Clonally expanded B cells in multiple sclerosis bind EBV EBNA1 and GlialCAM, 2022, Lanz et al

Utsikt

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Clonally expanded B cells in multiple sclerosis bind EBV EBNA1 and GlialCAM

Lanz, Tobias V.; Brewer, R. Camille; Ho, Peggy P.; Moon, Jae-Seung; Jude, Kevin M.; Fernandez, Daniel; Fernandes, Ricardo A.; Gomez, Alejandro M.; Nadj, Gabriel-Stefan; Bartley, Christopher M.; Schubert, Ryan D.; Hawes, Isobel A.; Vazquez, Sara E.; Iyer, Manasi; Zuchero, J. Bradley; Teegen, Bianca; Dunn, Jeffrey E.; Lock, Christopher B.; Kipp, Lucas B.; Cotham, Victoria C.; Ueberheide, Beatrix M.; Aftab, Blake T.; Anderson, Mark S.; DeRisi, Joseph L.; Wilson, Michael R.; Bashford-Rogers, Rachael J. M.; Platten, Michael; Garcia, K. Christopher; Steinman, Lawrence; Robinson, William H.

Abstract
(Line breaks added)

Multiple sclerosis (MS) is a heterogenous autoimmune disease in which autoreactive lymphocytes attack the myelin sheath of the central nervous system. B lymphocytes in the cerebrospinal fluid (CSF) of patients with MS contribute to inflammation and secrete oligoclonal immunoglobulins1,2. Epstein–Barr virus (EBV) infection has been epidemiologically linked to MS, but its pathological role remains unclear3.

Here we demonstrate high-affinity molecular mimicry between the EBV transcription factor EBV nuclear antigen 1 (EBNA1) and the central nervous system protein glial cell adhesion molecule (GlialCAM) and provide structural and in vivo functional evidence for its relevance.

A cross-reactive CSF-derived antibody was initially identified by single-cell sequencing of the paired-chain B cell repertoire of MS blood and CSF, followed by protein microarray-based testing of recombinantly expressed CSF-derived antibodies against MS-associated viruses.

Sequence analysis, affinity measurements and the crystal structure of the EBNA1–peptide epitope in complex with the autoreactive Fab fragment enabled tracking of the development of the naive EBNA1-restricted antibody to a mature EBNA1–GlialCAM cross-reactive antibody. Molecular mimicry is facilitated by a post-translational modification of GlialCAM.

EBNA1 immunization exacerbates disease in a mouse model of MS, and anti-EBNA1 and anti-GlialCAM antibodies are prevalent in patients with MS.

Our results provide a mechanistic link for the association between MS and EBV and could guide the development of new MS therapies.

Web | DOI | PMC | PDF | Nature
 
Sequence analysis, affinity measurements and the crystal structure of the EBNA1–peptide epitope in complex with the autoreactive Fab fragment enabled tracking of the development of the naive EBNA1-restricted antibody to a mature EBNA1–GlialCAM cross-reactive antibody. Molecular mimicry is facilitated by a post-translational modification of GlialCAM.
The article is paywalled, but I’m interested in understanding the last parts:
the development of the naive EBNA1-restricted antibody to a mature EBNA1–GlialCAM cross-reactive antibody.
What does it mean that the antibody changed reactivity? How did this happen?

I’m interested because this could be a way of getting around the auto-reactivity checkpoints if the changes happen after those.
Molecular mimicry is facilitated by a post-translational modification of GlialCAM.
If I’ve understood it correctly, post-translational modifications (PTM) are changes to proteins after the synthesis (the initial creation of the protein). Such changes would alter the physical form of the protein and therefore make the protein look like something else.

If whatever the protein now resembles is something there are antibodies against, the protein will now be more affected by the antibodies than before the PTM.

I think this is what the autoimmunity through molecular mimicry hypothesis proposes, although I’m not sure the name is ideal. It’s more that the «self» changes to resemble the virus, not that the virus looks so much like the self that the two are mistaken.
 
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