HIV Infection and Persistence in Pulmonary Mucosal Double Negative T Cells In Vivo

Pulmonary comorbidities in people with HIV- the microbiome connection

PURPOSE OF REVIEW

To report recent evidence on associations between human microbiome, particularly airway and gut, and pulmonary comorbidities in people with HIV (PWH). Furthermore, we explore how changes in the microbiome may contribute to pulmonary immune dysregulation and higher rates of pulmonary comorbidities among PWH. Finally, we propose future directions in the field.

RECENT FINDINGS

Increased risk of pulmonary comorbidities and rapid lung function decline have been reported in even well treated PWH. Altered microbiota profiles have been reported in PWH with pulmonary comorbidities and rapid lung function decline as compared to those without. The most consistent data have been the association between HIV-related pulmonary comorbidities, lung and oral microbiota dysbiosis, which has been also associated with distinct respiratory mucosal inflammatory profiles and short-term mortality. However, a possible causal link remains to be elucidated.

SUMMARY

Associations between the lung and oral microbiome, HIV-associated pulmonary comorbidities and rapid lung function decline have been reported in recent studies. Yet the underlying mechanism underpinning the observed associations is largely unknown and substantial knowledge gaps remain. Future research is warranted to unveil the role and mechanism of human microbiome from different anatomical compartments in relation to pulmonary comorbidities in PWH.

Dynamics of pulmonary mucosal cytotoxic CD8 T-cells in people living with HIV under suppressive antiretroviral therapy

BACKGROUND

Despite the success of antiretroviral therapy (ART), people living with HIV (PLWH) suffer from a high burden of pulmonary diseases, even after accounting for their smoking status. Cytotoxic CD8 T-cells are likely implicated in this phenomenon and may act as a double-edged sword. While being essential in viral infection control, their hyperactivation can also contribute to lung mucosal tissue damage. The effects of HIV and smoking on pulmonary mucosal CD8 T-cell dynamics has been a neglected area of research, which we address herein.

METHODS

Bronchoalveolar lavage (BAL) fluid were obtained from ART-treated PLWH (median duration of supressed viral load: 9 years; smokers: n = 14; non-smokers: n = 21) and HIV-uninfected controls (smokers: n = 11; non-smokers: n = 20) without any respiratory symptoms or active infection. Lymphocytes were isolated and CD8 T-cell subsets and homing markers were characterized by multiparametric flow cytometry.

RESULTS

Both smoking and HIV infection were independently associated with a significant increase in frequencies of total pulmonary mucosal CD8 T-cell. BAL CD8 T-cells were primarily CD69 + expressing CD103 and/or CD49a, at least one of the two granzymes (GzmA/GzmB), and little Perforin. Higher expression levels of CD103, CD69, and GzmB were observed in smokers versus non-smokers. The ex vivo phenotype of GzmA + and GzmB + cells revealed increased expression of CD103 and CXCR6 in smokers, while PLWH displayed elevated levels of CX3CR1 compared to controls.

CONCLUSION

Smoking and HIV could promote cytotoxic CD8 T-cell retention in small airways through different mechanisms. Smoking likely increases recruitment and retention of GzmB + CD8 Trm via CXCR6 and CD103. Heightened CX3CR1 expression could be associated with CD8 non-Trm recruitment from the periphery in PLWH.

Near full-length HIV sequencing in multiple tissues collected postmortem reveals shared clonal expansions across distinct reservoirs during ART

HIV persists in tissues during antiretroviral therapy (ART), but the relative contribution of different anatomical compartments to the viral reservoir in humans remains unknown. We performed an extensive characterization of HIV reservoirs in two men who donated their bodies to HIV cure research and who had been on suppressive ART for years. HIV DNA is detected in all tissues, with large variations across anatomical compartments and between participants. Intact HIV genomes represent 2% and 25% of all proviruses in the two participants and are mainly detected in secondary lymphoid organs, with the spleen and mediastinal lymph nodes harboring intact viral genomes in both individuals. Multiple copies of identical HIV genomes are found in all tissues, indicating that clonal expansions are common in anatomical sites. The majority (>85%) of these expanded clones are shared across multiple tissues. These findings suggest that infected cells expand, migrate, and possibly circulate between anatomical sites.

Blocking activation of CD4-CD8- T cells modulates their cytotoxic potential and decreases the expression of inflammatory and chemotactic receptors

CD4-CD8- (double negative - DN) T cells represent a small fraction of circulating T lymphocytes but are a major source of pro-inflammatory cytokines in patients with infectious diseases, including chronic Chagas cardiomyopathy (CCC), one of the deadliest cardiopathies known. Chagas disease is caused by an infection with the protozoan parasite Trypanosoma cruzi and can lead to either an asymptomatic form or a high-mortality cardiac disease. While circulating DN T cells represent a major inflammatory cytokine-expressing cell population in Chagas disease, their potential to be recruited to the heart and to perform cytotoxicity has not been determined. Our previous studies showed that blocking DN T cell activation decreases the expression of IFN-gamma, a cytokine involved in the severity of CCC. Here, studying a well-characterized cohort of Chagas patients with CCC or the asymptomatic form of Chagas disease (indeterminate form, IND), we evaluated the expression of cytotoxic molecules, cytokine and chemokine receptors in γδ+ and αβ+ DN T cells by multiparameter flow cytometry, and investigated whether blocking the activation of DN T cells influences the expression of these molecules. We observed that DN T cells from CCC display a higher expression of granzyme A, perforin, inflammatory molecules, and inflammatory chemokine receptors than cells from IND. Messenger RNA coding for these molecules is also upregulated in the heart of CCC patients. Importantly, blocking the activation of DN T cells from CCC modulates their cytotoxic potential and the expression of inflammatory and of chemokine receptors, suggesting that targeting DN T cell activation may be a valid strategy to reduce recruitment to the heart, inflammation, cytotoxicity and, thereby diminish CCC progression and severity.

HIV Tissue Reservoirs: Current Advances in Research

Acquired immunodeficiency syndrome (AIDS), caused by the human immunodeficiency virus (HIV), has become a heavy burden of disease and an important public health problem in the world. Although current antiretroviral therapy (ART) is effective at suppressing the virus in the blood, HIV still remains in two different types of reservoirs-the latently infected cells (represented by CD4⁺ T cells) and the tissues containing those cells, which may block access to ART, HIV-neutralizing antibodies and latency-reversing agents. The latter is the focus of our review, as blood viral load drops below detectable levels after ART, a deeper and more systematic understanding of the HIV tissue reservoirs is imperative. In this review, we take the lymphoid system (including lymph nodes, gut-associated lymphoid tissue, spleen and bone marrow), nervous system, respiratory system, reproductive system (divided into male and female), urinary system as the order, focusing on the particularity and importance of each tissue in HIV infection, the infection target cell types of each tissue, the specific infection situation of each tissue quantified by HIV DNA or HIV RNA and the evidence of compartmentalization and pharmacokinetics. In summary, we found that the present state of HIV in different tissues has both similarities and differences. In the future, the therapeutic principle we need to follow is to respect the discrepancy on the basis of grasping the commonality. The measures taken to completely eliminate the virus in the whole body cannot be generalized. It is necessary to formulate personalized treatment strategies according to the different characteristics of the HIV in the various tissues, so as to realize the prospect of curing AIDS as soon as possible.

CD73: Friend or Foe in Lung Injury

Ecto-5′-nucleotidase (CD73) plays a strategic role in calibrating the magnitude and chemical nature of purinergic signals that are delivered to immune cells. Its primary function is to convert extracellular ATP to adenosine in concert with ectonucleoside triphosphate diphosphohydrolase-1 (CD39) in normal tissues to limit an excessive immune response in many pathophysiological events, such as lung injury induced by a variety of contributing factors. Multiple lines of evidence suggest that the location of CD73, in proximity to adenosine receptor subtypes, indirectly determines its positive or negative effect in a variety of organs and tissues and that its action is affected by the transfer of nucleoside to subtype-specific adenosine receptors. Nonetheless, the bidirectional nature of CD73 as an emerging immune checkpoint in the pathogenesis of lung injury is still unknown. In this review, we explore the relationship between CD73 and the onset and progression of lung injury, highlighting the potential value of this molecule as a drug target for the treatment of pulmonary disease.

Frequency and functional profile of circulating TCRαβ+ double negative T cells in HIV/TB co-infection

BACKGROUND

Increased frequency of circulating double negative T (DNT, CD4^-CD8^-CD3⁺) cells with protective immune function has been observed in human immunodeficiency virus (HIV) infection and tuberculosis (TB). Here the role of circulating TCRαβ⁺ DNT cells was further investigated in HIV/TB co-infection.

METHODS

A cross-sectional study was conducted to investigate the frequency and functional profiles of peripheral TCRαβ⁺ DNT cells including apoptosis, chemokine and cytokine expression among healthy individuals and patients with TB, HIV infection and HIV/TB co-infection by cell surface staining and intracellular cytokine staining combined with flow cytometry.

RESULTS

Significantly increased frequency of TCRαβ⁺ DNT cells was observed in HIV/TB co-infection than that in TB (p < 0.001), HIV infection (p = 0.039) and healthy controls (p < 0.001). Compared with TB, HIV/TB co-infection had higher frequency of Fas expression (p = 0.007) and lower frequency of Annexin V expression on TCRαβ⁺ DNT cells (p = 0.049), and the frequency of Annexin V expression on Fas⁺TCRαβ⁺ DNT cells had no significant difference. TCRαβ⁺ DNT cells expressed less CCR5 in HIV/TB co-infection than that in TB (p = 0.014), and more CXCR4 in HIV/TB co-infection than that in HIV infection (p = 0.043). Compared with healthy controls, TB and HIV/TB co-infection had higher frequency of TCRαβ⁺ DNT cells secreting Granzyme A (p = 0.046; p = 0.005). In TB and HIV/TB co-infection, TCRαβ⁺ DNT cells secreted more granzyme A (p = 0.002; p = 0.002) and perforin (p < 0.001; p = 0.017) than CD4⁺ T cells but similar to CD8⁺ T cells.

CONCLUSIONS

Reduced apoptosis may take part in the mechanism of increased frequency of peripheral TCRαβ⁺ DNT cells in HIV/TB co-infection. TCRαβ⁺ DNT cells may play a cytotoxic T cells-like function in HIV/TB co-infection.

Interplay between the Lung Microbiome, Pulmonary Immunity and Viral Reservoirs in People Living with HIV under Antiretroviral Therapy

Pulmonary dysbiosis may predispose people living with HIV (PLWH) to chronic lung disease. Herein, we assessed whether intrapulmonary HIV reservoir size and immune disruption are associated with reduced bacterial lung diversity in PLWH. Bacterial DNA was extracted and PCR-amplified from cell-free bronchoalveolar lavage (BAL) fluid from 28 PLWH and 9 HIV-negative controls. Amplicon sequence variant (ASV) relative abundances and taxonomic identities were analyzed using joint species distribution modeling. HIV-DNA was quantified from blood and pulmonary CD4+ T-cells using ultra-sensitive qPCR. Immunophenotyping of BAL T-cells was performed using flow cytometry. Lung microbiome diversity was lower in smokers than non-smokers and microbiome composition was more variable in PLWH than HIV-negative individuals. Frequencies of effector memory BAL CD4+ and CD8+ T-cells positively correlated with abundance of several bacterial families while frequencies of BAL activated CD4+ T-cells negatively correlated with abundance of most lung bacterial families. Higher HIV-DNA levels in blood, but not in BAL, as well as frequencies of senescent CD4+ T-cells were associated with reduced bacterial diversity. These findings suggest that HIV infection may weaken the relationship between the lung microbiome and smoking status. Viral reservoir and immune activation levels may impact the lung microbiome, predisposing PLWH to pulmonary comorbidities.

Decreased CD73+ Double-Negative T Cells and Elevated Level of Soluble CD73 Correlated With and Predicted Poor Immune Reconstitution in HIV-Infected Patients After Antiretroviral Therapy

Although extensive use of antiretroviral therapy (ART) has made great progress in controlling HIV replication and improving CD4+ T cell recovery, the immune reconstitution remained insufficient in some patients, who were defined as poor immunological responders (PIRs). These PIRs were at a high risk of AIDS-related and non-AIDS complications, resulting in higher morbidity and mortality rate. Thus, it is a major challenge and urgently needed to distinguish PIRs early and improve their immune function in time. Immune activation is a key factor that leads to impaired immune reconstitution in people living with HIV (PLWH) who are receiving effective ART. Double negative T cells (DNT) were reported to associate with the control of immune activation during HIV infection. However, the precise mechanisms by which DNT cells exerted their suppressive capacity during HIV infection remained puzzled. CD73, both a soluble and a membrane-bound form, display immunosuppressive effects through producing adenosine (ADO). Thus, whether DNT cells expressed CD73 and mediated immune suppression through CD73-ADO pathway needs to be investigated. Here, we found a significant downregulation of CD73 expression on DNT cells in treatment-naïve PLWH (TNs) compared to healthy controls, accompanied with increased concentration of sCD73 in plasma. Both the frequency of CD73+ DNT cells and the level of plasma sCD73 recovered after ART treatment. However, PIRs showed decreased percentage of CD73+ DNT cells compared to immunological responders (IRs). The frequency of CD73+ DNT cells was positively correlated with CD4+ T cell count and CD4/CD8 ratio, and negatively correlated with immune activation in PLWH. The level of sCD73 also showed a negative correlation to CD4+ T cell count and CD4/CD8 ratio. More importantly, in the present cohort, a higher level of sCD73 at the time of initiating ART could predict poor immune reconstitution in PLWH after long-term ART. Our findings highlighted the importance of CD73+ DNT cells and sCD73 in the disease progression and immune reconstitution of PLWH, and provided evidences for sCD73 as a potential biomarker of predicting immune recovery.

Double-negative T cells: Setting the stage for disease control or progression

Double-negative (DN) T cells are present at relatively low frequencies in human peripheral blood, and are characterized as expressing the alpha-beta or gamma-delta T-cell receptor (TCR), but not the CD4 nor the CD8 co-receptors. Despite their low frequencies, these cells are potent producers of cytokines and, thus, are key orchestrators of immune responses. DN T cells were initially associated with induction of peripheral immunological tolerance and immunomodulatory activities related to disease prevention. However, other studies demonstrated that these cells can also display effector functions associated with pathology development. This apparent contradiction highlighted the heterogeneity of the DN T-cell population. Here, we review phenotypic and functional characteristics of DN T cells, emphasizing their role in human diseases. The need for developing biomarkers to facilitate the translation of studies from animal models to humans will also be discussed. Finally, we will examine DN T cells as promising therapeutic targets to prevent or inhibit human disease development.

Pulmonary Immune Dysregulation and Viral Persistence During HIV Infection

Despite the success of antiretroviral therapy (ART), people living with HIV continue to suffer from high burdens of respiratory infections, lung cancers and chronic lung disease at a higher rate than the general population. The lung mucosa, a previously neglected HIV reservoir site, is of particular importance in this phenomenon. Because ART does not eliminate the virus, residual levels of HIV that remain in deep tissues lead to chronic immune activation and pulmonary inflammatory pathologies. In turn, continuous pulmonary and systemic inflammation cause immune cell exhaustion and pulmonary immune dysregulation, creating a pro-inflammatory environment ideal for HIV reservoir persistence. Moreover, smoking, gut and lung dysbiosis and co-infections further fuel the vicious cycle of residual viral replication which, in turn, contributes to inflammation and immune cell proliferation, further maintaining the HIV reservoir. Herein, we discuss the recent evidence supporting the notion that the lungs serve as an HIV viral reservoir. We will explore how smoking, changes in the microbiome, and common co-infections seen in PLWH contribute to HIV persistence, pulmonary immune dysregulation, and high rates of infectious and non-infectious lung disease among these individuals.

Imprint of unconventional T-cell response in acute hepatitis C persists despite successful early antiviral treatment

Unconventional T cells (UTCs) are a heterogeneous group of T cells that typically exhibit rapid responses toward specific antigens from pathogens. Chronic hepatitis C virus (HCV) infection causes dysfunction of several subsets of UTCs. This altered phenotype and function of UTCs can persist over time even after direct-acting antiviral (DAA)-mediated clearance of chronic HCV. However, it is less clear if and how UTCs respond in acute, symptomatic HCV infection, a rare clinical condition, and if rapid DAA treatment of such patients reverses the caused perturbations within UTCs. Here, we comprehensively analyzed the phenotype and reinvigoration capacity of three major UTC populations, mucosal-associated invariant T (MAIT) cells, γδ T cells, and CD4 and CD8 double-negative αβ T cells (DNT cells) before, during, and after DAA-mediated clearance of acute symptomatic HCV infection. Furthermore, MAIT cell functionality was systematically studied. We observed a reduced frequency of MAIT cells. However, remaining cells presented with a near-to-normal phenotype in acute infection, which contrasted with a significant dysfunction upon stimulation that was not restored after viral clearance. Notably, DNT and γδ T cells displayed a strong activation ex-vivo in acute HCV infection, which subsequently normalized during the treatment. In addition, DNT cell activation was specifically associated with liver inflammation and inflammatory cytokines. Altogether, these data provide evidence that UTCs respond in a cell type-specific manner during symptomatic HCV infection. However, even if early treatment is initiated, long-lasting imprints within UTCs remain over time.

Recent advances in HIV-associated chronic lung disease clinical research

PURPOSE OF REVIEW

To highlight recently published, clinically focused research on chronic lung disease in adult persons with human immunodeficiency virus-1 (HIV) (PWH).

RECENT FINDINGS

Chronic lung disease was the most common comorbidity in hospitalized PWH in New York and second-most common condition in ambulatory PWH in Canada. The elevated risk of chronic obstructive pulmonary disease in PWH has been widely recognized, but PWH are also at higher risk for asthma and worse asthma outcomes. Expanded assessments of lung structure and function, such as single-breath diffusing capacity of carbon monoxide (DLCO), exhaled nitric oxide (FeNO), and chest computed tomography (CT) have provided new insights into HIV effects on the lungs. New biomarker analyses are emerging, but further studies are needed to validate predictive biomarkers for chronic lung disease in PWH. Clinical trials addressing chronic lung disease in PWH are few in number.

SUMMARY

Chronic lung disease is a common and high-impact comorbidity among PWH. Future studies should collect more comprehensive lung assessments such as DLCO, FeNO, and chest CT in order to better phenotype lung derangements in HIV. Clinical trials are desperately needed to reduce the rising burden of chronic lung disease in PWH.

Double-negative T cells in autoimmune diseases

PURPOSE OF REVIEW

TCRαβ+CD4-CD8- double-negative T (DNT) cells, a principal subset of mature T lymphocytes, have been closely linked with autoimmune/inflammatory conditions. However, controversy persists regarding their ontogeny and function. Here, we present an overview on DNT cells in different autoimmune diseases to advance a deeper understanding of the contribution of this population to disease pathogenesis.

RECENT FINDINGS

DNT cells have been characterized in various chronic inflammatory diseases and they have been proposed to display pathogenic or regulatory function. The tissue location of DNT cells and the effector cytokines they produce bespeak to their active involvement in chronic inflammatory diseases.

SUMMARY

By producing various cytokines, expanded DNT cells in inflamed tissues contribute to the pathogenesis of a variety of autoimmune inflammatory diseases. However, it is unclear whether this population represents a stable lineage consisting of different subsets similar to CD4+ T helper cell subset. Better understanding of the possible heterogeneity and plasticity of DNT cells is needed to reveal interventional therapeutic opportunities.