Publications by authors named "Frans H Claas"

294 Publications

Editorial: "The Role of Immune Checkpoint Molecules in Solid and Hematopoietic Stem Cell Transplantation".

Front Immunol 2021 20;12:822558. Epub 2021 Dec 20.

Institute for Transfusion Medicine, University Hospital Essen, Essen, Germany.

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http://dx.doi.org/10.3389/fimmu.2021.822558DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8720776PMC
December 2021

Implementation of molecular matching in transplantation requires further characterization of both immunogenicity and antigenicity of individual HLA epitopes.

Hum Immunol 2021 Dec 25. Epub 2021 Dec 25.

Department of Immunology, Leiden University Medical Center, Leiden, The Netherlands; Eurotransplant Reference Laboratory, Leiden, The Netherlands. Electronic address:

Over the past decade, high HLA epitope mismatch scores have been associated with inferior transplant outcomes using several tools, of which HLAMatchmaker is most well-known. This software uses theoretically defined polymorphic amino acid configurations, called eplets, for HLA compatibility analysis. Although consideration of eplet mismatch loads has potential for immunological risk stratification of transplant patients, the use of eplet matching in organ allocation algorithms is hindered by lacking knowledge of the immunogenicity of individual eplets, and the possibility that single mismatched amino acids, rather than complete eplets, are responsible for HLA antibody induction. There are several approaches to define eplet immunogenicity, such as antibody verification of individual eplets, and data-driven approaches using large datasets that correlate specific eplet mismatches to donor specific antibody formation or inferior transplant outcomes. Data-driven approaches can also be used to define whether single amino acid mismatches may be more informative than eplet mismatches for predicting HLA antibody induction. When using epitope knowledge for the assignment of unacceptable antigens, it important to realize that alleles sharing an eplet to which antibodies have formed are not automatically all unacceptable since multiple contact sites determine the binding strength and thus biological function and pathogenicity of an antibody, which may differ between reactive alleles. While the future looks bright for using HLA epitopes in clinical decision making, major steps need to be taken to make this a clinical reality.
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http://dx.doi.org/10.1016/j.humimm.2021.12.002DOI Listing
December 2021

Heterologous Immunity of Virus-Specific T Cells Leading to Alloreactivity: Possible Implications for Solid Organ Transplantation.

Viruses 2021 11 24;13(12). Epub 2021 Nov 24.

Department of Immunology, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands.

Exposure of the adaptive immune system to a pathogen can result in the activation and expansion of T cells capable of recognizing not only the specific antigen but also different unrelated antigens, a process which is commonly referred to as heterologous immunity. While such cross-reactivity is favourable in amplifying protective immune responses to pathogens, induction of T cell-mediated heterologous immune responses to allo-antigens in the setting of solid organ transplantation can potentially lead to allograft rejection. In this review, we provide an overview of murine and human studies investigating the incidence and functional properties of virus-specific memory T cells cross-reacting with allo-antigens and discuss their potential relevance in the context of solid organ transplantation.
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http://dx.doi.org/10.3390/v13122359DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8706157PMC
November 2021

T-Cell Epitopes Shared Between Immunizing HLA and Donor HLA Associate With Graft Failure After Kidney Transplantation.

Front Immunol 2021 18;12:784040. Epub 2021 Nov 18.

Renal Transplant Unit, Department of Internal Medicine, Amsterdam University Medical Center, Amsterdam, Netherlands.

CD4 T-helper cells play an important role in alloimmune reactions following transplantation by stimulating humoral as well as cellular responses, which might lead to failure of the allograft. CD4 memory T-helper cells from a previous immunizing event can potentially be reactivated by exposure to HLA mismatches that share T-cell epitopes with the initial immunizing HLA. Consequently, reactivity of CD4 memory T-helper cells toward T-cell epitopes that are shared between immunizing HLA and donor HLA could increase the risk of alloimmunity following transplantation, thus affecting transplant outcome. In this study, the amount of T-cell epitopes shared between immunizing and donor HLA was used as a surrogate marker to evaluate the effect of donor-reactive CD4 memory T-helper cells on the 10-year risk of death-censored kidney graft failure in 190 donor/recipient combinations using the PIRCHE-II algorithm. The T-cell epitopes of the initial theoretical immunizing HLA and the donor HLA were estimated and the number of shared PIRCHE-II epitopes was calculated. We show that the natural logarithm-transformed PIRCHE-II overlap score, or Shared T-cell EPitopes (STEP) score, significantly associates with the 10-year risk of death-censored kidney graft failure, suggesting that the presence of pre-transplant donor-reactive CD4 memory T-helper cells might be a strong indicator for the risk of graft failure following kidney transplantation.
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http://dx.doi.org/10.3389/fimmu.2021.784040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8637278PMC
November 2021

Precision Engineering of an Anti-HLA-A2 Chimeric Antigen Receptor in Regulatory T Cells for Transplant Immune Tolerance.

Front Immunol 2021 20;12:686439. Epub 2021 Sep 20.

Department of Surgery, University of California, San Francisco, San Francisco, CA, United States.

Infusion of regulatory T cells (Tregs) engineered with a chimeric antigen receptor (CAR) targeting donor-derived human leukocyte antigen (HLA) is a promising strategy to promote transplant tolerance. Here, we describe an anti-HLA-A2 CAR (A2-CAR) generated by grafting the complementarity-determining regions (CDRs) of a human monoclonal anti-HLA-A2 antibody into the framework regions of the Herceptin 4D5 single-chain variable fragment and fusing it with a CD28-ζ signaling domain. The CDR-grafted A2-CAR maintained the specificity of the original antibody. We then generated HLA-A2 mono-specific human CAR Tregs either by deleting the endogenous T-cell receptor (TCR) CRISPR/Cas9 and introducing the A2-CAR using lentiviral transduction or by directly integrating the CAR construct into the TCR alpha constant locus using homology-directed repair. These A2-CARTCR human Tregs maintained both Treg phenotype and function . Moreover, they selectively accumulated in HLA-A2-expressing islets transplanted from either HLA-A2 transgenic mice or deceased human donors. A2-CARTCR Tregs did not impair the function of these HLA-A2 islets, whereas similarly engineered A2-CARTCRCD4 conventional T cells rejected the islets in less than 2 weeks. A2-CARTCR Tregs delayed graft--host disease only in the presence of HLA-A2, expressed either by co-transferred peripheral blood mononuclear cells or by the recipient mice. Altogether, we demonstrate that genome-engineered mono-antigen-specific A2-CAR Tregs localize to HLA-A2-expressing grafts and exhibit antigen-dependent suppression, independent of TCR expression. These approaches may be applied towards developing precision Treg cell therapies for transplant tolerance.
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http://dx.doi.org/10.3389/fimmu.2021.686439DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8488356PMC
October 2021

Highly Sensitized Patients Are Well Served by Receiving a Compatible Organ Offer Based on Acceptable Mismatches.

Front Immunol 2021 25;12:687254. Epub 2021 Jun 25.

Eurotransplant Reference Laboratory, Leiden University Medical Center, Leiden, Netherlands.

Highly sensitized kidney patients accrue on the transplant waiting list due to their broad immunization against non-self Human Leucocyte Antigens (HLA). Although challenging, the best option for highly sensitized patients is transplantation with a crossmatch negative donor without any additional therapeutic intervention. The Eurotransplant Acceptable Mismatch (AM) program was initiated more than 30 years ago with the intention to increase the chance for highly sensitized patients to be transplanted with such a compatible donor. The AM program allows for enhanced transplantation to this difficult to transplant patient group by allocating deceased donor kidneys on the basis of a match with the recipient's own HLA antigens in combination with predefined acceptable antigens. Acceptable antigens are those HLA antigens towards which the patients has never formed antibodies, as determined by extensive laboratory testing. By using this extended HLA phenotype for allocation and giving priority whenever a compatible donor organ becomes available, organ offers are made for roughly 80% of patients in this program. Up till now, more than 1700 highly sensitized patients have been transplanted through the AM program. Recent studies have shown that the concept of acceptable mismatches being truly immunologically acceptable holds true for both rejection rates and long-term graft survival. Patients that were transplanted through the AM program had a similar rejection incidence and long-term graft survival rates identical to non-sensitized patients transplanted through regular allocation. However, a subset of patients included in the AM program does not receive an organ offer within a reasonable time frame. As these are often patients with a rare HLA phenotype in comparison to the Eurotransplant donor population, extension of the donor pool for these specific patients through further European collaboration would significantly increase their chances of being transplanted. For those patients that will not benefit from such strategy, desensitization is the ultimate solution.
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http://dx.doi.org/10.3389/fimmu.2021.687254DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8267476PMC
October 2021

Significance of HLA-DQ in kidney transplantation: time to reevaluate human leukocyte antigen-matching priorities to improve transplant outcomes? An expert review and recommendations.

Kidney Int 2021 11 8;100(5):1012-1022. Epub 2021 Jul 8.

Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium.

The weight of human leukocyte antigen (HLA) matching in kidney allocation algorithms, especially in the United States, has been devalued in a stepwise manner, supported by the introduction of modern immunosuppression. The intent was further to reduce the observed ethnic/racial disparity, as data emerged associating HLA matching with decreased access to transplantation for African American patients. In recent years, it has been increasingly recognized that a leading cause of graft loss is chronic antibody-mediated rejection, attributed to the development of de novo antibodies against mismatched donor HLA expressed on the graft. These antibodies are most frequently against donor HLA-DQ molecules. Beyond their impact on graft survival, generation of de novo donor-specific HLA antibodies also leads to increased sensitization, as measured by panel-reactive antibody metrics. Consequently, access to transplantation for patients returning to the waitlist in need of a second transplant is compromised. Herein, we address the implications of reduced HLA matching policies in kidney allocation. We highlight the observed diminished outcome data, the significant financial burden, the long-term health consequences, and, more important, the unintended consequences. We further provide recommendations to examine the impact of donor-recipient HLA class II and specifically HLA-DQαβ mismatching, focusing on collection of appropriate data, application of creative simulation approaches, and reconsideration of best practices to reduce inequalities while optimizing patient outcomes.
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http://dx.doi.org/10.1016/j.kint.2021.06.026DOI Listing
November 2021

Comparison of different luminex single antigen bead kits for memory B cell-derived HLA antibody detection.

HLA 2021 09 16;98(3):200-206. Epub 2021 Jul 16.

Department of Immunology, Leiden University Medical Center, Leiden, The Netherlands.

Detection of HLA-specific memory B cells can provide additional information on sensitization of alloantigen-exposed individuals and refine immunological risk assessment. We have recently developed an assay enabling profiling of memory B cell-derived HLA antibodies using luminex single antigen bead (SAB) assay. Here, we compared the performance of the SAB kits from two vendors for memory B cell-derived HLA antibody detection. IgG was isolated from culture supernatants of polyclonally activated B cells from alloantigen-exposed (n = 7) or nonexposed (n = 5) individuals, using our previously established method. Eluates containing isolated IgG from culture supernatants were tested for the presence of HLA antibodies using luminex SAB analysis from both One Lambda and Lifecodes (Immucor). In contrast to Lifecodes, high mean fluorescence intensity (MFI) signals were found for negative control beads in One Lambda (median MFI for class I:1730 and for class II:728), accompanied by high MFI values for self HLA-coated beads, especially for HLA-C. Despite high background in the One Lambda assays, 91% concordance for HLA class I and 85% concordance for HLA class II were found between the specificities detected using SAB kits from the two vendors. Our results show that HLA-specific memory B cells can be profiled using kits from both vendors. However, when analyzing One Lambda results one should be aware of the restrictions related to nonspecific binding particularly in HLA-C-coated beads, and pay attention to self HLA-coated beads in order to accurately identify the reactivities leading to the definition of the actual HLA antibody specificities.
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http://dx.doi.org/10.1111/tan.14356DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8456970PMC
September 2021

A Combined microRNA and Chemokine Profile in Urine to Identify Rejection After Kidney Transplantation.

Transplant Direct 2021 Jul 10;7(7):e711. Epub 2021 Jun 10.

Department of Immunology, Leiden University Medical Center, Leiden, The Netherlands.

There is an unmet need for noninvasive tools for diagnosis of rejection after kidney transplantation. The aim of this study was to determine the discriminative value of a combined cellular and molecular biomarker platform in urine for the detection of rejection.

Methods: First, microRNA (miR) molecules were screened in transplant biopsies and urine sediments of patients with acute rejection and patients without rejection and stable graft function. Second, the expression of 15 selected miRs was quantified in an independent set of 115 urine sediments of patients with rejection and 55 urine sediments of patients without histological signs of rejection on protocol biopsy. Additionally, CXCL-9 and CXCL-10 protein levels were quantified in the urine supernatant.

Results: Levels of miR-155-5p (5.7-fold), miR-126-3p (4.2-fold), miR-21-5p (3.7-fold), miR-25-3p (2.5-fold), and miR-615-3p (0.4-fold) were significantly different between rejection and no-rejection urine sediments. CXCL-9 and CXCL-10 levels were significantly elevated in urine from recipients with rejection. In a multivariable model (sensitivity: 89.1%, specificity: 75.6%, area under the curve: 0.94, < 0.001), miR-155-5p, miR-615-3p, and CXCL-9 levels were independent predictors of rejection. Stratified 10-fold cross validation of the model resulted in an area under the curve of 0.92.

Conclusions: A combined urinary microRNA and chemokine profile discriminates kidney transplant rejection from stable graft conditions.
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http://dx.doi.org/10.1097/TXD.0000000000001169DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8196093PMC
July 2021

Maternal-Fetal HLA Compatibility in Uncomplicated and Preeclamptic Naturally Conceived Pregnancies.

Front Immunol 2021 13;12:673131. Epub 2021 May 13.

Department of Obstetrics and Gynaecology, Leiden University Medical Center, Leiden, Netherlands.

Introduction: In pregnancy, the mother and fetus differ in HLA antigens, and yet the maternal immune system generally tolerates the fetus. KIR receptors expressed by maternal uterine NK cells at the maternal-fetal interface directly interact with HLA-C on extravillous trophoblast cells for optimal placental development. In this study, we aimed to determine whether there is a preferential selection for HLA compatibility and specific KIR/HLA-C combinations in uncomplicated and preeclamptic naturally conceived pregnancies compared to what would be expected by chance.

Methods: Genotyping for maternal and fetal HLA-A, -B, -C, -DR, and -DQ, and maternal KIR was performed for 451 uncomplicated pregnancies and 77 pregnancies complicated with preeclampsia. The number of HLA antigen (mis)matches between mother and fetus was calculated and compared to expected values obtained by randomization of the HLA haplotype, inherited from the father, over the existing maternal haplotype of the fetuses. A similar methodology was executed for analysis of the KIR/HLA-C data (n=309).

Results: In uncomplicated pregnancies, the degree of maternal-fetal HLA matching was not different than expected-by-chance values. In preeclamptic pregnancies, the degree of maternal-fetal HLA matching was different in observed compared to expected-by-chance values (p=0.012). More specifically, the degree of maternal-fetal matching of HLA-C was higher in the actual preeclamptic pregnancies than was expected-by-chance (p=0.007). Preeclamptic pregnancies showed an overall tendency towards higher maternal-fetal HLA compatibility, for total HLA matches (p=0.021), HLA class I (p=0.038) and HLA-C (p=0.025) compared to uncomplicated pregnancies.

Conclusion: The data suggest that there is no preferential selection of maternal-fetal HLA compatibility in uncomplicated pregnancies. In contrast, increased total HLA, HLA class I and, especially, HLA-C compatibility is associated with preeclampsia, suggestive for a role of HLA mismatches in immune regulation leading to uncomplicated pregnancy.
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http://dx.doi.org/10.3389/fimmu.2021.673131DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8155594PMC
October 2021

Single antigen testing to reduce early antibody-mediated rejection risk in female recipients of a spousal donor kidney.

Transpl Immunol 2021 08 8;67:101407. Epub 2021 May 8.

Department of Internal Medicine (Nephrology), Leiden University Medical Center, the Netherlands; Department of Internal Medicine, Haga Teaching Hospital, The Hague, the Netherlands.

Female recipients of a spousal donor kidney transplant are at greater risk of donor-specific pre-immunization, which may increase the risk of acute antibody-mediated rejection (ABMR). We assessed the incidence of early ABMR (within two weeks after transplantation), risk factors for ABMR and graft function in 352 complement-dependent cytotoxicity test-negative LURD transplant recipients, transplanted between 1997 and 2014 at the Leiden University Medical Center in The Netherlands. Risk factors for immunization were retrieved from the health records. As methods to screen for preformed donor-specific antibodies (pDSA) have developed through time, we retrospectively screened those with ABMR for pDSA using pooled-antigen bead (PAB) and single-antigen bead (SAB) assays. The cumulative incidence of rejection in the first six months after transplantation was 18% (TCMR 15%; early ABMR 3%). Early ABMR resulted in inferior graft survival and was more common in women who received a kidney from their spouse (10%) than in other women (2%) and men (<1%). The SAB assay retrospectively identified pDSA in seven of nine cases of early ABMR (78%), while the PAB detected pDSA in only three cases (33%). Seeing that early ABMR occurred in 10% of women who received a kidney from their spouse, a SAB assay should be included in the pre-transplant assessment of this group of women, regardless of the result of the PAB assay.
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http://dx.doi.org/10.1016/j.trim.2021.101407DOI Listing
August 2021

ERAP2 Increases the Abundance of a Peptide Submotif Highly Selective for the Birdshot Uveitis-Associated HLA-A29.

Front Immunol 2021 25;12:634441. Epub 2021 Feb 25.

Department of Ophthalmology, University Medical Center Utrecht, University of Utrecht, Utrecht, Netherlands.

Birdshot Uveitis (BU) is a blinding inflammatory eye condition that only affects HLA-A29-positive individuals. Genetic association studies linked with BU, an aminopeptidase which trims peptides before their presentation by HLA class I at the cell surface, which suggests that ERAP2-dependent peptide presentation by HLA-A29 drives the pathogenesis of BU. However, it remains poorly understood whether the effects of ERAP2 on the HLA-A29 peptidome are distinct from its effect on other HLA allotypes. To address this, we focused on the effects of ERAP2 on the immunopeptidome in patient-derived antigen presenting cells. Using complementary HLA-A29-based and pan-class I immunopurifications, isotope-labeled naturally processed and presented HLA-bound peptides were sequenced by mass spectrometry. We show that the effects of ERAP2 on the N-terminus of ligands of HLA-A29 are shared across endogenous HLA allotypes, but discover and replicate that one peptide motif generated in the presence of ERAP2 is specifically bound by HLA-A29. This motif can be found in the amino acid sequence of putative autoantigens. We further show evidence for internal sequence specificity for ERAP2 imprinted in the immunopeptidome. These results reveal that ERAP2 can generate an HLA-A29-specific antigen repertoire, which supports that antigen presentation is a key disease pathway in BU.
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http://dx.doi.org/10.3389/fimmu.2021.634441DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7950316PMC
September 2021

Two Human Monoclonal HLA-Reactive Antibodies Cross-React with Mamu-B*008, a Rhesus Macaque MHC Allotype Associated with Control of Simian Immunodeficiency Virus Replication.

J Immunol 2021 04 10;206(8):1957-1965. Epub 2021 Mar 10.

Department of Comparative Genetics and Refinement, Biomedical Primate Research Centre, 2288 GJ Rijswijk, the Netherlands.

MHC class I molecules play an important role in adaptive immune responses against intracellular pathogens. These molecules are highly polymorphic, and many allotypes have been characterized. In a transplantation setting, a mismatch between MHC allotypes may initiate an alloimmune response. Rhesus macaques (, ) are valuable as a preclinical model species in transplantation research as well as to evaluate the safety and efficacy of vaccine candidates. In both lines of research, the availability of nonhuman primate MHC-reactive mAbs may enable in vitro monitoring and detection of presence of particular Mamu molecules. In this study, we screened a collection of thoroughly characterized HLA class I-specific human mAbs for cross-reactivity with rhesus macaque MHC class I allotypes. Two mAbs, OK4F9 and OK4F10, recognize an epitope that is defined by isoleucine (I) at amino acid position 142 that is present on the Indian rhesus macaque Mamu-B*008:01 allotype, which is an allotype known to be associated with elite control of SIV replication. The reactive pattern of a third mAb, MUS4H4, is more complex and includes an epitope shared on Mamu-A2*05:01 and -B*001:01-encoded Ags. This is the first description, to our knowledge, of human HLA-reactive mAbs that can recognize Mamu allotypes, and these can be useful tools for in vitro monitoring the presence of the relevant allelic products. Moreover, OK4F9 and OK4F10 can be powerful mAbs for application in SIV-related research.
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http://dx.doi.org/10.4049/jimmunol.2001405DOI Listing
April 2021

A possible role for HLA-G in development of uteroplacental acute atherosis in preeclampsia.

J Reprod Immunol 2021 04 2;144:103284. Epub 2021 Feb 2.

Institute for Clinical Medicine, Faculty of Medicine, University of Oslo, Norway; Division of Obstetrics and Gyneacology, Oslo University Hospital, Norway.

HLA-G, a non-classical HLA molecule expressed by extravillous trophoblasts, plays a role in the maternal immune tolerance towards fetal cells. HLA-G expression is regulated by genetic polymorphisms in the 3' untranslated region (3'UTR). Low levels of HLA-G in the maternal circulation and placental tissue are linked to preeclampsia. Our objective was to investigate whether variants of the 3'UTR of the HLA-G gene in mother and fetus are associated with acute atherosis, a pregnancy specific arterial lesion of the decidua basalis that is prevalent in preeclampsia. Paired maternal and fetal DNA samples from 83 normotensive and 83 preeclamptic pregnancies were analyzed. We sequenced the part of the HLA-G 3'UTR containing a 14-bp insertion/deletion region and seven single nucleotide polymorphisms (SNPs). Associations with acute atherosis were tested by logistic regression. The frequency of heterozygosity for the 14-bp polymorphism (Ins/Del) and the +3142 SNP (C/G) variant in the fetus are associated with acute atherosis in preeclampsia (66.7 % vs. 39.6 %, p = 0.039, and 69.0 % vs. 43.4 %, p = 0.024). Furthermore, the fetal UTR-3 haplotype, which encompasses the 14-bp deletion and the +3142G variant, is associated with acute atherosis in preeclampsia (15 % vs. 3.8 %, p = 0.016). In conclusion, HLA-G polymorphisms in the fetus are associated with acute atherosis. We hypothesize that these polymorphisms lead to altered HLA-G expression in the decidua basalis, affecting local feto-maternal immune tolerance and development of acute atherosis.
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http://dx.doi.org/10.1016/j.jri.2021.103284DOI Listing
April 2021

Autologous bone marrow-derived mesenchymal stromal cell therapy with early tacrolimus withdrawal: The randomized prospective, single-center, open-label TRITON study.

Am J Transplant 2021 09 18;21(9):3055-3065. Epub 2021 Mar 18.

Department of Internal Medicine (Nephrology) and Transplant Center, Leiden University Medical Center, Leiden, the Netherlands.

After renal transplantation, there is a need for immunosuppressive regimens which effectively prevent allograft rejection, while preserving renal function and minimizing side effects. From this perspective, mesenchymal stromal cell (MSC) therapy is of interest. In this randomized prospective, single-center, open-label trial, we compared MSCs infused 6 and 7 weeks after renal transplantation and early tacrolimus withdrawal with a control tacrolimus group. Primary end point was quantitative evaluation of interstitial fibrosis in protocol biopsies at 4 and 24 weeks posttransplant. Secondary end points included acute rejection, graft loss, death, renal function, adverse events, and immunological responses. Seventy patients were randomly assigned of which 57 patients were included in the final analysis (29 MSC; 28 controls). Quantitative progression of fibrosis failed to show benefit in the MSC group and GFR remained stable in both groups. One acute rejection was documented (MSC group), while subclinical rejection in week 24 protocol biopsies occurred in seven patients (four MSC; three controls). In the MSC group, regulatory T cell numbers were significantly higher compared to controls (p = .014, week 24). In conclusion, early tacrolimus withdrawal with MSC therapy was safe and feasible without increased rejection and with preserved renal function. MSC therapy is a potentially useful approach after renal transplantation.
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http://dx.doi.org/10.1111/ajt.16528DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8518640PMC
September 2021

A Europe wide acceptable mismatch program will enable transplantation of long waiting highly sensitised patients with a compatible donor.

Transpl Immunol 2021 02 1;64:101354. Epub 2020 Dec 1.

Eurotransplant Reference Laboratory, Leiden University Medical Centre, Leiden, the Netherlands. Electronic address:

Immunisation against Human Leucocyte Antigens (HLA) can be caused by pregnancy, blood transfusion, or organ transplants. The HLA antibody status of a given patient significantly influences their access and waiting time to transplant. For some highly sensitised patients (HSP) there is hardly any suitable donor available in the deceased donor pool of their allocation organisation and therefore they wait a very long time before being offered a kidney for transplant. Especially patients with rare HLA phenotypes in relation to the actual donor pool are waiting extremely long. As HLA phenotypes are different in the various European populations, we hypothesized that extension of the donor pool outside the respective allocation system will increase the chance of receiving a compatible transplant for this subgroup of highly sensitised patients. One of the objectives of the EUROSTAM project, (a Europe-wide Strategy to enhance Transplantation of highly sensitised patients on the basis of Acceptable HLA Mismatches) was to develop a tool to compare the chance of transplanting HSP in different European populations with donor organs from within and outside their own donor pool. Information on the HLA type and ABO blood group of the actual donor population, as well as the acceptable mismatches of long waiting HSP were obtained from the EUROSTAM partner organizations i.e. Eurotransplant (ET), UK National Health Service Blood and Transplant (NHSBT), Barcelona, Prague and Athens. Results from simulations using the newly developed tool shows that 195 (27%) of the 724 long waiting highly sensitised patients registered at each partner organisation have increased chances of transplant in a different European donor pool. This makes a strong case for sharing kidneys between European countries for selected difficult to transplant patients.
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http://dx.doi.org/10.1016/j.trim.2020.101354DOI Listing
February 2021

PAKC: A novel panel of HLA class I antigen presentation machinery knockout cells from the same genetic origin.

Eur J Immunol 2021 03 1;51(3):734-737. Epub 2021 Feb 1.

Department of Immunopathology, Sanquin Research, Amsterdam, The Netherlands.

A single model system for integrative studies on multiple facets of antigen presentation is lacking. PAKC is a novel panel of ten cell lines knocked out for individual components of the HLA class I antigen presentation pathway. PAKC will accelerate HLA-I research in the fields of oncology, infectiology, and autoimmunity.
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http://dx.doi.org/10.1002/eji.202048599DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7986913PMC
March 2021

The SPPL3-Defined Glycosphingolipid Repertoire Orchestrates HLA Class I-Mediated Immune Responses.

Immunity 2021 01 2;54(1):132-150.e9. Epub 2020 Dec 2.

Department of Immunopathology, Sanquin Research, Amsterdam, the Netherlands; Landsteiner Laboratory, Amsterdam UMC, University of Amsterdam, Amsterdam, the Netherlands; Cancer Center Amsterdam, Amsterdam, the Netherlands. Electronic address:

HLA class I (HLA-I) glycoproteins drive immune responses by presenting antigens to cognate CD8 T cells. This process is often hijacked by tumors and pathogens for immune evasion. Because options for restoring HLA-I antigen presentation are limited, we aimed to identify druggable HLA-I pathway targets. Using iterative genome-wide screens, we uncovered that the cell surface glycosphingolipid (GSL) repertoire determines effective HLA-I antigen presentation. We show that absence of the protease SPPL3 augmented B3GNT5 enzyme activity, resulting in upregulation of surface neolacto-series GSLs. These GSLs sterically impeded antibody and receptor interactions with HLA-I and diminished CD8 T cell activation. Furthermore, a disturbed SPPL3-B3GNT5 pathway in glioma correlated with decreased patient survival. We show that the immunomodulatory effect could be reversed through GSL synthesis inhibition using clinically approved drugs. Overall, our study identifies a GSL signature that inhibits immune recognition and represents a potential therapeutic target in cancer, infection, and autoimmunity.
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http://dx.doi.org/10.1016/j.immuni.2020.11.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8722104PMC
January 2021

Low incidence of IgA isotype of HLA antibodies in alloantigen exposed individuals.

HLA 2021 02 2;97(2):101-111. Epub 2020 Dec 2.

Department of Immunology, Leiden University Medical Center, Leiden, The Netherlands.

Human leukocyte antigen (HLA) antibodies are induced by pregnancy, transfusion, or transplantation. Serum from transplant recipients is regularly screened for IgG HLA antibodies because of their clinical relevance for transplant outcome. While other isotypes of HLA antibodies, such as IgA may also contribute to the alloimmune response, validated detection assays for IgA HLA antibody detection are lacking. Therefore, we modified the commonly used luminex screening assay for IgG HLA antibody detection (IgG-LMX) into an IgA HLA antibody screening assay (IgA-LMX). Optimization and validation was performed with IgG, IgA1, and IgA2 isotype variants of HLA-specific human recombinant monoclonal antibodies (mAbs). Reactivity patterns of IgA1 and IgA2 isotype HLA-specific mAbs in IgA-LMX were identical to those of the IgG isotype. Cross-reactivity with IgG and IgM antibodies and nonspecific binding to the beads were excluded. Further assay validation showed the absence of IgA HLA antibodies in serum from individuals without alloantigen exposure (n = 18). When the IgA-LMX assay was applied to sera from 289 individuals with known alloantigen exposure through pregnancy (n = 91) or kidney transplantation (n = 198), IgA HLA antibodies were detected in 3.5% of individuals; eight patients on the kidney retransplant waitlist and two women immunized through pregnancy. The majority (90%) of IgA HLA antibodies were directed against HLA class II and were always present in conjunction with IgG HLA antibodies. Results of this study show that this validated IgA-LMX method can serve as a screening assay for IgA HLA antibodies and that the incidence of IgA HLA antibodies in alloantigen exposed individuals is low.
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http://dx.doi.org/10.1111/tan.14146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7898292PMC
February 2021

Visualizing Dynamic Changes at the Maternal-Fetal Interface Throughout Human Pregnancy by Mass Cytometry.

Front Immunol 2020 26;11:571300. Epub 2020 Oct 26.

Department of Immunology, Leiden University Medical Center, Leiden, Netherlands.

During healthy pregnancy, a balanced microenvironment at the maternal-fetal interface with coordinated interaction between various immune cells is necessary to maintain immunological tolerance. While specific decidual immune cell subsets have been investigated, a system-wide unbiased approach is lacking. Here, mass cytometry was applied for data-driven, in-depth immune profiling of the total leukocyte population isolated from first, second, and third trimester decidua, as well as maternal peripheral blood at time of delivery. The maternal-fetal interface showed a unique composition of immune cells, different from peripheral blood, with significant differences between early and term pregnancy samples. Profiling revealed substantial heterogeneity in the decidual lymphoid and myeloid cell lineages that shape gestational-specific immune networks and putative differentiation trajectories over time during gestation. Uncovering the overall complexity at the maternal-fetal interface throughout pregnancy resulted in a human atlas that may serve as a foundation upon which comprehension of the immune microenvironment and alterations thereof in pregnancy complications can be built.
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http://dx.doi.org/10.3389/fimmu.2020.571300DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7649376PMC
May 2021

HLA-EMMA, a tool for molecular-level HLA matching after heart transplantation.

Transpl Int 2020 12 14;33(12):1821-1822. Epub 2020 Oct 14.

Division of Cardiac Surgery, Medical University of Vienna, Vienna, Austria.

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http://dx.doi.org/10.1111/tri.13755DOI Listing
December 2020

Got your mother in a whirl: The role of maternal T cells and myeloid cells in pregnancy.

HLA 2020 11 20;96(5):561-579. Epub 2020 Sep 20.

Department of Immunology, Leiden University Medical Center, Leiden, The Netherlands.

Appropriate development of the placenta is required for healthy pregnancy to occur. After implantation of the fertilized blastocyst, fetal trophoblasts invade the endometrium and myometrium of the mother's uterus to establish placentation. In this process, fetal trophoblasts encounter maternal immune cells. In this review, we focus on the role of maternal T cells and myeloid cells (macrophages, dendritic cells) in pregnancy and their interaction with trophoblasts. To retain immunologic tolerization, trophoblasts evade immune recognition by T cells and produce factors that modulate their phenotype and function. On top of that, the local environment at the maternal-fetal interface favors expansion of regulatory T cells. Macrophages and dendritic cells are essential in maintaining a healthy pregnancy. They produce soluble factors and act as antigen-presenting cells, thereby interacting with T cells. Herein, M2 macrophages, immature dendritic cells, CD4 Th2 cells, and regulatory T cells represent an axis that maintains a local immune tolerant environment. We consider outstanding issues concerning these cell types and their pathways, which need to be addressed in future investigations. Data from recent single-cell sequencing experiments of the placental bed, to study heterogeneity of maternal immune cells and to predict cell-cell interactions, are discussed. Novel ways for long-term culturing of primary trophoblasts allow for cell-cell interaction studies in a functional way. Future directions should include study of the functionality of currently known and newly identified decidual immune cell subsets in healthy and complicated pregnancies, and their interaction with and modulation by trophoblast cells.
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http://dx.doi.org/10.1111/tan.14055DOI Listing
November 2020

Pre-existing Alloreactive T and B Cells and Their Possible Relevance for Pre-transplant Risk Estimation in Kidney Transplant Recipients.

Front Med (Lausanne) 2020 21;7:340. Epub 2020 Jul 21.

Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, Netherlands.

In allogeneic transplantation, genetic disparities between patient and donor may lead to cellular and humoral immune responses mediated by both naïve and memory alloreactive cells of the adaptive immune system. This review will focus on alloreactive T and B cells with emphasis on the memory compartment, their role in relation to kidney rejection, and assays to detect these alloreactive cells. Finally, the potential additional value of utilizing donor-specific memory T and B cell assays supplementary to current routine pre-transplant risk assessment of kidney transplant recipients will be discussed.
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http://dx.doi.org/10.3389/fmed.2020.00340DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7385137PMC
July 2020

Regulatory T Cells in Pregnancy: It Is Not All About FoxP3.

Front Immunol 2020 23;11:1182. Epub 2020 Jun 23.

Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, Netherlands.

In pregnancy, the semi-allogeneic fetus needs to be tolerated by the mother's immune system. Regulatory T cells (Tregs) play a prominent role in this process. Novel technologies allow for in-depth phenotyping of previously unidentified immune cell subsets, which has resulted in the appreciation of a vast heterogeneity of Treg subsets. Similar to other immunological events, there appears to be great diversity within the Treg population during pregnancy, both at the maternal-fetal interface as in the peripheral blood. Different Treg subsets have distinct phenotypes and various ways of functioning. Furthermore, the frequency of individual Treg subsets varies throughout gestation and is altered in aberrant pregnancies. This suggests that distinct Treg subsets play a role at different time points of gestation and that their role in maintaining healthy pregnancy is crucial, as reflected for instance by their reduced frequency in women with recurrent pregnancy loss. Since pregnancy is essential for the existence of mankind, multiple immune regulatory mechanisms and cell types are likely at play to assure successful pregnancy. Therefore, it is important to understand the complete microenvironment of the decidua, preferably in the context of the whole immune cell repertoire of the pregnant woman. So far, most studies have focused on a single mechanism or cell type, which often is the FoxP3 positive regulatory T cell when studying immune regulation. In this review, we instead focus on the contribution of FoxP3 negative Treg subsets to the decidual microenvironment and their possible role in pregnancy complications. Their phenotype, function, and effect in pregnancy are discussed.
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http://dx.doi.org/10.3389/fimmu.2020.01182DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7324675PMC
April 2021

Optimization of microRNA Acquirement from Seminal Plasma and Identification of Diminished Seminal microRNA-34b as Indicator of Low Semen Concentration.

Int J Mol Sci 2020 Jun 8;21(11). Epub 2020 Jun 8.

Department of Immunohematology, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands.

About 10-15% of couples who want to conceive suffer from subfertility, while in 30% of these cases, a male factor plays a role. Levels of particular microRNAs in seminal plasma, including those involved in spermatogenesis, may serve as an indicative parameter for subfertility. We first optimized a protocol for acquiring microRNAs from seminal plasma. Next, using a test-validation strategy in a male cohort, we aimed to identify microRNAs of which the levels are related to semen motility and concentration. By qPCR, 742 microRNAs were profiled in three normozoospermic samples, three seminal samples with a low semen motility (asthenozoospermia), and three with a low semen concentration (oligozoospermia). MicroRNAs showing significant differences between groups were further validated in a second cohort consisting of 40 samples with normozoospermia (control group), 47 samples with asthenozoospermia, and 19 samples with oligozoospermia (of which 74% also low motility). Highest microRNA yields were obtained with the Biofluids RNA extraction kit, with inclusion of MS2 RNA carrier and proteinase K treatment to the protocol, and when 50 µL of seminal plasma was used as input. Exosome isolation prior to RNA extraction did not lead to enhanced yields. In the test cohort, 236 microRNAs could be detected, of which 54 microRNAs showed a difference between groups. Five microRNAs were analyzed in the validation cohort. MiR-34b-5p levels in the control group were significantly higher compared to the asthenozoospermia group ( < 0.05) and compared to the oligozoospermia group ( < 0.001). We optimized microRNA acquirement from seminal plasma and identified microRNA levels in relation to semen concentration and motility. As recent human and mouse studies show that the miR-34 family is a marker of low semen concentration and is crucial in spermatogenesis, seminal plasma miR-34b-5p may represent a suitable candidate to study further as a marker of male subfertility.
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http://dx.doi.org/10.3390/ijms21114089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7312420PMC
June 2020

Molecular-level HLA mismatch is associated with rejection and worsened graft survival in heart transplant recipients - a retrospective study.

Transpl Int 2020 09 23;33(9):1078-1088. Epub 2020 Jun 23.

Division of Cardiac Surgery, Medical University of Vienna, Vienna, Austria.

The aim was to evaluate the association of molecular-level human leukocyte antigen (HLA) mismatching with post-transplant graft survival, rejection, and cardiac allograft vasculopathy (CAV). We retrospectively analyzed all primary cardiac transplant recipients between 01/1984-06/2016. 1167 patients fulfilled inclusion criteria and had HLA typing information available. In 312 donor-recipient pairs, typing at serological split antigen level was available. We used the Epitope MisMatch Algorithm to calculate the number of amino acid differences in antibody-verified HLA eplets (amino acid mismatch load (AAMM)) between donor and recipient. Patients with a higher HLA-DR AAMM load had inferior 1-year graft survival (hazard ratio [HR], 1.14; 95% confidence interval [CI], 1.01-1.28). The HLA-AB AAMM load showed no impact on graft survival. In the subgroup with available split-level information, we observed an inferior graft survival for a higher HLA-DR AAMM load 3 months after transplantation (HR, 1.22; 95% CI, 1.04-1.44) and a higher risk for rejection for an increasing HLA-AB (HR, 1.70; 95% CI, 1.29-2.24) and HLA-DR (HR, 1.32; 95% CI, 1.09-1.61) AAMM load. No impact on the development of CAV was found. Molecular-level HLA mismatch analysis could serve as a tool for risk stratification after heart transplantation and might take us one step further into precision medicine.
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http://dx.doi.org/10.1111/tri.13657DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7540475PMC
September 2020

Generation and reactivity analysis of human recombinant monoclonal antibodies directed against epitopes on HLA-DR.

Am J Transplant 2020 12 15;20(12):3341-3353. Epub 2020 May 15.

Department of Immunohematology and Blood Transfusion, Leiden University Medical Centre, Leiden, The Netherlands.

In kidney transplantation, eplet mismatches between donor and recipient have been associated with de novo donor-specific antibody development. Eplets are theoretically defined configurations of polymorphic amino acids and require experimental verification to establish whether they can be bound by alloantibodies. Human HLA-specific monoclonal antibodies (mAbs) have been instrumental for this purpose but are largely lacking for HLA class II. In this study, we isolated single HLA-DR-specific memory B cells from peripheral blood of immunized individuals (n = 3) using HLA class II tetramers to generate recombinant human HLA-DR antigen-reactive mAbs (n = 5). Comparison of the amino acid composition of the reactive HLA alleles in relation to the antibody reactivity patterns led to identification of 3 configurations, 70Q 73A, 31F 32Y 37Y, and 14K 25Q recognized, respectively, by HLA-DRB1*01:01, HLA-DRB1*04:01, and HLA-DRB1*07:01 antigen-reactive mAbs. The first 2 correspond to eplets 70QA and 31FYY and can now be considered antibody verified. The latter indicates that eplet 25Q needs to be redefined before being considered as antibody verified. Generation and reactivity analysis of human HLA-DR mAbs allowed for identification of amino acid configurations corresponding to known eplets, whereas the other patterns may be used to redefine eplets with similar, but not identical predicted amino acid composition.
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http://dx.doi.org/10.1111/ajt.15950DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7754395PMC
December 2020

HLA-G whole gene amplification reveals linkage disequilibrium between the HLA-G 3'UTR and coding sequence.

HLA 2020 08 17;96(2):179-185. Epub 2020 May 17.

Department of Immunohematology, Leiden University Medical Center, Leiden, The Netherlands.

Polymorphic sites in the HLA-G gene may influence expression and function of the protein. Knowledge of the association between high-resolution HLA-G alleles and 3-prime untranslated (3'UTR) haplotypes is useful for studies on the role of HLA-G in transplantation, pregnancy, and cancer. We developed a next generation sequencing (NGS)-based typing assay enabling full phasing over the whole HLA-G gene sequence with inclusion of the 3'UTR region. DNA from 171 mother-child pairs (342 samples) was studied for: (a) HLA-G allele information by the NGSgo-AmpX HLA-G assay, (b) 3'UTR haplotype information by an in-house developed sequence-based typing method of a 699/713 base pair region in the 3'UTR, and (c) the full phase HLA-G gene sequence, by combining primers from both assays. The mother to child inheritance allowed internal verification of newly identified alleles and of association between coding and UTR regions. The NGSgo workflow compatible with Illumina platforms was employed. Data was interpreted using NGSengine software. In 99.4% of all alleles analyzed, the extended typing was consistent with the separate allele and 3'UTR typing methods. After repeated analysis of four samples that showed discrepancy, consistency reached 100%. A high-linkage disequilibrium between IPD-IMGT/HLA Database-defined HLA-G alleles and the extended 3'UTR region was identified (D' = 0.994, P < .0001). Strong associations were found particularly between HLA-G*01:04 and UTR-3, between HLA-G*01:01:03 and UTR-7, and between HLA-G*01:03:01 and UTR-5 (for all: r = 1). Six novel HLA-G alleles and three novel 3'UTR haplotype variants were identified, of which three and one, respectively, were verified in the offspring.
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http://dx.doi.org/10.1111/tan.13909DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7384165PMC
August 2020

Human leukocyte antigen selected allogeneic mesenchymal stromal cell therapy in renal transplantation: The Neptune study, a phase I single-center study.

Am J Transplant 2020 10 6;20(10):2905-2915. Epub 2020 May 6.

Department of Internal Medicine (Nephrology) and Transplant Center, Leiden University Medical Center, Leiden, the Netherlands.

Mesenchymal stromal cells (MSC) hold promise as a novel immune-modulatory therapy in organ transplantation. First clinical studies have used autologous MSCs; however, the use of allogeneic "off-the-shelf" MSCs is more sustainable for broad clinical implementation, although with the risk of causing sensitization. We investigated safety and feasibility of allogeneic MSCs in renal transplantation, using a matching strategy that prevented repeated mismatches. Ten patients received two doses of 1.5 × 10 /kg allogeneic MSCs 6 months after transplantation in a single-center nonrandomized phase Ib trial, followed by lowering of tacrolimus (trough level 3 ng/mL) in combination with everolimus and prednisone. Primary end point was safety, measured by biopsy proven acute rejection (BPAR) and graft loss 12 months after transplantation. Immune monitoring was performed before and after infusion. No BPAR or graft loss occurred and renal function remained stable. One patient retrospectively had DSAs against MSCs, formed before infusion. No major alterations in T and B cell populations or plasma cytokines were observed upon MSC infusion. Administration of HLA selected allogeneic MSCs combined with low-dose tacrolimus 6 months after transplantation is safe at least in the first year after renal transplantation. This sets the stage to further explore the efficacy of third-party MSCs in renal transplantation.
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http://dx.doi.org/10.1111/ajt.15910DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7586810PMC
October 2020
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