The specificity of B-cell response in multiple sclerosis

Abstract

One of the pathological features of multiple sclerosis (MS) is the presence of a long lived chronic inflammation in the central nervous system (CNS) with presence of oligoclonal IgG and IgM bands (OCBs) in the cerebrospinal fluid (CSF) derived from clonally expanded B cells. In my PhD I have tested the hypothesis that the intrathecal B cells response is antigen driven and screened putative candidate antigenic epitopes. Materials and methods: Brain tissues were supplied from The UK Multiple Sclerosis Tissue Bank. Total RNA was extracted from the brain tissues from 14 patients with MS after homogenization of the snap frozen blocks and cDNA obtained. VH and VL fragments were amplified from IgM and IgG and cloned in an in house vector to build a phage display single chain fragment variable (scFv) antibody library. The library was used to analyse the VH and VL usage, somatic mutation and clonal expansion in the MS brain and to select for scFv specific to putative autoantigens candidates. Results and discussion: Two libraries of VH only and VH plus VL gene segments from MS brain’s B cells were built. The sequences analysis has revealed a biased usage of VH and VL and evidence of clonal expansion thus supporting an antigen driven response. The auto-antigen candidates chosen for screening the libraries were the myelin basic protein (MBP)-proteolipid protein (PLP) fusion protein MP4 and specific binders were selected as highlighted with monoclonal phage ELISA. Conclusion: A MS disease specific phage display antibody library was built to facilitate the analysis of the disease specific V gene usage in the MS brain. Selection using this library has provided a proof of concept that this library is functional. The library will be used in the future to identify human antibody fragments against candidate autoantigens either for diagnostic or therapeutic applications.