Marked central nervous system pathology in CD59 knockout rats following passive transfer of Neuromyelitis optica immunoglobulin G

Neuromyelitis optica spectrum disorders (herein called NMO) is an inflammatory demyelinating disease of the central nervous system in which pathogenesis involves complement-dependent cytotoxicity (CDC) produced by immunoglobulin G autoantibodies targeting aquaporin-4 (AQP4-IgG) on astrocytes. We reported evidence previously, using CD59(-/-) mice, that the membrane-associated complement inhibitor CD59 modulates CDC in NMO (Zhang and Verkman, J. Autoimmun. 53: 67-77, 2014). Motivated by the observation that rats, unlike mice, have human-like complement activity, here we generated CD59(-/-) rats to investigate the role of CD59 in NMO and to create NMO pathology by passive transfer of AQP4-IgG under conditions in which minimal pathology is produced in normal rats. CD59(-/-) rats generated by CRISPR/Cas9 technology showed no overt phenotype at baseline except for mild hemolysis. CDC assays in astrocyte cultures and cerebellar slices from CD59(-/-) rats showed much greater sensitivity to AQP4-IgG and complement than those from CD59(+/+) rats. Intracerebral administration of AQP4-IgG in CD59(-/-) rats produced marked NMO pathology, with astrocytopathy, inflammation, deposition of activated complement, and demyelination, whereas identically treated CD59+/+ rats showed minimal pathology. A single, intracisternal injection of AQP4-IgG in CD59(-/-) rats produced hindlimb paralysis by 3 days, with inflammation and deposition of activated complement in spinal cord, optic nerves and brain periventricular and surface matter, with most marked astrocyte injury in cervical spinal cord. These results implicate an important role of CD59 in modulating NMO pathology in rats and demonstrate amplification of AQP4-IgG-induced NMO disease with CD59 knockout.