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An increasing number of bispecific therapeutic antibodies are progressing through clinical development. The Knob-into-Hole (KiH) technology uses complementary mutations in the CH3 region of the antibody Fc fragment to achieve heavy chain heterodimerization. Here we describe the X-ray crystal structures of glycosylated and disulfide-engineered heterodimeric KiH Fc fragment and its homodimeric Knob–Knob and Hole–Hole side products. The heterodimer structure confirms the KiH design principle and supports the hypothesis that glycosylation stabilizes a closed Fc conformation. Both homodimer structures show parallel Fc fragment architectures, in contrast to recently reported crystal structures of the corresponding aglycosylated Fc fragments which in the absence of disulfide mutations show an unexpected antiparallel arrangement. The glycosylated Knob–Knob Fc fragment is destabilized as indicated by variability in the relative orientation of its CH3 domains. The glycosylated Hole–Hole Fc fragment shows an unexpected intermolecular disulfide bond via the introduced Y349C Hole mutation which results in a large CH3 domain shift and a new CH3–CH3 interface. The crystal structures of glycosylated, disulfide-linked KiH Fc fragment and its Knob–Knob and Hole–Hole side products reported here will facilitate further design of highly efficient antibody heterodimerization strategies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Estimation of human leukocyte antigen ( HLA) haplotype frequencies from unrelated stem cell donor registries presents a challenge because of large sample sizes and heterogeneity of HLA typing data. For the 14th International HLA and Immunogenetics Workshop, five bioinformatics groups initiated the 'Registry Diversity Component' aiming to cross-validate and improve current haplotype estimation tools. Five datasets were derived from different donor registries and then used as input for five different computer programs for haplotype frequency estimation. Because of issues related to heterogeneity and complexity of HLA typing data identified in the initial phase, the same five implementations, and two new ones, were used on simulated datasets in a controlled experiment where the correct results were known a priori. These datasets contained various fractions of missing HLA-DR modeled after European haplotype frequencies. We measured the contribution of sampling fluctuation and estimation error to the deviation of the frequencies from their true values, finding equivalent contributions of each for the chosen samples. Because of patient-directed activities, selective prospective typing strategies and the variety and evolution of typing technology, some donors have more complete and better HLA data. In this setting, we show that restricting estimation to fully typed individuals introduces biases that could be overcome by including all donors in frequency estimation. Our study underlines the importance of critical review and validation of tools in registry-related activity and provides a sustainable framework for validating the computational tools used. Accurate frequencies are essential for match prediction to improve registry operations and to help more patients identify suitably matched donors. [ABSTRACT FROM AUTHOR]

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 16 IHIW meeting in Liverpool. [ABSTRACT FROM AUTHOR]

Human leukocyte antigen (HLA)-E is an inhibitory ligand of natural killer cells and γ/δ T-cells. Differential expression of HLA-E alleles on the cell surface has been reported to influence outcome of hematopoietic stem cell transplantation (HSCT). We performed HLA-E genotyping in 116 HSCT patients and their HLA-matched unrelated donors. The impact of HLA-E genotypes on patient's overall survival (OS), disease free survival (DFS), cumulative incidences for relapse, transplant-related mortality (TRM) and acute graft vs host disease (aGvHD) was assessed. Neither univariate nor multivariate analysis showed any influence of HLA-E polymorphisms on the investigated endpoints of HSCT in our cohort. We could not confirm any of the previous observations in our cohort and consider it unlikely that HLA-E polymorphisms affect outcome of HSCT. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Nearly half of the unrelated hematopoietic SCTs facilitated worldwide involves an exchange of products between countries. The process is information intensive and requires coordination through regional hubs of complex data transactions of demographic, clinical and genetic information, laboratory samples and results. Each registry has developed its own unique systems for representing data and process leading to transplantation. The WMDA Information Technology Working Group was formed in the autumn of 2001 as a forum to discuss and develop standards for information technology (IT) in support of hematopoietic stem cell registries. Its membership includes experts in IT from the WMDA member registries. The group has focused its standardization efforts on three areas: Standardized reference data sets for validation and plausibility controls for HLA and other data domainsMatching algorithm standards for determining histocompatibilityCommunication standards between registries. [ABSTRACT FROM AUTHOR]

The article presents a report documenting the additions and revisions to the nomenclature of HLA specificities. It states that a number of HLA gene fragments have been reported and named which includes HLA-T previously known as HLA-16 and HLA-V previously known as HLA-75. It further discusses the conditions for acceptance of new genes and allele sequences for official names. It also presents lists of the serological specificities or antigens associated with the alleles.

Allogeneic haematopoietic SCT is a standard therapy for many patients with haematological diseases. A major aim of public umbilical cord blood (UCB) banking is to establish an inventory with a large HLA diversity. Few studies have compared HLA diversity between UCB banks and volunteer unrelated donor (VUD) registries and examined whether UCB banks indeed collect more units with rare alleles and haplotypes. This study compares HLA-A/B/DRB1 allele frequencies and inferred A/B/DRB1-haplotypes in 1602 UCB units and 3093 VUD from two centres in distinct recruitment areas in Switzerland. The results show that the frequencies of HLA-DRB1 alleles as well as of the HLA-A/B/DRB1 haplotypes differ between UCB and VUD. Ten DRB1 alleles occurred at a 2- to 12-fold higher relative frequency in UCB than in VUD and 27 rare alleles were identified in UCB. Out of these 27 alleles, 15 were absent in the entire VUD data set of the national registry. This difference in allele frequencies was found only by intermediate/high-resolution typing. Targeted recruitment of UCB units from non-Caucasian donors could further increase HLA allele and haplotype diversity of available donors. Intermediate or high-resolution DNA typing is essential to identify rare alleles or allele groups.Bone Marrow Transplantation (2009) 43, 771–778; doi:10.1038/bmt.2008.391; published online 8 December 2008 [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

For more than two decades, international cooperation and information technology have been playing key roles in the identification of suitable unrelated donors and cord blood units for hematopoietic SCT. To ensure consistent coding and interpretation of HLA data among the linked computer systems, the World Marrow Donor Association has standardized the extensions of the World Health Organization (WHO) Nomenclature for factors of the HLA system applied in practice. The first version of this report published in 2007 has become the reference for the technical validation of HLA information on donors and patients in the context of search and matching and is used by registries of volunteer unrelated hematopoietic stem cell donors and umbilical cord blood banks throughout the world. The present update became necessary after the major revision of the WHO HLA nomenclature in April 2010. It now covers issues arising when alleles are withdrawn or renamed because of the continuous updating of the WHO HLA nomenclature. In addition, formal validation and interpretation rules for the so-called 'multiple allele codes' have been added. [ABSTRACT FROM AUTHOR]

Good communication between the bone marrow registries, the donor centres, tissue typing laboratories and clinical units is paramount to ensure timely identification, testing and selection of donors for unrelated bone marrow transplants. This panel session focussed on how to improve communication so that there was a clear understanding of prioritization of requests from clinicians, typing strategies in the laboratories and requests for donors to the registries. This paper outlined some of the strategies discussed in this session. [ABSTRACT FROM AUTHOR]