Clinical validation of NGS technology for HLA: An early adopter’s perspective

HLA-A, -B, -C, -DRB1 allele and haplotype frequencies of the Korean population and performance characteristics of HLA typing by next-generation sequencing

INTRODUCTION

Human leukocyte antigen (HLA) identification at the allelic level is important for haematopoietic stem cell transplantation (HSCT). Next-generation sequencing (NGS) resolves ambiguous alleles by determining the phase of the polymorphisms. The aim of this study was to validate the software for HLA-SBT (sequence-based typing), assess Korean allele frequency, and characterise the performance of NGS-HLA typing.

METHODS

From the 2009 to 2016 registry, 1293 unrelated healthy donors with a complete dataset of previously characterised HLA-A, -B, -C, and -DRB1 loci were selected and assessed for frequency, haplotype inference, and relative linkage disequilibrium. For performance characteristics of NGS-HLA, alleles included in 1293 cases and ambiguous or alleles assigned as new by SBT-HLA software, or unassigned alleles were included. A total of 91 and 41 quality control samples resulted in 1056 alleles (132 samples × 4 loci × 2 diploid) for analysis. The GenDx NGSgo kit was used for NGS-HLA typing using the Illumina MiSeq platform.

RESULTS

A panel of 132 samples covered 231 alleles, including 53 HLA-A, 80 HLA-B, 43 HLA-C, and 55 HLA-DRB1 by HLA-SBT typing. Comparison of SBT-HLA and NGS-HLA typing showed 99.7% (1053/1056) concordance and discrepant cases were resolved by manual evaluation. Typing by NGS resulted in 67 HLA-A, 112 HLA-B, 71 HLA-C, and 72 HLA-DRB1 alleles. A total of 132 ambiguous, 4 new, and 1 unassigned alleles by HLA-SBT were resolved by NGS-HLA typing.

CONCLUSIONS

NGS-HLA typing provided robust and conclusive results without ambiguities, and its implementation could support HSCT in clinical settings.

Next-generation sequencing of HLA: validation and identification of new polymorphisms in a Brazilian population

BACKGROUND

Next-generation sequencing (NGS) is the most modern sequencing technique that has revolutionized HLA typing, providing high-resolution results with low ambiguity rates. This study aimed to show the experiences and challenges of an HLA laboratory in the validation process of the NGS methodology for HLA typing and show the use of this method for the study of HLA genetic diversity.

METHODS

We used 115 samples that comprised a comprehensive testing panel for validation of the NGS methodology using the AllType kit (One Lambda, Canoga Park, California) on the Ion Torrent S5 NGS platform. All quality metrics were analyzed. During validation, two new HLA sequences were identified and named by the HLA Nomenclature Committee.

RESULTS

A total of 1380 alleles from the HLA-A, -B, -C, -DRB1, -DQB1, and -DPB1 loci were examined by NGS. This validation panel provided a wide range of HLA sequence variations, including non-CWD HLA alleles, new variants, and homozygous alleles. The concordance rate with Sanger sequencing-based typing was 100.0% for HLA-A, -B, -C, -DRB1, -DQB1, and 99.93% for HLA-DPB1. The newly identified HLA alleles were HLA-B*14:69N and HLA-DQB1*02:145.

CONCLUSION

We have successfully validated NGS HLA typing despite numerous challenges, contributing to the identification of novel alleles that impact on HLA matching and antibody evaluation in organ and tissue transplantation.

A new set of reagents and related software used for NGS based classical and non-classical HLA typing showing evidence for a greater HLA haplotype diversity

To evaluate the HLA typing performance of a new Long-Range PCR NGS set of reagents and its dedicated software, a panel of 41 reference homozygous cell lines from the International Histocompatibility Working Group (IHWG) and a panel of 376 volunteer bone marrow donors were analyzed for classical and non-classical HLA class I and class II genes. All results, except HLA-DPB1, were obtained without any ambiguities at the 3rd field level. Based on the high resolution performance of the reagents, a number of new alleles have been described not only for classical but also for non-classical HLA class I genes, leading to a more accurate haplotype definition. Linkage disequilibrium between HLA-A and HLA-G genes has been defined at 4th field level of resolution. Moreover, for the first time, HLA-DQA2 and DQB2 polymorphisms and their linkage disequilibrium with DQB1 were described.

Human Leukocyte Antigen alleles as an aid to STR in complex forensic DNA samples

Human biological samples with multiple contributors remain one of the most challenging aspects of DNA typing within a forensic science context. With the increasing sensitivity of commercially available kits allowing detection of low template DNA, complex mixtures are now a standard component of forensic DNA evidence. Over the years, various methods and techniques have been developed to try to resolve the issue of mixed profiles. However, forensic DNA analysis has relied on the same markers to generate DNA profiles for the past 30 years causing considerable challenges in the deconvolution of complex mixed samples. The future of resolving complicated DNA mixtures may rely on utilising markers that have been previously applied to gene typing of non-forensic relevance. With Massively Parallel Sequencing (MPS), techniques becoming more popular and accessible even epigenetic markers have become a source of interest for forensic scientists. The aim of this review is to consider the potential of alleles from the Human Leukocyte Antigen (HLA) complex as effective forensic markers. While Massively Parallel Sequencing of HLA is routinely used in clinical laboratories in fields such as transplantation, pharmacology or population studies, there have not been any studies testing its suitability for forensic casework samples.

The Past, Present, and Future of HLA Typing in Transplantation

The HLA region is the most polymorphic genes in the human genome and is associated with an increasing number of disease states. Historically, HLA typing methodology has been governed by phenotypic determination. This practice has evolved into the use of molecular methods such as real-time PCR, sequence-specific oligonucleotides, and sequencing-based methods. Numerous studies have identified HLA matching as a key determinate to improve patient outcomes from transplantation. Solid-organ transplants focus on HLA-DRB1 in renal organ allocation while hematopoietic cell transplants focus on HLA-A, -B, -C, -DRB1 matching. The role of HLA typing in the future will be driven by HLA expression, understanding of HLA haplotypes, and rapid HLA typing.

High resolution HLA haplotyping by imputation for a British population bioresource

This study aimed to establish the occurrence and frequency of HLA alleles and haplotypes for a healthy British Caucasian population bioresource from Oxfordshire. We present the results of imputation from HLA SNP genotyping data using SNP2HLA for 5553 individuals from Oxford Biobank, defining one- and two-field alleles together with amino acid polymorphisms. We show that this achieves a high level of accuracy with validation using sequence-specific primer amplification PCR. We define six- and eight-locus HLA haplotypes for this population by Bayesian methods implemented using PHASE. We determine patterns of linkage disequilibrium and recombination for these individuals involving classical HLA loci and show how analysis within a haplotype block structure may be more tractable for imputed data. Our findings contribute to knowledge of HLA diversity in healthy populations and further validate future large-scale use of HLA imputation as an informative approach in population bioresources.