HLA-DQ-Specific Recombinant Human Monoclonal Antibodies Allow for In-Depth Analysis of HLA-DQ Epitopes.

Suzanne Bezstarosti,Dave L Roelen,Manon Vergunst,Johan W De Fijter,Sebastiaan Heidt,Merve Uyar-Mercankaya,Marry E I Franke-Van Dijk,Frans H J Claas,Kim H Bakker,Rico Buchli,Cynthia S M Kramer

doi:10.3389/fimmu.2021.761893

Abstract

HLA-DQ donor-specific antibodies (DSA) are the most prevalent type of DSA after renal transplantation and have been associated with eplet mismatches between donor and recipient HLA. Eplets are theoretically defined configurations of surface exposed amino acids on HLA molecules that require verification to confirm that they can be recognized by alloantibodies and are therefore clinically relevant. In this study, we isolated HLA-DQ specific memory B cells from immunized individuals by using biotinylated HLA-DQ monomers to generate 15 recombinant human HLA-DQ specific monoclonal antibodies (mAb) with six distinct specificities. Single antigen bead reactivity patterns were analyzed with HLA-EMMA to identify amino acids that were uniquely shared by the reactive HLA alleles to define functional epitopes which were mapped to known eplets. The HLA-DQB1*03:01-specific mAb LB_DQB0301_A and the HLA-DQB1*03-specific mAb LB_DQB0303_C supported the antibody-verification of eplets 45EV and 55PP respectively, while mAbs LB_DQB0402_A and LB_DQB0602_B verified eplet 55R on HLA-DQB1*04/05/06. For three mAbs, multiple uniquely shared amino acid configurations were identified, warranting further studies to define the inducing functional epitope and corresponding eplet. Our unique set of HLA-DQ specific mAbs will be further expanded and will facilitate the in-depth analysis of HLA-DQ epitopes, which is relevant for further studies of HLA-DQ alloantibody pathogenicity in transplantation.

Highlights

Chronic rejection remains a leading cause of graft loss in long-term renal transplant recipients and is associated with development of de novo donor-specific antibodies [1,2,3]
human leukocyte antigen (HLA) specificity in the serum of the immunized subjects and HLA specificity of the generated HLA-DQ-specific monoclonal antibodies (mAb) was confirmed by single antigen bead (SAB) analysis (Supplementary Figure 1), which demonstrated that all mAbs were directed against the beta chain of the HLA-DQ molecule and none were cross-reactive against HLA-DR or HLA-DP alleles
When multiple mAbs with identical reactivity patterns were generated from one individual, only one mAb will be discussed in detail

Summary

Introduction

Chronic rejection remains a leading cause of graft loss in long-term renal transplant recipients and is associated with development of de novo donor-specific antibodies (dnDSA) [1,2,3]. Most HLA matching algorithms are restricted to HLA-A, -B and -DR on HLA-DQ Epitope Analysis by Monoclonal Antibodies the serological antigen level, whereas dnDSA directed against HLA-DQ are the most prevalent after transplantation and have been associated with rejection, transplant glomerulopathy and allograft loss [4,5,6,7,8,9]. A residual effect of non-antibody-verified HLA-DQ mismatches on graft loss has been demonstrated [28], indicating that there are still immunogenic HLA-DQ eplets that have not yet been antibody-verified. Identification of clinically relevant HLA-DQ eplets would be instrumental for a better assessment of immunological risk in transplant patients and facilitate personalized medicine such as personalized immunosuppressive drug dosing [16, 29, 30]

Methods

Results

Conclusion