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IntroductionAntibody mediated rejection (ABMR) is the most common cause of long-term allograft loss in kidney transplantation (KT). Therefore, a low human leukocyte antigen (HLA) mismatch (MM) load is favorable for KT outcomes. Hitherto, serological or low-resolution molecular HLA typing have been adapted in parallel. Here, we aimed to identify previously missed HLA mismatches and corresponding antibodies by high resolution HLA genotyping in a living-donor KT cohort.Methods103 donor/recipient pairs transplanted at the University of Leipzig Medical Center between 1998 and 2018 were re-typed using next generation sequencing (NGS) of the HLA loci -A, -B, -C, -DRB1, -DRB345, -DQA1, -DQB1, -DPA1, and -DPB1. Based on these data, we compiled HLA MM counts for each pair and comparatively evaluated genomic HLA-typing with pre-transplant obtained serological/low-resolution HLA (=one-field) typing results. NGS HLA typing (=two-field) data was further used for reclassification of de novo HLA antibodies as “donor-specific”.ResultsBy two-field HLA re-typing, we were able to identify additional MM in 64.1% (n=66) of cases for HLA loci -A, -B, -C, -DRB1 and -DQB1 that were not observed by one-field HLA typing. In patients with biopsy proven ABMR, two-field calculated MM count was significantly higher than by one-field HLA typing. For additional typed HLA loci -DRB345, -DQA1, -DPA1, and -DPB1 we observed 2, 26, 3, and 23 MM, respectively. In total, 37.3% (69/185) of de novo donor specific antibodies (DSA) formation was directed against these loci (DRB345 ➔ n=33, DQA1 ➔ n=33, DPA1 ➔ n=1, DPB1 ➔ n=10).ConclusionOur results indicate that two-field HLA typing is feasible and provides significantly more sensitive HLA MM recognition in living-donor KT. Furthermore, accurate HLA typing plays an important role in graft management as it can improve discrimination between donor and non-donor HLA directed cellular and humoral alloreactivity in the long range. The inclusion of additional HLA loci against which antibodies can be readily detected, HLA-DRB345, -DQA1, -DQB1, -DPA1, and -DPB1, will allow a more precise virtual crossmatch and better prediction of potential DSA. Furthermore, in living KT, two-field HLA typing could contribute to the selection of the immunologically most suitable donors.

Membranous nephropathy (MN) constitutes a major cause of nephrotic syndrome (NS) in adults. After kidney transplantation (KTx), both recurrent and de novo MN has been reported. In addition to PLA2R and THSD7A, recent identification of neural EGFL-like-1 protein, NELL1, as a potential disease antigen has enriched our understanding of MN pathogenesis. To date, NELL1-positive MN has only been described in native kidneys, but never been diagnosed in renal allografts. We here report on a 56-year-old male kidney transplant recipient suffering from amyotrophic lateral sclerosis (ALS), who developed NS 25 years after KTx. Allograft biopsy revealed NELL1-positive MN. Using specifically established immunoblotting techniques, we detected new-onset NELL1-IgG1, IgG3, and IgG4 antibodies in the patient´s serum correlating with the course of proteinuria. While primary renal disease was undetermined, MN recurrence seemed unlikely given the long-time span since KTx. By clinical investigation of de novo etiologies, we did not detect an underlying malignancy. However, previous self-medication with dimercaptopropane sulfonate (DMPS) and alpha lipoic acid (ALA) represented a potential trigger and cessation associated with partial remission of proteinuria. This report illustrates the first case of posttransplant NS due to NELL1-positive MN. Monitoring NELL1 antibodies in the serum promise to be a non-invasive diagnostic tool guiding disease management.

The safety of direct oral anticoagulants (DOACs) in patients after solid organ transplantation (SOT) is not well defined. This study aimed at describing the safety and efficacy of DOACs in patients after SOT. Patients after kidney and/or liver transplantation under maintenance immunosuppression treated with rivaroxaban (n = 26), apixaban (n = 20) and edoxaban (n = 1) were included. Clinical data were collected retrospectively and using a questionnaire. DOAC plasma levels and thrombin generation (TG) were measured in patients after SOT and compared with nontransplanted controls receiving DOACs. DOACs were administered for 84.6 patient-years. Mean immunosuppressive trough levels after DOAC initiation increased from baseline by 18.8 ± 29.6% compared to 3.0 ± 16.5% in matched controls (P = 0.004), without significant differences in dose adjustments. No transplant rejection or significant change in liver or renal function was observed. There was one major bleeding after the observation period but no thromboembolic complication. DOAC plasma levels reached the expected range in all patients. The intrinsic hemostatic activity in transplanted patients was higher compared to nontransplant controls. Treatment with DOACs after SOT is safe and effective. Immunosuppressive trough levels should be monitored after DOAC initiation, particularly in the early phase after SOT. These data should be confirmed in a prospective study.

End-stage renal disease (ESRD) of undetermined etiology is highly prevalent and constitutes a significant clinical challenge, particularly in the context of kidney transplantation (KT). Despite the identification of numerous rare hereditary nephropathies over the last few decades, patients with undetermined ESRD are not being systematically investigated for rare genetic causes in clinical practice. To address this, we utilized mutation analysis in patients on the kidney transplant waitlist and scrutinized underlying renal diagnoses of 142 patients in a single center KT-waitlist. This cohort was stratified into 85 cases of determined and 57 cases of undetermined ESRD. The latter patients were analyzed by a renal gene panel for mutations in 209 genes associated with ESRD. The most likely genetic diagnoses in 12% of the tested individuals with undetermined ESRD were established. All of these patients showed mutations in genes encoding components of the glomerular filtration barrier. Taken together, hereditary nephropathies, including autosomal dominant polycystic kidney disease, were identified in 35 of the 142 patients of the waitlist cohort. By significantly increasing the proportion of hereditary diagnoses from 29 to 35 patients, the rate of undetermined ESRD significantly decreased from 57 to 51 patients. This study demonstrates the beneficial use of genetic diagnostics in significantly unraveling undetermined ESRD cases prior to KT. Thus, in the absence of renal histology or the presence of unspecific histological conditions, such as hypertensive nephrosclerosis, focal segmental glomerulosclerosis or thrombotic microangiopathy, genetic analysis may provide a robust and specific renal diagnosis and allow for optimizing pre- and post-KT management.

Liver graft steatosis has not been noninvasively evaluated yet. We therefore characterized liver transplant recipients by transient elastography (TE) and controlled attenuation parameter (CAP) and correlated the results with clinical and genetic risk factors.A total of 204 patients (pretransplant disease: n = 102 nonalcoholic etiology, nonalcoholic liver cirrhosis (non-ALC); n = 102 alcoholic liver disease, ALC; 42% female; median age 57.8 years; median time since transplantation 66 months) underwent ultrasound, TE, CAP, and nonalcoholic fatty liver disease (NAFLD) fibrosis score. Recipient DNA samples were genotyped for patatin-like phospholipase domain-containing protein 3 (PNPLA3) (rs738409) and IL28B (rs8099917, rs12979860) polymorphisms.Increased hepatic echogenicity at ultrasound was observed in 36% of patients, CAP values252 and300 dB/m indicated steatosis and advanced steatosis in 44% and 24% of individuals. Advanced fibrosis (TE7.9 kPa) was associated with increased CAP results (266 vs. 229 dB/m, p = 0.012). PNPLA3 G-allele carriers had increased CAP values (257 vs. 222 dB/m, p = 0.032), higher liver stiffness (TE 6.4 vs. 5.5 kPa, p = 0.005), and prevalence of diabetes mellitus (40% vs. 22%, p = 0.016). No such association was observed for IL28B polymorphisms. ALC compared to non-ALC patients had higher body mass index (28.1 vs. 25.5 kg/m², p0.001), higher prevalence of diabetes mellitus (41% vs. 25%, p = 0.017), and PNPLA3 CG + GG genotype (73% vs. 47%, p = 0.006), and had elevated TE (6.3 vs. 5.4 kPa, p = 0.022), CAP (266 vs. 221 dB/m, p = 0.001), and NAFLD fibrosis score (score -0.5 vs. -1.3, p0.001).Modern noninvasive liver graft assessment frequently detects hepatic steatosis, which is associated with graft fibrosis, components of the metabolic syndrome and recipient PNPLA3 rs738409 genotype, especially in ALC patients.