Cytomegalovirus (CMV) infection is a major cause of morbidity and mortality following hematopoietic stem cell transplantation (HSCT). Measuring CMV-specific cellular immunity may improve the risk ...stratification and management of patients. IFN-γ ELISpot assays, based on the stimulation of peripheral blood mononuclear cells with CMV pp65 and IE-1 proteins or peptides, have been validated in clinical settings. However, it remains unclear to which extend the T-cell response to synthetic peptides reflect that mediated by full-length proteins processed by antigen-presenting cells. We compared the stimulating ability of pp65 and IE-1 proteins and corresponding overlapping peptides in 16 HSCT recipients using a standardized IFN-γ ELISpot assay. Paired qualitative test results showed an overall 74.4% concordance. Discordant results were mainly due to low-response tests, with one exception. One patient with early CMV reactivation and graft-versus-host disease, sustained CMV DNAemia and high CD8
counts showed successive negative protein-based ELISpot results but a high and sustained response to IE-1 peptides. Our results suggest that the response to exogenous proteins, which involves their uptake and processing by antigen-presenting cells, more closely reflects the physiological response to CMV infection, while the response to exogenous peptides may lead to artificial in vitro T-cell responses, especially in strongly immunosuppressed patients.
Recurrence of cytomegalovirus reactivation remains a major cause of morbidity and mortality following allogeneic hematopoietic stem cell transplantation. Monitoring cytomegalovirus-specific cellular ...immunity using a standardized assay might improve the risk stratification of patients. A prospective multicenter study was conducted in 175 intermediate- and high-risk allogeneic hematopoietic stem cell transplant recipients under preemptive antiviral therapy. Cytomegalovirus-specific cellular immunity was measured using a standardized IFN-γ ELISpot assay (T-Track® CMV). Primary aim was to evaluate the suitability of measuring cytomegalovirus-specific immunity after end of treatment for a first cytomegalovirus reactivation to predict recurrent reactivation. 40/101 (39.6%) patients with a first cytomegalovirus reactivation experienced recurrent reactivations, mainly in the high-risk group (cytomegalovirus-seronegative donor/cytomegalovirus-seropositive recipient). The positive predictive value of T-Track® CMV (patients with a negative test after the first reactivation experienced at least one recurrent reactivation) was 84.2% in high-risk patients. Kaplan-Meier analysis revealed a higher probability of recurrent cytomegalovirus reactivation in high-risk patients with a negative test after the first reactivation (hazard ratio 2.73; p=0.007). Interestingly, a post-hoc analysis considering T-Track® CMV measurements at day 100 post-transplantation, a time point highly relevant for outpatient care, showed a positive predictive value of 90.0% in high-risk patients. Our results indicate that standardized cytomegalovirus-specific cellular immunity monitoring may allow improved risk stratification and management of recurrent cytomegalovirus reactivation after hematopoietic stem cell transplantation. This study was registered at www.clinicaltrials.gov as #NCT02156479.
Summary
Impaired cytomegalovirus (CMV)‐specific cell‐mediated immunity (CMV‐CMI) is a major cause of CMV reactivation and associated complications in solid‐organ transplantation. Reliably assessing ...CMV‐CMI is desirable to individually adjust antiviral and immunosuppressive therapy. This study aimed to evaluate the suitability of T‐Track® CMV, a novel IFN‐γ ELISpot assay based on the stimulation of peripheral blood mononuclear cells with pp65 and IE‐I CMV proteins, to monitor CMV‐CMI following kidney transplantation. A prospective longitudinal multicenter study was conducted in 86 intermediate‐risk renal transplant recipients. CMV‐CMI, CMV viral load, and clinical complications were monitored over 6 months post‐transplantation. Ninety‐five percent and 88–92% ELISpot assays were positive pre‐ and post‐transplantation, respectively. CMV‐specific response was reduced following immunosuppressive treatment and increased in patients with graft rejection, indicating the ability of the ELISpot assay to monitor patients' immunosuppressive state. Interestingly, median pp65‐specific response was ninefold higher in patients with self‐clearing viral load compared to antivirally treated patients prior to first viral load detection (P < 0.001), suggesting that reactivity to pp65 represents a potential immunocompetence marker. Altogether, T‐Track® CMV is a highly sensitive IFN‐γ ELISpot assay, suitable for the immunomonitoring of CMV‐seropositive renal transplant recipients, and with a potential use for the risk assessment of CMV‐related clinical complications (ClinicalTrials.gov Identifier: NCT02083042).
Recurrence of cytomegalovirus reactivation remains a major cause of morbidity and mortality following allogeneic hematopoietic stem cell transplantation. Monitoring cytomegalovirus-specific cellular ...immunity using a standardized assay might improve the risk stratification of patients. A prospective multicenter study was conducted in 175 intermediate- and high-risk allogeneic hematopoietic stem cell transplant recipients under preemptive antiviral therapy. Cytomegalovirusspecific cellular immunity was measured using a standardized interferon- γ enzyme-linked immunospot assay (T-Track® CMV). The primary aim was to evaluate the suitability of measuring cytomegalovirus-specific immunity after the end of treatment for a first cytomegalovirus reactivation to predict recurrent reactivation. Forty of 101 (39.6%) patients with a first cytomegalovirus reactivation experienced recurrent reactivations, mainly in the high-risk group (cytomegalovirus-seronegative donor/cytomegalovirus-seropositive recipient). The positive predictive value of T-Track® CMV (patients with a negative test after the first reactivation who experienced at least one recurrent reactivation) was 84.2% in high-risk patients. Kaplan-Meier analysis revealed a higher probability of recurrent cytomegalovirus reactivation in high-risk patients with a negative test after the first reactivation (hazard ratio 2.73;
P
=0.007). Interestingly, a
post-hoc
analysis considering T-Track® CMV measurements at day 100 after transplantation, a time point highly relevant for outpatient care, showed a positive predictive value of 90.0% in high-risk patients. Our results indicate that standardized cytomegalovirus-specific cellular immunity monitoring may allow improved risk stratification and management of recurrent cytomegalovirus reactivation after hematopoietic stem cell transplantation. This study was registered at
www.clinicaltrials.gov
as #NCT02156479.
Hey1, Hey2 and HeyL are downstream effectors of the Notch signalling pathway. Hey genes play decisive roles during embryonic development for example in cardiovascular development. However, the ...precise transcriptional programmes and genes, which are affected by each single Hey gene, are still poorly understood. One drawback for the analysis of Hey1, Hey2 or HeyL single gene function is that these genes are co-expressed in many tissues and share a high degree of functional redundancy. Thus, it was necessary to establish a system, which is either devoid of Hey expression, or just comprises one single Hey gene family member. For this, Hey1(fl/fl)/Hey2(-/-)/HeyL(-/-)- as well as Hey-triple- knock out (KO)-ES cells (embryonic stem cells) were generated in this work, because ES cells and their differentiation as EBs (embryoid bodies) represent a valuable tool for the in vitro analysis of embryonic developmental processes. After the establishment of Hey1(fl/fl)/Hey2(-/-)/HeyL(-/-)- and Hey-triple- KO-ES cells, it could be seen by ALP staining and pluripotency marker expression that loss of Hey expression did not affect ES cell pluripotency features. Thus, these ES cells represent bona fide ES cells and could be further used for the differentiation as EBs. Here, differences in gene expression between Hey1(fl/fl)/Hey2(-/-)/HeyL(-/-)- and Hey-triple- KO-ES cells (after the loss of Hey1) could be observed in realtime-RT-PCR analysis for the endodermal marker AFP as well as for neural and myogenic markers in d10 EBs. However, the establishment of inducible Hey1, Hey2 or HeyL ES cell lines will be essential to confirm these findings and to search for novel Hey target genes. To get further insight into the mode of Hey action, the analysis of Hey interaction partners is necessary. One such binding partner, the Bre protein, has previously been found in a yeast-two-hybrid screen. Bre has been described to be a member of two distinct complexes (i.e. the nuclear BRCA1-A complex with a function in DNA damage response and the cytoplasmic BRISC complex), to directly interact with the TNF-receptor and Fas and to interfere with apoptotic signalling. The Hey-Bre interaction could be further corroborated in this work; yet, it was not possible to narrow down the interaction site of Bre with Hey1. It rather seems that non-overlapping parts of the Bre protein may bind to Hey. This interaction may be direct– pointing to more than one interaction site inside the Bre protein – or via a common binding partner such as the endogenous Bre protein itself. Besides the interaction studies, functional assays were performed for a more detailed characterisation of Hey1 and Bre interaction. Here, it could be shown that Hey1 over-expression did not have any influence on Bre sub-cellular localisation. Interestingly, it could be demonstrated that Bre positively interfered with Hey1 repressive function in luciferase assays at three of four promoters analysed. Moreover, interaction with Bre seems to lead to a stabilisation of Hey1. As Bre has been described to modulate the E3-ligase activity intrinsic to the BRCC complex it was analysed whether Bre over-expression results in an ubiquitination of Hey1. Yet, this could not be observed in the present work. Furthermore, an interaction of Bre with ubiquitinated proteins could not be demonstrated in an ubiquitin binding assay. To obtain a better insight into Bre function, Bre LacZ gene trap-ES cells and animals were generated. However, realtime-RT-analyses revealed that these cells and mice did not show a loss of Bre expression on mRNA level indicating that insertion mutagenesis did not occur as expected. However, embryos derived from these mice could nevertheless be used for the detection of tissues with Bre expression by β-galactosidase staining. Bre deficiency on mRNA levels was only achieved after the deletion of the floxed exon 3 resulting in the generation of Bre del-mice. Bre del-mice were fertile and without any obvious phenotype and they were used for the generation of Bre del- and wt-MEFs (murine embryonic fibroblasts). Characterisation of these cells showed that proliferation was not affected after loss of Bre (neither under normal nor under stress conditions). However, loss of Bre notably resulted in a reduction in the BRCA1 DNA damage response, in a slightly increased sensitivity towards apoptosis induction by FasL treatment and in an increase in the K63-poly-ubiquitin content in Bre del-cytoplasmic fractions, probably linked to a change in the BRISC de-ubiquitinase activity. Even though these results have the same tendencies as observed in former studies, the effects in the present work are less striking. Further studies as well as intercrossing of Bre del- to Hey KO-animals will be necessary to further understand the functional relevance of Hey and Bre interaction.
Hey1, Hey2 und HeyL sind Zielgene des Notch Signalwegs und spielen eine entscheidende Rolle während der Embryonalentwicklung, z. B. bei der Bildung des kardiovaskulären Systems. Die genauen Effekte eines jeden einzelnen Hey Gens auf Transkriptionsprogramme und einzelne Gene sind allerdings noch relativ unbekannt. Einer der Gründe hierfür liegt vermutlich in der Koexpression von Hey-Proteinen in vielen Geweben bzw. in der daraus resultierenden funktionellen Redundanz. Daher sollte in dieser Arbeit ein System entwickelt werden, in dem entweder keines oder jeweils nur eines der Hey-Gene intakt ist. Hierzu wurden Hey1fl/fl/Hey2-/-/HeyL-/- und Hey-triple-knock out (KO) ES-Zellen (embryonale Stammzellen) etabliert. ES-Zellen stellen ein hervorragendes Modellsystem für die Embryonalentwicklung dar, weil ihre in vitro Differenzierung als sog. „embryoid bodies“ (EBs) embryonale Entwicklungsprozesse widerspiegelt. Der Verlust der Hey-Genexpression hatte keinen Einfluss auf den Stammzellcharakter der etablierten Zellen, da sowohl die generierten Hey-triple-KO- als auch die Hey1fl/fl/Hey2-/-/HeyL-/--ES-Zellen eine positive ALP-Färbung sowie eine hohe Expression von Pluripotenzmarkern zeigten. Daher konnten die Zellen im Folgenden als EBs differenziert und auf Genexpressionsunterschiede während der Differenzierung untersucht werden. Zwischen Hey1fl/fl/Hey2-/-/HeyL-/-- (mit intakter Hey1-Expression) und Hey-triple- KO- ES Zellen konnten an EB Tag 10 mittels realtime-RT-PCR Unterschiede in der Genexpression für den endodermalen Marker AFP, sowie für neurale und myogene Marker festgestellt werden. Um diese Ergebnisse zu bestätigen, aber auch, um neue Hey Zielgene ausfindig machen zu können, ist jedoch die Etablierung induzierbarer ES-Zellen (für Hey1, Hey2 bzw. HeyL) notwendig. Um einen tieferen Einblick in die Funktionsweise der Hey-Gene gewinnen zu können ist die Untersuchung von Hey Interaktionspartnern wichtig. Das Bre-Protein ist ein solcher Bindepartner und wurde zuvor in einem Yeast-two-hybrid Assay gefunden. Bre ist in zwei verschiedenen Komplexen beschrieben worden: dem nukleären BRCA1-A-Komplex, der eine Rolle bei der Detektion von DNA-Schäden spielt und dem cytoplasmatischen BRISC-Komplex. Es ist außerdem bekannt, dass Bre direkt mit dem TNF-Rezeptor und mit Fas interagiert und die apoptotische Antwort in der Zelle beeinflusst. Die Interaktion zwischen Bre und Hey1 konnte in dieser Arbeit zunächst bestätigt werden; in weiteren Ko-immunpräzipitations-Experimenten war es aber nicht möglich, den Bereich des Bre-Proteins zu bestimmen, der die Interaktion mit Hey1 vermittelt, da verschiedene nicht überlappende Bereiche des Bre-Proteins eine Interaktion mit Hey1 zeigten. Ob es sich hierbei um direkte Interaktionen handelte und Bre somit mehrere Bindestellen für Hey1 aufweist oder ob die Interaktion indirekt über einen gemeinsamen Bindepartner wie z.B. das endogene Bre-Protein selbst vermittelt wird, ist noch nicht geklärt. Für eine weitere Charakterisierung der Interaktion zwischen den beiden Proteinen wurden funktionelle Versuche durchgeführt. Hierbei konnte gezeigt werden, dass die Überexpression von Hey1 keinen Einfluss auf die subzelluläre Lokalisation des Bre Proteins hat. Mit Hilfe von Luziferase Assays konnte aber interessanterweise nachgewiesen werden, dass Bre bei drei von vier untersuchten Promotern positiv auf die Repression durch Hey1 einwirkte. Außerdem scheint die Überexpression von Bre möglicherweise eine Stabilisierung des Hey1-Proteins zu bewirken. Da Bre eine Verstärkung der E3-Ligasefunktion des BRCC-Komplexes zugeschrieben wird, wurde außerdem untersucht, ob die Überexpression von Bre zu einer Ubiquitinylierung von Hey1 führt. Dies konnte allerdings nicht festgestellt werden. Desweiteren konnte in einem Ubiquitin-Bindeassay keine Interaktion von Bre mit anderen ubiquitinylierten Proteinen gezeigt werden. ...
Increasing evidence suggests that impaired cytomegalovirus (CMV)-specific cell-mediated immunity (CMV-CMI) is a major cause of uncontrolled CMV reactivations and associated complications in ...hematopoietic stem cell transplantation (HSCT). No reliable test exists to predict patients at risk of primary and/or recurrent CMV reactivations following HSCT. Accurately assessing CMV-CMI might therefore improve the risk stratification of patients and allow optimizing and individualizing patient care.
This study aimed to evaluate the suitability of a novel IFN-γ ELISpot assay (T-Track® CMV), based on the stimulation of peripheral blood mononuclear cells with T-activated® pp65 and IE-1 CMV proteins, to predict protection from recurrent CMV reactivation following the resolution of a treatment-requiring primary CMV reactivation.
A prospective, longitudinal, observational, multicenter study was conducted in 175 intermediate- and high-risk (Donor (D)+/Recipient (R)+, D+/R-, D-/R+) HSCT recipients (ClinicalTrials.gov ID: NCT02156479). Patients underwent preemptive antiviral therapy per institutional guidelines. CMV DNAemia was analyzed by quantitative PCR. CMV-CMI was measured at day 45, 60, 80, 100 and 120 post-transplantation, as well as at onset and following the end of preemptive treatment. Occurrence of recurrent CMV reactivation was monitored up to 7.5 months post-transplantation. 154/175 patients fulfilling the inclusion/exclusion criteria and having at least one valid T-Track® CMV test result were included in the final analysis.
101/154 (66%) patients experienced at least one (treatment-requiring) CMV reactivation during the observational period. Out of 74 patients (24 D+/R+, 3 D+/R-, 47 D-/R+) who experienced a first CMV reactivation and had a valid ELISpot test result at the end of this primary reactivation, 30 (41%) faced a recurrent CMV reactivation during the observational period. Interestingly, 41/44 patients free of recurrent reactivation had a positive test result (i.e. positive for at least one of pp65- and/or IE-1-specific result) after resolution of the primary CMV reactivation, resulting in a 93% specificity in diagnostic accuracy. Accordingly, a time-to-event analysis indicated a significantly lower incidence of recurrent CMV reactivation in patients with a positive test result (Figure 1; Hazard ratio=5.68; Log-Rank Test, p<0.001). A ROC analysis also demonstrated that pp65-specific response measured following a primary CMV reactivation is a good negative predictor for future CMV reactivation (AUC=0.840 95% CI 0.741-0.939; p<0.001).
Altogether, this novel standardized IFN-γ ELISpot assay allows an improved risk stratification of CMV-related clinical complications, and can support clinicians in the identification and management of patients with increased risk of recurrent CMV reactivation following HSCT.
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