Cytomegalovirus infection alters phenotypes of different γδ T-cell subsets in renal transplant recipients with long-term stable graft function

An IL-10 homologue encoded by human cytomegalovirus is linked with the viral "footprint" in clinical samples

Persistent infections with human cytomegalovirus (HCMV) affect the hosts' immune system and have been linked with chronic inflammation and cardiovascular disease. These effects may be influenced by a HCMV-encoded homologue of the anti-inflammatory cytokine, IL-10 (cmvIL-10). To assess this, we quantitated cmvIL-10 in plasma from renal transplant recipients (RTR) and healthy adults. Detectable levels of cmvIL-10 associated with seropositivity in RTR, but were found in some seronegative healthy adults. RTR with detectable cmvIL-10 had elevated interferon-γ T-cell responses to HCMV antigens, whilst cmvIL-10 in healthy adults associated with reduced populations of terminally-differentiated T-cells - a known "footprint" of HCMV. Plasma cmvIL-10 associated with lower VCAM-1 levels in healthy adults. The data suggest cmvIL-10 may suppress seroconversion and/or reduce the footprint of HCMV in healthy adults. This appears to be subverted in RTR by their high burden of HCMV and/or immune dysregulation associated with transplantation. A role for cmvIL-10 in protection of vascular health is discussed.

Do variations in the HLA-E ligand encoded by UL40 distinguish individuals susceptible to HCMV disease?

Human cytomegalovirus (HCMV) is carried lifelong by ∼80 % of adults worldwide, generating distinct disease syndromes in transplant recipients, people with HIV (PWH) and neonates. Amino acids 15-23 encoded by the HCMV gene UL40 match positions 3-11 of HLA-A and HLA-C, and constitute a "signal peptide" able to stabilise cell surface HLA-E as a restriction element and a ligand of NKG2A and NKG2C. We present next generation sequencing of UL40 amplified from 15 Australian renal transplant recipients (RTR), six healthy adults and four neonates, and 21 Indonesian PWH. We found no groupwise associations between the presence of multiple sequences and HCMV burden (highest in PWH) or HCMV-associated symptoms in neonates. Homology between UL40 and corresponding HLA-C and HLA-A peptides in 11 RTR revealed perfect matches with HLA-C in three individuals, all carrying HCMV encoding only VMAPRTLIL - a peptide previously associated with viremia. However indices of the burden of HCMV did not segregate in our cohort.

Releasing the restraints of Vγ9Vδ2 T-cells in cancer immunotherapy

Objectives

Vγ9Vδ2 T-cells are a subset of T-cells with a crucial role in immunosurveillance which can be activated and expanded by multiple means to stimulate effector responses. Little is known about the expression of checkpoint molecules on this cell population and whether the ligation of these molecules can regulate their activity. The aim of this study was to assess the expression of both activatory and inhibitory receptors on Vγ9Vδ2 T-cells to assess potential avenues of regulation to target with immunotherapy.

Methods

Expression of various activatory and inhibitory receptors was assessed on Vγ9Vδ2 T-cells by flow cytometry following activation and expansion using zoledronic acid (ZA) and Bacillus Calmette-Guérin (BCG). Expression of these markers and production of effector molecules was also examined following co-culture with various tumour cell targets. The effect of immune checkpoint blockade on Vγ9Vδ2 T-cells was also explored.

Results

Vγ9Vδ2 T-cells expressed high levels of activatory markers both at baseline and following stimulation. Vγ9Vδ2 T-cells expressed variable levels of inhibitory checkpoint receptors with many being upregulated following stimulation. Expression of these markers is further modulated upon co-culture with tumour cells with changes reflecting activation and effector functions. Despite their high expression of inhibitory receptors when cultured with tumour cells expressing cognate ligands there was no effect on Vδ2+ T-cell cytotoxic capacity or cytokine production with immune checkpoint blockade.

Conclusions

Our work suggests the expression of checkpoint receptors present on Vγ9Vδ2 T-cells which may provide a mechanism with the potential to be utilised by tumour cells to subvert Vγ9Vδ2 T-cell cytotoxicity. This work suggests important candidates for blockade by ICI therapy in order to increase the successful use of Vγ9Vδ2 T-cells in immunotherapy.

Human Cytomegalovirus Infection and Cardiovascular Disease: Current Perspectives

Infections with human cytomegalovirus (HCMV) are often asymptomatic in healthy adults but can be severe in people with a compromised immune system. While several studies have demonstrated associations between cardiovascular disease in older adults and HCMV seropositivity, the underlying mechanisms are unclear. We review evidence published within the last 5 years establishing how HCMV can contribute directly and indirectly to the development and progression of atherosclerotic plaques. We also discuss associations between HCMV infection and cardiovascular outcomes in populations with a high or very high burden of HCMV, including patients with renal or autoimmune disease, transplant recipients, and people living with HIV.

Variants of HCMV UL18 Sequenced Directly from Clinical Specimens Associate with Antibody and T-Cell Responses to HCMV

Around 80% of adults worldwide carry human cytomegaloviris (HCMV). The HCMV gene UL18 is a homolog of HLA class I genes and encodes a protein with high affinity for the NK and T-cell cytotoxicity inhibitor LIR-1. UL18 was deep sequenced from blood, saliva or urine from Indonesian people with HIV (PWH) (n = 28), Australian renal transplant recipients (RTR) (n = 21), healthy adults (n = 7) and neonates (n = 4). 95% of samples contained more than one variant of HCMV UL18, as defined by carriage of nonsynonymous variations. When aligned with immunological markers of the host's burden of HCMV, the S318N variation associated with high levels of antibody reactive with HCMV lysate in PWH over 12 months on antiretroviral therapy. The A107T variation associated with HCMV antibody levels and inflammatory biomarkers in PWH at early timepoints. Variants D32G, D248N, V250A and E252D aligned with elevated HCMV antibody levels in RTR, while M191K, E196Q and F165L were associated with HCMV-reactive T-cells and proportions of Vδ2- γδ T-cells-populations linked with high burdens of HCMV. We conclude that UL18 is a highly variable gene, where variation may alter the persistent burden of HCMV and/or the host response to that burden.

γδ T Cell Subpopulations Associate with Recovery of Memory Function in Indonesian HIV Patients Starting Antiretroviral Therapy

Cognitive impairment may persist in HIV patients despite effective antiretroviral therapy (ART). However, recovery is influenced by the neurocognitive domain tested, the severity of HIV disease, and by education. In young adult patients commencing ART in Jakarta, Indonesia, we described improvements in all cognitive domains except memory after 6-12 months on ART. In this study, we address relationships between cytomegalovirus (CMV), γδ T cell profiles and neurocognitive assessments with a focus on memory. The JakCCANDO (Jakarta CMV Cardiovascular ART Neurology Dentistry Ophthalmology) project recruited patients (aged 18-48 years) beginning ART with <200 CD4⁺ T cells/μL. Cognitive assessments used validated tests of five domains. Flow cytometry was used to assess proportions of Vδ2^- and Vδ2⁺ γδ T cells, and their activation (HLA-DR) and terminal differentiation (CD27^-/CD45RA⁺). All patients carried high levels of antibodies reactive with CMV, so the detection of CMV DNA before ART was used to stratify participants into subgroups with a moderate/high or an extremely high burden of CMV. Patients had higher proportions of Vδ2^- γδ T cells and fewer Vδ2⁺ γδ T cells than healthy controls before ART and at 6 months. Z-scores for memory function correlated with proportions of Vδ2⁺ γδ T cells at both time points. Linear regression analyses confirmed this association. When the detection of CMV DNA was used to stratify the cohort, the association between memory Z-scores and Vδ2⁺ γδ T cells or CMV antibodies was only discernible in patients with a lower CMV burden. Hence, CMV and Vδ2⁺ γδ T cells warrant further consideration as factors that may contribute to the poor recovery of memory on ART.

Sequencing of the Viral UL111a Gene Directly from Clinical Specimens Reveals Variants of HCMV-Encoded IL-10 That Are Associated with Altered Immune Responses to HCMV

Human cytomegalovirus (HCMV) is a beta-herpesvirus carried by ~80% of adults worldwide. Acute infections are often asymptomatic in healthy individuals but generate diverse syndromes in neonates, renal transplant recipients (RTR), and people with HIV (PWH). The HCMV gene UL111a encodes a homolog of human interleukin-10 (IL-10) that interacts with the human IL-10 receptor. Deep sequencing technologies were used to sequence UL111a directly from 59 clinical samples from Indonesian PWH and Australian RTR, healthy adults, and neonates. Overall, 93% of samples contained more than one variant of HCMV, as defined by at least one nonsynonymous variation. Carriage of these variants differed between neonates and adults, Australians and Indonesians, and between saliva and blood leukocytes. The variant alleles of N41D and S71Y occurred together in Australian RTR and were associated with higher T-cell responses to HCMV pp65. The variant P122S was associated with lower levels of antibodies reactive with a lysate of HCMV-infected fibroblasts. L174F was associated with increased levels of antibodies reactive with HCMV lysate, immediate-early 1 (IE-1), and glycoprotein B (gB) in Australian RTR and Indonesians PWH, suggesting a higher viral burden. We conclude that variants of UL111a are common in all populations and may influence systemic responses to HCMV.

The Contribution of Human Herpes Viruses to γδ T Cell Mobilisation in Co-Infections

γδ T cells are activated in viral, bacterial and parasitic infections. Among viruses that promote γδ T cell mobilisation in humans, herpes viruses (HHVs) occupy a particular place since they infect the majority of the human population and persist indefinitely in the organism in a latent state. Thus, other infections should, in most instances, be considered co-infections, and the reactivation of HHV is a serious confounding factor in attributing γδ T cell alterations to a particular pathogen in human diseases. We review here the literature data on γδ T cell mobilisation in HHV infections and co-infections, and discuss the possible contribution of HHVs to γδ alterations observed in various infectious settings. As multiple infections seemingly mobilise overlapping γδ subsets, we also address the concept of possible cross-protection.

Challenging the Conventional Interpretation of HCMV Seronegativity

The majority of adults in the world (around 83%) carry antibodies reactive with HCMV and are thought to retain inactive or latent infections lifelong. The virus is transmitted via saliva, so infection events are likely to be common. Indeed, it is hard to imagine a life without exposure to HCMV. From 45 seronegative individuals (13 renal transplant recipients, 32 healthy adults), we present seven cases who had detectable HCMV DNA in their blood and/or saliva, or a CMV-encoded homologue of IL-10 (vIL-10) in their plasma. One case displayed NK cells characteristic of CMV infection before her HCMV DNA became undetectable. In other cases, the infection may persist with seroconversion blocked by vIL-10. Future research should seek mechanisms that can prevent an individual from seroconverting despite a persistent HCMV infection, as HCMV vaccines may not work well in such people.

Revisiting the Role of γδ T Cells in Anti-CMV Immune Response after Transplantation

Gamma delta (γδ) T cells form an unconventional subset of T lymphocytes that express a T cell receptor (TCR) consisting of γ and δ chains. Unlike conventional αβ T cells, γδ T cells share the immune signature of both the innate and the adaptive immunity. These features allow γδ T cells to act in front-line defense against infections and tumors, rendering them an attractive target for immunotherapy. The role of γδ T cells in the immune response to cytomegalovirus (CMV) has been the focus of intense research for several years, particularly in the context of transplantation, as CMV reactivation remains a major cause of transplant-related morbidity and mortality. Therefore, a better understanding of the mechanisms that underlie CMV immune responses could enable the design of novel γδ T cell-based therapeutic approaches. In this regard, the advent of next-generation sequencing (NGS) and single-cell TCR sequencing have allowed in-depth characterization of CMV-induced TCR repertoire changes. In this review, we try to shed light on recent findings addressing the adaptive role of γδ T cells in CMV immunosurveillance and revisit CMV-induced TCR reshaping in the era of NGS. Finally, we will demonstrate the favorable and unfavorable effects of CMV reactive γδ T cells post-transplantation.

Understanding the effects of CMV on γδ T-cell populations in HIV patients starting antiretroviral therapy

Cytomegalovirus (CMV) affects γδ T-cell profiles in healthy individuals and transplant recipients, but the effects of HIV and CMV have not been distinguished in HIV patients. CMV-seropositive Indonesian HIV patients (n = 40) were studied before ART and after six months, alongside healthy controls (n = 20). 50% of patients started ART with detectable CMV DNA. Proportions of Vδ2^- γδ T-cells were high in patients and declined on ART, whilst proportions of Vδ2⁺ γδ T-cells were uniformly low, and correlated inversely with levels of CMV DNA and CMV-reactive antibody. Residual Vδ2⁺ cells were enriched for markers of terminal differentiation, but this did not associate with CMV metrics. Patients with CMV DNA at baseline showed a direct correlation between CMV reactive-antibody and CD8⁺ γδ T-cells. Our data are consistent with a role for CMV in the depletion of Vδ2⁺ γδ T-cells in HIV patients beginning ART, with no consistent evidence of a role for CMV in γδ T-cell activation or differentiation.

Leukocyte immunoglobulin-like receptor subfamily B: therapeutic targets in cancer

Inhibitory leukocyte immunoglobulin-like receptors (LILRBs 1–5) transduce signals via intracellular immunoreceptor tyrosine-based inhibitory motifs that recruit phosphatases to negatively regulate immune activation. The activation of LILRB signaling in immune cells may contribute to immune evasion. In addition, the expression and signaling of LILRBs in cancer cells especially in certain hematologic malignant cells directly support cancer development. Certain LILRBs thus have dual roles in cancer biology—as immune checkpoint molecules and tumor-supporting factors. Here, we review the expression, ligands, signaling, and functions of LILRBs, as well as therapeutic development targeting them. LILRBs may represent attractive targets for cancer treatment, and antagonizing LILRB signaling may prove to be effective anti-cancer strategies.

Cytomegalovirus burden improves a predictive model identifying measures of vascular risk in renal transplant recipients and healthy adults

Cytomegalovirus (CMV) has been implicated in vascular pathologies and may warrant inclusion in cardiovascular predictive algorithms. We addressed this in healthy older adults and renal transplant recipients (RTR) as they retain a high burden of CMV. RTR (n  =  45) stable more than 2 years after transplantation and 58 age-matched healthy adults were assessed. Plasma inflammatory biomarkers (soluble isoform of the interferon-β receptor [sIFNAR2], soluble tumour necrosis factorreceptor-1 [sTNFR1], soluble cluster of differentiation 14 [sCD14], C reactive protein, P-selectin, intracellular cell adhesion molecule-1, vascular cell adhesion molecule-1), and measures of CMV burden (antibodies, saliva CMV DNA, and interferon γ responses to CMV) were assessed in 2014 and evaluated in 2017 as predictors of vascular health-defined using flow-mediated dilatation (FMD), pulse wave velocity (PWV), and augmentation indices (Aix@ 75). Linear regression models adjusted for age, sex, and body mass index (BMI) were optimized to identify risk factors. In 2017, RTR had inferior vascular health marked by impaired FMD and PWV. Detectable CMV DNA (P = .02) was associated with impaired FMD, whilst CMV glycoprotein B (gB) antibody attenuated this effect (P  =  .03) (adjusted R2  =  .42). In healthy adults, the optimal model for predicting FMD (R2  =.22) incorporated high P-selectin (P  =  .03) and low ICAM-1 (P  = .03) levels with no significant impact of CMV. Elevated sIFNAR2 (P  = .04) and gB antibody (P  =  .06) levels predicted increasing Aix@ 75 (poor vascular health) in healthy adults (R2  =  .4), whilst optimal models for RTR (R2  =  .37) linked low sIFNAR2 and CMV IE-1 antibody levels with lower Aix@ 75 (better vascular health). CMV IE-1 antibody was also protective in relation to PWV in healthy adults (R2  =  .55). Overall, measures of active CMV replication were more predictive of impaired FMD in RTR than standard biomarkers, but increased CMV gB antibodies may be protective.

Understanding human γδ T cell biology toward a better management of cytomegalovirus infection

Cytomegalovirus (CMV) infection is responsible for significant morbidity and mortality in immunocompromised patients, namely solid organ and hematopoietic cell transplant recipients, and can induce congenital infection in neonates. There is currently an unmet need for new management and treatment strategies. Establishment of an anti-CMV immune response is critical in order to control CMV infection. The two main human T cells involved in HCMV-specific response are αβ and non-Vγ9Vδ2 T cells that belong to γδ T cell compartment. CMV-induced non-Vγ9Vδ2 T cells harbor a specific clonal expansion and a phenotypic signature, and display effector functions against CMV. So far, only two main molecular mechanisms underlying CMV sensing have been identified. Non-Vγ9Vδ2 T cells can be activated either by stress-induced surface expression of the γδT cell receptor (TCR) ligand annexin A2, or by a multimolecular stress signature composed of the γδTCR ligand endothelial protein C receptor and co-stimulatory signals such as the ICAM-1-LFA-1 axis. All this basic knowledge can be harnessed to improve the clinical management of CMV infection in at-risk patients. In particular, non-Vγ9Vδ2 T cell monitoring could help better stratify the risk of infection and move forward a personalized medicine. Moreover, recent advances in cell therapy protocols open the way for a non-Vγ9Vδ2 T cell therapy in immunocompromised patients.

The Detection of CMV in Saliva Can Mark a Systemic Infection with CMV in Renal Transplant Recipients

Human cytomegalovirus (CMV) is often transmitted through saliva. The salivary gland is a site of CMV replication and saliva can be used to diagnose congenital CMV infections. CMV replication is monitored in whole blood or plasma in renal transplant recipients (RTR) and associates with clinical disease. However, these assays may not detect replication in the salivary gland and there is little data linking detection in saliva with systemic infection and clinical sequelae. RTR (n = 82) were recruited > 2 years after transplantation. An in-house quantitative PCR assay was used to detect CMV UL54 in saliva samples. CMV DNA was sought in plasma using a commercial assay. Vascular health was predicted using flow mediated dilatation (FMD) and plasma biomarkers. CMV-reactive antibodies were quantified by ELISA and circulating CMV-specific T-cells by an interferon-γ ELISpot assay. Vδ2⁻ γδ T-cells were detected using multicolor flow cytometry reflecting population expansion after CMV infection. The presence of CMV DNA in saliva and plasma associated with plasma levels of antibodies reactive with CMV gB and with populations of circulating Vδ2⁻ γδ T -cells (p < 0.01). T-cells reactive to CMV immediate early (IE)-1 protein were generally lower in patients with CMV DNA in saliva or plasma, but the level of significance varied (p = 0.02–0.16). Additionally, CMV DNA in saliva or plasma associated weakly with impaired FMD (p = 0.06–0.09). The data suggest that CMV detected in saliva reflects systemic infections in adult RTR.

Emerging role of γδ T cells in vaccine-mediated protection from infectious diseases

γδ T cells are fascinating cells that bridge the innate and adaptive immune systems. They have long been known to proliferate rapidly following infection; however, the identity of the specific γδ T cell subsets proliferating and the role of this expansion in protection from disease have only been explored more recently. Several recent studies have investigated γδ T‐cell responses to vaccines targeting infections such as Mycobacterium, Plasmodium and influenza, and studies in animal models have provided further insight into the association of these responses with improved clinical outcomes. In this review, we examine the evidence for a role for γδ T cells in vaccine‐induced protection against various bacterial, protozoan and viral infections. We further discuss results suggesting potential mechanisms for protection, including cytokine‐mediated direct and indirect killing of infected cells, and highlight remaining open questions in the field. Finally, building on current efforts to integrate strategies targeting γδ T cells into immunotherapies for cancer, we discuss potential approaches to improve vaccines for infectious diseases by inducing γδ T‐cell activation and cytotoxicity.

Deciphering the Contribution of γδ T Cells to Outcomes in Transplantation

γδ T cells are a subpopulation of lymphocytes expressing heterodimeric T-cell receptors composed of γ and δ chains. They are morphologically and functionally heterogeneous, innate yet also adaptive in behavior, and exhibit diverse activities spanning immunosurveillance, immunomodulation, and direct cytotoxicity. The specific responses of γδ T cells to allografts are yet to be fully elucidated with evidence of both detrimental and tolerogenic roles in different settings. Here we present an overview of γδ T-cell literature, consider ways in which their functional heterogeneity contributes to the outcomes after transplantation, and reflect on methods to harness their beneficial properties.

HIV patients, healthy aging and transplant recipients can reveal the hidden footprints of CMV

Cytomegalovirus (CMV) is a β-herpesvirus. Latent infections are common in all populations. However age-associated increases in levels of CMV-reactive antibody are testament to repeated reactivations and periods of viral replication. CMV has been associated with several diseases of aging, including vasculopathy and neurocognitive impairment. These conditions occur at a younger age in persons with particularly high burdens of CMV - transplant recipients and people living with HIV. Here we define the "clinical footprints" as immunopathologies triggered by CMV that develop over many years. A high burden of CMV also drives accumulation of multifunctional terminally-differentiated αβ T-cells, a novel population of Vδ2^- γδ T-cells, and a population of CD56^lo NK cells lacking a key regulatory molecule. An understanding of these "immunological footprints" of CMV may reveal how they collectively promote the "clinical footprints" of the virus. This is explored here in transplant recipients, HIV patients and healthy aging.

Immunological Prediction of Cytomegalovirus (CMV) Replication Risk in Solid Organ Transplantation Recipients: Approaches for Regulating the Targeted Anti-CMV Prevention Strategies

The current cytomegalovirus (CMV) prevention strategies in solid organ transplantation (SOT) recipients have contributed towards overcoming the detrimental effects caused by CMV lytic infection, and improving the long-term success rate of graft survival. Although the quantification of CMV in peripheral blood is the standard method, and an excellent end-point for diagnosing CMV replication and modulating the anti-CMV prevention strategies in SOT recipients, a novel biomarker mimicking the CMV control mechanism is required. CMV-specific immune monitoring can be employed as a basic tool predicting CMV infection or disease after SOT, since uncontrolled CMV replication mostly originates from the impairment of immune responses against CMV under immunosuppressive conditions in SOT recipients. Several studies conducted during the past few decades have indicated the possibility of measuring the CMV-specific cell-mediated immune response in clinical situations. Among several analytical assays, the most advancing standardized tool is the QuantiFERON®-CMV assay. The T-Track® CMV kit that uses the standardized enzyme-linked immunospot assay is also widely employed. In addition to these assays, immunophenotyping and intracellular cytokine analysis using flow cytometry (with fluorescence-labeled monoclonal antibodies or peptide-major histocompatibility complex multimers) needs to be adequately standardized and validated for potential clinical applications.