Multiple sclerosis (MS) is an inflammatory demyelinating disease of central nervous system, with unknown etiology. Our recent studies unveiled an association between Epstein-Barr virus (EBV) genomic variants and MS, reinforcing the idea that EBV contributes to disease development. In an analysis of a region of the viral DNA coding for Epstein-Barr nuclear antigen 2 (EBNA2) protein, we showed that MS risk significantly correlated with an excess of 1.2 allele and under-representation of 1.3B allele.
Besides EBNA2, other loci of the complex EBV genome may impact on MS pathophysiology. In an exploratory study (granted by Ricerca di Ateneo 2013) where we completely sequenced EBV genomes derived from spontaneously outgrowing lymphoblastoid cell lines (spLCLs) of patients and healthy donors (HD), we observed that other EBV variants may be relevant for MS. Based on this background, our objective is to confirm the data on EBNA2 alleles association with MS, and to ascertain the statistical significance of other possible MS-associated EBV genomic variants. We aim to analyze a large and independent cohorts of 250 relapsing-remitting MS patients and age/sex matched HD with different geographic origin. For this purpose, we will analyse viral DNA obtained from blood samples with a digital droplet PCR (ddPCR-granted by Medie attrezzature 2015) approach that is precise and accurate, fast and affordable for screenings conducted on large populations.
The last decade witnessed a terrific increase of therapeutic options for multiple sclerosis. Although the new drugs offer opportunity to better keep in check the disease progression, this is often at the cost of safety concerns. Moreover, the current therapeutic approaches target the underlying (especially immune-mediated) pathogenic mechanisms, while an actual etiologic therapy is still missing. The origin of MS is considered complex, and due the interplay between multiple genetic and environmental factors. Hence, clarifying the role of an environmental factor such as EBV latent infection (concordantly, a major risk for MS development), waiting for understanding how to target the scattered and often elusive genetic elements, seems of relevance for MS management.
The polymorphisms we found in the EBNA2 gene may have functional consequences as supported by recent data showing that a single amino acid in EBNA2 determines superior B lymphoblastoid cell line growth maintenance [9]. The allelic variants we described may affect the host-virus interplay at different levels: a) the same region is involved in interactions with cellular proteins such as Nur77 [10] and SMARCB1 [11] that have been associated with MS susceptibility [12] and antiviral responses [13]; b) the gene region we investigated is important for successful strategies of EBV immune evasion [14]; c) last, but not least, the EBNA2 mRNA, where we found MS-related variants, belongs to the targetome of human micro-RNAs that may serve to keep in check EBV infection [15].
These results may be complementary to our recent studies showing that a portion of the genetic predisposition to MS may be attributable to variants in genes that interact with EBV [7]. Specifically, EBNA2 binding motifs resulted to be significantly enriched in genomic intervals associated with MS, showing a striking overlap with Vitamin D receptor (VDR) binding sites [16], suggesting that a complex interplay between both host and viral genetic variants may contribute to disease development.
Apart from the predictive potential of EBNA2 variants, the likelihood that these variants and others, may induce functional consequences, possibly contributing to disease etiology, deserves consideration. In a virus that is not prone to mutations, [17] new variants are more likely to have a functional impact and may be used as disease biomarker and/or therapeutic targets (Italian Patent: 0001417523; PCT/IB2014/060489).