Dr Sean Burnard

Conventional genome-wide association studies (GWASs) of complex traits, such as Multiple Sclerosis (MS), are reliant on per-SNP p-values and are therefore heavily burdened by multiple testing correction. Thus, in order to detect more subtle alterations, ever increasing sample sizes are required, while ignoring potentially valuable information that is readily available in existing datasets. To overcome this, we used penalised regression incorporating elastic net with a stability selection method by iterative subsampling to detect the potential interaction of loci with MS risk. Through re-analysis of the ANZgene dataset (1617 cases and 1988 controls) and an IMSGC dataset as a replication cohort (1313 cases and 1458 controls), we identified new association signals for MS predisposition, including SNPs above and below conventional significance thresholds while targeting two natural killer receptor loci and the well-established HLA loci. For example, rs2844482 (98.1% iterations), otherwise ignored by conventional statistics (p = 0.673) in the same dataset, was independently strongly associated with MS in another GWAS that required more than 40 times the number of cases (~45 K). Further comparison of our hits to those present in a large-scale meta-analysis, confirmed that the majority of SNPs identified by the elastic net model reached conventional statistical GWAS thresholds (p < 5 × 10-8 ) in this much larger dataset. Moreover, we found that gene variants involved in oxidative stress, in addition to innate immunity, were associated with MS. Overall, this study highlights the benefit of using more advanced statistical methods to (re-)analyse subtle genetic variation among loci that have a biological basis for their contribution to disease risk.

Multiple Sclerosis (MS) is a chronic neurological disease with genetic and environmental risk factors. Epstein Barr-Virus (EBV) has been closely associated with MS but with a significant amount of conflicting evidence. Some of the evidence for EBV involvement in MS includes: almost 100% of MS patients showing past EBV infection, an association with Infectious Mononucleosis (acute EBV infection), higher titres of EBV antibodies associated with an increased risk of MS development, and an overall altered immune response to EBV found in peripheral blood and the CNS of MS patients. However, evidence for EBV presence in the CSF and T cell responses to EBV in MS have been particularly conflicting. Several hypotheses have been proposed for direct and indirect EBV involvement in MS such as 1) Molecular Mimicry 2) Mistaken Self 3) Bystander Damage and 4) Autoreactive B cells infected with EBV. More recently, an association between EBV and human endogenous retrovirus in MS has been shown, which may provide an alternative pathogenetic target for MS treatment. However, if EBV is not the major contributor to MS and is instead one of several viral or infectious agents able to elicit a similar altered immune response, MS development may be the result of a failure of viral clearance in general. This review aims to evaluate the evidence for the currently discussed theories of EBV involvement in MS pathogenesis.