NK cells in treated HIV-infected children display altered phenotype and function

High KIR diversity in Uganda and Botswana children living with HIV

Killer-cell immunoglobulin-like receptors (KIRs) are essential components of the innate immune system found on the surfaces of natural killer (NK) cells. The KIRs encoding genes are located on chromosome 19q13.4 and are genetically diverse across populations. KIRs are associated with various disease states including HIV progression, and are linked to transplantation rejection and reproductive success. However, there is limited knowledge on the diversity of KIRs from Uganda and Botswana HIV-infected paediatric cohorts, with high endemic HIV rates. We used next-generation sequencing technologies on 312 (246 Uganda, 66 Botswana) samples to generate KIR allele data and employed customised bioinformatics techniques for allelic, allotype and disease association analysis. We show that these sample sets from Botswana and Uganda have different KIRs of different diversities. In Uganda, we observed 147 vs 111 alleles in the Botswana cohort, which had a more than 1 % frequency. We also found significant deviation towards homozygosity for the KIR3DL2 gene for both rapid (RPs) and long-term non-progressors (LTNPs)in the Ugandan cohort. The frequency of the bw4-80I ligand was also significantly higher among the LTNPs than RPs (8.9 % Vs 2.0%, P-value: 0.032). In the Ugandan cohort, KIR2DS4*001 (OR: 0.671, 95 % CI: 0.481-0.937, FDR adjusted Pc=0.142) and KIR2DS4*006 (OR: 2.519, 95 % CI: 1.085-5.851, FDR adjusted Pc=0.142) were not associated with HIV disease progression after adjustment for multiple testing. Our study results provide additional knowledge of the genetic diversity of KIRs in African populations and provide evidence that will inform future immunogenetics studies concerning human disease susceptibility, evolution and host immune responses.

Integrins in Health and Disease-Suitable Targets for Treatment?

Integrin receptors are heterodimeric surface receptors that play multiple roles regarding cell-cell communication, signaling, and migration. The four members of the β2 integrin subfamily are composed of an alternative α (CD11a-d) subunit, which determines the specific receptor properties, and a constant β (CD18) subunit. This review aims to present insight into the multiple immunological roles of integrin receptors, with a focus on β2 integrins that are specifically expressed by leukocytes. The pathophysiological role of β2 integrins is confirmed by the drastic phenotype of patients suffering from leukocyte adhesion deficiencies, most often resulting in severe recurrent infections and, at the same time, a predisposition for autoimmune diseases. So far, studies on the role of β2 integrins in vivo employed mice with a constitutive knockout of all β2 integrins or either family member, respectively, which complicated the differentiation between the direct and indirect effects of β2 integrin deficiency for distinct cell types. The recent generation and characterization of transgenic mice with a cell-type-specific knockdown of β2 integrins by our group has enabled the dissection of cell-specific roles of β2 integrins. Further, integrin receptors have been recognized as target receptors for the treatment of inflammatory diseases as well as tumor therapy. However, whereas both agonistic and antagonistic agents yielded beneficial effects in animal models, the success of clinical trials was limited in most cases and was associated with unwanted side effects. This unfavorable outcome is most probably related to the systemic effects of the used compounds on all leukocytes, thereby emphasizing the need to develop formulations that target distinct types of leukocytes to modulate β2 integrin activity for therapeutic applications.

Longitudinal analysis of innate immune system in infants with perinatal HIV infection until 18 months of age

With the advent of antiretroviral therapy (ART), perinatal HIV infection is declining globally but prevalence in Sub-Saharan Africa is still greater than other nations. The relationship of HIV replication in early infancy and the developing immune system is not well understood. In this study, we investigated cellular components of the innate immune system including Natural Killer (NK) cells, monocytes, and Dendritic Cells (DC) in a cohort of HIV exposed infected (HEI) and age-matched HIV exposed uninfected (HEU) infants from Mozambique. Study entry was at the first visit after delivery at age 1-2 months for HIV diagnosis and initiation of ART. Phenotypic analysis by multi-parameter flow cytometry revealed an expansion of total NK cells and the dysfunctional, CD56-CD16+, NK cell subset; increased activation in monocytes and DC; and higher levels of inflammatory homing receptor CCR5 on circulating DC subsets in the HEI infants. NKG2A, an inhibitory receptor for NK cytolytic function, was reduced in HEI compared to HEU and positively correlated with pre-ART viral load (VL) while expression of CCR2, the inflammatory homing receptor, on NK was negatively correlated with VL. Other subsets exhibited positive correlations with VL including the frequency of intermediate monocytes amongst total monocytes. Longitudinal analysis of VL indicated suboptimal ART adherence in HEI. Regardless of level of viral suppression achieved, the frequencies of specific innate immune subsets in HEI were normalized to HEU by 18m. These data support the notion that in early life, NK cells play a role in virus control and should be explored for functional attributes that are effective against HIV at this time during development. Overall, our study provides high resolution overview of the innate immune system during perinatal HIV infection.

NK cell subsets and dysfunction during viral infection: a new avenue for therapeutics?

In the setting of viral challenge, natural killer (NK) cells play an important role as an early immune responder against infection. During this response, significant changes in the NK cell population occur, particularly in terms of their frequency, location, and subtype prevalence. In this review, changes in the NK cell repertoire associated with several pathogenic viral infections are summarized, with a particular focus placed on changes that contribute to NK cell dysregulation in these settings. This dysregulation, in turn, can contribute to host pathology either by causing NK cells to be hyperresponsive or hyporesponsive. Hyperresponsive NK cells mediate significant host cell death and contribute to generating a hyperinflammatory environment. Hyporesponsive NK cell populations shift toward exhaustion and often fail to limit viral pathogenesis, possibly enabling viral persistence. Several emerging therapeutic approaches aimed at addressing NK cell dysregulation have arisen in the last three decades in the setting of cancer and may prove to hold promise in treating viral diseases. However, the application of such therapeutics to treat viral infections remains critically underexplored. This review briefly explores several therapeutic approaches, including the administration of TGF-β inhibitors, immune checkpoint inhibitors, adoptive NK cell therapies, CAR NK cells, and NK cell engagers among other therapeutics.

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.

Innate and adaptive abnormalities in youth with vertically acquired HIV through a multicentre cohort in Spain

Introduction

Immune abnormalities have been described among youth with vertically acquired HIV (YWVH) despite antiretroviral treatment (ART). The CD4/CD8 ratio could be a useful prognostic marker. We assess immune activation and senescence in a cohort of YWVH in comparison to youth without vertically acquired HIV.

Methods

YWVH under suppressive ART were included and compared to a group of HIV‐negative donors (HD) matched by age and sex, from September 2019 to September 2020. Subset distribution and expression of activation, maturation, senescence and exhaustion markers on T and NK cells were studied on peripheral blood mononuclear cells by multiparametric flow cytometry.

Results

Thirty‐two YWVH (median age: 24.4 years (interquartile range: 22.5 to 28.3 years)) were included. Among YWVH, CD4‐ and CD8‐T cells showed high levels of activation (HLA‐DR/CD38), IL‐7 receptor expression (CD127) and exhaustion (TIM‐3). Regarding NK cells, YWVH showed increased levels of activation and exhaustion markers compared to HD. Strong inverted correlations were observed between T‐cell activation (HLA‐DR/CD38), senescence (CD57) and exhaustion (TIGIT, PD‐1) levels with the CD4/CD8 ratio among YWVH. HLA‐DR, CD69, NKG2D and NKG2A expression levels on NK cells also correlated with the CD4/CD8 ratio. Age at ART initiation was directly associated with higher frequency of CD16^high NK‐cell subsets, exhaustion T‐cell levels (CD57, TIM3) and NK cells activation levels.

Conclusions

Immunological changes associated with vertically acquired HIV, characterized by increased activation and exhaustion levels in innate and adaptive immune components, are only partially restored by ART. The CD4/CD8 ratio can be a useful marker of disease progression for routine clinical practice.

Early ART initiation during infancy preserves natural killer cells in young European adolescents living with HIV (CARMA cohort)

INTRODUCTION

HIV infection causes pathological changes in the natural killer (NK) cell compartment that can be only partially restored by antiretroviral therapy (ART). We investigated NK cells phenotype and function in children with perinatally acquired HIV (PHIV) and long-term viral control (five years) due to effective ART in a multicentre cross-sectional European study (CARMA, EPIICAL consortium). The impact of age at ART start and viral reservoir was also evaluated.

METHODS

Peripheral blood mononuclear cells (PBMCs) from 40 PHIV who started ART within two years of life (early treated patients (ET), ≤6 months; late treated patients (LT), > 6 months), with at least five years of HIV-1 suppression (<40 HIV copies/mL), were collected between November 2017 and August 2018. NK phenotype and function were analysed by flow cytometry and transcriptional profile of PBMCs by RNA-Seq. HIV-1 DNA was measured by real-time polymerase chain reaction (Data were analysed by Spearman correlation plots and multivariable Poisson regression model (adjusted for baseline %CD4 and RNA HIV viral load and for age at ART start as an interaction term, either ET or LT) to explore the association between NK cell parameters and HIV reservoir modulated by age at ART start.

RESULTS

A significantly higher frequency of CD56neg NK cells was found in LT compared with ET. We further found in LT a positive correlation of CD56neg NK cells with HIV-1 DNA. LT also displayed increased expression of the NKG2D and NKp46 activating receptors and perforin compared with ET. Moreover, CD107a+ and IFN-γ+ frequencies in non-stimulated NK were associated with HIV-1 DNA in LT patients. Finally, RNA-Seq analysis showed in LT an up-regulation of genes related to NK-activating pathways and susceptibility to apoptosis compared with ET.

CONCLUSIONS

We show that early initiation of ART during infancy preserves the NK compartment and is associated with lower HIV-1 reservoir. Such condition persists over adolescence due to long-term viral control achieved through effective ART.

Immune cell profiles associated with measured exposure to phthalates in the Norwegian EuroMix biomonitoring study - A mass cytometry approach in toxicology

BACKGROUND

Phthalate exposure has been associated with immune-related diseases such as asthma and allergies, but there is limited knowledge on mechanisms, effect biomarkers and thus biological support of causality.

OBJECTIVES

To investigate associations between exposure to the phthalates DEHP (di(2-ethylhexyl) phthalate) and DiNP (diisononyl phthalate) and functional immune cell profiles.

METHODS

Peripheral blood mononuclear cells (PBMCs) from 32 healthy adult Norwegian participants in the EuroMix biomonitoring study were selected based on high or low (n = 16) levels of urine metabolites of DEHP and DiNP. High-dimensional immune cell profiling including phenotyping and functional markers was performed by mass cytometry (CyTOF) using two broad antibody panels after PMA/ionomycin-stimulation. The CITRUS algorithm with unsupervised clustering was used to identify group differences in cell subsets and expression of functional markers, verified by manual gating.

RESULTS

The group of participants with high phthalate exposure had a higher proportion of some particular innate immune cells, including CD11c positive NK-cell and intermediate monocyte subpopulations. The percentage of IFNγ TNFα double positive NK cells and CD11b expression in other NK cell subsets were higher in the high exposure group. Among adaptive immune cells, however, the percentage of IL-6 and TNFα expressing naïve B cell subpopulations and the percentage of particular naïve cytotoxic T cell populations were lower in the high exposure group.

DISCUSSION

Cell subset percentages and expression of functional markers suggest that DEHP and DiNP phthalate exposure may stimulate subsets of innate immune cells and suppress adaptive immune cell subsets. By revealing significant immunological differences even in small groups, this study illustrates the promise of the broad and deep information obtained by high-dimensional single cell analyses of human samples to answer toxicological questions regarding health effects of environmental exposures.

Deciphering the Immunological Phenomenon of Adaptive Natural Killer (NK) Cells and Cytomegalovirus (CMV)

Natural killer (NK) cells play a significant and vital role in the first line of defense against infection through their ability to target cells without prior sensitization. They also contribute significantly to the activation and recruitment of both innate and adaptive immune cells through the production of a range of cytokines and chemokines. In the context of cytomegalovirus (CMV) infection, NK cells and CMV have co-evolved side by side to employ several mechanisms to evade one another. However, during this co-evolution the discovery of a subset of long-lived NK cells with enhanced effector potential, increased antibody-dependent responses and the potential to mediate immune memory has revolutionized the field of NK cell biology. The ability of a virus to imprint on the NK cell receptor repertoire resulting in the expansion of diverse, highly functional NK cells to this day remains a significant immunological phenomenon that only occurs in the context of CMV. Here we review our current understanding of the development of these NK cells, commonly referred to as adaptive NK cells and their current role in transplantation, infection, vaccination and cancer immunotherapy to decipher the complex role of CMV in dictating NK cell functional fate.

Functional Perturbation of Mucosal Group 3 Innate Lymphoid and Natural Killer Cells in Simian-Human Immunodeficiency Virus/Simian Immunodeficiency Virus-Infected Infant Rhesus Macaques

Mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1) via breastfeeding is responsible for nearly half of new infections of children with HIV. Although innate lymphoid cells (ILC) and natural killer (NK) cells are found throughout the oral mucosae, the effects of HIV/simian-human immunodeficiency virus (SHIV) in these tissues are largely unknown. To better understand the mechanics of postnatal transmission, we performed a comprehensive study of simian immunodeficiency virus (SIV)/SHIV-infected infant rhesus macaques (RM) and tracked changes in frequency, trafficking, and function of group 3 ILC (ILC3) and NK cells using polychromatic flow cytometry and cell stimulation assays in colon, tonsil, and oral lymph node samples. Infection led to a 3-fold depletion of ILC3 in the colon and an increase in the levels of NK cells in tonsils and oral lymph nodes. ILC3 and NK cells exhibited alterations in their trafficking repertoires as a result of infection, with increased expression of CD103 in colon NK cells and curtailment of CXCR3, and a significant decrease in α4β7 expression in colon ILC3. SPICE analyses revealed that ILC3 and NK cells displayed distinct functional profiles by tissue in naive samples. Infection perturbed these profiles, with a nearly total loss of interleukin-22 (IL-22) production in the tonsil and colon; an increase in the levels of CD107a, gamma interferon (IFN-γ), and tumor necrosis factor alpha (TNF-α) from ILC3; and an increase in the levels of CD107a, macrophage inflammatory protein 1 beta (MIP-1β), and TNF-α from NK cells. Collectively, these data reveal that lentivirus infection alters the frequencies, receptor repertoires, and functions of innate cells in the oral and gut mucosa of infants. Further study will be required to delineate the full extent of the effect that these changes have on oral and gut homeostasis, SHIV/SIV pathogenesis, and oral opportunistic disease.IMPORTANCE Vertical transmission of HIV from mother to child accounts for many of the new cases seen worldwide. There is currently no vaccine to mitigate this transmission, and there has been limited research on the effects that lentiviral infection has on the innate immune system in oral tissues of infected children. To fill this knowledge gap, our laboratory studied infant rhesus macaques to evaluate how acute SIV/SHIV infections impacted ILC3 and NK cells, which are immune cells critical for mucosal homeostasis and antimicrobial defense. Our data revealed that SIV/SHIV infection led to a depletion of ILC3 and an increase of NK cells and to a functional shift from a homeostatic to a multifunctional proinflammatory state. Taking the results together, we describe how lentiviral infection perturbs the oral and gastrointestinal mucosae of infant macaques through alterations of resident innate immune cells giving rise to chronic inflammation and potentially exacerbating morbidity and mortality in children living with HIV.

DNAM-1 Activating Receptor and Its Ligands: How Do Viruses Affect the NK Cell-Mediated Immune Surveillance during the Various Phases of Infection?

Natural Killer (NK) cells play a critical role in host defense against viral infections. The mechanisms of recognition and killing of virus-infected cells mediated by NK cells are still only partially defined. Several viruses induce, on the surface of target cells, the expression of molecules that are specifically recognized by NK cell-activating receptors. The main NK cell-activating receptors involved in the recognition and killing of virus-infected cells are NKG2D and DNAM-1. In particular, ligands for DNAM-1 are nectin/nectin-like molecules involved also in mechanisms allowing viral infection. Viruses adopt several immune evasion strategies, including those affecting NK cell-mediated immune surveillance, causing persistent viral infection and the development of virus-associated diseases. The virus's immune evasion efficacy depends on molecules differently expressed during the various phases of infection. In this review, we overview the molecular strategies adopted by viruses, specifically cytomegalovirus (CMV), human immunodeficiency virus (HIV-1), herpes virus (HSV), Epstein-Barr virus (EBV) and hepatitis C virus (HCV), aiming to evade NK cell-mediated surveillance, with a special focus on the modulation of DNAM-1 activating receptor and its ligands in various phases of the viral life cycle. The increasing understanding of mechanisms involved in the modulation of activating ligands, together with those mediating the viral immune evasion strategies, would provide critical tools leading to design novel NK cell-based immunotherapies aiming at viral infection control, thus improving cure strategies of virus-associated diseases.