Naturally Presented Peptides on Major Histocompatibility Complex I and II Molecules Eluted from Central Nervous System of Multiple Sclerosis Patients

Abstract

Tandem mass spectrometry was used to identify naturally processed peptides bound to major histocompatibility complex (MHC) I and MHC II molecules in central nervous system (CNS) of eight patients with multiple sclerosis (MS). MHC molecules were purified from autopsy CNS material by immunoaffinity chromatography with monoclonal antibody directed against HLA-A, -B, -C, and -DR. Subsequently peptides were separated by reversedphase HPLC and analyzed by mass spectrometry. Database searches revealed 118 amino acid sequences from self-proteins eluted from MHC I molecules and 191 from MHC II molecules, corresponding to 174 identified source proteins. These sequences define previously known and potentially novel autoantigens in MS possibly involved in disease induction and antigen spreading. Taken together, we have initiated the characterization of the CNS-expressed MHC ligandome in CNS diseases and were able to demonstrate the presentation of naturally processed myelin basic protein peptides in the brain of MS patients.

Diverse HLA-I Peptide Repertoires of the APC Lines MUTZ3-Derived Immature and Mature Dendritic Cells and THP1-Derived Macrophages

“…First, the source proteins were derived from almost all subcellular locations, with the nucleus, cytoplasm, plasma membrane, and endoplasmic reticulum the most dominant (Fig. 5), which is similar for the HLA-I peptidome of melanoma tumor samples reported earlier (37,38), but different for other human samples such as the B lymphoblastoid cell line, where no source proteins from plasma membrane were found (39), and multiple sclerosis autopsy samples, where cytoplasm and plasma membrane were the most dominant, 34 and 24%, respectively (40). Second, the source proteins were involved in various molecular functions but especially in cell communication/signal transduction, protein metabolism, and transcription factor activity/regulator activity, and the proportion of source proteins per molecular function was similar.…”

“…The heterogeneity and individualization was slightly higher for the HLA-I-bound peptides than for the source proteins, as the number of shared source proteins was slightly higher compared with those of the HLA-I peptides. This has been observed also in other human cell lines and tumor samples such as melanoma (37,38,40) and depicts differences in the Ag processing and presentation in the two MUTZ3 DC differentiation states and THPMF.…”

“…The dominance of nanopeptides was also observed in the shared peptides between MUTZ3 iDC and MUTZ3 mDC, and in the HLA-A*02:01-bound peptides shared among the MUTZ3 DCs and THP1MF. This dominance of nanopeptides has also been observed in other cell lines and patient tumor samples (37)(38)(39)(40), and indicates that nine amino acids is the optimum length for MHC I-binding peptides. Decapeptides were the second most dominant and constituted 22 and 25% for MUTZ3 iDC and MUTZ3 mDC and 12% for THP1.…”

“…Second, the source proteins were involved in various molecular functions but especially in cell communication/signal transduction, protein metabolism, and transcription factor activity/regulator activity, and the proportion of source proteins per molecular function was similar. In contrast, in the B lymphoblastic cell line 721.221, the source proteins were dominantly involved in declining prominence in metabolism, cell growth and/or maintenance, cell communication, and stress response (39), and in multiple sclerosis autopsy samples, they were dominantly involved in cellular assembly and organization, nervous system development and function, cellular growth, and proliferation (40). The similarities in source protein peptide sampling in MUTZ3 DCs and THP1MF, although unconfirmed, would imply similarities in protein turnover, because protein turnover correlates with source protein peptide sampling (43,44).…”

Experimental Autoimmune Encephalomyelitis

“…The selection of the specific model might differ strongly between an immunologist who wants to assess basic principles of organ specific autoimmunity in contrast to the MS researcher who wants to analyze specific disease aspects or a new therapeutic approach in preclinical pharmacology studies. (Fissolo et al, 2009). On the ground of a genetic predisposition with the possible cofactors vitamin D and sunlight exposure the disease is induced and autoimmunity is maintained by aberrant immune cascades that will finally lead to myelin/oligodendrocyte pathology as well as axonal and neuronal loss.…”