Carlheinz Müller

Nomenclature for factors of the HLA system, 2010

The WHO Nomenclature Committee for Factors of the HLA System met following the 14th International HLA and Immunogenetics Workshop in Melbourne, Australia in December 2005 and Buzios, Brazil during the 15th International HLA and Immunogenetics Workshop in September 2008. This report documents the additions and revisions to the nomenclature of HLA specificities following the principles established in previous reports (1–18).

High-resolution HLA matching in hematopoietic stem cell transplantation: a retrospective collaborative analysis

To validate current donor selection strategies based on previous international studies, we retrospectively analyzed 2646 transplantations performed for hematologic malignancies in 28 German transplant centers. Donors and recipients were high resolution typed for HLA-A, -B, -C, -DRB1, and -DQB1. The highest mortality in overall survival analysis was seen for HLA-A, -B, and DRB1 mismatches. HLA-DQB1 mismatched cases showed a trend toward higher mortality, mostly due to HLA-DQB1 antigen disparities. HLA incompatibilities at >1 locus showed additive detrimental effects. HLA mismatching had no significant effect on relapse incidence and primary graft failure. Graft source had no impact on survival end points, neither in univariate nor in multivariate analysis. Higher patient age, advanced disease, transplantations before 2004, patient C2C2 killer cell immunoglobulin-like receptor (KIR)-ligand phenotype, and unavailability of a national donor adversely influenced outcomes in multivariate analysis. Our study confirms the association of HLA-A, -B, -C, and -DRB1 incompatibilities with adverse outcome in hematopoietic stem cell transplantation (HSCT). The relevance of HLA-DQB1 disparities in single mismatched transplantations remains unclear. Similar hazard ratios for allele and antigen mismatches (possibly with an exception for HLA-DQB1) highlight the importance of allele level typing and matching in HSCT. The number of incompatibilities and their type significantly impact survival.

An update to HLA Nomenclature, 2010

The WHO Nomenclature Committee for Factors of the HLA System met during the 15th International Histocompatibility and Immunogenetics Workshop in Buzios, Brazil in September 2008. This update is an extract of the main report that documents the additions and revisions to the nomenclature of human leukocyte antigen (HLA) specificities following the principles established in previous reports.

Estimating unbiased haplotype frequencies from stem cell donor samples typed at heterogeneous resolutions: a practical study based on over 1 million German donors

The human leukocyte antigen (HLA) distribution in donor registry data is typically nonrandom as, mostly for economical reasons, typing additional loci or resolving ambiguities is selectively performed based on the previously known HLA type. Analyzing a sample of over 1 million German stem cell donors, we practically show the extent of the bias caused by the restriction of the input data for HLA haplotype frequency (HF) estimation to subsets selected according to their higher HLA typing resolution and, conversely, the correctness of estimates based on unselected data with a methodology suitable for heterogeneous resolution. We discuss algorithmic aspects of this approach and, also because of the sample size, provide some new insights into the distribution of HLA-DRB1 alleles in the German population and the application of HFs in unrelated donor search.

Hematopoietic stem cell donor registry strategies for assigning search determinants and matching relationships.

Summary:Registries and cord blood banks around the world collect and store the HLA types of volunteers in order to identify matched unrelated donors for patients requiring hematopoietic stem cell transplantation. This task is complicated by the many formats in which HLA types are provided by the testing laboratories (types obtained by serology vs by DNA-based methods; high vs intermediate vs low resolution) and by the need to identify which of these diverse types are most likely to match the HLA assignments of a searching patient as closely as possible. Conversion of the assignments to ‘search determinants’ may be included within the algorithm used to select and prioritize a list of potentially suitable donors, either as an aid to matching or as a tool to optimize the performance of comparisons within large data files. The strategies used by registries to create search determinants are described. A set of search determinants, utilized by the National Marrow Donor Program, is provided as an example and is intended to initiate further discussion aimed at understanding the process used by each registry with the possibility of developing a standard process among registries worldwide.

Impact of KIR and HLA Genotypes on Outcomes after Reduced-Intensity Conditioning Hematopoietic Cell Transplantation

Natural killer cells are regulated by killer cell immunoglobulin-like receptor (KIR) interactions with HLA class I ligands. Several models of natural killer cell reactivity have been associated with improved outcomes after myeloablative allogeneic hematopoietic cell transplantation (HCT), but this issue has not been rigorously addressed in reduced-intensity conditioning (RIC) unrelated donor (URD) HCT. We studied 909 patients undergoing RIC-URD HCT. Patients with acute myeloid leukemia (AML, n = 612) lacking ≥ 1 KIR ligands experienced higher grade III to IV acute graft-versus-host disease (GVHD) (HR, 1.6; 95% CI, 1.16 to 2.28; P = .005) compared to those with all ligands present. Absence of HLA-C2 for donor KIR2DL1 was associated with higher grade II to IV (HR, 1.4; P = .002) and III to IV acute GVHD (HR, 1.5; P = .01) compared with HLA-C2(+) patients. AML patients with KIR2DS1(+), HLA-C2 homozygous donors had greater treatment-related mortality compared with others (HR, 2.4; 95% CI, 1.4 to 4.2; P = .002) but did not experience lower relapse. There were no significant associations with outcomes for AML when assessing donor-activating KIRs or centromeric KIR content or for any donor-recipient KIR-HLA assessments in patients with myelodysplastic syndrome (n = 297). KIR-HLA combinations in RIC-URD HCT recapitulate some but not all KIR-HLA effects observed in myeloablative HCT.

16 th IHIW: Global analysis of registry HLA haplotypes from 20 Million individuals: Report from the IHIW Registry Diversity Group

This project has the goal to validate bioinformatics methods and tools for HLA haplotype frequency analysis specifically addressing unique issues of haematopoietic stem cell registry data sets. In addition to generating new methods and tools for the analysis of registry data sets, the intent is to produce a comprehensive analysis of HLA data from 20 million donors from the Bone Marrow Donors Worldwide (BMDW) database. This report summarizes the activity on this project as of the 16IHIW meeting in Liverpool.

World Marrow Donor Association framework for the implementation of HLA matching programs in hematopoietic stem cell donor registries and cord blood banks

A major goal of the World Marrow Donor Association (WMDA) is to foster international transplants of hematopoietic stem cells through the establishment of guidelines and recommendations in this field. In this tradition, this study defines a comprehensive framework for HLA matching programs, which use intricate algorithms to rapidly select potential donors for a patient from a database and to present these donors in a prioritized list. Starting with the comparison of single HLA markers of the donor and the patient possibly obtained using different testing methodologies at different resolutions, the more complex matching of loci and phenotypes is inductively built up. The consensus of this international collaborative group describes the state of the art in the field and points out many important design options compatible with the best practice. This should help existing registries to review and validate the most critical part of their IT systems and newly created donor registries around the world to tackle one of their real challenges.

A comparative reference study for the validation of HLA‐matching algorithms in the search for allogeneic hematopoietic stem cell donors and cord blood units

The accuracy of human leukocyte antigen (HLA)‐matching algorithms is a prerequisite for the correct and efficient identification of optimal unrelated donors for patients requiring hematopoietic stem cell transplantation. The goal of this World Marrow Donor Association study was to validate established matching algorithms from different international donor registries by challenging them with simulated input data and subsequently comparing the output. This experiment addressed three specific aspects of HLA matching using different data sets for tasks of increasing complexity. The first two tasks targeted the traditional matching approach identifying discrepancies between patient and donor HLA genotypes by counting antigen and allele differences. Contemporary matching procedures predicting the probability for HLA identity using haplotype frequencies were addressed by the third task. In each task, the identified disparities between the results of the participating computer programs were analyzed, classified and quantified. This study led to a deep understanding of the algorithms participating and finally produced virtually identical results. The unresolved discrepancies total to less than 1%, 4% and 2% for the three tasks and are mostly because of individual decisions in the design of the programs. Based on these findings, reference results for the three input data sets were compiled that can be used to validate future matching algorithms and thus improve the quality of the global donor search process.

Minimum information for reporting next generation sequence genotyping (MIRING): Guidelines for reporting HLA and KIR genotyping via next generation sequencing

The development of next-generation sequencing (NGS) technologies for HLA and KIR genotyping is rapidly advancing knowledge of genetic variation of these highly polymorphic loci. NGS genotyping is poised to replace older methods for clinical use, but standard methods for reporting and exchanging these new, high quality genotype data are needed. The Immunogenomic NGS Consortium, a broad collaboration of histocompatibility and immunogenetics clinicians, researchers, instrument manufacturers and software developers, has developed the Minimum Information for Reporting Immunogenomic NGS Genotyping (MIRING) reporting guidelines. MIRING is a checklist that specifies the content of NGS genotyping results as well as a set of messaging guidelines for reporting the results. A MIRING message includes five categories of structured information - message annotation, reference context, full genotype, consensus sequence and novel polymorphism - and references to three categories of accessory information - NGS platform documentation, read processing documentation and primary data. These eight categories of information ensure the long-term portability and broad application of this NGS data for all current histocompatibility and immunogenetics use cases. In addition, MIRING can be extended to allow the reporting of genotype data generated using pre-NGS technologies. Because genotyping results reported using MIRING are easily updated in accordance with reference and nomenclature databases, MIRING represents a bold departure from previous methods of reporting HLA and KIR genotyping results, which have provided static and less-portable data. More information about MIRING can be found online at miring.immunogenomics.org.