13-P: Profiling of HLA antibodies in wait listed organ graft recipients with the use of solid phase single antigen beads: Pre-sensitization to class I and II and implications for the calculated PRA (CPRA)

Abstract Introduction: In the Trial to Reduce Alloimmunization to Platelets (TRAP) study, 101 of the 530 subjects became clinically refractory (CR) to platelet transfusions in the absence of detectable antibodies against HLA as measured by the lymphocytotoxicity assay (LCA). Using more sensitive bead-based detection methods we have previously demonstrated that while many of these LCA- patients do have anti-HLA antibodies, that these low to moderate level antibodies do not predict refractoriness. In addition to being less sensitive then bead based methods, the LCA screen only detects complement-binding antibodies. As these antibodies could be important for platelet rejection, we assessed if previously undetected complement-binding antibodies could account for some of the refractoriness seen in LCA- patients. Methods: 169 LCA- (69 CR, 100 non-CR) and 20 LCA+ (10 CR, 10 non-CR) subjects were selected from the TRAP study. Anti-class I HLA IgG and C1q binding antibodies were measured in serum or plasma using two different multi-analyte, semi-quantitative, bead-based fluorescent antibody detection assays: the LabScreen mixed Luminex assay, and the LabScreen single antigen class I assay with or without added EDTA (One Lambda). Groups were compared using an unpaired t-test, a=0.05, and correlation between variables was also assessed. Results: New measurements of anti-class I HLA IgG antibodies reliably reproduced earlier data with a strong correlation between the old and new measurements (R2=0.9736, p<0.0001). While some of the LCA- subjects did have detectable C1q-binding anti-class I HLA antibodies, and some LCA+ subjects did not, levels of these antibodies were significantly higher among LCA+ subjects (p<0.0001). Levels of C1q-binding anti-class I HLA antibodies were not significantly different between CR and non-CR among either the LCA- or LCA+ subjects. Conclusions: While complement-binding anti-class I HLA antibody levels were higher in the LCA+ subjects, higher levels of these antibodies were not seen in CR LCA+ patients as compared with non-CR LCA+ patients. Complement-binding anti-class I HLA antibodies do not account for refractoriness seen among the LCA- TRAP subjects. This work confirms that low to mid level anti-class I antibodies do not drive refractoriness to platelets, and suggests that antibody-independent mechanisms cause refractoriness in patients lacking higher levels of anti-HLA antibodies. Disclosures No relevant conflicts of interest to declare.

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P1604SIGNIFICANT DETECTION OF UNEXPLAINED HLA ANTIBODIES WITH SINGLE-ANTIGEN BEADS IN PATIENTS ON THE WAITING-LIST WITHOUT PREVIOUS SENSITIZING EVENTS

Nephrology Dialysis Transplantation ◽

10.1093/ndt/gfaa142.p1604 ◽

2020 ◽

Vol 35 (Supplement_3) ◽

Author(s):

Sara Núñez Delgado ◽

Carla Burballa Tarrega ◽

José Luis Caro ◽

Carlos Arias Cabrales ◽

Marisa Mir Fontana ◽

...

Keyword(s):

Solid Phase ◽

Class Ii ◽

Automated Detection ◽

Waiting List ◽

Hla Antigen ◽

Hla Antibodies ◽

Single Antigen ◽

Screening Assays ◽

As Solid Phase ◽

Limit Access

Abstract Background and Aims The introduction of more sensitive and specific tools as solid phase immunoasssays has improved the ability to detect HLA antibodies. The techniques based on solid phase immunoassays in Luminex system can be performed either as screening assays (with pooled antigen panels that use bead populations coated in affinity-purified class I or class II HLA molecules) or to assess the specificity with single-antigen bead (SAB) assays (single cloned allelic HLA antigen).The sensitivity of each assay Is different, and their results may be discordant. Our objective was to evaluate the potential discrepancies between tests in a cohort of patients on our waiting list with no previous sensitizing events, for their potential influence in the access to transplantation. Method Observational study of 184 patients included in the kidney-transplant waiting list on March 31st, 2019. All possible sensitizing events (pregnancy, transfusion and previous transplants) were registered. HLA antibodies where analyzed both by screening and SAB tests. Results We limited the observations to males (64.7% of the cohort), as most women (95.4%) had a known sensitizing event, not being possible to discard possible pregnancies in the remaining. Of men, 46.2% had a sensitizing event and 63.8% did not. All 63 unsensitized patients showed a negative screening test, and 49 (77,78%) had at least one SAB done being positive in 73.4% (36/49). The positive SAB yielded a cPRA >10% in 30 cases (between 21-85%), mostly (27/30) due to HLA class II antibodies (88.8% with at least one DQ antibody) with a median MFI of 1571 (range:752-17650). A thorough review of specificities showed that 81% DQB1* and 89.6% DQA1* antibodies did not show consistency in all beads included for the same allele. Conclusion Screening and SAB assays show a significant discordancy in unsensitized men included in the waiting list for kidney transplantation. Automated detection of antibodies by SAB without a proper specialized interpretation may wrongly limit access to transplantation.

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13: Computational Analysis of the Single Antigen Beads Used in Solid Phase Assays for the Detection of Anti-HLA Antibodies

The Journal of Heart and Lung Transplantation ◽

10.1016/j.healun.2009.11.020 ◽

2010 ◽

Vol 29 (2) ◽

pp. S10-S11 ◽

Cited By ~ 1

Author(s):

O.E. Pajaro ◽

J.K. Kirklin ◽

J.F. George

Keyword(s):

Computational Analysis ◽

Solid Phase ◽

Hla Antibodies ◽

Single Antigen

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Comparison Between Total IgG, C1q, and C3d Single Antigen Bead Assays in Detecting Class I Complement-Binding Anti-HLA Antibodies

Transplantation Proceedings ◽

10.1016/j.transproceed.2017.09.040 ◽

2017 ◽

Vol 49 (9) ◽

pp. 2031-2035 ◽

Cited By ~ 8

Author(s):

M.A. Moreno Gonzales ◽

D.G. Mitema ◽

B.H. Smith ◽

C.A. Schinstock ◽

M.D. Stegall ◽

...

Keyword(s):

Class I ◽

Hla Antibodies ◽

Single Antigen

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Management of Donor-Specific Antibodies in Haploidentical Transplant: Multicenter Experience From the Madrid Group of Hematopoietic Transplant

Frontiers in Immunology ◽

10.3389/fimmu.2021.674658 ◽

2021 ◽

Vol 12 ◽

Author(s):

Rebeca Bailén ◽

José Luis Vicario ◽

Laura Solán ◽

Irene Sánchez-Vadillo ◽

Pilar Herrera ◽

...

Keyword(s):

Solid Phase ◽

Hla Class I ◽

Progressive Increase ◽

Buffy Coat ◽

Class I ◽

Hematopoietic Stem ◽

Specific Antibodies ◽

Single Antigen ◽

Donor Specific Antibodies ◽

Neutrophil Engraftment

BackgroundDonor specific antibodies (DSAs) can be responsible for graft failure (GF) in the setting of mismatched hematopoietic stem cell transplantation (HSCT). The aim of our study is to report the experience of the Madrid Group of Hematopoietic Transplant (GMTH) in patients with DSAs undergoing haplo-HSCT.MethodsPatients undergoing haplo-HSCT in centers from the GMTH from 2012 to 2020 were included in the study. DSAs were analyzed with a solid-phase single-antigen immunoassay; monitoring was performed during desensitization on days -14, -7, 0 and in a weekly basis until neutrophil engraftment. Desensitization strategies varied depending on center experience, immunofluorescence intensity, complement fixation and type of antibodies.ResultsWe identified a total of 20 haplo-HSCT in 19 patients performed with DSAs in 5 centers. 10 (53%) patients presented anti-HLA class I DSAs (6 of them with > 5000 mean fluorescence intensity (MFI)), 4 (21%) presented anti-HLA class II (1 with > 5000 MFI) and 5 (26%) presented both anti-HLA class I and II (5 with > 5000 MFI). 90% of patients received at least two treatments as desensitization strategy and all experienced a decrease of MFI after desensitization (mean reduction 74%). Only one patient who developed progressive increase of MFI after infusion developed GF. Desensitization treatments used included rituximab, immunoglobulins, therapeutic plasma exchange, incompatible platelets, buffy coat and immunosuppressors. Seventeen (90%) patients achieved neutrophil engraftment; one patient died before engraftment because of infection and one patient with class I DSAs developed primary GF despite an intensive desensitization. After a median follow-up of 10 months, OS and EFS were 60% and 58%, respectively, cumulative incidence of relapse was 5% and NRM was 32%.ConclusionsDespite the optimal strategy of DSAs desensitization remains unclear, the use of desensitization treatment guided by DSAs intensity kinetics constitute an effective approach with high rates of engraftment for patients with DSAs in need for an haplo-HSCT lacking an alternative suitable donor.

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109-P: Increased incidence of HLA antibodies (Class I/II) in hematopoietic cell transplant (HCT) candidates detected by a solid phase assay

Human Immunology ◽

10.1016/j.humimm.2008.08.128 ◽

2008 ◽

Vol 69 ◽

pp. S62

Author(s):

Laima Gaidulis ◽

Jiyao Sun ◽

David Senitzer

Keyword(s):

Solid Phase ◽

Hematopoietic Cell ◽

Class I ◽

Cell Transplant ◽

Hematopoietic Cell Transplant ◽

Hla Antibodies ◽

Solid Phase Assay

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ADSORPTION OF CYTOTOXIC ANTI-HLA ANTIBODIES WITH HLA CLASS I IMMUNOSORBANT BEADS

Transplantation Journal ◽

10.1097/00007890-199005000-00019 ◽

1990 ◽

Vol 49 (5) ◽

pp. 925-930 ◽

Cited By ~ 12

Author(s):

LYNN D. DEVITO ◽

HANS W. SOLLINGER ◽

WILLIAM J. BURLINGHAM

Keyword(s):

Hla Class I ◽

Class I ◽

Hla Antibodies

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The impact of anti-HLA antibodies on unrelated cord blood transplantations

Blood ◽

10.1182/blood-2009-10-249219 ◽

2010 ◽

Vol 116 (15) ◽

pp. 2839-2846 ◽

Cited By ~ 162

Author(s):

Minoko Takanashi ◽

Yoshiko Atsuta ◽

Koki Fujiwara ◽

Hideki Kodo ◽

Shunro Kai ◽

...

Keyword(s):

Cord Blood ◽

Solid Phase ◽

Human Leukocyte ◽

Antibody Detection ◽

Red Cross ◽

Hla Antibodies ◽

Platelet Recovery ◽

Neutrophil Recovery ◽

Unrelated Cord Blood ◽

The Impact

Abstract The majority of cord blood transplantations (CBTs) have human leukocyte antigen (HLA) disparities. We investigated the impact that patients' pretransplantation anti-HLA antibodies have on the outcome of CBTs. Testing for anti-HLA antibody and its specificity was performed retrospectively at the Japanese Red Cross Tokyo Blood Center with sensitive solid-phase antibody detection assays. Among 386 CBTs, which were first myeloablative stem cell transplantations for malignancies and used a single unit of cord blood, 89 tested positive. Among the antibody-positive group, the cord blood did not have the corresponding HLA type for the antibody in 69 cases (ab-positive), while 20 cases had specificity against the cord blood HLA (positive-vs-CB). Cumulative incidence of neutrophil recovery 60 days after transplantation was 83% (95% confidence interval [CI], 79%-87%) for the antibody-negative group (ab-negative), 73% (95% CI, 61%-82%) for ab-positive, but only 32% (95% CI, 13%-53%) for the positive-vs-CB (P < .0001, Gray test). With multivariate analysis, the ab-positive showed significantly lower neutrophil recovery than the ab-negative (relative risk [RR] = 0.69, 95% CI, 0.49-0.96, p = .027). The positive-vs-CB had significantly lower neutrophil recovery (RR = 0.23, 95% CI, 0.09-0.56, P = .001) and platelet recovery (RR = 0.31, 95% CI, 0.12-0.81, P = .017) than the ab-negative. Patients' pretransplantation anti-HLA antibodies should be tested and considered in the selection of cord blood.

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