Signature profiles of CMV-specific T-cells in patients with CMV reactivation after hematopoietic SCT

Dynamics of cytomegalovirus-specific T-cell recovery in allogeneic hematopoietic cell transplant recipients using a commercially available flow cytometry assay: A pilot study

BACKGROUND

Cytomegalovirus-specific T-cell-mediated immunity (CMV-CMI) protects from CMV infection in allogeneic hematopoietic cell transplantation (allo-HCT), but to date, there is no validated measure of CMV immunity for this population.

METHODS

In this prospective, observational, pilot study, CMV T-cell responses were evaluated monthly and at onset of graft-versus-host disease (GVHD) or CMV infection in CMV-seropositive allo-HCT recipients using a commercial flow cytometry assay, the CMV inSIGHT T-Cell Immunity Panel (CMV-TCIP). The primary endpoint was the time to first positive CMV-TCIP, defined as percentage of interferon-γ-producing CD4+ or CD8+ CMV-specific T cells >0.2%. Letermovir was prescribed from day +10 to ≥100.

RESULTS

Twenty-eight allo-HCT recipients were enrolled. The median time to first positive CMV-TCIP result was earlier for CD4+ (60 days [interquartile range, IQR 33‒148]) than for CD8+ T cells (96 days [IQR 33‒155]) and longer for haploidentical and mismatched transplant recipients (77 and 96 days, respectively) than for matched donors (45 and 33 days, respectively). CD4+ and CD8+ CMV-CMI recovery was sustained in 10/10 (100%) and 10/11 (91%) patients, respectively, without GVHD, whereas CD4+ and/or CD8+ CMV-CMI was lost in 4/6 and 2/6 patients, respectively, with GVHD requiring steroids. As a predictor of clinically significant CMV infection in patients with low-level CMV reactivation, the sensitivity and negative predictive value of CMV-TCIP were 90% and 87.5%, respectively, for CD4+ CMV-TCIP and 66.7% and 62.5%, respectively, for CD8+ CMV-TCIP.

CONCLUSIONS

There was significant variability in time to CMV-CMI recovery post-HCT, with slower recovery after haploidentical and mismatched HCT. CD4+ CMV-CMI may protect against CS-CMVi, but immunity may be lost with GVHD diagnosis and treatment.

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.

Wnt activation promotes memory T cell polyfunctionality via epigenetic regulator PRMT1

T cell polyfunctionality is a hallmark of protective immunity against pathogens and cancer, yet the molecular mechanism governing it remains mostly elusive. We found that canonical Wnt agonists inhibited human memory CD8+ T cell differentiation while simultaneously promoting the generation of highly polyfunctional cells. Downstream effects of Wnt activation persisted after removal of the drug, and T cells remained polyfunctional following subsequent cell division, indicating the effect is epigenetically regulated. Wnt activation induced a gene expression pattern that is enriched with stem cell-specific gene signatures and upregulation of protein arginine methyltransferase 1 (PRMT1), a known epigenetic regulator. PRMT1+CD8+ T cells are associated with enhanced polyfunctionality, especially the ability to produce IL-2. In contrast, inhibition of PRMT1 ameliorated the effects of Wnt on polyfunctionality. Chromatin immunoprecipitation revealed that H4R3me2a, a permissive transcription marker mediated by PRMT1, increased at the IL-2 promoter loci following Wnt activation. In vivo, Wnt-treated T cells exhibited superior polyfunctionality and persistence. When applied to cytomegalovirus (CMV) donor-seropositive, recipient-seronegative patients (D+/R-) lung transplant patient samples, Wnt activation enhanced CMV-specific T cell polyfunctionality, which is important in controlling CMV diseases. These findings reveal a molecular mechanism governing T cell polyfunctionality and identify PRMT1 as a potential target for T cell immunotherapy.

Human cytomegalovirus infection: A considerable issue following allogeneic hematopoietic stem cell transplantation

Cytomegalovirus (CMV) is an opportunistic virus, whereby recipients are most susceptible following allogeneic hematopoietic stem cell transplantation (allo-HSCT). With the development of novel immunosuppressive agents and antiviral drugs, accompanied with the widespread application of prophylaxis and preemptive treatment, significant developments have been made in transplant recipients with human (H)CMV infection. However, HCMV remains an important cause of short- and long-term morbidity and mortality in transplant recipients. The present review summarizes the molecular mechanism and risk factors of HCMV reactivation following allo-HSCT, the diagnosis of CMV infection following allo-HSCT, prophylaxis and treatment of HCMV infection, and future perspectives. All relevant literature were retrieved from PubMed and have been reviewed.

Preserved specific anti-viral T-cell response but associated with decreased lupus activity in SLE patients with cytomegalovirus infection

OBJECTIVES

SLE is an autoimmune disease characterized by aberrant autoantibody production and immune dysfunctions. Whether the anti-CMV immunity is impaired in SLE patients is poorly understood. We investigated the specific anti-viral T-cell response in SLE patients with CMV infection and its possible impacts on clinical manifestations in lupus.

METHODS

CD28 null T-cell percentages were measured by flow cytometry in 89 SLE patients and 58 healthy controls. A specific anti-CMV CD8 T-cell response was assessed ex vivo by the production of intracellular cytokines in response to CMV phosphoprotein 65 (pp65) by flow cytometry. Clinical manifestations and immune parameters were analysed in SLE patients according to their CMV serostatus.

RESULTS

CD28 null T cells were significantly expanded in SLE patients. When the anti-CMV pp65 CD8 polyfunctional T cell response was analysed, as defined by production of at least three of four functional cytokines or effectors (intracellular IFN-γ, IL-2, TNF-α and surface CD107a), the results demonstrated that it was not impaired in SLE patients. In contrast, when comparing clinical manifestations, there were lower anti-ds-DNA levels and decreased SLEDAI in SLE patients with CMV infection. Furthermore, the expansion of CD4+CD28 null T cells was negatively associated with anti-ds-DNA levels and SLEDAI in these lupus patients.

CONCLUSION

In SLE patients with CMV infection, the specific anti-CMV CD8 T-cell response is preserved but is associated with decreased disease activity and lower anti-DNA levels among these patients, suggesting CMV infection may mitigate lupus activity.

Early T cell reconstitution and cytokine profile may help to guide a personalized management of human cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation

Human cytomegalovirus (HCMV) infection is one of the major causes of mortality and morbidity after allo-hematopoietic stem cell transplantation (HSCT). Antiviral therapies are associated with toxicity and high economic burden. The aim of this retrospective study was to identify allo-HSCT HCMV-seropositive recipients at low risk of clinically significant HCMV infection who could avoid antiviral therapies. Sixty adult patients who underwent allo-HSCT were clustered in two groups: i) 22 (37%) spontaneously controlling HCMV reactivation (Controllers); ii) 38 (63%) developing clinically significant HCMV infection and receiving pre-emptive therapy (Non-Controllers). We analyzed several patient baseline characteristics, total/HCMV-specific CD4⁺ and CD8⁺ T-cell counts and their cytokine production (IFNγ, TNFα, IL2). Controllers presented a higher number of total/HCMV-specific CD4⁺ and CD8⁺ T-cells (P=0.001 and P=0.017 for total CD4⁺ and CD8⁺ T-cells respectively; P<0.001 for HCMV-specific T-cells) and a lower percentage of mono-functional IFNγ-producing HCMV-specific CD8⁺ T-cells (P=0.002). In bi-variable models, the prognostic impact of the percentage of mono-functional HCMV-specific CD8⁺ T-cells on treatment-free survival, adjusted for total/HCMVspecific CD4⁺ and CD8⁺ T-cells, was confirmed. An HCMV-seronegative donor was the only baseline characteristic associated with a clinically significant infection. These data, when confirmed by a larger prospective study, may provide information for guiding the personalized management of HCMV infection in allo-HSCT recipients.

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.

The CD4+ T Cell Response to Human Cytomegalovirus in Healthy and Immunocompromised People

While CD8+ T cells specific for human cytomegalovirus (HCMV) have been extensively studied in both healthy HCMV seropositive carriers and patients undergoing immunosuppression, studies on the CD4+ T cell response to HCMV had lagged behind. However, over the last few years there has been a significant advance in our understanding of the importance and contribution that CMV-specific CD4+ T cells make, not only to anti-viral immunity but also in the potential maintenance of latently infected cells. During primary infection with HCMV in adults, CD4+ T cells are important for the resolution of symptomatic disease, while persistent shedding of HCMV into urine and saliva is associated with a lack of HCMV specific CD4+ T cell response in young children. In immunosuppressed solid organ transplant recipients, a delayed appearance of HCMV-specific CD4+ T cells is associated with prolonged viremia and more severe clinical disease, while in haematopoietic stem cell transplant recipients, it has been suggested that HCMV-specific CD4+ T cells are required for HCMV-specific CD8+ T cells to exert their anti-viral effects. In addition, adoptive T-cell immunotherapy in transplant patients has shown that the presence of HCMV-specific CD4+ T cells is required for the maintenance of HCMV-specific CD8+ T cells. HCMV is a paradigm for immune evasion. The presence of viral genes that down-regulate MHC class II molecules and the expression of viral IL-10 both limit antigen presentation to CD4+ T cells, underlining the important role that this T cell subset has in antiviral immunity. This review will discuss the antigen specificity, effector function, phenotype and direct anti-viral properties of HCMV specific CD4+ T cells, as well as reviewing our understanding of the importance of this T cell subset in primary infection and long-term carriage in healthy individuals. In addition, their role and importance in congenital HCMV infection and during immunosuppression in both solid organ and haemopoietic stem cell transplantation is considered.

Toward Functional Immune Monitoring in Allogeneic Stem Cell Transplant Recipients

Serious viral infections, due to delayed immune reconstitution, are a leading cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Thus, many transplant centers prospectively track cellular immune recovery by evaluating absolute cell numbers and the phenotypic profile of reconstituting T cell subsets to identify individuals who are at highest risk of infection. Conventional assessments, however, fail to measure either the antigen specificity or functional capacity of reconstituting cells-both factors that correlate with endogenous antiviral protection. In this pilot study, we sought to address this limitation by prospectively investigating the tempo of endogenous immune reconstitution in a cohort of 23 pediatric HSCT patients using both quantitative (flow cytometry) and qualitative (IFNγ ELISpot) measures, which we correlated with either the presence or absence of infections associated with cytomegalovirus, adenovirus, Epstein-Barr virus, BK virus, human herpes virus 6, respiratory syncytial virus, parainfluenza, influenza, and human metapneumovirus. We present data spanning 12 months post-transplant demonstrating the influence of conditioning on immune recovery and highlighting the differential impact of active viral replication on the quantity and quality of reconstituting cells. Judicious use of standard (phenotypic) and novel (functional) monitoring strategies can help guide the clinical care and personalized management of allogenic HSCT recipients with infections.

Cytomegalovirus Infections after Hematopoietic Stem Cell Transplantation: Current Status and Future Immunotherapy

Cytomegalovirus (CMV) infection after hematopoietic stem cell transplantation (HSCT) is one of the critical infectious complications related to host immune recovery. The spectrum of CMV infection is quite extensive, from asymptomatic CMV reactivation presenting mainly as CMV DNAemia to fatal CMV diseases involving gut, liver, lungs, or brain. In addition to organ involvement, CMV reactivation can exert indirect effects such as immunosuppression or graft failure that may result in the development of concurrent infectious complications. Currently, preemptive therapy, which is based on PCR-based monitoring of CMV from blood, is a mainstay enabling improvement in CMV-related outcomes. During the past decades, new antiviral drugs, clinical trials for prophylaxis in high-risk groups, and vaccines for preventing CMV infection have been introduced. In addition, data for immunologic monitoring and adoptive immunotherapy have also been accumulated. Here, we review the current status and recent updates in this field, with future perspectives including immunotherapy in HSCT recipients.

Human Cytomegalovirus Latency and Reactivation in Allogeneic Hematopoietic Stem Cell Transplant Recipients

Human cytomegalovirus (HCMV) reactivation is a major infectious cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). HCMV is a ubiquitous beta-herpesvirus which asymptomatically infects immunocompetent individuals but establishes lifelong latency, with the potential to reactivate to a life-threatening productive infection when the host immune system is suppressed or compromised. Opportunistic HCMV reactivation is the most common viral complication following engraftment after HSCT and is associated with a marked increase in non-relapse mortality, which appears to be linked to complex effects on post-transplant immune recovery. This minireview explores the cellular sites of HCMV latency and reactivation in HSCT recipients and provides an overview of the risk factors for HCMV reactivation post-HSCT. The impact of HCMV in shaping post-transplant immune reconstitution and its relationship with patient outcomes such as relapse and graft-versus-host disease will be discussed. Finally, we survey current and emerging strategies to prevent and control HCMV reactivation in HSCT recipients, with recent developments including adoptive T cell therapies to accelerate HCMV-specific T cell reconstitution and new anti-HCMV drug therapy for HCMV reactivation after HSCT.

Deep functional immunophenotyping predicts risk of cytomegalovirus reactivation after hematopoietic cell transplantation

Cytomegalovirus (CMV) is the most common viral infection in hematopoietic cell transplantation (HCT) recipients. We performed deep phenotyping of CMV-specific T cells to predict CMV outcomes following allogeneic HCT. By using 13-color flow cytometry, we studied ex vivo CD8⁺ T-cell cytokine production in response to CMV-pp65 peptides in 3 clinically distinct subgroups of CMV-seropositive HCT patients: (1) Elite Controllers (n = 19): did not have evidence of CMV DNAemia on surveillance testing; (2) Spontaneous Controllers (n = 16): spontaneously resolved low-grade CMV DNAemia without antiviral therapy; and (3) Noncontrollers (NC; n = 21): experienced clinically significant CMV. Two CMV-specific CD8⁺ T-cell functional subsets were strongly associated with risk of CMV: (i) the nonprotective signature (NPS; IL-2^-IFN-γ⁺TNF-α^-MIP-1β⁺), found at increased levels among NC; and (ii) the protective signature (PS; IL-2⁺IFN-γ⁺TNF-α⁺MIP-1β⁺) found at low levels among NC. High levels of the NPS and low levels of PS were associated with an increased 100-day cumulative incidence of clinically significant CMV infection (35% vs 5%; P = .02; and 40% vs 12%; P = .05, respectively). The highest predictive value was observed when these signatures were combined into a composite biomarker consisting of low levels of the PS and high levels of the NPS (67% vs 10%; P < .001). After adjusting for steroid use or donor type, this composite biomarker remained associated with a fivefold increase in the risk of clinically significant CMV infection. CMV-specific CD8⁺ T-cell cytokine signatures with robust predictive value for risk of CMV reactivation should prove useful in guiding clinical decision making in HCT recipients.

Immune Monitoring for CMV in Transplantation

PURPOSE OF REVIEW

Immune monitoring to determine when and how the recovery of cytomegalovirus (CMV)-specific T-cells occurs post-transplantation may help clinicians to risk stratify individuals at risk of complications from CMV. We aimed to review all recent clinical studies using CMV immune monitoring in the pre- and post-transplant setting including the use of recently developed standardized assays (Quantiferon-CMV and the CMV ELISPOT) to better understand in whom, when, and how immune monitoring is best used.

RECENT FINDINGS

Pre-transplant assessment of CMV immunity in solid-organ transplant recipients where CMV seropositive recipients had undetectable cell-mediated responses despite past immunity has shown that they are at a much higher risk of developing CMV reactivation. Post-transplant CMV immune monitoring can guide (shorten or prolong) the duration of antiviral prophylaxis, identify recipients at risk of post-prophylaxis CMV disease, and predict recurrent CMV reactivation. Thus, CMV immune monitoring, in addition to current clinical and DNA-based monitoring for CMV, has the potential to be incorporated into routine clinical care to better improve CMV management in both the stem and solid-organ transplant population.

Impact of Cytomegalovirus Viral Load on Probability of Spontaneous Clearance and Response to Preemptive Therapy in Allogeneic Stem Cell Transplantation Recipients

The optimal viral load threshold at which to initiate preemptive cytomegalovirus (CMV) therapy in hematopoietic cell transplantation (HCT) recipients remains to be defined. In an effort to address this question, we conducted a retrospective study of 174 allogeneic HCT recipients who underwent transplantation at a single center between August 2012 and April 2016. During this period, preemptive therapy was initiated at the discretion of the treating clinician. A total of 109 patients (63%) developed CMV viremia. The median time to reactivation was 17 days (interquartile range, IQR, 7-30 days) post-HCT. A peak viremia ≥150 IU/mL was strongly associated with a reduced probability of spontaneous clearance (relative risk, .16; 95% confidence interval, .1-.27), independent of established clinical risk factors, including CMV donor serostatus, exposure to antithymocyte globulin, and underlying lymphoid malignancy. The median time to clearance of viremia was significantly shorter in those who started therapy at CMV <350 IU/mL (19 days; IQR, 11-35 days) compared with those who started antiviral therapy at higher viremia thresholds (33 days; IQR, 21-42 days; P = .02). The occurrence of treatment-associated cytopenias was frequent but similar in patients who started preemptive therapy at CMV <350 IU/mL and those who started at CMV >350 IU/mL (44% versus 57%; P = .42). Unresolved CMV viremia by treatment day 35 was associated with increased risk of therapeutic failure (32% versus 0%; P = .001). Achieving eradication of CMV viremia by treatment day 35 was associated with a 74% reduction in 1-year nonrelapse mortality (NRM) (adjusted hazard ratio [HR], .26; 95% confidence interval [CI], .1-.8; P = .02), whereas therapeutic failure was associated with a significant increase in the probability of 1-year NRM (adjusted HR, 26; 95% CI, 8-87; P <.0001). We conclude that among allogeneic HCT patients, a peak CMV viremia ≥150 IU/mL is associated with a >80% reduction in the probability of spontaneous clearance independent of ATG administration, CMV donor serostatus, and lymphoid malignancy, and is a reasonable cutoff for preemptive therapy. Delaying initiation of therapy until a CMV value ≥350 IU/mL is associated with more protracted CMV viremia, and unresolved viremia by treatment day 35 is associated with a significant increase in NRM.

Identifying Cytomegalovirus Complications Using the Quantiferon-CMV Assay After Allogeneic Hematopoietic Stem Cell Transplantation

Background

A simple test to identify recovery of CMV-specific T-cell immunity following hematopoietic stem cell transplantation (HSCT) could assist clinicians in managing CMV-related complications.

Methods

In an observational, multicenter, prospective study of 94 HSCT recipients we evaluated CMV-specific T-cell immunity at baseline, 3, 6, 9, and 12 months after transplant using the Quantiferon-CMV, an enzyme-linked immunosorbent spot assay (ELISpot), and intracellular cytokine staining.

Results

At 3 months after HSCT, participants who developed CMV disease (n = 8) compared with CMV reactivation (n = 26) or spontaneous viral control (n = 25) had significantly lower CD8+ T-cell production of interferon-γ (IFN-γ) in response to CMV antigens measured by Quantiferon-CMV (P = .0008). An indeterminate Quantiferon-CMV result had a positive predictive value of 83% and a negative predictive value of 98% for identifying participants at risk of further CMV reactivation. Participants experiencing CMV reactivation compared with patients without CMV reactivation had a reduced proportion of polyfunctional (IFN-γ+/tumor necrosis factor α-positive) CD4+ and CD8+ T cells and a higher proportion of interleukin 2-secreting cells (P = .01 and P = .002, respectively).

Conclusions

Quantifying CMV-specific T-cell immunity after HSCT can identify participants at increased risk of clinically relevant CMV-related outcomes.

A constant companion: immune recognition and response to cytomegalovirus with aging and implications for immune fitness

Approximately 50% of individuals aged 6-49 years in the United States are infected with cytomegalovirus (CMV), with seroprevalence increasing with age, reaching 85-90% by 75-80 years according to Bate et al. (Clin Infect Dis 50 (11): 1439-1447, 2010) and Pawelec et al. (Curr Opin Immunol 24:507-511, 2012). Following primary infection, CMV establishes lifelong latency with periodic reactivation. Immunocompetent hosts experience largely asymptomatic infection, but CMV can cause serious illness in immunocompromised populations, such as transplant patients and the elderly. Control of CMV requires constant immune surveillance, and recent discoveries suggest this demand alters general features of the immune system in infected individuals. Here, we review recent advances in the understanding of the immune response to CMV and the role of CMV in immune aging and fitness, while highlighting the importance of potential confounding factors that influence CMV studies. Understanding how CMV contributes to shaping "baseline" immunity has important implications for a host's ability to mount effective responses to diverse infections and vaccination.

Emerging concepts in cytomegalovirus infection following hematopoietic stem cell transplantation

Despite the refinements in molecular methods for the detection of cytomegalovirus (CMV) and the advent of highly effective preemptive strategies, CMV remains a leading cause of morbidity and mortality in hematopoietic cell transplant (HCT) recipients. CMV can cause tissue-invasive disease including pneumonia, hepatitis, colitis, retinitis, and encephalitis. Mortality in HCT recipients with CMV disease can be as high as 60%. CMV infection has been associated with increased risk of secondary bacterial and fungal infections, increased risk of graft-versus-host disease, and high rates of non-relapse mortality following HCT. The risk of CMV is highly dependent on the donor (D) and the recipient (R) serostatus (D^-/R⁺>D⁺/R⁺>D⁺/R^->D^-/R^-). Among allogeneic HCT recipients, high-dose corticosteroids, T-cell depletion, graft-versus-host disease, and mismatched or unrelated donors constitute the main predisposing factors. However, not all seropositive individuals with these risk factors develop CMV, which strongly suggests that host factors, such as those regulating CMV-specific T-cell responses, play a major role in predisposition to CMV in HCT recipients. Here, we discuss emerging concepts in CMV infection in HCT with emphasis on immunological factors that govern CMV reactivation and the applicability of immune monitoring to understand correlates of pathogenesis and its potential to guide clinical decision making.

Common Variable Immunodeficiency patients with a phenotypic profile of immunosenescence present with thrombocytopenia

Common variable immunodeficiency (CVID) is a heterogeneous group of diseases. Our aim was to define sub-groups of CVID patients with similar phenotypes and clinical characteristics. Using eight-color flow cytometry, we analyzed both B- and T-cell phenotypes in a cohort of 88 CVID patients and 48 healthy donors. A hierarchical clustering of probability binning “bins” yielded a separate cluster of 22 CVID patients with an abnormal phenotype. We showed coordinated proportional changes in naïve CD4+ T-cells (decreased), intermediate CD27− CD28+ CD4+ T-cells (increased) and CD21low B-cells (increased) that were stable for over three years. Moreover, the lymphocytes’ immunophenotype in this patient cluster exhibited features of profound immunosenescence and chronic activation. Thrombocytopenia was only found in this cluster (36% of cases, manifested as Immune Thrombocytopenia (ITP) or Evans syndrome). Clinical complications more frequently found in these patients include lung fibrosis (in 59% of cases) and bronchiectasis (55%). The degree of severity of these symptoms corresponded to more deviation from normal levels with respect to CD21low B-cells, naïve CD4+ and CD27− CD28+ over three years. Moreover, th-cells. Next-generation sequencing did not reveal any common genetic background. We delineate a subgroup of CVID patients with activated and immunosenescent immunophenotype of lymphocytes and distinct set of clinical complications without common genetic background.

Reconstitution of cytomegalovirus-specific T-cell response in allogeneic hematopoietic stem cell recipients: the contribution of six frequently recognized, virus-encoded ORFs

BACKGROUND

The reactivation of human cytomegalovirus (HCMV) in immunosuppressed patients is associated with significant morbidity. Testing HCMV-specific T-cell responses can help determine which patients are at high risk of HCMV disease. We optimized selection of HCMV antigens for detection of T-cell response of patients after allogeneic hematopoietic stem cell transplantation (HSCT) with the aim of identifying patients with insufficient control of HCMV reactivation.

METHODS

T-cell immune response to HCMV was monitored in 30 patients during the first year after HSCT. The HSCT recipients were classified according to their anti-HCMV T-cell response and the presence of HCMV DNA in the blood.

RESULTS

We observed an inverse relationship between the magnitude of HCMV-specific T-cell responses against CMV lysate, phosphoprotein (pp) 65, immediate early-1 (IE-1), UL36, and UL55, but not to US3 and US29 detected by interferon-gamma (IFNγ)- ELISPOT and the level of HCMV DNA in the blood of patients during the 30 days following sampling. The study has revealed that patients who received a graft from a seronegative donor have a lower T-cell response against HCMV and increased probability of HCMV reactivation in comparison to the patients who had received their graft from a seropositive donor.

CONCLUSION

The individual peptide pools and native HCMV antigens were useful for monitoring the time course of the anti-HCMV response by IFNγ-ELISPOT, which proved to have a prognostic value. Besides widely employed peptide pools of pp65 and IE-1, the use of antigens UL36 and UL55, but not US3 or US29, increased sensitivity of the test.

Cytotoxic polyfunctionality maturation of cytomegalovirus-pp65-specific CD4 + and CD8 + T-cell responses in older adults positively correlates with response size

Cytomegalovirus (CMV) infection is one of the most common persistent viral infections in humans worldwide and is epidemiologically associated with many adverse health consequences during aging. Previous studies yielded conflicting results regarding whether large, CMV-specific T-cell expansions maintain their function during human aging. In the current study, we examined the in vitro CMV-pp65-reactive T-cell response by comprehensively studying five effector functions (i.e., interleukin-2, tumor necrosis factor-α, interferon-γ, perforin, and CD107a expression) in 76 seropositive individuals aged 70 years or older. Two data-driven, polyfunctionality panels (IL-2-associated and cytotoxicity-associated) derived from effector function co-expression patterns were used to analyze the results. We found that, CMV-pp65-reactive CD8 + and CD4 + T cells contained similar polyfunctional subsets, and the level of polyfunctionality was related to the size of antigen-specific response. In both CD8 + and CD4 + cells, polyfunctional cells with high cytotoxic potential accounted for a larger proportion of the total response as the total response size increased. Notably, a higher serum CMV-IgG level was positively associated with a larger T-cell response size and a higher level of cytotoxic polyfunctionality. These findings indicate that CMV-pp65-specific CD4 + and CD8 + T cell undergo simultaneous cytotoxic polyfunctionality maturation during aging.

Appearance of cytomegalovirus-specific T-cells predicts fast resolution of viremia post hematopoietic stem cell transplantation

BACKGROUND

Cytomegalovirus (CMV) specific T-cells are known to provide long-term control of CMV reactivation, which is a frequent complication of hematopoietic stem cell transplantation. We have studied 58 pediatric patients after hematopoietic stem cell transplantation who suffered from CMV reactivation to reveal which functional T cell subset is best correlating with successful reactivation resolution and which protects from reactivation episode.

METHODS

Detection of 30 combinatorial subsets of four types of response to ex vivo CMV stimulation (IFNγ secretion, IL-2 secretion, CD40L upregulation and degranulation) that were detectable on either CD8+ or CD4+ T cells through flow cytometry intracellular cytokine staining was used.

RESULTS

We found that the presence of CD8+ dual positive (IFNγ+ and IL-2+) cells is the most accurate functional parameter that can predict fast resolution of CMV reactivation. Next, we show that the presence of CD8+ dual positive (IFNγ+ and IL-2+) and CD8+ IFNγ+ cells provides a protective effect (a hazard risk of 0.28 (confidence interval 0.18 - 0.43) and 0.45 (CI 0.27 - 0.75), respectively) and the presence of corticotherapy increases the risk of reactivation (HR 2.47 (CI 1.82-3.36)). Thus, a patient without corticotherapy and with both of the critical T cell subsets present has a cumulative 19.6 times lower risk of developing CMV reactivation than a patient on corticotherapy and without CD8+ dual positive (IFNγ+ and IL-2+) or CD8+ IFNγ+ cells.

CONCLUSIONS

We have established parameters of CMV specific functional response ex vivo that can be used in assisting clinical management of patients with CMV reactivation. © 2015 International Clinical Cytometry Society.

The immune response to cytomegalovirus in allogeneic hematopoietic stem cell transplant recipients

Approximately, up to 70 % of the human population is infected with cytomegalovirus (CMV) that persists for life in a latent state. In healthy people, CMV reactivation induces the expansion of CMV-specific T cells up to 10 % of the entire T cell repertoire. On the contrary, CMV infection is a major opportunistic viral pathogen that remains a leading cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Due to the delayed CMV-specific immune recovery, the incidence of CMV reactivation during post-transplant period is very high. Several methods are currently available for the monitoring of CMV-specific responses that help in clinical monitoring. In this review, essential aspects in the immune recovery against CMV are discussed to improve the better understanding of the immune system relying on CMV infection and, thereby, helping the avoidance of CMV disease or reactivation following hematopoietic stem cell transplantation with severe consequences for the transplanted patients.

Therapeutic strategies for cytomegalovirus in allogeneic hematopoietic cell transplantation

Cytomegalovirus (CMV) remains a major cause of morbidity and mortality in allogeneic hematopoietic cell transplantation. Advances in surveillance of cytomegalovirus reactivation using sensitive techniques and a preemptive strategy to treat virus reactivation has reduced incidence of cytomegalovirus end organ disease. However, severe immunosuppression associated with extensive T-cell depletion resulting from graft-versus-host disease prevention for cases of mismatched or others such as haploidentical allogeneic hematopoietic cell transplantation (allo-HCT) and graft-versus-host disease therapy itself create clinical challenges in managing cytomegalovirus infection. Novel anticytomegalovirus therapies including newer pharmacologic interventions, vaccines, and adoptive cellular therapies to restore anticytomegalovirus immunity appear promising and are expected to continue to shape our treatment armamentarium. Eradication of CMV disease altogether, rather than simply suppressing viremia, should be the ultimate desirable goal.

Functional patterns of cytomegalovirus (CMV) pp65 and immediate early-1-specific CD8(+) T cells that are associated with protection from and control of CMV DNAemia after allogeneic stem cell transplantation

BACKGROUND

The functional profile of cytomegalovirus (CMV)-specific CD8(+) T cells that associate with protection from and control of CMV DNAemia in allogeneic stem cell transplant (allo-SCT) recipients remains incompletely characterized.

METHODS

We enumerated pp65 and immediate early (IE)-1-specific CD8(+) T cells expressing interferon-gamma, tumor necrosis factor-alpha, and CD107a, by flow cytometry in 94 patients at days +30 and +60 after allo-SCT.

RESULTS

Fifty of 94 patients had CMV DNAemia within the first 100 days after transplant. CMV-specific CD8(+) T-cell responses (of any functional type) were more likely to be detected in patients who did not display CMV DNAemia than in those who did (P = 0.04). Qualitatively, no major differences in the functional signature of CMV-specific CD8(+) T cells were noted between patients who had or did not have CMV DNAemia. Patients displaying levels of polyfunctional CD8(+) T cells at day +30 >0.30 cell/μL had a lower risk of CMV DNAemia (positive predictive value 76%, and negative predictive value 43%).

CONCLUSION

The presence of polyfunctional CD8(+) T cells (either expressing CD107a or not) was associated with lower levels of CMV replication, and higher frequency of self-resolved episodes. The data reported further clarify the role of polyfunctional CD8(+) T cells in control of CMV DNAemia in allo-SCT recipients.

An update on the management and prevention of cytomegalovirus infection following allogeneic hematopoietic stem cell transplantation

ABSTRACT 

A significant progress has been made in deciphering critical aspects of the biology and immunology of CMV infection in the allogeneic stem cell transplantation setting. Genetic traits predisposing to active CMV infection and CMV end-organ disease have begun to be delineated. Reliable molecular assays for CMV DNA load quantitation in body fluids have been developed. Elucidation of immune mechanisms affording control of CMV infection will help to improve the management of active CMV infection. Finally, the advent of new CMV-specific antivirals and promising vaccine prototypes as well as the development of fine procedures for large-scale ex vivo generation of functional CMV-specific T cells for adoptive T cell transfer therapies will certainly minimize the negative impact of CMV on survival in these patients.

Decreased functional T lymphocyte-mediated cytokine responses in patients with chemotherapy-induced neutropenia

OBJECTIVES

The degree of immunosuppression in patients with haematological malignancies treated with chemotherapy is routinely measured as number of circulating cells (preferable neutrophils) in peripheral blood. A parallel decline in the number of T cells is expected, but a possible alteration in their functionality has been less well explored. The ability of T cells to secrete more than one cytokine simultaneously is known to indicate protective immunity. The aim of this study was to determine whether the function of circulating T cells is altered in patients with chemotherapy-induced neutropenia.

DESIGN, SETTING AND SUBJECTS

In this cross-sectional study, we used the FluoroSpot assay to investigate the proportion of T cells secreting either interferon-γ or interleukin-2, or both cytokines simultaneously, after anti-CD3 stimulation. Peripheral blood mononuclear cells from 53 adult patients with chemotherapy-induced neutropenia and 20 healthy individuals were investigated.

RESULTS

There were significantly fewer T cells secreting interferon-γ in patients with neutropenia compared with healthy control subjects (P = 0.02), but the difference was greatest for dual cytokine-secreting T cells (P = 0.001). Furthermore, the amount of secreted cytokine per T cell appeared to be reduced in patients, compared with control subjects.

CONCLUSION

Our results suggest that the functionality of T cells is altered in patients with haematological malignancies with chemotherapy-induced neutropenia. In parallel with a decline in T cell count, this may further increase the risk of severe infections.

Clinical factors influencing phenotype of HCMV-specific CD8+ T cells and HCMV-induced interferon-gamma production after allogeneic stem cells transplantation

Human cytomegalovirus (HCMV) infection causes significant morbidity and mortality after hematopoietic stem cell transplantation (HSCT). In this work, we characterized the phenotype and interferon-gamma (INF-γ) production of HCMV-specific T cells using QuantiFERON-HCMV assay in 26 patients 6 months after HSCT. We analysed whether these two parameters were associated with clinical variables. Our results showed that the patients receiving stem cells from donors ≥40 years old were 12 times more likely to have HCMV-specific CD8+ T cells with "differentiated phenotype" (CD45RA+CCR7+ ≤6.7% and CD28+ ≤30%) than patients grafted from donors <40 years old (OR = 12; P = 0.014). In addition, a detectable IFN-γ production in response to HCMV peptides (cutoff 0.2 IU/mL IFN-γ; "reactive" QuantiFERON-HCMV test) was statistically associated with HCMV replication after transplantation (OR = 11; P = 0.026), recipients ≥40 versus <40 years old (OR = 11; P = 0.026), and the use of peripheral blood versus bone marrow as stem cell source (OR = 17.5; P = 0.024). In conclusion, donor age is the only factor significantly associated with the presence of the "differentiated phenotype" in HCMV-specific CD8+ T cells, whereas HCMV replication after transplantation, recipient age, and stem cell source are the factors associated with the production of IFN-γ in response to HCMV epitopes.

Neuroantigen-Specific CD4 Cells Expressing Interferon-γ (IFN-γ), Interleukin (IL)-2 and IL-3 in a Mutually Exclusive Manner Prevail in Experimental Allergic Encephalomyelitis (EAE)

Experimental allergic encephalomyelitis (EAE) is mediated by neuroantigen-specific pro-inflammatory T cells of the Th1 and Th17 effector class. Th-17 cells can be clearly defined by expression of IL-17, but not IFN-γ, IL-2 or IL-3. Th1 cells do not express IL-17, but it is unclear presently to what extent they co-express the cytokines canonically assigned to Th1 immunity (i.e., IFN-γ, IL-2 and IL-3) and whether CD4 cells producing these cytokines indeed belong to a single Th1 lineage. It is also unclear to what extent the Th1 response in EAE entails polyfunctional T cells that co-express IFN-γ and IL-2. Therefore, we dissected the Th1 cytokine signature of neuroantigen-specific CD4 cells studying at single cell resolution co-expression of IFN-γ, IL-2 and IL-3 using dual color cytokine ELISPOT analysis. Shortly after immunization, in the draining lymph nodes (dLN), the overall cytokine signature of the neuroantigen-specific CD4 cells was highly type 1-polarized, but IFN-γ, IL-2, and IL-3 were each secreted by different CD4 cells in a mutually exclusive manner. This single cell - single cytokine profile was stable through the course of chronic EAE-polyfunctional CD4 cells co-expressing IL-2 and IFN-γ presented less than 5% of the neuroantigen-specific T cells, even in the inflamed CNS itself. The neuroantigen-specific CD4 cells that expressed IFN-γ, IL-2 and IL-3 in a mutually exclusive manner exhibited similar functional avidities and kinetics of cytokine production, but showed different tissue distributions. These data suggest that Th1 cells do not belong to a single lineage, but different Th1 subpopulations jointly mediate Th1 immunity.

Monitoring of human cytomegalovirus and virus-specific T-cell response in young patients receiving allogeneic hematopoietic stem cell transplantation

In allogeneic hematopoietic stem-cell transplantation (HSCT) recipients, outcome of human cytomegalovirus (HCMV) infection results from balance between viral load/replication and pathogen-specific T-cell response. Using a cut-off of 30,000 HCMV DNA copies/ml blood for pre-emptive therapy and cut-offs of 1 and 3 virus-specific CD4⁺ and CD8⁺ T cells/µl blood for T-cell protection, we conducted in 131 young patients a prospective 3-year study aimed at verifying whether achievement of such immunological cut-offs protects from HCMV disease. In the first three months after transplantation, 55/89 (62%) HCMV-seropositive patients had infection and 36/55 (65%) were treated pre-emptively, whereas only 7/42 (17%) HCMV-seronegative patients developed infection and 3/7 (43%) were treated. After 12 months, 76 HCMV-seropositive and 9 HCMV-seronegative patients (cumulative incidence: 90% and 21%, respectively) displayed protective HCMV-specific immunity. Eighty of these 85 (95%) patients showed spontaneous control of HCMV infection without additional treatment. Five patients after reaching protective T-cell levels needed pre-emptive therapy, because they developed graft-versus-host disease (GvHD). HSCT recipients reconstituting protective levels of HCMV-specific T-cells in the absence of GvHD are no longer at risk for HCMV disease, at least within 3 years after transplantation. The decision to treat HCMV infection in young HSCT recipients may be taken by combining virological and immunological findings.

Danon disease: a focus on processing of the novel LAMP2 mutation and comments on the beneficial use of peripheral white blood cells in the diagnosis of LAMP2 deficiency

Danon disease (DD) is a monogenic X-linked disorder characterized by cardiomyopathy, skeletal myopathy and variable degrees of intellectual disability. DD develops due to mutations in the gene encoding lysosomal-associated membrane protein 2 (LAMP2). We report on a family exhibiting the clinical phenotype comprising of hypertrophic cardiomyopathy and ventricular pre-excitation, myopia and mild myopathy in two male patients and cardiomyopathy and myopia in a female patient. The diagnosis of DD in this family was based on the assessment of the clinical phenotypes and the absence of LAMP2 in skeletal and/or cardiac muscle biopsy specimens. Sequence analysis of the LAMP2 gene and its mRNA revealed a novel LAMP2 mutation (c.940delG) in all three patients. Approximately 25% of the female patient's cardiomyocytes were LAMP2 positive apparently due to the unfavorable skewing of X chromosome inactivation. We further performed qualitative LAMP2 immunohistochemistry on peripheral white blood cells using the smear technique and revealed the absence of LAMP2 in the male patients. LAMP2 expression was further assessed in granulocytes, CD4+ and CD8+ T lymphocytes, CD20+ B lymphocytes, CD14+ monocytes and CD56+ natural killer cells by quantitative polychromatic flow cytometry. Whereas the male DD patients lacked LAMP2 in all WBC populations, the female patient expressed LAMP2 in 15.1% and 12.8% of monocytes and granulocytes, respectively. LAMP2 expression ratiometrics of highly vs. weakly expressing WBC populations discriminated the DD patients from the healthy controls. WBCs are thus suitable for initial LAMP2 expression testing when DD is a differential diagnostic option. Moreover, flow cytometry represents a quantitative method to assess the skewing of LAMP2 expression in female heterozygotes. Because LAMP2 is a major protein constituent of the membranes of a number of lysosome-related organelles, we also tested the exocytic capacity of the lytic granules from CD8+ T lymphocytes in the patient samples. The degranulation triggered by a specific stimulus (anti-CD3 antibody) was normal. Therefore, this process can be considered LAMP2 independent in human T cells. The c.940delG mutation results in a putatively truncated protein (p.A314QfsX32), which lacks the transmembrane domain and the cytosolic tail of the wild-type LAMP2. We tested whether this variant becomes exocytosed because of a failure in targeting to late endosomes/lysosomes. Western blotting of cardiac muscle, WBCs and cultured skin fibroblasts (and their culture media) showed no intra- or extracellular truncated LAMP2. By comparing the expression pattern and intracellular targeting in cultured skin fibroblasts of normal LAMP2 isoforms (A, B and C) tagged with green fluorescent protein (GFP) and the A314Qfs32-GFP fusion, we found that the A314Qfs32-GFP protein is not even expressed. These observations suggest that the truncated protein is unstable and is co-translationally or early post-translationally degraded.

Cytomegalovirus viral load and virus-specific immune reconstitution after peripheral blood stem cell versus bone marrow transplantation

Peripheral blood stem cell (PBSC) products contain more T cells and monocytes when compared with bone marrow (BM), leading to fewer bacterial and fungal infections. Cytomegelovirus (CMV) viral load and disease as well as CMV-specific immune reconstitution were compared in patients enrolled in a randomized trial comparing PSBC and BM transplantation. There was a higher rate of CMV infection and disease during the first 100 days after transplantation among PBSC recipients (any antigenemia/DNAemia: PBSC, 63% vs BM, 42%, P = .04; CMV disease: PBSC, 17% vs BM, 4%, P = .03). By 2 years, CMV disease rates were similar. The early increase in CMV events correlated temporarily with lower CMV-specific CD4(+) T helper and CD8(+) cytotoxic T lymphocyte function at 30 days after transplantation in PBSC recipients. By 3 months after transplantation and thereafter, CMV-specific immune responses were similar between BM and PBSC recipients. In conclusion, higher CMV infection and disease rates occurred in PBSC transplant recipients early after transplantation. These differences may be because of a transient delay in CMV-specific immune reconstitution following PBSC transplantation.