Potential beneficial effects of cytomegalovirus infection after transplantation

Cytomegalovirus (CMV) infection can cause significant complications after transplantation, but recent emerging data suggest that CMV may paradoxically also exert beneficial effects in two specific allogeneic transplant settings. These potential benefits have been underappreciated and are therefore highlighted in this review. First, after allogeneic hematopoietic stem cell transplantation (HSCT) for acute myeloid leukemia (AML) using T-cell and natural killer (NK) cell-replete grafts, CMV reactivation is associated with protection from leukemic relapse. This association was not observed for other hematologic malignancies. This anti-leukemic effect might be mediated by CMV-driven expansion of donor-derived memory-like NKG2C+ NK and Vδ2negγδ T-cells. Donor-derived NK cells probably recognize recipient leukemic blasts by engagement of NKG2C with HLA-E and/or by the lack of donor (self) HLA molecules. Vδ2negγδ T cells probably recognize as yet unidentified antigens on leukemic blasts via their TCR. Second, immunological imprints of CMV infection, such as expanded numbers of Vδ2negγδ T cells and terminally differentiated TCRαβ+ T cells, as well as enhanced NKG2C gene expression in peripheral blood of operationally tolerant liver transplant patients, suggest that CMV infection or reactivation may be associated with liver graft acceptance. Mechanistically, poor alloreactivity of CMV-induced terminally differentiated TCRαβ+ T cells and CMV-induced IFN-driven adaptive immune resistance mechanisms in liver grafts may be involved. In conclusion, direct associations indicate that CMV reactivation may protect against AML relapse after allogeneic HSCT, and indirect associations suggest that CMV infection may promote allograft acceptance after liver transplantation. The causative mechanisms need further investigations, but are probably related to the profound and sustained imprint of CMV infection on the immune system

High numbers of differentiated CD28null CD8+ T cells are associated with a lowered risk for late rejection and graft loss after kidney transplantation

BACKGROUND: The hypothesis was tested that parameters of an aged T-cell compartment associate with the risk for late rejection after kidney transplantation. METHODS: Recipients of a kidney transplant in the period 2007-2013 were (N = 365) were included. T cells were characterized prior to transplantation by flow cytometry as naive (CD45RO-CCR7+), central-memory (CD45RO+CCR7+), effector-memory (CD45RO-CCR7-) or terminally differentiated CD8+ Temra (CD45RO-/CCR7-/CD28-) cells. T cell telomere length and thymic output were assessed prior to transplantation in 202 recipients. Follow-up was until December 2018. The date of the first time of biopsy-proven late rejection (>6 months after transplantation) was used to calculate the rejection-free survival time. RESULTS: Fifty cases of biopsy-proven rejection were recorded. Thymic output and T cell telomere length did not associate with late rejection-free survival. However, the percentage and absolute numbers of CD8+Temra and CD28null CD8+ T cells were significantly lower in patients with late rejection. Specifically, in the highest tertile of percentages of CD28null CD8+ T cells, the cumulative incidence of late rejection at 5 and 10 years was only 5% and 8% compared to 16% and 20% in the middle to lowest tertile (p = 0.002). Multivariate proportional hazard analysis showed that percentage and absolute number of CD28null CD8+ T cells remained significantly associated with late rejection and rejection-related graft loss. CONCLUSION: High numbers of differentiated CD28null CD8+ T cells decrease the risk for late rejection and rejection-related graft loss after kidney transplantation

End-stage renal disease causes skewing in the TCR Vβ-repertoire primarily within CD8+ T Cell subsets

A broad T cell receptor (TCR-) repertoire is required for an effective immune response. TCR-repertoire diversity declines with age. End-stage renal disease (ESRD) patients have a prematurely aged T cell system which is associated with defective T cell-mediated immunity. Recently, we showed that ESRD may significantly skew the TCR Vβ-repertoire. Here, we assessed the impact of ESRD on the TCR Vβ-repertoire within different T cell subsets using a multiparameter flow-cytometry-based assay, controlling for effects of aging and CMV latency. Percentages of 24 different TCR Vβ-families were tested in circulating naive and memory T cell subsets of 10 ESRD patients and 10 age- and CMV-serostatus-matched healthy individuals (HI). The Gini-index, a parameter used in economics to describe the distribution of income, was calculated to determine the extent of skewing at the subset level taking into account frequencies of all 24 TCR Vβ-families. In addition, using HI as reference population, the differential impact of ESRD was assessed on clonal expansion at the level of an individual TCR Vβ-family. CD8+, but not CD4+, T cell differentiation was

In vitro pharmacokinetics of anti-psoriatic fumaric acid esters

Background: Psoriasis is a chronic inflammatory skin disease that can be successfully treated with a mixture of fumaric acid esters (FAE) formulated as enteric-coated tablets for oral use. These tablets consist of dimethylfumarate (DMF) and salts of monoethylfumarate (MEF) and its main bioactive metabolite is monomethylfumarate (MMF). Little is known about the pharmacokinetics of these FAE. The aim of the present study was to investigate the hydrolysis of DMF to MMF and the stability of MMF, DMF and MEF at in vitro conditions representing different body compartments. Results: DMF is hydrolyzed to MMF in an alkaline environment (pH 8), but not in an acidic environment (pH 1). In these conditions MMF and MEF remained intact during the period of analysis (6 h). Interestingly, DMF was hardly hydrolyzed to MMF in a buffer of pH 7.4, but was rapidly hydrolyzed in human serum having the same pH. Moreover, in whole blood the half-life of DMF was dramatically reduced as compared to serum. The concentrations of MMF and MEF in serum and whole blood decreased with increasing time. These data indicate that the majority of the FAE in the circulation are metabolized by one or more types of blood cells. Additional experiments with purified blood cell fractions resuspended in phosphate buffered saline (pH 7.4) revealed that at concentrations present in whole blood monocytes/lymphocytes, but not granulocytes and erythrocytes, effectively hydrolyzed DMF to MMF. Furthermore, in agreement with the data obtained with the pure components of the tablet, the enteric-coated tablet remained intact at pH 1, but rapidly dissolved at pH 8. Conclusion: Together, these in vitro data indicate that hydrolysis of DMF to MMF rapidly occurs at pH 8, resembling that within the small intestines, but not at pH 1 resembling the pH in the stomach. At both pHs MMF and MEF remained intact. These data explain the observation that after oral FAE intake MMF and MEF, but not DMF, can be readily detected in the circulation of human healthy volunteers and psoriasis patients

End stage renal disease patients have a skewed T cell receptor Vβ repertoire

Background: End stage renal disease (ESRD) is associated with defective T-cell mediated immunity. A diverse T-cell receptor (TCR) Vβ repertoire is central to effective T-cell mediated immune responses to foreign antigens. In this study, the effect of ESRD on TCR Vβ repertoire was assessed. Results: A higher proportion of ESRD patients (68.9 %) had a skewed TCR Vβ repertoire compared to age and cytomegalovirus (CMV) - IgG serostatus matched healthy individuals (31.4 %, P < 0.001). Age, CMV serostatus and ESRD were independently associated with an increase in shifting of the TCR Vβ repertoire. More differentiated CD8+ T cells were observed in young ESRD patients with a shifted TCR Vβ repertoire. CD31-expressing naive T cells and relative telomere length of T cells were not significantly related to TCR Vβ skewing. Conclusions: ESRD significantly skewed the TCR Vβ repertoire particularly in the elderly population, which may contribute to the uremia-associated defect in T-cell mediated immunity

Cytomegalovirus contributes partly to uraemia-associated premature immunological ageing of the T cell compartment

Cytomegalovirus (CMV) infection has been implicated in accelerated T cell ageing. End-stage renal disease (ESRD) patients have a severely immunologically aged T cell compartment but also a high prevalence of CMV infection. We investigated whether CMV infection contributes to T cell ageing in ESRD patients. We determined the thymic output by the T cell receptor excision circle (TREC) content and percentage of CD31+ naïve T cells. The proliferative history of the T cell compartment by determination of the relative telomere length (RTL) and the T cell differentiation status was determined by immunophenotyping. It appeared that CMV infection did not affect thymic output but reduced RTL of CD8+ T cells in ESRD patients. Moreover, increased T cell differentiation was observed with higher percentages of CD57+ and CD28null CD4+ and CD8+ memory T cells. These CD28null T cells had significantly shorter telomeres compared to CD28+ T cells. Therefore we concluded that CMV infection does not affect the decreased thymic output but increases T cell differentiation as observed in ESRD-related premature T cell ageing

A very low thymus function identifies patients with substantial increased risk for long-term mortality after kidney transplantation

Background: End-stage renal disease is associated with premature ageing of the T cell immune system but inter-individual variation is substantial. The hypothesis was tested that advanced immunological T cell ageing assessed by peripheral T cell differentiation increases the long-term mortality risk after renal transplantation. Results: Circulating T cells of 211 recipients of a kidney from a living donor were analyzed before and in the first year after transplantation. The number of CD31-positive naive T cells (as a marker for recent thymic emigrants) and the differentiation status of the memory T cells was assessed. Thirty recipients died during follow-up of at least 5 years. Absolute numbers of naive CD4+ (living:258 cells/μl vs. deceased:101 cells/μl, p < 0.001) and naive CD8+ T cells (living:97 cells/μl vs. deceased:37 cells/μl, p < 0.001) were significantly lower in the deceased group prior to transplantation. In a multivariate proportional hazard analysis the number of naive CD4+ T cells remained associated with all-cause mortality (HR 0.98, CI 0.98-0.99, p < 0.001). The low number of naive T cells in the deceased patient group was primarily caused by a decrease in recent thymic emigrants (i.e. less CD31+ naive T cells) indicating a lowered thymus function. In addition, the physiological age-related compensatory increase in CD31- naïve T cells was not observed. Within the first year after transp

Belatacept does not inhibit follicular T cell-dependent B-cell differentiation in kidney transplantation

Humoral alloreactivity has been recognized as a common cause of kidney transplant dysfunction. B-cell activation, differentiation, and antibody production are dependent on IL-21+CXCR5+ follicular T-helper (Tfh) cells. Here, we studied whether belatacept, an inhibitor of the costimulatory CD28-CD80/86-pathway, interrupts the crosstalk between Tfh- and B-cells more efficiently than the calcineurin inhibitor tacrolimus. The suppressive effects of belatacept and tacrolimus on donor antigen-driven Tfh-B-cell interaction were functionally studied in peripheral blood mononuclear cells from 40 kidney transplant patients randomized to a belatacept- or tacrolimus-based immunosuppressive regimen. No significant differences in uncultured cells or donor antigen-stimulated cells were found between belatacept- and tacrolimus-treated patients in the CXCR5+Tfh cell generation and activation (upregulation of PD-1). Belatacept and tacrolimus in vitro minimally inhibited Tfh-cell generation (by ~6-7%) and partially prevented Tfh-cell activation (by ~30-50%). The proportion of IL-21+-activated Tfh-cells was partially decreased by in vitro addition of belatacept or tacrolimus (by ~60%). Baseline expressions and proportions of activated CD86+ B-cells, plasmablasts, and transitional B-cells after donor antigen stimulation did not differ between belatacept- and tacrolimus-treated patients. Donor antigen-drive

Increased CD16 expression on NK cells is indicative of antibody-dependent cell-mediated cytotoxicity in chronic-active antibody-mediated rejection

Chronic-active antibody mediated rejection (c-aABMR) contributes significantly to late renal allograft failure. The antibodies directed against donor-derived antigens, e.g. anti-HLA antibodies, cause inflammation at the level of the microvascular endothelium. This is characterized by signs of local activation of the complement system and accumulation of immune cells within the capillaries. Non-invasive biomarkers of c-aABMR are currently not available but could be valuable for early detection. We therefore analyzed the activation profiles of circulating T and B cells, NK cells and monocytes in the peripheral blood of 25 kidney transplant recipients with c-aABMR and compared them to 25 matched recipients to evaluate whether they could serve as a potential biomarker. No significant differences were found in the total percentage and distribution of NK cells, B cells and T cells between the c-aABMRpos and c-aABMRneg cases. There was however a higher percentage of monocytes present in c-aABMRpos cases (p < .05). Additionally, differences were found in activation status of circulating monocytes, NK cells and γδ T cells, mainly concerning the activation marker CD16. Although statistically significant, these differences were not sufficient for use as a biomarker of c-aABMR

Cytomegalovirus contributes partly to uraemia-associated premature immunological ageing of the T cell compartment

Cytomegalovirus (CMV) infection has been implicated in accelerated T cell ageing. End-stage renal disease (ESRD) patients have a severely immunologically aged T cell compartment but also a high prevalence of CMV infection. We investigated whether CMV infection contributes to T cell ageing in ESRD patients. We determined the thymic output by the T cell receptor excision circle (TREC) content and percentage of CD31+ naive T cells. The proliferative history of the T cell compartment by determination of the relative telomere length (RTL) and the T cell differentiation status was determined by immunophenotyping. It appeared that CMV infection did not affect thymic output but reduced RTL of CD8+ T cells in ESRD patients. Moreover, increased T cell differentiation was observed with higher percentages of CD57+ and CD28null CD4+ and CD8+ memory T cells. These CD28null T cells had significantly shorter telomeres compared to CD28+ T cells. Therefore we concluded that CMV infection does not affect the decreased thymic output but increases T cell differentiation as observed in ESRD-related premature T cell ageing