HLA Antigens Research Articles

Clinical Applicability of 2-Field High-Resolution and Extended HLA-Allele Typing in Deceased Donor Kidney Allocation.

HLA-compatibility remains an important triage test for deceased donor kidney allocation. Low-intermediate resolution donor HLA-typing is typically available at allocation, but its accuracy in assigning pre-transplant donor-specific anti-HLA antibody (DSA) and HLA mismatches compared to 2-field high-resolution typing is poorly characterised. Consecutive deceased donor/recipient pairs from a single centre between 2016 and 2020 were included. Majority of donor typing at HLA-ABDRB1 loci were performed at low-intermediate resolution, with 2-field high-resolution NGS typing across extended loci performed by NGS-technique post-transplantation. We compared the two typing methods for (1) accuracy of pre-transplant DSA assignment; (2) misassignment of HLA-antigen/allele mismatches and performance of each model for acute rejection and (3) proportion of recipients who developed de novo DSA (dnDSA) when matched at antigen but mismatched at allele level. Of 179 deceased donor/recipient pairs, 157 donors had low-intermediate resolution typing and 22 with high-resolution ONT typing. Sixty-two recipients (35%) had potential pre-transplant DSAs, with incorrect assignment of allele-specific Class I and II actual DSAs in 31% and 53% of cases, respectively. NGS typing identified 59 (33%) additional HLA-DRB1 allele mismatches. ONT typing accurately assigned pre-transplant DSAs and allele mismatches in all cases. Seven (4%) recipients with antigen/allele level discordance developed dnDSAs, majority HLA-DQ antibodies. Two-field high-resolution donor HLA typing may provide a more accurate transplant immunological risk assessment and identify those at risk of developing dnDSA to matched HLA antigen.

Pan-immune-inflammation value predicts immunotherapy response and reflects local antitumor immune response in rectal cancer.

The pan-immune-inflammation value reflects the systemic inflammatory response, and tumor-infiltrating lymphocytes indicate a local immune response in rectal cancer. However, the association between systemic inflammatory response, as indicated by the pan-immune-inflammation value, and local immune responses in rectal cancer remains unclear. This study analyzed 915 treatment-naïve rectal cancer patients from the Peking Union Medical College Hospital and PLA General Hospital (PLAGH) cohorts who underwent radical surgery to investigate the relationship between the pan-immune-inflammation value and immune responses. Lower pan-immune-inflammation value was significantly associated with improved disease-free survival and cancer-specific survival. Multivariate Cox regression models identified the pan-immune-inflammation value as an independent prognostic factor. In the PLAGH cohort, patients with low pan-immune-inflammation values had higher immune cell levels, activated immune pathways, and increased expression of immune checkpoint genes according to RNA sequencing. Hematoxylin and eosin staining and immunohistochemical analysis revealed that lower pan-immune-inflammation value was associated with higher tumor-infiltrating lymphocyte density, more mature tertiary lymphoid structures, increased CD8+ T cells, and elevated human lymphocyte antigen class I expression. Conversely, patients with high pan-immune-inflammation values exhibited pathways linked to tumor progression, such as angiogenesis, epithelial-mesenchymal transition, hypoxia, KRAS signaling, and TGF-ß signaling. Among patients receiving anti-PD-1 therapy, responders had low pre- and post-treatment pan-immune-inflammation values. The pan-immune-inflammation value is a reliable marker associated with distinct immune microenvironment characteristics and can effectively predict disease-free survival, cancer-specific survival, and response to immunotherapy.

A new strategy for systematically classifying HLA alleles into serological specificities: Update and refinement.

HLA antigens were historically defined according to the unique reactivity pattern of cells expressing HLA molecules with distinctive clusters of allo-antisera and/or monoclonal antibodies. Subsequently, amino acid residues determining epitopes (DEP) in the HLA molecule were correlated with reactivity patterns. In current clinical practice, the presence of allo-antibodies is assessed using Luminex-based solid phase single antigen bead (SAB) assays for transplantation. Recently, novel antigens were proposed for HLA molecules with DEP patterns that do not match any serologically defined antigens recognised by the WHO Nomenclature Committee. To validate the antigens, mean fluorescence intensity values of SABs tested on >13,000 patients' sera were extracted from clinical databases and analysed by scatter plots using a linear regression model. We found that when two proteins were considered as the same antigen in the original study, for example, HLA-A*02:01 and -A*02:06, their correlation ranked among the highest values at each locus. In contrast, discrete asymmetric outliers were observed when there were different antigens, for example, HLA-A*30:01 and -A*30:02, allowing validation and confirmation of 20 novel antigens for HLA-A, -B, -C and -DR. The outliers were confirmed to be true or false by flow cytometric crossmatches. In addition to the previously defined residues for antigen assignments, findings suggest that further distinction should be made for common antigens by including the substitutions at residue 67 of HLA-B, 67 and 74 of -DR. These serologic analyses can be applied systematically to identify and confirm novel antigens. These developments will lead to designing optimal SAB panels and further improving virtual donor-specific antibodies assessment.

460 (PB448): On-target – prioritizing specificity during T Cell Engager discovery against peptide: HLA antigens

460 (PB448): On-target – prioritizing specificity during T Cell Engager discovery against peptide: HLA antigens

Calculated Panel Reactive Antibody for an Organ-Sharing Zone: Concept and Execution Based on Data from North Kerala

Background Calculated-PRA (CPRA) is derived by virtually matching a recipient’s antibody profile against HLA antigens of a representative donor pool of a geographical region. Materials and Methods An android application–based CPRA calculator was created from HLA typing data (A/B/DR loci) of 712 consecutive living donors spanning over last 10 years from an organ-sharing region in Kerala. Only an open-source software was used. Results Our HLA data, compared with the National Marrow Donor Program (NMDP) 2011 database, show that the most common haplotype frequencies show comparable positions in order of prevalence. Available online PRA calculators like OPTN and Canadian CPRA show significant differences in PRA estimation when used in our population. This calculator provides a more accurate and realistic estimate of sensitization against the representative donor pool. Conclusion This CPRA tool can be customized for any allocation region using portable open-source software. The donor pool can be updated continually by populating data from multiple regional centers.

Refining cPRA calculation to improve HLA compatibility assessment in organ transplantation: A detailed picture of the Paris waiting list.

The determination of panel reactive antibodies (cPRA) scores plays a critical role in assessing the immunological compatibility between organ transplant recipients and potential donors. Traditional cPRA methods focus on a limited number of HLA loci using physical cytotoxicity tests. However, advancements such as the Luminex single antigen (LSA) assay, which uses mean fluorescence intensity (MFI) of individualised HLA antigens for antibody evaluation, provide a foundation for a more precise assessment. We developed cPRAdictor, a novel cPRA calculation tool using a large series of HLA-type individuals in France with NGS. cPRAdictor was applied to a cohort of 5962 kidney transplant candidates in Paris. We analysed how extending the range of HLA specificities could affect cPRA values. Implementing cPRAdictor revealed and allowed quantification of the significant discrepancies in cPRA values that appeared when HLA loci C and DP, and antigen-specific antibodies were taken into account. Notably, over 43% of the immunised transplant candidates showed an increase in calculated cPRA values when considering C/DP loci and antigen-specific antibodies, negatively impacting their eligibility and prioritisation in the transplantation programme. These findings highlight the necessity of revisiting cPRA calculation methodologies to include a broader spectrum of immunological data, as more exhaustive and precise information regarding anti-HLA antibodies in patients' sera and donor and recipient HLA typing are available prospectively. This will strongly improve both accuracy and equity at the organ allocation step, especially for highly sensitised candidates for whom organ offers are very limited in number.

V-110.7: Prevalence of non- representation of HLA antigens and alleles in Single Antigen Bead assay panels in patients at a referral lab.

V-110.7: Prevalence of non- representation of HLA antigens and alleles in Single Antigen Bead assay panels in patients at a referral lab.

Prognostic Impact of Human Lymphocyte Antigen (HLA) Class I Expression in Patients With Breast Cancer.

Various biomarkers are utilized in the field of breast cancer. Human lymphocyte antigen (HLA) class I molecules have a critical role in cancer immune surveillance. Therefore, this study aimed to assess the HLA class I expression and analyze the correlation with clinicopathologic factors in breast cancer. We investigated the clinical pathology archives of 150 consecutive patients with breast cancer who underwent a curative operation at the Sapporo Medical University, Japan, from January 2012 to December 2014. Immunohistochemical staining was used to evaluate HLA class I expression and CD8-positive T cell infiltration. The Pearson χ2 test was used to assess HLA class I expression level and clinicopathological parameters. The Kaplan-Meier method was used to evaluate survival and the log-rank test to analyze the differences between survival curves. Patients with dull/negative HLA class I had significantly poor disease-free survival (DFS) compared with those with positive HLA class I (p=0.0073). Univariate analyses revealed that pT, pN, positive lymphatic invasion, and dull/negative HLA class I were significantly associated with DFS. Multivariate analyses revealed dull/negative HLA class I as an independent poor prognostic factor (hazard ratio=2.75, 95% confidence interval=1.30-5.80, p=0.008). HLA class I expression level may have a very sensitive prognostic effect on patients with breast cancer.

New Therapies for Highly Sensitized Patients on the Waiting List.

Exposure to HLA alloantigens through pregnancy, blood products, and previous transplantations induce powerful immunologic responses that create an immunologic barrier to successful transplantation. This is commonly detected through screening for HLA antibodies using Luminex beads coated with HLA antigens at transplant evaluation. Currently accepted approaches to desensitization include plasmapheresis/low-dose or high-dose intravenous Ig plus anti-CD20. However, these approaches are often unsuccessful because of the inability to remove high titer circulating HLA antibodies and limit rebound responses by long-lived anti-HLA antibody secreting plasma cells (PCs) and memory B cells (B MEM ). This is especially significant for patients with a calculated panel reactive antibody of 99%-100%. Newer desensitization approaches, such as imlifidase (IgG endopeptidase), rapidly inactivate IgG molecules and create an antibody-free zone by cleaving IgG into F(ab'2) and Fc fragments, thus eliminating complement and cell-mediated injury to the graft. This represents an important advancement in desensitization. However, the efficacy of imlifidase is limited by pathogenic antibody rebound, increasing the potential for antibody-mediated rejection. Controlling antibody rebound requires new strategies that address the issues of antibody depletion and inhibition of B MEM and PC responses. This will likely require a combination of agents that effectively and rapidly deplete pathogenic antibodies and prevent immune cell activation pathways responsible for antibody rebound. Here, using anti-IL-6 receptor (tocilizumab) or anti-IL-6 (clazakizumab) could offer long-term control of B MEM and PC donor-specific HLA antibody responses. Agents aimed at eliminating long-lived PCs (anti-CD38 and anti-B-cell maturation antigen×CD3) are likely to benefit highly HLA sensitized patients. Complement inhibitors and novel agents aimed at inhibiting Fc neonatal receptor IgG recycling will be important in desensitization. Administering these agents alone or in combination will advance our ability to effectively desensitize patients and maintain durable suppression post-transplant. After many years of limited options, advanced therapeutics will likely improve efficacy of desensitization and improve access to kidney transplantation for highly HLA sensitized patients.

A novel hypothesis on mechanisms and potential role of host cell membrane proteins incorporated into the viral envelope in alloreactivity

Despite significant advances in transplantation medicine, allograft rejection remains a major challenge in clinical practice. The preexistence of alloreactive lymphocytes is a primary cause of allograft rejection. The forthcoming challenges in clinical transplantation will involve the suppression or eradication of allospecific memory T cells. Viral infections and allograft rejection interact in multiple ways that can compromise the survival of transplanted organs. Evidence is currently accumulating on the incorporation of HLA antigens and other host cell plasma membrane molecules into the viral envelope. A consequence of the viral envelope displaying the HLA signature acquired from the plasma membrane of infected cells is that when virions are transmitted to the next host, the newly infected person became exposed to allogeneic molecules stimulating alloimmunity and generating memory to alloantigens. Thus, successive exposure to viral infections throughout life could potentially contribute to the development of alloimmunity and the generation of numerous clones of memory alloreactive lymphocytes. In this paper a novel hypothesis is developed on the potential role and mechanisms of alloresponse induced by human spread of enveloped viruses. As this hypothesis could aid in the knowledge of preexisting alloreactivity, additional research into the intricacies of virion-incorporated host cell proteins is necessary. A deeper understanding of this dynamic interaction will help promote advances in the long-term acceptance of transplants.

Allosensitisation in NHP results in cross-reactive anti-SLA antibodies not detected by a lymphocyte-based flow cytometry crossmatch.

Xenotransplantation is a potential option for individuals for whom an acceptable human allograft is unavailable. Individuals with broadly reactive HLA antibodies due to prior exposure to foreign HLA are potential candidates for a clinical xenotransplant trial. It remains controversial if allosensitisation results in the development of cross-reactive antibodies against SLA. This may require increased histocompatibility scrutiny for highly sensitised individuals prior to enrollment in a clinical trial. Serum samples were obtained from non-human primates sensitised via serial skin transplantation from maximally MHC-mismatched donor, as reported. Sera from pre- and post-allosensitisation timepoints were assessed in a flow crossmatch (FXM) for IgM and IgG binding to pig splenocytes with or without red blood cell adsorption. Xenoreactive antibodies were eluted from pig splenocytes and screened on a single antigen HLA bead assay. A MHC Matchmaker algorithm was developed to predict potential conserved amino acid motifs among the pig, NHP, and human. Our sensitised NHP model was used to demonstrate that allosensitisation does not result in an appreciable difference in xenoreactive antibody binding in a cell-based FXM. However, antibody elution and screening on single antigen HLA beads suggest the existence of potential cross-reactive antibodies against SLA. The cross-reactive IgG after allosensitisation were predicted by comparing the recipient Mamu alleles against its previous allograft donor Mamu alleles and the donor pig SLA alleles. Our study suggests that allosensitisation could elevate cross-reactive antibodies, but a more sensitive assay than a cell-based FXM is required to detect them. The MHC Matchmaker algorithm was developed as a potential tool to help determine amino acid motif conservation and reactivity pattern.

Balancing Equity and HLA Matching in Deceased-Donor Kidney Allocation with Eplet Mismatch.

Prioritization of HLA antigen-level matching in the US kidney allocation system intends to improve post-transplant survival but causes racial disparities and thus has been substantially de-emphasized. Recently, molecular matching based on eplets has been found to improve risk stratification compared to antigen matching. To assign eplets unambiguously, we utilized a cohort of 5193 individuals with high resolution allele-level HLA genotypes from the National Kidney Registry. Using repeated random sampling to simulate donor-recipient genotype pairings based on the ethnic composition of the historical US deceased donor pool, we profiled the percentage of well-matched donors for candidates by ethnicity. The percentage of well-matched donors with zero-DR/DQ eplet mismatch was 3-fold less racially disparate for Black and Asian candidates than percentage of donors with zero-ABDR antigen mismatches, and 2-fold less racially disparate for Latino candidates. For other HLA antigen and eplet mismatch thresholds, the percentage of well-matched donors was more similar across candidate ethnic groups. Compared to the current zero-ABDR antigen mismatch, prioritizing a zero-DR/DQ eplet mismatch in allocation would decrease racial disparities and increase the percentage of well-matched donors. High resolution HLA deceased donor genotyping would enable unambiguous assignment of eplets to operationalize molecular mismatch metrics in allocation. Question: What is the impact of prioritizing low molecular mismatch transplants on racial and ethnic disparities in US deceased-donor kidney allocation, compared to the current prioritization of antigen-level matching?Findings: The lowest-risk eplet mismatch approach decreases racial disparities up to 3-fold compared to lowest-risk antigen mismatch and identifies a larger number of the lowest allo-immune risk donors.Meaning: Prioritizing eplet matching in kidney transplant allocation could both improve outcomes and reduce racial disparities compared to the current antigen matching.

A personalised delisting strategy enables successful kidney transplantation in highly sensitised patients with preformed donor-specific anti HLA antibodies.

This study investigates kidney transplant outcomes in highly sensitised patients after implementing a delisting strategy aimed at enabling transplantation despite preformed donor-specific antibodies (preDSA), with the goal of reducing acute antibody-mediated rejection (aAMR) risk. Fifty-three sensitised recipients underwent kidney transplant after delisting prohibited HLA antigens, focusing initially in low MFI antibodies (<5000), except for anti-HLA-DQ. If insufficient, higher MFI antibodies were permitted, especially for those without an immunogenic eplet pattern assigned. Delisting of Complement-fixing antibodies (C1q+) was consistently avoided. Comparison cohorts included 53 sensitised recipients without DSA (SwoDSA) and 53 non-sensitised (NS). The average waiting time prior to delisting was 4.4 ± 1.8 years, with a reduction in cPRA from 99.7 ± 0.5 to 98.1 ± 0.7, followed by transplantation within 7.2 ± 8.0 months (analysed in 34 patients). Rejection rates were similar among preDSA, SwoDSA, and NS groups (16%, 8%, and 11%, respectively; p = 0.46). However, aAMR was higher in the preDSA group (12%, 4%, and 2%, respectively; p = 0.073), only presented in recipients with DSA of MFI >5000. The highest MFI DSA were against HLA-DP (Median: 10796 MFI), with 50% of preDSA aAMR cases due to anti-DP antibodies (n = 3). Graft survival rates at 1 and 5 years in preDSA group were 94%, and 67%, comparable to SwoDSA (94%, and 70%; p = 0.69), being significantly higher in the NS group (p = 0.002). The five-year recipient survival rate was 89%, comparable to SwoDSA and NS groups (p = 0.79). A delisting strategy enables safe kidney transplant in highly sensitised patients with preDSA, with a slight increase in aAMR and comparable graft and patient survivals to non-DSA cohorts.

Individual HLAs affect survival after allogeneic stem cell transplantation in adult T-cell leukaemia/lymphoma.

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) is the only curative therapy for adult T-cell leukaemia/lymphoma (ATL). Specific HLAs are associated with outcomes of immunotherapy and allo-HSCT. We hypothesised that individual HLAs would affect the clinical outcomes of ATL patients after allo-HSCT. Using data from a Japanese registry, we retrospectively analysed 829 patients with ATL who received transplants from HLA-identical sibling donors or HLA-A, -B, -C or -DRB1 allele-matched unrelated donors between 1996 and 2015. We evaluated the overall mortality risk of HLA-A, -B and -DR antigens with frequencies exceeding 3%. Outcomes were compared between transplants with or without specific HLA antigens. Of the 25 HLAs, two candidates were identified but showed no statistically significant differences by multiple comparison. HLA-B62 was associated with a lower risk of mortality (hazard ratio [HR], 0.68; 95% confidence interval [CI]: 0.51-0.90; p = 0.008), whereas HLA-B60 was associated with a higher risk of mortality (HR, 1.64; 95% CI: 1.19-2.27; p = 0.003). In addition, HLA-B62 was associated with a lower risk of transplant-related mortality (TRM) (HR, 0.52; 95% CI: 0.32-0.85, p = 0.009), whereas HLA-B60 was associated with a higher risk of grades III-IV acute graft-versus-host disease (HR, 2.63; 95% CI: 1.62-4.27; p < 0.001). Neither HLA influenced relapse. The higher risk of acute GVHD in HLA-B60-positive patients and the lower risk of TRM in HLA-B62-positive patients were consistent with previously obtained results from patients with other haematological malignancies. Consideration of HLA in ATL patients may help to predict risk and outcomes after allo-HSCT.

Study of the Bria-IMT regimen and CPI vs physicians' choice in advanced metastatic breast cancer (BRIA-ABC).

TPS1137 Background: BriaCell (BC) human immortalized cell lines have been engineered to trigger robust immune responses and deliver efficacy through diverse mechanisms, including adaptive (involving T-cells) and innate responses (dendritic and NK cells). BC can match patients’ HLA antigens for optimal effectiveness. BC works by several mechanisms, including direct antigen presentation and activation of CD4+ T-cells. When combined with an immune checkpoint inhibitor, the BC regimen has demonstrated clinical benefit in 54 heavily treated MBCs. Most pts whose disease has progressed after checkpoint inhibitor (CPI) therapy showed similar or improved PFS compared to the patient's last treatment regimen. Disease control after prior antibody-drug conjugates (ADCs) has been observed in 40% of patients, and clinical benefit has been seen in 5/7 patients with untreated intracranial metastases. CD8+ Immuno PET shows an increase in CD8+ tumor infiltrating lymphocytes suggesting systemic activation and infiltration into lymphoid organs and metastatic sites. Sequencing of CPI with BC and the latest phase 3 formulation are associated with improved clinical outcomes, including OS (median 13.4 months), PFS, and CBR, which are reflected in the design of this ongoing pivotal registration enabling Phase 3 study [doi:10.1158/1538-7445.sabcs22-p3-07-12]. Methods: Multicenter randomized, open label Bria-IMT regimen (with SV-BR-1-GM cells) plus CPI vs Treatment of Physicians' Choice (TPC) in MBCs with no approved curative therapies available. ECOG &lt;2 allowed with no limit on prior therapies. Eligibility encompasses all MBC subtypes including pts with CNS metastases. Prior immune therapy is allowed if administered more than 21 days before the first cycle of Bria-IMT; treatments within 21 days preclude participation. Initial randomization will be 1:1:1 to the Bria-IMT regimen + CPI (combination), TPC, and the Bria-IMT regimen alone (monotherapy). There will be 100 sites across the US, Canada, and ex-NA for 404 total evaluable pts. The Bria-IMT regimen includes: Day -2 Cyclophosphamide 300mg/m2, Day 0 20 million irradiated SV-BR-1-GM cells intradermally, and 0.1mcg peg α interferon intra-dermally (Day 2 or 3) into each Bria-IMT inoculation site. After the first 150 pts have enrolled, the monotherapy arm will be discontinued. Bria regimen + CPI arms treatment cycles occur q3w. CPI infusion is given every cycle between Day –3 to Day 3 TPC cycle details will be according to the site's SOC. Imaging assessment will be q6w x2 then q8w. The primary endpoint is overall survival with an interim analysis at 144 events targeting a hazard ratio of 0.6. Key secondary endpoints will include PFS, ORR, CBR, CNS event free survival, and TWiST (time without symptoms or toxicities). Safety analysis will be ongoing. Patient-reported outcomes will be incorporated to assess subjective treatment effects. Clinical trial information: NCT06072612 .

#1016 Kidney transplantation in highly sensitized patients with preformed donor-specific antibodies through personalized delisting strategies

Abstract Background and Aims This study explores a personalized delisting strategy enabling kidney transplantation in highly sensitized patients with preformed donor-specific anti-HLA antibodies (DSA) trying to minimize the risk of antibody-mediated rejection (ABMR). Method Retrospective single-centre analysis of 50 kidney transplant recipients with preformed DSA (preDSA) after employing a delisting strategy to enhance their access to transplantation, and without received a pre-transplant or immediate post-transplant desensitization protocol. The delisting approach focused on allowing less deleterious antibodies according to their mean fluorescence intensity (MFI), anti-HLA class and C1q study results. The strategy consisted on eliminating as prohibited HLA antigens those recognized by antibodies with the lowest MFI in the following order: 1st- MFI &amp;lt; 5000; 2nd- MFI &amp;lt; 10000; 3rd-Any MFI. Additionally, delisting prioritized a single locus in the following order: 1st- one of the HLA class I loci (A, B, or Cw); 2nd- the rest of the class I loci; 3rd- HLA-DP, followed by DR. C1q studies were performed before delisting and transplantation was contraindicated in the presence of DSA detected in the C1q assay. Two comparative cohorts included 50 sensitized recipients without pre-transplant DSA (SwoDSA) and 50 non-sensitized recipients (NS). Results The delisting strategy allowed transplantation with preformed DSA and demonstrated comparable rejection rates to SwoDSA and NS groups (16%, 14% and 8%, respectively; log-rank = 0.28). However, the occurrence of acute ABMR was 12% in the preDSA group, significantly higher than in SwoDSA (1%) and NS (0%) (log-rank = 0.0093). The immunological risk assumed in delisting correlated with ABMR incidence (patients with ABMR had significantly higher sum MFI [mean ± SD: 9301 ± 6340 vs 4492 ± 5641; p = 0.049]), emphasizing the importance of tailored strategies. DSA persistence after transplantation correlated with higher MFI and increased ABMR risk. Of note, 16% of preDSA patients developed de novo DSA versus only the 4% of SwoDSA and 0% of NS patients (p = 0.004). After a mean follow-up of 3.1 ± 2.1 years, the 1-, 3- and 5-year death-censored allograft survival rates were 100%, 90% and 78%, respectively, in the preDSA group; 98%, 84% and 84% in the SwoDSA group and 100% in NS group (log-rank = 0.02). Conclusion The present study demonstrates the feasibility and acceptable outcomes of kidney transplantation in highly sensitized patients with preformed DSA through a personalized delisting strategy without using desensitization protocols.

Homozygosity in any HLA locus is a risk factor for specific antibody production: the taboo concept 2.0.

In a cooperative study of the University Hospital Leipzig, University of Leipzig, and the Charité Berlin on kidney transplant patients, we analysed the occurrence of HLA-specific antibodies with respect to the HLA setup of the patients. We aimed at the definition of specific HLA antigens towards which the patients produced these antibodies. Patients were typed for the relevant HLA determinants using mainly the next-generation technology. Antibody screening was performed by the state-of-the-art multiplex-based technology using microspheres coupled with the respective HLA alleles of HLA class I and II determinants. Patients homozygous for HLA-A*02, HLA-A*03, HLA-A*24, HLA-B*07, HLA-B*18, HLA-B*35, HLA-B*44, HLA-C*03, HLA-C*04, and HLA-C*07 in the class I group and HLA-DRB1*01, HLA-DRB1*03, HLA-DRB1*07, HLA-DRB1*15, HLA-DQA1*01, HLA-DQA1*05, HLA-DQB1*02, HLA-DQB1*03(7), HLA-DQB1*06, HLA-DPA1*01, and HLA-DPB1*04 in the class II group were found to have a significant higher antibody production compared to the heterozygous ones. In general, all HLA determinants are affected. Remarkably, HLA-A*24 homozygous patients can produce antibodies towards all HLA-A determinants, while HLA-B*18 homozygous ones make antibodies towards all HLA-B and selected HLA-A and C antigens, and are associated with an elevation of HLA-DRB1, parts of DQB1 and DPB1 alleles. Homozygosity for the HLA class II HLA-DRB1*01, and HLA-DRB1*15 seems to increase the risk for antibody responses against most of the HLA class I antigens (HLA-A, HLA-B, and HLA-C) in contrast to HLA-DQB1*03(7) where a lower risk towards few HLA-A and HLA-B alleles is found. The widely observed differential antibody response is therefore to be accounted to the patient's HLA type. Homozygous patients are at risk of producing HLA-specific antibodies hampering the outcome of transplantation. Including this information on the allocation procedure might reduce antibody-mediated immune reactivity and prevent graft loss in a patient at risk, increasing the life span of the transplanted organ.

T-Cell Epitope Vaccine Prediction Analysis Targeting Phosphoprotein (P) Rabies Virus Based on the Presence of HLA-I Alleles A, B, and C Loci Throughout Southeast Asia: An Immunoinformatics Study

T cell immunity, like responses of CD4+and CD8+ T-cell, plays an important role to fight against viral infections and pathological harm. Several previous studies have shown the results that rabies virus (RABV) protein can act as an ideal receptor for rabies neuroseptic vaccine by inducing a response of T-cell. In this research, we evaluated possible vaccine epitopes based on the Rabies virus sequence and human lymphocyte antigen (HLA) distribution. First, this study used the rabies virus protein P sequence obtained from the NCBI database. Next, we predicted rabies CTL protein epitopes based on the frequency of HLA-I distribution allele locus A, B, and C in Southeast Asia region (&gt; 1%) using Immune Epitope Database and Analysis Resource (iedb.org). Our results predict the presence of 12 epitopes of the protein P RABV. A cluster analysis of epitopes shows that seven P-protein clusters cover 97.47% of the Southeast Asian population. After a conservative epitope analysis, 8 epitopes of protein P showed protection in 11 different types of isolated Rabies virus. Finally, 4 epitopes (SQTVEEIISY119-128; RSSGIFLYNF218-227, ASGPPALEW178-186, IISYVTVNF125-133) were used to vaccinate 97.47% of people in Southeast Asia. Our results suggest that both single and combined CTL epitopes which were predicted in this study can be used as a more effective alternative vaccine against rabies virus’ infections and development

Using single antigen specificity magnetic beads for the isolation of specific antibodies against HLA antigens.

The presence of multiple donor-specific antibodies (DSAs) targeting HLA antigens poses a challenge to transplantation. Various techniques, including the use of recombinant cell lines and crossmatch cells have been developed to isolate DSAs. To simplify the extraction of HLA-specific DSAs from complex sera, we introduced magnetic beads with single HLA specificity (MagSort). Sera were treated with MagSort, allowing HLA-specific antibodies to bind to the beads, and these specific antibodies were subsequently eluted. MagSort beads, coated with 59 different HLA variants, underwent testing through 1329 adsorption/elution processes, demonstrating their effectiveness and specificity in adsorbing and eluting HLA-specific antibodies. The MagSort method proves comparable to the cell method, showing similar isolated antibody binding patterns. The isolated antibody binding patterns from MagSort reveal both known eplets and unknown patterns, suggesting its utility for eplet discovery. Additionally, MagSort proved effective in extracting signals for flow cytometry cross-matching, offering a means to assess the binding capability of isolated antibodies against specific donor cells.

Successful Desensitization in a Patient with Donor-Specific Antibodies Persisting after Pretransplant Immunosuppression Using Intravenous Immunoglobulin and Plasma Exchange

The use of posttransplant cyclophosphamide has revolutionized the field of haploidentical hematopoietic stem cell transplant. The impact has been especially enhanced in low- and middle-income countries. Unrelated donor pool in developing nations is often limited due to the lack of large unrelated donor registries. Donor-specific antibodies (DSAs) are preformed immunoglobulin G anti-human leukocyte antigen (HLA) antibodies against HLA antigens that are not shared with the donor. We present successful desensitization in a 13-year-old patient with class III β-thalassemia with very high MFI DSAs with flow crossmatch positivity, persisting after pretransplant immunosuppression.