Development and evaluation of an in-house assay for anti-myelin oligodendrocyte glycoprotein antibody

Abstract

Introduction: Myelinoligodendrocyte glycoprotein (MOG) was contributing for about 0.05% of total myelin proteins. It was a transmembrane protein located on the surface of the myelin sheath and oligodendrocytes. Although the functioning role of MOG was remaining unclear, it was identified as an important autoantigen in demyelinating disease. Therefore anti-MOG antibody had raised many researches about its pathogenic and diagnostic roles.

Anti-MOG could be found in a wide spectrum of acquired central nervous system (CNS) inflammatory demyelinating diseases. It was mainly detected in paediatric patients and Acute Disseminated Encephalomyelitis (ADEM) patients. It could also be commonly found in anti-aquaporin-4 (anti-AQP4)-seronegative Neuromyelitis Optica Spectrum Disorder (NMOSD), isolated or recurrent optic neuritis (ON) and transverse myelitis (TM). Unlike most autoimmune diseases, anti-MOG associated demyelinating diseases were male predominant or even chance varying from different studies. The recovery of anti-MOG seropositive patients in generally was better than anti-MOGseronegative patients. Currently, there was no definitive evidence between anti-MOG and disease progression or severity. However, anti-MOG seropositivity could indicate the case was likely to be autoantibody based acute demyelinating syndrome instead of multiple sclerosis (MS). Anti-MOG associated demyelinating patients showed a rapid response to steroids and plasma exchange treatment.

In this study, an in-house live cell based assay (CBA) was used to test serum samples for anti-MOG and anti-AQP4. The gene and protein expression in the transfected cell lines was confirmed with reverse transcription polymerase chain reaction (RT-PCR) and Western Blot. The live CBA results would be evaluated with commercial indirect immunofluorescence assay (IIFA). The live CBA was believed to be the golden standard method to detect anti-MOG and anti-AQP4.

Aims: This study aimed to develop an in-house live CBA to detect anti-MOG antibody. The assay would be evaluated with a commercial IIFA.

Methods: 111 serum samples were obtained from the Division of Clinical Immunology laboratory of Queen Mary Hospital. The laboratory had already tested anti-AQP4 with commercial IIFA and established the AQP4-transfected cell line. The samples were selected based on the clinical diagnosis. The samples included suspected or confirmed MS, ADEM, NMOSD, isolated, recurrent ON or TM. In this study, all the samples were tested with commercial anti-MOG IIFA kit. In addition, in-house live CBA was tested for both anti-AQP4 and anti-MOG.

Results: RT-PCR and Western Blot results confirmed that the cells were successfully transfected. For anti-MOG, both commercial IIFA and in-house live CBA showed comparable results. The results agreed with the statistics of other studies in terms of disease distribution, sex and age. Conclusion: A stable cell line was successfully established for the in-house live CBA to detect anti-MOG. The results were comparable to commercial IIFA. The in-house live CBAwas considered as aslightly better detection methodthan IIFA in terms of sensitivity. This serological biomarker was useful in a wide spectrum of acquired CNS inflammatory demyelinating diseases.