Introduction: Antibodies to the extracellular domain of the astrocytic aquaporin-1 (AQP-1) have been reported in patients with neuromyelitis optica spectrum disorder (NMOSD) and a few multiple sclerosis (MS) patients with predominant spinal cord involvement. Our aim was to identify the prevalence and clinical correlates of antibodies against AQP1 (AQP1-Abs) in a broader spectrum of autoimmune inflammatory demyelinating central nervous system (CNS) disorders.
Methods: Sera from patients with NMOSD (n=30), recurrent inflammatory optic neuropathy (RION) (n=15), relapsing remitting MS (RRMS) (n=69), of which 10 had optic neuritis and/or short myelitis, and healthy controls (n=36) were screened for the presence of AQP1-Abs by ELISA and for antibodies against aquaporin-4 (AQP4-Abs) and myelin oligodendrocyte glycoprotein (MOG)-Abs by cell-based assays.
Results: AQP1-Abs were found in 11% of patients with optic neuritis and/or myelitis [6.7% of NMOSD, 13.3% of RION and 20% of RRMS with optic neuritis and/or short myelitis]. None of the RRMS patients without optic neuritis and/or short myelitis and none of the healthy controls had AQP1-Abs. The two AQP1-Abs-positive RRMS patients, who fulfilled Barkhof criteria by virtue of MRI lesion distribution, had experienced ≥4 short myelitis and/or optic neuritis attacks.
Conclusion: AQP1-Abs are occasionally detected in autoimmune inflammatory demyelinating CNS disorders highlighting optic nerve and spinal cord involvement.
Keywords: Aquaporin-1, neuromyelitis, multiple sclerosis, antibody,