Associations between recent thymic emigrants and CD4+ T-cell recovery after short-term antiretroviral therapy initiation

Higher proportions of circulating CXCR3+ CCR6- Tfh cells as a hallmark of impaired CD4+ T-cell recovery in HIV-1-infected immunological non-responders

Despite long-term suppressive antiretroviral therapy (ART), immune dysregulation due to impaired reconstitution of CD4+ T cells is a major hurdle for reducing morbidity and mortality in HIV-1-infected immunological non-responders (INRs, CD4+ T cells ≤350 cells/µL). To evaluate potential immunological factors associated with impaired CD4+ T-cell reconstitution, we performed comprehensive immunophenotyping of multiple subsets of CD4+ T cells among HIV-1-infected individuals with high (>350 cells/µL) and low (≤350 cells/µL) CD4+ T cells, either ART-naïve or ART-exposed (median, 10 years). In comparison to other groups, INRs showed exclusively elevated proportions of CXCR3+ CCR6- Th1-like circulatory T follicular helper (cTfh1) CD4+ T cells, correlating negatively with CD4+ T cells (r = -0.6769, P < 0.0001), suggesting a strong association with incomplete CD4+ T-cell recovery. In contrast, compared to INRs, higher proportions of CXCR3- CCR6+ Th17-like cTfh cells (cTfh17) in immunological responders (IRs, CD4+ T cells >350 cells/µL) showed no correlation with CD4+ T-cell counts, suggesting a lack of association with CD4+ T-cell recovery. Additionally, proportions of activated (CD4+ CD38+ HLA-DR+) and regulatory (CD4+ CD25+/hi CD127-/lo) CD4+ T cells were increased in INRs compared to IRs, as previously known. A negative correlation was also observed between the CD4+ T-cell counts and activated (r = -0.6726, P < 0.0001) or regulatory (r = -0.5627, P < 0.0001) CD4+ T-cell proportions among IRs and INRs. Our study highlights that immune dysregulation associated with skewing of cTfh cells toward CXCR3+ CCR6- Th1-like phenotype may be the leading cause of inefficient CD4+ T-cell recovery in INRs and can serve as a hallmark of impaired CD4+ T-cell reconstitution.IMPORTANCEThe altered proportions of CD4+ T-cell subsets in immunological non-responders (INRs) indicate their involvement in poor CD4+ T-cell reconstitution. Reversing these alterations may help prevent the loss of CD4+ T cells. Particularly, blocking cTfh-cell polarization toward CXCR3+ CCR6- cTfh-cell subset may help restore CD4+ T-cell counts in INRs, thereby preventing increased risk of morbidity and mortality.

Insights to the HIV-associated visceral leishmaniasis clinical outcome: lessons learned about immune mediated disorders

Most cases of visceral leishmaniasis (VL) and human immunodeficiency virus (HIV) co-infection (VL/HIV) in the Americas occur in Brazil, and the prevalence of VL/HIV has been increasing since 2019, reaching 19% in 2023. This association presents a challenge for the management of VL, since both VL and HIV infection share immunopathogenic characteristics that can reciprocally affect co-infected patients. Thus, VL may contribute to the immunosuppression and other immunological disturbances associated with the rapid progression to acquired immunodeficiency syndrome (AIDS), whereas HIV infection accelerates the development of active VL and reduces the probability of a successful response to anti-Leishmania therapy, resulting in an increase in the relapse and lethality rates of VL. In this synergistic impairment, one of the most critical hallmarks of VL/HIV co-infection is the enhancement of immunosuppression and intense chronic immune activation, caused not only by each infection per se, but also by the cytokine storm and translocation of microbial products. Thus, co-infected patients present with an impaired effector immune response that may result in inefficient parasitic control. In addition, the chronic activation environment in VL/HIV patients may favor progression to early immunosenescence and exhaustion, worsening the patients' clinical condition and increasing the frequency of disease relapse. Herein, we review the immunological parameters associated with the immunopathogenesis of VL/HIV co-infection that could serve as good biomarkers of clinical prognosis in terms of relapse and severity of VL.

Systematic review and quantitative meta-analysis of age-dependent human T-lymphocyte homeostasis

Objective

To evaluate and quantitatively describe age-dependent homeostasis for a broad range of total T-cells and specific T-lymphocyte subpopulations in healthy human subjects.

Methods

A systematic literature review was performed to identify and collect relevant quantitative information on T-lymphocyte counts in human blood and various organs. Both individual subject and grouped (aggregated) data on T-lymphocyte observations in absolute and relative values were digitized and curated; cell phenotypes, gating strategies for flow cytometry analyses, organs from which observations were obtained, subjects' number and age were also systematically inventoried. Age-dependent homeostasis of each T-lymphocyte subpopulation was evaluated via a weighted average calculation within pre-specified age intervals, using a piece-wise equal-effect meta-analysis methodology.

Results

In total, 124 studies comprising 11722 unique observations from healthy subjects encompassing 20 different T-lymphocyte subpopulations - total CD45+ and CD3+ lymphocytes, as well as specific CD4+ and CD8+ naïve, recent thymic emigrants, activated, effector and various subpopulations of memory T-lymphocytes (total-memory, central-memory, effector-memory, resident-memory) - were systematically collected and included in the final database for a comprehensive analysis. Blood counts of most T-lymphocyte subpopulations demonstrate a decline with age, with a pronounced decrease within the first 10 years of life. Conversely, memory T-lymphocytes display a tendency to increase in older age groups, particularly after ~50 years of age. Notably, an increase in T-lymphocyte numbers is observed in neonates and infants (0 - 1 year of age) towards less differentiated T-lymphocyte subpopulations, while an increase into more differentiated subpopulations emerges later (1 - 5 years of age).

Conclusion

A comprehensive systematic review and meta-analysis of T-lymphocyte age-dependent homeostasis in healthy humans was performed, to evaluate immune T-cell profiles as a function of age and to characterize generalized estimates of T-lymphocyte counts across age groups. Our study introduces a quantitative description of the fundamental parameters characterizing the maintenance and evolution of T-cell subsets with age, based on a comprehensive integration of available organ-specific and systems-level flow cytometry datasets. Overall, it provides the most up-to-date view of physiological T-cell dynamics and its variance and may be used as a consistent reference for gaining further mechanistic understanding of the human immune status in health and disease.

The role of pyroptosis in incomplete immune reconstitution among people living with HIV：Potential therapeutic targets

Globally, HIV infection causes significant morbidity and mortality, and is a major public health problem. Despite the fact that widespread use of antiretroviral therapy (ART) has substantially altered the natural history of HIV infection from originally being a universally lethal disease to now being a chronic medical condition for those taking appropriate treatment, approximately 10-40% of people living with HIV (PLWH) who take effective ART and maintain long-term viral suppression fail to achieve normalization of CD4 + T-cell counts. This phenomenon is referred to as incomplete immune reconstitution or immunological non-response. Although the precise mechanisms underlying this outcome have not been elucidated, recent evidence indicates that excessive pyroptosis may play a crucial role in the development of incomplete immune reconstitution. Pyroptosis is characterized by the formation of pores in the cell membrane, cell rupture, and secretion of intracellular contents and pro-inflammatory cytokines, including IL-1β and IL-18. This excessive inflammation-induced programmed cell death leads to a massive loss of CD4 + T-cells, and inflammatory consequences that may promote and sustain incomplete immune reconstitution. Herein, we review the possible pathways activated in HIV infection by inflammasomes that act as switches of pyroptosis, and the role of pyroptosis in HIV, as well as the relevance of CD4 + T-cells in incomplete immune reconstitution. We also highlight the possible mechanisms of pyroptosis involved in incomplete immune reconstitution, thus paving the way for the development of potential targets for the treatment of incomplete immune reconstitution.

Distinct fecal microbial signatures are linked to sex and chronic immune activation in pediatric HIV infection

Introduction

Our understanding of HIV-associated gut microbial dysbiosis in children perinatally-infected with HIV (CLWH) lags behind that of adults living with HIV. Childhood represents a critical window for the gut microbiota. Any disturbances, including prolonged exposure to HIV, antiretroviral drugs, and antibiotics are likely to have a significant impact on long-term health, resulting in a less resilient gut microbiome. The objective of our study was to characterize the gut microbiota in CLWH, and compare it with HIV-unexposed and -uninfected children.

Methods

We enrolled 31 children aged 3 to 15 years; 15 were CLWH and 16 were HUU. We assessed dietary patterns and quality; quantified soluble and cellular markers of HIV disease progression by flow cytometry, enzyme-linked immunosorbent and multiplex-bead assays, and profiled the gut microbiota by 16S rRNA sequencing. We explored relationships between the gut microbiota, antibiotic exposure, dietary habits, soluble and cellular markers and host metadata.

Results

Children had a Western-type diet, their median health eating index score was 67.06 (interquartile range 58.76-74.66). We found no discernable impact of HIV on the gut microbiota. Alpha diversity metrics did not differ between CLWH and HUU. Sex impacted the gut microbiota (R-squared= 0.052, PERMANOVA p=0.024). Male children had higher microbial richness compared with female children. Two taxa were found to discriminate female from male children independently from HIV status: Firmicutes for males, and Bacteroides for females. Markers of HIV disease progression were comparable between CLWH and HUU, except for the frequency of exhausted CD4+ T cells (PD-1+) which was increased in CLWH (p=0.0024 after adjusting for confounders). Both the frequency of exhausted CD4+ and activated CD4+ T cells (CD38+ HLADR+) correlated positively with the relative abundance of Proteobacteria (rho=0.568. false discovery rate (FDR)-adjusted p= 0.029, and rho=0.62, FDR-adjusted p=0.0126, respectively).

Conclusion

The gut microbiota of CLWH appears similar to that of HUU, and most markers of HIV disease progression are normalized with long-term ART, suggesting a beneficial effect of the latter on the gut microbial ecology. The relationship between exhausted and activated CD4+ T cells and Proteobacteria suggests a connection between the gut microbiome, and premature aging in CLWH.

Recent advances in poor HIV immune reconstitution: what will the future look like?

Combination antiretroviral therapy has demonstrated proved effectiveness in suppressing viral replication and significantly recovering CD4+ T cell count in HIV type-1 (HIV-1)-infected patients, contributing to a dramatic reduction in AIDS morbidity and mortality. However, the factors affecting immune reconstitution are extremely complex. Demographic factors, co-infection, baseline CD4 cell level, abnormal immune activation, and cytokine dysregulation may all affect immune reconstitution. According to report, 10-40% of HIV-1-infected patients fail to restore the normalization of CD4+ T cell count and function. They are referred to as immunological non-responders (INRs) who fail to achieve complete immune reconstitution and have a higher mortality rate and higher risk of developing other non-AIDS diseases compared with those who achieve complete immune reconstitution. Heretofore, the mechanisms underlying incomplete immune reconstitution in HIV remain elusive, and INRs are not effectively treated or mitigated. This review discusses the recent progress of mechanisms and factors responsible for incomplete immune reconstitution in AIDS and summarizes the corresponding therapeutic strategies according to different mechanisms to improve the individual therapy.

Treg Cell Evaluation in Patients with Acquired Immune Deficiency Syndrome with Poor Immune Reconstitution and Human Immunodeficiency Virus-Infected Treg Cell Prevention by Polymeric Nanoparticle Drug Delivery System

To better deliver antiretroviral drugs for treating patients with acquired immune deficiency syndrome (AIDS) with poor immune reconstitution, a novel nanopole capsule was designed in this study. Forty-eight patients with AIDS with poor immune reconstitution were chosen as subjects to test their immune state. CD4⁺ T and Regulatory T cells (Treg) infected with HIV were cultured to test polyethyleneimine (PEI) and polychitosan (PC) drug delivery system efficiency. The infiltration efficiency test was performed to study the drug delivery efficiency of the delivery systems, and the cell numbers of CD4⁺ T and Treg cells infected with HIV were calculated to evaluate the therapeutic effect. The results showed that patients with AIDS with poor immune reconstitution had lower CD4⁺ T cell count and higher Treg cell count. Furthermore, the infiltration efficiency of the PC drug delivery system was higher than that of the PEI drug delivery system, and the therapy efficiency of antiretroviral drugs was greatly improved in the PC group. Additionally, the improvement of CD4⁺ T and Treg cells damaged by HIV was greater in the PC group. Sequentially, the PC system can better deliver and release loaded antiretroviral drugs and may be a better choice for treating patients with AIDS with poor immune reconstitution in the future.

Immunological factors, but not clinical features, predict visceral leishmaniasis relapse in patients co-infected with HIV

Visceral leishmaniasis (VL) has emerged as a clinically important opportunistic infection in HIV patients, as VL/HIV co-infected patients suffer from frequent VL relapse. Here, we follow cohorts of VL patients with or without HIV in Ethiopia. By the end of the study, 78.1% of VL/HIV-but none of the VL patients-experience VL relapse. Despite a clinically defined cure, VL/HIV patients maintain higher parasite loads, lower BMI, hepatosplenomegaly, and pancytopenia. We identify three immunological markers associated with VL relapse in VL/HIV patients: (1) failure to restore antigen-specific production of IFN-γ, (2) persistently lower CD4+ T cell counts, and (3) higher expression of PD1 on CD4+ and CD8+ T cells. We show that these three markers, which can be measured in primary hospital settings in Ethiopia, combine well in predicting VL relapse. The use of our prediction model has the potential to improve disease management and patient care.