Targeted complement inhibition salvages stressed neurons and inhibits neuroinflammation after stroke in mice

• Published in: Science translational medicine Vol. 10; no. 441
• Main Authors: Alawieh, Ali, Langley, E Farris, Tomlinson, Stephen
• Format: Journal Article
• Language: English
• Published: United States 16.05.2018
• Subjects: Animals; Brain Ischemia - complications; Brain Ischemia - drug therapy; Brain Ischemia - pathology; Brain Ischemia - physiopathology; Complement Activation; Complement System Proteins - metabolism; Disease Models, Animal; Disease Susceptibility; Immunoglobulin M - metabolism; Infarction, Middle Cerebral Artery - complications; Infarction, Middle Cerebral Artery - drug therapy; Infarction, Middle Cerebral Artery - pathology; Infarction, Middle Cerebral Artery - physiopathology; Inflammation - complications; Inflammation - etiology; Inflammation - pathology; Ischemia - pathology; Mice; Mice, Inbred C57BL; Microglia - metabolism; Microglia - pathology; Nerve Degeneration - complications; Nerve Degeneration - pathology; Nerve Degeneration - physiopathology; Neurons - drug effects; Neurons - pathology; Neuroprotective Agents - pharmacology; Neuroprotective Agents - therapeutic use; Opsonin Proteins - metabolism; Phagocytosis - drug effects; Pneumonia - complications; Pneumonia - pathology; Proto-Oncogene Proteins c-fos - metabolism; Recovery of Function - drug effects; Stroke - complications; Stroke - drug therapy; Stroke - pathology; Stroke - physiopathology; Time Factors
• ISSN: 1946-6242
• DOI: 10.1126/scitranslmed.aao6459

Ischemic stroke results from the interruption of blood flow to the brain resulting in long-term motor and cognitive neurological deficits, and it is a leading cause of death and disability. Current interventions focus on the restoration of blood flow to limit neuronal death, but these treatments have a therapeutic window of only a few hours and do not address post-stroke cerebral inflammation. The complement system, a component of the innate immune system, is activated by natural immunoglobulin M (IgM) antibodies that recognize neoepitopes expressed in the brain after ischemic stroke. We took advantage of this recognition system to inhibit complement activation locally in the ischemic area in mice. A single chain antibody recognizing a post-ischemic neoepitope linked to a complement inhibitor (termed B4Crry) was administered systemically as a single dose after stroke and shown to specifically target the ischemic hemisphere and improve long-term motor and cognitive recovery. We show that complement opsonins guide microglial phagocytosis of stressed but salvageable neurons, and that by locally and transiently inhibiting complement deposition, B4Crry prevented phagocytosis of penumbral neurons and inhibited pathologic complement and microglial activation that otherwise persisted for several weeks after stroke. B4Crry was protective in adult, aged, male and female mice and had a therapeutic window of at least 24 hours after stroke. Furthermore, the epitope recognized by B4Crry in mice is overexpressed in the ischemic penumbra of acute stroke patients, but not in the contralateral tissue, highlighting the translational potential of this approach.