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Cetuximab, an anti-epidermal growth factor receptor (EGFR) antibody, has been shown to improve survival in nasopharyngeal carcinoma (NPC) patients. However, a correlation between the expression of EGFR and the response to cetuximab has not been observed, indicating that the mechanism underlying the effects of cetuximab needs to be further elucidated. The antitumour response involves immunotherapeutic mechanisms that target tumour-associated antigens, including complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC), act either alone or, more often, in combination. However, EBV infected NPC cells often develop resistance mechanisms that allow them to evade immune surveillance. Here, we found that overexpression of the complement-regulated protein CD55 in EBV-associated NPC cells mainly suppresses ADCC activity thus reduces the efficacy of cetuximab. Mechanistically, EBV latent membrane protein 1 (LMP1) mediated upregulation of CD55 through the NF-κB signalling pathway. The present study provides a rationale for the development of CD55 inhibitors to improve the clinical efficacy of cetuximab in NPC. [ABSTRACT FROM AUTHOR]

Abstract The primary pathological change in Parkinson’s disease (PD) is the progressive degeneration of dopaminergic neurons in the substantia nigra. Additionally, excessive microglial activation and synaptic loss are also typical features observed in PD samples. Exercise trainings have been proven to improve PD symptoms, delay the disease progression as well as affect excessive microglial synaptic phagocytosis. In this study, we established a mouse model of PD by injecting mouse-derived α-synuclein preformed fibrils (M-α-syn PFFs) into the substantia nigra, and demonstrated that treadmill exercise inhibits microglial activation and synaptic phagocytosis in striatum. Using RNA-Seq and proteomics, we also found that PD involves excessive activation of the complement pathway which is closely related to over-activation of microglia and abnormal synaptic function. More importantly, exercise training can inhibit complement levels and complement-mediated microglial phagocytosis of synapses. It is probably triggered by CD55, as we observed that CD55 in the striatum significantly increased after exercise training and up-regulation of that molecule rescued motor deficits of PD mice, accompanied with reduced microglial synaptic phagocytosis in the striatum. This research elucidated the interplay among microglia, complement, and synapses, and analyzed the effects of exercise training on these factors. Our work also suggested CD55 as a complement-relevant candidate molecule for developing therapeutic strategies of PD. Graphical Abstract

Background: Thrombocytopenia is a significant concern in individuals with chronic hepatitis infections, especially those who have advanced liver injury. Complement regulatory proteins, namely, CD55 and CD59, may directly disrupt the proper functioning of the complement system. Both proteins are found on platelets and, as a result, might be subjected to autoantibody targeting. This work aimed to assess the expression of complement regulatory proteins (CD59 and CD55) on the platelet surface in patients with hepatitis-associated thrombocytopenia. Methods: This case-control study was performed on 90 patients aged 4 to 80. The patients were divided into three equal groups. Group I: included 30 chronic hepatitis patients with hepatitis B virus and thrombocytopenia. Group II: included 30 chronic hepatitis C virus patients with thrombocytopenia. Group III: 30 immune thrombocytopenia patients were used as controls. Results: Compared with those in group III CD55, CD59, CD61, and CD42 did not substantially differ among group I and group II patients, however, they significantly decreased when group I was compared with group III control subjects, and they significantly differed when group II was compared group III control subjects. A statistically significant positive correlation existed between absolute counts of CD55+ platelets and CD59+ platelets as well as between the absolute counts of CD61+ platelets and CD42+ platelets. Conclusion: CD55 and CD59 could be predictors of late-stage hepatitis accompanied by thrombocytopenia, and this information is important for determining the diagnosis and treatment choice. [ABSTRACT FROM AUTHOR]

The primary pathological change in Parkinson's disease (PD) is the progressive degeneration of dopaminergic neurons in the substantia nigra. Additionally, excessive microglial activation and synaptic loss are also typical features observed in PD samples. Exercise trainings have been proven to improve PD symptoms, delay the disease progression as well as affect excessive microglial synaptic phagocytosis. In this study, we established a mouse model of PD by injecting mouse-derived α-synuclein preformed fibrils (M-α-syn PFFs) into the substantia nigra, and demonstrated that treadmill exercise inhibits microglial activation and synaptic phagocytosis in striatum. Using RNA-Seq and proteomics, we also found that PD involves excessive activation of the complement pathway which is closely related to over-activation of microglia and abnormal synaptic function. More importantly, exercise training can inhibit complement levels and complement-mediated microglial phagocytosis of synapses. It is probably triggered by CD55, as we observed that CD55 in the striatum significantly increased after exercise training and up-regulation of that molecule rescued motor deficits of PD mice, accompanied with reduced microglial synaptic phagocytosis in the striatum. This research elucidated the interplay among microglia, complement, and synapses, and analyzed the effects of exercise training on these factors. Our work also suggested CD55 as a complement-relevant candidate molecule for developing therapeutic strategies of PD. [ABSTRACT FROM AUTHOR]

Background: A complement imbalance in lung alveolar tissue can play a deteriorating role in COVID-19, leading to acute respiratory distress syndrome (ARDS). CD55 is a transmembrane glycoprotein that inhibits the activation of the complement system at the intermediate cascade level, blocking the activity of the C3 convertase. Objective: In our study, lung specimens from COVID-19 and ARDS-positive COVID+/ARDS+ patients were compared with COVID-19 and ARDS-negative COVID–/ARDS– as well as COVID–/ARDS+ patients. Methods: Histochemical staining and immunolabeling of CD55 protein were performed. Results: The COVID–/ARDS– specimen showed higher expression and homogeneous distribution of glycosaminoglycans as well as compactly arranged elastic and collagen fibers of the alveolar walls in comparison to ARDS-affected lungs. In addition, COVID–/ARDS– lung tissues revealed stronger and homogenously distributed CD55 expression on the alveolar walls in comparison to the disrupted COVID–/ARDS+ lung tissues. Conclusions: Even though the collapse of the alveolar linings and the accumulation of cellular components in the alveolar spaces were characteristic of COVID+/ARDS+ lung tissues, evaluating CD55 expression could be relevant to understand its relation to the disease. Furthermore, targeting CD55 upregulation as a potential therapy could be an option for post-infectious complications of COVID-19 and other inflammatory lung diseases in the future. [ABSTRACT FROM AUTHOR]

Abstract Background Localized scleroderma (LoS) is an autoimmune disorder that primarily affects the skin, and is often treated with autologous fat grafting (AFG). Nevertheless, the retention rate of AFG in patients with LoS is typically low. We hypothesize that the low retention rate may be partially attributed to the inherent abnormalities of adipose-derived stem cells (ASCs) from nonlesional sites of patients with LoS. Methods We performed a comparative analysis of the single-cell transcriptome of the SVF from nonlesional sites of patients with LoS and healthy donors, including cellular compositional analysis, differential expression analysis, and high-dimensional weighted gene coexpression network analysis. Experimental validation with fluorescence-activated cell sorting and bleomycin-induced skin fibrosis mice models were conducted. Results We found a significant reduction in the relative proportion of CD55high interstitial progenitors in ASCs under the condition of LoS. Differential expression analysis revealed inherent abnormalities of ASCs from patients with LoS, including enhanced fibrogenesis, reduced anti-inflammatory properties, and increased oxidative stress. Compared with CD55low ASCs, CD55high ASCs expressed significantly higher levels of secreted protein genes that had functions related to anti-inflammation and tissue regeneration (such as CD55, MFAP5, and METRNL). Meanwhile, CD55high ASCs expressed significantly lower levels of secreted protein genes that promote inflammation, such as chemokine and complement protein genes. Furthermore, we provided in vivo experimental evidence that CD55high ASCs had superior treatment efficacy compared with CD55low ASCs in bleomycin-induced skin fibrosis mice models. Conclusions We found that the low retention rate of AFG may be partially ascribed to the reduced pool of interstitial progenitor cells (CD55high) present within the ASC population in patients with LoS. We demonstrated the potential for improving the efficacy of AFG in the treatment of LoS by restoring the pool of interstitial progenitors within ASCs. Our study has significant implications for the field of translational regenerative medicine.

Background: Localized scleroderma (LoS) is an autoimmune disorder that primarily affects the skin, and is often treated with autologous fat grafting (AFG). Nevertheless, the retention rate of AFG in patients with LoS is typically low. We hypothesize that the low retention rate may be partially attributed to the inherent abnormalities of adipose-derived stem cells (ASCs) from nonlesional sites of patients with LoS. Methods: We performed a comparative analysis of the single-cell transcriptome of the SVF from nonlesional sites of patients with LoS and healthy donors, including cellular compositional analysis, differential expression analysis, and high-dimensional weighted gene coexpression network analysis. Experimental validation with fluorescence-activated cell sorting and bleomycin-induced skin fibrosis mice models were conducted. Results: We found a significant reduction in the relative proportion of CD55high interstitial progenitors in ASCs under the condition of LoS. Differential expression analysis revealed inherent abnormalities of ASCs from patients with LoS, including enhanced fibrogenesis, reduced anti-inflammatory properties, and increased oxidative stress. Compared with CD55low ASCs, CD55high ASCs expressed significantly higher levels of secreted protein genes that had functions related to anti-inflammation and tissue regeneration (such as CD55, MFAP5, and METRNL). Meanwhile, CD55high ASCs expressed significantly lower levels of secreted protein genes that promote inflammation, such as chemokine and complement protein genes. Furthermore, we provided in vivo experimental evidence that CD55high ASCs had superior treatment efficacy compared with CD55low ASCs in bleomycin-induced skin fibrosis mice models. Conclusions: We found that the low retention rate of AFG may be partially ascribed to the reduced pool of interstitial progenitor cells (CD55high) present within the ASC population in patients with LoS. We demonstrated the potential for improving the efficacy of AFG in the treatment of LoS by restoring the pool of interstitial progenitors within ASCs. Our study has significant implications for the field of translational regenerative medicine. [ABSTRACT FROM AUTHOR]

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Myopia is regarded as a worldwide epidemic ocular disease, has been proved related to inflammation. CD55, also known as decay-accelerating factor (DAF) can modulate the activation of complement through inhibiting the formation of complement 3 convertase and its dysregulation is involved in various inflammatory diseases. To investigate the association between CD55 and myopia, and to test whether CD55 can inhibit myopia development by suppressing inflammation in the eye, we use three different animal models including monocular form-deprivation myopia, myopia induced by TNF-α administration and allergic conjunctivitis animal model to reveal the CD55 in myopia development. The tears of thirty-eight participants with different spherical equivalents were collected and CD55 in the tears were also analyzed. Complement 3 and complement 5 levels increased while CD55 levels decreased in allergic conjunctivitis and myopic eyes. After anti-inflammatory drugs administration, CD55 expression was increased in monocular form-deprivation myopia model. We also found inflammatory cytokines TGF-β, IL-6, TNF-α, and IL-1β may enhance complement 3 and complement 5 activation while CD55 level was suppressed contrary. Moreover, lower CD55 levels were found in the tears of patients with myopia with decreased diopter values. Finally, CD55-Fc administration on the eyelids can inhibit the elongation of axial length and change of refractive error. CD55-Fc application also suppress myopia development subsequent to complement 3 and complement 5 reduction and can lower myopia-specific (MMP-2 and TGF-β) cytokine expression in TNF-α induced myopia animal model. This suggests that CD55 can inhibit myopia development by suppression of complement activation and eventual down-regulation of inflammation. • CD55-Fc administration kept down the elongation of axial length and the change if refractive error in myopic eyes. • CD55 expression decreased in tears pf patients with higher spherical equivalent. • Activation of complementary system and inflammatory cytokines were involved in myopia development. • CD55 can inhibit myopia development via suppressing the complementary system and downregulating the inflammation. [ABSTRACT FROM AUTHOR]

Background and Aims: To further substantiate the role of antibody‐mediated complement activation in multifocal motor neuropathy (MMN) immunopathology, we investigated the distribution of promotor polymorphisms of genes encoding the membrane‐bound complement regulators CD46, CD55, and CD59 in patients with MMN and controls, and evaluated their association with disease course. Methods: We used Sanger sequencing to genotype five common polymorphisms in the promotor regions of CD46, CD55, and CD59 in 133 patients with MMN and 380 controls. We correlated each polymorphism to clinical parameters. Results: The genotype frequencies of rs28371582, a 21‐bp deletion in the CD55 promotor region, were altered in patients with MMN as compared to controls (p.009; Del/Del genotype 16.8% vs. 7.7%, p.005, odds ratio: 2.43 [1.27–4.58]), and patients carrying this deletion had a more favorable disease course (mean difference 0.26 Medical Research Council [MRC] points/year; 95% confidence interval [CI]: 0.040–0.490, p.019). The presence of CD59 rs141385724 was associated with less severe pre‐diagnostic disease course (mean difference 0.940 MRC point/year; 95% CI: 0.083–1.80, p.032). Interpretation: MMN susceptibility is associated with a 21‐bp deletion in the CD55 promotor region (rs2871582), which is associated with lower CD55 expression. Patients carrying this deletion may have a more favorable long‐term disease outcome. Taken together, these results point out the relevance of the pre‐C5 level of the complement cascade in the inflammatory processes underlying MMN. [ABSTRACT FROM AUTHOR]

Introduction: Flow cytometry‐based paroxysmal nocturnal hemoglobinuria (PNH) testing involves utilization of monoclonal antibodies against GPI‐linked proteins and FLAER. The ability of FLAER to bind to a wide variety of GPI‐linked structures and to be utilized across different leukocyte subsets is remarkable. We hypothesize that FLAER as a standalone reagent may be equally effective for detecting PNH clones. The present study intends to compare the results of a FLAER alone‐based strategy to the recommended FLAER+GPI‐linked protein‐based approach for applicability in clinical settings. Methods: EDTA‐anticoagulated blood samples from patients for PNH workup were tested for PNH by multiparametric flow cytometry. A conventional panel comprising gating markers (CD45 for WBC, CD15 for granulocytes, and CD64 for monocytes) and a combination of FLAER and GPI‐linked markers, such as CD24 and CD14, henceforth referred to as the "routine panel," was employed. Second, a "FLAER‐only panel" comprising the gating markers and FLAER alone (excluding the GPI‐linked markers CD24 and CD14) was set up. The samples were processed using the lyse‐wash‐stain‐wash technique, and events were acquired on BC Navios Ex flow cytometer (Beckman Coulter, Inc., USA) and analyzed on Kaluza Software 2.1. The presence of a PNH clone was reported at a value of ≥0.01%. Results: A total of 209 patients were tested. Both panels found a PNH clone in 20.1% of patients (n = 42/209) with a 100% concordance rate. The PNH clone range for granulocytes was 0.01%–89.68%, and for monocyte was 0.04%–96.09% in the routine panel. The range in the FLAER‐only panel for granulocytes was 0.01%–89.61%, and for monocytes, it was 0.01%–96.05%. Pearson correlation statistics revealed a significant correlation between the size of the PNH clone of granulocytes and monocytes among the two panels tested (granulocytes r = 0.9999, p < 0.0001, 95% CI = 0.9999 to 1.000; monocytes r = 0.9974, p < 0.0001, 95% CI = 0.9966–0.9980). Conclusion: Based on our results, FLAER as a standalone marker is specific and sensitive for identifying PNH clones in granulocytes and monocytes, even for high‐sensitivity PNH assay. The proposed "FLAER‐only panel" panel is efficient and cost‐effective for highly sensitive PNH testing in two different cell lineages, especially in resource‐limited clinical settings. [ABSTRACT FROM AUTHOR]

Background & Aims: A high human cytomegalovirus (HCMV) infection rate accompanied by an increased level of bile duct damage is observed in the perinatal period. The possible mechanism was investigated. Methods: A total of 1,120 HCMV-positive and 9,297 HCMV-negative children were recruited, and depending on age, their liver biochemistry profile was compared. Fetal and infant biliary epithelial cells (F-BECs and I-BECs, respectively) were infected with HCMV, and the differences in cells were revealed by proteomic analysis. Protein–protein interactions were examined by coimmunoprecipitation and mass spectrometry analyses. A murine cytomegalovirus (MCMV) infection model was established to assess treatment effects. Results: Perinatal HCMV infection significantly increased the level of bile duct damage. Neonatal BALB/c mice inoculated with MCMV showed obvious inflammation in the portal area with an abnormal bile duct structure. Proteomics analysis showed higher CD14 expression in F-BECs than in I-BECs. CD14 siRNA administration hindered HCMV infection, and CD14-knockout mice showed lower MCMV-induced bile duct damage. HCMV infection upregulated CD55 and poly ADP-ribose polymerase-1 (PARP-1) expression in F-BECs. Coimmunoprecipitation and mass spectrometry analyses revealed formation of the CD14–CD55 complex. siRNA-mediated inhibition of CD55 expression reduced sCD14-promoted HCMV replication in F-BECs. In MCMV-infected mice, anti-mouse CD14 antibody and PARP-1 inhibitor treatment diminished cell death, ameliorated bile duct damage, and reduced mortality. Conclusions: CD14 facilitates perinatal HCMV infection in BECs via CD55, and PARP-1-mediated cell death was detected in perinatal cytomegalovirus-infected BECs. These results provide new insight into the treatment of perinatal HCMV infection with bile duct damage. Impact and implications: Perinatal human cytomegalovirus (HCMV) infection is associated with bile duct damage, but the underlying mechanism is still unknown. We discovered that CD14 expression is increased in biliary epithelial cells during perinatal HCMV infection and facilitates viral entry through CD55. We also detected PARP-1-mediated cell death in perinatal HCMV-infected biliary epithelial cells. We showed that blocking CD14 or inhibiting PARP-1 reduced bile duct damage and mortality in a mouse model of murine cytomegalovirus infection. Our findings provide a new insight into therapeutic strategies for perinatal HCMV infection.

The transcription factor Kruppel-like factor 4 (KLF4) regulates the expression of immunosuppressive and anti-thrombotic proteins. Despite its importance in maintaining homeostasis, the signals that control its expression and the mechanism of its transactivation remain unclarified. CD55 [aka decay accelerating factor (DAF)], now known to be a regulator of T and B cell responses, biases between pro- and anti-inflammatory processes by controlling autocrine C3a and C5a receptor (C3ar1/C5ar1) signaling in cells. The similarity in CD55's and KLF4's regulatory effects prompted analyses of their functional relationship. In vascular endothelial cells (ECs), CD55 upregulation accompanied KLF4 expression via a p-CREB and CREB Binding Protein (CBP) mechanism. In both ECs and macrophages, CD55 expression was essential for KLF4's downregulation of pro-inflammatory/pro-coagulant proteins and upregulation of homeostatic proteins. Mechanistic studies showed that upregulation of KLF4 upregulated CD55. The upregulated CD55 in turn enabled the recruitment of p-CREB and CBP to KLF4 needed for its transcription. Activation of adenylyl cyclase resulting from repression of autocrine C3ar1/C5ar1 signaling by upregulated CD55 concurrently led to p-CREB and CBP recruitment to KLF4-regulated genes, thereby conferring KLF4's transactivation. Accordingly, silencing CD55 in statin-treated HUVEC disabled CBP transfer from the E-selectin to the eNOS promoter. Importantly, silencing CD55 downregulated KLF4's expression. It did the same in untreated HUVEC transitioning from KLF4low growth to KLF4hi contact inhibition. KLF4's and CD55's function in ECs and macrophages thus are linked via a novel mechanism of gene transactivation. Because the two proteins are co-expressed in many cell types, CD55's activity may be broadly tied to KLF4's immunosuppressive and antithrombotic activities. [ABSTRACT FROM AUTHOR]

Overexpression of the inducible heme oxygenase (HO-1) isoform in visceral renal glomerular epithelial cells (podocytes) using in vivo transgenesis methods was shown to increase glomerular expression of the complement regulatory protein decay-accelerating factor (DAF, CD55) and reduce complement activation/deposition in a rat model of immune-mediated injury. In this preliminary study, we assessed whether constitutively expressed HO-1 regulates CD55 expression in cultured rat podocytes. We employed methods of flow cytometry, quantitative (q) RT-qPCR and post-transcriptional HO-1 gene silencing (HO-1 interfering RNA, RNAi), to assess changes in constitutive (basal) levels of podocyte HO-1 and CD55 mRNA in cultured rat podocytes. Additionally, the effect of the HO-1 inducer, heme, on HO-1 and CD55 expression was assessed. Results indicate that rat podocytes constitutively express HO-1 and DAF and that the HO-1 inducer, heme, increases both HO-1 and DAF expression. HO-1 gene silencing using RNA interference (RNAi) is feasible but the effect on constitutive CD55 transcription is inconsistent. These observations are relevant to conditions of podocyte exposure to heme that can activate the complementary cascade, as may occur in systemic or intraglomerular hemolysis. [ABSTRACT FROM AUTHOR]

Abstract Background Acute graft-versus-host disease (aGvHD) is a life-threatening complication of allogeneic hematopoietic stem cell transplantation (HSCT). Transplantation of immunosuppressive human mesenchymal stromal cells (hMSCs) can protect against aGvHD post-HSCT; however, their efficacy is limited by poor engraftment and survival. Moreover, infused MSCs can be damaged by activated complement, yet strategies to minimise complement injury of hMSCs and improve their survival are limited. Methods Human MSCs were derived from bone marrow (BM), adipose tissue (AT) and umbilical cord (UC). In vitro immunomodulatory potential was determined by co-culture experiments between hMSCs and immune cells implicated in aGvHD disease progression. BM-, AT- and UC-hMSCs were tested for their abilities to protect aGvHD in a mouse model of this disease. Survival and clinical symptoms were monitored, and target tissues of aGvHD were examined by histopathology and qPCR. Transplanted cell survival was evaluated by cell tracing and by qPCR. The transcriptome of BM-, AT- and UC-hMSCs was profiled by RNA-sequencing. Focused experiments were performed to compare the expression of complement inhibitors and the abilities of hMSCs to resist complement lysis. Results Human MSCs derived from three tissues divergently protected against aGvHD in vivo. AT-hMSCs preferentially suppressed complement in vitro and in vivo, resisted complement lysis and survived better after transplantation when compared to BM- and UC-hMSCs. AT-hMSCs also prolonged survival and improved the symptoms and pathological features of aGvHD. We found that complement-decay accelerating factor (CD55), an inhibitor of complement, is elevated in AT-hMSCs and contributed to reduced complement activation. We further report that atorvastatin and erlotinib could upregulate CD55 and suppress complement in all three types of hMSCs. Conclusion CD55, by suppressing complement, contributes to the improved protection of AT-hMSCs against aGvHD. The use of AT-hMSCs or the upregulation of CD55 by small molecules thus represents promising new strategies to promote hMSC survival to improve the efficacy of transplantation therapy. As complement injury is a barrier to all types of hMSC therapy, our findings are of broad significance to enhance the use of hMSCs for the treatment of a wide range of disorders.

The decline in blood donation rates and the ongoing shortage of blood products pose significant challenges to medical societies. One potential solution is to use porcine red blood cells (pRBCs) from genetically modified pigs as an alternative to human red blood cells (hRBCs). However, adverse immunological reactions remain a significant obstacle to their use. This study aimed to evaluate the compatibility of diverse genetically modified pRBCs with human serum. We acquired human complement-competent serum, complement 7 (C7)-deficient serum, and hRBCs from all ABO blood types. Additionally, we used leftover clinical samples from health checkups for further evaluation. pRBCs were collected from wild-type (WT) and genetically modified pigs: triple knockout (TKO), quadruple KO (QKO), and TKO/hCD55.hCD39 knockin (hCD55.hCD39KI). The extent of C3 deposition on RBCs was measured using flow cytometry after incubation in C7-deficient serum diluted in Ca++-enriched or Ca++-depleted and Mg++-enriched buffers. The binding of immunoglobulin (Ig) M/IgG antibody to RBCs after incubation in ABO-type human serum was evaluated using flow cytometry. Naïve human serum- or sensitized monkey serum-mediated hemolysis was also evaluated. Phagocytosis was assessed by incubating labeled RBCs with the human monocytic cell line THP-1 and measurement by flow cytometry. All three genetic modifications significantly improved the compatibility of pRBCs with human serum relative to that of WT pRBCs. The extent of IgM/IgG binding to genetically modified pRBCs was lower than that of WT pRBCs and similar to that of O-type hRBCs. Total and alternative pathway complement activation in all three genetically modified pRBCs was significantly weaker than that in WT pRBCs and did not differ from that in O-type hRBCs. The extent of serum-mediated hemolysis and phagocytosis of these genetically modified pRBCs was low and similar to that of O-type hRBCs. Sensitized monkey serum-mediated hemolysis in QKO and TKO/hCD55.hCD39KI pRBCs was higher than in O-type hRBCs but lower than in TKO pRBCs. The elimination of porcine carbohydrate antigens in genetically modified pigs significantly enhanced pRBC compatibility with naïve human sera, which was comparable to that of O-type hRBCs. These findings provide valuable insights into the development of pRBCs as potential alternatives to hRBCs [ABSTRACT FROM AUTHOR]

The complement system is a complex, tightly regulated protein cascade involved in pathogen defense and the pathogenesis of several diseases. Thus, the development of complement modulators has risen as a potential treatment for complement‐driven inflammatory pathologies. The enzymatically inactive MAP‐2 has been reported to inhibit the lectin pathway by competing with its homologous serine protease MASP‐2. The membrane‐bound complement inhibitor CD55 acts on the C3/C5 convertase level. Here, we fused MAP‐2 to the four N‐terminal domains of CD55 generating a targeted chimeric inhibitor to modulate complement activation at two different levels of the complement cascade. Its biological properties were compared in vitro with the parent molecules. While MAP‐2 and CD55 alone showed a minor inhibition of the three complement pathways when co‐incubated with serum (IC50MAP‐2+CD551‐4 = 60.98, 36.10, and 97.01 nM on the classical, lectin, and alternative pathways, respectively), MAP‐2:CD551‐4 demonstrated a potent inhibitory activity (IC50MAP‐2:CD551‐4 = 2.94, 1.76, and 12.86 nM, respectively). This inhibitory activity was substantially enhanced when pre‐complexes were formed with the lectin pathway recognition molecule mannose‐binding lectin (IC50MAP‐2:CD551‐4 = 0.14 nM). MAP‐2:CD551‐4 was also effective at protecting sensitized sheep erythrocytes in a classical hemolytic assay (CH50 = 13.35 nM). Finally, the chimeric inhibitor reduced neutrophil activation in full blood after stimulation with Aspergillus fumigatus conidia, as well as phagocytosis of conidia by isolated activated neutrophils. Our results demonstrate that MAP‐2:CD551‐4 is a potent complement inhibitor reinforcing the idea that engineered fusion proteins are a promising design strategy for identifying and developing drug candidates to treat complement‐mediated diseases. [ABSTRACT FROM AUTHOR]

• Expression pattern of complement regulatory proteins (CRPs) CD46, CD59, and CD55 in HPV-positive (HPV +) & negative (HPV-) cervical cancer cell lines. • A differential expression profile of CRPs in HPV+ and HPV- cervical cancer cell lines. • A high level of CD59 expression in Hela cells and SiHa cells but low expression in HPV- C33a cells. • CRPs may serve as potential early diagnostic and immune-modulatory markers for HPV-infected cervical cancer. This study aimed to evaluate the expression pattern of complement regulatory proteins (CRPs) CD46, CD59, and CD55 in HPV-positive (HPV+) & negative (HPV-) cervical cancer cell lines in search of a reliable differential biomarker. We analysed the expression of CRPs in HPV 16-positive SiHa cell line, HPV 18-positive HeLa cell line, and HPV-negative cell line C33a using RT-qPCR, Western blotting, flow cytometry, and confocal microscopy. We observed a differential expression profile of CRPs in HPV+ and HPV- cervical cancer cell lines. The mRNA level of CD59 & CD55 showed a higher expression pattern in HPV+ cells when compared to HPV- cancer cells. However, flow cytometry-based experiments revealed that CD46 was preferentially expressed more in HPV 16-positive SiHa cells followed by HPV 18-positive HeLa cells when compared to HPV- C33a cells. Interestingly, confocal microscopy revealed a high level of CD59 expression in Hela cells and SiHa cells but low expression in HPV- C33a cells. In addition, HPV 18-positive HeLa cells expressed more CD55, which was lower in SiHa cells and very weak in C33a cells. The study demonstrates the differential expression of CRPs in both HPV+ and HPV- cervical cancer cells for the first time, and their potential to serve as an early diagnostic marker for cervical carcinogenesis. [ABSTRACT FROM AUTHOR]

Depending on their central metal atom, metalloporphyrins (MPs) can attenuate or exacerbate the severity of immune-mediated kidney injury, and this has been attributed to the induction or inhibition of heme oxygenase (HO) activity, particularly the inducible isoform (HO-1) of this enzyme. The role of central metal or porphyrin moieties in determining the efficacy of MPs to attenuate injury, as well as mechanisms underlying this effect, have not been assessed. Using an antibody-mediated complement-dependent model of injury directed against rat visceral glomerular epithelial cells (podocytes) and two MPs (FePPIX, CoPPIX) that induce both HO-1 expression and HO enzymatic activity in vivo but differ in their chelated metal, we assessed their efficacy in reducing albuminuria. Podocyte injury was induced using rabbit immune serum raised against the rat podocyte antigen, Fx1A, and containing an anti-Fx1A antibody that activates complement at sites of binding. FePPIX or CoPPIX were injected intraperitoneally (5 mg/kg) 24 h before administration of the anti-Fx1A serum and on days 1, 3, 6, and 10 thereafter. Upon completion of urine collection on day 14, the kidney cortex was obtained for histopathology and isolation of glomeruli, from which total protein extracts were obtained. Target proteins were analyzed by capillary-based separation and immunodetection (Western blot analysis). Both MPs had comparable efficacy in reducing albuminuria in males, but the efficacy of CoPPIX was superior in female rats. The metal-free protoporphyrin, PPIX, had minimal or no effect on urine albumin excretion. CoPPIX was also the most potent MP in inducing glomerular HO-1, reducing complement deposition, and preserving the expression of the complement regulatory protein (CRP) CD55 but not that of CD59, the expression of which was reduced by both MPs. These observations demonstrate that the metal moiety of HO-1-inducing MPs plays an important role in reducing proteinuria via mechanisms involving reduced complement deposition and independently of an effect on CRPs. [ABSTRACT FROM AUTHOR]

Nasopharyngeal carcinoma (NPC) is endemic in Southern China and Southeast Asia. Hyperthermia is widely used in combination with chemotherapy and radiotherapy to enhance therapeutic efficacy in NPC treatment, but the underlying anti-tumor mechanisms of hyperthermia remain unclear. Complement C3 has been reported to participate in the activation of immune system in the tumor microenvironment, leading to tumor growth inhibition. In this study, we aimed to explore the effect and mechanisms of hyperthermia and investigate the functional role of complement C3 in NPC hyperthermia therapy (HT). The serum levels of complement C3 before and after hyperthermia therapy in patients with NPC were analyzed. NPC cell lines SUNE1 and HONE1 were used for in vitro experiment to evaluate the function of complement C3 and HT on cell proliferation and apoptosis. SUNE1 xenograft mouse model was established and tumor-bearing mice were treated in water bath at a constant temperature of 43°C. Tumor samples were collected at different time points to verify the expression of complement C3 by immunohistochemical staining and western blot. The differential expressed genes after hyperthermia were analyzed by using RNA sequencing. We found that complement could enhance hyperthermia effect on suppressing proliferation and promoting apoptosis of tumor cells in NPC. Hyperthermia decreased the mRNA expression of complement C3 in tumor cells, but promoted the aggregation and activation circulating C3 in NPC tumor tissue. By using in vitro hyperthermia-treated NPC cell lines and SUNE1 xenograft tumor-bearing mice, we found that the expression of heat shock protein 5 (HSPA5) was significantly upregulated. Knockdown of HSPA5 abrogated the anti-tumor effect of hyperthermia. Moreover, we demonstrated that hyperthermia downregulated CD55 expression via HSPA5/NFκB (P65) signaling and activated complement cascade. Our findings suggest that therapeutic hyperthermia regulates complement C3 activation and suppresses tumor development via HSPA5/NFκB/CD55 pathway in NPC. Complement was involved in the anti-tumor effect of hyperthermia in vitro. Hyperthermia markedly increased the expression of heat shock protein 5 (HSPA5) and decreased the expression of CD55 which regulated the activation of complement C3 and complement cascade. Activation of HSPA5/NFκB (P65) signaling pathway resulted in a decrease in CD55 expression. [ABSTRACT FROM AUTHOR]

Introduction: Expression of human complement pathway regulatory proteins (hCPRP's) such as CD46 or CD55 has been associated with improved survival of pig organ xenografts in multiple different models. Here we evaluate the hypothesis that an increased human CD46 gene dose, through homozygosity or additional expression of a second hCPRP, is associated with increased protein expression and with improved protection from injury when GTKO lung xenografts are perfused with human blood. Methods: Twenty three GTKO lungs heterozygous for human CD46 (GTKO.heteroCD46), 10 lungs homozygous for hCD46 (GTKO.homoCD46), and six GTKO.homoCD46 lungs also heterozygous for hCD55 (GTKO.homoCD46.hCD55) were perfused with human blood for up to 4 h in an ex vivo circuit. Results: Relative to GTKO.heteroCD46 (152 min, range 5–240; 6/23 surviving at 4 h), survival was significantly improved for GTKO.homoCD46 (>240 min, range 45–240, p =.034; 7/10 surviving at 4 h) or GTKO.homoCD46.hCD55 lungs (>240 min, p =.001; 6/6 surviving at 4 h). Homozygosity was associated with increased capillary expression of hCD46 (p <.0001). Increased hCD46 expression was associated with significantly prolonged lung survival (p =.048),) but surprisingly not with reduction in measured complement factor C3a. Hematocrit, monocyte count, and pulmonary vascular resistance were not significantly altered in association with increased hCD46 gene dose or protein expression. Conclusion: Genetic engineering approaches designed to augment hCPRP activity — increasing the expression of hCD46 through homozygosity or co‐expressing hCD55 with hCD46 — were associated with prolonged GTKO lung xenograft survival. Increased expression of hCD46 was associated with reduced coagulation cascade activation, but did not further reduce complement activation relative to lungs with relatively low CD46 expression. We conclude that coagulation pathway dysregulation contributes to injury in GTKO pig lung xenografts perfused with human blood, and that the survival advantage for lungs with increased hCPRP expression is likely attributable to improved endothelial thromboregulation. [ABSTRACT FROM AUTHOR]

Background: Acute graft-versus-host disease (aGvHD) is a life-threatening complication of allogeneic hematopoietic stem cell transplantation (HSCT). Transplantation of immunosuppressive human mesenchymal stromal cells (hMSCs) can protect against aGvHD post-HSCT; however, their efficacy is limited by poor engraftment and survival. Moreover, infused MSCs can be damaged by activated complement, yet strategies to minimise complement injury of hMSCs and improve their survival are limited. Methods: Human MSCs were derived from bone marrow (BM), adipose tissue (AT) and umbilical cord (UC). In vitro immunomodulatory potential was determined by co-culture experiments between hMSCs and immune cells implicated in aGvHD disease progression. BM-, AT- and UC-hMSCs were tested for their abilities to protect aGvHD in a mouse model of this disease. Survival and clinical symptoms were monitored, and target tissues of aGvHD were examined by histopathology and qPCR. Transplanted cell survival was evaluated by cell tracing and by qPCR. The transcriptome of BM-, AT- and UC-hMSCs was profiled by RNA-sequencing. Focused experiments were performed to compare the expression of complement inhibitors and the abilities of hMSCs to resist complement lysis. Results: Human MSCs derived from three tissues divergently protected against aGvHD in vivo. AT-hMSCs preferentially suppressed complement in vitro and in vivo, resisted complement lysis and survived better after transplantation when compared to BM- and UC-hMSCs. AT-hMSCs also prolonged survival and improved the symptoms and pathological features of aGvHD. We found that complement-decay accelerating factor (CD55), an inhibitor of complement, is elevated in AT-hMSCs and contributed to reduced complement activation. We further report that atorvastatin and erlotinib could upregulate CD55 and suppress complement in all three types of hMSCs. Conclusion: CD55, by suppressing complement, contributes to the improved protection of AT-hMSCs against aGvHD. The use of AT-hMSCs or the upregulation of CD55 by small molecules thus represents promising new strategies to promote hMSC survival to improve the efficacy of transplantation therapy. As complement injury is a barrier to all types of hMSC therapy, our findings are of broad significance to enhance the use of hMSCs for the treatment of a wide range of disorders. [ABSTRACT FROM AUTHOR]

BackgroundNeuromyelitis optica spectrum disorder (herein called NMO) is an inflammatory demyelinating disease that can be initiated by binding of immunoglobulin G autoantibodies (AQP4-IgG) to aquaporin-4 on astrocytes, causing complement-dependent cytotoxicity (CDC) and downstream inflammation. The increased NMO pathology in rodents deficient in complement regulator protein CD59 following passive transfer of AQP4-IgG has suggested the potential therapeutic utility of increasing the expression of complement regulator proteins.MethodsA cell-based ELISA was developed to screen for pharmacological upregulators of endogenous CD55 and CD59 in a human astrocyte cell line. A statin identified from the screen was characterized in cell culture models and rodents for its action on complement regulator protein expression and its efficacy in models of seropositive NMO.ResultsScreening of ~ 11,500 approved and investigational drugs and nutraceuticals identified transcriptional upregulators of CD55 but not of CD59. Several statins, including atorvastatin, simvastatin, lovastatin, and fluvastatin, increased CD55 protein expression in astrocytes, including primary cultures, by three- to four-fold at 24 h, conferring significant protection against AQP4-IgG-induced CDC. Mechanistic studies revealed that CD55 upregulation involves inhibition of the geranylgeranyl transferase pathway rather than inhibition of cholesterol biosynthesis. Oral atorvastatin at 10-20 mg/kg/day for 3 days strongly increased CD55 immunofluorescence in mouse brain and spinal cord and reduced NMO pathology following intracerebral AQP4-IgG injection.ConclusionAtorvastatin or other statins may thus have therapeutic benefit in AQP4-IgG seropositive NMO by increasing CD55 expression, in addition to their previously described anti-inflammatory and immunomodulatory actions.

Overexpression of the inducible heme oxygenase (HO-1) isoform in visceral renal glomerular epithelial cells (podocytes) using in vivo transgenesis methods was shown to increase glomerular expression of the complement regulatory protein decay-accelerating factor (DAF, CD55) and reduce complement activation/deposition in a rat model of immune-mediated injury. In this preliminary study, we assessed whether constitutively expressed HO-1 regulates CD55 expression in cultured rat podocytes. We employed methods of flow cytometry, quantitative (q) RT-qPCR and post-transcriptional HO-1 gene silencing (HO-1 interfering RNA, RNAi), to assess changes in constitutive (basal) levels of podocyte HO-1 and CD55 mRNA in cultured rat podocytes. Additionally, the effect of the HO-1 inducer, heme, on HO-1 and CD55 expression was assessed. Results indicate that rat podocytes constitutively express HO-1 and DAF and that the HO-1 inducer, heme, increases both HO-1 and DAF expression. HO-1 gene silencing using RNA interference (RNAi) is feasible but the effect on constitutive CD55 transcription is inconsistent. These observations are relevant to conditions of podocyte exposure to heme that can activate the complementary cascade, as may occur in systemic or intraglomerular hemolysis.

We present a case report of a child with features of hyperphosphatasia with neurologic deficit (HPMRS) or Mabry syndrome (MIM 239300) with variants of unknown significance in two post-GPI attachments to proteins genes, PGAP2 and PGAP3, that underlie HPMRS 3 and 4. Background: In addition to HPMRS 3 and 4, disruption of four phosphatidylinositol glycan (PIG) biosynthesis genes, PIGV, PIGO, PIGW and PIGY, result in HPMRS 1, 2, 5 and 6, respectively. Methods: Targeted exome panel sequencing identified homozygous variants of unknown significance (VUS) in PGAP2 c:284A>G and PGAP3 c:259G>A. To assay the pathogenicity of these variants, we conducted a rescue assay in PGAP2 and PGAP3 deficient CHO cell lines. Results: Using a strong (pME) promoter, the PGAP2 variant did not rescue activity in CHO cells and the protein was not detected. Flow cytometric analysis showed that CD59 and CD55 expression on the PGAP2 deficient cell line was not restored by variant PGAP2. By contrast, activity of the PGAP3 variant was similar to wild-type. Conclusions: For this patient with Mabry syndrome, the phenotype is likely to be predominantly HPMRS3: resulting from autosomal recessive inheritance of NM_001256240.2 PGAP2 c:284A>G, p.Tyr95Cys. We discuss strategies for establishing evidence for putative digenic inheritance in GPI deficiency disorders. [ABSTRACT FROM AUTHOR]

Background: CD55 plays an important role in the development of colon cancer. This study aims to evaluate the expression of CD55 in colon cancer and discover how it is regulated by transcriptional factors and miRNA. Methods: The expression of CD55 was explored by TIMER2.0, UALCAN, and Human Protein Atlas (HPA) databases. TRANSFAC and Contra v3 were used to predict the potential binding sites of transcription factors in the CD55 promoter. TargetScan and starBase v2.0 were used to predict the potential binding ability of miRNAs to the 3' untranslated region (3'UTR) of CD55. SurvivalMeth was used to explore the differentially methylated sites in the CD55 promoter. Western blotting was used to detect the expression of TFCP2 and CD55. Dual-luciferase reporter assay and chromatin immunoprecipitation (ChIP) assay were performed to determine the targeting relationship of TFCP2, NF-κB, or miR-27a-3p with CD55. CD55-related genes were explored by constructing a protein-protein interaction (PPI) network and performing pathway analysis by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Results: CD55 was highly expressed in colon cancer tissues. The mRNA and protein expression levels of TFCP2 were reduced by si-TFCP2. NF-κB mRNA was obviously reduced by NF-κB inhibitor and increased by NF-κB activator. CD55 protein was also inhibited by miR-27a-3p. Dual-luciferase reporter assays showed that after knocking down TFCP2 or inhibiting NF-κB, the promoter activity of CD55 was decreased by 21% and 70%, respectively; after activating NF-κB, the promoter activity of CD55 increased by 2.3 times. As TFCP2 or NF-κB binding site was mutated, the transcriptional activity of CD55 was significantly decreased. ChIP assay showed that TFCP2 and NF-κB combined to the promoter of CD55. The luciferase activity of CD55 3'UTR decreased after being co-transfected with miR-27a-3p mimics and increased by miR-27a-3p antagomir. As the miR-27a-3p binding site was mutated, we did not find any significant effect of miR-27a-3p on reporter activity. PPI network assay revealed a set of CD55-related genes, which included CFP, CFB, C4A, and C4B. GO and KEGG analyses revealed that the target genes occur more frequently in immune-related pathways. Conclusion: Our results indicated that CD55 is regulated by TFCP2, NF-κB, miR-27a-3p, and several immune-related genes, which in turn affects colon cancer. [ABSTRACT FROM AUTHOR]

The overexpression of membrane-bound complement regulatory proteins (mCRPs) on tumour cells helps them survive complement attacks by suppressing antibody-mediated complement-dependent cytotoxicity (CDC). Consequently, mCRP overexpression limits monoclonal antibody drug immune efficacy. CD55, an mCRP, plays an important role in inhibiting antibody-mediated CDC. However, the mechanisms regulating CD55 expression in tumour cells remain unclear. Here, the aim was to explore CD55-targeting miRNAs. We previously constructed an in vitro model comprising cancer cell lines expressing α-gal and serum containing natural antibodies against α-gal and complement. This was used to simulate antibody-mediated CDC in colon cancer cells. We screened microRNAs that directly target CD55 using LoVo and Ls-174T colon cell lines, which express CD55 at low and high levels, respectively. miR-132-3p expression was dramatically lower in Ls-174T cells than in LoVo cells. miR-132-3p overexpression or inhibition transcriptionally regulated CD55 expression by specifically targeting its mRNA 3ʹ-untranslated regions. Further, miR-132-3p modulation regulated colon cancer cell sensitivity to antibody-mediated CDC through C5a release and C5b-9 deposition. Moreover, miR-132-3p expression was significantly reduced, whereas CD55 expression was increased, in colon cancer tissues compared to levels in adjacent normal tissues. CD55 protein levels were negatively correlated with miR-132-3p expression in colon cancer tissues. Our results indicate that miR-132-3p regulates colon cancer cell sensitivity to antibody-mediated CDC by directly targeting CD55. In addition, incubating the LoVo human tumour cell line, stably transfected with the xenoantigen α-gal, with human serum containing natural antibodies comprises a stable and cheap in vitro model to explore the mechanisms underlying antibody-mediated CDC. miR-132-3p regulates CD55 expression by directly targeting the 3ʹ-UTR of CD55, leading to changes in cell sensitivity to Ab-mediated CDC through the release of C5a and deposition of C5b-9. [ABSTRACT FROM AUTHOR]

Enteroviruses cause nearly 1 billion global infections annually and are associated with a diverse array of human illnesses. Among these, myocarditis and the resulting chronic inflammation have been recognized as major contributing factors to virus-induced heart failure. Despite our growing understanding, very limited therapeutic strategies have been developed to address the pathological consequences of virus-induced chronic innate immune activation. Coxsackievirus B3 (CVB3) was used as a model cardiotropic enterovirus. We leveraged in vitro cell-based studies to investigate cardiomyocyte and macrophage interaction during CVB3 infection, as well as animal studies and unique human cardio specimens to evaluate mechanisms of viral heart injury. We present evidence that viral myocarditis is in part exacerbated by pathological activation of the complement pathway in cells, mice, and human cardiac tissues. We demonstrate unique cell type-specific responses to viral infection that are exacerbated by mitochondrial injury in cardiomyocytes and NFκB-dependent pro-inflammatory response in macrophages. Macrophages are robustly activated by damage-associated mitochondrial components, including mitochondrial proteins and lipid extracts. Mechanistically, we identify complement protective factors CD59/protectin and CD55/DAF as novel targets of viral proteinase that acts to release the brakes on complement-mediated autoinjury. Collectively, our study highlights a novel mechanism that can act as a potential contributor to CVB3 pathogenesis through mitochondrial injury-mediated autoimmunity., Importance: This study sheds light on how enteroviruses, specifically coxsackievirus B3, may contribute to heart failure by triggering harmful immune responses in the heart. We discovered that viral infections in heart cells cause mitochondrial damage, which in turn activates a destructive immune response involving the complement system. This immune activation is one of the significant contributors that lead to further injury of heart tissues, worsening the damage caused by the virus. Additionally, we identified key protective molecules that are targeted and disrupted by the virus, allowing the immune system to attack the heart even more aggressively. Understanding these mechanisms may provide additional insights into how viral infections can lead to chronic heart conditions and suggests potential therapeutic targets to prevent or reduce heart damage in patients affected by viral myocarditis.

Background: Gene-edited pigs for xenotransplantation usually contain one or more transgenes encoding human complement regulatory proteins (CRPs). Because of species differences, human CRP(s) expressed in gene-edited pigs may have difficulty inhibiting the activation of exogenous rabbit complement added to a complement-dependent cytotoxicity (CDC) assay. The use of human complement instead of rabbit complement in CDC experiments may more accurately reflect the actual regulatory activity of human CRP(s)., Methods: Peripheral blood mononuclear cells (PBMCs) were obtained from one GTKO pig and two GTKO/hCD55 pigs with a high or low level of hCD55 expression. After incubation of heat-inactivated normal human sera (HINHS) with porcine PBMCs, CDC levels were measured after the addition of commercial rabbit complement or human complement. In addition, a modified one-step CDC method was established using pooled normal human sera (NHS) without the addition of exogenous complement., Results: There was no significant difference in the binding of IgM/IgG to PBMCs from the three pigs. Both rabbit and human complement mediated a significant cytotoxic effect on GTKO pig PBMCs (98.97% vs. 82.73%). Even the high expression of hCD55 only had a very limited inhibitory effect on rabbit complement-mediated cytotoxicity (81.70% vs. 98.97%). However, regardless of whether the expression level was high or low, hCD55 had a very remarkable inhibitory effect on human complement-mediated cytotoxicity (2.94% and 23.83% vs. 82.73%; p < 0.01). Similar results were obtained using the modified one-step CDC method. In addition, the inhibitory effect of hCD55 on C3c and C5b-9 deposition on pig PBMCs was positively correlated with the expression level of hCD55., Conclusion: The use of human complement instead of rabbit complement in CDC assays can better reflect the actual cytotoxic effect of human xenoantibodies against pig PBMCs expressing human CRP(s), and thus may have potential application to gene-edited pig-to-human xenotransplantation., (© 2025 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Introduction: CHAPLE disease is a severe, ultra-rare disorder caused by CD55 gene mutations, leading to uncontrolled complement hyperactivation, protein-losing enteropathy, and systemic thrombosis. Recent advances in targeted therapies, particularly the C5 inhibitor pozelimab (Veopoz), offer new treatment options by addressing complement dysregulation, marking a shift from symptomatic to precision therapy., Areas Covered: This review explores the pathophysiology, clinical manifestations, and current treatments for CHAPLE disease. It examines pozelimab's pharmacological development, its mechanism as a C5 inhibitor, and results from Phase 1 to Phase 3 studies. Additionally, potential use of other anti-C5 therapies and emerging agents targeting proximal complement components are discussed. A systematic literature search using PubMed, Google Scholar, and ClinicalTrials.gov focused on studies from 2017 onwards to provide a comprehensive overview., Expert Opinion: Managing CHAPLE disease requires a combination of targeted anti-complement therapies like pozelimab and supportive measures, including nutritional support and thrombosis management. While pozelimab shows promise in reversing core symptoms, risks like serious infections necessitate preventive measures, such as vaccination and antibiotic prophylaxis. Future research should focus on optimizing dosing, evaluating long-term safety, and assessing the need for lifelong therapy. Expanding our understanding of the disease's pathophysiology will refine treatment strategies and improve outcomes.

Background: Case reports are available showing that patients develop symptoms of acute arthritis during or after recovery from SARS-CoV-2 infection. Since the interrelation is still unknown, our aim was to study the impact of the SARS-CoV-2 nucleocapsid protein (NP) on human fibroblast-like synoviocytes and human endothelial cells (hEC) in terms of complement and cytokine regulation. Methods: Non-arthritic (K4IM) synoviocyte, arthritic (HSE) synoviocyte cell lines and primary hEC were stimulated with recombinant NP and/or TNFα. Analyses of cell viability, proliferation, gene and protein expression of cytokines and complement factors were performed. Results: NP suppressed significantly the vitality of hEC and proliferation of HSE. NP alone did not induce any significant changes in the examined gene expressions. However, NP combined with TNFα induced significantly higher TNFα in HSE and K4IM as well as higher IL-6 and CD55 gene expression in HSE and suppressed C3aR1 gene expression in hEC. HSE proliferated twice as fast as K4IM, but showed significantly lesser gene expressions of CD46, CD55, CD59 and TNFα with significantly higher IL-6 gene expression. CD35 gene expression was undetectable in K4IM, HSE and hEC. Conclusions: NP might contribute in combination with other inflammatory factors to complement regulation in arthritis. [ABSTRACT FROM AUTHOR]

High‐level expression of decay‐accelerating factor, CD55, has previously been found in human gastric cancer (GC) and intestinal metaplasia (IM) tissues. Therapeutic effects of CD55 inhibition in cancer have been reported. However, the role of Helicobacter pylori infection and virulence factors in the induction of CD55 and its association with histological changes of the human gastric mucosa remain incompletely understood. We hypothesised that CD55 would be increased during infection with more virulent strains of H. pylori, and with more marked gastric mucosal pathology. RT‐qPCR and immunohistochemical analyses of gastric biopsy samples from 42 H. pylori‐infected and 42 uninfected patients revealed that CD55 mRNA and protein were significantly higher in the gastric antrum of H. pylori‐infected patients, and this was associated with the presence of IM, but not atrophy, or inflammation. Increased gastric CD55 and IM were both linked with colonisation by vacA i1‐type strains independently of cagA status, and in vitro studies using isogenic mutants of vacA confirmed the ability of VacA to induce CD55 and sCD55 in gastric epithelial cell lines. siRNA experiments to investigate the function of H. pylori‐induced CD55 showed that CD55 knockdown in gastric epithelial cells partially reduced IL‐8 secretion in response to H. pylori, but this was not due to modulation of bacterial adhesion or cytotoxicity. Finally, plasma samples taken from the same patients were analysed for the soluble form of CD55 (sCD55) by ELISA. sCD55 levels were not influenced by IM and did not correlate with gastric CD55 mRNA levels. These results suggest a new link between active vacA i1‐type H. pylori, IM, and CD55, and identify CD55 as a molecule of potential interest in the management of IM as well as GC treatment. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland. [ABSTRACT FROM AUTHOR]

Agustin Pasqual Dalmasso died in December 2021. He was 88 years old and an Honorary Member of the International Xenotransplantation Association. Gus made seminal contributions to understanding and overcoming the barrier complement system poses to xenotransplantation. Those endeavoring to advance xenotransplantation to clinical application and those seeking the most topics in which to devote their life's work could do no better than examining how Gus approached the subjects of his life's work. [ABSTRACT FROM AUTHOR]

Background: Targeted knock-in assisted by the CRISPR/Cas9 system is an advanced technology with promising applications in various research fields including medical and agricultural sciences. However, improvements in the efficiency, precision, and specificity of targeted knock-in are prerequisites to facilitate the practical application of this technology. To improve the efficiency of targeted knock-in, it is necessary to have a molecular system that allows sensitive monitoring of targeted knock-in events with simple procedures. Methods and results: We developed an assay, named CD55 correction assay, with which to monitor CD55 gene correction accomplished by targeted knock-in. To create the reporter clones used in this assay, we initially introduced a 7.7-kb heterozygous deletion covering CD55 exons 2–5, and then incorporated a truncating mutation within exon 4 of the remaining CD55 allele in human cell lines. The resultant reporter clones that lost the CD55 protein on the cell membrane were next transfected with Cas9 constructs along with a donor plasmid carrying wild-type CD55 exon 4. The cells were subsequently stained with fluorescence-labeled CD55 antibody and analyzed by flow cytometry to detect CD55-positive cells. These procedures allow high-throughput, quantitative detection of targeted gene correction events occurring in an endogenous human gene. Conclusions: The current study demonstrated the utility of the CD55 correction assay to sensitively quantify the efficiency of targeted knock-in. When used with the PIGA correction assay, the CD55 correction assay will help accurately determine the efficiency of targeted knock-in, precluding possible experimental biases caused by cell line-specific and locus-specific factors. [ABSTRACT FROM AUTHOR]

The complement system is an essential component of the innate immune defence that, if overly activated, may damage organs and tissues. For this reason, there is a fine complement regulatory system. The complement modulation system includes two proteins with important regulatory activity, CD55 or decay accelerating factor (DAF) and CD59 or membrane inhibitor of reactive lysis (MIRL). The paroxysmal nocturnal hemoglobinuria (PNH) is a clonal and non-neoplastic disease characterized by intravascular haemolysis, occurrence of thrombosis and bone marrow failure. In clinical practice, in opposition to PNH, a variety of pathological conditions have been observed with an acquired and non-genetic deficiency of the regulatory proteins CD55 and CD59. This abnormal, non-clonal, reduced expression of complement regulatory proteins configures what we may define as PNH-like phenotype. Similarly to PNH, even in the PNH-like phenotype diseases there has been a greater exposure to the mediated complement cellular lysis and, a likely increased risk of thromboembolic events. Therefore, the knowledge of the potential roles of the complement system becomes necessary for a deeper understanding of several pathological conditions and for an improved clinical management of the patients. [ABSTRACT FROM AUTHOR]

Objective: To investigate the expression of S100A4 and decay-accelerating factor(CD55) in gastrointestinal stromal tu-mors (GIST) and their relationship with clinicopathological parameters and prognosis. Methods: From January 2011 to December 2015, 124 cases of GIST tissue and corresponding adjacent normal tissue pathological wax block in Jiangbei District of Southwest Hospital Affiliated to Army Medical University/958 Hospital of PLA were selected, which were surgically resected and pathologically confirmed. Immunohistochemistry was used to detect the expression of S100A4 and CD55 in GIST tissue and adjacent normal tissues. The relation-ship between the expression of S100A4 and CD55 and clinicopathological parameters and prognosis of GIST patients was analyzed. Results: The high expression rates of S100A4 and CD55 in GIST tissues were significantly higher than those in adjacent normal tissues (P<0.05). The expression of S100A4 and CD55 were correlated with tumor size, mitotic phase, NIH grade and distant metastasis (P<0.05), but not with age, gender, location and histological type (P>0.05). The recurrence rate and metastasis rate of GIST patients with low expression of S100A4 and CD55 were lower than those with high expression of S100A4 and CD55,and the difference was statistically significant (P<0.05); the 5-years median progression free survival of patients with low expression of S100A4 and CD55 was significantly higher than those with high expression of S100A4 and CD55, and the difference was statistically significant (P<0.05). Conclusion: S100A4 and CD55 are highly expressed in GIST tissues, which may be involved in the invasion and metastasis of gist and related to the prognosis of patients after operation. [ABSTRACT FROM AUTHOR]

Dalia Mahmoud Eldewi,1 Alshaymaa M Alhabibi,1 Hanaa Mohammed Eid El Sayed,2 Sammar Ahmed Kasim Mahmoud,2 Sanaa Mohammed El Sadek,3 Rasha Mahmoud Gouda,3 Mohammed Abd El Malik Hassan,4 Amal H Ibrahim,2 Naglaa F Abd El Haliem5 1Clinical Pathology Department, Faculty of Medicine for Girls, Al-Azhar University, Cairo, Egypt; 2Internal Medicine Department, Faculty of Medicine for Girls, Al-Azhar University, Cairo, Egypt; 3Pediatric Department, Faculty of Medicine for Girls, Al-Azhar University, Cairo, Egypt; 4Pediatric Department, Faculty of Medicine for Boys, Al-Azhar University, Cairo, Egypt; 5Medical Microbiology and Immunology Department, Faculty of Medicine for Girls, Al-Azhar University, Cairo, EgyptCorrespondence: Alshaymaa M AlhabibiClinical Pathology Department, Faculty of Medicine for Girls, Al-Azhar University, Cairo 11765, EgyptTel +20 100 289 4075Email Elshymaamohamed.medg@azhar.edu.egBackground: Altered regulation of the complement system is associated with multiple kidney diseases. CD35, CD55 and CD59 regulate the complement system, and changes in their expression have previously been linked with kidney disease. This study assessed whether changes in the expression levels of these proteins are associated specifically with chronic kidney disease (CKD) to understand its pathogenesis.Materials and methods: Sixty CKD patients and 60 age-matched controls were enrolled and divided into two groups: Group I (n=30 pediatric patients and n=30 controls) and Group II (n=30 adult patients and n=30 controls). The expression of CD35, CD55 and CD59 on peripheral blood cells was evaluated by flow cytometry as the proportion of positive cells expressing the marker and mean fluorescence intensity (MFI), also the relation of these markers to the stage of CKD was also evaluated.Results: Pediatric and adult CKD patients had significantly lower proportion of erythrocytes expressing CD35, CD55 and CD59 than healthy controls (P

Abstract Background Neuromyelitis optica spectrum disorder (herein called NMO) is an inflammatory demyelinating disease that can be initiated by binding of immunoglobulin G autoantibodies (AQP4-IgG) to aquaporin-4 on astrocytes, causing complement-dependent cytotoxicity (CDC) and downstream inflammation. The increased NMO pathology in rodents deficient in complement regulator protein CD59 following passive transfer of AQP4-IgG has suggested the potential therapeutic utility of increasing the expression of complement regulator proteins. Methods A cell-based ELISA was developed to screen for pharmacological upregulators of endogenous CD55 and CD59 in a human astrocyte cell line. A statin identified from the screen was characterized in cell culture models and rodents for its action on complement regulator protein expression and its efficacy in models of seropositive NMO. Results Screening of ~ 11,500 approved and investigational drugs and nutraceuticals identified transcriptional upregulators of CD55 but not of CD59. Several statins, including atorvastatin, simvastatin, lovastatin, and fluvastatin, increased CD55 protein expression in astrocytes, including primary cultures, by three- to four-fold at 24 h, conferring significant protection against AQP4-IgG-induced CDC. Mechanistic studies revealed that CD55 upregulation involves inhibition of the geranylgeranyl transferase pathway rather than inhibition of cholesterol biosynthesis. Oral atorvastatin at 10–20 mg/kg/day for 3 days strongly increased CD55 immunofluorescence in mouse brain and spinal cord and reduced NMO pathology following intracerebral AQP4-IgG injection. Conclusion Atorvastatin or other statins may thus have therapeutic benefit in AQP4-IgG seropositive NMO by increasing CD55 expression, in addition to their previously described anti-inflammatory and immunomodulatory actions.

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INTRODUCTION: Paroxysmal nocturnal hemoglobinuria (PNH) is an uncommon disease. Many cases go undiagnosed as high index of clinical suspicion is required for its detection. This study was performed to detect the presence of PNH defect by flow cytometric immunophenotyping (FCMI) in patients with suspected PNH disease and evaluate their clinical and laboratory profile. MATERIALS AND METHODS: In this retrospective study, a total of 136 patients with suspected PNH who fulfilled the inclusion criteria for the study were evaluated for PNH defect by FCMI using monoclonal antibodies against CD55 and CD59 on red blood cell, granulocytes, and monocytes. RESULTS: Forty-eight (35.3%) of 136 patients evaluated had a PNH defect. Nineteen (39.5%) of these 48 patients had classical PNH (hemolytic type). The remaining 29 patients had PNH Clone in association with aplastic anemia. The clinical and laboratory data of these 19 patients with classical PNH were analyzed in this retrospective study. The median age was 34 years (range: 19–65 years). Thrombotic events were observed in 3 (16%) of the 19 cases (one each with Budd–Chiari syndrome, cerebral venous thrombosis, and abdominal vein thrombosis). The flow cytometric data of these patients were further analyzed for the presence of and size of PNH clone on erythrocytes, granulocytes, and monocytes. PNH clone was detected in 84% of erythrocytes, 76.9 % of monocytes and in 100% granulocytes. CONCLUSION: Classical PNH is not rare in India as previously thought. A high index of clinical suspicions and evaluation by FCMI is necessary for its detection. CD59 is a better marker for identification of PNH clone than CD55 in all three cell types.

Aim of the study : β-thalassaemia (β-Thal) is considered a severe, progressive haemolytic anaemia, which needs regular blood transfusions for life expectancy. Complement-mediated erythrocyte destruction can cause both intravascular and extravascular haemolysis. Complement regulatory proteins protect cells from such effects of the complement system. We aimed to perform quantitative analysis of membrane-bound complement regulators, CD55 (decay accelerating factor – DAF), CD35 (complement receptor type 1 – CR1), and CD59 (membrane attack complex inhibitory factor – MACIF) on peripheral red blood cells by flow cytometry. Material and methods: The present study was carried out on 47 β-thalassemia major (β-TM) patients, 20 β-thalassaemia intermedia (β-TI) patients, and 17 healthy volunteers as control subjects. Results : CD55 levels of β-TM patients (58.64 ±17.06%) were significantly decreased compared to β-TI patients (83.34 ±13.82%) and healthy controls (88.57 ±11.69%) (p < 0.01). CD59 levels of β-TM patients were not significantly different than β-TI patients and controls, but CD35 levels were significantly lower in the β-TM patients (3.56 ±4.87%) and β-TI patients (12.48 ±9.19%) than in the control group (39.98 ±15.01%) (p < 0.01). Conclusions : Low levels of CD55 and CD35 in thalassaemia major patients indicates a role for them in the aetiopathogenesis of haemolysis in this disease, and also this defect in a complement system may be responsible for the chronic complications seen in these patients.

In a recent report, the cellular receptor CD55 was identified as a molecule essential for the invasion of human erythrocytes by Plasmodium falciparum, the causal agent of the most severe form of malaria. As this invasion process represents a critical step during infection with the parasite, it was hypothesized that genetic variants in the gene could affect severe malaria (SM) susceptibility. We performed high-resolution variant discovery of rare and common genetic variants in the human CD55 gene. Association testing of these variants in over 1700 SM cases and unaffected control individuals from the malaria-endemic Ashanti Region in Ghana, West Africa, were performed on the basis of single variants, combined rare variant analyses, and reconstructed haplotypes. A total of 26 genetic variants were detected in coding and regulatory regions of CD55. Five variants were previously unknown. None of the single variants, rare variants, or haplotypes showed evidence for association with SM or P. falciparum density. Here, we present the first comprehensive analysis of variation in the CD55 gene in the context of SM and show that genetic variants present in a Ghanaian study group appear not to influence susceptibility to the disease.

Influenza remains an important threat for human health, despite the extensive study of influenza viruses and the production of effective vaccines. In contrast to virus genetics determinants, host genetic factors with clinical impact remained unexplored until recently. The association between three single nucleotide polymorphisms (SNPs) and influenza outcome in a European population was investigated in the present study. All samples were collected during the influenza A(H1N1)pdm09 post-pandemic period 2010–11 and a sufficient number of severe and fatal cases was included. Host genomic DNA was isolated from pharyngeal samples of 110 patients from northern Greece with severe (n = 59) or mild (n = 51) influenza A(H1N1)pdm09 disease, at baseline, and the genotype of CD55 rs2564978, C1QBP rs3786054 and FCGR2A rs1801274 SNPs was investigated. Our findings suggest a relationship between the two complement-related SNPs, namely, the rare TT genotype of CD55 and the rare AA genotype of C1QBP with increased death risk. No significant differences were observed for FCGR2A genotypes neither with fatality nor disease severity. Additional large-scale genetic association studies are necessary for the identification of reliable host genetic risk factors associated with influenza A(H1N1)pdm09 outcome. Prophylactic intervention of additional high-risk populations, according to their genetic profile, will be a key achievement for the fight against influenza viruses. [ABSTRACT FROM AUTHOR]