Neuromyelitis optica study model based on chronic infusion of autoantibodies in rat cerebrospinal fluid

Abstract

BackgroundDevic’s neuromyelitis optica (NMO) is an autoimmune astrocytopathy, associated with central nervous system inflammation, demyelination, and neuronal injury. Several studies confirmed that autoantibodies directed against aquaporin-4 (AQP4-IgG) are relevant in the pathogenesis of NMO, mainly through complement-dependent toxicity leading to astrocyte death. However, the effect of the autoantibody per se and the exact role of intrathecal AQP4-IgG are still controversial.MethodsTo explore the intrinsic effect of intrathecal AQP4-IgG, independent from additional inflammatory effector mechanisms, and to evaluate its clinical impact, we developed a new animal model, based on a prolonged infusion of purified immunoglobulins from NMO patient (IgGAQP4+, NMO-rat) and healthy individual as control (Control-rat) in the cerebrospinal fluid (CSF) of live rats.ResultsWe showed that CSF infusion of purified immunoglobulins led to diffusion in the brain, spinal cord, and optic nerves, the targeted structures in NMO. This was associated with astrocyte alteration in NMO-rats characterized by loss of aquaporin-4 expression in the spinal cord and the optic nerves compared to the Control-rats (p = 0.001 and p = 0.02, respectively).In addition, glutamate uptake tested on vigil rats was dramatically reduced in NMO-rats (p = 0.001) suggesting that astrocytopathy occurred in response to AQP4-IgG diffusion. In parallel, myelin was altered, as shown by the decrease of myelin basic protein staining by up to 46 and 22 % in the gray and white matter of the NMO-rats spinal cord, respectively (p = 0.03). Loss of neurofilament positive axons in NMO-rats (p = 0.003) revealed alteration of axonal integrity. Then, we investigated the clinical consequences of such alterations on the motor behavior of the NMO-rats. In a rotarod test, NMO-rats performance was lower compared to the controls (p = 0.0182). AQP4 expression, and myelin and axonal integrity were preserved in AQP4-IgG-depleted condition. We did not find a major immune cell infiltration and microglial activation nor complement deposition in the central nervous system, in our model.ConclusionsWe establish a link between motor-deficit, NMO-like lesions and astrocytopathy mediated by intrathecal AQP4-IgG. Our study validates the concept of the intrinsic effect of autoantibody against surface antigens and offers a model for testing antibody and astrocyte-targeted therapies in NMO.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0577-8) contains supplementary material, which is available to authorized users.

Absence of antibodies against KIR4.1 in multiple sclerosis: A three-technique approach and systematic review

“…One study[19] was not included due to lack of normal controls (S1 Fig). Compared with studies in healthy controls, three studies in MS patients showed an association of positivity of anti-KIR4.1[10,11,14] and seven studies, including our own, showed no significant differences[12,13,16,20,21,27–29] (Fig 4). The statistical heterogeneity between studies was over 75% and did not allow data pooling to perform meta-analysis.…”

“…The studies were developed in the USA (3)[15,16,20], Germany (2)[10,11], France (2)[12,27], Japan (2)[28,29], Israel (1)[14], Italy (1)[21], Spain (1), Switzerland (1)[19], and Turkey (1)[13]. They showed substantial variability in the technical determination of anti-KIR4.1 and control group populations.…”

“…They showed substantial variability in the technical determination of anti-KIR4.1 and control group populations. The methodological quality was qualified as week in five studies[13,21,27–29], moderate in four studies[11,16,20,30] plus our own, and strong in three studies[10,14,15]. One study[19] was not included due to lack of normal controls (S1 Fig).…”

“…Importantly, these studies did not identify clinical, radiological or therapeutic features that were specifically associated with the presence of anti-KIR4.1 antibodies in MS patients. The results from early replication studies using the KIR4.1 extracellular loop (residues 83–120) peptide to test anti-KIR4.1 antibodies by ELISA were insufficiently consistent to demonstrate a clear association of anti-KIR4.1 and MS even though the same detection assay was used[12,27]. A thorough replication study including a multimodal approach also failed to confirm the association of anti-KIR4.1 antibodies with MS[16].…”

Experimental animal models of aquaporin‐4‐IgG‐seropositive neuromyelitis optica spectrum disorders: progress and shortcomings

“…Curiously, similar pathology was seen in rats pre‐treated with cobra venom factor, suggesting a complement‐independent mechanism. A related model involved continuous intraventricular infusion of patient‐derived AQP4‐IgG for 7 days by osmotic mini‐pump . Human IgG was seen in brain, spinal cord and optic nerve, with the loss of AQP4 and reactive astrocytes in spinal cord and optic nerve, and demyelination and axonal injury in spinal cord.…”