C3 Deposition Research Articles

Clinical characteristics of bullous pemphigoid patients of different ages and the possible mechanism.

Bullous pemphigoid (BP) is an acquired autoimmune bullous disease that often occurs in elderly patients. Some BP patients with early age of disease onset were observed to have difficulty in receiving applicable disease control. It remains challenging for clinicians to choose the appropriate treatment for these patients. This study aimed to analyze the differences between patients of different ages at disease onset and further explore the possible mechanism of these differences between patients of different ages. A total of 215 BP patients seen at the dermatology department of Peking Union Medical College Hospital between January 2009 and September 2020 were included. The patients were allocated to five groups according to the age at disease onset. Clinical data were collected through medical records and telephone follow-up interviews. Analyses of anti-BP180 antibody subclasses, anti-BP230 antibodies, complement fixation, serum cytokine levels, and single nucleotide polymorphisms (SNPs) were conducted. Nearly 52% of patients under 60 were misdiagnosed on their first visit, often presenting with oral mucosal involvement. The anti-BP180 immunoglobulin (Ig) E titers and C3 deposition increased in patients under 60 (p = 0.044 and p = 0.014, respectively), while the anti-BP230 IgG titers decreased (p = 0.043). The hospitalization rate of patients under 50 was significantly higher than that of patients aged 80 and older (p < 0.001). The patients under 60 had a significantly higher serum concentration of interleukin (IL)-13, tumor necrosis factor (TNF)-α, and interferon gamma (IFN-γ) (p < 0.005, respectively). We observed significant differences in the distribution of genotypes or alleles of TNF-α rs1799964, TNF-α rs1800630, and IFN-γ rs2069705. Approximately one-third of the elderly patients suffered from neurological diseases. Elderly patients usually presented with peripheral eosinophilia (p = 0.013). No significant difference was identified in the recurrence rate and complement-activating capacity among the age groups. In conclusion, the early age of BP onset was associated with a more severe clinical presentation, higher titers of anti-BP180 IgE, lower titers of anti-BP230 IgG, and significantly higher serum concentrations of IL-13, TNF-α, and IFN-γ. It may also be associated with the presence of SNPs of cytokines, including TNF-α rs1799964, TNF-α rs1800630, and IFN-γ rs2069705 variants.

Effectiveness of a Novel PLA2R1 Knock-In Rat Model in Repairing Renal Function Damage.

Phospholipase A2 receptor 1 (PLA2R1) exists in many animals and plays an important role in membranous nephropathy. In this study, we aimed to evaluate a PLA2R1 knock-in rat model with repaired kidney function to study the molecular mechanisms of membranous nephropathy. We constructed the PLA2R1 knockout [PLA2R1(-)] model and PLA2R1 knock in [PLA2R1(+)] model in rats. Consistent complement C3 and IgA expression was confirmed through colocalization studies. Urinary biochemical indicators were performed using Automatic Biochemistry Analyzer. The complement C3, IgG, and Nephrin were detected by immunofluorescence assay. The expression levels of complement C3, IgA, and PLA2R1 were detected by western blot. The differential expression proteins (DEPs) between control and PLA2R1(+) models were detected by liquid chromatography with tandem mass spectrometry. The PLA2R1(-) model showed proteinuria, complement C3 aggregation, and IgA and IgG deposition in the glomerulus. Comparing with the PLA2R1(-) model, the PLA2R1(+) model, the deposition of complement C3 and IgA in the glomerulus did not completely disappear, and IgG expression weakened. Moreover, the absolute value of urinary protein was much lower in the PLA2R1(+) model than in the PLA2R1(-) model, and some of the humanized PLA2R1 gene fragments repaired some of the kidney functions. Humanized PLA2R1-insertion in rats can repair part of the renal function and reduce proteinuria, which will help in studying the molecular mechanisms of membranous nephropathy, as well as the entire membranous nephropathy-related system and complement activation signaling pathway.

Combined injection of pristane and Bacillus Calmette-Guerin Vaccine successfully establishes a lupus model with atherosclerosis.

Cardiovascular disease (CVD) induced by atherosclerosis (AS) is the main fatal complication of systemic lupus erythematosus (SLE). Establishing an appropriate animal model of SLE with AS is of great value for investigating the pathogenesis and therapeutic targets of SLE-CVD. In the present work, pristane was injected intraperitoneally into C57BL/6J mice to establish the SLE model and Bacillus Calmette-Guerin Vaccine (BCG) was injected intradermally one month later to enhance immunity and induce AS. Both pristane or pristane and BCG treated C57BL/6J mice exhibit a classical lupus-like phenotype which manifested as proteinuria and high levels of serum anti-ANA and anti-dsDNA autoantibodies, in conjunction with pathological changes in spleen and kidney, complement C3 deposition in the kidney, overactivation of T and B cells, a decreased proportion of splenic CD19+ B cells, and an increased frequency of CD19-CD138+ plasma cells, CD19+CD27+ memory B cells, CD3+CD4+ helper T (Th) cells, and CD3+CD4+CXCR5+PD-1+ T follicular helper cells. The combined pristane and BCG challenge aggravated AS in SLE mice, which had an enlarged thymus gland, an increased T cell proliferative vitality, an expanded Th cell pool, severe perivascular lymphocytes, and CD68+ macrophage infiltration, in addition to an intimal lipid deposition, and further elevation of Toll-like receptor 2 (TLR2), TLR4, and the transcription factor nuclear factor-κB (NF-κB) expression in kidney tissue and blood vessels when comparing with pristane or BCG injection alone. Pristane combined BCG challenge is able to establish a validated SLE-AS mouse model in C57BL/6J mice.

Novel opportunities for C3 glomerulopathy treatment: what do we know to date

C3 glomerulopathy (С3G) is a group of ultra-rare diseases with the incidence about 13 cases per 1 million population per year. Major role in the C3G pathogenesis play disturbances of the complement activation, deposition and degradation, resulting in the glomerular deposition of C3, which, in turn, leads to glomerular damage and inflammation in the kidney tissue. C3G commonly associated with the progressive course, poor kidney outcomes and high rate of recurrence after kidney transplantation. Efficacy of the current conventional approaches to C3G treatment, including nephroprotective measures and glucocorticoids and mycophenolic acid analogues is insufficient; the usage of targeted anti-B-cell therapy with rituximab also did not provide sustainable effect. Unsatisfactory results of the current clinical practice and a rapid progress in the development of new targeted medications recently lead to the active investigation of a number of molecules, targeting several factors of the complement cascade, which may enrich therapeutic armamentarium for the treatment of C3G and other glomerular diseases, associated with the complement dysregulation. Several studies, aiming the evaluation of blockade of various complement system components – C5, C5a receptor, factor D, factor B, C3, and mannose-binding lectin-associated serine proteases type 1 and type 2 for С3G treatment are currently in progress. This review of literature presents available data from the current clinical trials and discusses new options of the targeted treatment of C3G.

Some Human Anti-Glycan Antibodies Lack the Ability to Activate the Complement System.

Background. Naturally occurring human antibodies against glycans recognize and quickly eliminate infectious bacteria, viruses and aberrantly glycosylated neoplastic malignant cells, and they often initiate processes that involve the complement system. Methods. Using a printed glycan array (PGA) containing 605 glycoligands (oligo- and polysaccharides, glycopeptides), we examined which of the glycan-binding antibodies are able to activate the complement system. Using this PGA, the specificities of antibodies of the IgM and IgG classes were determined in the blood serum of healthy donors (suggested as mostly natural), and, then, using the same array, it was determined which types of the bound immunoglobulins were also showing C3 deposition. Results. It was found that about 30% of anti-glycan antibodies in human serum detected by the PGA did not activate the complement. They were mostly IgGs and directed to bacterial O-antigens; no apparent common structural motif within their target polysaccharides was found. Antibodies to blood group systems ABO and Forssman, xeno-antigens, a number of polysaccharides from various strains of S. enterica, E. coli and P. alcalifaciens, as well as small fragments of bacterial polysaccharides were recognized by complement-activating antibodies as expected. A complement-activating antibody was affinity-isolated on glycan-Sepharose from human serum, and, in the presence of the complement, it lysed red blood cells coated with the same glycan (kodecytes, where glycans expressed on biological membranes), while an isolated complement non-activating antibody did not, which confirms the validity of the solid-phase PGA results. Conclusions. Thus, ~30% of human anti-glycan antibodies lack the ability to activate the complement system. The function of the widely represented immunoglobulins that do not cause C3 deposition remains unclear.

Clinical Characteristics, Comorbidities, and Treatment in Patients with Pemphigus-A Single-Center Retrospective Study.

Pemphigus comprises a diverse group of disorders within the autoimmune bullous dermatoses (AIBDs) spectrum. Among these, pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are the most commonly encountered variants. Despite its rarity, this condition can pose a life-threatening risk. We aimed to assess clinical characteristics, comorbidities, medication, as well as the treatment of various types of pemphigus in pemphigus patients. We gathered data from 69 patients treated in the Department of Dermatology in the years 2016-2023. The investigation included sex, age at diagnosis, type of pemphigus, comorbidities and medications, presence of neoplasms and treatment of pemphigus, as well as enzyme-linked immunosorbent assay (ELISA) and direct immunofluorescence (DIF) results. The data were statistically analyzed with the p-value set at 0.05. The study group comprised 69 patients, including 41 women and 28 men. The mean age at diagnosis was 56.89 years +/- 15.42 years. A total of 79.31% of the patients were diagnosed with PV and the following 26.09% with PF. The most common comorbidities were arterial hypertension, hypercholesterolemia, and diabetes mellitus. The dominant treatment regimen was the systemic use of glucocorticosteroids (GCSs; 90% and 94% of PV and PF patients, respectively). More than half of the patients received at least one GCS-sparing treatment, including dapsone and rituximab. We observed a significantly frequent presence of IgG deposits in DIF in patients with PF (p = 0.0217) and a subsequent correlation between the concurrent presence of IgG deposits in DIF and anti-DSG1 antibodies in ELISA testing (p = 0.0469). The combination of IgG, IgG1, IgG4, and C3 deposits was more often existent in PF patients (p = 0.0054) and the combination of IgG4 and C3 deposits in PV patients (p = 0.0339). We also found a positive correlation between the level of anti-DSG1 antibodies and the age at diagnosis (p = 0.0298). Patients with pemphigus are very often diagnosed with significant comorbidities and take diverse medication, which shows that the treatment of pemphigus should follow a multidisciplinary approach. Accurate analysis of the clinical condition of the patients, as well as the results of the ELISA panel or DIF, is crucial for a successful diagnostic and therapeutic process.

GS-4997 halts the progression of tubulointerstitial injury inlupus nephritis.

Tubulointerstitial injury has been increasingly recognized as an important component in lupus nephritis (LN) pathology over the last decades. However, current clinical treatment options for this process remain limited. In this study, we aimed to investigate the potential benefits of GS-4997, a selective inhibitor of ASK1, in tubulointerstitial injury of LN. Female MRL/lpr mice were used as a classical lupus-prone murine model. Development of nephritis was assessed by monitoring of proteinuria, renal function, and histologic analysis. GS-4997 (50 mg/kg) or vehicle were treated orally. Invitro study, human kidney-2 (HK-2) cells were stimulated with 1 μg/mL lipopolysaccharide (LPS) to mimic the response of renal tubular epithelial cells undergoing inflammatory responses during LN. GS-4997 could inhibit the activation of the ASK1 in renal tubulointerstitium in MRL/lpr mice and LPS-induced HK-2 cells. GS-4997 treatment improved renal function, proteinuria, and attenuated tubular injury, renal interstitial fibrosis, and inflammation both invivo and invitro. Additionally, we found that in MRL/lpr mice, GS-4997 reduced deposition of IgG and C3 in the kidneys, antibody levels in the serum, splenic enlargement, and inflammatory cell infiltration in the spleen. Mechanistically, GS-4997 inhibited the activation of downstream signaling molecules, p38 and JNK, in the ASK1 signaling pathway. Pharmacological inhibition of ASK1 may prevent the progression of tubulointerstitial injury via inhibiting the ASK1/MAPK pathway in LN. Therefore, our findings demonstrate the potential use of GS-4997 for LN treatment.

A rare presentation of pompholyx in a child mimicking bullous pemphigoid

Pompholyx, or dyshidrotic eczema, an eczematous condition predominantly seen in adults, occasionally presents in children, where it can be mistaken for other bullous diseases, such as bullous pemphigoid (BP). This case report describes a rare and atypical presentation of pompholyx in a 7-year-old male who exhibited vesicular and bullous lesions on the palms, soles, and dorsae of the feet, mimicking BP. Histopathological examination showed spongiotic reaction and intraepidermal vesicle formation, and direct immunofluorescence was negative for immunoglobulin (Ig)G, IgA, IgM, and C3 deposits, ruling out BP and confirming a diagnosis of pompholyx. Treatment with systemic and topical corticosteroids and emollients led to rapid improvement, with complete resolution in 1 month. A 3-month follow-up showed no recurrence. This case emphasizes the diagnostic challenge of differentiating pompholyx from BP in pediatric patients due to clinical overlap. Accurate identification is essential, as management strategies differ significantly; misdiagnosis can lead to unnecessary immunosuppressive therapy. This report also highlights the need for increased awareness of atypical presentations of pompholyx in children to optimize patient outcomes and reduce treatment-related complications.

Effectiveness of a Novel PLA2R1 Knock-in Middle Age Rat Model in Repairing Renal Function Damage.

Phospholipase A2 receptor 1 (PLA2R1) exists important role in membranous nephropathy. In this study, we evaluate a PLA2R1 in a middle-aged rat model of renal function repair to further investigate the molecular mechanisms of membranous nephropathy. We analyzed the PLA2R1 knockout (KO) model and PLA2R1 knock in (KI) model in rats, extending the time to 85 weeks of age. Urinary biochemical indicators were detected using a fully automated biochemical analyzer. The complement C3, IgG, and Nephrin were detected using the immunofluorescence method. Western blot was used to detect the expression levels of complement C3, IgA and PLA2R1 in middle-aged models. The KO model continues to display glomerular proteinuria, complement C3 aggregation, and IgA and IgG deposition. Comparing with the KO model, the deposition of complement C3 and IgA in the glomerulus of the KI chimeric model still exists and IgG expression weakened. Inserting humanized PLA2R1 into rats can continuously repair partial renal function and reduce proteinuria, which will help investigate the pathogenesis of membranous nephropathy and complement activation signaling pathways.

De Novo C3 Glomerulonephritis of Allograft Associated with Factor H Autoantibody in a Patient with Systemic Lupus Erythematosus: A Case Report

C3 Glomerulonephritis (C3GN) is a rare disease with a challenging diagnosis and poor prognosis. It is characterized by dysregulation of alternate complement pathway and diagnosed by biopsy findings of isolated or predominant C3 deposits on immunofluorescence (IF) staining. Dysregulation of alternate complement pathway (ACP) caused by genetic mutations or autoantibodies leads to C3 glomerulopathy (C3G) and complement-mediated thrombotic microangiopathies (c-TMA), later also referred to as atypical hemolytic uremic syndrome (aHUS). Autoantibodies like C3 nephritic factor and Factor H autoantibodies (FHAA) are frequently seen as acquired abnormalities in C3GN. SLE is a multi-system complex disorder distinguished by the presence of autoantibodies to multiple nuclear antigens, including DNA and ribonucleoprotein leading to complement activation, characterized by low level of C3 and C4 and may present with c-TMA. There are not many cases of C3GN with SLE that have been described, and current literature lacks strong evidence-based treatment options of post-transplant C3GN. Here, we describe a case of de novo C3GN of allograft in a patient with SLE.

A Comparative Study of Direct Immunofluorescence Patterns in Linear IgA Bullous Dermatosis Versus Dermatitis Herpetiformis.

Dermatitis herpetiformis (DH) is typically characterized by granular IgA deposition in the papillary dermis on direct immunofluorescence (DIF), and linear IgA bullous dermatosis (LABD) is characterized by linear deposition of IgA along the basement membrane. Other DIF findings in both conditions may include IgG, IgM, and C3 deposition in various patterns. In cases where immunofluorescence findings are unclear, such as continuous but somewhat granular IgA deposition along the dermal-epidermal junction, additional DIF patterns may be helpful in the diagnostic process. Forty-five cases of digitized images of LABD and 48 digitized images of DH cases were analyzed. The data regarding the positivity and patterns of immunoglobulins were documented and analyzed. None of the LABD cases had a picket fence pattern, while 47.9% (n = 23) of the DH cases had the pattern. Elevated levels of IgG and IgM were found in LABD compared with DH. In DH, higher IgM and kappa light chain levels were observed in the deposited particles compared with those in LABD. The "picket fence pattern" is highly specific for DH (Specificity 100%) but less sensitive (Sensitivity 47.9%). It may be helpful to differentiate between DH and LABD for a more accurate diagnosis.

METTL3 facilitates kidney injury through promoting IRF4-mediated plasma cell infiltration via an m6A-dependent manner in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown cause. N6-methyladenosine (m6A) is the most common mRNA modification and participates in various immune processes such as interferon production and immune cell regulation. However, the role of m6A in dysregulated immune response of SLE remains unknown. PBMCs from SLE patients were collected to compare the m6A modification profile by methylated RNA immunoprecipitation sequencing (MeRIP-seq). Interferon regulatory factor 4 (IRF4) was identified by combination with MeRIP-seq and RNA-Seq. IRF4 and methyltransferase 3 (METTL3) were detected using qRT-PCR and WB. Clinical significance of IRF4 in SLE patients was explored subsequently. IRF4 expression in B cell subsets of female MRL/lpr mice was detected by flow cytometry. Adeno-associated viruses (AAV) including AAV9-METTL3-OE and/or AAV9-IRF4-sh were treated with female MRL/lpr mice. Autoantibody levels and kidney injury were tested by ELISA, pathological staining, and immunofluorescence. m6A level of IRF4 was detected by MeRIP-qPCR. The downstream effectors of IRF4 contributing to renal pathology were explored by RNA-seq and verified by qRT-PCR. m6A methylation features were obviously aberrant in SLE patients, and IRF4 was the upregulated gene modified by m6A. METTL3 and IRF4 expressions were elevated in SLE patients and kidney of MRL/lpr mice. Clinical analysis indicated that SLE patients with high IRF4 level were more prone to kidney damage. IRF4 expression was especially increased in plasma cells of MRL/lpr mice. METTL3 induced renal IRF4 expression, plasma creatinine, ANA and urine ALB levels, IgG and C3 deposition, and renal damage and plasma cell infiltration were aggravated in MRL/lpr mice. However, IRF4 depletion could partially reduce METTL3-induced kidney damage. Meanwhile, m6A level of IRF4 elevated with METTL3 overexpression. Also, the expression of Cxcl1, Bcl3, and Fos mRNA were significantly reduced after knockdown of IRF4, which were mainly involved in TNF signaling pathway. Our study confirmed that upregulated METTL3 promoting IRF4 expression in an m6A-dependent manner, thus causing plasma cell infiltration-mediated kidney damage of SLE. This provides new evidence for the role of m6A in SLE kidney injury.

The prognostic role of activation of the complement pathways in the progression of advanced IgA nephropathy to end-stage renal disease

IntroductionThe role of complement system in late stage of IgA nephropathy (IgAN) remains unknown. We therefore investigated the effects of complement system on worsening kidney function in advanced (stage 4 CKD) IgAN.MethodsRenal specimens of 69 IgAN patients who underwent renal biopsy during stage 4 CKD between 2010 and 2021, were stained using immunofluorescence (IF) and immunohistochemistry (IHC) for glomerular complement components. The primary outcome was progression to end-stage renal disease (ESRD). Associations of complement components with baseline clinicopathological characteristics and outcomes were assessed using multivariable Cox regression and Spearman analyses.ResultsDuring a median follow-up of 18.0 months, 26 (37.7%) patients progressed to ESRD and none died. C1q and C3 deposition were detected in 12 and 66 patients, respectively. Higher eGFR [hazards ratio (HR), 0.852, 95% confidence interval (CI), 0.756–0.959; P = 0.008], higher C3 intensity (HR, 2.955, 95%CI, 1.063–8.220; P = 0.038) and T1-2 score (HR, 2.576, 95%CI, 1.205–5.576, P = 0.015) were predictive of time to ESRD in CKD 4 stage IgAN. Significant expressions of C1q (P = 0.005), C4d (P < 0.001), factor B (P < 0.001), C3 (P = 0.042) and C5b-9 (P = 0.004) were identified in ESRD group than in non-ESRD group by IHC, while MBL expression was low. Although they were not associated with baseline 24 h-UP, higher factor B and C1q expressions were both correlated with a lower baseline eGFR (P < 0.001 and = 0.04, respectively) and the deterioration of kidney function during follow-up (P = 0.046 and 0.015, respectively).ConclusionComplement deposition in IgAN patients with stage 4 CKD portends a faster deterioration of kidney function. Activation of classical and alternative complement pathways plays a major role in this stage.

Protease-activated receptor 2 (PAR2) inhibition reduces complement-associated cardiac remodelling in obesity-related heart failure

Abstract Background and Aims Obesity is considered a major risk factor for the development of heart failure (HF) due to lipid accumulation, oxidative stress and inflammation which results in cardiac remodeling. Protease activated receptor 2 (PAR2) has been linked to various cardiovascular and inflammatory diseases. The role of PAR2 has not yet been studied in obesity-related HF. Methods In the experimental mouse study, we used 1-year-old ApoE knockout (ApoE-/-) and ApoE PAR2 double knockout (ApoE-/-PAR2-/-) mice with a C57BL/6J background on a high fat (HF) diet (n=5/ group). Cell culture experiments were performed with human primary cardiac fibroblasts and HepG2 hepatocytes. Patients (n=50) included in the clinical study had a BMI &amp;gt; 25kg/m², symptoms of heart failure (HF), coronary angiography (CA) that excluded coronary artery disease (CAD) and endomyocardial biopsy (EMB) that confirmed the absence of active myocarditis or primary cardiac amyloidosis. Patients were divided into PAR2low (n=22) and PAR2high (n=22) based on the median PAR2 expression measured via qPCR in the EMB of the cohort, and six patients served as healthy controls. Results Evaluation of endomyocardial biopsies (EMB) from overweight/ obese non-ischemic cardiomyopathy (NICM) patients with heart failure (HF) (n=44) revealed that a reduced cardiac PAR2 expression is associated with less cardiac C3 (p≤0.054), C4 (p≤0.041) and C5 gene expression (p≤0.045), as well as plasma levels of complement C3 (1.1g/l± 0.7 vs 2.1g/l±0.2; p≤0.016) and C5b-9 (303.4ng/ml± 215.7 vs 992.7ng/ml± 756.2; p≤0.0002) and as a result, better systolic function i.e. LVEF (46.1%±17.1 vs 36.8%±15.2; p≤0.046) and LV GLS (-14.9%± 5.7 vs -9.5%± 4.6; p≤0.009), less cardiac remodeling and damage. Correspondingly, aged ApoE-/-PAR2-/-mice on a Western diet showed less hepatic and cardiac complement expression (i.e. C1q, C3, C4, C5, C9), cardiac C3 deposition (p≤0.047) and C5b-9 plasma levels (p≤0.049), as well as less cardiac necrosis (p≤0.046) and lower BNP (p≤0.016) than ApoE-/-. PAR2 overexpression in human cardiac fibroblasts (HCFs) independently enhanced and PAR2 antagonism reduced interferon γ (IFNγ)-mediated STAT1-dependent complement C3, C4 and C5 expression. Conclusions Protease-activated receptor 2 regulates complement-mediated cardiac damage and remodeling in HF. The PAR2-IFNγ/STAT1/C3-C4-C5 complement-axis might be a promising prognostic and therapeutic approach to identify and treat high-risk cases of HF in overweight/obese patients.

Childhood onset C3 glomerulopathy: recurrence after kidney transplantation-a case series.

C3 Glomerulopathy (C3G) is a complement-mediated disease, with predominant C3 deposits, where pathogenic genetic variants in complement system components and circulating autoantibodies result in loss of control of the alternative pathway, have been described. A high incidence of disease recurrence including graft failure has been reported after kidney transplantation (KTx). Currently treatment modalities for preventing and treating post KTx C3G recurrence (plasma exchange, rituximab and eculizumab) in adults have yielded inconsistent results. Data on post KTx C3G recurrence in childhood-onset C3G is still unknown. A comprehensive case study of patients diagnosed with C3G as children or adolescents, who underwent KTx between the years 2015-2023. Data collected included complement workup, treatment modalities, and outcomes. 19 patients with C3G were identified during the study period. Five patients developed ESRD and received a kidney transplant. C3G recurrence was diagnosed post KTx in 100% of patients. Graft function improved in 3 of these patients (two with anti-factor H antibodies) after eculizumab treatment, one patient reached graft failure 9 months after transplantation despite eculizumab, recieved a second successful transplantation with pre-emptive eculizumab treatment and one patient showed histologic signs of disease recurrence without clinical signs. C3G recurrence after KTx in patients diagnosed as children or adolescents may be higher than previously described. Treatment with eculizumab is beneficial in some patients. New treatments are needed for improving post-transplant outcome in patients with C3G.

A case of de novo glomerulonephritis following COVID-19 in a patient with preexistent IgA vasculitis.

During the unprecedented COVID-19 outbreak, new-onset or relapsing glomerulonephritis, such as ANCA-associated glomerulonephritis and Immunoglobulin A (IgA) nephropathy, following COVID-19 has been reported. However, to date, the association of COVID-19 with preexistent IgA vasculitis (IgAV) remains unclear. Here, we present the case of a 20-something old Japanese woman with preexistent IgAV who newly developed glomerulonephritis following COVID-19. At the diagnosis of IgAV, she had cutaneous purpura, joint pains, and gastrointestinal symptoms, but no signs of kidney involvement. Three months ago, she was tested positive for COVID-19 and subsequently developed hematuria and proteinuria. She was then admitted to our hospital and renal biopsy showed glomerular mesangial expansion and hypercellularity and cellular and fibrocellular crescents, accompanied by diffuse IgA and C3 deposits. With the diagnosis of de novo IgAV nephritis, the patient was treated with intravenous methylprednisolone followed by oral prednisolone. She had favorable responses to this treatment and has achieved and maintained the remission of hematuria and proteinuria after initiation of glucocorticoid therapy. Our case highlights that immune response to SARS-CoV-2 infection could trigger the onset of glomerulonephritis in the IgAV patients who have no renal involvement.

Nanoparticle-Binding Immunoglobulins Predict Variable Complement Responses in Healthy and Diseased Cohorts.

Systemic administration of nanomedicines results in the activation of the complement cascade, promoting phagocytic uptake and triggering proinflammatory responses. Identifying the biomarkers that can predict the "risk" of abnormally high complement responders can improve the safety and efficacy of nanomedicines. Polyethylene glycol (PEG) and dextran are two types of clinically approved polymer coatings that trigger complement activation. We performed a multifaceted analysis of the factors affecting the complement activation by PEGylated liposomal doxorubicin (PLD) and dextran-coated superparamagnetic iron oxide nanoworms (SPIO NWs) in plasma from patients with different inflammatory disease conditions and healthy donors. The complement activation (measured as deposition of the complement protein C3) varied greatly, with 29-fold and 26-fold differences for PLD and SPIO NWs, respectively. Chronic inflammation, acute infection, use of steroids, and sex had minor effects on the variable complement activation, whereas age inversely correlated with the complement activation. C-reactive protein level was not predictive of high (top 20th percentile) complement responses. Plasma concentrations of the main complement factors, as well as total IgG and IgM, showed no correlation with the activation by either nanoparticle. On the other hand, plasma concentrations of anti-PEG IgG and IgM showed a strong positive correlation with the activation by PLD. Particularly, titers of anti-PEG IgM showed the best predictive value for the "risk" of high complement activation by PLD. Titers of antidextran IgG and IgM showed a lower correlation with the activation by SPIO NWs and poor predictive value of the top 20% complement responses. Nanoparticle-bound immunoglobulins showed the best correlation with complement activation and a strong predictive value, supporting the critical role of immunoglobulins in inciting complement. The opsonization of PLD with C3 in plasma with high anti-PEG antibodies was predominantly via the alternative pathway. Characterizing the nature of nanoparticle-binding antibodies has important implications in mitigating and stratifying nanomedicine safety.

Efficacy and Safety of Pegcetacoplan in Kidney Transplant Recipients With Recurrent Complement 3 Glomerulopathy or Primary Immune Complex Membranoproliferative Glomerulonephritis

Complement 3 glomerulopathy (C3G) and primary immune complex membranoproliferative glomerulonephritis (IC-MPGN) have high risks for disease recurrence and allograft loss in transplant kidneys. Pegcetacoplan (targeted complement 3 [C3]/C3b inhibitor) may prevent excessive deposition of C3 and complement 5 [C5] breakdown products and associated renal damage. NOBLE (NCT04572854) is a prospective, phase 2, multicenter, open-label, randomized controlled trial evaluating the efficacy and safety of pegcetacoplan in posttransplant patients with recurrent C3G or IC-MPGN. The primary end point was reduction in C3c staining on renal biopsy at week 12 for patients who received either pegcetacoplan 1080 mg twice weekly by subcutaneous infusion plus standard-of-care (SOC) or SOC only. Ten patients received pegcetacoplan and 3 received SOC only through week 12. At week 12, 5 of 10 pegcetacoplan-treated patients (50%) achieved≥2 orders of magnitude (OOM) reduction in C3 staining (4 of these 5 had 0 staining and absent electron microscopy deposits) and 8 of 10 (80%) achieved≥1 OOM reduction; 1 of 3 (33%) SOC-only patients showed staining reduction. Mean C3G histology activity score decreased by >54% in 8 of 10 pegcetacoplan-treated patients (80.0%). Pegcetacoplan-treated patients with baseline urine protein-to-creatinine ratio (uPCR)≥1000 mg/g showed a median (interquartile range [IQR]) 54.4% (-56.33 to -53.95) reduction in proteinuria at week 12. In addition, pegcetacoplan-treated patients showed stable estimated glomerular filtration rate (eGFR), reduced plasma sC5b-9, and increased serum C3. Pegcetacoplan was well-tolerated and most adverse events were mild/moderate. No discontinuations, treatment withdrawals, or deaths were reported. NOBLE demonstrated efficacy, safety, and tolerability of pegcetacoplan for patients with posttransplant recurrent C3G and primary IC-MPGN.

Serotype 15C Streptococcus pneumoniae resistant to classical complement deposition and agglutination by polyclonal rabbit anti-capsular 15B sera

BackgroundS. pneumoniae (SP) serotypes 15B and 15C are frequent causative agents of invasive pneumococcal disease (IPD), otitis media, and nasopharyngeal colonization in the post PCV13 era. The principal difference between serotypes 15B and 15C is the presence of an O-acetyl group on the pentasaccharide repeating unit of 15B polysaccharide. It remains unclear if antibodies against SP15B polysaccharide demonstrate functional cross reaction with SP15C strains. We compared functional activity of polyclonal rabbit anti-capsular 15B sera against SP15B and SP15C isolates. MethodsUsing flow cytometry we measured complement factors C3c and C4d deposition on SP15B and 15C in the presence of polyclonal rabbit anti capsular 15B sera. We measured the binding of C3c, common to all complement pathways, and C4d, specific to classical pathway, on SP serotypes 15B and 15C when co-incubated with polyclonal rabbit anti capsular 15B sera and antibody depleted complement. Both the proportion of bacteria with complement deposition and the fluorescence intensity were measured. We also measured agglutination as the increase in forward and side scatter. ResultsPolyclonal rabbit anti-capsular 15B sera activated classical pathway resulting in deposition of C4d and C3c at high intensity on all SP15B cells but only achieved limited deposition and intensity of C4 with SP15C. Similarly, polyclonal rabbit anti-capsular 15B sera induced agglutination of SP15B strains in a dose dependent manner and limited agglutination of SP15C. ConclusionsAnti-capsular 15B sera induce limited C4d and C3c deposition, and minimal agglutination with SP15C strains, reflecting lower classical pathway activation in contrast to high C4d and C3c deposition and agglutination of SP15B. These observations support limited functional cross reactivity of anti-15B to SP15C strains and are consistent with the reduction in opsonophagocytic killing of SP15C reported following immunization with vaccines containing 15B polysaccharide.

Iptacopan Reduces Proteinuria and Stabilizes Kidney Function in C3 Glomerulopathy

IntroductionC3 glomerulopathy (C3G) is a complex, chronic, ultra rare, progressive primary glomerulonephritis, resulting from alternative complement pathway overactivation, leading to kidney failure in most patients, and frequent recurrence in transplants. Iptacopan (LNP023) is an oral, proximal complement inhibitor specifically targeting factor B, selectively inhibiting the alternative complement pathway. MethodsThis was a Phase 2 extension study of 26 adult patients with native kidney (Cohort A), or recurrent C3G (post kidney transplantation; Cohort B) receiving open-label iptacopan. ResultsAt 12 months, patients in Cohort A had a significant reduction in 24-h urine protein–creatinine ratio (UPCR; 57%; p<0.0001; confidence interval [CI]: 0.31, 0.59), an improvement in estimated glomerular filtration rate (eGFR; 6.83 mL/min/1.73 m2; p=0.0174; CI: 1.25, 12.40), and an increase in serum C3 levels (geometric mean ratio to baseline: 3.53; p<0.0001; CI: 3.01, 4.15).In Cohort B, most patients had normal urinary protein excretion at baseline [mean (range) 24 h UPCR: 121 (9–445)], which was slightly lower by 12 months (21% reduction; CI: 0.48, 1.31 p=0.3151). In Cohort B at 12 months, mean eGFR was at baseline values (mean change from baseline: -0.96 mL/min/1.73 m2; p=0.7335; CI: -6.60, 4.69). Cohort B patients had significantly higher serum C3 values at 12 months compared with baseline (ratio:1.96; CI: 1.70, 2.27; p<0.0001). In Cohorts A+B combined, the median difference in C3 deposit score on renal biopsy from baseline was -7.00 (CI: -12.00, 4.00;) at 9–12 months treatment with iptacopan. ConclusionThese data provide a clinical rationale for further evaluation of long-term treatment of C3G with iptacopan.