PLA2R-associated Membranous Nephropathy Research Articles

#2154 Rituximab in the treatment of PLA2R-associated membranous nephropathy: insights from a hospital centre experience

Abstract Background and Aims Rituximab (RTX) is recommended as the first-line therapy for PLA2R-associated Membranous Nephropathy in patients with a moderate to high risk of progressive loss of kidney function, according to the KDIGO 2021 guidelines. This recommendation is based on the superior long-term efficacy and improved safety profile of RTX. This study aims to assess the use of RTX for the treatment of for PLA2R-associated Membranous Nephropathy at a hospital centre. Method A retrospective study was conducted on patients diagnosed with PLA2R-associated Membranous Nephropathy who underwent their first RTX administration between 2017 and 2022 at a tertiary hospital centre. Exclusion criteria involved patients with less than 6 months of follow-up post-RTX. The study evaluated the occurrence of immune remission, clinical remission, as well as instances of immune and proteinuria relapse, and recorded any adverse events. Results A total of 11 patients were included, with 54.5% being male. The mean age was 60.4 ± 14.7 years, and the median disease duration 69.0 [8.0-87.0] months. The mean follow-up time post-RTX was 36.7 ± 23.3 months. Regarding the risk of progressive loss of kidney function, 8 patients were classified as high risk, 1 as moderate risk, and 2 as low risk. RTX served as the initial immunosuppressive therapy for only 3 patients. Additional immunosuppressive therapies post-RTX, including further RTX doses, were administrated in 63.6% (n = 7) of patients. No response was observed in 18.2% (n = 2). Immune remission was achieved in 81.8% (n = 9), mean time of 3.8 ± 1.4 months. Within this group 55.5% (n = 5) patients achieved complete remission, 22.2% (n = 2) experienced partial remission, and 22.2% (n = 2) maintained nephrotic proteinuria, with immune remission consistently preceding clinical remission. Relapses occurred in 45.5% (n = 5), at a mean time of 20.8 ± 13.5 months. Patients with lower serum albumin at time of RTX administration were more likely to experience non-response or relapse (T (9) = 2.51, p = 0.03), with a Youden Index cut-off of 3.2 g/dL, demonstrating a sensitivity of 100% and a specificity of 85.7%. Patients with anti-PLA2R exceeding 150 RU/mL exhibited no response or relapsed. Four patients (36.4%) remained free of relapses throughout the entire follow-up period, mean time of 22.8 ± 10.0 months, with 1 keeping RTX maintenance therapy. During the 6 months post-RTX, 36.4% (n = 4) of patients experienced adverse events. Conclusion Rituximab demonstrated both efficacy and safety in treating PLA2R-associated Membranous Nephropathy. However, lower serum albumin levels and anti-PLA2R > 150 RU/mL at time of RTX administration were associated with worse response. Given the substantial need for additional immunosuppression, and considering lower albumin values and higher anti-PLA2R titres as risk markers, it is recommended to closely monitor these patients. Anti-PLA2R titres showed a meaningful association with disease activity, preceding changes in proteinuria levels. Therefore, tracking disease progression through the measurement of anti-PLA2R titres not only guides clinical decisions but also enables a judicious approach to subsequent RTX administrations.

#932 Obinutuzumab for the treatment of refractory PLA2R-associated membranous nephropathy: a single-center cohort study

Abstract Background and Aims The established first-line immunosuppressive treatment for membranous nephropathy, rituximab, is met with resistance in some cases of refractory disease. Obinutuzumab, a Type II humanized CD20 monoclonal antibody, has been documented in international case reports as a potential treatment for refractory membranous nephropathy, yet application in China is in its infancy. This study aims to investigate the preliminary short-term efficacy and safety profile of obinutuzumab in such challenging cases. Method We assessed six adult patients with PLA2R-associated membranous nephropathy unresponsive to rituximab, prednisone combined with cyclophosphamide, and calcineurin inhibitors. Obinutuzumab was administered intravenously at 1000 mg, preceded by prophylactic dexamethasone and diphenhydramine to mitigate infusion reactions. Immunological remission was defined as a reduction of anti-PLA2R antibodies to titers below 2RU/ml. Results Baseline characteristics at the initiation of obinutuzumab treatment included an average disease duration of 3.6 ± 2.1 years and a median patient age of 54 years, with a male predominance (3:1 ratio). Laboratory findings at baseline revealed serum albumin at 22 ± 4 g/L, serum creatinine at 133 ± 68 μmol/L, and a significant 24-hour urinary protein quantification (24 hUP) at 7.1 ± 2.9 g/d. The median baseline anti-PLA2R antibody titer was substantial at 90 (range 50-671) RU/ml. At follow-up (9.1 ± 3.7 months), immunological remission rates post-obinutuzumab at 1, 3, and 6 months were 33.3%, 50%, and 50%, respectively. By the end of the study, CD19+ B-cells were depleted (< 5 cells/μL) for an average duration of 6.8 ± 2.6 months. At this juncture, improvements were noted with increased serum albumin (33 ± 8 g/L) and decreased serum creatinine (125 ± 80 μmol/L), along with a reduction in 24 hUP to 4.7 ± 6.2 g/L. Clinical evaluations indicated two cases of complete remission and two of partial remission. In the remaining two patients, 24 hUP was halved compared to baseline. Prednisone dosage was reduced to 7 ± 7 mg/day, with a corresponding reduction in cyclosporine and tacrolimus dosages, and cessation of cyclophosphamide and Tripterygium wilfordii polyglycosides. There were no acute infusion reactions, but two patients suffered severe infections, including one fatality, related to COVID-19 during the pandemic. Conclusion Obinutuzumab emerges as a novel agent in the immunosuppressive armamentarium against refractory PLA2R-associated membranous nephropathy, warranting further long-term study. The enduring B-cell depletion necessitates a careful pre-treatment risk assessment for opportunistic infections, particularly during the ongoing COVID-19 pandemic.

#992 Protocol based on PLA2R1 epitope recognition is superior to standard protocol in achieving remission in PLA2R1-associated membranous nephropathy

Abstract Background and Aims Membranous nephropathy (MN) is a rare, but severe autoimmune disease affecting kidney glomeruli. Clinical evolution is variable, ranging from spontaneous remission to persistent nephrotic syndrome and kidney failure. The major autoantigen in MN is PLA2R1 protein associated with 50-70% of all cases. Patients may present antibodies against a single immunodominant CysR domain or may develop additional antibodies against CTLD1 and/or CTLD7 and/or CTLD8 domains of PLA2R1 defining a cascade immunization or epitope spreading. The mechanism of epitope spreading has been described in a variety of contexts: it can reinforce immune response to eliminate a pathogen, but can also be associated with the aggravation of autoantibody-mediated autoimmune pathologies. The value of this marker in the management of MN patients remains debated. Our initial study (confirmed on an independent cohort) has shown that the single domain recognition (non-spreader patients) is associated with a higher chance of spontaneous remission (45% vs 0.05% in GEMRITUX cohort) and a better response to treatment (100% of remission regardless of the dose of rituximab used). The patients with multi domain recognition (spreader patients) of CTLD1 and/or CTLD7 domains, on the other hand, have poor prognosis and are less likely to achieve remission requiring high doses of rituximab. Based on these studies we have proposed a personalized treatment protocol with either low or high dose Rituximab based on patients’ PLA2R1 epitope spreading status. The aim of this study was to evaluate the efficacy of this personalized treatment in comparison to the established GEMRITUX protocol. Method A multicenter, randomized, controlled, prospective clinical trial was conducted in 12 French hospitals. Sixty-four consecutive patients with PLA2R1-related MN were randomly assigned to either the control group following the GEMRITUX protocol (symptomatic treatment for 6 months, two 375 mg/m2 rituximab infusions at month-6 in case of persistent nephrotic syndrome (NS)) or the personalized treatment (PMMN) group (patients with no epitope spreading at month-0 were treated as per GEMRITUX protocol, while patients with epitope spreading at month-0 or month-6 with persistent NS were treated immediately with two 1 g rituximab infusions). The primary study outcome was the rate of clinical remission at month-12. The secondary outcomes were complete and partial remission, immunological remission, proteinuria, albuminuria, serum creatinine, and PLA2R1 antibody titer. Results From 64 patients included, three were excluded from final analyses due to loss to follow-up. There was no difference in age, gender, albumin, UPCR, anti-PLA2R1 titer and the rate of PLA2R1 epitope spreading at baseline between the two groups. At M12, 34% of patients from the GEMRITUX group and 69% of patients from PMMN group achieved partial clinical remission (P = .0105) defined as UPCR < 3.5 g/g with a decrease greater than 50% from baseline; improvement or normalization of serum albumin; and increase of serum creatinine lower than 20%. While there was no difference in remission rate between the GEMRITUX group and PMMN group for patients with single domain recognition (38% vs 50%, respectively, P = .7107), multi-domain recognizers (spreaders) were more likely to achieve remission with personalized protocol (36% vs. 87%, P = .0078). The rate of complete clinical remission between the two experimental groups, defined as UPCR <0.3 g/g and normal albumin, was close to statistical significance (0% vs 16%, P = .0538). Conclusion Personalized treatment protocol based on the stratification of patients with PLA2R1-related MN according to their epitope spreading status, is superior to the standard GEMRITUX protocol in achieving partial clinical remission at 12 months. Patients with multiple domain recognition should be treated immediately with high doses of rituximab to increase their chances of remission.

#1649 Obinutuzumab is effective for the treatment of rituximab-resistant membranous nephropathy

Abstract Background and Aims Membranous nephropathy (MN) is a leading cause of nephrotic syndrome in nondiabetic adults. Rituximab has become the first-line therapy for patients with MN after the recognition of MN as an autoimmune disease. However, 40% of patients with MN do not respond to rituximab. Obinutuzumab is a humanized and glycoengineered type II anti-CD20 monoclonal antibody that has superior in vitro B-cell cytotoxicity compared with rituximab which might provide an attractive option for rituximab-resistant MN. We presented our single-center experience of treating MN with obinutuzumab. Method Fourteen patients with rituximab-resistant PLA2R-associated MN who received obinutuzumab at the First affiliated hospital of Xi'an Jiaotong university between January 2022 and June 2023 were included in this retrospective study. Resistance to rituximab was defined as the failure to achieve complete (urinary protein excretion <0.3 g/d along with normal serum albumin concentration and stable renal function) or partial (urinary protein excretion <3.5 g/d or with ≥50% reduction vs baseline, accompanied by improvement or normalization of serum albumin concentration and stable GFR) remission of NS in 3-6 months after 2 doses of rituximab administration. Clinical and laboratory parameters were evaluated at presentation, before and after obinutuzumab administration. Results Of all patients with an average age of 50.0 ± 13.6 years, 10 (71.4%) patients were men, 8 (57.1%) patients had hypertension and 4 (28.6%) patients had diabetes. The median disease duration was 1.3 (1.0, 4.8) years. At presentation, the proteinuria and albumin levels were 7.94 ± 4.23 g/d and 21.5 ± 3.6 g/L, respectively. The mean serum creatinine level was 70.5 ± 10.7 µmol/L and the patients had a median baseline anti-PLA2R level of 193.5 (104.5,299.2) RU/mL. Six patients had been previously exposed to steroids, alkylating agents, calcineurin inhibitors in different combinations in addition to rituximab. Both patients received 1 g of obinutuzumab on day 0 and day 15. At obinutuzumab administration, the proteinuria and albumin levels were 8.43 ± 3.36 g/d and 22.4 ± 4.0 g/L, respectively. The mean serum creatinine level was 85.1 ± 28.5 µmol/L and median anti-PLA2R level decreased to 32.7 (10.7,178.) RU/mL compared with that at presentation. After a median follow-up of 5.4 (4.0, 9.7) months after obinutuzumab therapy, complete remission was achieved in 4 (28.6%) and partial remission was achieved in 8 (57.1%) of patients. Of the remaining two patients who did not achieve complete or partial remission, 1 patient had a follow-up of 4 months and had a 33% decline in proteinuria accompanied by improvement in serum albumin. The other patient had an anti-PLA2R level higher than 1500 RU/mL (exceeding detection upper limit) at obinutuzumab administration and an inadequate follow-up of 3 months without proteinuria decline. Whereas, anti-PLA2R level decreased to 18.17 RU/ml accompanied by B-lymphocyte depletion (absolute CD19 count <5 cells/ml) at that time. Of the 12 patients who achieved complete or partial remission, the median time from treatment to remission was 4.7 ± 2.3 months. Two patients with longer follow-up maintained complete remission at 1 year. At first complete or partial remission, the proteinuria and albumin levels were 3.47 ± 1.99 g/d and 32.5 ± 3.3 g/L, respectively. The mean serum creatinine level was 74.8 ± 24.1 µmol/L and anti-PLA2R levels of 11 patients had a decline in the titer to <2 RU/ml (negative result for our immunology laboratory). B-lymphocyte depletion was achieved in all these patients. Conclusion Obinutuzumab may represent an attractive alternative therapy in patients with resistance to rituximab. Larger prospective studies are needed to validate these findings.

Significance of the total renal chronicity score in predicting renal outcome in PLA2R-associated membranous nephropathy.

Phospholipase A2 receptor (PLA2R)-associated membranous nephropathy accounts for the majority of membranous nephropathy; however, few studies have determined the prognostic impact and clinicalapplication of renal pathologic change on this disease. A retrospective cohort study of 262 patients with PLA2R-associated membranous nephropathy was conducted. The total renal chronicity score calculatedaccording to the degree ofglomerulosclerosis, interstitial fibrosis, tubular atrophy, and arteriosclerosis was applied to evaluate renal chronicity. Baseline bias was adjusted by inverse probability weight whenassessing the prognostic impact of chronicity, and multiple parameters were used to evaluatethe application valueof renalchronicity. During a median follow-up of 24.5 months, renal outcome (kidney function deteriorationand/or end-stage kidney disease) was observed in 22 (8.40%) patients. Not only did a higher total renal chronicity score independently predict renal outcome [odds ratio (OR): 1.562, 95% confidence interval (CI) 1.073-2.273, P = 0.020], but non-minimal chronicity was also an independent risk factor for renal outcome (OR: 3.170, 95% CI 1.040-9.659, P = 0.042). Moreover, the membranous nephropathy risk classification in the Kidney Disease: Improving Global Outcomes (KDIGO) guideline integrated with non-minimal chronicity showed improvements in categorical net reclassification (0.174, 95% CI 0.012-0.335, P = 0.035), continuous net reclassification (0.462, 95% CI 0.087-0.838, P = 0.016), and integrated discrimination (0.019, 95% CI 0.003-0.035, P = 0.020) compared to the original classification. Renal chronicity is closely associated withrenal outcomes in PLA2R-associated membranous nephropathy, and combiningthe KDIGO risk classification with chronicity scoresmay provide amore accurate prognostic prediction.

Combined Serologic and Genetic Risk Score and Prognostication of Phospholipase A2 receptor-Associated Membranous Nephropathy.

The aim of this study was to test whether a combined risk score on the basis of genetic risk and serology can improve the prediction of kidney failure in phospholipase A2 receptor (PLA2R)-associated primary membranous nephropathy. We performed a retrospective analysis of 519 biopsy-proven PLA2R-associated primary membranous nephropathy patients with baseline eGFR ≥25 ml/min per 1.73 m 2 . The combined risk score was calculated by combining the genetic risk score with PLA2R ELISA antibody titers. The primary end point was kidney disease progression defined as a 50% reduction in eGFR or kidney failure. Cox proportional hazard regression analysis and C-statistics were applied to compare the performance of PLA2R antibody, genetic risk score, and combined risk score, as compared with clinical factors alone, in predicting primary outcomes. The median age was 56 years (range, 15-82 years); the male-to-female ratio was 1:0.6, the median eGFR at biopsy was 99 ml/min per 1.73 m 2 (range: 26-167 ml/min per 1.73 m 2 ), and the median proteinuria was 5.3 g/24 hours (range: 1.5-25.8 g/24 hours). During a median follow-up of 67 (5-200) months, 66 (13%) had kidney disease progression. In Cox proportional hazard regression models, PLA2R antibody titers, genetic risk score, and combined risk score were all individually associated with kidney disease progression with and without adjustments for age, sex, proteinuria, eGFR, and tubulointerstitial lesions. The best-performing clinical model to predict kidney disease progression included age, eGFR, proteinuria, serum albumin, diabetes, and tubulointerstitial lesions (C-statistic 0.76 [0.69-0.82], adjusted R 2 0.51). Although the addition of PLA2R antibody titer improved the performance of this model (C-statistic: 0.78 [0.72-0.84], adjusted R 2 0.61), replacing PLA2R antibody with the combined risk score improved the model further (C-statistic: 0.82 [0.77-0.87], adjusted R 2 0.69, difference of C-statistics with clinical model=0.06 [0.03-0.10], P < 0.001; difference of C-statistics with clinical-serologic model=0.04 [0.01-0.06], P < 0.001). In patients with PLA2R-associated membranous nephropathy, the combined risk score incorporating inherited risk alleles and PLA2R antibody enhanced the prediction of kidney disease progression compared with PLA2R serology and clinical factors alone.

Quantitative detection and prognostic value of antibodies against M-type phospholipase A2 receptor and its cysteine-rich ricin domain and C-type lectin domains 1 and 6-7-8 in patients with idiopathic membranous nephropathy.

M-type phospholipase A2 receptor (PLA2R) is the major autoantigen in adult idiopathic membranous nephropathy (IMN). Although reactive epitopes in the PLA2R domains have been identified, the clinical value of these domains recognized by anti-PLA2R antibodies remains controversial. Accordingly, this study aimed to quantitatively detect changes in the concentrations of different antibodies against epitopes of PLA2R in patients with IMN before and after treatment to evaluate the clinical value of epitope spreading. Highly sensitive time-resolved fluorescence immunoassay was used to quantitatively analyze the concentrations of specific IgG and IgG4 antibodies against PLA2R and its epitopes (CysR, CTLD1, CTLD6-7-8) in a cohort of 25 patients with PLA2R-associated membranous nephropathy (13 and 12 in the remission and non-remission groups, respectively) before and after treatment, and the results were analyzed in conjunction with clinical biochemical indicators. The concentration of specific IgG (IgG4) antibodies against PLA2R and its epitopes (CysR, CTLD1 and CTLD6-7-8) in non-remission group was higher than that in remission group. The multipliers of elevation of IgG (IgG4) antibody were 5.6(6.2) fold, 3.0(24.3) fold, 1.6(9.0) fold, and 4.2(2.6) fold in the non-remission/remission group, respectively. However, the difference in antibody concentrations between the two groups at the end of follow-up was 5.6 (85.2), 1.7 (13.1), 1.0 (5.1), and 1.5 (22.3) times higher, respectively. When detecting concentrations of specific IgG antibodies against PLA2R and its different epitopes, the remission rate was 66.67% for only one epitope at M0 and 36.36% for three epitopes at M0. When detecting concentrations of specific IgG4 antibodies against PLA2R and its different epitopes, the remission rate was 100.00% for only one epitope at M0 and 50.00% for three epitopes at M0. A trivariate logistic regression model for the combined detection of eGFR, anti-CTLD678 IgG4, and urinary protein had an AUC of 100.00%. Low concentrations of anti-CysR-IgG4, anti-CTLD1-IgG4, and anti-CTLD6-7-8-IgG4 at initial diagnosis predict rapid remission after treatment. The use of specific IgG4 against PLA2R and its different epitopes combined with eGFR and urinary protein provides a better assessment of the prognostic outcome of IMN.

Rituximab in the treatment of PLA2R-associated membranous nephropathy: Insights from a hospital centre experience

Rituximab in the treatment of PLA2R-associated membranous nephropathy: Insights from a hospital centre experience

Effect of rituximab in patients with PLA2R-associated membranous nephropathy and malignancy

IntroductionPhospholipase A2 receptor (PLA2R)-associated membranous nephropathy (MN) is a common cause of nephrotic syndrome in nondiabetic adults who are also within the common age group for malignancy. How to treat patients with PLA2R-associated MN and malignancy effectively and safely still requires careful consideration. The aim of our study was to examine the outcomes and safety of rituximab (RTX) in these patients. MethodsRetrospective analysis of clinical data was performed on 15 patients with PLA2R-associated MN and malignancy. Patients were followed every 1–3 months for a minimum of 24 months. Clinical data were collected, including CD19+ B cells, anti-PLA2R antibodies, 24-hour urinary protein, serum albumin, and serum creatinine. The percentage of patients who achieved clinical remission and immunological remission was also measured. ResultsAmong these 15 patients, 14 patients with solid tumors received treatment for malignant diseases with complete resection. One patient received chemotherapy for chronic myeloid leukemia, and achieved complete remission 36 months before the diagnosis of MN. There were 6 (40.00 %) patients who achieved complete remission and 14 (93.33 %) patients who achieved complete or partial remission at the last visit after RTX treatment. At the last visit, patients were clinically improved, as evidenced by significant improvements in anti-PLA2R antibody titer [2.00 (2.00, 2.00) vs 35.25 (11.18, 91.58) RU/ml, P = 0.002], 24-hour urine protein [0.39 (0.11, 2.28) vs 9.22 (4.47, 14.73) g/d, P = 0.001], and serum albumin [38.15 (34.80, 43.20) vs 23.70 (18.70, 25.70) g/L, P = 0.001]. During the follow-up, the renal function of those patients remained stable. Recurrence of malignant tumors or the occurrence of new tumor events were not observed. ConclusionIn this single-center retrospective study with a small sample size, RTX therapy might be an effective and safe treatment in patients with PLA2R-associated MN and malignancy.

Optimization of Rituximab Therapy in Adult Patients With PLA2R1-Associated Membranous Nephropathy With Artificial Intelligence

IntroductionRituximab is a first-line treatment for membranous nephropathy. Nephrotic syndrome limits rituximab exposure due to urinary drug loss. Rituximab underdosing (serum level< 2 μg/mL at month-3) is a risk factor for treatment failure. We developed a machine learning algorithm to predict the risk of underdosing based on patients’ characteristics at rituximab infusion. We investigated the relationship between the predicted risk of underdosing and the cumulative dose of rituximab required to achieve remission. MethodsRituximab concentrations were measured at month-3 in 92 sera from adult patients with primary membranous nephropathy, split into a training (75%) and a testing set (25%). A forward-backward machine-learning procedure determined the best combination of variables to predict rituximab underdosing in the training dataset, which was tested in the test set. The performances were evaluated for accuracy, sensitivity and specificity in ten-fold cross-validation training and test sets. ResultsThe best variables combination to predict rituximab underdosing included: age, sex, body surface area, anti-PLA2R1 antibody titer at day-0, serum albumin at day-0 and day-15 and serum creatinine at day-0 and day-15. The accuracy, sensitivity and specificity were respectively 79.4%, 78.7% and 81.0% (training dataset), and 79.2%, 84.6% and 72.7% (testing dataset). In both sets, the algorithm performed significantly better than chance (p<0.05). Patients with an initial high probability of underdosing experienced a longer time to remission with higher rituximab cumulative doses required to achieved remission. ConclusionThis algorithm could allow for early intensification of rituximab regimen in patients at high estimated risk of underdosing to increase the likelihood of remission.

Primary Sjögren Syndrome (pSS) with PLA2R-Associated Membranous Nephropathy (MN)

Primary Sjögren Syndrome (pSS) with PLA2R-Associated Membranous Nephropathy (MN)

The association of serum anti-PLA2R antibody and glomerularPLA2R antigen staining with clinical manifestations and outcomes in membranous nephropathy.

Phospholipase A2receptor (PLA2R)-associated membranous nephropathy (MN) wasmanifested as seropositiveforPLA2R antibodies (SAb) and/or glomerular PLA2R antigens' (GAg) deposits. According to the test of SAb and GAg, PLA2R-associated MN can be divided into SAb + /GAg-, SAb-/GAg + , and SAb + /GAg + groups. The clinical characteristics and outcomes of the three groups need to be further evaluated. 184 PLA2R-associated MN patients were enrolled. SAb was measured by enzyme-linked immunosorbent assay with a cut-off value of 14 RU/mL. GAg was detected by immunofluorescence using a paraffin section of renal biopsy samples. Clinical characteristics and the decline of eGFR were compared among the 3 groups. There were 33 SAb + /GAg-, 46 SAb-/GAg +, and 105 SAb + /GAg + PLA2R-associated MN patients reviewed. Clinical characteristics, such as the level of proteinuria, serum albumin, as well as eGFR, were comparable between the SAb + /GAg- and SAb + /GAg + patients. While SAb-/GAg + patients exhibited mild clinical manifestations as evidenced by higherserum albumin (P < 0.001) and lower proteinuria (p = 0.049) compared with SAb + /GAg + patients. After 21.96 ± 7.39month follow-up, the eGFR decrease was no difference between the SAb + /GAg- and SAb + /GAg + patients. SAb-/GAg + patients had a lower rate of the > 20% eGFR decline as well as a 50% eGFR decline compared with the SAb + /GAg + patients (10.87% vs 30.48%, p = 0.013; 0.00% vs 4.76%, p = 0.324). Our study showed that the clinical manifestations of SAb + /Gag- patients were the same as those of double-positive patients, while SAb-/GAg + patientsexhibited mild clinical manifestations and slower eGFR decline compared to the double-positive patients.

Introduction of a novel chimeric active immunization mouse model of PLA2R1-associated membranous nephropathy

The phospholipase A2 receptor 1 (PLA2R1) is the major target antigen in patients with membranous nephropathy (MN), an antibody-mediated autoimmune glomerular disease. Investigation of MN pathogenesis has been hampered by the lack of reliable animal models. Here, we overcome this issue by generating a transgenic mouse line expressing a chimeric PLA2R1 (chPLA2R1) consisting of three human PLA2R1 domains (cysteine-rich, fibronectin type-II and CTLD1) and seven murine PLA2R1 domains (CTLD2-8) specifically in podocytes. Mice expressing the chPLA2R1 were healthy at birth and showed no major glomerular alterations when compared to mice with a wild-type PLA2R1 status. Upon active immunization with human PLA2R1 (hPLA2R1), chPLA2R1-positive mice developed anti-hPLA2R1 antibodies, a nephrotic syndrome, and all major histological features of MN, including granular deposition of mouse IgG and complement components in immunofluorescence and subepithelial electron-dense deposits and podocyte foot process effacement in electron microscopy. In order to investigate the role of the complement system in this model, we further crossed chPLA2R1-positive mice with mice lacking the central complement component C3 (C3-/- mice). Upon immunization with hPLA2R1, chPLA2R1-positive C3-/- mice had substantially less severe albuminuria and nephrotic syndrome when compared to chPLA2R1-positive mice with a wild-type C3 status. In conclusion, we introduce a novel active immunization model of PLA2R1-associated MN and demonstrate a pathogenic role of the complement system in this model.

Measurement of urinary exosomal phospholipase A2 receptor is a sensitive method for diagnosis of PLA2R-associated membranous nephropathy.

The discovery of phospholipase A2 receptor (PLA2R) and its antibody (aPLA2Rab) has paved the way for diagnosing PLA2R-associated membranous nephropathy (PLA2R-MN) with a high specificity of 98%. However, the sensitivity was only 40% to 83.9%, and there is ongoing discussion around determining the optimal threshold for diagnosis. Recent advancements in the use of exosomes, a novel form of "liquid biopsy," have shown great promise in identifying markers for various medical conditions. Protein mass spectrometry and western blot were applied to verify the existence of PLA2R antigen in the urine exosome. We then evaluated the efficacy of urinary exosomal PLA2R antigen alone or combined with serum aPLA2Rab level to diagnose PLA2R-MN. The urinary exosomes contained a high abundance of PLA2R antigen as evidenced by protein mass spectrometry and western blot in 85 PLA2R-MN patients vs the disease controls (14 secondary MN patients, 22 non-MN patients and 4 PLA2R-negative MN patients) and 20 healthy controls. Of note, urinary exosomal PLA2R antigen abundance also had a good consistency with the PLA2R antigen level in the renal specimens of PLA2R-MN patients. The sensitivity of urinary exosomal PLA2R for diagnosing PLA2R-MN reached 95.4%, whereas the specificity was 63.3%. Combining detection of the urinary exosomal PLA2R and serum aPLA2Rab could develop a more sensitive diagnostic method for PLA2R-MN, especially for patients with serum aPLA2Rab ranging from 2 to 20 RU/mL. Measurement of urinary exosomal PLA2R could be a sensitive method for the diagnosis of PLA2R-MN.

#3585 FAT1 ANTIGEN IN PATIENTS WITH MEMBRANOUS NEPHROPATHY AFTER HEMATOPOIETIC STEM CELL ALLOTRANSPLANTATION: A CASE SERIES

Abstract Background and Aims Nephrotic syndrome (NS) is a rare complication of haematopoietic stem cell transplantation (HSCT). When it occurs, it usually develops after cessation of immunosuppressive therapy, which is why it is commonly denominated as a renal form of chronic graft-versus-host disease. Membranous nephropathy (MN) is the most common pathological finding. The protocadherin FAT1 antigen is a novel antigen identified only in patients with MN who have undergone allogeneic HSCT. PLA2R and NELL1 antigens can also be found, even though they are rare and not specific to HSCT-associated MN. The aim of this study was to present a case series of allogeneic HSCT-associated MN, the treatment, outcomes and presence of a novel antigen specifically detected in this population. Method All patients with full blown NS due to MN after HSCT in UHC Zagreb were enrolled. Kidney biopsy was performed and examined by light, immunofluorescence and electron microscopy. Biopsy samples were sent to Renal Pathology Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic for detection of FAT1 antigen in biopsy tissue samples Results In last 30 years there had been 1302 HSCT in UHC Zagreb and three of them developed MN. The first two patients were treated with allogeneic HSCT for acute myeloid leukaemia (AML). Both developed NS after cessation of GVHD prophylaxis, after 1 and 8 months respectively. The first patient's kidney function was preserved, while the second patient's was reduced. Kidney biopsy showed MN. Thorough examination found no secondary cause of the disease. In the first patient, complete remission (CR) was achieved after 5 months of steroids, 2 boluses of cyclophosphamide (CP) and cyclosporine treatment. The second patient reached partial remission (PR) after 6 months of steroid treatment and oral CP. Immunosuppression was terminated due to infectious complications. CR was achieved after an additional 8 months while the patient was not taking immunosuppressants. Both patients remained in CR during the follow-up period. The third patient with acute lymphoblastic leukaemia (ALL) underwent a related peripheral blood HSCT. Sixteen years later, he developed NS with preserved renal function and was diagnosed with MN. Apart from thyroid disease, no secondary cause was detected and he was treated with rituximab. Partial remission (PR) was achieved after 24 months of therapy. Anti-PLA2R antibodies were negative in all three cases. Tissue samples from patients 1 and 2 were positive for FAT1 antigen using laser microdissection and tandem mass spectrometry (MS/MS) of glomeruli. The third patient was negative for FAT1. Clinical and biopsy findings in our cohort of HSCT-associated MN are summarised in Tables 1 and 2. Conclusion MN can occur at different points in time, sometimes even years, after HSCT. It can be successfully treated with steroids and immunosuppressants, achieving long-term remission. Most patients with HSCT-associated MN are FAT1-positive, although it is not the only antigen associated with MN in HSCT patients. In the future, serum testing for anti-FAT1 antibodies in patients with HSCT could be of similar significance in diagnosing FAT1-associated MN as PLA2R antibodies are for PLA2R-associated MN.

Lectin Complement Pathway Activation is Associated with Massive Proteinuria in PLA2R-Positive Membranous Nephropathy: A Retrospective Study.

Complement activation is highly involved in membranous nephropathy. Identifying the mechanism of the complement activation pathway carries crucial therapeutic implications yet remains controversial. This study explored lectin complement pathway activation in PLA2R-associated membranous nephropathy (MN). One hundred and seventy-six patients with biopsy-proven PLA2R-associated MN were enrolled in the retrospective study and divided into the remission group (24-hour urine protein <0.75g and serum albumin >35 g/L) and the nephrotic syndrome group. The clinical manifestation and C3, C4d, C1q, MBL, and B factor in renal biopsy tissues and C3, C4, and immunoglobulins in serum were evaluated. Deposition of glomerular C3, C4d, and mannose-binding lectin (MBL) was significantly higher in the activated state than in the remission state in PLA2R-associated MN. MBL deposition was the risk factor for no remission. During follow-up, the persistent non-remission patients have significantly lower serum C3 levels. Activation of the lectin complement pathway in PLA2R-associated MN may contribute to proteinuria progression and disease activity.

Clinical characteristics of membranous nephropathy with spontaneous remission: An analysis of 24 patients

PurposeTo investigate the prognosis of patients with spontaneous remission (SR) of phospholipase A2 receptor (PLA2R)-associated membranous nephropathy (MN). Patients and methodsPatients diagnosed with MN were recruited after examining their renal biopsy in the Renal Department of China-Japan Friendship Hospital between January 2015 and September 2021. Among them, 24 patients with SR were included in this study and follow-up. ResultsTwenty-four patients diagnosed with SR of PLA2R-associated MN were recruited; 11 were male, and 13 were female, with a mean age of 49.5±14.5 years (range, 30–77 years). The initial 24-hour urinary total protein and serum albumin levels were 0.29±0.14g/d and 37.5±4.4g/L, respectively, and the initial serum creatinine was 65.0±15.8μmol/L. During the follow-up of 33.9±19.1 months (range, 6–73 months), 22 (91.7%) patients maintained remission; however, one patient had impaired renal function due to acute coronary syndrome and coronary angiography findings, and one patient experienced a repeated relapse caused by respiratory tract infection, at 50 and 70 months. A systematic review of the relevant literature was conducted, and records of patients with SR of PLA2R-associated MN were retrieved from 16 case reports or case series with a total of 97 cases. ConclusionsMost patients with SR of MN had a promising long-term prognosis, with only a few cases of relapse.

Clinical characteristics of membranous nephropathy with spontaneous remission: An analysis of 24 patients

PurposeTo investigate the prognosis of patients with spontaneous remission (SR) of phospholipase A2 receptor (PLA2R)-associated membranous nephropathy (MN). Patients and methodsPatients diagnosed with MN were recruited after examining their renal biopsy in the Renal Department of China-Japan Friendship Hospital between January 2015 and September 2021. Among them, 24 patients with SR were included in this study and follow-up. ResultsTwenty-four patients diagnosed with SR of PLA2R-associated MN were recruited; 11 were male, and 13 were female, with a mean age of 49.5±14.5 years (range, 30–77 years). The initial 24-hour urinary total protein and serum albumin levels were 0.29±0.14g/d and 37.5±4.4g/L, respectively, and the initial serum creatinine was 65.0±15.8μmol/L. During the follow-up of 33.9±19.1 months (range, 6–73 months), 22 (91.7%) patients maintained remission; however, one patient had impaired renal function due to acute coronary syndrome and coronary angiography findings, and one patient experienced a repeated relapse caused by respiratory tract infection, at 50 and 70 months. A systematic review of the relevant literature was conducted, and records of patients with SR of PLA2R-associated MN were retrieved from 16 case reports or case series with a total of 97 cases. ConclusionsMost patients with SR of MN had a promising long-term prognosis, with only a few cases of relapse.

Phospholipase A2 receptor is associated with hypercoagulable status in membranous nephropathy: a narrative review.

Background and ObjectiveMembranous nephropathy (MN) is the pathology type with the highest incidence of thrombotic events in nephrotic syndrome (NS). While patients with MN are prone to developing thromboembolic complications, the specific mechanism remains unclear. Many studies have shown a high titer of PLA2R antibody aggravates proteinuria and hypoalbuminemia and predicts a lower likelihood of clinical remission in patients with PLA2R-associated MN. Proteinuria and hypoalbuminemia also increase the risk of thrombotic events. In our previous review, we found secretory phospholipase A2 (sPLA2) may act as a ligand for PLA2R, and binding of sPLA2 to PLA2R results in damage to podocytes. sPLA2 can promote the release of AA from membrane phospholipids, and AA is closely related to blood lipid levels and coagulation cascades. The objective of this study is to explain the relationship between phospholipase A2 receptor (PLA2R) and blood hypercoagulability in MN patients and the new theory that secretory phospholipase A2 (sPLA2) and arachidonic acid (AA) may play a role in regulating blood lipid levels and the coagulation cascade in patients with PLA2R-positive MN.MethodsLiterature retrieval was conducted through China National Knowledge Infrastructure (CNKI) and PubMed. and Introduction information was then retrieved and the results from the literature searched, classified, and important information summarized. A conclusion was then reached, and a new standpoint put forward.Key Content and FindingsWe discussed the role of PLA2R antibody and sPLA2 in hypercoagulability in patients with MN and analyzed the following four possible mechanisms: sPLA2 can combine with PLA2R and induce podocyte apoptosis; sPLA2 may promote the production of anti-PLA2R antibodies; sPLA2 may promote the release of AA from membrane phospholipids; and AA induces platelet aggregation.ConclusionsPLA2R may exacerbate hypercoagulability in patients with PLA2R-related MN, and sPLA2 plays an important role in the process.

A case of Gitelman syndrome with membranous nephropathy

BackgroundGitelman syndrome (GS) is a rare autosomal recessive inherited salt-losing tubulopathy (SLT). Here, we report, for the first time, a case of GS overlapping nephrotic syndrome (NS) related to PLA2R-associated membranous nephropathy (MN).Case presentationWe described a male patient had a 4-year history of recurrent fatigue. Serum biochemistry revealed hypokalemia with renal potassium wasting, hypomagnesemia, metabolic alkalosis, hyperreninemia, hypocalciuria, as well as nephrotic-range proteinuria, hypoalbuminemia, and elevated serum anti-phospholipase A2 receptor (PLA2R) antibody. Gene sequencing identified compound heterozygous mutations in SLC12A3 [c.536T > A(p.V179D) and c.1456G > A(p.D486N)]. The unusual association of SLTs and nephrotic-range glomerular proteinuria prompted us to perform a renal biopsy. Renal biopsy showed idiopathic MN. Due to the potential to activate the sodium-chloride co-transporter (NCC) and cause hyperkalemia, tacrolimus was selected to treat NS. Following treatment with potassium chloride, magnesium oxide, low-dose glucocorticoid combined with tacrolimus, the fatigue significantly improved, and concurrently hypokalemia, hypomagnesemia were corrected and NS was remitted.ConclusionsRenal biopsy should be warranted for GS patients with moderate to nephrotic-range proteinuria. Tacrolimus was preferred to the management of GS patients with NS.