Plasma complement biomarkers distinguish multiple sclerosis and neuromyelitis optica spectrum disorder

Background: Multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD) are autoimmune demyelinating diseases distinguished clinically by selective involvement in NMOSD of optic nerves and spinal cord. Early clinical manifestations are similar, complicating clinical management. Aquaporin-4 autoantibody measurement aids diagnosis of NMOSD but is frequently negative, creating unmet need for alternative biomarkers. Objective: We investigated whether plasma complement proteins are altered in MS and NMOSD and whether these provide biomarkers that reliably distinguish the diseases. Methods: Plasma from 53 NMOSD, 49 MS and 69 control donors was tested in multiplex assays measuring complement activation products and proteins. Logistic regression was used to test whether combinations of complement analyte measurements distinguish NMOSD from controls and MS. Results: All activation products were significantly elevated in NMOSD compared to either control or MS. Four complement proteins (C1inh, C1s, C5, FH) were significantly higher in NMOSD compared to MS or controls. A model comprising C1 inhibitor and TCC distinguished NMOSD from MS (area under curve (AUC) 0.98), while C1 inhibitor and C5 distinguished NMOSD from controls (AUC 0.94). Conclusions: NMOSD is distinguished from MS by plasma complement activation

Complement biomarkers as predictors of disease progression in Alzheimer's disease

There is a critical unmet need for reliable markers of disease and disease course in mild cognitive impairment (MCI) and early Alzheimer’s disease (AD). The growing appreciation of the importance of inflammation in early AD has focused attention on inflammatory biomarkers in cerebrospinal fluid or plasma; however, non-specific inflammation markers have disappointed to date. We have adopted a targeted approach, centered on an inflammatory pathway already implicated in the disease. Complement, a core system in innate immune defense and potent driver of inflammation, has been implicated in pathogenesis of AD based on a confluence of genetic, histochemical, and model data. Numerous studies have suggested that measurement of individual complement proteins or activation products in cerebrospinal fluid or plasma is useful in diagnosis, prediction, or stratification, but few have been replicated. Here we apply a novel multiplex assay to measure five complement proteins and four activation products in plasma from donors with MCI, AD, and controls. Only one complement analyte, clusterin, differed significantly between control and AD plasma (controls, 295 mg/l; AD, 388 mg/l: p < 10- 5). A model combining clusterin with relevant co-variables was highly predictive of disease. Three analytes (clusterin, factor I, terminal complement complex) were significantly different between MCI individuals who had converted to dementia one year later compared to non-converters; a model combining these three analytes with informative co-variables was highly predictive of conversion. The data confirm the relevance of complement biomarkers in MCI and AD and build the case for using multi-parameter models for disease prediction and stratification

Systemic complement profiling in multiple sclerosis as a biomarker of disease state

Background: There is increasing evidence of significant and dynamic systemic activation and upregulation of complement in multiple sclerosis (MS), which may contribute to disease pathogenesis. Objective: We aimed to investigate the pathological role of complement in MS and the potential role for complement profiling as a biomarker of MS disease state. Methods: Key components of the classical, alternative and terminal pathways of complement were measured in plasma and cerebrospinal fluid (CSF) of patients with MS in different clinical phases of disease and in matched controls. Results: Increased plasma levels of C3 (p<0.003), C4 (p<0.001), C4a (p<0.001), C1 inhibitor (p<0.001), and factor H (p<0.001), and reduced levels of C9 (p<0.001) were observed in MS patients compared with controls. Combined profiling of these analytes produced a statistical model with a predictive value of 97% for MS and 73% for clinical relapse when combined with selected demographic data. CSF-plasma correlations suggested that source of synthesis of these components was both systemic and central. Conclusion: These data provide further evidence of alterations in both local and systemic expression and activation of complement in MS and suggest that complement profiling may be informative as a biomarker of MS disease, although further work is needed to determine its use in distinguishing MS from its differential

Tissue-specific host recognition by complement factor H is mediated by differential activities of its glycosaminoglycan-binding regions

Complement factor H (CFH) regulates complement activation in host tissues through its recognition of polyanions, which mediate CFH binding to host cell surfaces and extracellular matrix, promoting the deactivation of deposited C3b. These polyanions include heparan sulfate (HS), a glycosaminoglycan (GAG) with a highly diverse range of structures, for which two regions of CFH (referred to as CCP6-8 and CCP19-20) have been implicated in HS binding. Mutations/polymorphisms within these GAG-binding sites have been associated with age-related macular degeneration (AMD) and atypical hemolytic uremic syndrome (aHUS). Here we demonstrate that CFH has tissue-specific binding properties, mediated through its two HS-binding regions. Our data shows that the CCP6-8 region of CFH binds more strongly to heparin (a highly sulfated form of HS) than CCPs19-20 and that their sulfate specificities are different. Furthermore, the HS-binding site in CCPs6-8, which is affected by the AMD-associated Y402H polymorphism, plays the principle role in host tissue recognition in the human eye, whilst the CCP19-20 region makes the major contribution to the binding of CFH in the human kidney. This helps provide a biochemical explanation for the genetic basis of tissue-specific diseases such as AMD and aHUS, and leads to a better understanding of the pathogenic mechanisms for these diseases of complement dysregulation

Dendritic cells promote the spread of human T-cell leukemia virus type 1 via bidirectional interactions with CD4+ T cells

Human T-cell leukemia virus type-1 (HTLV-1) propagates within and between individuals via cell-to-cell transmission, and primary infection typically occurs across juxtaposed mucosal surfaces during breastfeeding and sexual intercourse. It is therefore likely that dendritic cells (DCs) are among the first potential targets for HTLV-1. However, it remains unclear how DCs contribute to virus transmission and dissemination in the early stages of infection. We show that an HTLV-1-infected cell line (MT-2) and naturally-infected CD4+ T-cells transfer p19+ viral particles to the surface of allogeneic DCs via cell-to-cell contacts. Similarly organized cell-to-cell contacts facilitate DC-mediated transfer of HTLV-1 to autologous CD4+ T-cells. These findings shed light on the cellular structures involved in anterograde and retrograde transmission, and suggest a key role for DCs in the natural history and pathogenesis of HTLV-1 infection

C3 Glomerulopathy and related disorders in children

Background and objectives: Membranoproliferative Glomerulonephritis (MPGN) and C3 Glomerulopathy are rare and overlapping disorders associated with dysregulation of the alternative complement pathway. Specific aetiological data for paediatric MPGN/C3 glomerulopathy are lacking, and outcome data are based upon retrospective studies without aetiological data. Design, setting, participants, and measurements: Eighty prevalent pediatric patients with MPGN/C3 glomerulopathy underwent detailed phenotyping and long-term follow-up within the National Registry of Rare Kidney Diseases (RaDaR). Risk factors for kidney survival were determined using COX proportional hazards model. Kidney and transplant graft survival was determined using Kaplan-Meier method. Results: Central histology review determined 39 C3 glomerulopathy, 31 immune-complex MPGN and 10 immune-complex glomerulonephritis (GN) cases. Patients were aged 2-15 (median 9 (IQR 7-11) years. Median complement C3 and C4 levels were 0.31g/L and 0.14g/L respectively; acquired (anti-complement autoantibodies) or genetic alternative pathway abnormalities were detected in 46% and 9% patients respectively, across all groups including immune-complex GN. Median follow-up was 5.18 (IQR 2.13-8.08) years. Eleven patients (14%) progressed to kidney failure with 9 transplants performed in 8 patients, 2 of which failed due to recurrent disease. Presence of >50% crescents on initial biopsy was the sole variable associated with kidney failure in multivariable analysis (Hazard Ratio 6.2, p = 0.045; 95% CI 1.05 to 36.6). Three distinct C3 glomerulopathy prognostic groups were identified according to presenting eGFR and >50% crescents on initial biopsy. Conclusions: Crescentic disease was a key risk factor associated with kidney failure in a national cohort of pediatric MPGN/C3 glomerulopathy and immune-complex GN. Presenting eGFR and crescentic disease help define prognostic groups in pediatric C3 glomerulopathy. Acquired abnormalities of the alternative pathway were commonly identified but not a risk factor for kidney failure

Thrombotic and bleeding complications in patients with chronic lymphocytic leukemia and severe COVID-19: a study of ERIC, the European Research Initiative on CLL

BACKGROUND: Patients with chronic lymphocytic leukemia (CLL) may be more susceptible to COVID-19 related poor outcomes, including thrombosis and death, due to the advanced age, the presence of comorbidities, and the disease and treatment-related immune deficiency. The aim of this study was to assess the risk of thrombosis and bleeding in patients with CLL affected by severe COVID-19. METHODS: This is a retrospective multicenter study conducted by ERIC, the European Research Initiative on CLL, including patients from 79 centers across 22 countries. Data collection was conducted between April and May 2021. The COVID-19 diagnosis was confirmed by the real-time polymerase chain reaction (RT-PCR) assay for SARS-CoV-2 on nasal or pharyngeal swabs. Severe cases of COVID-19 were defined by hospitalization and the need of oxygen or admission into ICU. Development and type of thrombotic events, presence and severity of bleeding complications were reported during treatment for COVID-19. Bleeding events were classified using ISTH definition. STROBE recommendations were used in order to enhance reporting. RESULTS: A total of 793 patients from 79 centers were included in the study with 593 being hospitalized (74.8%). Among these, 511 were defined as having severe COVID: 162 were admitted to the ICU while 349 received oxygen supplementation outside the ICU. Most patients (90.5%) were receiving thromboprophylaxis. During COVID-19 treatment, 11.1% developed a thromboembolic event, while 5.0% experienced bleeding. Thrombosis developed in 21.6% of patients who were not receiving thromboprophylaxis, in contrast to 10.6% of patients who were on thromboprophylaxis. Bleeding episodes were more frequent in patients receiving intermediate/therapeutic versus prophylactic doses of low-molecular-weight heparin (LWMH) (8.1% vs. 3.8%, respectively) and in elderly. In multivariate analysis, peak D-dimer level and C-reactive protein to albumin ratio were poor prognostic factors for thrombosis occurrence (OR?=?1.022, 95%CI 1.007?1.038 and OR?=?1.025, 95%CI 1.001?1.051, respectively), while thromboprophylaxis use was protective (OR?=?0.199, 95%CI 0.061?0.645). Age and LMWH intermediate/therapeutic dose administration were prognostic factors in multivariate model for bleeding (OR?=?1.062, 95%CI 1.017-1.109 and OR?=?2.438, 95%CI 1.023-5.813, respectively). CONCLUSIONS: Patients with CLL affected by severe COVID-19 are at a high risk of thrombosis if thromboprophylaxis is not used, but also at increased risk of bleeding under the LMWH intermediate/therapeutic dose administration

Elevated plasma C4a levels in multiple sclerosis correlate with disease activity

Complement plays a pivotal role in the pathogenesis of multiple sclerosis. C4a, an activated fragment of complement component C4, has been linked to disease activity. We correlated plasma C4 and plasma and CSF C4a with clinical disease in a well-characterised cohort of patients and controls. Plasma C4 was non-significantly and CSF C4a was significantly elevated overall in patients compared to controls. Plasma C4a was raised only in acute relapse, decreasing over 2 months. Results demonstrate intrathecal and systemic activation of complement, reflected in changes in CSF and plasma C4a. The data support a role for complement activation in pathogenesis and suggest a systemic component to the disease

Complement regulator factor H in multiple sclerosis

A recent proteomic study published in this journal demonstrated lower cerebrospinal fluid (CSF) expression of factor H (fH), an important complement regulator, along with two other complement proteins, in active multiple sclerosis (MS) patients. We have previously demonstrated raised serum fH levels in MS and here, an extended analysis, quantifying fH in CSF, demonstrates no change in fH levels in active disease, but significantly raised levels in progressive disease. These findings support our previous work showing raised serum fH in patients with progressive MS, and our results predict that CSF fH levels will be raised rather than reduced in active disease

Variant-specific quantification of factor H in plasma identifies null alleles associated with atypical Hemolytic Uremic Syndrome

7 páginas, 6 figuras -- PAGS nros. 782-788Atypical hemolytic uremic syndrome (aHUS) is associated with complement alternative pathway defects in over half the cases. Point mutations that affect complement surface regulation are common in factor H (CFH); however, sometimes individuals have null mutations in heterozygosis. The latter are difficult to identify, although a consistently low plasma factor H (fH) concentration is suggestive; definitive proof requires demonstration that the mutant sequence is not expressed in vitro. Here, novel reagents and assays that distinguish and individually quantify the common factor H-Y402H polymorphic variants were used to identify alleles of the CFH gene, resulting in low or null expression of full-length fH and also normal or increased expression of the alternative splice product factor H-like-1 (FHL-1). Our assay identified three Y402H heterozygotes with low or absent fH-H402 but normal or increased FHL-1-H402 levels in a cohort of affected patients. Novel mutations explained the null phenotype in two cases, which was confirmed by family studies in one. In the third case, family studies showed that a known mutation was present on the Y allele. The cause of reduced expression of the H allele was not found, although the data suggested altered splicing. In each family, inheritance of low expression or null alleles for fH strongly associated with aHUS. Thus, our assays provide a rapid means to identify fH expression defects without resorting to gene sequencing or expression analysisThis work was supported by the UK Multiple Sclerosis Society no 884/08 (to BPM), MRC Project Grant no. 84908 (to CLH and BPM), and Ministerio de Ciencia e Innovación SAF 2005-00913, the CIBER de Enfermedades Raras and Fundación Renal Iñigo Alvarez de Toledo (to SRdeC)Peer reviewe