C E M Voorter

Maastricht University, Maestricht, Limburg, Netherlands

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Publications (113)229.45 Total impact

  • Christina E.M. Voorter · Mathijs Groeneweg · Lisette Groeneveld · Marcel G.J. Tilanus
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    ABSTRACT: Although the number of HLA alleles still increases, many of them have been reported being uncommon. This might partly be due to lack of full length gene sequencing, especially for those alleles belonging to an allele ambiguity in which the first discovered allele has been assigned as the most frequent one. As members of the working group on Common and Well Documented (CWD) alleles and since we implemented full length group-specific sequencing as standard method routinely, we have investigated the presence of presumably rare alleles in our collection of HLA typing data. We identified 50 alleles, that were not previously encountered as Common or Well Documented. Sixteen of them should be added to the CWD catalogue, since we encountered them in 5 or more unrelated individuals. Another 11 could be added, based upon our results and the data present in the IMGT database and the rare allele section of the allele frequencies database. Furthermore, tight associations were observed between several different alleles even at the level of synonymous and non-coding sequences. In addition, in several cases the uncommon allele was found to be more frequent than its common counterpart.
    No preview · Article · Nov 2015 · Human immunology
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    ABSTRACT: Currently 1582 HLA-DRB1 alleles have been identified in the IMGT/HLA database (v3.18). Among those alleles, more than 90% have incomplete allele sequences, which complicates the analysis of the functional relevance of polymorphism beyond exon 2. The polymorphic index of each individual exon of the currently known allele sequences, shows that polymorphism is present in all exons, albeit not equally abundant. Full-length HLA-DRB1 RNA sequencing identifies polymorphism of the complete coding region. Here we describe a hemizygous full-length RNA sequence-based typing (SBT) approach based on group-specific HLA-DRB1 amplification and subsequent sequencing. RNA full-length sequences can easily be accessed because of the short amplicon length (801 bp). The RNA-SBT approach was successfully validated on a panel of DRB1 alleles having fully known coding sequences according to the IMGT/HLA database, and cover all serological equivalents. Subsequently, the approach was applied on a panel of 54 alleles with incomplete allele sequences, resulting in full-length coding sequences and the identification of one new and one corrected allele. This study shows the universal applicability of the RNA-based sequencing approach to identify full-length coding sequences and to define the polymorphic content of HLA-DRB1 alleles.
    No preview · Article · Sep 2015 · Tissue Antigens
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    ABSTRACT: NK cells interact with the HLA-E molecule via the inhibitory receptor NKG2A and the activating receptor NKG2C. Hence, HLA-E can have a dual role in the immune response. In the present study, we aim to investigate the functional consequences of HLA-E for NKG2A and NKG2C expressing NK cell subsets by using a panel of HLA-E binding peptides derived from CMV, Hsp60 and HLA class I. PBMC derived from healthy subjects were used as targets for isolated NK cells and NK cell activation was examined by analysis of the expression of the degranulation marker CD107a. Peptide induced HLA-E expression inhibited degranulation of NKG2A+ NK cell subsets with almost all peptides, whereas NKG2A- NKG2C+ NK cell responses were enhanced only after incubation with four peptides; 1.3-fold with CMV(I), A80 and B13 and 3.2-fold with HLA-G derived peptide. In addition, the HLA-E:G peptide complex triggered NKG2C receptor internalization, as evidenced by reduction in the percentage of NKG2C+ NK cells when incubated with the peptide, which could be restored by addition of Bafilomycin. In conclusion: in contrast to NKG2A, NKG2C is regulated by HLA-E only when HLA-E is in complex with a restricted peptide repertoire, especially in combination with the HLA-G leader peptide. © 2015 American Society for Histocompatibility and Immunogenetics.
    No preview · Article · Sep 2015 · Human immunology
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    ABSTRACT: The full length sequence of HLA-A*02:455 differs from HLA-A*02:01:01:01 by one amino acid substitution: A245E. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
    No preview · Article · May 2015 · Tissue Antigens

  • No preview · Conference Paper · May 2015

  • No preview · Conference Paper · May 2015
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    ABSTRACT: Human Leukocyte Antigen (HLA)-E is a low-polymorphic non-classical HLA class I molecule which plays a crucial role in immune surveillance by presentation of peptides to T and natural killer (NK) cells. HLA-E polymorphism is related to HLA-E surface expression and is associated with patient outcome after stem cell transplantation. We aim to investigate the regulation of HLA-E expression level in peripheral blood mononuclear cells (PBMCs) of healthy individuals homozygous for HLA-E*01:01 or HLA-E*01:03, by using a panel of HLA-E binding peptides derived from CMV, Hsp60 and HLA class I. Basal and peptide-induced HLA-E surface expression levels were higher in PBMC from HLA-E*01:03 homozygous subjects as compared to PBMC from HLA-E*01:01 homozygous subjects. HLA-E mRNA levels were comparable between the two genotypes and remained constant after peptide stimulation. HLA-E surface expression seemed to be not only dependent on the HLA-E genotype, but also on the sequence of the peptide as evidenced by the profound difference in HLA-E upregulation with the Hsp60 and the B7 peptide. Our results showed that peptide-induced HLA-E expression is regulated at the posttranscriptional level as extracellular peptide stimulation did not influence RNA expression. This study provides new insights in the mechanism by which HLA-E expression is regulated and underlines a new role for extracellular peptides in inducing HLA-E translation, which may represent a defense mechanism against lytic viral infections and necrosis. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
    No preview · Article · Mar 2015 · Tissue Antigens
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    ABSTRACT: The assignment of null alleles is clinically relevant in stem cell transplantation, in particular for donor selection. It is unclear how questionable (Q) alleles, having an unknown expression profile, should be considered in matching criteria. In this study we analyzed the RNA and protein expression profile of a questionable allele encountered in a sample of the Guadeloupe population: GD23Q, HLA-A∗23:19Q, 29:02:01. Full-length DNA sequencing of HLA-A∗23:19Q revealed a single polymorphism at position 619 (G > A) compared to HLA-A∗23:01:01. Serological typing showed only the presence of HLA-A29; HLA-A∗23:19Q was not detected on the cell surface. The absence of HLA-A∗23:19Q surface expression was shown by flow cytometry using a directly labeled monoclonal antibody and a panel of five indirectly labeled polyclonal antibodies all directed against HLA-A23 (HLA-A9) molecules. Allele specific amplification revealed the absence of intact full-length mRNA, but the presence of two major alternatively spliced mRNAs: sequencing identified that in one variant exon 3 is missing and in the other variant introns 2 and 3 are retained. Based upon the lack of HLA-A∗23:19Q surface expression and the presence of aberrant mRNA transcripts only, this study shows that HLA-A∗23:19Q is non-expressed.
    Full-text · Article · Feb 2015 · Human Immunology
  • V B G Crijns · F Palusci · H C Schouten · C E M Voorter · M G J Tilanus
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    ABSTRACT: HLA-C*03:219 differs from HLA-C*03:04:01:01 by a non-synonymous substitution in the α3 domain (T216I). © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
    No preview · Article · Dec 2014 · Tissue Antigens
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    L. Wieten · N. M. Mahaweni · C. E.M. Voorter · G. M.J. Bos · M. G.J. Tilanus
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    ABSTRACT: Human leukocyte antigen-E (HLA-E) is a nonclassical HLA class I molecule that canonically binds peptides derived from the leader sequence of classical HLA class I. HLA-E can also bind peptides from stress protein [e.g. heat shock protein 60 (Hsp60)] and pathogens, illustrating the importance of HLA-E for anti-viral and anti-tumor immunity. Like classical HLA class I molecules, HLA-E is ubiquitously expressed, however, it is characterized by only a very limited sequence variability and two dominant protein forms have been described (HLA-E*01:01 and HLA-E*01:03). HLA-E influences both the innate and the adaptive arms of the immune system by the engagement of inhibitory (e.g. NKG2A) and activating receptors [e.g. αβ T cell receptor (αβTCR) or NKG2C] on NK cells and CD8 T cells. The effects of HLA-E on the cellular immune response are therefore complex and not completely understood yet. Here, we aim to provide an overview of the immunological and clinical relevance of HLA-E and HLA-E polymorphism in stem cell transplantation and in cancer. We review novel insights in the mechanism via which HLA-E expression levels are controlled and how the cellular immune response in transplantation and cancer is influenced by HLA-E.
    Full-text · Article · Dec 2014 · Tissue Antigens
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    ABSTRACT: It is clinically relevant to assign null alleles since they affect the donor selection in stem cell transplanta-tion due to their absence on the cell surface. Questionable alleles however, are a problem since their expression profile is unknown, which makes it unclear how they should be considered in matching criteria. The nomenclature committee assigns alleles as questionable when they carry a mutation that has previously been shown to have a significant effect on cell surface expression but has not been confirmed. In this study the expression profile of one of these questionable alleles HLA-A⁄23:19Q is addressed. This allele has one known substitution in exon 3 at position 619 (G > A) compared to HLA-A⁄23:01:01. We encountered HLA-A⁄23:19Q in a sample of our population study of Guadeloupe (HLA-A⁄23:19Q, 29:02:01). Serological typing of the sample showed only the presence of A29, suggesting that A⁄23:19Q was not expressed on the cell surface, whereas the presence of the A⁄23:19Q allele was confirmed by SBT DNA sequencing. Interestingly, allele specific sequencing of mRNA revealed the absence of an intact full-length 'normal' mRNA product and the presence of two alternatively spliced mRNAs. Sequencing these two variants resulted in one variant missing exon 3 and the other variant retaining introns 2 and 3. Both these variants will not encode a regular A23 molecule because of the lack of the a2 domain, whereas intron 2 introduces a premature stop codon. To confirm the lack of expression of A⁄23:19Q the patient sample was transformed into an EBV cell line and used for flow cytometry analysis of HLA cell surface expression. The absence of HLA-A⁄23:19Q on the cell surface was shown by using a directly labelled A9 monoclonal antibody and indirect labelling of multiple patient sera having polyclonal antibodies directed against A9 and A23. Based upon the lack of detection of A⁄23:19Q cell surface expression and the absence of a full length mRNA transcript, this study indicates that A⁄23:19Q should be reclassified as a null allele.
    Full-text · Conference Paper · Oct 2014
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    Full-text · Conference Paper · Oct 2014
  • Article: P054

    No preview · Article · Oct 2014
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    Full-text · Conference Paper · Oct 2014
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    Full-text · Conference Paper · Oct 2014
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    ABSTRACT: Kidney transplantation is the best treatment option for patients with end-stage renal failure. At present, approximately 800 Dutch patients are registered on the active waiting list of Eurotransplant. The waiting time in the Netherlands for a kidney from a deceased donor is on average between 3 and 4 years. During this period, patients are fully dependent on dialysis, which replaces only partly the renal function, whereas the quality of life is limited. Mortality among patients on the waiting list is high. In order to increase the number of kidney donors, several initiatives have been undertaken by the Dutch Kidney Foundation including national calls for donor registration and providing information on organ donation and kidney transplantation. The aim of the national PROCARE consortium is to develop improved matching algorithms that will lead to a prolonged survival of transplanted donor kidneys and a reduced HLA immunization. The latter will positively affect the waiting time for a retransplantation.
    Full-text · Article · Sep 2014 · Transplant Immunology
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    ABSTRACT: Our understanding of the immunological processes influencing the clinical outcome after kidney transplantation has advanced majorly over the last few decades. However, many factors still restrict graft and patient survival. Within the Maastricht transplant centre we have successfully implemented an alternative immunosuppressive regimen involving Tacrolimus monotherapy in order to minimize the adverse effects associated with long-term use of immunosuppressive drugs. This clinical development has an impact on pre-transplant risk stratification which requires that patients are closely monitored immunologically. In this review we will elaborate on our strategy regarding the analysis of epitopes in HLA-DQ and HLA-DP molecules. In this respect we have also looked at the immunodominance of certain epitopes by assessing their structural localisation, conformation and physiochemical properties.
    No preview · Article · Sep 2014 · Transplant Immunology
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    ABSTRACT: The functional relevance of human leukocyte antigen (HLA) class I allele polymorphism beyond exons 2 and 3 is difficult to address because more than 70% of the HLA class I alleles are defined by exons 2 and 3 sequences only. For routine application on clinical samples we improved and validated the HLA sequence-based typing (SBT) approach based on RNA templates, using either a single locus-specific or two overlapping group-specific polymerase chain reaction (PCR) amplifications, with three forward and three reverse sequencing reactions for full length sequencing. Locus-specific HLA typing with RNA SBT of a reference panel, representing the major antigen groups, showed identical results compared to DNA SBT typing. Alleles encountered with unknown exons in the IMGT/HLA database and three samples, two with Null and one with a Low expressed allele, have been addressed by the group-specific RNA SBT approach to obtain full length coding sequences. This RNA SBT approach has proven its value in our routine full length definition of alleles.
    No preview · Article · Sep 2014 · Tissue Antigens
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    ABSTRACT: A total of 1,411 HLA-DRB1 alleles have been identified mainly based on exon 2 encoding the peptide-binding groove (IMGT/HLA v3.15). Nonetheless, 90% of these alleles have multiple unknown exons and by calculating their polymorphic index, itwas shown that the polymorphic content is dispersed among the different exons. Full length sequencing will give an insight in the polymorphic content of the other exons. However, sequencing approaches based on DNA are hampered by the long and variable length of intron 1 and multiple overlapping PCR reactions are required to achieve a reliable full length sequencing result. The advantage of an RNA approach is that the relatively short fragment length of ±800 bp makes it possible to cover the full-length coding region of the alleles directly. In this study we describe our RNA approach for HLA-DRB1 sequencing. RNA was isolated from EBV B-cell lines and transcribed into cDNA using oligo-dT primers. Group-specific amplification of DRB1 was achieved by combining a locus specific primer in the 5′ or 3′ UTR with a group specific primer located in exon 2 or 3 in two separate amplification reactions. Full length forward and reverse sequencing was achieved using the amplification primers combined with an additional forward sequencing primer in exon 3. Our method was successfully validated on a panel of fully known DRB1 alleles covering the major serological determinants. To test the applicability of our method, we selected a panel of 52 cell lines with different DRB1 alleles that represent all major serological groups and of which the sequences beyond exon 2 were unknown. This panel showed there were no differences beyond exon 2 compared to its full length known allele equivalent. The results of this study indicate a low degree of previously unknown polymorphisms in the other exons and that the calculated polymorphic index based on IMGT/HLA v3.15 reflects the diversity of DRB1.
    Full-text · Conference Paper · Jun 2014
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    ABSTRACT: The Luminex SSO method is a routine HLA DNA typing method based on the most polymorphic regions, exons 2 and 3, of the HLA class I and II molecules. However, additional polymorphism has been found beyond these exons. To study this polymorphism additional PCR reactions are needed in DNA approaches. Using RNA instead of DNA as template would make a simultaneous amplification of the full coding sequence possible in a single PCR. In this study, RNA was used as template for cDNA synthesis and subsequently for HLA-A, -B, -C, -DRB1 and -DQA1/B1 typing using the existing Luminex SSO method for DNA (One Lambda). To validate whether cDNA was a suitable replacement for DNA, a panel of 10 samples for each locus was used, including variable HLA class I and II alleles. For all samples DNA and RNA was isolated using QIAamp DNA blood Mini kit and RNeasy Mini Kit (QIAgen, Hilden, Germany), respectively. cDNA was synthesized with Life Technologies reagents (Bleiswijk, The Netherlands). DNA and cDNA were used as starting material for the Luminex SSO method and HLA typing results were compared. For HLA class I, HLA-A, -B and –C, only a few false negative and false positive reactions were encountered in the typing results using cDNA as compared to DNA. However, the majority of false negative reactions could be resolved by adapting the cutoff value to the cutoff as determined using 50 randomized chosen DNA samples from our department. For HLA class II, correct typing results for all HLA-DRB1, -DQA1 and –DQB1 samples were obtained with cDNA,making the cDNA SSO method directly applicable without any adaptations for HLA class II alleles. Our results imply that with the use of cDNA full length polymorphism allele assignment with Luminex technology is feasible.
    Full-text · Conference Paper · Jun 2014

Publication Stats

1k Citations
229.45 Total Impact Points

Institutions

  • 1999-2015
    • Maastricht University
      Maestricht, Limburg, Netherlands
  • 1997-2014
    • Maastricht Universitair Medisch Centrum
      • Central Diagnostic Laboratory
      Maestricht, Limburg, Netherlands
  • 2009
    • University of Bologna
      Bolonia, Emilia-Romagna, Italy