Persistent strong anti-HLA antibody at high titer is complement binding and associated with increased risk of antibody-mediated rejection in heart transplant recipients

Adriana Zeevi, John Lunz, Brian Feingold, Michael Shullo, Christian Bermudez, Jeffery Teuteberg, Steven Webber, Adriana Zeevi, John Lunz, Brian Feingold, Michael Shullo, Christian Bermudez, Jeffery Teuteberg, Steven Webber

Abstract

Background: Sensitized heart transplant candidates are evaluated for donor-specific anti-HLA IgG antibody (DSA) by Luminex single-antigen bead (SAB) testing (SAB-IgG) to determine donor suitability and help predict a positive complement-dependent cytotoxicity crossmatch (CDC-XM) by virtual crossmatching (VXM). However, SAB testing used for VXM does not correlate perfectly with CDC-XM results and individual transplant programs have center-specific permissible thresholds to predict crossmatch positivity. A novel Luminex SAB-based assay detecting C1q-binding HLA antibodies (SAB-C1q) contributes functional information to SAB testing, but the relationship between SAB strength and complement-binding ability is unclear.

Methods: In this retrospective study, we identified 15 pediatric and adult heart allograft candidates with calculated panel-reactive antibody (cPRA) >50% by SAB-IgG and compared conventional SAB-IgG results with SAB-C1q testing.

Results: Pre- and post-transplant DSA by SAB-C1q correlated with DSA by SAB-IgG and also with CDC-XM results and early post-transplant endomyocardial biopsy findings. Individual HLA antibodies by SAB-IgG in undiluted sera correlated poorly with SAB-C1q; however, when sera were diluted 1:16, SAB-IgG results were well correlated with SAB-C1q. In some sera, HLA antibodies with low mean fluorescent intensity (MFI) by SAB-IgG exhibited high SAB-C1q MFIs for the same HLA antigens. Diluting or heat-treating these sera increased SAB-IgG MFI, consistent with SAB-C1q results. In 13 recipients, SAB-C1q-positive DSA was associated with positive CDC-XM and with early clinical post-transplant antibody-mediated rejection (cAMR).

Conclusions: Risk assessment for positive CDC-XM and early cAMR in sensitized heart allograft recipients are correlated with SAB-C1q reactivity.

Conflict of interest statement

Disclosure statement

The authors have no conflicts of interest to disclose.

Copyright © 2013 International Society for Heart and Lung Transplantation. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1
Figure 1
Correlation of the HLA Class I antibody single-antigen bead (SAB) mean fluorescent intensity (MFI) results of 873 beads from 9 individual sera assessed by conventional IgG and C1q testing. (A) Comparison of SAB results using undiluted sera vs C1q results. The HLA alleles were segregated using cutoff values of 8,000 MFI in the conventional IgG SAB assay using undiluted sera and 500 MFI for C1q testing. This was used to generate positive and negative predictive values. (B) Comparison of SAB results using sera diluted 1:16 vs C1q results. The HLA alleles were segregated using cutoff values of 8,000 MFI in the conventional IgG SAB assay using 1:16 diluted sera and 500 MFI for the C1q testing for use in generating positive and negative predictive values.
Figure 2
Figure 2
Receiver–operator characteristic curve analysis examining the ability of a mean fluorescent intensity (MFI) value from conventional single-antigen bead testing using (A) undiluted sera or (B) sera diluted 1:16 to predict a positive C1q test value (MFI >500). A better area under the curve (AUC) was found using the 1:16 diluted sera (AUC = 0.988) compared with the undiluted sera (AUC = 0.821).

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Source: PubMed

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