Association of Complement Factors With Disability Progression in Primary Progressive Multiple Sclerosis.

BACKGROUND AND OBJECTIVES: The complement system is known to play a role in multiple sclerosis (MS) pathogenesis. However, its contribution to disease progression remains elusive. The study investigated the role of the complement system in disability progression of patients with primary progressive MS (PPMS). METHODS: Sixty-eight patients with PPMS from 12 European MS centers were included in the study. Serum and CSF levels of a panel of complement components (CCs) were measured by multiplex enzyme-linked immunosorbent assay at a baseline time point (i.e., sampling). Mean (SD) follow-up time from baseline was 9.6 (4.8) years. Only one patient (1.5%) was treated during follow-up. Univariable and multivariable logistic regressions adjusted for age, sex, and albumin quotient were performed to assess the association between baseline CC levels and disability progression in short term (2 years), medium term (6 years), and long term (at the time of the last follow-up). RESULTS: In short term, CC played little or no role in disability progression. In medium term, an elevated serum C3a/C3 ratio was associated with a higher risk of disability progression (adjusted OR 2.30; 95% CI 1.17-6.03; p = 0.040). By contrast, increased CSF C1q levels were associated with a trend toward reduced risk of disability progression (adjusted OR 0.43; 95% CI 0.17-0.98; p = 0.054). Similarly, in long term, an elevated serum C3a/C3 ratio was associated with higher risk of disability progression (adjusted OR 1.81; 95% CI 1.09-3.40; p = 0.037), and increased CSF C1q levels predicted lower disability progression (adjusted OR 0.41; 95% CI 0.17-0.86; p = 0.025). DISCUSSION: Proteins involved in the activation of early complement cascades play a role in disability progression as risk (elevated serum C3a/C3 ratio) or protective (elevated CSF C1q) factors after 6 or more years of follow-up in patients with PPMS. The protective effects associated with C1q levels in CSF may be related to its neuroprotective and anti-inflammatory properties.

Thrombin-activatable fibrinolysis inhibitor influences disease severity in humans and mice with pneumococcal meningitis.

BACKGROUND: Mortality and morbidity in patients with bacterial meningitis result from the proinflammatory response and dysregulation of coagulation and fibrinolysis. Thrombin-activatable fibrinolysis inhibitor (TAFI) is activated by free thrombin or thrombin in complex with thrombomodulin, and plays an antifibrinolytic role during fibrin clot degradation, but also has an anti-inflammatory role by inactivating proinflammatory mediators, such as complement activation products. OBJECTIVE: To assess the role of TAFI in pneumococcal meningitis. METHODS: We performed a prospective nationwide genetic association study in patients with bacterial meningitis, determined TAFI and complement levels in cerebrospinal fluid (CSF), and assessed the function of TAFI in a pneumococcal meningitis mouse model by using Cpb2 (TAFI) knockout mice. RESULTS: Polymorphisms (reference sequences: rs1926447 and rs3742264) in the CPB2 gene, coding for TAFI, were related to the development of systemic complications in patients with pneumococcal meningitis. Higher protein levels of TAFI in CSF were significantly associated with CSF complement levels (C3a, iC3b, and C5b-9) and with more systemic complications in patients with bacterial meningitis. The risk allele of rs1926447 (TT) was associated with higher levels of TAFI in CSF. In the murine model, consistent with the human data, Cpb2-deficient mice had decreased disease severity, as reflected by lower mortality, and attenuated cytokine levels and bacterial outgrowth in the systemic compartment during disease, without differences in the brain compartment, as compared with wild-type mice. CONCLUSIONS: These findings suggest that TAFI plays an important role during pneumococcal meningitis, which is likely to be mediated through inhibition of the complement system, and influences the occurrence of systemic complications and inflammation.

Complement activation and intraventricular rituximab distribution in recurrent central nervous system lymphoma.

PURPOSE: To elucidate the mechanistic basis for efficacy of intrathecal rituximab. We evaluated complement activation as well as the pharmacokinetics of intraventricular rituximab in patients who participated in two phase 1 multicenter studies. EXPERIMENTAL DESIGN: We evaluated complement activation as a candidate mediator of rituximab within the central nervous system (CNS). Complement C3 and C5b-9 were quantified by ELISA in serial cerebrospinal fluid (CSF) specimens after intraventricular rituximab administration. We determined rituximab concentration profiles in CSF and serum. A population three- compartment pharmacokinetic model was built to describe the disposition of rituximab following intraventricular administration. The model was derived from results of the first trial and validated with results of the second trial. RESULTS: Complement C3 and C5b-9 were reproducibly activated in CSF after intraventricular rituximab. Ectopic expression of C3 mRNA and protein within CNS lymphoma lesions was localized to myeloid cells. Constitutive high C3 activation at baseline was associated with adverse prognosis. A pharmacokinetic model was built, which contains three distinct compartments, to describe the distribution of rituximab within the neuroaxis after intraventricular administration. CONCLUSIONS: We provide the first evidence of C3 activation within the neuroaxis with intraventricular immunotherapy and suggest that complement may contribute to immunotherapeutic responses of rituximab in CNS lymphoma. Penetration of rituximab into neural tissue is supported by this pharmacokinetic model and may contribute to efficacy. These findings have general implications for intraventricular immunotherapy. Our data highlight potential innovations to improve efficacy of intraventricular immunotherapy both via modulation of the innate immune response as well as innovations in drug delivery.

Increased soluble C5b-9 in CSF of neuromyelitis optica.

Neuromyelitis optica (NMO) and multiple sclerosis (MS) are two of the autoimmune inflammatory demyelinating diseases in the central nervous system. Complement is thought to have an important role in pathogenesis of these diseases, especially in NMO. However, the change of terminal complement complex (TCC, C5b-9) in patients with NMO is still unclear. Cerebrospinal fluid (CSF) C3a, C5a, sC5b-9 were measured by enzyme-linked immunosorbent assay in patients with NMO (n = 26), MS (n = 25) and other neurological disease (OND, n = 19). CSF levels of C5a in patients with NMO were higher than patients with OND (P = 0.006). Increased CSF sC5b-9 were found in the patients with NMO compared with patients with MS (P = 0.029) and OND (P = 0.0001). CSF sC5b-9 in patients with MS were also higher than patients with OND (P = 0.030). Patients with NMO revealed a trend to an increased disease disability with increased CSF sC5b-9 during relapse but not in MS (NMO: P = 0.006, MS: P = 0.097). CSF levels of sC5b-9 are increased in patients with NMO and reflect the activation of complement in NMO.

Complement activation in circulation and central nervous system after rituximab (anti-CD20) treatment of B-cell lymphoma.

Rituximab (IDEC-C2B8, Mabthera, Rituxan), a chimeric monoclonal antibody against the B-cell specific CD20-antigen, has been demonstrated to be effective in the treatment of non-Hodgkin's B-cell lymphoma (B-NHL). Previous in vitro studies have shown that direct complement-dependent cytotoxicity (CDC), ADCC and apoptosis are important in the rituximab-induced killing of lymphoma cells. It is, however, unknown whether rituximab penetrates the blood-brain barrier. Therefore, we studied rituximab levels and complement (C) activation in blood and cerebrospinal fluid (CSF) following intravenous rituximab therapy in a patient with relapsing non-Hodgkin's lymphoma with central nervous system (CNS) involvement. Longitudinal samples from blood and CSF were taken at 13 time-points during the treatment period. The results show that the C cascade becomes activated in blood during the first mAb infusion (C3a-desArg concentration rose from 55 to 138 microg/ml during the first 2 hours). After the first infusion the proportions of lymphocytes positive for the CD19- and CD20-antigens in the peripheral blood were reduced from 41% and 35%, respectively, to a level of 2% (for both). In CSF the rituximab concentration increased after successive infusions, but remained below 0.55 microg/ml (compared to a Cmax of 400 microg/ml in peripheral blood). Although a minor and delayed C activation response was seen in the CSF the treatment did not clear CD20-positive cells away from the CNS. Thus, it appears that an intact blood-brain barrier restricts the entry of rituximab into the CNS. Possible options to circumvent this would be dose escalation or intrathecal rituximab treatment.

Cerebrospinal fluid C3a increases with age, but does not increase further in Alzheimer's disease.

Complement activation is present in the brain in Alzheimer's disease (AD), and C1q concentrations are decreased in AD cerebrospinal fluid (CSF). To determine whether concentrations of other complement proteins are also altered in AD CSF, we measured concentrations of C3a and SC5b-9 in CSF from patients with probable AD (n = 19), normal aged controls (n = 11), and normal younger controls (n = 15). C3a concentrations were similar between AD and aged controls, but threefold higher than in younger controls (p < 0.05 vs. both groups). A similar pattern was found with SC5b-9, though the increase was only twofold and statistically significant only for AD vs. younger controls. These results suggest that an increased generation of complement proteins in localized areas of the AD brain does not result in elevated concentrations of these proteins in CSF, compared with age-matched controls. Increased C3a (and, to a lesser extent, SC5b-9) in aged controls may be due to increased complement activation, increased central nervous system production, and/or blood-brain barrier leakage of these proteins.

Activated complement components C3a and C4a in cerebrospinal fluid and plasma following subarachnoid hemorrhage.

The cerebrospinal fluid (CSF) and plasma levels of the complement components C3a and C4a in 40 patients suffering from subarachnoid hemorrhage (SAH) were quantitated by radioimmunoassay. Serial measurements of the lumbar CSF levels revealed that the C3a and C4a levels were significantly elevated in the initial stage of SAH, but decreased rapidly. Within 48 hours after SAH, the mean C3a and C4a levels in the cisternal, lumbar, and ventricular CSF were significantly higher in patients with delayed ischemic neurological deficits (DIND) than in those without DIND. The serially measured plasma levels of C3a and C4a in patients with DIND were elevated more than in those without DIND, but they did not show a significant change over time. Simultaneous levels of fibrinopeptide A (FPA), an indicator of thrombin activity in CSF, were also measured by radioimmunoassay. There was a significant correlation between CSF-activated complement components and CSF FPA. These results suggest that complement activation occurred in the subarachnoid space soon after SAH, chiefly due to activation of the coagulation system. The higher CSF levels of C3a and C4a in patients with DIND may indicate a relationship between these components and the pathogenesis of cerebral vasospasms.