Polyfunctional T-Cell Signatures to Predict Protection from Cytomegalovirus after Lung Transplantation

Transcriptional signature of durable effector T cells elicited by a replication defective HCMV vaccine

Human cytomegalovirus (HCMV) is a leading infectious cause of birth defects and the most common opportunistic infection that causes life-threatening diseases post-transplantation; however, an effective vaccine remains elusive. V160 is a live-attenuated replication defective HCMV vaccine that showed a 42.4% efficacy against primary HCMV infection among seronegative women in a phase 2b clinical trial. Here, we integrated the multicolor flow cytometry, longitudinal T cell receptor (TCR) sequencing, and single-cell RNA/TCR sequencing approaches to characterize the magnitude, phenotype, and functional quality of human T cell responses to V160. We demonstrated that V160 de novo induces IE-1 and pp65 specific durable polyfunctional effector CD8 T cells that are comparable to those induced by natural HCMV infection. We identified a variety of V160-responsive T cell clones which exhibit distinctive "transient" and "durable" expansion kinetics, and revealed a transcriptional signature that marks durable CD8 T cells post-vaccination. Our study enhances the understanding of human T-cell immune responses to V160 vaccination.

Distinct T cell polyfunctional profile in SARS-CoV-2 seronegative children associated with endemic human coronavirus cross-reactivity

SARS-CoV-2 infection in children typically results in asymptomatic or mild disease. There is a paucity of studies on SARS-CoV-2 antiviral immunity in African children. We investigated SARS-CoV-2-specific T cell responses in 71 unvaccinated asymptomatic South African children who were seropositive or seronegative for SARS-CoV-2. SARS-CoV-2-specific CD4+ T cell responses were detectable in 83% of seropositive and 60% of seronegative children. Although the magnitude of the CD4+ T cell response did not differ significantly between the two groups, their functional profiles were distinct, with SARS-CoV-2 seropositive children exhibiting a higher proportion of polyfunctional T cells compared to their seronegative counterparts. The frequency of SARS-CoV-2-specific CD4+ T cells in seronegative children was associated with the endemic human coronavirus (HCoV) HKU1 IgG response. Overall, the presence of SARS-CoV-2-responding T cells in seronegative children may result from cross-reactivity to endemic coronaviruses and could contribute to the relative protection from disease observed in SARS-CoV-2-infected children.

Multiparameter Flow Cytometry Monitoring of T Cell Responses

Multiparameter flow cytometry is a common tool for assessing responses of T, B, and other cells to pathogens or vaccines. Such responses are likely to be important for predicting the efficacy of an HIV vaccine, despite the elusive findings in HIV vaccine trials to date. Fortunately, flow cytometry has evolved to be capable of readily measuring 30-40 parameters, providing the ability to dissect detailed phenotypes and functions that may be correlated with disease protection. Nevertheless, technical hurdles remain, and standardization of assays is still largely lacking. Here an optimized protocol for antigen-specific T cell monitoring is presented, with specific variations for particular markers. It covers the analysis of multiple cytokines, cell surface proteins, and other functional markers such as CD107, CD154, CD137, etc. References are given to published panels of 8-28 colors.

Updates in Cytomegalovirus Prevention and Treatment in Solid Organ Transplantation

The authors summarize recent updates in the prevention and management of cytomegalovirus (CMV) in solid organ transplant (SOT) recipients with a focus on CMV seronegative recipients of organs from seropositive donors (CMV D+/R-) who are at highest risk of CMV infection and disease. They discuss advantages of preemptive therapy for CMV disease prevention in CMV D+/R- liver transplant recipients, letermovir for CMV prophylaxis, and updates in the development of monoclonal antibodies and vaccines as immune-based preventative strategies. They review the roles of maribavir and virus-specific T cells for management of resistant or refractory CMV infection in SOT recipients.

Prediction of herpes virus infections after solid organ transplantation: a prospective study of immune function

Introduction

Herpes virus infections are a major concern after solid organ transplantation and linked to the immune function of the recipient. We aimed to determine the incidence of positive herpes virus (cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes simplex virus type 1/2 (HSV-1/2), and varicella zoster virus (VZV)) PCR tests during the first year post-transplantation and assess whether a model including immune function pre-transplantation and three months post-transplantation could predict a subsequent positive herpes virus PCR.

Methods

All participants were preemptively screened for CMV, and EBV IgG-negative participants were screened for EBV during the first year post-transplantation. Herpes virus PCR tests for all included herpes viruses (CMV, EBV, HSV-1/2, and VZV) were retrieved from the Danish Microbiology database containing nationwide PCR results from both hospitals and outpatient clinics. Immune function was assessed by whole blood stimulation with A) LPS, B) R848, C) Poly I:C, and D) a blank control. Cytokine concentrations (TNF-α, IL-1β, IL-6, IL-8, IL-10, IL-12p40, IL-17A, IFN-α, and IFN-γ) were measured using Luminex.

Results

We included 123 liver (54%), kidney (26%), and lung (20%) transplant recipients. The cumulative incidence of positive herpes virus PCR tests was 36.6% (95% CI: 28.1-45.1) during the first year post-transplantation. The final prediction model included recipient age, type of transplantation, CMV serostatus, and change in Poly I:C-induced IL-12p40 from pre-transplantation to three months post-transplantation. The prediction model had an AUC of 77% (95% CI: 61-92). Risk scores were extracted from the prediction model, and the participants were divided into three risk groups. Participants with a risk score <5 (28% of the cohort), 5-10 (45% of the cohort), and >10 (27% of the cohort) had a cumulative incidence of having a positive herpes virus PCR test at 5.8%, 25%, and 73%, respectively (p < 0.001).

Conclusion

In conclusion, the incidence of positive herpes virus PCR tests was high, and a risk model including immune function allowed the prediction of positive herpes virus PCR and may be used to identify recipients at higher risk.

Interferon-gamma FlowSpot assay for the measurement of the T-cell response to cytomegalovirus

Objectives

We describe a new method, FlowSpot, to assess CMV-specific T-cell response by quantification of interferon-gamma (IFN-γ). CMV-specific, T-cell-released IFN-γ was captured by flow beads and measured via flow cytometry. In the present study, we used FlowSpot to assess CMV-specific T-cell response in healthy individuals. The FlowSpot results were compared with those of serological analysis and enzyme-linked immunospot (ELISpot) assay.

Methods

Experimental results and parameter analysis were investigated by using serological, ELISpot, and FlowSpot assays.

Results

The levels of IFN-γ, which is released from CMV-specific T-cells, were measured, and the results and parameter analysis showed a good correlation between FlowSpot and ELISpot. However, FlowSpot was more sensitive and better reflected the strength of IFN-γ secretion than did ELISpot.

Conclusions

Compared to ELISpot, FlowSpot has a high sensitivity and is cost and time effective. Thus, this method can be used in wider clinical and scientific applications.

Distinct T cell functional profiles in SARS-CoV-2 seropositive and seronegative children associated with endemic human coronavirus cross-reactivity

SARS-CoV-2 infection in children typically results in asymptomatic or mild disease. There is a paucity of studies on antiviral immunity in African children. We investigated SARS-CoV-2-specific T cell responses in 71 unvaccinated asymptomatic South African children who were seropositive or seronegative for SARS-CoV-2. SARS-CoV-2-specific CD4+ T cell responses were detectable in 83% of seropositive and 60% of seronegative children. Although the magnitude of the CD4+ T cell response did not differ significantly between the two groups, their functional profiles were distinct, with SARS-CoV-2 seropositive children exhibiting a higher proportion of polyfunctional T cells compared to their seronegative counterparts. The frequency of SARS-CoV-2-specific CD4+ T cells in seronegative children was associated with the endemic human coronavirus (HCoV) HKU1 IgG response. Overall, the presence of SARS-CoV-2-responding T cells in seronegative children may result from cross-reactivity to endemic coronaviruses and could contribute to the relative protection from disease observed in SARS-CoV-2-infected children.

A bivalent CMV vaccine formulated with human compatible TLR9 agonist CpG1018 elicits potent cellular and humoral immunity in HLA expressing mice

There is now convincing evidence that the successful development of an effective CMV vaccine will require improved formulation and adjuvant selection that is capable of inducing both humoral and cellular immune responses. Here, we have designed a novel bivalent subunit vaccine formulation based on CMV-encoded oligomeric glycoprotein B (gB) and polyepitope protein in combination with human compatible TLR9 agonist CpG1018. The polyepitope protein includes multiple minimal HLA class I-restricted CD8⁺ T cell epitopes from different antigens of CMV. This subunit vaccine generated durable anti-viral antibodies, CMV-specific CD4⁺ and CD8⁺ T cell responses in multiple HLA expressing mice. Antibody responses included broad T_H1 isotypes (IgG2a, IgG2b and IgG3) and potently neutralized CMV infection in fibroblasts and epithelial cells. Furthermore, polyfunctional antigen-specific T cell immunity and antiviral antibody responses showed long-term memory maintenance. These observations argue that this novel vaccine strategy, if applied to humans, could facilitate the generation of robust humoral and cellular immune responses which may be more effective in preventing CMV-associated complications in various clinical settings.

Human Cytomegalovirus (CMV) is a significant human pathogen. Generally, in healthy people CMV causes mild symptomatic disease, but during pregnancy CMV can transmit from mother to foetus (1 out of every 200 live births worldwide) and lead to sensorineural hearing loss, vision impairment and central nervous system damage. In transplant patients, CMV can cause serious complications leading to organ rejection and even death. Currently, there is no licensed vaccine available to prevent CMV-associated complications in pregnant women and transplant patients. Here, we have developed a novel bivalent CMV vaccine formulation consisting of recombinant CMVpoly and gB proteins in combination with human compatible adjuvant CpG1018. Preclinical immunogenicity evaluation in multiple HLA expressing mice demonstrated that bivalent CMV vaccine formulation consistently generated robust CMV-specific neutralising antibodies, CD4⁺ and CD8⁺ T cell responses. More importantly, long-term follow-up analysis showed that the CMV vaccine can induce durable CMV-specific humoral and cellular immune responses. Our results support further development of this bivalent subunit CMV vaccine to test safety, immunogenicity and efficacy in humans.

QuantiFERON-Cytomegalovirus Assay for Prediction of Cytomegalovirus Viremia in Kidney Transplant Recipients: Study From High Cytomegalovirus Seroprevalence Country

Background

Early studies showed the utility of pretransplant QuantiFERON-Cytomegalovirus (QF-CMV) assays for CMV-disease prediction post kidney transplant (KT). However, recent data are conflicting.

Methods

This prospective cohort study enrolled adult patients undergoing KT between July 2017 and May 2019. Patients with antithymocyte globulin therapy or negative pretransplant CMV IgG were excluded. QF-CMV assays were performed on transplantation day and one month thereafter, and CMV viral loads were obtained 1, 3, and 6 months posttransplantation. The primary outcome was CMV viremia within 6 months. The QF-CMV assay–posttransplant CMV viremia association was analyzed.

Results

Fifty-five patients were enrolled (male, 58.2%; mean (SD) age, 46.5 (10.2) years). Fifty-two (94.5%) received CMV-seropositive donor kidneys. Over 6 months, 29 patients developed CMV viremia (52.7%), with 14 (25.5%) having significant viremia requiring antiviral therapy. The CMV-viremia incidence of patients with nonreactive and reactive baseline QF-CMV assays did not differ significantly (55.3% and 47.1%; p = 0.573). Among patients with reactive pretransplant QF-CMV assays, there was a trend toward a lower incidence of CMV viremia for those who were persistently reactive at 1 month after KTs, although there was no statistically significant difference (50% vs 83%; p = 0.132).

Conclusions

Our study could not support the use of single-timepoint pretransplant or 1-month posttransplant QF-CMV assays as a predictor for posttransplant CMV viremia in CMV seropositive KT recipients. Investigation of the association between dynamic QF-CMV-status changes and CMV-viremia incidence are needed.

Utility of Cytomegalovirus Cell-Mediated Immunity Assays in Solid Organ Transplantation

Cytomegalovirus (CMV) is one of the most important viral complications after solid organ transplantation (SOT). Current preventive and management strategies rely primarily on serologic and viral load testing and remain suboptimal. To address these issues, multiple techniques to measure CMV-specific cell-mediated immunity (CMI) have been developed and evaluated in clinical studies over the past two decades. These assays show significant promise for the personalization of CMV management. For example, CMI assays can be used to help determine the optimal duration of antiviral prophylaxis or whether antiviral therapy is indicated in patients with low levels of CMV reactivation. However, despite numerous studies showing potential utility, these assays are not yet in widespread routine clinical use. Barriers to adoption include variations in test complexity, standardization, and thresholds for positivity and insufficient interventional clinical trials. Here, we provide an updated assessment of commonly available tests and the clinical utility of CMV-specific CMI testing in SOT recipients.

Longitudinal analyses of development of the immune system during the first five years of life in relation to lifestyle

BACKGROUND

Changes in immune cell composition during the immunological window within the first years after birth are not fully understood, especially the effect that different lifestyles might have on immune cell functionality.

METHODS

Peripheral blood mononuclear cells from mothers and their children at birth and at two anvd five years were analyzed by mass cytometry. Immune cell composition and functionality was analyzed according to family lifestyle (anthroposophic and non-anthroposophic).

RESULTS

We found no significant differences in the proportions of major immune lineages between anthroposophic and non-anthroposophic children at each time point, but there were clear changes over time in the proportions of mononuclear leukocytes, especially in B-cells and T lymphocytes. Phenotypic distances between cord blood and maternal blood were high at birth but decreased sharply the first two years, indicating strong phenotypic convergence with maternal cells. We found that children exhibited similar stimulation responses at birth, but subsequently segregated into two discrete functional trajectories. Trajectory 1 was associated with a decrease in tumor necrosis factor alpha (TNFa) production by CD4⁺ T- and NK-cells, while Trajectory 2 depicted an increase in the production of IL-2 and interferon gamma (INFg) by T-cells. In both trajectories, there was an increase in IL-17A production by T-cells resulting in prominent differences at five years of age.

CONCLUSIONS

This exploratory study suggests that leukocyte frequencies and cell phenotypes change with age in the same way across all children, while functional development follows one of two discrete trajectories that largely segregate by family lifestyle, supporting the hypothesis that early environmental exposures imprint immune cell function which may contribute to IgE sensitization. Our results also support that the first two years are critical for the environmental exposures to imprint the immune cells. Further studies with larger sample sizes are required to validate our findings.

Longitudinal association of cytokine-producing CMV-specific T cells with frailty in HIV-infected and -uninfected men who have sex with men

Background

Chronic cytomegalovirus (CMV) infection has been postulated as a driver of chronic inflammation that has been associated with frailty and other age-related conditions in both HIV-infected (HIV+) and -uninfected (HIV-) people.

Methods

To study the T cell response to CMV as a predictor of onset and maintenance of frailty, baseline CMV-specific T cell responses of 42 men (20 HIV-, 22 HIV+; 21 frail, 21 nonfrail) in the Multicenter AIDS Cohort Study (MACS) were assessed by flow cytometric analysis of cytokine production (IFN-γ, TNF-⍺, and IL-2) in response to overlapping peptide pools spanning 19 CMV open reading frames. The Fried frailty phenotype was assessed at baseline and semiannually thereafter. Times to transition into or out of frailty were compared by tertiles of percentages of cytokine-producing T cells using Kaplan-Meier estimators and the exact log-rank test.

Results

Over a median follow-up of 6.5 (interquartile range: 2) years, faster onset of frailty was significantly predicted by higher (HIV- men) or lower (HIV+ men) percentages of CD4 T cells producing only IFN-γ (IFN-γ-single-producing (SP)), and by lower percentages of IFN-γ-, TNF-⍺-, and IL-2-triple-producing CD8 T cells (HIV- men). Greater maintenance of frailty was significantly predicted by lower percentages of both these T cell subsets in HIV- men, and by lower percentages of IFN-γ-SP CD4 T cells in HIV+ men. The antigenic specificity of IFN-γ-SP CD4 T cells was different between HIV- and HIV+ nonfrail men, as were the correlations between these cells and serum inflammatory markers.

Conclusions

In this pilot study, percentages of CMV-specific T cells predicted the onset and maintenance of frailty in HIV- and HIV+ men. Predictive responses differed by HIV status, which may relate to differential control of CMV reactivation and inflammation by anti-CMV T cell responses.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12979-022-00270-3.

microRNA-378a-3p regulates the progression of hepatocellular carcinoma by regulating PD-L1 and STAT3

Programmed death ligand 1 (PD-L1) plays an essential role in the development or progression of hepatocellular carcinoma (HCC). MicroRNAs (miRNAs) are small RNA molecules that regulate gene expression during normal and pathophysiological events. Here, we explored the functions and detailed mechanisms of miR-378a-3p and PD-L1 in HCC progression. First, miR-378a-3p was selected by analyzing miRNA levels in two HCC Gene Expression Omnibus datasets. We found that miR-378a-3p levels exhibited a downward trend in HCC and were negatively correlated with PD-L1 levels. Additionally, a dual luciferase assay predicted that miR-378a-3p directly targets PD-L1. Moreover, the transfection of miR-378a-3p mimics into Li-7 and HuH-7 cells effectively decreased the PD-L1 mRNA and protein expression levels, and inhibited Treg differentiation in co-culture models by modulating the expression levels of certain cytokines. Furthermore, the overexpression of miR-378a-3p hindered cell proliferation and migration but facilitated apoptosis by repressing STAT3 signaling in HCC cells. In conclusion, miR-378a-3p appears to inhibit HCC tumorigenesis by regulating PD-L1 and STAT3 levels. Thus, miR-378a-3p may be a potential target for HCC therapy.

Cytomegalovirus and other herpesviruses after hematopoietic cell and solid organ transplantation: From antiviral drugs to virus-specific T cells

Herpesviruses can either cause primary infection or may get reactivated after both hematopoietic cell and solid organ transplantations. In general, viral infections increase post-transplant morbidity and mortality. Prophylactic, preemptive, or therapeutically administered antiviral drugs may be associated with serious side effects and may induce viral resistance. Virus-specific T cells represent a valuable addition to antiviral treatment, with high rates of response and minimal side effects. Even low numbers of virus-specific T cells manufactured by direct selection methods can reconstitute virus-specific immunity after transplantation and control viral replication. Virus-specific T cells belong to the advanced therapy medicinal products, and their production is regulated by appropriate legislation; also, strict safety regulations are required to minimize their side effects.

Cytomegalovirus specific polyfunctional T-cell responses expressing CD107a predict control of CMV infection after liver transplantation

Cytomegalovirus (CMV) viral load after liver transplantation (LT) is controlled by cell mediated immune responses (CMI). Quantification of CMV-specific T-cells may identify patients who control CMV spontaneously and avoid expensive and potentially toxic antiviral therapies. Prospective post-LT clinical, virological and immunological monitoring was carried out up to 1-year post-LT in a cohort of adult recipients. The CMV-specific T-cell response was characterized using flow cytometry intracellular cytokine staining in 49 LT recipients-R (79.6% R+, 20.4% R-). CMV infection occurred in 24 patients (18 D+/R+ and 6 D+/R-). Only patients with undetectable polyfunctional CMV-specific CD4+ T-cells developed CMV infection. Predictive models showed that polyfunctional CMV-specific CD4+ T-cells pre-existing before LT are protective for CMV reactivation posttransplantation. Quantitation of CD4+ T-cell responses to CMV may be a useful marker for spontaneous control of viral replication to tailor antiviral prophylaxis after LT.

Functional Consequences of Memory Inflation after Solid Organ Transplantation

CMV is a major infectious complication following solid organ transplantation. Reactivation of CMV leads to memory inflation, a process in which CD8 T cells expand over time. Memory inflation is associated with specific changes in T cell function, including increased oligoclonality, decreased cytokine production, and terminal differentiation. To address whether memory inflation during the first year after transplantation in human subjects alters T cell differentiation and function, we employed single-cell-matched TCRαβ and targeted gene expression sequencing. Expanded T cell clones exhibited a terminally differentiated, immunosenescent, and polyfunctional phenotype whereas rare clones were less differentiated. Clonal expansion occurring between pre- and 3 mo posttransplant was accompanied by enhancement of polyfunctionality. In contrast, polyfunctionality and differentiation state were largely maintained between 3 and 12 mo posttransplant. Highly expanded clones had a higher degree of polyfunctionality than rare clones. Thus, CMV-responsive CD8 T cells differentiated during the pre- to posttransplant period then maintained their differentiation state and functional capacity despite posttransplant clonal expansion.

Mechanisms that allow vaccination against an oncolytic vesicular stomatitis virus-encoded transgene to enhance safety without abrogating oncolysis

Vaccination can prevent viral infections via virus-specific T cells, among other mechanisms. A goal of oncolytic virotherapy is replication of oncolytic viruses (OVs) in tumors, so pre-existing T cell immunity against an OV-encoded transgene would seem counterproductive. We developed a treatment for melanomas by pre-vaccinating against an oncolytic vesicular stomatitis virus (VSV)-encoded tumor antigen. Surprisingly, when the VSV-vectored booster vaccine was administered at the peak of the primary effector T cell response, oncolysis was not abrogated. We sought to determine how oncolysis was retained during a robust T cell response against the VSV-encoded transgene product. A murine melanoma model was used to identify two mechanisms that enable this phenomenon. First, tumor-infiltrating T cells had reduced cytopathic potential due to immunosuppression. Second, virus-induced lymphopenia acutely removed virus-specific T cells from tumors. These mechanisms provide a window of opportunity for replication of oncolytic VSV and rationale for a paradigm change in oncolytic virotherapy, whereby immune responses could be intentionally induced against a VSV-encoded melanoma-associated antigen to improve safety without abrogating oncolysis.

Using Adjuvants to Drive T Cell Responses for Next-Generation Infectious Disease Vaccines

Using adjuvants to drive features of T cell responses to vaccine antigens is an important technological challenge in the design of new and improved vaccines against infections. Properties such as T helper cell function, T cell memory, and CD8+ T cell cytotoxicity may play critical roles in optimal and long-lived immunity through vaccination. Directly manipulating specific immune activation or antigen delivery pathways with adjuvants may selectively augment desired T cell responses in vaccination and may improve the effectiveness and durability of vaccine responses in humans. In this review we outline recently studied adjuvants in their potential for antigen presenting cell and T cell programming during vaccination, with an emphasis on what has been observed in studies in humans as available.

Sticholysin II shows similar immunostimulatory properties to LLO stimulating dendritic cells and MHC-I restricted T cell responses of heterologous antigen

Induction of CD8⁺ T cell responses against tumor cells and intracellular pathogens is an important goal of modern vaccinology. One approach of translational interest is the use of liposomes encapsulating pore-forming proteins (PFPs), such as Listeriolysin O (LLO), which has shown efficacy at priming strong and sustained CD8⁺ T cell responses. Recently, we have demonstrated that Sticholysin II (StII), a PFP from the sea anemone Stichodactyla helianthus, co-encapsulated into liposomes with ovalbumin (OVA) was able to stimulate, antigen presenting cells, antigen-specific CD8⁺ T cells and anti-tumor activity in mice. In the present study, we aimed to compare StII and LLO in terms of their abilities to stimulate dendritic cells and to induce major histocompatibility complex (MHC) class I restricted T cell responses against OVA. Interestingly, StII exhibited similar abilities to LLO in vitro of inducing dendritic cells maturation, as measured by increased expression of CD40, CD80, CD86 and MHC-class II molecules, and of stimulating OVA cross-presentation to a CD8⁺ T cell line. Remarkably, using an ex vivo Enzyme-Linked ImmunoSpot Assay (ELISPOT) to monitor gamma interferon (INF-γ) producing effector memory CD8⁺ T cells, liposomal formulations containing either StII or LLO induced comparable frequencies of OVA-specific INF-γ producing CD8⁺ T cells in mice that were sustained in time. However, StII-containing liposomes stimulated antigen-specific memory CD8⁺ T cells with a higher potential to secrete IFN-γ than liposomes encapsulating LLO. This StII immunostimulatory property further supports its use for the rational design of T cell vaccines against cancers and intracellular pathogens. In summary, this study indicates that StII has immunostimulatory properties similar to LLO, despite being evolutionarily distant PFPs.

Immunoregulatory properties of a crude extraction fraction rich in polysaccharide from Chrysanthemum zawadskii Herbich var. latilobum and its potential role as a vaccine adjuvant

The objective of the current study was to demonstrate the immunostimulatory effects of a polysaccharide isolated from Chrysanthemum zawadskii Herbich var. latilobum leaves (CP) and evaluate its potential as a vaccine adjuvant. Results showed that CP induced maturation of the dendritic cells (DCs). In addition, CP-treated DCs activated naïve T cells to polarized CD4+ and CD8+ T cells and substantially induced the production of IFN-γ and IL-2 in vitro. Furthermore, CP initiated the maturation of DCs via the activation of MAPK and NF-κB signaling pathways. Interestingly, systemic administration of CP-treated DCs pulsed with ovalbumin (OVA) peptides significantly enhanced the immune response in vivo, which included the generation of antigen (OVA)-specific polyfunctional T cells, increased cytotoxic T lymphocyte activity, induction of Th1-mediated humoral immunity, and suppression of tumor growth. Taken together, our study highlighted the immunoregulatory activity of CP as well as its potential as a candidate vaccine adjuvant.

Utility of CMV-Specific Immune Monitoring for the Management of CMV in Solid Organ Transplant Recipients: A Clinical Update

Cytomegalovirus (CMV) is one of the most important opportunistic infections in solid organ transplant (SOT) recipients. However, current techniques used to predict risk for CMV infection fall short. CMV-specific cell mediated immunity (CMI) plays an important role in protecting against CMV infection. There is evidence that assays measuring CMV-CMI might better identify SOT recipients at risk of complications from CMV compared to anti-CMV IgG, which is our current standard of care. Here, we review recently published studies that utilize CMV-CMI, at various points before and after transplantation, to help predict risk and guide the management of CMV infection following organ transplantation. The evidence supports the use of these novel assays to help identify SOT recipients at increased risk and highlights the need for larger prospective trials evaluating these modalities in this high-risk population.

Constant regulation for stable CD8 T-cell functional avidity and its possible implications for cancer immunotherapy

The functional avidity (FA) of cytotoxic CD8 T cells impacts strongly on their functional capabilities and correlates with protection from infection and cancer. FA depends on TCR affinity, downstream signaling strength, and TCR affinity-independent parameters of the immune synapse, such as costimulatory and inhibitory receptors. The functional impact of coreceptors on FA remains to be fully elucidated. Despite its importance, FA is infrequently assessed and incompletely understood. There is currently no consensus as to whether FA can be enhanced by optimized vaccine dose or boosting schedule. Recent findings suggest that FA is remarkably stable in vivo, possibly due to continued signaling modulation of critical receptors in the immune synapse. In this review, we provide an overview of the current knowledge and hypothesize that in vivo, codominant T cells constantly "equalize" their FA for similar function. We present a new model of constant FA regulation, and discuss practical implications for T-cell-based cancer immunotherapy.

CRISPR-Cas9-Edited Tacrolimus-Resistant Antiviral T Cells for Advanced Adoptive Immunotherapy in Transplant Recipients

Viral infections, such as with cytomegalovirus (CMV), remain a major risk factor for mortality and morbidity of transplant recipients because of their requirement for lifelong immunosuppression (IS). Antiviral drugs often cause toxicity and sometimes fail to control disease. Thus, regeneration of the antiviral immune response by adoptive antiviral T cell therapy is an attractive alternative. Our recent data, however, show only short-term efficacy in some solid organ recipients, possibly because of malfunction in transferred T cells caused by ongoing IS. We developed a vector-free clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9-based good manufacturing practice (GMP)-compliant protocol that efficiently targets and knocks out the gene for the adaptor protein FK506-binding protein 12 (FKBP12), required for the immunosuppressive function of tacrolimus. This was achieved by transient delivery of ribonucleoprotein complexes into CMV-specific T cells by electroporation. We confirmed the tacrolimus resistance of our gene-edited T cell products in vitro and demonstrated performance comparable with non-tacrolimus-treated unmodified T cells. The alternative calcineurin inhibitor cyclosporine A can be administered as a safety switch to shut down tacrolimus-resistant T cell activity in case of adverse effects. Furthermore, we performed safety assessments as a prerequisite for translation to first-in-human applications.

Progress and Challenges in the Prevention, Diagnosis, and Management of Cytomegalovirus Infection in Transplantation

Hosts with compromised or naive immune systems, such as individuals living with HIV/AIDS, transplant recipients, and fetuses, are at the highest risk for complications from cytomegalovirus (CMV) infection. Despite substantial progress in prevention, diagnostics, and treatment, CMV continues to negatively impact both solid-organ transplant (SOT) and hematologic cell transplant (HCT) recipients. In this article, we summarize important developments in the field over the past 10 years and highlight new approaches and remaining challenges to the optimal control of CMV infection and disease in transplant settings.

Human Salmonella Typhi exposure generates differential multifunctional cross-reactive T-cell memory responses against Salmonella Paratyphi and invasive nontyphoidal Salmonella

Objective

There are no vaccines for most of the major invasive Salmonella strains causing severe infection in humans. We evaluated the specificity of adaptive T memory cell responses generated after Salmonella Typhi exposure in humans against other major invasive Salmonella strains sharing capacity for dissemination.

Methods

T memory cells from eleven volunteers who underwent controlled oral challenge with wtS. Typhi were characterised by flow cytometry for cross‐reactive cellular cytokine/chemokine effector responses or evidence of degranulation upon stimulation with autologous B‐lymphoblastoid cells infected with either S. Typhi, Salmonella Paratyphi A (PA), S. Paratyphi B (PB) or an invasive nontyphoidal Salmonella strain of the S. Typhimurium serovar (iNTSTy).

Results

Blood T‐cell effector memory (T_EM) responses after exposure to S. Typhi in humans evolve late, peaking weeks after infection in most volunteers. Induced multifunctional CD4⁺ Th1 and CD8⁺ T_EM cells elicited after S. Typhi challenge were cross‐reactive with PA, PB and iNTSTy. The magnitude of multifunctional CD4⁺ T_EM cell responses to S. Typhi correlated with induction of cross‐reactive multifunctional CD8⁺ T_EM cells against PA, PB and iNTSTy. Highly multifunctional subsets and T central memory and T effector memory cells that re‐express CD45 (T_EMRA) demonstrated less heterologous T‐cell cross‐reactivity, and multifunctional Th17 elicited after S. Typhi challenge was not cross‐reactive against other invasive Salmonella.

Conclusion

Gaps in cross‐reactive immune effector functions in human T‐cell memory compartments were highly dependent on invasive Salmonella strain, underscoring the importance of strain‐dependent vaccination in the design of T‐cell‐based vaccines for invasive Salmonella.

Transcriptional Profiling of CD8+ CMV-Specific T Cell Functional Subsets Obtained Using a Modified Method for Isolating High-Quality RNA From Fixed and Permeabilized Cells

Previous studies suggest that the presence of antigen-specific polyfunctional T cells is correlated with improved pathogen clearance, disease control, and clinical outcomes; however, the molecular mechanisms responsible for the generation, function, and survival of polyfunctional T cells remain unknown. The study of polyfunctional T cells has been, in part, limited by the need for intracellular cytokine staining (ICS), necessitating fixation and cell membrane permeabilization that leads to unacceptable degradation of RNA. Adopting elements from prior research efforts, we developed and optimized a modified protocol for the isolation of high-quality RNA (i.e., RIN > 7) from primary human T cells following aldehyde-fixation, detergent-based permeabilization, intracellular cytokines staining, and sorting. Additionally, this method also demonstrated utility preserving RNA when staining for transcription factors. This modified protocol utilizes an optimized combination of an RNase inhibitor and high-salt buffer that is cost-effective while maintaining the ability to identify and resolve cell populations for sorting. Overall, this protocol resulted in minimal loss of RNA integrity, quality, and quantity during cytoplasmic staining of cytokines and subsequent flourescence-activated cell sorting. Using this technique, we obtained the transcriptional profiles of functional subsets (i.e., non-functional, monofunctional, bifunctional, polyfunctional) of CMV-specific CD8+T cells. Our analyses demonstrated that these functional subsets are molecularly distinct, and that polyfunctional T cells are uniquely enriched for transcripts involved in viral response, inflammation, cell survival, proliferation, and metabolism when compared to monofunctional cells. Polyfunctional T cells demonstrate reduced activation-induced cell death and increased proliferation after antigen re-challenge. Further in silico analysis of transcriptional data suggested a critical role for STAT5 transcriptional activity in polyfunctional cell activation. Pharmacologic inhibition of STAT5 was associated with a significant reduction in polyfunctional cell cytokine expression and proliferation, demonstrating the requirement of STAT5 activity not only for proliferation and cell survival, but also cytokine expression. Finally, we confirmed this association between CMV-specific CD8+ polyfunctionality with STAT5 signaling also exists in immunosuppressed transplant recipients using single cell transcriptomics, indicating that results from this study may translate to this vulnerable patient population. Collectively, these results shed light on the mechanisms governing polyfunctional T cell function and survival and may ultimately inform multiple areas of immunology, including but not limited to the development of new vaccines, CAR-T cell therapies, and adoptive T cell transfer.

Highlights from the clinical trials in organ transplantation (CTOT)-20 and CTOT-22 Consortium studies in lung transplant

Long-term survival after lung transplant lags behind that of other commonly transplanted organs, reflecting the current incomplete understanding of the mechanisms involved in the development of posttransplant lung injury, rejection, infection, and chronic allograft dysfunction. To address this unmet need, 2 ongoing National Institute of Allergy and Infectious Disease funded studies through the Clinical Trials in Organ Transplant Consortium (CTOT) CTOT-20 and CTOT-22 were dedicated to understanding the clinical factors and biological mechanisms that drive chronic lung allograft dysfunction and those that maintain cytomegalovirus polyfunctional protective immunity. The CTOT-20 and CTOT-22 studies enrolled 800 lung transplant recipients at 5 North American centers over 3 years. Given the number and complexity of subjects included, CTOT-20 and CTOT-22 utilized innovative data transfers and capitalized on patient-entered data collection to minimize site manual data entry. The data were coupled with an extensive biosample collection strategy that included DNA, RNA, plasma, serum, bronchoalveolar lavage fluid, and bronchoalveolar lavage cell pellet. This Special Article describes the CTOT-20 and CTOT-22 protocols, data and biosample strategy, initial results, and lessons learned through study execution.

Lack of cytomegalovirus (CMV)-specific cell-mediated immune response using QuantiFERON-CMV assay in CMV-seropositive healthy volunteers: fact not artifact

The QuantiFERON-CMV (QF) assay measures cell-mediated immunity against cytomegalovirus (CMV-CMI), which is particularly useful in individuals susceptible to CMV infection such as transplant patients. A positive QF result identifies patients that are better protected against CMV infection. However, the significance of a negative QF result in CMV-seropositive individuals needs to be clarified. CMV-CMI was analyzed in healthy subjects using the QF assay, and, in parallel, the Flow-cytometric Assay of Specific Cell-mediated Immune response in Activated whole blood (FASCIA). FASCIA assay measures T-cell proliferation using CMV lysate as stimulus whereas QF assay use a mix of peptides. A total of 93 healthy volunteers were enrolled, and 13/71 CMV-seropositive individuals (18.3%) showed humoral/cellular discordance using QF assay (CMV+ QF-). Interestingly, with FASCIA assay CD4+ and CD8+ T-cell proliferations were lower in CMV+ QF- than in CMV+ QF+ individuals. Furthermore, CMV+ QF- volunteers had a lower level of anti-CMV IgG than CMV+ QF+ subjects. Discordant CMV+ QF- volunteers can be defined as low responder individuals since they show lower CMV-specific humoral and cellular immune responses in comparison to CMV+ QF+ individuals. Immune discordance shows the high heterogeneity of immunity to CMV in healthy subjects.

A Randomized Dose-Escalating Phase I Trial of a Replication-Deficient Lymphocytic Choriomeningitis Virus Vector-Based Vaccine Against Human Cytomegalovirus

BACKGROUND

A vaccine (HB-101) consisting of 2 nonreplicating lymphocytic choriomeningitis virus (LCMV) vectors expressing the human cytomegalovirus antigens glycoprotein B (gB) and the 65-kD phosphoprotein (pp65), respectively, is in development to prevent cytomegalovirus infection.

METHODS

HB-101 was tested in cytomegalovirus-naive, healthy adults in a randomized, double-blind, placebo-controlled, dose-escalation Phase I trial. Fifty-four subjects received low, medium, or high dose of HB-101 or placebo by intramuscular administration at Month 0, 1, and 3. Safety and immunogenicity were the respective primary and secondary endpoints. Subjects were followed for 12 months after the initial immunization.

RESULTS

Vaccination was associated with transient mild to moderate adverse events. HB-101 administration induced dose-dependent gB- and pp65-specific cellular responses, dominated by pp65-specific CD8 T cells, a high fraction of which were polyfunctional. Two administrations were sufficient to elicit dose-dependent gB-binding and cytomegalovirus-neutralizing antibodies (Abs). Cytomegalovirus-specific immune responses were boosted after each administration. Only 1 of 42 vaccine recipients mounted a transient LCMV vector-neutralizing Ab response.

CONCLUSIONS

HB-101 was well tolerated and induced cytomegalovirus-specific polyfunctional CD8 T-cell and neutralizing Ab responses in the majority of subjects. Lack of vector-neutralizing Ab responses should facilitate booster vaccinations. These results justify further clinical evaluation of this vaccine candidate.

Human Cytomegalovirus Glycoprotein B Nucleoside-Modified mRNA Vaccine Elicits Antibody Responses with Greater Durability and Breadth than MF59-Adjuvanted gB Protein Immunization

A vaccine to prevent maternal acquisition of human cytomegalovirus (HCMV) during pregnancy is a primary strategy to reduce the incidence of congenital disease. The MF59-adjuvanted glycoprotein B (gB) protein subunit vaccine (gB/MF59) is the most efficacious vaccine tested to date for this indication. We previously identified that gB/MF59 vaccination elicited poor neutralizing antibody responses and an immunodominant response against gB antigenic domain 3 (AD-3). Thus, we sought to test novel gB vaccines to improve functional antibody responses and reduce AD-3 immunodominance. Groups of juvenile New Zealand White rabbits were administered 3 sequential doses of the full-length gB protein with an MF59-like squalene-based adjuvant, the gB ectodomain protein (lacking AD-3) with squalene adjuvant, or lipid nanoparticle (LNP)-encapsulated nucleoside-modified mRNA encoding full-length gB. All vaccines were highly immunogenic with similar kinetics and comparable peak gB-binding and functional antibody responses. The AD-3-immunodominant IgG response following human gB/MF59 vaccination was closely mimicked in rabbits. Though gB ectodomain subunit vaccination eliminated targeting of epitopes in AD-3, it did not improve vaccine-elicited neutralizing or nonneutralizing antibody functions. gB nucleoside-modified mRNA-LNP-immunized rabbits exhibited an enhanced durability of vaccine-elicited antibody responses. Furthermore, the gB mRNA-LNP vaccine enhanced the breadth of IgG binding responses against discrete gB peptides. Finally, low-magnitude gB-specific T cell activity was observed in the full-length gB protein and mRNA-LNP groups, though not in ectodomain-vaccinated rabbits. Altogether, these data suggest that the use of gB nucleoside-modified mRNA-LNP vaccines is a viable strategy for improving on the partial efficacy of gB/MF59 vaccination and should be further evaluated in preclinical models.IMPORTANCE Human cytomegalovirus (HCMV) is the most common infectious cause of infant birth defects, resulting in permanent neurological disability for one newborn child every hour in the United States. After more than a half century of research and development, we remain without a clinically licensed vaccine or immunotherapeutic to reduce the burden of HCMV-associated disease. In this study, we sought to improve upon the glycoprotein B protein vaccine (gB/MF59), the most efficacious HCMV vaccine evaluated in a clinical trial, via targeted modifications to either the protein structure or vaccine formulation. Utilization of a novel vaccine platform, nucleoside-modified mRNA formulated in lipid nanoparticles, increased the durability and breadth of vaccine-elicited antibody responses. We propose that an mRNA-based gB vaccine may ultimately prove more efficacious than the gB/MF59 vaccine and should be further evaluated for its ability to elicit antiviral immune factors that can prevent HCMV-associated disease.

Effect of Preemptive Therapy vs Antiviral Prophylaxis on Cytomegalovirus Disease in Seronegative Liver Transplant Recipients With Seropositive Donors: A Randomized Clinical Trial

IMPORTANCE

Despite the use of a cytomegalovirus (CMV) prevention strategy of antiviral prophylaxis for high-risk CMV-seronegative liver transplant recipients with seropositive donors, high rates of delayed-onset postprophylaxis CMV disease occur. An alternate approach, preemptive therapy (initiation of antiviral therapy for early asymptomatic CMV viremia detected by surveillance testing), has not previously been directly compared with antiviral prophylaxis in these patients.

OBJECTIVE

To compare preemptive therapy with antiviral prophylaxis in CMV-seronegative liver transplant recipients with seropositive donors for the prevention of CMV disease.

DESIGN, SETTING, AND PARTICIPANTS

Randomized clinical trial of preemptive therapy vs antiviral prophylaxis in 205 CMV-seronegative liver transplant recipients with seropositive donors aged older than 18 years. The trial was conducted at 6 academic transplant centers in the United States between October 2012 and June 2017, with last follow-up in June 2018.

INTERVENTIONS

Patients were randomized 1:1 to receive either preemptive therapy (valganciclovir, 900 mg, twice daily until 2 consecutive negative tests a week apart) for viremia detected by weekly plasma CMV polymerase chain reaction for 100 days (n = 100) or valganciclovir, 900 mg, daily for 100 days as antiviral prophylaxis (n = 105).

MAIN OUTCOMES AND MEASURES

The primary outcome was incidence of CMV disease by 12 months, defined as CMV syndrome (CMV viremia and clinical or laboratory findings) or end-organ disease. Secondary outcomes included acute allograft rejection, opportunistic infections, graft and patient survival, and neutropenia.

RESULTS

Among 205 patients who were randomized (mean age, 55 years; 62 women [30%]), all 205 (100%) completed the trial. The incidence of CMV disease was significantly lower with preemptive therapy than antiviral prophylaxis (9% [9/100] vs 19% [20/105]; difference, 10% [95% CI, 0.5% to 19.6%]; P = .04]). The incidence of allograft rejection (28% vs 25%; difference, 3% [95% CI, -9% to 15%]), opportunistic infections (25% vs 27%; difference, 2% [95% CI, -14% to 10%]), graft loss (2% vs 2%; difference, <1% [95% CI, -4% to 4%]), and neutropenia (13% vs 10%; difference, 3% [95% CI, -5% to 12%]) did not differ significantly for the preemptive therapy vs antiviral prophylaxis group, respectively. All-cause mortality at last follow-up was 15% in the preemptive therapy vs 19% in the antiviral prophylaxis group (difference, 4% [95% CI, -14% to 6%]; P = .46).

CONCLUSIONS AND RELEVANCE

Among CMV-seronegative liver transplant recipients with seropositive donors, the use of preemptive therapy, compared with antiviral prophylaxis, resulted in a lower incidence of CMV disease over 12 months. Further research is needed to replicate these findings and assess long-term outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01552369.

Immune Correlates of Protection Against Human Cytomegalovirus Acquisition, Replication, and Disease

Human cytomegalovirus (HCMV) is the most common infectious cause of infant birth defects and an etiology of significant morbidity and mortality in solid organ and hematopoietic stem cell transplant recipients. There is tremendous interest in developing a vaccine or immunotherapeutic to reduce the burden of HCMV-associated disease, yet after nearly a half-century of research and development in this field we remain without such an intervention. Defining immune correlates of protection is a process that enables targeted vaccine/immunotherapeutic discovery and informed evaluation of clinical performance. Outcomes in the HCMV field have previously been measured against a variety of clinical end points, including virus acquisition, systemic replication, and progression to disease. Herein we review immune correlates of protection against each of these end points in turn, showing that control of HCMV likely depends on a combination of innate immune factors, antibodies, and T-cell responses. Furthermore, protective immune responses are heterogeneous, with no single immune parameter predicting protection against all clinical outcomes and stages of HCMV infection. A detailed understanding of protective immune responses for a given clinical end point will inform immunogen selection and guide preclinical and clinical evaluation of vaccines or immunotherapeutics to prevent HCMV-mediated congenital and transplant disease.

Cytomegalovirus Infection in Solid Organ and Hematopoietic Cell Transplantation: State of the Evidence

This review focuses on recent advances in the field of cytomegalovirus (CMV). The 2 main strategies for CMV prevention are prophylaxis and preemptive therapy. Prophylaxis effectively prevents CMV infection after solid organ transplantation (SOT) but is associated with high rates of neutropenia and delayed-onset postprophylaxis disease. In contrast, preemptive therapy has the advantage of leading to lower rates of CMV disease and robust humoral and T-cell responses. It is widely used in hematopoietic cell transplant recipients but is infrequently utilized after SOT due to logistical considerations, though these may be overcome by novel methods to monitor CMV viremia using self-testing platforms. We review recent developments in CMV immune monitoring, vaccination, and monoclonal antibodies, all of which have the potential to become part of integrated strategies that rely on viral load monitoring and immune responses. We discuss novel therapeutic options for drug-resistant or refractory CMV infection, including maribavir, letermovir, and adoptive T-cell transfer. We also explore the role of donor factors in transmitting CMV after SOT. Finally, we propose a framework with which to approach CMV prevention in the foreseeable future.

Diagnostic usefulness of the cytomegalovirus (CMV)-specific T cell-based assay for predicting CMV infection after kidney transplant

BACKGROUND/AIMS

We evaluated the usefulness in kidney transplant (KT) candidates of cytomegalovirus (CMV)-specific enzyme-linked immunospot (ELISPOT) assays for predicting the development of post-transplant CMV infections.

METHODS

All adult recipients admitted for living-donor KT between March 2014 and March 2015 were prospectively enrolled except donor CMV-seropositive and recipient seronegative (D+/R-) recipients. All the enrolled patients underwent CMV-specific ELISPOT assays before transplant, and a researcher blinded to the results of these assays examined the patients for CMV infection at least 6 months post-transplant.

RESULTS

Of 133 KT recipients, 44 (33%) developed CMV infections. When we used the cut-off determined by receiver operator characteristic curve, 16 of the 34 patients (47%) with negative pp65-specific ELISPOT results (< 11 spots/200,000 cells) developed CMV infections, whereas 28 of the 99 patients (39%) with positive pp65-specific ELISPOT results at baseline (≥ 11 spots/200,000 cells) developed CMV infections after KT (p = 0.02). Based on the multivariable Cox regression model, negative pp65-specific ELISPOT assay results was an independent risk factor for CMV infection (adjusted hazard ratio [AHR], 1.87; 95% confidence interval [CI], 1.01 to 3.46; p = 0.047) as well as age (AHR, 1.05; 95% CI, 1.01 to 1.08; p = 0.007).

CONCLUSION

Pre-transplant CMV-specific ELISPOT assay appears to predict the development of CMV infections after KT in recipients at moderate risk such as CMV-seropositive recipients (Clinical Trial Registration Number NCT02025335).

Clinical experience with a novel assay measuring cytomegalovirus (CMV)-specific CD4+ and CD8+ T-cell immunity by flow cytometry and intracellular cytokine staining to predict clinically significant CMV events

BACKGROUND

Cytomegalovirus (CMV) infection is one of the most common opportunistic infections following organ transplantation, despite administration of CMV prophylaxis. CMV-specific T-cell immunity (TCI) has been associated with reduced rates of CMV infection. We describe for the first time clinical experience using the CMV T-Cell Immunity Panel (CMV-TCIP), a commercially available assay which measures CMV-specific CD4+ and CD8+ T-cell responses, to predict clinically significant CMV events.

METHODS

Adult (> 18-year-old) patients with CMV-TCIP results and ≥ 1 subsequent assessment for CMV DNAemia were included at Brown University and the University of Maryland Medical Center-affiliated hospitals between 4/2017 and 5/2019. A clinically significant CMV event was defined as CMV DNAemia prompting initiation of treatment. We excluded indeterminate results, mostly due to background positivity, allogeneic hematopoetic cell transplant (HCT) recipients, or patients who were continued on antiviral therapy against CMV irrespective of the CMV-TCIP result, because ongoing antiviral therapy could prevent a CMV event.

RESULTS

We analyzed 44 samples from 37 patients: 31 were solid organ transplant recipients, 4 had hematologic malignancies, 2 had autoimmune disorders. The CMV-protection receiver operating characteristic (ROC) area under the curve (AUC) was significant for %CMV-specific CD4+ (AUC: 0.78, P < 0.001) and borderline for CD8+ (AUC: 0.66, P = 0.064) T-cells. At a cut-off value of 0.22% CMV-specific CD4+ T-cells, positive predictive value (PPV) for protection against CMV was 85% (95%CI 65-96%), and negative predictive value (NPV) was 67% (95%CI 41-87%).

CONCLUSIONS

The CMV-TCIP, in particular %CMV-specific CD4+ T-cells, showed good diagnostic performance to predict CMV events. The CMV-TCIP may be a useful test in clinical practice, and merits further validation in larger prospective studies.

Proteome-wide analysis of T-cell response to BK polyomavirus in healthy virus carriers and kidney transplant recipients reveals a unique transcriptional and functional profile

Objectives

Cellular immunity against BK polyomavirus (BKV)‐encoded antigens plays a crucial role in long‐term protection against virus‐associated pathogenesis in transplant recipients. However, in‐depth understanding on dynamics of these cellular immune responses is required to develop better immune monitoring and immunotherapeutic strategies.

Methods

Here, we have conducted a proteome‐wide analysis of BKV‐specific T‐cell responses in a cohort of 53 healthy individuals and 26 kidney transplant recipients to delineate the functional and transcriptional profile of these effector cells and compared these characteristics to T cells directed against cytomegalovirus, which is also known to cause significant morbidity in transplant recipients.

Results

Profiling of BKV‐specific CD4⁺ and CD8⁺ T cells revealed that kidney transplant recipients with high levels of circulating viraemia showed significantly reduced T‐cell reactivity against large T and/or small T antigens when compared to healthy donors. Interestingly, T cells specific for these antigens showed strong cross‐recognition to orthologous JC virus (JCV) peptides, including those exhibiting varying degrees of sequence identity. Ex vivo functional and phenotypic characterisation revealed that the majority of BKV‐specific T cells from renal transplant recipients expressed low levels of the key transcriptional regulators T‐bet and eomesodermin, which was coincident with undetectable expression of granzyme B and perforin. However, in vitro stimulation of T cells with BKV epitopes selectively enhanced the expression of T‐bet, granzyme B and cellular trafficking molecules (CCR4, CD49d and CD103) with minimal change in eomesodermin and perforin.

Conclusions

These observations provide an important platform for the future development of immune monitoring and adoptive T‐cell therapy strategies for BKV‐associated diseases in transplant recipients, which may also be exploited for similar therapeutic value in JCV‐associated clinical complications.

Association of dengue virus-specific polyfunctional T-cell responses with clinical disease severity in acute dengue infection

INTRODUCTION

Although the role of dengue virus (DENV)-specific T cells in the pathogenesis of acute dengue infection is emerging, the functionality of virus-specific T cells associated with milder clinical disease has not been well studied. We sought to investigate how the functionality of DENV-NS3 and DENV-NS5 protein-specific T cells differ in patients with dengue fever (DF) and dengue hemorrhagic fever (DHF).

METHODS

Using intracellular cytokine assays, we assessed the production of interferon γ (IFNγ), tumor necrosis factor-α (TNF-α), macrophage inflammatory protein-1β (MIP-1β), and CD107a expression in adult patients with acute DF (n = 21) and DHF (n = 22).

RESULTS

Quadruple cytokine-producing, polyfunctional DENV-NS3- and DENV-NS5-specific T cells were more frequent in those with DF when compared to those with DHF. While DENV-NS3- and DENV-NS5-specific T cells in patients with DF expressed IFNγ > TNF-α > MIP-β > CD107a, T cells of those with DHF predominantly expressed CD107a > MIP-1β > IFNγ > TNF-α. Overall production of IFNγ or TNF-α by DENV-NS3- and DENV-NS5-specific T cells was significantly higher in patients with DF. The majority of NS3-specific T cells in patients with DF (78.6%) and DHF (68.9%) were single-cytokine producers; 76.6% of DENV-NS5-specific T cells in those with DF and 77.1% of those with DHF, produced only a single cytokine. However, no significant association was found with polyfunctional T-cell responses and the degree of viraemia.

CONCLUSIONS

Our results suggest that the functional phenotype of DENV-specific T cells are likely to associate with clinical disease severity.

A Randomized Study of Quantiferon CMV-directed Versus Fixed-duration Valganciclovir Prophylaxis to Reduce Late CMV After Lung Transplantation

BACKGROUND

We provide the results of the first interventional study of cytomegalovirus (CMV)-specific immune monitoring to direct the length of antiviral prophylaxis in lung transplantation (LTx).

METHODS

Patients (n = 118) at risk of CMV infection were randomized 1:2 to either 5 months or variable length valganciclovir prophylaxis (5-11 mo post-LTx), as determined by the QuantiFERON (QFN)-CMV assay. Patients with a negative QFN-CMV assay (< 0.2 IU/mL) received prolonged valganciclovir prophylaxis.

RESULTS

The primary endpoint that was the incidence of CMV infection in the lung allograft within 18 months of LTx was significantly reduced in the QFN-CMV directed arm (37% versus 58%, P = 0.03). Secondary endpoints that included blood viremia, acute rejection, and chronic lung allograft dysfunction did not differ between the 2 arms. Of the 80/118 patients who ceased antiviral prophylaxis at 5 months, the incidence of viremia (> 600 copies/mL) within the blood was significantly reduced in patients with a positive QFN-CMV assay compared with those without protective immunity (13% versus 67%, P = 0.0003), as was the incidence of severe viremia (> 10 000 copies/mL) (3% versus 50%, P < 0.001). Ceasing antiviral prophylaxis at 11 months in patients with a negative assay was associated with a 25% incidence of late CMV viremia.

CONCLUSIONS

Cytomegalovirus immune monitoring allows an individualized approach to CMV prophylaxis and reduces late CMV infection within the lung allograft.

Deep Profiling of the CD8+ T-cell Compartment Identifies Activated Cell Subsets and Multifunctional Responses Associated With Control of Cytomegalovirus Viremia

BACKGROUND

Human cytomegalovirus (HCMV) is a common opportunistic pathogen in transplant recipients. Patterns of viremia and reactivation are influenced by the host immune response, including CD8 T cells. However, the cellular deficits or phenotypic differences that account for differential outcomes during HCMV viremia are incompletely understood.

METHODS

Peripheral blood mononuclear cells were collected from 20 transplant recipients (10 viremia controllers and 10 noncontrollers) at onset of HCMV viremia and 4 weeks postonset. We used mass cytometry to perform in-depth characterization of cell surface and intracellular CD8 T cell markers and to compare frequencies of these cells between groups.

RESULTS

Deep profiling identified 2 central memory T cell subsets at onset and 5 terminally differentiated memory T (TEMRA) cell subsets at 4 weeks that were associated with control of HCMV viremia, in addition to 6 TEMRA subsets at onset and 4 weeks associated with relapsing or remitting HCMV viremia. In general, CD8 T-cell clusters associated with poorly controlled HCMV viremia lacked markers of activation or terminal differentiation including CD38, CD69, CD25, CD57, and HLA-DR. We also measured the production of 8 HCMV-specific effector molecules (TNFα, IFNγ, interleukin 2, granzyme B, perforin, macrophage inflammatory protein 1β, interleukin 10, and CD107a) in CD8 T cells. Viremia controllers had greater diversity of HCMV-specific multifunctional responses at both time points, including significantly higher frequencies of HCMV-specific TNFαIFNγ CD8 T cells at onset. These multifunctional cells had a phenotype consistent with activated TEM/TEMRA cells.

CONCLUSIONS

Uncontrolled CMV viremia is associated with specific clusters of memory T-cell subsets and lower frequencies of HCMV-specific multifunctional CD8 T cells.

Naturally processed HLA-DR3-restricted HHV-6B peptides are recognized broadly with polyfunctional and cytotoxic CD4 T-cell responses

Human herpes virus 6B (HHV-6B) is a widespread virus that infects most people early in infancy and establishes a chronic life-long infection with periodic reactivation. CD4 T cells have been implicated in control of HHV-6B, but antigenic targets and functional characteristics of the CD4 T-cell response are poorly understood. We identified 25 naturally processed MHC-II peptides, derived from six different HHV-6B proteins, and showed that they were recognized by CD4 T-cell responses in HLA-matched donors. The peptides were identified by mass spectrometry after elution from HLA-DR molecules isolated from HHV-6B-infected T cells. The peptides showed strong binding to matched HLA alleles and elicited recall T-cell responses in vitro. T-cell lines expanded in vitro were used for functional characterization of the response. Responding cells were mainly CD3⁺ CD4⁺ , produced IFN-γ, TNF-α, and low levels of IL-2, alone or in combination, highlighting the presence of polyfunctional T cells in the overall response. Many of the responding cells mobilized CD107a, stored granzyme B, and mediated specific killing of peptide-pulsed target cells. These results highlight a potential role for polyfunctional cytotoxic CD4 T cells in the long-term control of HHV-6B infection.

BKV Clearance Time Correlates With Exhaustion State and T-Cell Receptor Repertoire Shape of BKV-Specific T-Cells in Renal Transplant Patients

Reactivation of the BK polyomavirus is known to lead to severe complications in kidney transplant patients. The current treatment strategy relies on decreasing the immunosuppression to allow the immune system to clear the virus. Recently, we demonstrated a clear association between the resolution of BKV reactivation and reconstitution of BKV-specific CD4⁺ T-cells. However, which factors determine the duration of viral infection clearance remains so far unclear. Here we apply a combination of in-depth multi-parametric flow cytometry and NGS-based CDR3 beta chain receptor repertoire analysis of BKV-specific T-cells to a cohort of 7 kidney transplant patients during the clinical course of BKV reactivation. This way we followed TCR repertoires at single clone levels and functional activity of BKV-specific T-cells during the resolution of BKV infection. The duration of BKV clearance did not depend on the number of peripheral blood BKV-specific T-cells nor on a few immunodominant BKV-specific T-cell clones. Rather, the T-cell receptor repertoire diversity and exhaustion status of BKV-specific T-cells affected the duration of viral clearance: high clonotype diversity and lack of PD1 and TIM3 exhaustion markers on BKV-specific T-cells was associated with short clearance time. Our data thus demonstrate how the diversity and the exhaustion state of the T-cells can determine the clinical course of BKV infection.

Diagnostic performance of cytomegalovirus (CMV) immune monitoring with ELISPOT and QuantiFERON-CMV assay in kidney transplantation: A PRISMA-compliant article

BACKGROUND

Cytomegalovirus (CMV) infection is part of major infection complications following kidney transplantation. However, more rapid and low-complexity assays are needed for CMV infection. Our study is to investigate the diagnostic efficacy of 2 novel tests, CMV-ELISPOT and QuantiFERON-CMV tests, in CMV DNA viremia and CMV infection following renal transplant.

METHODS

We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials and the Web of Science. Case-control or cohort study designed to explore the CMV-ELISPOT and/or QuantiFERON-CMV tests in the recipients with CMV infection was considered to be eligible for this study. Sensitivity (SEN), specificity (SPE), diagnostic odds ratio (DOR), and summary receiver-operating characteristic (SROC) curves were calculated.

RESULTS

We selected a total of 12 articles for systematic review and 11 of them were included in meta-analysis. For CMV-pp65 assay, the pooled SEN, SPE, and DOR were 0.73 (95% confidence interval [CI], 0.67-0.78), 0.61 (95% CI, 0.56-0.65), and 4.46 (95% CI, 3.11-6.39), respectively. For CMV-IE-1 assay, the pooled SEN, SPE, and DOR were 0.84 (95% CI, 0.78-0.88), 0.46 (95% CI, 0.42-0.51), and 5.07 (95% CI, 3.26-7.89), respectively, whereas the pooled SEN, SPE, and DOR of QuantiFERON-CMV test were 0.38 (95% CI, 0.28-0.49), 0.38 (95% CI, 0.32-0.44), and 1.02 (95% CI, 0.17-6.00).

CONCLUSIONS

We reported that CMV-ELISPOT tests, including CMV-pp65 and CMV-IE-1, perform well in the diagnosis and prediction of CMV infection in renal transplant recipients, whereas QuantiFERON-CMV test needs further exploration.

Impaired Cytomegalovirus Immunity in Idiopathic Pulmonary Fibrosis Lung Transplant Recipients with Short Telomeres

RATIONALE

Cytomegalovirus (CMV)-related morbidities remain one of the most common complications after lung transplantation and have been linked to allograft dysfunction, but the factors that predict high risk for CMV complications and effective immunity are incompletely understood.

OBJECTIVES

To determine if short telomeres in idiopathic pulmonary fibrosis (IPF) lung transplant recipients (LTRs) predict the risk for CMV-specific T-cell immunity and viral control.

METHODS

We studied IPF-LTRs (n = 42) and age-matched non-IPF-LTRs (n = 42) and assessed CMV outcomes. We measured lymphocyte telomere length and DNA sequencing, and assessed CMV-specific T-cell immunity in LTRs at high risk for CMV events, using flow cytometry and fluorescence in situ hybridization.

MEASUREMENTS AND MAIN RESULTS

We identified a high prevalence of relapsing CMV viremia in IPF-LTRs compared with non-IPF-LTRs (69% vs. 31%; odds ratio, 4.98; 95% confidence interval, 1.95-12.50; P < 0.001). Within this subset, IPF-LTRs who had short telomeres had the highest risk of CMV complications (P < 0.01) including relapsing-viremia episodes, end-organ disease, and CMV resistance to therapy, as well as shorter time to viremia versus age-matched non-IPF control subjects (P < 0.001). The short telomere defect in IPF-LTRs was associated with significantly impaired CMV-specific proliferative responses, T-cell effector functions, and induction of the major type-1 transcription factor T-bet (T-box 21;TBX21).

CONCLUSIONS

Because the short telomere defect has been linked to the pathogenesis of IPF in some cases, our data indicate that impaired CMV immunity may be a systemic manifestation of telomere-mediated disease in these patients. Identifying this high-risk subset of LTRs has implications for risk assessment, management, and potential strategies for averting post-transplant CMV morbidities.

The Third International Consensus Guidelines on the Management of Cytomegalovirus in Solid-organ Transplantation

Despite recent advances, cytomegalovirus (CMV) infections remain one of the most common complications affecting solid organ transplant recipients, conveying higher risks of complications, graft loss, morbidity, and mortality. Research in the field and development of prior consensus guidelines supported by The Transplantation Society has allowed a more standardized approach to CMV management. An international multidisciplinary panel of experts was convened to expand and revise evidence and expert opinion-based consensus guidelines on CMV management including prevention, treatment, diagnostics, immunology, drug resistance, and pediatric issues. Highlights include advances in molecular and immunologic diagnostics, improved understanding of diagnostic thresholds, optimized methods of prevention, advances in the use of novel antiviral therapies and certain immunosuppressive agents, and more savvy approaches to treatment resistant/refractory disease. The following report summarizes the updated recommendations.

Multiantigenic Modified Vaccinia Virus Ankara Vaccine Vectors To Elicit Potent Humoral and Cellular Immune Reponses against Human Cytomegalovirus in Mice

As human cytomegalovirus (HCMV) is a common cause of disease in newborns and transplant recipients, developing an HCMV vaccine is considered a major public health priority. Yet an HCMV vaccine candidate remains elusive. Although the precise HCMV immune correlates of protection are unclear, both humoral and cellular immune responses have been implicated in protection against HCMV infection and disease. Here we describe a vaccine approach based on the well-characterized modified vaccinia virus Ankara (MVA) vector to stimulate robust HCMV humoral and cellular immune responses by an antigen combination composed of the envelope pentamer complex (PC), glycoprotein B (gB), and phosphoprotein 65 (pp65). We show that in mice, multiantigenic MVA vaccine vectors simultaneously expressing all five PC subunits, gB, and pp65 elicit potent complement-independent and complement-dependent HCMV neutralizing antibodies as well as mouse and human MHC-restricted, polyfunctional T cell responses by the individual antigens. In addition, we demonstrate that the PC/gB antigen combination of these multiantigenic MVA vectors can enhance the stimulation of humoral immune responses that mediate in vitro neutralization of different HCMV strains and antibody-dependent cellular cytotoxicity. These results support the use of MVA to develop a multiantigenic vaccine candidate for controlling HCMV infection and disease in different target populations, such as pregnant women and transplant recipients.IMPORTANCE The development of a human cytomegalovirus (HCMV) vaccine to prevent congenital disease and transplantation-related complications is an unmet medical need. While many HCMV vaccine candidates have been developed, partial success in preventing or controlling HCMV infection in women of childbearing age and transplant recipients has been observed with an approach based on envelope glycoprotein B (gB). We introduce a novel vaccine strategy based on the clinically deployable modified vaccinia virus Ankara (MVA) vaccine vector to elicit potent humoral and cellular immune responses by multiple immunodominant HCMV antigens, including gB, phosphoprotein 65, and all five subunits of the pentamer complex. These findings could contribute to development of a multiantigenic vaccine strategy that may afford more protection against HCMV infection and disease than a vaccine approach employing solely gB.

Temporal dynamics of the lung and plasma viromes in lung transplant recipients

The human virome plays an important role for the clinical outcome of lung transplant recipients (LTRs). While pathogenic viruses may cause severe infections, non-pathogenic viruses may serve as potential markers for the level of immunosuppression. However, neither the complexity of the virome in different compartments nor the dynamics of the virus populations posttransplantation are yet understood. Therefore, in this study the virome was analyzed by metagenomic sequencing in simultaneously withdrawn bronchoalveolar lavage (BAL) and plasma samples of 15 LTRs. In seven patients, also follow-up samples were investigated for abundance and dynamics of virus populations posttransplantation. Five eukaryotic and two prokaryotic virus families were identified in BAL, and nine eukaryotic and two prokaryotic families in plasma. Anelloviruses were the most abundant in both compartments, followed by Herpes- and Coronaviruses. Virus abundance was significantly higher in LTRs than in healthy controls (Kruskal-Wallis test, p<0.001). Up to 48 different anellovirus strains were identified within a single LTR. Analyses in the follow-up patients revealed for the first time a highly complex and unique dynamics of individual anellovirus strains in the posttransplantation period. The abundance of anelloviruses in plasma was inversely correlated with that of other eukaryotic viruses (Pearson correlation coefficient r = -0.605; p<0.05). A broad spectrum of virus strains co-exists in BAL and plasma of LTRs. Especially for the anelloviruses, a high degree of co-infections and a highly individual and complex dynamics after transplantation was observed. The biological impact of these findings and their relation to clinical variables remain to be elucidated by future analyses.

Viral infections in solid organ transplant recipients: novel updates and a review of the classics

PURPOSE OF REVIEW

To summarize new discoveries in viral pathogenesis and novel therapeutic and prophylactic strategies in organ transplant recipients.

RECENT FINDINGS

For decades, prophylaxis of cytomegalovirus (CMV) has been the standard preventive strategy, but new clinical trials are expected to determine the advantages of preemptive therapy over prophylaxis. Novel anti-CMV agents, such as maribavir and letermovir, are being studied for the treatment of resistant/refractory CMV as alternatives to foscarnet and cidofovir. CMV immune monitoring may offer individualized management plans. Epstein-Barr virus infections in transplant recipients are difficult to prevent and treat, though recent data suggest possible merit to pretransplant rituximab among high-risk transplant recipients. We review the groundbreaking HIV-to-HIV organ transplant trials, which are expected to revolutionize the care of HIV-infected individuals. Finally, we review topical developments in human herpesvirus 8, Zika virus, RNA respiratory viruses, adenovirus, norovirus, and polyoma viruses in organ transplantation.

SUMMARY

Ongoing trials to optimize CMV prophylaxis and treatment, and outcomes of HIV-to-HIV organ transplantation in the United States, have significant implications to optimize management of these viruses in transplant recipients. Assessment of new antivirals and antiviral strategies, such as adoptive immunotherapy, is warranted for refractory viral infections.