Serum autoantibodies to myelin peptides distinguish acute disseminated encephalomyelitis from relapsing-remitting multiple sclerosis

Abstract

Background and objective: Acute disseminated encephalomyelitis (ADEM) and relapsing-remitting multiple sclerosis (RRMS) share overlapping clinical, radiologic and laboratory features at onset. Because autoantibodies may contribute to the pathogenesis of both diseases, we sought to identify autoantibody biomarkers that are capable of distinguishing them.

Methods: We used custom antigen arrays to profile anti-myelin-peptide autoantibodies in sera derived from individuals with pediatric ADEM (n = 15), pediatric multiple sclerosis (Ped MS; n = 11) and adult MS (n = 15). Using isotype-specific secondary antibodies, we profiled both IgG and IgM reactivities. We used Statistical Analysis of Microarrays software to confirm the differences in autoantibody reactivity profiles between ADEM and MS samples. We used Prediction Analysis of Microarrays software to generate and validate prediction algorithms, based on the autoantibody reactivity profiles.

Results: ADEM was characterized by IgG autoantibodies targeting epitopes derived from myelin basic protein, proteolipid protein, myelin-associated oligodendrocyte basic glycoprotein, and alpha-B-crystallin. In contrast, MS was characterized by IgM autoantibodies targeting myelin basic protein, proteolipid protein, myelin-associated oligodendrocyte basic glycoprotein and oligodendrocyte-specific protein. We generated and validated prediction algorithms that distinguish ADEM serum (sensitivity 62-86%; specificity 56-79%) from MS serum (sensitivity 40-87%; specificity 62-86%) on the basis of combined IgG and IgM anti-myelin autoantibody reactivity to a small number of myelin peptides.

Conclusions: Combined profiles of serum IgG and IgM autoantibodies identified myelin antigens that may be useful for distinguishing MS from ADEM. Further studies are required to establish clinical utility. Further biological assays are required to delineate the pathogenic potential of these antibodies.

Keywords: Pediatric disease; acute disseminated encephalomyelitis; autoantibody; autoimmune disease; biomarker; differential diagnosis; immunoassay; immunoglobulin; multiple sclerosis; myelin.

Figure 1. Differences in IgG and IgM autoantibody reactivity differentiate between ADEM and MS

SAM-generated heatmaps highlight differences between IgM- and IgG-specific autoantibody reactivity between serum samples from patients with pediatric ADEM, adult MS, or pediatric MS. Individual patients are listed above the heat map and the individual antigens are listed to the right of the heat map. Autoantibody reactivities are conveyed with blue, yellow, and red hues representing low, medium, and high reactivity respectively. Differences in serum IgG (A) and IgM (B) reactivity between patients with ADEM and patients with adult MS. Differences in serum IgG (C) and IgM (D) reactivity between patients with ADEM and patients with pediatric MS. Q values for individual SAM analyses are 8.8% in A, 23.1% in B, 16.7% in C, and 33.3% in D. MOBP, myelin-associated oligodendrocyte basic protein; abCrys, alpha-B-crystallin; PLP, proteolipid protein; OSP, oligodendrocyte specific protein; MBP, myelin basic protein; CNPase, 2’,3’ cyclic nucleotide phosphodiesterase.

Figure 2. Performance of serum autoantibody profiles in the differential diagnosis of ADEM and MS

We used PAM to generate and validate prediction algorithms based on autoantibody reactivity profiles. For prediction on Cohort 1 (starting top left), we generated an algorithm (antigens and scores as listed) by ‘training’ PAM using the reactivity profiles from Cohort 2. We validated this algorithm using the autoantibody reactivity profiles from Cohort 1. The prediction accuracy of the algorithm is listed at the bottom left. To further test the validity of our autoantibody prediction paradigm, we reversed the order of training and validation (starting bottom right) such that the training analysis was done using reactivity profiles from Cohort 1 and validated using serum samples from Cohort 2. Shown in bold are the IgG-targeted antigens that differentiated between ADEM and MS in both prediction trials. There were no overlapping patients in Cohorts 1 & 2. SN, sensitivity; SP, specificity; MOBP, myelin-associated oligodendrocyte basic protein; abCrys, alpha-B-crystallin; PLP, proteolipid protein; OSP, oligodendrocyte specific protein; MBP, myelin basic protein; CNPase, 2’,3’ cyclic nucleotide phosphodiesterase, MOG, myelin oligodendrocyte glycoprotein.