Increased CSF sulfatide levels and serum glycosphingolipid antibody levels in healthy siblings of multiple sclerosis patients

Abstract

A proportion of healthy siblings of multiple sclerosis (MS) patients have an oligoclonal immunological reaction in their cerebrospinal fluid (CSF) termed the “MS oligoclonal trait”. The CSF levels of the major myelin glycosphingolipid sulfatide and serum antibodies against the glycosphingolipids sulfatide and galactosylceramide were recently reported to be increased in MS patients. We studied the levels of these substances in pairs of 46 patients and their 46 healthy siblings and 50 unrelated healthy blood donors (HBD). The sulfatide concentration in CSF was assayed by thin layer chromatography and immunostaining, and the concentration of galactosylceramide by densitometry after thin layer chromatography. Anti-glycosphingolipid antibody levels were assayed by ELISA. In the healthy siblings, the CSF sulfatide concentrations were markedly increased (p < 0.001, age adjusted p = 0.025), and the serum IgM anti-GalCer antibodies were increased in healthy siblings compared with HBD (p = 0.02). The increased sulfatide or antibody levels did not co-segregate with the “MS oligoclonal trait” or the HLA-DR15 phenotype. In conclusion, a proportion of healthy siblings of MS patients have increased CSF sulfatide and anti-glycosphingolipid antibody levels, which may, analogous to the “MS oligoclonal trait”, constitute an “MS glycosphingolipid endophenotype”. Endophenotypes could potentially simplify the genetics of complex disorders.

Introduction

Healthy first degree relatives (FDR) of patients with complex autoimmune disorders carry, to a variable degree, autoantibodies identical to those of their affected relatives [1], [2]. The frequency of such asymptomatic individuals may be higher than the frequency of affected relatives [3]. Many FDR of MS patients harbor antiviral antibodies with specificities identical to those known to occur in MS [4] or a cerebrospinal fluid (CSF) enriched oligoclonal IgG reaction with undefined specificity, which (in the relevant clinical context) supports an MS diagnosis, a condition termed “MS trait” [5], [6]. Haghighi et al. found measles antibodies and an “MS oligoclonal trait” in approximately 20% of FDR [7], [8].

Immunoreactivity against several glycolipids was previously demonstrated in MS [9], [10], and we recently reported that the CSF levels of the myelin glycosphingolipid (GSL) sulfatide and serum antibodies against the GSL sulfatide and galactosylceramide (GalCer) are increased in relapsing-remitting and progressive MS patients [7], [11]. In the present study, we further investigate the levels of these GSLs and their corresponding antibodies in the healthy siblings of MS patients compared with healthy blood donors (HBD) as controls. We observed that CSF sulfatide levels and serum anti-GSL antibodies are increased in a large proportion of healthy siblings of MS patients. We examined whether these features in healthy siblings fulfill the criteria for an MS endophenotype, and whether they co-segregate with the previously reported “MS oligoclonal trait” [7] and an established genetic risk factor for MS, the HLA-DR15 genotype [12].