Foxp3+Helios+ regulatory T cells are associated with monocyte subsets and their PD-1 expression during acute HIV-1 infection

Revisiting regulatory T cells as modulators of innate immune response and inflammatory diseases

Regulatory T cells (Treg) are known to be critical for the maintenance of immune homeostasis by suppressing the activation of auto- or allo-reactive effector T cells through a diverse repertoire of molecular mechanisms. Accordingly, therapeutic strategies aimed at enhancing Treg numbers or potency in the setting of autoimmunity and allogeneic transplants have been energetically pursued and are beginning to yield some encouraging outcomes in early phase clinical trials. Less well recognized from a translational perspective, however, has been the mounting body of evidence that Treg directly modulate most aspects of innate immune response under a range of different acute and chronic disease conditions. Recognizing this aspect of Treg immune modulatory function provides a bridge for the application of Treg-based therapies to common medical conditions in which organ and tissue damage is mediated primarily by inflammation involving myeloid cells (mononuclear phagocytes, granulocytes) and innate lymphocytes (NK cells, NKT cells, γδ T cells and ILCs). In this review, we comprehensively summarize pre-clinical and human research that has revealed diverse modulatory effects of Treg and specific Treg subpopulations on the range of innate immune cell types. In each case, we emphasize the key mechanistic insights and the evidence that Treg interactions with innate immune effectors can have significant impacts on disease severity or treatment. Finally, we discuss the opportunities and challenges that exist for the application of Treg-based therapeutic interventions to three globally impactful, inflammatory conditions: type 2 diabetes and its end-organ complications, ischemia reperfusion injury and atherosclerosis.

Assessment of CD39 expression in regulatory T cell subsets by disease severity in adult and juvenile COVID -19 cases

COVID‐19 is a disease characterized by acute respiratory failure and is a major health problem worldwide. Here, we aimed to investigate the role of CD39 expression in Treg cell subsets in COVID‐19 immunopathogenesis and its relationship to disease severity. One hundred and ninety COVID‐19 patients (juveniles, adults) and 43 volunteers as healthy controls were enrolled in our study. Flow cytometric analysis was performed using a 10‐color monoclonal antibody panel from peripheral blood samples. In adult patients, CD39⁺ Tregs increased with disease severity. In contrast, CD39⁺ Tregs were decreased in juvenile patients in an age‐dependent manner. Overall, our study reveals an interesting profile of CD39‐expressing Tregs in adult and juvenile cases of COVID‐19. Our results provide a better understanding of the possible role of Tregs in the mechanism of immune response in COVID‐19 cases.

CD39⁺ Tregs increased with disease severity in adult COVID‐19 cases. In addition, significant changes were also observed in other Treg subsets.

Treg subsets in the juvenile COVID‐19 cases showed age‐related variability but were significantly lower than in the healthy control group.

Consistent correlations were found between laboratory findings in adult COVID‐19 cases and Treg subsets.

OUP accepted manuscript

Glial cell activation is a hallmark of several neurodegenerative and neuroinflammatory diseases. During HIV infection, neuroinflammation is associated with cognitive impairment, even during sustained long-term suppressive antiretroviral therapy. However, the cellular subsets contributing to neuronal damage in the CNS during HIV infection remain unclear.

Using post-mortem brain samples from eight HIV patients and eight non-neurological disease controls, we identify a subset of CNS phagocytes highly enriched in LGALS3, CTSB, GPNMB and HLA-DR, a signature identified in the context of ageing and neurodegeneration.

In HIV patients, the presence of this phagocyte phenotype was associated with synaptic stripping, suggesting an involvement in the pathogenesis of HIV-associated neurocognitive disorder.

Taken together, our findings elucidate some of the molecular signatures adopted by CNS phagocytes in HIV-positive patients and contribute to the understanding of how HIV might pave the way to other forms of cognitive decline in ageing HIV patient populations.

Acute HIV-1 and SARS-CoV-2 Infections Share Slan+ Monocyte Depletion-Evidence from an Hyperacute HIV-1 Case Report

Monocytes are key modulators in acute viral infections, determining both inflammation and development of specific B- and T-cell responses. Recently, these cells were shown to be associated to different SARS-CoV-2 infection outcome. However, their role in acute HIV-1 infection remains unclear. We had the opportunity to evaluate the mononuclear cell compartment in an early hyper-acute HIV-1 patient in comparison with an untreated chronic HIV-1 and a cohort of SARS-CoV-2 infected patients, by high dimensional flow cytometry using an unsupervised approach. A distinct polarization of the monocyte phenotype was observed in the two viral infections, with maintenance of pro-inflammatory M1-like profile in HIV-1, in contrast to the M2-like immunosuppressive shift in SARS-CoV-2. Noticeably, both acute infections had reduced CD14^low/−CD16⁺ non-classical monocytes, with depletion of the population expressing Slan (6-sulfo LacNac), which is thought to contribute to immune surveillance through pro-inflammatory properties. This depletion indicates a potential role of these cells in acute viral infection, which has not previously been explored. The inflammatory state accompanied by the depletion of Slan+ monocytes may provide new insights on the critical events that determine the rate of viral set-point in acute HIV-1 infection and subsequent impact on transmission and reservoir establishment.

Detection of Immune Checkpoint Receptors - A Current Challenge in Clinical Flow Cytometry

Immunological therapy principles are increasingly determining modern medicine. They are used to treat diseases of the immune system, for tumors, but also for infections, neurological diseases, and many others. Most of these therapies base on antibodies, but small molecules, soluble receptors or cells and modified cells are also used. The development of immune checkpoint inhibitors is amazingly fast. T-cell directed antibody therapies against PD-1 or CTLA-4 are already firmly established in the clinic. Further targets are constantly being added and it is becoming increasingly clear that their expression is not only relevant on T cells. Furthermore, we do not yet have any experience with the long-term systemic effects of the treatment. Flow cytometry can be used for diagnosis, monitoring, and detection of side effects. In this review, we focus on checkpoint molecules as target molecules and functional markers of cells of the innate and acquired immune system. However, for most of the interesting and potentially relevant parameters, there are still no test kits suitable for routine use. Here we give an overview of the detection of checkpoint molecules on immune cells in the peripheral blood and show examples of a possible design of antibody panels.

Differences in Maturation Status and Immune Phenotypes of Circulating Helios+ and Helios- Tregs and Their Disrupted Correlations With Monocyte Subsets in Autoantibody-Positive T1D Individuals

CD4 Tregs are involved in the regulation of various autoimmune diseases but believed to be highly heterogeneous. Studies have indicated that Helios controls a distinct subset of functional Tregs. However, the immunological changes in circulating Helios⁺ and Helios⁻ Tregs are not fully explored in type 1 diabetes (T1D). Here, we elucidated the differences in maturation status and immune regulatory phenotypes of Helios⁺ and Helios⁻ Tregs and their correlations with monocyte subsets in T1D individuals. As CD25^−/low FOXP3⁺ Tregs also represent a subset of functional Tregs, we defined Tregs as FOXP3⁺CD127^−/low and examined circulating Helios⁺ and Helios⁻ Treg subpopulations in 68 autoantibody-positive T1D individuals and 68 age-matched healthy controls. We found that expression of both FOXP3 and CTLA4 diminished in Helios⁻ Tregs, while the proportion of CD25^−/low Tregs increased in Helios⁺ Tregs of T1D individuals. Although the frequencies of neither Helios⁺ nor Helios⁻ Tregs were affected by investigated T1D genetic risk loci, Helios⁺ Tregs correlated with age at T1D diagnosis negatively and disease duration positively. Moreover, the negative correlation between central and effector memory proportions of Helios⁺ Tregs in healthy controls was disrupted in T1D individuals. Finally, regulatory non-classical and intermediate monocytes also decreased in T1D individuals, and positive correlations between these regulatory monocytes and Helios⁺/Helios⁻ Treg subsets in healthy controls disappeared in T1D individuals. In conclusion, we demonstrated the alternations in maturation status and immune phenotypes in Helios⁺ and Helios⁻ Treg subsets and revealed the missing association between these Treg subsets and monocyte subsets in T1D individuals, which might point out another option for elucidating T1D mechanisms.

Evolution and Diversity of Immune Responses during Acute HIV Infection

Understanding the earliest immune responses following HIV infection is critical to inform future vaccines and therapeutics. Here, we review recent prospective human studies in at-risk populations that have provided insight into immune responses during acute infection, including additional relevant data from non-human primate (NHP) studies. We discuss the timing, nature, and function of the diverse immune responses induced, the onset of immune dysfunction, and the effects of early anti-retroviral therapy administration. Treatment at onset of viremia mitigates peripheral T and B cell dysfunction, limits seroconversion, and enhances cellular antiviral immunity despite persistence of infection in lymphoid tissues. We highlight pertinent areas for future investigation, and how application of high-throughput technologies, alongside targeted NHP studies, may elucidate immune response features to target in novel preventions and cures.