TripHLApan: predicting HLA molecules binding peptides based on triple coding matrix and transfer learning.

Human leukocyte antigen (HLA) recognizes foreign threats and triggers immune responses by presenting peptides to T cells. Computationally modeling the binding patterns between peptide and HLA is very important for the development of tumor vaccines. However, it is still a big challenge to accurately predict HLA molecules binding peptides. In this paper, we develop a new model TripHLApan for predicting HLA molecules binding peptides by integrating triple coding matrix, BiGRU + Attention models, and transfer learning strategy. We have found the main interaction site regions between HLA molecules and peptides, as well as the correlation between HLA encoding and binding motifs. Based on the discovery, we make the preprocessing and coding closer to the natural biological process. Besides, due to the input being based on multiple types of features and the attention module focused on the BiGRU hidden layer, TripHLApan has learned more sequence level binding information. The application of transfer learning strategies ensures the accuracy of prediction results under special lengths (peptides in length 8) and model scalability with the data explosion. Compared with the current optimal models, TripHLApan exhibits strong predictive performance in various prediction environments with different positive and negative sample ratios. In addition, we validate the superiority and scalability of TripHLApan's predictive performance using additional latest data sets, ablation experiments and binding reconstitution ability in the samples of a melanoma patient. The results show that TripHLApan is a powerful tool for predicting the binding of HLA-I and HLA-II molecular peptides for the synthesis of tumor vaccines. TripHLApan is publicly available at https://github.com/CSUBioGroup/TripHLApan.git.

Improving HLA typing imputation accuracy and eplet identification with local next-generation sequencing training data.

Assessing donor/recipient HLA compatibility at the eplet level requires second field DNA typings but these are not always available. These can be estimated from lower-resolution data either manually or with computational tools currently relying, at best, on data containing typing ambiguities. We gathered NGS typing data from 61,393 individuals in 17 French laboratories, for loci A, B, and C (100% of typings), DRB1 and DQB1 (95.5%), DQA1 (39.6%), DRB3/4/5, DPB1, and DPA1 (10.5%). We developed HaploSFHI, a modified iterative maximum likelihood algorithm, to impute second field HLA typings from low- or intermediate-resolution ones. Compared with the reference tools HaploStats, HLA-EMMA, and HLA-Upgrade, HaploSFHI provided more accurate predictions across all loci on two French test sets and four European-independent test sets. Only HaploSFHI could impute DQA1, and solely HaploSFHI and HaploStats provided DRB3/4/5 imputations. The improved performance of HaploSFHI was due to our local and nonambiguous data. We provided explanations for the most common imputation errors and pinpointed the variability of a low number of low-resolution haplotypes. We thus provided guidance to select individuals for whom sequencing would optimize incompatibility assessment and cost-effectiveness of HLA typing, considering not only well-imputed second field typing(s) but also well-imputed eplets.

Helper T cell immunity in humans with inherited CD4 deficiency.

CD4+ T cells are vital for host defense and immune regulation. However, the fundamental role of CD4 itself remains enigmatic. We report seven patients aged 5-61 years from five families of four ancestries with autosomal recessive CD4 deficiency and a range of infections, including recalcitrant warts and Whipple's disease. All patients are homozygous for rare deleterious CD4 variants impacting expression of the canonical CD4 isoform. A shorter expressed isoform that interacts with LCK, but not HLA class II, is affected by only one variant. All patients lack CD4+ T cells and have increased numbers of TCRαß+CD4-CD8- T cells, which phenotypically and transcriptionally resemble conventional Th cells. Finally, patient CD4-CD8- αß T cells exhibit intact responses to HLA class II-restricted antigens and promote B cell differentiation in vitro. Thus, compensatory development of Th cells enables patients with inherited CD4 deficiency to acquire effective cellular and humoral immunity against an unexpectedly large range of pathogens. Nevertheless, CD4 is indispensable for protective immunity against at least human papillomaviruses and Trophyrema whipplei.

Daratumumab treatment in six highly sensitised solid organ transplant recipients: A case series and literature review.

We report data on six kidney or heart recipients who were administered daratumumab to treat or prevent antibody-mediated rejection (ABMR). To date, data are scarce concerning the use of daratumumab in solid organ transplantation and most reports show a decrease in donor-specific antigen (DSA) levels and an improvement in ABMR using a multiple myeloma daratumumab administration scheme, that is, with sequential systematic administration. Here, we report on the efficacy of daratumumab 1/ in reducing the histological signs of ABMR, 2/ in reducing the ability of DSA to bind to donor cells in vitro through negativation of flow cytometry crossmatching, 3/ in preferentially being directed towards antibodies sharing epitopes, suggesting that daratumumab may specifically target activated plasma cells, 4/ and when administered as a single dose. This last point suggests, for the first time, that, as for rituximab in auto-immune diseases, the scheme for daratumumab administration could be different for targeting DSA-producing plasma cells than for tumour cells.

Regulatory SVA retrotransposons and classical HLA genotyped-transcripts associated with Parkinson's disease.

Introduction: Parkinson's disease (PD) is a neurodegenerative and polygenic disorder characterised by the progressive loss of neural dopamine and onset of movement disorders. We previously described eight SINE-VNTR-Alu (SVA) retrotransposon-insertion-polymorphisms (RIPs) located and expressed within the Human Leucocyte Antigen (HLA) genomic region of chromosome 6 that modulate the differential co-expression of 71 different genes including the HLA classical class I and class II genes in a Parkinson's Progression Markers Initiative (PPMI) cohort. Aims and methods: In the present study, we (1) reanalysed the PPMI genomic and transcriptomic sequencing data obtained from whole blood of 1521 individuals (867 cases and 654 controls) to infer the genotypes of the transcripts expressed by eight classical HLA class I and class II genes as well as DRA and the DRB3/4/5 haplotypes, and (2) examined the statistical differences between three different PD subgroups (cases) and healthy controls (HC) for the HLA and SVA transcribed genotypes and inferred haplotypes. Results: Significant differences for 57 expressed HLA alleles (21 HLA class I and 36 HLA class II alleles) up to the three-field resolution and four of eight expressed SVA were detected at p<0.05 by the Fisher's exact test within one or other of three different PD subgroups (750 individuals with PD, 57 prodromes, 60 individuals who had scans without evidence of dopamine deficits [SWEDD]), when compared against a group of 654 HCs within the PPMI cohort and when not corrected by the Bonferroni test for multiple comparisons. Fourteen of 20 significant alleles were unique to the PD-HC comparison, whereas 31 of the 57 alleles overlapped between two or more different subgroup comparisons. Only the expressed HLA-DRA*01:01:01 and -DQA1*03:01:01 protective alleles (PD v HC), the -DQA1*03:03:01 risk (HC v Prodrome) or protective allele (PD v Prodrome), the -DRA*01:01:02 and -DRB4*01:03:02 risk alleles (SWEDD v HC), and the NR_SVA_381 present genotype (PD v HC) at a 5% homozygous insertion frequency near HLA-DPA1, were significant (Pc<0.1) after Bonferroni corrections. The homologous NR_SVA_381 insertion significantly decreased the transcription levels of HLA-DPA1 and HLA-DPB1 in the PPMI cohort and its presence as a homozygous genotype is a risk factor (Pc=0.012) for PD. The most frequent NR_SVA_381 insertion haplotype in the PPMI cohort was NR_SVA_381/DPA1*02/DPB1*01 (3.7%). Although HLA C*07/B*07/DRB5*01/DRB1*15/DQB1*06 was the most frequent HLA 5-loci phased-haplotype (n, 76) in the PPMI cohort, the NR_SVA_381 insertion was present in only six of them (8%). Conclusions: These data suggest that expressed SVA and HLA gene alleles in circulating white blood cells are coordinated differentially in the regulation of immune responses and the long-term onset and progression of PD, the mechanisms of which have yet to be elucidated.

Differences in F pocket impact on HLA I genetic associations with autoimmune diabetes.

Introduction: Human leukocyte antigen (HLA) I molecules present antigenic peptides to activate CD8+ T cells. Type 1 Diabetes (T1D) is an auto-immune disease caused by aberrant activation of the CD8+ T cells that destroy insulin-producing pancreatic ß cells. Some HLA I alleles were shown to increase the risk of T1D (T1D-predisposing alleles), while some reduce this risk (T1D-protective alleles). Methods: Here, we compared the T1D-predisposing and T1D-protective allotypes concerning peptide binding, maturation, localization and surface expression and correlated it with their sequences and energetic profiles using experimental and computational methods. Results: T1D-predisposing allotypes had more peptide-bound forms and higher plasma membrane levels than T1D-protective allotypes. This was related to the fact that position 116 within the F pocket was more conserved and made more optimal contacts with the neighboring residues in T1D-predisposing allotypes than in protective allotypes. Conclusion: Our work uncovers that specific polymorphisms in HLA I molecules potentially influence their susceptibility to T1D.

The antibodies 3D12 and 4D12 recognise distinct epitopes and conformations of HLA-E.

The commonly used antibodies 3D12 and 4D12 recognise the human leukocyte antigen E (HLA-E) protein. These antibodies bind distinct epitopes on HLA-E and differ in their ability to bind alleles of the major histocompatibility complex E (MHC-E) proteins of rhesus and cynomolgus macaques. We confirmed that neither antibody cross-reacts with classical HLA alleles, and used hybrids of different MHC-E alleles to map the regions that are critical for their binding. 3D12 recognises a region on the alpha 3 domain, with its specificity for HLA-E resulting from the amino acids present at three key positions (219, 223 and 224) that are unique to HLA-E, while 4D12 binds to the start of the alpha 2 domain, adjacent to the C terminus of the presented peptide. 3D12 staining is increased by incubation of cells at 27°C, and by addition of the canonical signal sequence peptide presented by HLA-E peptide (VL9, VMAPRTLVL). This suggests that 3D12 may bind peptide-free forms of HLA-E, which would be expected to accumulate at the cell surface when cells are incubated at lower temperatures, as well as HLA-E with peptide. Therefore, additional studies are required to determine exactly what forms of HLA-E can be recognised by 3D12. In contrast, while staining with 4D12 was also increased when cells were incubated at 27°C, it was decreased when the VL9 peptide was added. We conclude that 4D12 preferentially binds to peptide-free HLA-E, and, although not suitable for measuring the total cell surface levels of MHC-E, may putatively identify peptide-receptive forms.

Selection, engineering, and in vivo testing of a human leukocyte antigen-independent T-cell receptor recognizing human mesothelin.

BACKGROUND: Canonical α/ß T-cell receptors (TCRs) bind to human leukocyte antigen (HLA) displaying antigenic peptides to elicit T cell-mediated cytotoxicity. TCR-engineered T-cell immunotherapies targeting cancer-specific peptide-HLA complexes (pHLA) are generating exciting clinical responses, but owing to HLA restriction they are only able to target a subset of antigen-positive patients. More recently, evidence has been published indicating that naturally occurring α/ß TCRs can target cell surface proteins other than pHLA, which would address the challenges of HLA restriction. In this proof-of-concept study, we sought to identify and engineer so-called HLA-independent TCRs (HiTs) against the tumor-associated antigen mesothelin. METHODS: Using phage display, we identified a HiT that bound well to mesothelin, which when expressed in primary T cells, caused activation and cytotoxicity. We subsequently engineered this HiT to modulate the T-cell response to varying levels of mesothelin on the cell surface. RESULTS: The isolated HiT shows cytotoxic activity and demonstrates killing of both mesothelin-expressing cell lines and patient-derived xenograft models. Additionally, we demonstrated that HiT-transduced T cells do not require CD4 or CD8 co-receptors and, unlike a TCR fusion construct, are not inhibited by soluble mesothelin. Finally, we showed that HiT-transduced T cells are highly efficacious in vivo, completely eradicating xenografted human solid tumors. CONCLUSION: HiTs can be isolated from fully human TCR-displaying phage libraries against cell surface-expressed antigens. HiTs are able to fully activate primary T cells both in vivo and in vitro. HiTs may enable the efficacy seen with pHLA-targeting TCRs in solid tumors to be translated to cell surface antigens.

Reassessing human MHC-I genetic diversity in T cell studies.

The Major Histocompatibility Complex class I (MHC-I) system plays a vital role in immune responses by presenting antigens to T cells. Allele specific technologies, including recombinant MHC-I technologies, have been extensively used in T cell analyses for COVID-19 patients and are currently used in the development of immunotherapies for cancer. However, the immense diversity of MHC-I alleles presents challenges. The genetic diversity serves as the foundation of personalized medicine, yet it also poses a potential risk of exacerbating healthcare disparities based on MHC-I alleles. To assess potential biases, we analysed (pre)clinical publications focusing on COVID-19 studies and T cell receptor (TCR)-based clinical trials. Our findings reveal an underrepresentation of MHC-I alleles associated with Asian, Australian, and African descent. Ensuring diverse representation is vital for advancing personalized medicine and global healthcare equity, transcending genetic diversity. Addressing this disparity is essential to unlock the full potential of T cells for enhancing diagnosis and treatment across all individuals.

Generation of Highly Functional Hepatocyte-like Organoids from Human Adipose-Derived Mesenchymal Stem Cells Cultured with Endothelial Cells.

Previously, we successfully established a highly functional, three-dimensional hepatocyte-like cell (3D-HLC) model from adipose-derived mesenchymal stem cells (ADSCs) via a three-step differentiation protocol. The aim of the present study was to investigate whether generating hepatocyte-like organoids (H-organoids) by adding endothelial cells further improved the liver-like functionality of 3D-HLCs and to assess H-organoids' immunogenicity properties. Genes representing liver maturation and function were detected by quantitative reverse transcription-PCR analysis. The expression of hepatic maturation proteins was measured using immunofluorescence staining. Cytochrome P (CYP)450 metabolism activity and ammonia metabolism tests were used to assess liver function. H-organoids were successfully established by adding human umbilical vein endothelial cells at the beginning of the definitive endoderm stage in our 3D differentiation protocol. The gene expression of alpha-1 antitrypsin, carbamoyl-phosphate synthase 1, and apolipoprotein E, which represent liver maturation state and function, was higher in H-organoids than non-organoid 3D-HLCs. H-organoids possessed higher CYP3A4 metabolism activity and comparable ammonia metabolism capacity than 3D-HLCs. Moreover, although H-organoids expressed human leukocyte antigen class I, they expressed little human leukocyte antigen class II, cluster of differentiation (CD)40, CD80, CD86, and programmed cell death ligand 1, suggesting their immunogenicity properties were not significantly upregulated during differentiation from ADSCs. In conclusion, we successfully established an H-organoid model with higher liver-like functionality than previously established 3D-HLCs and comparable immunogenicity to ADSCs.

HLA-class II restricted TCR targeting human papillomavirus type 18 E7 induces solid tumor remission in mice.

T cell receptor (TCR)-engineered T cell therapy is a promising potential treatment for solid tumors, with preliminary efficacy demonstrated in clinical trials. However, obtaining clinically effective TCR molecules remains a major challenge. We have developed a strategy for cloning tumor-specific TCRs from long-term surviving patients who have responded to immunotherapy. Here, we report the identification of a TCR (10F04), which is human leukocyte antigen (HLA)-DRA/DRB1*09:01 restricted and human papillomavirus type 18 (HPV18) E784-98 specific, from a multiple antigens stimulating cellular therapy (MASCT) benefited metastatic cervical cancer patient. Upon transduction into human T cells, the 10F04 TCR demonstrated robust antitumor activity in both in vitro and in vivo models. Notably, the TCR effectively redirected both CD4+ and CD8+ T cells to specifically recognize tumor cells and induced multiple cytokine secretion along with durable antitumor activity and outstanding safety profiles. As a result, this TCR is currently being investigated in a phase I clinical trial for treating HPV18-positive cancers. This study provides an approach for developing safe and effective TCR-T therapies, while underscoring the potential of HLA class II-restricted TCR-T therapy as a cancer treatment.

Tracking Circulating HLA-Specific IgG-Producing Memory B Cells with the B-Cell ImmunoSpot Assay.

Donor-specific antibodies (DSA) against human leukocyte antigen (HLA) molecules are a major risk factor for rejection of transplanted organs (in antibody-mediated rejection [ABMR]), particularly in patients who have prior sensitization or receive insufficient immunosuppression through minimization or noncompliance. These DSA are measured routinely in the serum of patients prior to transplantation mainly using bead-based technologies or cell-based assays. However, the absence of detectable serum DSA does not always reflect the absence of sensitization or histologically defined ABMR, and so it has been proposed that the detection and measurement of memory B cells capable of secreting antibodies against donor HLA antigens could be carried out using B-cell ImmunoSpot, to better inform the degree of immune sensitization of transplant patients prior to as well as after transplantation. Such an assay is described here.

Routine screening for HLA Antibodies in Heart Transplant patients-Does it affect clinical decision making?

BACKGROUND: We aimed to assess outcomes in patients with and without donor specific antibodies (DSA) and to evaluate the relationship between DSA presence and graft function, cardiac allograft vasculopathy (CAV), and mortality. METHODS: The study population comprises 193 consecutive long-term heart transplanted (HTx) patients who underwent DSA surveillance between 2016 and 2022. The patients were prospectively screened for CAV through serial coronary angiograms, graft function impairment through serial echocardiograms, and cardiac biomarkers. The patients were followed from the first DSA measurement until death, 5 years follow-up or right censuring on the 30th of June 2023. RESULTS: DSAs were detected in 50 patients using a cut-off at MFI ≥1000 and 45 patients using a cut-off at ≥2000 MFI. The median time since HTx was 9.0 years [3.0-14.4]. DSA positive patients had poorer graft function and higher values of NT-proBNP and troponin T, and more prevalent CAV than DSA negative patients. In total, 25 patients underwent endomyocardial biopsies due to DSA presence while another eight patients underwent endomyocardial biopsies for other reasons. Histological antibody mediated rejection (AMR) signs were seen in three biopsies. During a median follow-up of five years [4.7-5], a total of 41 patients died. Mortality rates did not differ between DSA positive and DSA negative patients (HR 1.2, 95% CI .6-2.4). DSA positive patients were more likely to experience CAV progression than DSA negative patients (HR 2.7, 95% CI 1.5-4.8) CONCLUSIONS: Routine screening reveals DSA in approximately 25% of long-term HTx patients but is rarely related to histopathological AMR signs. DSA presence was associated with poorer graft function and more prevalent and progressive CAV. However, DSA positive patients had similar survival rates to DSA negative patients.

Two-field resolution on-call HLA typing for deceased donors using nanopore sequencing.

The current practice of HLA genotyping in deceased donors poses challenges due to limited resolution within time constraints. Nevertheless, the assessment of compatibility between anti-HLA sensitized recipients and mismatched donors remains a critical medical need, particularly when dealing with allele-specific (second field genotyping level) donor-specific antibodies. In this study, we present a customized protocol based on the NanoTYPE® HLA typing kit, employing the MinION® sequencer, which enables rapid HLA typing of deceased donors within a short timeframe of 3.75 h on average at a three-field resolution with almost no residual ambiguities. Through a prospective real-time analysis of HLA typing in 18 donors, we demonstrated the efficacy and precision of our nanopore-based method in comparison to the conventional approach and without delaying organ allocation. Indeed, this duration was consistent with the deceased donor organ donation procedure leading to organ allocation via the French Biomedicine Agency. The improved resolution achieved with our protocol enhances the security of organ allocation, particularly benefiting highly sensitized recipients who often present intricate HLA antibody profiles. By overcoming technical challenges and providing comprehensive genotyping data, this approach holds the potential to significantly impact deceased donor HLA genotyping, thereby facilitating optimal organ allocation strategies.

Protocol for structural modeling of antibody to human leukocyte antigen interaction using discovery and targeted cross-linking mass spectrometry.

Cross-linking mass spectrometry (XL-MS) provides low-resolution structural information to model protein structures. Here, we present a protocol to identify cross-links of purified antibody binding to purified human leukocyte antigen (HLA). We describe steps for using a discovery-based XL-MS approach followed by a targeted XL-MS approach. We then detail procedures for using the identified cross-links with other structural data for molecular docking of the antibody to HLA. This protocol has applications for modeling the interacting structure of purified antibody to antigen. For complete details on the use and execution of this protocol, please refer to Ser et al.1.

Human Leukocyte Antigen Markers for Distinguishing Pustular Psoriasis and Adult-Onset Immunodeficiency with Pustular Reaction.

Pustular skin diseases, with pustular psoriasis (PP) being the prototype, are immune-mediated diseases characterized by the presence of multiple pustules, resulting from neutrophil accumulation in the layer of epidermis. Sterile skin pustular eruption, like PP, is also observed in 20-30% of patients with adult-onset immunodeficiency syndrome (AOID) and anti-interferon γ autoantibodies (IFN-γ), leading to challenges in classification and diagnosis. While the mechanism underlying this similar phenotype remains unknown, genetic factors in relation to the immune system are suspected of playing an important role. Here, the association between human leukocyte antigen (HLA) genes, which play essential roles in antigen presentation, contributing to immune response, and the presence of skin pustules in AOID and PP was revealed. HLA genotyping of 41 patients from multiple centers in Thailand who presented with multiple sterile skin pustules (17 AOID patients and 24 PP patients) was conducted using a next-generation-sequencing-based approach. In comparison to healthy controls, HLA-B*13:01 (OR = 3.825, 95%CI: 2.08-7.035), C*03:04 (OR = 3.665, 95%CI: 2.102-6.39), and DQB1*05:02 (OR = 2.134, 95%CI: 1.326-3.434) were significantly associated with the group of aforementioned conditions having sterile cutaneous pustules, suggesting a common genetic-related mechanism. We found that DPB1*05:01 (OR = 3.851, p = 0.008) and DRB1*15:02 (OR = 3.195, p = 0.033) have a significant association with pustular reaction in AOID patients, with PP patients used as a control. A variant in the DRB1 gene, rs17885482 (OR = 9.073, p = 0.005), was observed to be a risk factor for PP when using AOID patients who had pustular reactions as a control group. DPB1*05:01 and DRB1*15:02 alleles, as well as the rs17885482 variant in the DRB1 gene, were proposed as novel biomarkers to differentiate PP and AOID patients who first present with multiple sterile skin pustules without known documented underlying conditions.

Mass Spectrometry-Based Immunopeptidomics of Peptides Presented on Human Leukocyte Antigen Proteins.

Human leukocyte antigen (HLA) proteins are a group of glycoproteins that are expressed at the cell surface, where they present peptides to T cells through physical interactions with T-cell receptors (TCRs). Hence, characterizing the set of peptides presented by HLA proteins, referred to hereafter as the immunopeptidome, is fundamental for neoantigen identification, immunotherapy, and vaccine development. As a result, different methods have been used over the years to identify peptides presented by HLA proteins, including competition assays, peptide microarrays, and yeast display systems. Nonetheless, over the last decade, mass spectrometry-based immunopeptidomics (MS-immunopeptidomics) has emerged as the gold-standard method for identifying peptides presented by HLA proteins. MS-immunopeptidomics enables the direct identification of the immunopeptidome in different tissues and cell types in different physiological and pathological states, for example, solid tumors or virally infected cells. Despite its advantages, it is still an experimentally and computationally challenging technique with different aspects that need to be considered before planning an MS-immunopeptidomics experiment, while conducting the experiment and with analyzing and interpreting the results. Hence, we aim in this chapter to provide an overview of this method and discuss different practical considerations at different stages starting from sample collection until data analysis. These points should aid different groups aiming at utilizing MS-immunopeptidomics, as well as, identifying future research directions to improve the method.

Deep Learning-Assisted Analysis of Immunopeptidomics Data.

Liquid chromatography-coupled mass spectrometry (LC-MS/MS) is the primary method to obtain direct evidence for the presentation of disease- or patient-specific human leukocyte antigen (HLA). However, compared to the analysis of tryptic peptides in proteomics, the analysis of HLA peptides still poses computational and statistical challenges. Recently, fragment ion intensity-based matching scores assessing the similarity between predicted and observed spectra were shown to substantially increase the number of confidently identified peptides, particularly in use cases where non-tryptic peptides are analyzed. In this chapter, we describe in detail three procedures on how to benefit from state-of-the-art deep learning models to analyze and validate single spectra, single measurements, and multiple measurements in mass spectrometry-based immunopeptidomics. For this, we explain how to use the Universal Spectrum Explorer (USE), online Oktoberfest, and offline Oktoberfest. For intensity-based scoring, Oktoberfest uses fragment ion intensity and retention time predictions from the deep learning framework Prosit, a deep neural network trained on a very large number of synthetic peptides and tandem mass spectra generated within the ProteomeTools project. The examples shown highlight how deep learning-assisted analysis can increase the number of identified HLA peptides, facilitate the discovery of confidently identified neo-epitopes, or provide assistance in the assessment of the presence of cryptic peptides, such as spliced peptides.

Platelet transfusions in haploidentical haematopoietic stem cell allograft candidates: Protecting HLA-A and HLA-B antigens through eplet analysis.

In patients awaiting an allogeneic haematopoietic stem cell transplantation, platelet transfusion is a risk factor for anti-HLA class I immunization because the resulting donor-specific antibodies complicate the allograft process. The objective of the present study was to determine the feasibility of a novel eplet-based strategy for identifying HLA class I mismatches between potential donors and the recipient when pre-allograft platelet transfusions were required. We included 114 recipient/haploidentical relative pairs. For each pair, we entered HLA-class I typing data into the HLA Eplet Mismatch calculator, defined the list of mismatched eplets (for the recipient versus donor direction) and thus identified the shared HLAs to be avoided. Using this list of HLAs, we defined the theoretical availability of platelet components (PCs) by calculating the virtual panel-reactive antibody (vPRA). We also determined the number of PCs actually available in France by querying the regional transfusion centre's database. The mean ± standard deviation number of highly/moderately exposed eplets to be avoided in platelet transfusions was 5.8 ± 3.3, which led to the prohibition of 38.5 ± 2 HLAs-A and -B. Taking into account the mismatched antigens and the eplet load, the mean ± standard deviation theoretical availability of PCs (according to the vPRA) was respectively 34.49% ± 1.95% for HLA-A and 80% ± 2.3% for HLA-B. A vPRA value below 94.9% for highly or moderately exposed eplets would predict that 10 PCs were actually available nationally. Although epitope protection of HLA molecules is feasible, it significantly restricts the choice of PCs.

[Challenges and solutions in current human leukocyte antigen confirmatory typing of hematopoietic stem cell transplantation].

The impact of human leukocyte antigen (HLA) on hematopoietic stem cell transplantation (HSCT) necessitates high precision in HLA genotyping. Confirmatory typing for patients and their related or unrelated donors before HSCT is critical. This study seeks to standardize HLA confirmatory typing in laboratories by examining the current state of HLA genotyping in the country, building upon the National Standards and Industrial Standards for HLA, and highlighting the significance of confirmatory typing for patients and potential donors prior to HSCT. A retrospective analysis over a decade reveals initial typing errors, indicating potential issues and critical considerations in pre-analytical, analytical, and post-analytical stages. Problems are attributed to three main causes: (1) random human errors, including technical mistakes, sample mix-up, and transcription inaccuracies; (2) limitations of technical methods, such as the varied sequence ranges between confirmatory and initial typing; (3) patient factors, involving high tumor burden, the influence of certain drugs on HLA genotyping results, and the second transplantation. Solutions are proposed for these problems, along with recommendations to standardize HLA confirmatory typing.