Antigenic mimicry of ubiquitin by the gut bacterium Bacteroides fragilis: a potential link with autoimmune disease, 2018, Patrick et al

Andy · Oct 30, 2018

Summary
Ubiquitin is highly conserved across eukaryotes and is essential for normal eukaryotic cell function. The bacterium Bacteroides fragilis is a member of the normal human gut microbiota, and the only bacterium known to encode a homologue of eukaryotic ubiquitin. The B. fragilis gene sequence indicates a past horizontal gene transfer event from a eukaryotic source. It encodes a protein (BfUbb) with 63% identity to human ubiquitin which is exported from the bacterial cell.

The aim of this study was (i) to determine if there was antigenic cross‐reactivity between B. fragilis ubiquitin and human ubiquitin and (ii) to determine if humans produced antibodies to BfUbb. Molecular model comparisons of BfUbb and human ubiquitin predicted a high level (99·8% confidence) of structural similarity. Linear epitope mapping identified epitopes in BfUbb and human ubiquitin that cross‐react. BfUbb also has epitope(s) that do not cross‐react with human ubiquitin. The reaction of human serum (n = 474) to BfUbb and human ubiquitin from the following four groups of subjects was compared by enzyme‐linked immunosorbent assay (ELISA): (1) newly autoantibody‐positive patients, (2) allergen‐specific immunoglobulin (Ig)E‐negative patients, (3) ulcerative colitis patients and (4) healthy volunteers.

We show that the immune system of some individuals has been exposed to BfUbb which has resulted in the generation of IgG antibodies. Serum from patients referred for first‐time testing to an immunology laboratory for autoimmune disease are more likely to have a high level of antibodies to BfUbb than healthy volunteers. Molecular mimicry of human ubiquitin by BfUbb could be a trigger for autoimmune disease.
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Open access at https://onlinelibrary.wiley.com/doi/full/10.1111/cei.13195

Article based on this paper

Researchers Discover New Link Between Autoimmune Diseases and a Gut Bacterium

Queen’s University researchers have, for the first time, found a specific microbe in the gut that pumps out protein molecules that mimic a human protein, causing the human defense system to turn on its own cells by mistake.

The culprit in this case is called Bacteroides fragilis, a bacterium that normally lives in the human gut. The Queen’s team has shown that this bacterium produces a human-like protein that could trigger autoimmune diseases, such as rheumatoid arthritis. This human protein is called ‘ubiquitin’ and is needed for all the normal cell processes in our bodies.
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https://www.infectioncontroltoday.c...between-autoimmune-diseases-and-gut-bacterium

Barry · Oct 31, 2018

Thread merged

Being an autoimmune issue, might also have ME/CFS implications.

ETA: Removed link as already in original post.

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Antigenic mimicry of ubiquitin by the gut bacterium Bacteroides fragilis: a potential link with autoimmune disease, 2018, Patrick et al

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Antigenic mimicry of ubiquitin by the gut bacterium Bacteroides fragilis: a potential link with autoimmune disease, 2018, Patrick et al

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