Recipient Human Leukocyte Antigen Research Articles

Calculated PRA and PIRCHE Algorithm in Kidney Transplant Recipients

Abstract Introduction Calculated PRA testing in kidney transplantation has revolutionized the field by enabling a more accurate assessment of compatibility and risk prediction for AMR. On the other hand, The PIRCHE algorithm aims to identify the potentially immunogenic human leukocyte antigens (HLA) epitopes on the donor graft that are recognized by the recipient's HLA antibodies. The aim of this analysis was to compare the actual immunological risk at the time of transplantation with the hypothetical risk that would be determined by cPRA and PIRCHE. Another aim was to compare this hypothetical risk also in the context of the development of DSA and the protocol graft biopsy at month 3. Material and methods In a group of 20 patients we recorded the real immunological risk determined at the time of transplantation according to the induction immunosuppression protocol of the Transplant-Nephrology Department of the University Hospital Martin and compared it with the hypothetical calculated risk according to cPRA and PIRCHE. We then compared the hypothetical risk with the protocol biopsy result and with any evidence of donor-specific antibodies at month 3 after the kidney transplantation. Results Under cPRA, the two patients we assessed as medium risk in real time would be classified as low risk. Both of these patients did not have DSA identified at month 3 and did not have rejection changes in the protocol biopsy. According to PIRCHE, the immunological risk would change from moderate to low in two patients, and even from very high to low in one patient. In none of these patients did we subsequently observe DSA formation at month 3 post-transplantation, and also all three protocol biopsies were free of rejection changes in these patients. Conclusion In our analysis we confirmed the importance of both immunological and non-immunological parameters for determining risk at the time of transplantation. For using PIRCHE score larger studies are required to confirm this strategy.

Abstract 3855: Kinetics of neoantigen-specific T cells in post-transplant relapse

Abstract Introduction: Graft-versus-leukemia effect (GVL) underpins the curative mechanism of allogeneic stem cell transplantation (alloSCT) for acute leukemias. Donor-derived T cells can recognize various antigens, including human leukocyte antigen (HLA), minor-histocompatibility antigens (miHA), over-expressed antigens, or neoantigens derived from somatic mutations of leukemia. However, the role of neoantigens has not been fully investigated in GVL. Here, we aimed to predict neoantigens and identify neoantigen-reactive T cells using samples after alloSCT. Materials: Leukemia blasts were purified from relapsed samples. Recipient saliva or T cells from pre-transplant peripheral blood (PB) were used as a recipient germline control, while donor monocyte or CD34 cells were used as donor controls. DNA/RNA isolated from these specimens were analyzed for whole exome sequencing (WES) paired with RNAseq. Somatic mutations were called using blasts and recipient germline controls by mutect and mpileup and annotation with SnpEff. Somatic mutations with variant allele frequency >20% were screened for neoantigen prediction bound to recipient HLA (IC50 < 500nM) by pVAC-seq. We also genotyped 73 SNPs associated with publicly known miHAs. Serial PB were stained for HLA-A*02:01 tetramers loaded with neoantigens or CMVpp65. T cells were stimulated with neoantigens for 10 days and tested for cytokine production in responses to target or control peptides. Results: We screened neoantigens in 8 patients relapsing after alloSCT (7 acute myeloid leukemia and 1 acute lymphoblastic leukemia) and their donors (4 matched siblings, 1 matched unrelated, 3 haploidentical). In 7 subjects, WES/RNAseq showed an average of 273 somatic mutations per patient (range 108- 609). In one subject, targeted next-generation sequencing was used to detect 2 somatic mutations. Among these mutations, seven out of eight subjects (87.5%) had potential neoantigen candidates, with a median number of 9 antigens per subject. In contrast, only 2 subjects (25%) had potential miHA. UPN8, a responder to donor lymphocyte infusion (DLI), showed dominant CMVpp65-specific T cells at the time of relapse and emergence of TP53- (neoantigen) or HA-2- (miHA) specific T cells after relapse. HA-2-specific T cells upregulated PD-1 expression at the time of graft-versus-host disease (GVHD), indicating activation of these miHA-specific T cells during GVHD. In two subjects (UPN3 and UPN8) who achieved long-term remission after DLI, CD8 T cells specific to neoantigens were detectable by IFN-γ/CD107a production in reaction to mutant peptides (SDE2.pK123X or TP53.pR248W) from post-relapse samples. Discussion: Our study showed the feasibility of in-silico neoantigens prediction and neoantigen-specific T-cell detection from a subject who developed relapse after alloSCT. Further investigation is needed to test if neoepitope burden and miHA disparity could correlate with transplant outcomes. Citation Format: Biswas Neupane, Jui-En Ray Lee, Kedwin Ventura, Kayla Parr, Kevin Quann, Sawa Ito. Kinetics of neoantigen-specific T cells in post-transplant relapse [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3855.

Immunology Status of Patients During Kidney Transplant.

The immunology status of a patient has a crucial role in kidney transplant. We investigated the effectiveness of a desensitization protocol, guided by the immunology status of patients, for kidney transplant candidates. Antibody screening for human leukocyte antigens was conducted with the Luminex single-antigen microsphere bead assay method for 34 patients from June 2021 to June 2022. Donor human leukocyte antigen genotypes at 8 loci (A*, B*, С*, DRB1*, DQA1*, DQB1*, DPA1*, and DPB1*) were determined, to correlate the specificities of recipient human leukocyte antigen antibodies with donor antigens and identify unacceptable donor antigen combinations. Specialized immunology studies measured panel reactive antibody levels and human leukocyte antigen class I and class II antibodies. A crossmatch compatibility test using complementdependent cytotoxicity was conducted. Of the 34 patients, 10 completed all 3 stages of the desensitization therapy. Most patients experienced decreased sensitization to human leukocyte antigen class I and class II antibodies. Two patients achieved complete clearance of A1 and DQ5 antibodies, respectively, whereas 1 patient exhibited an increase in donor-specific antibody mean fluorescence intensity. Prior to desensitization therapy, the crossmatch compatibility test yielded positive results with T and B lymphocytes. After completing the therapy, the crossmatch test showed negative results in 4 cases with T lymphocytes and positive results with B lymphocytes. Plasmapheresis sessions effectively reduced circulating antibodies. However, the combination of rituximab and plasmapheresis alone did not achieve a negative crossmatch test required for kidney transplant. It is crucial to assess the reduction of donor-specific antibody quantity, considering both the percentage and the mean fluorescence intensity. To avoid false-positive results in crossmatch analysis, drug half-life must be considered. Laboratories should have various crossmatch techniques, such as flow cytometry and single-antigen microsphere bead assay technology, available for research and urgent cases that require crossmatch analysis.

HLA Typing and Donor-Specific Antibody Screening in Kidney Transplantation: Bridging the Past to the Future

Human leukocyte antigens (HLA) are unique proteins expressed on the surface of human cells, playing a pivotal role in the immune system, particularly in the contexts of infection, cancer, and transplantation. The widespread adoption of HLA typing methods has become an essential component in assessing donor-recipient compatibility, a crucial limiting factor in solid organ transplantation. In general, the greater the disparity between a donor's and recipient's HLA types, the higher the likelihood of provoking an alloimmune response, which frequently results in alloimmune graft rejection. With significant advancements in organ transplantation techniques, immunosuppressive medications, and surgical procedures, attention has increasingly turned toward understanding and managing humoral rejection processes. Pre-transplant antibody screening plays a critical role in identifying individuals with elevated levels of antibodies against potential donor antigens. This screening aids in risk assessment and planning to mitigate the risk of antibody-mediated rejection (AbMR). Several methods are available for assessing circulating antigen-specific antibodies and HLA tissue typing, including cell-based assays like serological assays, complement-dependent cytotoxicity, and flow cytometry. However, non-cell-based approaches, such as molecular methods, HLA imputation techniques and high-throughput HLA-matchmaker assays have gained significant popularity due to their ability to provide higher resolution and robust donor-recipient matching. Despite the advancements in precision and sensitivity observed in HLA cutting-edge technologies, numerous challenges still persist. These challenges involve complexities linked to allelic ambiguities, the differentiation of closely related alleles, and the ongoing effort to establish a standardized HLA testing methodology across diverse laboratories. Additionally, correlating the HLA crossmatch results with the clinical outcomes for transplant donors poses another important aspect that warrants attention and requires expert analysis. In this review, we will enumerate the different methods of HLA typing and DSA screening and discuss the unmet needs and future directions for HLA typing methods.

The Rule of Rescue in the Era of Precision Medicine, HLA Eplet Matching, and Organ Allocation

Precision medicine can put clinicians in a position where they must act more as resource allocators than their traditional role as patient advocates. In the allocation of transplantable organs and tissues, the use of eplet matching will enhance precision medicine but, in doing so, generate a tension with the present reliance on rule of rescue and justice-based factors for allocations. Matching donor and recipient human leukocyte antigens (HLA) is shown to benefit virtually all types of solid organ transplants yet, until recently, HLA-matching has not been practical and was shown to contribute to ethnic/racial disparities in organ allocation. Recent advances using eplets from the HLA molecule has renewed the promise of such matching for predicting patient outcomes. The rule of rescue in organ allocation reflects a combination of ethical, policy, and legal imperatives. However, the rule of rescue can impede the allocation strategies adopted by professional medical associations and the optimal use of scarce transplant resources. While eplet-matching seeks to improve outcomes, it may potentially frustrate current ethics-motivated initiatives, established patient-practitioner relationships, and functional conventions in the allocation of medical resources such as organ and tissue transplants. Eplet-matching allocation schemes need to be carefully and collaboratively designed with clear, fair and equitable guidelines that complement functional conventions and maintain public trust.

Assessment of donor compatibility in human solid organ transplantation and evaluation of allogeneic responses using a novel humanized mouse model.

Abstract The end result of solid organ transplantation is dictated by selection of a well-matched donor, leading to allograft survival. An allogeneic immune response is the main immunological barrier for successful organ transplantation. Donor and recipient human leukocyte antigen (HLA) mismatching results in poor graft acceptance, inflammation and rejection. The current evaluations for donor-recipient HLA incompatibility does not provide adequate information on the immunogenicity of individual HLA mismatches and impact of non-HLA-related alloantigens, especially in vivo. Here we demonstrate a novel method for analysis of alloimmune responsiveness between donor and recipient in vivoby introducing a humanized mouse model. Using molecular, cellular, and genomic analyses, we demonstrated that a recipient’s personalized humanized mouse provided the most sensitive assessment of allogeneic responsiveness to potential donors. In our study, HLA typing and mixed lymphocyte reaction (MLR) for assessment of allogeneic response was indistinguishable between 2 related donors of the recipient. Contrastingly in recipient’s humanized mouse model, the donor selected by HLA typing induced the strongest allogeneic response with increased infiltration of cytotoxic GzmB +CD8 +T cells. Moreover, the same donor induced upregulation of genes involved in the allograft rejection identified by transcriptomic analysis of graft infiltrating CD45 +cells. Humanized mouse model determined the lowest degree of recipient-donor alloimmune response, allowing for better selection of donor and minimized immunological risk of allograft rejection in transplantation. This approach can be used to evaluate alloresponses in cell based therapies as well. This study was supported by research funding from the Carlos and Marguerite Mason Trust, and by U.S. National Institutes of Health, National Cancer Institute Grant CA 172230

The clinical impact of donor against recipient HLA one way mismatch on the occurrence of graft versus host disease in liver transplantation

Graft versus host disease (GVHD) after liver transplantation (LT) is a rare, fatal disease. This study aimed to evaluate the risk factors of GVHD after LT including the human leukocyte antigen (HLA) donor-recipient relationship after LT. LT recipients, who underwent HLA typing together with donors, were included in the study. The donor against recipient (D → R) one-way mismatch of HLA loci was evaluated. HLA relationships, along with basic characteristics, were analyzed as variable factors of GVHD, graft survival, and patient survival. A total of 994 living donor LT (LDLT) and 393 deceased donor LT (DDLT) patients were included. Nine patients had suffered GVHD, four LDLT with D → R one-way at three loci, one LDLT without D → R one-way at three loci, and four DDLT without D → R one-way at three loci. Four (57.1%) of seven LDLT patients, with D → R one-way mismatch at three loci, developed GVHD. D → R one-way mismatch at three loci was related to high GVHD incidence (HR 787, p < 0.001, multivariate). D → R one-way mismatch at three loci was related to graft failure and patient death (HR 9.90, p = 0.020 and HR 12.8, p < 0.001, respectively, multivariate). Only one GVHD without D → R one-way mismatch at three loci, survived despite receiving multiple modalities including tumor necrosis factor-alpha inhibitors. D → R one-way mismatch at three loci was significantly related to GVHD incidence after LT.

Generation of hypoimmunogenic induced pluripotent stem cells by CRISPR-Cas9 system and detailed evaluation for clinical application

In order to expand the promise of regenerative medicine using allogeneic induced pluripotent stem cells (iPSCs), precise and efficient genome editing of human leukocyte antigen (HLA) genes would be advantageous to minimize the immune rejection caused by mismatches of HLA type. However, clinical-grade genome editing of multiple HLA genes in human iPSC lines remains unexplored. Here, we optimized the protocol for good manufacturing practice (GMP)-compatible CRISPR-Cas9 genome editing to deplete the three gene locus (HLA-A, HLA-B, and CIITA genes) simultaneously in HLA homozygous iPSCs. The use of HLA homozygous iPSCs has one main advantage over heterozygous iPSCs for inducing biallelic knockout by a single gRNA. RNA-seq and flow cytometry analyses confirmed the successful depletion of HLAs, and lineage-specific differentiation into cardiomyocytes was verified. We also confirmed that the pluripotency of genome-edited iPSCs was successfully maintained by the three germ layers of differentiation. Moreover, whole-genome sequencing, karyotyping, and optical genome mapping analyses revealed no evident genomic abnormalities detected in some clones, whereas unexpected copy number losses, chromosomal translocations, and complex genomic rearrangements were observed in other clones. Our results indicate the importance of multidimensional analyses to ensure the safety and quality of the genome-edited cells. The manufacturing and assessment pipelines presented here will be the basis for clinical-grade genome editing of iPSCs.

Donor-recipient human leukocyte antigen A mismatching is associated with hepatic artery thrombosis, sepsis, graft loss, and reduced survival after liver transplant.

Human leukocyte antigen (HLA) matching is not routinely performed for liver transplantation as there is no consistent evidence of benefit; however, the impact of HLA mismatching remains uncertain. We explored the effect of class I and II HLA mismatching on graft failure and mortality. A total of 1042 liver transplants performed at a single center between 1999 and 2016 with available HLA typing data were included. The median follow‐up period was 9.38 years (interquartile range 4.9–14) and 350/1042 (33.6%) transplants resulted in graft loss and 280/1042 (26.9%) in death. Graft loss and mortality were not associated with the overall number of mismatches at HLA‐A, HLA‐B, HLA‐C, HLA‐DR, and HLA‐DQ loci. However, graft failure and mortality were both increased in HLA mismatching on graft failure and mortality the presence of one (p = 0.004 and p = 0.01, respectively) and two (p = 0.01 and p = 0.04, respectively) HLA‐A mismatches. Elevated hazard ratios for graft failure and death were observed with HLA‐A mismatches in univariate and multivariate Cox proportional hazard models. Excess graft loss with HLA‐A mismatch (138/940 [14.7%] mismatched compared with 6/102 [5.9%] matched transplants) occurred within the first year following transplantation (odds ratio 2.75; p = 0.02). Strikingly, transplants performed at a single all grafts lost due to hepatic artery thrombosis were in HLA‐A–mismatched transplants (31/940 vs. 0/102), as were those lost due to sepsis (35/940 vs. 0/102). In conclusion, HLA‐A mismatching was associated with increased graft loss and mortality. The poorer outcome for the HLA‐mismatched group was due to hepatic artery thrombosis and sepsis, and these complications occurred exclusively with HLA‐A–mismatched transplants. These data suggest that HLA‐A mismatching is important for outcomes following liver transplant. Therefore, knowledge of HLA‐A matching status may potentially allow for enhanced surveillance, clinical interventions in high‐risk transplants or stratified HLA‐A matching in high‐risk recipients.

Human leukocyte antigen epitope mismatch loads and the development of de novo donor-specific antibodies in cardiothoracic organ transplantation.

De novo donor-specific human leucocyte antigen (HLA) antibodies (dnDSA) are associated with increased risk of rejection and mortality in solid organ transplantation. Such dnDSA is produced in some recipients upon allorecognition of mismatched HLA post-transplant. HLA matching is not currently considered in the allocation of deceased donor hearts and lungs and pre-transplant immunological risk stratification is based entirely on the mean fluorescence intensity (MFI) of circulating donor-directed HLA antibodies. HLA epitope-based matching tools predict B-cell or T-cell HLA epitopes that are present in the donor's HLA but absent in the recipient's HLA. We hypothesized that patients with higher epitope mismatch loads would be at increased risk of dnDSA development. We retrospectively analysed 73 heart and/or lung transplant recipients who were tested for DSA between 2015 and 2020. HLAMatchmaker, PIRCHE-II and HLA epitope mismatch algorithm (HLA-EMMA) were used to calculate eplet mismatch (EpMM) loads, T-cell epitope mismatch (TEpMM) loads and solvent accessible amino acid mismatch (SAMM) loads, respectively. Multivariate analyses showed that HLA-EMMA was the only tool with a significant association between the total score for all HLA loci and dnDSA production [odds ratio (OR) 1.021, 95% confidence interval (CI) 1.003-1.042, p=.0225] though this increased risk was marginal. The majority of dnDSA were directed against HLA-DQ and patients with higher HLA-DQ TEpMM loads (OR=1.008, CI=1.002-1.014, p=.007), and HLA-DR+DQ SAMM loads (OR=1.035, CI=1.010-1.064, p=.0077) were most at risk of producing dnDSA. We also showed that patients with a risk epitope within the HLA molecule encoded for by HLA-DQA1*05 + HLA-DQB1*02/03:01 were significantly more likely to produce dnDSA. The use of HLA epitope-based matching tools could be used for cardiothoracic transplant risk stratification to enable early intervention and monitoring of patients at increased risk of producing dnDSA.

Human leukocyte antigen eplet mismatching is associated with increased risk of graft loss and rejection after pediatric heart transplant.

While mismatching between donor and recipient human leukocyte antigen (HLA) alleles has been associated with increased graft loss in pediatric heart recipients, it is actually the surface amino acid structures, termed eplets, which determine the antigenicity of each HLA molecule. We hypothesized that HLA eplet mismatch analysis is a better predictor of adverse outcomes after pediatric heart transplant than conventional allele mismatch comparison. A retrospective review of the Pediatric Heart Transplant Society database identified pediatric heart recipients (<18years at listing) with complete donor and recipient HLA typing (A, B, and DR). Imputed high-resolution HLA genotypes were entered into HLAMatchmaker software which then calculated the number of eplet mismatches between each donor-recipient pair. Multivariable Cox regression analysis was used to examine associations between allele or eplet mismatching and adverse outcomes. Compared to those with <20 HLA class I eplet mismatches, recipients with 20 or more HLA class I eplet mismatches had an increased risk of graft loss (HR 1.46 [1.01-2.12], p=.049). HLA class I eplet mismatching was also associated with rejection (>20mismatches: HR 1.30 [1.03-1.65], p=.030), while HLA class II eplet mismatching was associated with specified antibody-mediated rejection (10-20mismatches: HR 1.57 [1.06-2.34], p=.025; >20mismatches: HR 3.14 [1.72-5.71], p<.001). Neither HLA class I nor class II allele mismatching was significantly associated with graft loss or rejection. Eplet mismatch analysis was more predictive of adverse post-transplant outcomes (including graft loss and rejection) than allele mismatch comparison. Further study, including prospective high-resolution HLA typing, is warranted.

Precision medicine in transplantation and hemodialysis.

In kidney transplantation, precision medicine has already entered clinical practice. Donor and recipient human leucocyte antigen (HLA) regions are genotyped in two class 1 and usually three class 2 loci, and the individual degree of sensitization against alloimmune antigens is evaluated by the detection of anti-HLA donor-specific antibodies. Recently, the contribution of non-HLA mismatches to outcomes such as acute T- and B-cell-mediated rejection and even long-term graft survival was described. Tracking of specific alloimmune T- and B-cell clones by next generation sequencing and refinement of the immunogenicity of allo-epitopes specifically in the interaction with HLA and T- and B-cell receptors may further support individualized therapy. Although the choices of maintenance immunosuppression are rather limited, individualization can be accomplished by adjustment of dosing based on these risk predictors. Finally, supplementing histopathology by a transcriptomics analysis allows for a biological interpretation of the histological findings and avoids interobserver variability of results. In contrast to transplantation, the prescription of hemodialysis therapy is far from precise. Guidelines do not consider modifications by age, diet or many comorbid conditions. Patients with residual kidney function routinely receive the same treatment as those without. A major barrier hitherto is the definition of ‘adequate’ treatment based on urea removal. Kt/Vurea and related parameters neither reflect the severity of uremic symptoms nor predict long-term outcomes. Urea is poorly representative for numerous other compounds that accumulate in the body when the kidneys fail, yet clinicians prescribe treatment based on its measurement. Modern technology has provided the means to identify other solutes responsible for specific features of uremic illness and their measurement will be a necessary step in moving beyond the standardized prescription of hemodialysis.

Humanized Mouse Model as a Novel Approach in the Assessment of Human Allogeneic Responses in Organ Transplantation.

The outcome of organ transplantation is largely dictated by selection of a well-matched donor, which results in less chance of graft rejection. An allogeneic immune response is the main immunological barrier for successful organ transplantation. Donor and recipient human leukocyte antigen (HLA) mismatching diminishes outcomes after solid organ transplantation. The current evaluation of HLA incompatibility does not provide information on the immunogenicity of individual HLA mismatches and impact of non-HLA-related alloantigens, especially in vivo. Here we demonstrate a new method for analysis of alloimmune responsiveness between donor and recipient in vivo by introducing a humanized mouse model. Using molecular, cellular, and genomic analyses, we demonstrated that a recipient’s personalized humanized mouse provided the most sensitive assessment of allogeneic responsiveness to potential donors. In our study, HLA typing provided a better recipient-donor match for one donor among two related donors. In contrast, assessment of an allogeneic response by mixed lymphocyte reaction (MLR) was indistinguishable between these donors. We determined that, in the recipient’s humanized mouse model, the donor selected by HLA typing induced the strongest allogeneic response with markedly increased allograft rejection markers, including activated cytotoxic Granzyme B-expressing CD8+ T cells. Moreover, the same donor induced stronger upregulation of genes involved in the allograft rejection pathway as determined by transcriptome analysis of isolated human CD45+cells. Thus, the humanized mouse model determined the lowest degree of recipient-donor alloimmune response, allowing for better selection of donor and minimized immunological risk of allograft rejection in organ transplantation. In addition, this approach could be used to evaluate the level of alloresponse in allogeneic cell-based therapies that include cell products derived from pluripotent embryonic stem cells or adult stem cells, both undifferentiated and differentiated, all of which will produce allogeneic immune responses.

HLA DR Genome Editing with TALENs in Human iPSCs Produced Immune-Tolerant Dendritic Cells.

Although human induced pluripotent stem cells (iPSCs) can serve as a universal cell source for regenerative medicine, the use of iPSCs in clinical applications is limited by prohibitive costs and prolonged generation time. Moreover, allogeneic iPSC transplantation requires preclusion of mismatches between the donor and recipient human leukocyte antigen (HLA). We, therefore, generated universally compatible immune nonresponsive human iPSCs by gene editing. Transcription activator-like effector nucleases (TALENs) were designed for selective elimination of HLA DR expression. The engineered nucleases completely disrupted the expression of HLA DR on human dermal fibroblast cells (HDF) that did not express HLA DR even after stimulation with IFN-γ. Teratomas formed by HLA DR knockout iPSCs did not express HLA DR, and dendritic cells differentiated from HLA DR knockout iPSCs reduced CD4+ T cell activation. These engineered iPSCs might provide a novel translational approach to treat multiple recipients from a limited number of cell donors.

High-throughput sequencing defines donor and recipient HLA B-cell epitope frequencies for prospective matching in transplantation

Compatibility for human leukocyte antigen (HLA) genes between transplant donors and recipients improves graft survival but prospective matching is rarely performed due to the vast heterogeneity of this gene complex. To reduce complexity, we have combined next-generation sequencing and in silico mapping to determine transplant population frequencies and matching probabilities of 150 antibody-binding eplets across all 11 classical HLA genes in 2000 ethnically heterogeneous renal patients and donors. We show that eplets are more common and uniformly distributed between donors and recipients than the respective HLA isoforms. Simulations of targeted eplet matching shows that a high degree of overall compatibility, and perfect identity at the clinically important HLA class II loci, can be obtained within a patient waiting list of approximately 250 subjects. Internal epitope-based allocation is thus feasible for most major renal transplant programs, while regional or national sharing may be required for other solid organs.

HLA-A gene knockout using CRISPR/Cas9 system toward overcoming transplantation concerns

BackgroundThe treatment of many cancers and genetic diseases relies on novel engraftment approaches such as cell therapy and hematopoietic stem cell transplantation (HSCT). However, these methods are hindered by the alloreactive immune responses triggered by incompatible human leukocyte antigen (HLA) molecules. A successful HSCT procedure requires the eradication of donor and recipient HLA alloimmunization. Eliminating HLA-A gene expression using clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 nuclease (CRISPR/Cas9) could be a great approach to increase the possibility of a successful HSCT through extending pool of unrelated donors.ResultsOur dual gRNA approach introduced a large deletion in the HLA-A gene. Among 22 single-cloned cells, two clones (9.09%) and 11 clones (50%) received homozygous and heterozygous large deletions, respectively. Finally, the real-time PCR results also revealed that HLA-A gene expression was diminished significantly.ConclusionThe results suggested that CRISPR/Cas9 could be used as an efficient technique to introduce HLA-A gene knockout; thus, it can considerably lessen the burden of finding a fully matched donor by lowering the alleles required for a successful HSCT.

HLA-associated preadaptation in HIV Vif is associated with higher set point viral load and faster CD4+ decline in Zambian transmission pairs.

We investigated the relationship between human leukocyte antigen (HLA)-associated preadaptation for the entire subtype C HIV-1 proteome of the transmitted founder virus and subsequent HIV-1 disease progression in a cohort of heterosexual linked transmission pairs in Zambia. An adaptation model was used to calculate an adaptation score for each virus-HLA combination in order to quantify the degree of preadaptation of the transmitted virus to the linked recipient's HLA alleles. These scores were then assessed for their relationship to viral load and longitudinal CD4+ decline in the recipient. Viral RNA was extracted from the plasma of the donor partner and the linked recipient near the time of transmission, as well as longitudinally from the linked recipient. Viral adaptation scores were calculated for each individual and each protein in the subtype C HIV-1 proteome. The majority of HLA-associated sites were located in Gag, Pol and Nef; however, proportional to protein length, the accessory and regulatory proteins contained a relatively high proportion of HLA-associated sites. Over the course of infection, HLA-mediated immune adaptation increased for all proteins except Vpu and gp120. Preadaptation was positively associated with higher early set point viral load and faster CD4+ decline. When examined by protein, preadaptation in Pol and Vif were statistically significantly associated with these markers of disease progression. Adaptation in Pol had the greatest impact on viral control. Despite containing a large proportion of HLA-associated sites, Vif was the only regulatory or accessory protein for which preadaptation significantly correlated with disease progression.

Incidence and outcome of post-transplant lymphoproliferative disorders in lung transplant patients: Analysis of ISHLT Registry

Post-transplant lymphoproliferative disorder (PTLD) is a life-threatening complication following lung transplant. We studied incidence and risk factors for PTLD in adult lung transplant recipients (LTRs) using the International Society for Heart and Lung Transplantation Registry. The International Society for Heart and Lung Transplantation Registry was used to identify adult, first-time, single and bilateral LTRs with at least 1 year of follow-up between 2006 and 2016. Kaplan-Meier method was used to describe the timing and distribution of PTLD. Univariable and multivariable Cox proportional hazards regression models were used to examine clinical characteristics associated with PTLD. Of 19,309 LTRs in the analysis cohort, we identified 454 cases of PTLD. Cumulative incidence of PTLD was 1.1% (95% CI = 1.0%-1.3%) at 1 year and 4.1%(95% CI = 3.6%-4.6%) at 10years. Of the PTLD cases, 47.4% occurred within the first year following lung transplantation. In the multivariable model, independent risk factors for PTLD included age, Epstein-Barr virus serostatus, restrictive lung diseases, and induction. Risk of PTLD during the first year after transplant increased with increasing age in patients between 45 and 62 years at time of transplantation; the inverse was true for ages <45 years or >62 years. Finally, receiving a donor organ with human leukocyte antigen types A1 and A24 was associated with an increased risk of PTLD, whereas the recipient human leukocyte antigen type DR11 was associated with a decreased risk. Our study indicates that PTLD is a relatively rare complication among adult LTRs. We identified clinical characteristics that are associated with an increased risk of PTLD.

Impact of donor KIRs and recipient KIR/HLA class I combinations on GVHD in patients with acute leukemia after HLA-matched sibling HSCT

In addition to T cells, NK cells can also participate in the outcome of hematopoietic stem cell transplantation (HSCT) mainly through the interaction between donor killer cell immunoglobulin-like receptors (KIRs) and recipient human leukocyte antigen (HLA) class I molecules. There is a risk of GVHD other than leukemia relapse after allogeneic HSCT that activation of donor NK cells in the absence of appropriate inhibitory ligands will be one of the reasons. To investigate the impact of donor KIRs and recipient KIR/HLA class I combinations on GVHD and leukemia relapse in patients with acute leukemia after HSCT, 100 patients with acute leukemia who received HSCT from their HLA-matched siblings were included in this study. Genotypes of 16 KIR genes and two 2DS4 variants (full length and deleted alleles), along with HLA-A/B genotypes, were determined by PCR-SSP. HLA-C genotyping was done with the SSO-Luminex method. Chimerism analysis was done using 16 short tandem repeats (STRs) to detect early leukemia relapse. Acute (a)GVHD occurred in 38 patients, and 16 of them died during the study. None of the recipients showed any sign of leukemia relapse after HSCT. Full donor chimerism was observed in all tested patients during the first year after HSCT. Our results also indicated an increased risk of aGVHD in AA recipients with the C2/Cx, Bw4+ (or A-Bw4+) or HLA-A3−/A11− genotypes who received HSCT from Bx donors. Our results showed that donor selection based on donor-recipient KIR genotypes and recipient HLA class I status can improve the outcome of HSCT.

Deep sequence analysis of HIV adaptation following vertical transmission reveals the impact of immune pressure on the evolution of HIV.

Human immunodeficiency virus (HIV) can adapt to an individual’s T cell immune response via genomic mutations that affect antigen recognition and impact disease outcome. These viral adaptations are specific to the host’s human leucocyte antigen (HLA) alleles, as these molecules determine which peptides are presented to T cells. As HLA molecules are highly polymorphic at the population level, horizontal transmission events are most commonly between HLA-mismatched donor/recipient pairs, representing new immune selection environments for the transmitted virus. In this study, we utilised a deep sequencing approach to determine the HIV quasispecies in 26 mother-to-child transmission pairs where the potential for founder viruses to be pre-adapted is high due to the pairs being haplo-identical at HLA loci. This scenario allowed the assessment of specific HIV adaptations following transmission in either a non-selective immune environment, due to recipient HLA mismatched to original selecting HLA, or a selective immune environment, mediated by matched donor/recipient HLA. We show that the pattern of reversion or fixation of HIV adaptations following transmission provides insight into the replicative cost, and likely compensatory networks, associated with specific adaptations in vivo. Furthermore, although transmitted viruses were commonly heavily pre-adapted to the child’s HLA genotype, we found evidence of de novo post-transmission adaptation, representing new epitopes targeted by the child’s T cell response. High-resolution analysis of HIV adaptation is relevant when considering vaccine and cure strategies for individuals exposed to adapted viruses via transmission or reactivated from reservoirs.