probiotics (supplementation duration shorter than 30 days) did not reduce the incidence of diarrhea (RR = 0.76 (95% CI: 0.51–1.14), p = 0.19), while the long-term use of probiotics (supplementation duration longer than 30 days) reduced diarrhea (RR = 0.47 (95% CI: 0.29–0.76), p = 0.002). Probiotics had no effect on CD4 cell counts in HIV/AIDS patients (MD = 21.24 (95% CI: −12.95–55.39), p = 0.22). Our data support that probiotics were associated with an obvious reduction in AIDS-related diarrhea, which indicates the need for additional research on this potential preventive strategy for AIDS.

AIDS patients with immune non-response are prone to malnutrition, intestinal barrier damage, thus aggravating chronic immune activation and inflammation. However, nutritional interventions targeting malnutrition may be beneficial to restore immune function, improve clinical outcomes, and reduce mortality remains largely unclear. This work aimed to evaluate the efficacy of a nutritional supplement in HIV-infected immune non-responders (INRs). The subjects received oral supplementation of a pre-digested protein nutrition formula for three months. We show that the CD4+ T and CD8+ T cell counts were significantly increased after supplementation of the pre-digested enteral nutritional supplement. Among all pro-inflammatory cytokines in the serum, only IL-1β level was significantly decreased, while TNF-β was significantly increased (P &lt; 0.05). The levels of intestinal mucosal damage markers, diamine oxidase (DAO), D-lactic acid (D-lactate), and lipopolysaccharide (LPS), decreased significantly (P &lt; 0.05) after the nutritional intervention. Moreover, at month 3 after the intervention, the body weight, body mass index, albumin, and hemoglobin of all subjects were significantly increased (P &lt; 0.05). The correlation analysis demonstrated a significantly negative correlation of CD4+ T cell count with levels of DAO (r = -0.343, P = 0.004), D-lactate (r = -0.250, P = 0.037), respectively, and a significantly positive correlation of IL-1β level with levels of DAO (r = 0.445, P &lt; 0.001), D-lactate (r = 0.523, P &lt; 0.001), and LPS (r = 0.622, P &lt; 0.001). We conclude that the pre-digested enteral nutrition supplement is effective for HIV-infected INRs.

Coronavirus disease 2019 (COVID-19) is a highly infectious epidemic disease that has seriously affected human health worldwide. To date, however, there is still no definitive drug for the treatment of COVID-19. Cell-based therapies could represent a new breakthrough. Over the past several decades, mesenchymal stromal cells (MSCs) have proven to be ideal candidates for the treatment of many viral infectious diseases due to their immunomodulatory and tissue repair or regeneration promoting properties, and several relevant clinical trials for the treatment of COVID-19 have been registered internationally. Herein, we systematically summarize the clinical efficacy of MSCs in the treatment of COVID-19 based on published results, including mortality, time to symptom improvement, computed tomography (CT) imaging, cytokines, and safety, while elaborating on the possible mechanisms underpinning the effects of MSCs, to provide a reference for subsequent studies.