Biomarkers and viral risk factors in multiple sclerosis

Sammanfattning: Multiple sclerosis (MS) is a chronic inflammatory disease resulting in axonal injury and demyelination of nerve fibers in the central nervous system. The causal factor and pathological mechanisms governing disease progression have remained elusive, limiting the available clinical tools for MS diagnosis and treatment monitoring, particularly in the periphery. In the following studies, we investigated potential [1] protein biomarkers capable of differentiating MS and characterizing disease activity and [2] serological biomarkers that may predict MS risk or adverse events associated with immunomodulatory treatment. Studies I-III measured proteins in cerebrospinal fluid (CSF) and plasma using a highsensitivity proximity extension immunoassay to characterize the differential protein profile associated with MS. Although many require further validation, several proteins in CSF (e.g., IL12B and CD79B) and plasma (e.g., OSM) show promise in differentiating early stages of MS and assessing progressive disease, relapse activity, and severity of disability progression. Many also complement current diagnostic tools for MS, including oligoclonal bands, IgG index, and MRI T2 lesions. Measures were responsive to common disease-modifying drugs, including natalizumab and fingolimod, indicating the potential for monitoring treatment efficacy. Lastly, in Study IV, we characterized the susceptibility of several of these inflammation-related proteins to sample processing conditions, a necessary consideration for reliable usage in clinical practice. In Study V, we showed high anti-EBNA1 IgG levels (Epstein-Barr virus, EBV), particularly against the aa385-420 peptide fragment, were associated with an increased risk for MS, independent of any history of infectious mononucleosis. Genome-wide association analysis showed HLA as the primary genetic risk factor for high EBNA-1/VCAp18 antibody response, particularly the MS risk haplotype with DRB1'15:01. A bi-directional relationship between EBV and MS genetic susceptibility was observed, with genetic susceptibility to high EBNA- 1 IgG resulting in an increased risk for MS and vice versa. Overlapping HLA associations with MS and previous auto-antigen studies may indicate the role of molecular mimicry. Study VI identified genetic risk factors affecting JC polyomavirus (JCV) seropositivity, a risk assessment measure for progressive multifocal leukoencephalopathy (PML). In addition to HLA, genetic polymorphisms in the FUT2 and ABO genes, corresponding with secretor status and blood group phenotypes, were associated with anti-JCV(VP1) IgG levels. These findings indicate a potential neutralization effect of ABH antigens against JCV. However, further investigation is needed to assess the implications of HLA and blood phenotypes in the risk assessment of PML, particularly for MS treatment.