Molecular diagnosis of antibody-mediated rejection: Evaluating biopsy-based transcript diagnostics in the presence of donor-specific antibodies but without microvascular inflammation, a single-center descriptive analysis.

Biopsy-based transcript diagnostics may identify molecular antibody-mediated rejection (AMR) when microvascular inflammation (MVI) is absent. In this single-center cohort, biopsy-based transcript diagnostics were validated in 326 kidney allograft biopsies. A total of 71 histological AMR and 35 T cell-mediated rejection (TCMR) cases were identified as molecular AMR and TCMR in 55% and 63%, respectively. Among 121 cases without MVI (glomerulitis + peritubular capillaritis = 0), 45 (37%) donor-specific antibody (DSA)-positive and 76 (63%) DSA-negative cases were analyzed. Twenty-one out of the 121 (17%) cases showed borderline changes, or TCMR, while BK nephropathy was excluded. None of the 45 DSA-positive patients showed molecular AMR. Among 76 DSA-negative patients, 2 had mixed molecular AMR/TCMR. All-AMR phenotype scores (sum of R4-R6) exhibited median values of 0.13 and 0.12 for DSA-positive and DSA-negative patients, respectively (P = .84). A total of 13% (6/45) DSA-positive and 11% (8/76) DSA-negative patients showed an all-AMR phenotype score > 0.30 (P = .77). Patients with a higher all-AMR phenotype score showed 33% more histologic TCMR (P = .005). The median all-AMR phenotype scores of glomerular basement membrane double contours = 0 and glomerular basement membrane double contours > 0 biopsies were 0.12 and 0.10, respectively (P = .35). Biopsy-based transcript diagnostics did not identify molecular AMR in cases without MVI. Follow-up biopsies and outcome data should evaluate the clinical relevance of subthreshold molecular alterations.

Limitations of biopsy-based transcript diagnostics to detect T cell-mediated allograft rejection.

BACKGROUND AND HYPOTHESIS: Isolated Tubulitis, Borderline Changes, and Isolated Arteritis suspicious for histologic T cell-mediated rejection (hTCMR) remain findings of uncertain significance. Although the Molecular Microscope Diagnostics System (MMDx) has not been trained on those lesions, it was suggested that MMDx might reclassify a subgroup to molecular TCMR (mTCMR). METHODS: In this single-center cohort of 326 consecutive, unselected kidney allograft biopsies assessed by histology and MMDx, we analyzed 249 cases with Isolated Tubulitis (i0, t1-3, v0; n=101), Borderline Changes (according to Banff 2022, v0; n=9), Isolated Arteritis (no borderline, v1; n=37), No Inflammation (i0, t0, v0; n=67) and a Positive Control Cohort (hTCMR, n=27; Mixed histologic Rejection, n=8; both according to Banff 2022; total n=35). The first three groups were summarized as TCMR-Suspicion (n=147). Subcategorization included the presence and absence of microvascular inflammation (MVI; g+ptc≥2). Molecular rejection rates and differentiation were investigated. RESULTS: Molecular rejection rates were 37/147 cases (25.2%; 32 with MVI) in TCMR-Suspicion, 6/67 (9%; 4 with MVI) in No Inflammation and 30/35 (85.7%; 19 with MVI) in the Positive Control Cohort. Molecular antibody-mediated rejection (mAMR) was present in 39/73 (53.4%) of cases. The presence of donor-specific antibodies (DSA) at the time of the biopsy was high (127/249, 51%). Only 3 mAMR/TCMR and no pure mTCMR cases were detected in TCMR-Suspicion and No Inflammation, compared to 12 mAMR/TCMR and 10 mTCMR cases in the Positive Control Cohort (p<0.001). Even though the TCMR-specific molecular (Classifier) score differentiated between TCMR-Suspicion and No Inflammation (p=0.005), rejection phenotype scores (R2 and R3) did not (p=0.157 and 0.121). CONCLUSIONS: MMDx did not identify pure mTCMR among Isolated Tubulitis, Borderline Changes, or Isolated Arteritis, likely due to low sensitivity for TCMR-lesions. However, it identified mAMR or mAMR/TCMR, especially in cases with MVI. Subthreshold findings remain to be further studied.

Therapeutic Drug Monitoring of Mycophenolic Acid Identifies Kidney Transplant Recipients Responsive to Two SARS-CoV-2 mRNA Vaccine Doses.

Immune-responsiveness to SARS-CoV-2 mRNA vaccination is reduced in kidney transplant recipients (KTRs). Previous reports point to a role of mycophenolic acid (MPA). Our observational cohort study included all KTRs at University Hospital Zurich receiving two SARS-CoV-2 mRNA vaccine doses more than 6 months post-transplantation, who were assessed by measuring anti-spike immunoglobulin G (IgG). We applied principles of therapeutic drug monitoring (TDM) to correlate MPA exposure and lymphocyte counts with SARS-CoV-2 IgG. MPA trough levels differ largely among KTRs with a median of 3.1 mg/L (range 0.7-9.5 mg/L). 34 of 84 KTRs (40%) developed positive SARS-CoV-2 IgG after two vaccine doses. KTRs who developed positive SARS-CoV-2 IgG showed significantly higher eGFR (p < 0.001), lower MPA trough levels (p < 0.001) and higher CD19+ lymphocytes (p < 0.001). MPA trough levels <2.5 mg/l and CD19+ lymphocytes >40/µl identify KTRs with seroconversion. Upon logistic regression, MPA trough levels <2.5 mg/L were associated with a 7-fold (CI 95%: 1.589-29.934) and ciclosporin use with a 6-fold (CI 95%: 1.148-30.853) increase in the odds of seroconversion. Our study indicates that immune-responsiveness to SARS-CoV-2 mRNA vaccines correlates with MPA exposure measured by MPA trough level but argues against a class effect of MPA. TDM-guided MPA dosing may be a strategy to increase seroconversion rate.

Association between PIRCHE-II scores and de novo allosensitization after reduction of immunosuppression during SARS-CoV-2 infection in kidney transplant recipients.

BACKGROUND: Before the availability of mRNA vaccines, many transplant centers chose to significantly reduce maintenance immunosuppression in kidney transplant recipients (KTRs) with SARS-CoV-2 infection. The extent to which this increases the risk of allosensitization is unclear. METHODS: In this observational cohort study, we analyzed 47 KTRs from March 2020 to February 2021 who underwent substantial reduction of maintenance immunosuppression during SARS-CoV-2 infection. KTRs were followed at 6 and 18 months concerning the development of de novo donor-specific anti-HLA (human leukocyte antigen) antibodies (DSA). The HLA-derived epitope mismatches were calculated using the predicted indirectly recognizable HLA-epitopes (PIRCHE-II) algorithm. RESULTS: In total, 14 of 47 KTRs (30%) developed de novo HLA antibodies after the reduction of maintenance immunosuppression. KTRs with higher total PIRCHE-II scores and higher PIRCHE-II scores for the HLA-DR locus were more likely to develop de novo HLA antibodies (p = .023, p = .009). Furthermore, 4 of the 47 KTRs (9%) developed de novo DSA after reduction of maintenance immunosuppression, which were exclusively directed against HLA-class II antigens and also showed higher PIRCHE-II scores for HLA-class II. The cumulative mean fluorescence intensity of 40 KTRs with preexisting anti-HLA antibodies and 13 KTRs with preexisting DSA at the time of SARS-CoV-2 infection remained stable after the reduction of maintenance immunosuppression (p = .141; p = .529). CONCLUSIONS: Our data show that the HLA-derived epitope mismatch load between donor and recipient influences the risk of de novo DSA development when immunosuppression is temporarily reduced. Our data further suggest that reduction in immunosuppression should be made more cautiously in KTRs with high PIRCHE-II scores for HLA-class II antigens.

Use of letermovir-valganciclovir combination as a step-down treatment after foscarnet for ganciclovir-resistant CMV infection in kidney transplant recipients.

BACKGROUND: Letermovir (LTV) might be an alternative treatment to nephrotoxic foscarnet (FOS) in Ganciclovir (GCV) resistant cytomegalovirus (CMV) infection. However, its efficacy in controlling active CMV viremia is unclear, as it is only approved for CMV prophylaxis in hematopoietic stem-cell transplantation. METHODS: This case series describes 14 kidney transplant recipients (KTR) with moderate-level GCV resistant CMV infection, treated by different step-down strategies after initial FOS therapy: (1) Observation without antiviral follow-up or switch to valganciclovir (VGCV) (pre-LTV era), and (2) Switch to LTV±VGCV (LTV era). RESULTS: One patient died under FOS. Thirteen patients were followed under step-down regimens. All but two patients had ongoing CMV viremia when stopping FOS. In pre-LTV era, 5/9 (56%) experienced a CMV breakthrough > 10 000 IU/ml calling for another course of FOS, as compared to 1/4 (25%) in the LTV era. Addition of VGCV to LTV at low-level viral breakthrough, addressing a possible developing resistance against LTV, prevented viral surge in two patients. In the pre-LTV era, CMV-related death or graft loss occurred in three of nine (33%), compared to no death or graft loss in the LTV era. CONCLUSION: A step-down strategy combining LTV+VGCV, might allow to safely stop FOS at ongoing low-level viremia.

Ten tips from the Swiss Working Group on Sustainable Nephrology on how to go green in your dialysis unit.

The health-care system and particularly renal replacement therapy has a significant carbon footprint adding to global warming and extreme weather conditions. Improving sustainability has become the focus of national and international working groups. Many reviews underline the need for improvement of sustainability in nephrology, in particular dialysis, and provide recommendations on how to reduce waste, energy, and water consumption. However, how to implement these recommendations, and where to start, is not always clear. This paper summarizes discussions within the 'working group on sustainable nephrology' of the Swiss Society of Nephrology. We do not provide a detailed review of the topic but instead present a practical 10-point action plan to help health-care workers in nephrology make a start and improve the carbon footprint of their dialysis centres. We emphasize the importance of ongoing research, cooperation, and dialogue, and welcome additional ideas from the wider renal community.

[Symptom Control in Nephrological Palliative Care].

INTRODUCTION: Nephrology may have quite a lot in common with with palliative care. Examples of this are the conservative therapy of a terminal chronic kidney disease or dialysis termination. Nevertheless, palliative co-care of patients with chronic kidney disease still happens rather rarely. On the one hand, this might be due to lacking experience regarding the benefits and opportunities of incorporating palliative care in nephrology care, on the other hand, palliative care is often misunderstood as pure "end-of-life" care. By highlighting the whole spectrum of palliative care, we aim to promote these two disciplines in order to integrate palliative care services into the nephrological treatment concept at an early stage.

The Spleen Plays No Role in Nephrotoxic Serum Nephritis, but Constitutes a Place of Compensatory Haematopoiesis.

BACKGROUND: The spleen has been implicated in the pathogenesis of immune-complex glomerulonephritis by initiating and resolving adaptive immune responses. Thus, we aimed to evaluate the role of the spleen in experimental nephrotoxic serum nephritis (NTS). METHODS: In order to accelerate the disease, animals were subjected to NTS by preimmunizing male C57BL/6J mice with rabbit IgG three days before injecting the rabbit anti-glomerular basement antiserum, or were immunized only. A group underwent splenectomy before NTS induction. RESULTS: We observed enlargement of the spleen with a maximum at 14 days after NTS induction or immunization only. Splenectomized mice were found to develop albuminuria and renal histological changes comparable to sham-operated controls. Nevertheless, anaemia was aggravated in mice after splenectomy. During the course of NTS, we detected CD41+ megakaryocytes and Ter119+ erythroid precursor cells in the spleen of mice with NTS and of immunized mice. Ter119+Cxcr4+ cells and the binding partner Cxcl12 increased in the spleen, and decreased in the bone marrow. This was accompanied by a significant systemic increase of interferon-gamma in the serum. CONCLUSIONS: In summary, splenectomy does not influence the course of NTS per se, but is involved in concomitant anaemia. Extramedullary haematopoiesis in the spleen is probably facilitated through the migration of Cxcr4+ erythroid precursor cells from the bone marrow to the spleen via a Cxcl12 gradient and likely arises from the suppressive capacity of chronic inflammation on the bone marrow.