Functional evaluation of rare variants in complement factor I using a minigene assay.

The regulatory serine protease, complement factor I (FI), in conjunction with one of its cofactors (FH, C4BP, MCP, or CR1), plays an essential role in controlling complement activity through inactivation of C3b and C4b. The functional impact by missense variants in the CFI gene, particularly those with minor allele frequencies of 0.01% to 0.1%, is infrequently studied. As such, these variants are typically classified as variants of uncertain significance (VUS) when they are identified by clinical testing. Herein, we utilized a minigene splicing assay to assess the functional impact of 36 ultra-rare variants of CFI. These variants were selected based on their minor allele frequencies (MAF) and their association with low-normal FI levels. Four variants lead to aberrant splicing-one 5' consensus splice site (NM_000204.5: c.1429G>C, p.Asp477His) and three exonic changes (c.355G>A, p.Gly119Arg; c.472G>A, p.Gly158Arg; and c.950G>A, p.Arg317Gln)-enabling their reclassification to likely pathogenic (LP) or pathogenic (P) based on ACMG guidelines. These findings underscore the value of functional assays, such as the minigene assay, in assessing the clinical relevance of rare variants in CFI.

Complement Factor B (CFB) inhibits the malignant progression of lung adenocarcinoma by downregulating the Ras/MAPK signaling pathway.

Lung adenocarcinoma (LUAC) as the most common lung cancer, and its incidence is increasing. Complement factor B (CFB) is an important factor in the alternative complement pathway. CFB has been reported to be involved in the progression of many cancers, including in pancreatic cancer, cutaneous squamous cell carcinoma, and nasopharyngeal carcinoma, but the function and molecular mechanism of CFB in LUAC remains unclear. The present study aimed to explore the role of CFB in LUAC malignant progression. In our previous study, we found that CFB was downregulated expression in LUAC clinical samples. Here, we firstly detected the cell function in vitro. Cell proliferation and migration were increased, while cell apoptosis and cell cycle arrest were suppressed after CFB knockdown. Overexpression of CFB repressed the malignant progression of LUAC in vitro. Besides, in vivo experiments revealed that upregulation of CFB inhibited tumor growth and Ki67 expression. Additionally, our data indicated that CFB negatively regulated Ras/mitogen-activated protein kinase (MAPK) signaling pathway. Furthermore, upregulation of CFB inhibited the progression of LUAC was reversed by Ras/MAPK pathway activators (ML-098 or C16-PAF). Our study uncovered that CFB acts as a tumor suppressor repressed tumorigenesis of LUAC through inhibiting the Ras/MAPK pathway, suggesting that CFB may be a potential biomarker and therapeutic target for LUAC.

Inter-tissue differences in oxidative stress susceptibility reveal a less stable endothelial barrier in the brain than in the retina.

Oxidative stress can impair the endothelial barrier and thereby enable autoantibody migration in Neuromyelitis optica spectrum disorder (NMOSD). Tissue-specific vulnerability to autoantibody-mediated damage could be explained by a differential, tissue-dependent endothelial susceptibility to oxidative stress. In this study, we aim to investigate the barrier integrity and complement profiles of brain and retinal endothelial cells under oxygen-induced oxidative stress to address the question of whether the pathomechanism of NMOSD preferentially affects the brain or the retina. Primary human brain microvascular endothelial cells (HBMEC) and primary human retinal endothelial cells (HREC) were cultivated at different cell densities (2.5*104 to 2*105 cells/cm2) for real-time cell analysis. Both cell types were exposed to 100, 500 and 2500 µM H2O2. Immunostaining (CD31, VE-cadherin, ZO-1) and Western blot, as well as complement protein secretion using multiplex ELISA were performed. HBMEC and HREC cell growth phases were cell type-specific. While HBMEC cell growth could be categorized into an initial peak, proliferation phase, plateau phase, and barrier breakdown phase, HREC showed no proliferation phase, but entered the plateau phase immediately after an initial peak. The plateau phase was 7 h shorter in HREC. Both cell types displayed a short-term, dose-dependent adaptive response to H2O2. Remarkably, at 100 µM H2O2, the transcellular resistance of HBMEC exceeded that of untreated cells. 500 µM H2O2 exerted a more disruptive effect on the HBMEC transcellular resistance than on HREC. Both cell types secreted complement factors H (FH) and I (FI), with FH secretion remaining stable after 2 h, but FI secretion decreasing at higher H2O2 concentrations. The observed differences in resistance to oxidative stress between primary brain and retinal endothelial cells may have implications for further studies of NMOSD and other autoimmune diseases affecting the eye and brain. These findings may open novel perspectives for the understanding and treatment of such diseases.

Complement Component C5a and Fungal Pathogen Induce Diverse Responses through Crosstalk between Transient Receptor Potential Channel (TRPs) Subtypes in Human Conjunctival Epithelial Cells.

The conjunctiva has immune-responsive properties to protect the eye from infections. Its innate immune system reacts against external pathogens, such as fungi. The complement factor C5a is an important contributor to the initial immune response. It is known that activation of transient-receptor-potential-vanilloid 1 (TRPV1) and TRP-melastatin 8 (TRPM8) channels is involved in different immune reactions and inflammation in the human body. The aim of this study was to determine if C5a and mucor racemosus e voluminae cellulae (MR) modulate Ca2+-signaling through changes in TRPs activity in human conjunctival epithelial cells (HCjECs). Furthermore, crosstalk was examined between C5a and MR in mediating calcium regulation. Intracellular Ca2+-concentration ([Ca2+]i) was measured by fluorescence calcium imaging, and whole-cell currents were recorded using the planar-patch-clamp technique. MR was used as a purified extract. Application of C5a (0.05-50 ng/mL) increased both [Ca2+]i and whole-cell currents, which were suppressed by either the TRPV1-blocker AMG 9810 or the TRPM8-blocker AMTB (both 20 µM). The N-terminal peptide C5L2p (20-50 ng/mL) blocked rises in [Ca2+]i induced by C5a. Moreover, the MR-induced rise in Ca2+-influx was suppressed by AMG 9810 and AMTB, as well as 0.05 ng/mL C5a. In conclusion, crosstalk between C5a and MR controls human conjunctival cell function through modulating interactions between TRPV1 and TRPM8 channel activity.

Identification of potential diagnostic biomarkers for hypertension via integrated analysis of gene expression and DNA methylation.

OBJECTIVE: Hypertension refers to the elevated blood pressure (BP) in arteries, with a BP reading of 140/90 mm Hg or higher in adults. Over 40% of >25-year-old population have suffered from hypertension. Thus, this study aimed to find novel diagnostic biomarkers for hypertension. METHODS: All hypertension-related mRNA and methylation datasets were downloaded from the GEO database. Liner model method was used to identify differentially expressed genes (DEGs) between hypertension and control groups. Gene Ontology and Kyoto Encyclopaedia of Genes and Genomes enrichment analysis was employed to obtain functional information. CpG sites and the corresponding genes associated with hypertension were screened using epigenome-wide association study (EWAS) analysis. RESULTS: There were 37 DEGs between the hypertension group and control group, which were significantly enriched in 84 Biological Process terms, 31 Cellular Component terms, 18 Molecular Function terms and 9 signalling pathways. EWAS results indicated that 1072 CpG sites were associated with hypertension occurrence, corresponding to 1029 genes. After cross-analysis, complement factor D (CFD) and OTU deubiquitinase, ubiquitin aldehyde binding 2 (OTUB2) with methylation modification were identified as diagnostic markers for hypertension. CONCLUSION: In conclusion, CFD and OTUB2 were potential biomarkers of hypertension occurrence. Our results will provide more information for hypertension diagnosis and would be more reliable combined with multiple biomarkers.

In the GSE24752 dataset, there were 37 differentially expressed genes between the hypertension group and the normal group.In the GSE42774 dataset, there were 1072 CpG sites, corresponding to 1029 genes, associated with hypertension occurrence.CFD and OTUB2 were potential biomarkers that were associated with hypertension occurrence.

Enhancement of complement-dependent cytotoxicity by linking factor-H derived short consensus repeats 19-20 to CD20 antibodies.

Antibody-mediated complement-dependent cytotoxicity (CDC) on malignant cells is regulated by several complement control proteins, including the inhibitory complement factor H (fH). fH consists of 20 short consensus repeat elements (SCRs) with specific functional domains. Previous research revealed that the fH-derived SCRs 19-20 (SCR1920) can displace full-length fH on the surface of chronic lymphocytic leukemia (CLL) cells, which sensitizes CLL cells for e.g. CD20-targeting therapeutic monoclonal antibody (mAb) induced CDC. Therefore, we constructed lentiviral vectors for the generation of cell lines that stably produce mAb-SCR-fusion variants starting from the clinically approved parental mAbs rituximab, obinutuzumab and ofatumumab, respectively. Flow-cytometry revealed that the modification of the mAbs by the SCRs does not impair the binding to CD20. Increased in vitro lysis potency compared to their parental mAbs was corroborated by showing specific and dose dependent target cell elimination by CDC when compared to their parental mAbs. Lysis of CLL cells was not affected by the depletion of NK cells, suggesting that antibody-dependent cellular cytotoxicity plays a minor role in this context. Overall, this study emphasizes the crucial role of CDC in the elimination of CLL cells by mAbs and introduces a novel approach for enhancing CDC by directly fusing fH SCR1920 with mAbs.

First Successful Treatment of a Patient with a Primary Immune Complex-Membranoproliferative Glomerulonephritis with Iptacopan: A Case Report.

Introduction: Nowadays, there is insufficient evidence for the recommendation of management patients with a primary membranoproliferative glomerulonephritis (MPGN). A better understanding of the pathogenesis has led to the reclassification of primary MPGN and distinction into the two main entities of either primary immune complex-MPGN or C3 glomerulopathy. Both entities share overlapping pathophysiological features with complement alternative pathway (AP) dysregulation. Iptacopan is an oral inhibitor of the complement factor B that effectively blocks the complement AP. Case Presentation: We report the first successful treatment of a 47-year-old man suffering from a primary immune complex-MPGN with iptacopan. So far established immunosuppressive therapies with prednisone and mycophenolate mofetil failed to control the current flare of the disease, mainly presenting with impaired kidney function and proteinuria within the nephrotic range. However, 3 months after starting the treatment with iptacopan urine protein-creatinine ratio decreased impressively to a level of 100-150 mg/mmol. Thereafter, low-level proteinuria and kidney function remained stable during follow-up. Do date, the treatment with iptacopan is continued as a monotherapy and is well tolerated. Conclusion: To the best of our knowledge, this is the first case report which suggests that iptacopan may be an interesting treatment option for primary immune complex-MPGN.

Complement factor I knockdown inhibits colon cancer development by affecting Wnt/ß-catenin/c-Myc signaling pathway and glycolysis.

BACKGROUND: Colon cancer (CC) occurrence and progression are considerably influenced by the tumor microenvironment. However, the exact underlying regulatory mechanisms remain unclear. AIM: To investigate immune infiltration-related differentially expressed genes (DEGs) in CC and specifically explored the role and potential molecular mechanisms of complement factor I (CFI). METHODS: Immune infiltration-associated DEGs were screened for CC using bioinformatics. Quantitative reverse transcription polymerase chain reaction was used to examine hub DEGs expression in the CC cell lines. Stable CFI-knockdown HT29 and HCT116 cell lines were constructed, and the diverse roles of CFI in vitro were assessed using CCK-8, 5-ethynyl-2'-deoxyuridine, wound healing, and transwell assays. Hematoxylin and eosin staining and immunohistochemistry staining were employed to evaluate the influence of CFI on the tumorigenesis of CC xenograft models constructed using BALB/c male nude mice. Key proteins associated with glycolysis and the Wnt pathway were measured using western blotting. RESULTS: Six key immune infiltration-related DEGs were screened, among which the expression of CFI, complement factor B, lymphoid enhancer binding factor 1, and SRY-related high-mobility-group box 4 was upregulated, whereas that of fatty acid-binding protein 1, and bone morphogenic protein-2 was downregulated. Furthermore, CFI could be used as a diagnostic biomarker for CC. Functionally, CFI silencing inhibited CC cell proliferation, migration, invasion, and tumor growth. Mechanistically, CFI knockdown downregulated the expression of key glycolysis-related proteins (glucose transporter type 1, hexokinase 2, lactate dehydrogenase A, and pyruvate kinase M2) and the Wnt pathway-related proteins (ß-catenin and c-Myc). Further investigation indicated that CFI knockdown inhibited glycolysis in CC by blocking the Wnt/ß-catenin/c-Myc pathway. CONCLUSION: The findings of the present study demonstrate that CFI plays a crucial role in CC development by influencing glycolysis and the Wnt/ß-catenin/c-Myc pathway, indicating that it could serve as a promising target for therapeutic intervention in CC.

Infantile Bullous Pemphigoid: A Case Report.

Background: Infantile bullous pemphigoid (IBP) is an exceptionally rare acquired autoimmune subepidermal bullous disorder characterized by vesicles, bullae, and additional manifestations, such as urticarial and infiltrated papules, plaques, or eczematous lesions. These skin lesions can lead to eroded and crusted regions after healing, and in some cases, rapid blister rupturing causes extensively eroded areas. Reporting these rare cases is crucial to improving our understanding, diagnosis, and treatment of IBP. Case Presentation: In this report, we present the clinical case of a 4-month-old male infant with generalized tense bullae causing irritability and sleeplessness. This case highlights the distinctive clinical features of IBP, including the development of multiple generalized tense bullae over 2 weeks. The pathological examination findings confirmed the diagnosis of IBP. Conclusion: This case emphasizes the significance of early identification and proper management of IBP. Our thorough assessment, which incorporates pathological verification and therapeutic interventions, has advanced our understanding of IBP. Additionally, this case underscores the vital need for timely diagnosis and personalized treatment approaches for affected infants.

Urinary complement factor D is increased in primary malignant hypertension: a single-center, cross-sectional study.

Kidney injury is one of the detrimental consequences of primary malignant hypertension (pMHTN). There is a paucity of non-invasive biomarkers to enhance diagnosis and elucidate the underlying mechanisms. This study aims to explore urine protein biomarkers for pMHTN associated renal damage. In the discovery phase, urine samples were collected from 8 pMHTN, 19 disease controls (DCs), and 5 healthy controls (HCs). In-gel digestion combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach was used for identification of proteins associated with pMHTN. In the validation phase, the differentially expressed proteins were validated by ELISA assay in cohort with 10 pMHTN patients, 37 DCs, and 30 HCs. Compared to DCs and HCs, a specific band between 15 and 25 kDa was found in 7 out of 8 patients with pMHTN. Further LC-MS/MS analysis revealed 5 differentially expressed proteins. ELISA validation demonstrated that urinary complement factor D (CFD) was significantly up regulated in pMHTN. By receiver operating characteristic curve analysis, urinary CFD/Cr showed moderate potential in discriminating pMHTN from DCs (the area under curve: 0.822, 95% CI 0.618-0.962). Urinary CFD may be a potential biomarker for pMHTN with its elevation indicative of the activation of the alternative complement pathway in pMHTN.

Anti-C5 monoclonal antibody treatment showing pathological resolution of complement-mediated atypical hemolytic uremic syndrome: a case report.

BACKGROUND: No reports have shown histological changes before and after anti-C5 monoclonal antibody treatment in patients with atypical hemolytic uremic syndrome (aHUS). Here, we report a rare case of complement-mediated aHUS with a complement factor H (CFH) mutation and anti-CFH antibodies who underwent multiple kidney biopsies. CASE PRESENTATION: A 53-year-old woman developed aHUS with CFH gene mutation [c.3572C > T (p. Ser1191 Leu)] and anti-CFH antibodies. Her father had succumbed to acute kidney injury (AKI) in his 30 s. She exhibited AKI, thrombocytopenia, and hemolytic anemia with schistocytes. After improving the platelet count with one session of plasma exchange, a kidney biopsy was performed one month after the onset of symptoms. Blood vessel thrombosis, obvious endothelial swelling, endocapillary hypercellularity, and subendothelial exudative lesions in the glomeruli and arterioles were detected. Anti-C5 monoclonal antibody treatment with eculizumab immediately improved disease activity. A second biopsy 3 months later revealed marked improvement of endothelial injuries with residual membrane double contours and exudative lesions. A third biopsy at 17 months after gradual improvement of kidney function showed a further decrease of double contours along with alterations of the exudative lesions to fibrous intimal thickening. CONCLUSIONS: This is the first report showing the pathophysiology of aHUS in the kidneys and the efficacy of anti-C5 monoclonal antibody treatment by presenting serial kidney pathological features before and after anti-C5 monoclonal antibody treatment. Since her CFH mutation was considered the most important pathological condition, treatment centered on eculizumab was administered, resulting in a good long-term prognosis. In addition, kidney pathological resolution in aHUS occurred over 1 year after anti-C5 monoclonal antibody treatment.

Proof of concept of a new plasma complement Factor H from waste plasma fraction.

Introduction: Complement factor H (FH) is a major regulator of the complement alternative pathway, its mutations predispose to an uncontrolled activation in the kidney and on blood cells and to secondary C3 deficiency. Plasma exchange has been used to correct for FH deficiency and although the therapeutic potential of purified FH has been suggested by in vivo experiments in animal models, a clinical approved FH concentrate is not yet available. We aimed to develop a purification process of FH from a waste fraction rather than whole plasma allowing a more efficient and ethical use of blood and plasma donations. Methods: Waste fractions from industrial plasma fractionation (pooled human plasma) were analyzed for FH content by ELISA. FH was purified from unused fraction III and its decay acceleration, cofactor, and C3 binding capacity were characterized in vitro. Biodistribution was assessed by high-resolution dynamic PET imaging. Finally, the efficacy of the purified FH preparation was tested in the mouse model of C3 glomerulopathy (Cfh-/- mice). Results: Our purification method resulted in a high yield of highly purified (92,07%), pathogen-safe FH. FH concentrate is intact and fully functional as demonstrated by in vitro functional assays. The biodistribution revealed lower renal and liver clearance of human FH in Cfh-/- mice than in wt mice. Treatment of Cfh-/- mice documented its efficacy in limiting C3 activation and promoting the clearance of C3 glomerular deposits. Conclusion: We developed an efficient and economical system for purifying intact and functional FH, starting from waste material of industrial plasma fractionation. The FH concentrate could therefore constitute possible treatments options of patients with C3 glomerulopathy, particularly for those with FH deficiency, but also for patients with other diseases associated with alternative pathway activation.

Comprehensive functional characterization of complement factor I rare variant genotypes identified in the SCOPE geographic atrophy cohort.

Rare variants (RVs) in the gene encoding the regulatory enzyme complement factor I (CFI; FI) that reduce protein function or levels increase age-related macular degeneration risk. A total of 3357 subjects underwent screening in the SCOPE natural history study for geographic atrophy secondary to age-related macular degeneration, including CFI sequencing and serum FI measurement. Eleven CFI RV genotypes that were challenging to categorize as type I (low serum level) or type II (normal serum level, reduced enzymatic function) were characterized in the context of pure FI protein in C3b and C4b fluid phase cleavage assays and a novel bead-based functional assay (BBFA) of C3b cleavage. Four variants predicted or previously characterized as benign were analyzed by BBFA for comparison. In all, three variants (W51S, C67R, and I370T) resulted in low expression. Furthermore, four variants (P64L, R339Q, G527V, and P528T) were identified as being highly deleterious with IC50s for C3b breakdown >1 log increased versus the WT protein, while two variants (K476E and R474Q) were ∼1 log reduced in function. Meanwhile, six variants (P50A, T203I, K441R, E548Q, P553S, and S570T) had IC50s similar to WT. Odds ratios and BBFA IC50s were positively correlated (r = 0.76, p < 0.01), while odds ratios versus combined annotation dependent depletion (CADD) scores were not (r = 0.43, p = 0.16). Overall, 15 CFI RVs were functionally characterized which may aid future patient stratification for complement-targeted therapies. Pure protein in vitro analysis remains the gold standard for determining the functional consequence of CFI RVs.

An unusual case of adult-onset still's disease complicated with anti-complement factor H antibodies associated atypical haemolytic uraemic syndrome.

BACKGROUND: Atypical haemolytic uremic syndrome (aHUS) is an uncommon form of thrombotic microangiopathy (TMA). However, it remains difficult to diagnose the disease early, given its non-specific and overlapping presentation to other conditions such as thrombotic thrombocytopenic purpura and typical HUS. It is also important to identify the underlying causes and to distinguish between primary (due to a genetic abnormality leading to a dysregulated alternative complement pathway) and secondary (often attributed by severe infection or inflammation) forms of the disease, as there is now effective treatment such as monoclonal antibodies against C5 for primary aHUS. However, primary aHUS with severe inflammation are often mistaken as a secondary HUS. We presented an unusual case of adult-onset Still's disease (AOSD) with macrophage activation syndrome (MAS), which is in fact associated with anti-complement factor H (anti-CFH) antibodies related aHUS. Although the aHUS may be triggered by the severe inflammation from the AOSD, the presence of anti-CFH antibodies suggests an underlying genetic defect in the alternative complement pathway, predisposing to primary aHUS. One should note that anti-CFH antibodies associated aHUS may not always associate with genetic predisposition to complement dysregulation and can be an autoimmune form of aHUS, highlighting the importance of genetic testing. CASE PRESENTATION: A 42 years old man was admitted with suspected adult-onset Still's disease. Intravenous methylprednisolone was started but patient was complicated with acute encephalopathy and low platelet. ADAMTS13 test returned to be normal and concurrent aHUS was eventually suspected, 26 days after the initial thrombocytopenia was presented. Plasma exchange was started and patient eventually had 2 doses of eculizumab after funding was approved. Concurrent tocilizumab was also used to treat the adult-onset Still's disease with MAS. The patient was eventually stabilised and long-term tocilizumab maintenance treatment was planned instead of eculizumab following haematology review. Although the aHUS may be a secondary event to MAS according to haematology opinion and the genetic test came back negative for the five major aHUS gene, high titre of anti-CFH antibodies was detected (1242 AU/ml). CONCLUSION: Our case highlighted the importance of prompt anti-CFH antibodies test and genetic testing for aHUS in patients with severe AOSD and features of TMA. Our case also emphasized testing for structural variants within the CFH and CFH-related proteins gene region, as part of the routine genetic analysis in patients with anti-CFH antibodies associated aHUS to improve diagnostic approaches.

Genetic and Clinical Characteristics of Central Serous Chorioretinopathy With Steroid Use.

PURPOSE: To compare the genetic and clinical characteristics of central serous chorioretinopathy (CSC) in patients with and without steroid use. METHODS: A total of 407 consecutive patients with CSC were included. Demographic data and clinical factors, including subfoveal choroidal thickness, bilateral involvement, descending tracts, pachydrusen, fibrin, and dome-shaped pigment epithelial detachment, were obtained. Variants of complement factor H (CFH) I62V (rs800292) and rs1329428 were genotyped in all cases using TaqMan technology. RESULTS: Of the total patients, 48 (11.8%) were steroid users. The majority of males were non-steroid users (82.5%) than steroid users (58.3%) (p = 9.8 × 10-5). Demographic data and the prevalence of clinical factors were comparable between the two groups (all p-values > 0.10). Risk allele frequencies of CFH rs800292 and rs1329428 were also comparable between the two groups (p = 0.76, rs800292: steroid users = 52.1% vs. non-steroid users = 50.4%; p = 0.62, rs1329428: steroid users = 47.9% vs. non-steroid users = 45.3%). CONCLUSIONS: Except for the male/female ratio, there were no significant differences in the clinical presentation or genetic characteristics, including variants of the CFH gene, between the two groups.

A Rare Case of Atypical Hemolytic Uremic Syndrome (aHUS) Precipitated by Dengue and the Treatment Landscape in Singapore.

Atypical hemolytic uremic syndrome (aHUS) is a rare disease caused by uncontrolled complement activation due to complement dysregulation. It is often triggered by precipitating events such as infections, inflammation, pregnancy, or medications. Dengue, an endemic viral infection in Southeast Asia, can activate the complement pathway, thereby triggering aHUS in genetically susceptible individuals. Here, we present the case of a 33-year-old male who presented with Dengue fever and subsequently developed aHUS. Plasma exchange (PLEX) successfully normalized his neurological status and hematological parameters. Although his renal function improved, it failed to normalize. Eculizumab, a monoclonal antibody that inhibits C5, was administered for a total of six months. The treatment was successfully discontinued without evidence of relapse after six months of follow-up. This case report demonstrates the safety of discontinuing eculizumab in patients who do not possess pathogenic mutations or variants in complement factors.

A Case of C3 Nephritis With a Rare Variant of the CFHR5 Gene.

C3 nephropathy is a renal disease caused by the aberrant activation of the alternative complement pathway. The long-term renal prognosis of C3 nephropathy is generally poor, and elucidation of its pathogenesis is clinically important. Genetic abnormalities within complement genes, encompassing autoantibodies targeting complement components and complement factor H-related proteins (CFHRs), can lead to abnormal complement activation. CFHR5 is one of the best-known responsible genes for C3 nephritis. Moreover, the renal prognosis can vary depending on the specific type of genetic mutation. Here, we report the case of a young woman with C3 nephritis and a heterozygous rare variant, P453S, in CFHR5. The P453S variant, characterized by amino acid substitutions with a low allele frequency, was located in the region essential for CFHR5 protein function, and multiple in silico analyses were done suggesting the pathological significance of P453S. The renal function of our patient remains stable. The P453S variant might contribute to the suppression of the CFHR5 protein's function, resulting in gradual complement progression and a favorable renal prognosis.

Heterozygous mutations in factor H aggravate pathological damage in a stable IgA deposition model induced by Lactobacillus casei cell wall extract.

Introduction: Activation of complement through the alternative pathway (AP) has a key role in the pathogenesis of IgA nephropathy (IgAN). We previously showed, by intraperitoneal injection of Lactobacillus casei cell wall extract (LCWE), C57BL/6 mice develop mild kidney damage in association with glomerular IgA deposition. To further address complement activity in causing glomerular histological alterations as suggested in the pathogenesis of IgAN, here we used mice with factor H mutation (FHW/R) to render AP overactivation in conjunction with LCWE injection to stimulate intestinal production of IgA. Methods: Dose response to LCWE were examined between two groups of FHW/R mice. Wild type (FHW/W) mice stimulated with LCWE were used as model control. Results: The FHW/R mice primed with high dose LCWE showed elevated IgA and IgA-IgG complex levels in serum. In addition to 100% positive rate of IgA and C3, they display elevated biomarkers of kidney dysfunction, coincided with severe pathological lesions, resembling those of IgAN. As compared to wild type controls stimulated by the same high dose LCWE, these FHW/R mice exhibited stronger complement activation in the kidney and in circulation. Discussion: The new mouse model shares many disease features with IgAN. The severity of glomerular lesions and the decline of kidney functions are further aggravated through complement overactivation. The model may be a useful tool for preclinical evaluation of treatment response to complement-inhibitors.

C-reactive protein-complement factor H axis as a biomarker of activity in early and intermediate age-related macular degeneration.

Purpose: To determine and compare the serum levels of complement Factor H (FH), monomeric C-Reactive Protein (mCRP) and pentameric C-Reactive protein (pCRP) in patients with age-related macular degeneration (AMD) and to correlate them with clinical, structural and functional parameters. Methods: Cross-sectional observational study. One hundred thirty-nine individuals (88 patients and 51 healthy controls) from two referral centers were included and classified into three groups: early or intermediate AMD (n=33), advanced AMD (n=55), and age and sex matched healthy controls (n=51). Serum levels of FH, mCRP, and pCRP were determined and correlated with clinical and imaging parameters. Results: Patients with intermediate AMD presented FH levels significantly lower than controls [186.5 (72.1-931.8) µg/mL vs 415.2 (106.1-1962.2) µg/mL; p=0.039] and FH levels <200 µg/mL were associated with the presence of drusen and pigmentary changes in the fundoscopy (p=0.002). While no differences were observed in pCRP and mCRP levels, and mCRP was only detected in less than 15% of the included participants, women had a significantly higher detection rate of mCRP than men (21.0% vs. 3.8%, p=0.045). In addition, the ratio mCRP/FH (log) was significantly lower in the control group compared to intermediate AMD (p=0.031). Visual acuity (p<0.001), macular volume (p<0.001), and foveal thickness (p=0.034) were significantly lower in the advanced AMD group, and choroidal thickness was significantly lower in advanced AMD compared to early/intermediate AMD (p=0.023). Conclusion: Intermediate AMD was associated in our cohort with decreased serum FH levels together with increased serum mCRP/FH ratio. All these objective serum biomarkers may suggest an underlying systemic inflammatory process in early/intermediate AMD patients.

Bilateral Retinal Venous Occlusion in Atypical Hemolytic-Uremic Syndrome Due to Complement Factor H Mutation.

PURPOSE: Atypical hemolytic uremic syndrome (aHUS) is a rare progressive thrombotic microangiopathy caused by overactivation in the alternative complement pathway. A wide spectrum of environmental triggers, such as viruses, vaccination, drugs, pregnancy, neoplasms, transplant, and autoimmune diseases can cause aHUS in genetically susceptible individuals. In this report, the diagnosis and treatment process of aHUS and bilateral retinal venous occlusion (RVO) will be presented. METHODS: Single-case, retrospective management of ophthalmological and systemic manifestations. RESULTS: A 28-year-old G2P2 female with acute blurred vision and history of acute renal failure. She was diagnosed with preeclampsia in her gestation history. After the laboratory work-up, the diagnosis of aHUS was confirmed. She was treated with eculizumab following 14 days of plasmapheresis. However, her visual acuity was 20/20 on the right and 20/60 on the left at the time of admission. Retinal examination revealed flame-shaped hemorrhages, exudation, and macular edema. The patient was diagnosed with branch RVO in the right eye. Subsequently, central RVO was occurred in the left eye. Intravitreal dexamethasone implant was administered for both eyes since there was no reasonable regression in retinal findings with bevacizumab treatment. She went into remission and her BCVA reached 20/25 during the 12-month follow-up period under the eculizumab therapy. CONCLUSION: Diagnosis of aHUS is challenging especially during pregnancy and the postpartum period. Although ocular involvement is quite rare, we described bilateral RVO in aHUS case with homozygous nonsense mutation (c.2134 G > T p.G712). Dexamethasone implant should be considered for the treatment of RVO in aHUS cases.