Anti-aquaporin-4 autoantibodies in systemic lupus erythematosus persist for years and induce astrocytic cytotoxicity but not CNS disease

• Anti-AQP4 antibodies were investigated in SLE patients without neurological disease.
• Two patients were positive, including archived samples, while patient antibodies induced damage in cultured astrocytes.
• It is unclear why neurological disease has not been induced by the persisting AQP4-antibodies.

Anti-aquaporin-4 autoantibodies are specific for the neuromyelitis optica spectrum disorders (NMOSD) and they have also been described in patients with systemic lupus erythematosus (SLE) with neurological signs consistent with NMOSD. Our objective was to test for the presence and pathogenicity of anti-AQP4 antibodies in SLE patients without neurological disease.Sera from 89 non-CNS-SLE patients were screened for anti-AQP4 autoantibodies. Two of the 89 patients were positive. Archived samples dating back 11 years were also positive. A brain and spinal cord MRI did not reveal any NMOSD-compatible lesions. An in vitro cytotoxicity assay showed that either sera or purified IgG from these patients induced a complement-mediated damage in cultured astrocytes comparable to antibodies obtained from typical NMO patients.We conclude that AQP4-antibodies can be present in SLE patients and persist for many years, without concurrent clinical or radiological NMOSD signs. It is unclear why the anti-AQP4 antibodies did not induce CNS disease.

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