In HLA-incompatible kidney transplantation, monitoring donor-specific antibodies (DSA) plays a crucial role in providing appropriate treatment and increases kidney survival times. This work aimed to determine if early post-transplant DSA dynamics inform graft outcome over and above other predictive factors. Eighty-eight cases were classified by unsupervised machine learning into five distinct DSA response groups: no response, fast modulation, slow modulation, rise to sustained and sustained. Fast modulation dynamics gave an 80% rate for early acute rejection, whereas the sustained group was associated with the lowest rejection rates (19%). In complete contrast, the five-year graft failure was lowest in the modulation groups (4-7%) and highest in the sustained groups (25-31%). Multivariable analysis showed that a higher pre-treatment DSA level, male gender and absence of early acute rejection were strongly associated with a sustained DSA response. The modulation group had excellent five-year outcomes despite higher rates of early rejection episodes. This work further develops an understanding of post-transplant DSA dynamics and their influence on graft survival following HLA-incompatible kidney transplantation.

• Frontiers Media SA
• Europe PubMed Central
• PubMed Central

BACKGROUND:

Patients who are HLA-sensitized are at high risk for early antibody-mediated rejection (AMR) and worse outcomes. Therefore, it is crucial to detect the presence of donor-specific antibodies (DSAs) using pretransplant antibody identification and crossmatch assays. An error in antibody identification can lead to disastrous clinical outcomes. We present a case of acute AMR associated with preformed HLA-DPα and HLA-DPβ DSAs that were not identified before transplantation.

CASE PRESENTATION:

A 27-year-old woman received a second kidney transplant from a deceased donor. Her pretransplant panel-reactive antibody level was 94%. The complement-dependent cytotoxicity crossmatch was negative for T and B cells at the time of transplantation. She experienced early acute AMR proven by a kidney biopsy. Single antigen bead testing of the patient's serum at the time of rejection as well as the pre-second transplant serum revealed strong antibodies against the DPA1*01:03 and DPB1*02:01 alleles in the second donor. These antibodies were not identified by phenotypic bead assay during the patient's time on the waiting list. The patient was treated with plasmapheresis and anti-thymocyte globulin. However, she experienced abdominal pain on day 37 post-transplantation. Surgical exploration revealed a laceration on the transplanted kidney, which was then repaired. Subsequently, infected hematoma was suspected and the transplanted kidney was removed.

CONCLUSION:

The present case highlights the clinical significance of preformed HLA-DPα and HLA-DPβ DSAs. Accuracy in determination of HLA antibodies before transplantattion is critical for transplant outcome. HLA-DP typing and single antigen bead testing are recommended for a precise antibody interpretation, especially in highly sensitized patients. Careful interpretation of antibody testing results is essential for the success of organ transplantation.

• Europe PubMed Central
• PubMed Central
• BioMed Central

BACKGROUND:

Highly sensitized (HS) anti-HLA patients awaiting kidney transplantation benefit from specific allocation programs. Serological monitoring at 3-mo intervals is recommended to prevent unexpected positive crossmatch (XM), but this strategy is not evidence-based. Therefore, we assessed its relevance when using single-antigen flow bead (SAFB) and screening flow bead (SFB) assays.

METHODS:

We included 166 HS patients awaiting a transplant and assessed their SAFB profile during the year preceding their inclusion. Anti-HLA antibodies were evaluated by SAFB assay and compared within patients as serum pairs at 3, 6, and 9 mo. We assessed the performance of SFB for detecting changes in SAFB profiles with 35 serum pairs.

RESULTS:

On comparing 354, 218, and 107 serum pairs at 3, 6, and 9 mo, respectively, only 0.6%, 0.7%, and 1% of all antigens tested exceeded for the first time the unacceptable antigen threshold (mean fluorescence intensity ≥2000) in the most recent sample. Irrespective of the follow-up period, the calculated panel-reactive antibodies increased by a mean of 1%, and there was no significant increase in the proportion of donors at risk for positivity of flow- or complement-dependent cytotoxicity XM. The SFB did not accurately detect the variations of SAFB profiles.

CONCLUSIONS:

Changes in HS patient profiles are anecdotal and show little association with transplant access or risk for positive XM. Less-frequent monitoring in HS patients should be considered to improve cost-effectiveness without affecting transplant safety.

• Wolters Kluwer
• Ovid Technologies, Inc.

The IgG-degrading enzyme derived from Streptococcus pyogenes (Imlifidase, Hansa Biopharma) is a novel agent that cleaves all four human subclasses of IgG and has therapeutic potential for HLA desensitization in kidney transplantation and antibody-mediated rejection. Data from clinical trials in kidney transplantation demonstrated rapid degradation of anti-HLA donor-specific antibodies facilitating HLA-incompatible transplantation, which led to conditional approval of imlifidase by the European Medicines Agency for desensitization in kidney transplant recipients of a deceased donor with a positive cross match. Important considerations arising from the early experiences with imilfidase on kinetics of donor-specific antibodies after administration, timing of complementary therapeutic monoclonal or polyclonal IgG antibodies, and interference with cross match assays should be recognized as imlifidase emerges as a therapeutic agent for clinical transplantation.

• Europe PubMed Central
• PubMed Central

• Wiley
• Ovid Technologies, Inc.

BACKGROUND:

Imlifidase is an immunoglobulin G (IgG)-specific protease conditionally approved in the EU for desensitization in highly sensitized crossmatch positive kidney transplant patients. Imlifidase efficiently cleaves both heavy chains of IgG in a 2-step process. However, low levels of the intermediate cleavage product, single-cleaved IgG (scIgG), may persist in the circulation. The study objective was to investigate Fc-mediated effector functions of scIgG and its potential impact on common clinical immunologic assays used to assess transplant eligibility.

METHODS:

Imlifidase-generated scIgG, obtained by in vitro cleavage of HLA-sensitized patient serum or selected antibodies, was investigated in different complement- and FcγR-dependent assays and models, including clinical tests used to evaluate HLA-specific antibodies.

RESULTS:

ScIgG had significantly reduced Fc-mediated effector function compared with intact IgG, although some degree of activity in complement- and FcγR-dependent models was still detectable. A preparation of concentrated scIgG generated from a highly HLA-sensitized individual gave rise to a positive signal in the anti-HLA IgG LABScreen, which uses anti-Fc detection, but was entirely negative in the C1qScreen. The same high-concentration HLA-binding scIgG preparation also generated positive complement-dependent cytotoxicity responses against 80%-100% of donor T and B cells, although follow-up titrations demonstrated a much lower intrinsic activity than for intact anti-HLA IgG.

CONCLUSIONS:

ScIgG has a significantly reduced capacity to mediate Fc-dependent effector functions. However, remaining HLA-reactive scIgG in plasma after imlifidase treatment can cause positive assay results equivalent to intact IgG in clinical assays. Therefore, complete IgG cleavage after imlifidase treatment is essential to allow correct decision-making in relation to transplant eligibility.

• Europe PubMed Central
• PubMed Central

• Wolters Kluwer
• Ovid Technologies, Inc.

The presence of anti-HLA antibodies is an increasing challenge in kidney transplantation. Tocilizumab (TCZ), a monoclonal antibody targeting the interleukin-6 receptor (IL-6R), has been proposed to complement conventional desensitization therapy. We aimed to describe TCZ plasma trough concentrations and their variability and to investigate the link between TCZ concentration and the evolution of anti-HLA antibodies. Sensitized kidney-transplant candidates treated monthly with TCZ (8 mg/kg) for desensitization were retrospectively included. TCZ concentrations were determined by liquid chromatography-tandem mass spectrometry. Seventy-four TCZ concentrations from 10 patients were analyzed. The TCZ trough concentration ranged from <1.0 to 52.5 mg·L-1, with a median of 25.6 mg·L-1 [25th-75th percentiles: 13.2-35.3 mg·L-1). The inter- and intra-individual coefficients of variation were 55.0% and 33.0%, respectively. The TCZ trough concentration was not related to IL-6 (rho = -0.46, p = 0.792), soluble IL-6R (rho = -0.81, p = 0.65) concentrations or reduction of anti-HLA antibodies (mixed-effects model adjusting, effect of TCZ trough concentration: rho = -0.004, p = 0.26). The individual median TCZ concentration tended to be associated with the number of antibodies, with an initial MFI > 3000 that dropped to <3000 after TCZ treatment (rho = 0.397, p = 0.083). TCZ trough concentrations in kidney-transplant candidates treated for desensitization were highly variable. Further studies on larger cohorts are needed to study the possible link between TCZ concentrations and the reduction of anti-HLA antibodies.

• Europe PubMed Central
• PubMed Central
• MDPI

Kidney transplant candidates (KTCs) who are HLA highly sensitized (calculated panel-reactive alloantibodies >95%) have poor access to deceased kidney transplantation. In this single-center prospective study, 13 highly sensitized desensitization-naïve KTCs received IV tocilizumab (8 mg/kg) every 4 weeks. We evaluated tolerability as well as immune responses, that is, T cell, B cell, T follicular helper (Tfh) subsets, blood cytokines (IL-6, soluble IL-6 receptor-sIL-6R-, IL-21), blood chemokines (CXCL10, CXCL13), and anti-HLA alloantibodies. Tocilizumab treatment was well-tolerated except in one patient who presented spondylodiscitis, raising a note of caution. Regarding immune parameters, there were no significant changes of percentages of lymphocyte subsets, that is, CD3+ , CD3+ /CD4+ , CD3+ /CD8+ T cells, and NK cells. This was also the case for Tfh cell subsets, B cells, mature B cells, plasma cells, pre-germinal center (GC) B cells, and post-GC B cells, whereas we observed a significant increase in naïve B cells (p = .02) and a significant decrease in plasmablasts (p = .046) over the tocilizumab treatment course. CXCL10, CXCL13, IL-21, total IgG, IgA, and IgM levels did not significantly change during tocilizumab therapy; conversely, there was a significant increase in IL-6 levels (p = .03) and a huge increase in sIL-6R (p = .00004). There was a marginal effect on anti-HLA alloantibodies (class I and class II). To conclude in highly sensitized KTCs, tocilizumab as a monotherapy limited B cell maturation; however, it had almost no effect on anti-HLA alloantibodies.

• Ovid Technologies, Inc.

BACKGROUND:

There is no standard definition for "HLA incompatible" transplants. For the first time, we systematically assessed how HLA incompatibility was defined in contemporary peer-reviewed publications and its prognostic implication to transplant outcomes.

METHODS:

We combined 2 independent searches of MEDLINE, EMBASE, and the Cochrane Library from 2015 to 2019. Content-expert reviewers screened for original research on outcomes of HLA-incompatible transplants (defined as allele or molecular mismatch and solid-phase or cell-based assays). We ascertained the completeness of reporting on a predefined set of variables assessing HLA incompatibility, therapies, and outcomes. Given significant heterogeneity, we conducted narrative synthesis and assessed risk of bias in studies examining the association between death-censored graft failure and HLA incompatibility.

RESULTS:

Of 6656 screened articles, 163 evaluated transplant outcomes by HLA incompatibility. Most articles reported on cytotoxic/flow T-cell crossmatches (n = 98). Molecular genotypes were reported for selected loci at the allele-group level. Sixteen articles reported on epitope compatibility. Pretransplant donor-specific HLA antibodies were often considered (n = 143); yet there was heterogeneity in sample handling, assay procedure, and incomplete reporting on donor-specific HLA antibodies assignment. Induction (n = 129) and maintenance immunosuppression (n = 140) were frequently mentioned but less so rejection treatment (n = 72) and desensitization (n = 70). Studies assessing death-censored graft failure risk by HLA incompatibility were vulnerable to bias in the participant, predictor, and analysis domains.

CONCLUSIONS:

Optimization of transplant outcomes and personalized care depends on accurate HLA compatibility assessment. Reporting on a standard set of variables will help assess generalizability of research, allow knowledge synthesis, and facilitate international collaboration in clinical trials.

• Wolters Kluwer
• Ovid Technologies, Inc.

We investigated whether HLA class II eplet mismatch was related to dnDSA development and analyzed its combined impact with tacrolimus levels for kidney transplantation outcomes. A total of 347 kidney transplants were included. HLA Matchmaker was used for the single molecular eplet, total eplet, antibody (Ab)-verified eplet mismatch analyses, and Ab-verified single molecular analysis to identify HLA-DR/DQ molecular thresholds for the risk of dnDSA development. A time-weighted tacrolimus trough level (TAC-C0) of 5 ng/mL and a TAC-C0 time-weighted coefficient variability (TWCV) of 20% were applied to find the combined effects on dnDSA development. A high level of mismatch for single molecular eplet (DQ ≥ 10), total eplet (DQ ≥ 12), Ab-verified eplet (DQ ≥ 4), and Ab-verified single molecular eplet (DQ ≥ 4) significantly correlated with HLA class II dnDSA development. Class II dnDSA developed mostly in patients with low TAC-C0 and high eplet mismatch. In the multivariable analyses, low TAC-C0 and high eplet mismatch showed the highest hazard ratio for the development of dnDSA. No significant combined effect was observed in dnDSA development according to TWCV. In conclusion, the determination of HLA class II eplet mismatch may improve the risk stratification for dnDSA development, especially in conjunction with tacrolimus trough levels.

• Europe PubMed Central
• PubMed Central
• MDPI