|BRIGOTTI, MAURIZIO - University Of Bologna, Italy|
|ARFILLI, VALENTINA - University Of Bologna, Italy|
|CARNICELLI, DOMENICA - University Of Bologna, Italy|
|RICCI, FRANCESCA - Bologna University Hospital Authority St Orsola-Malpighi Polyclinic|
|TAZZARI, PIER LUIGI - Bologna University Hospital Authority St Orsola-Malpighi Polyclinic|
|ARDISSINO, GIANLUIGI - Fondazione Irccs Ca’ Granda Ospedale Maggiore Policlinico|
|SCAVIA, GAIA - Istituto Superiore Di Sanita|
|MORABITO, STEFANO - Istituto Superiore Di Sanita|
Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2018
Publication Date: 9/18/2018
Citation: Brigotti, M., Arfilli, V., Carnicelli, D., Ricci, F., Tazzari, P., Ardissino, G., Scavia, G., Morabito, S., He, X. 2018. Soluble toll-like receptor 4 impairs the interaction of Shiga toxin 2a with human serum amyloid P component. Toxins. 10(9):379. https://doi.org/10.3390/toxins10090379.
Interpretive Summary: Shiga toxin (Stx) produced by Stx-producing E. coli (STEC) are powerful toxins that cause severe illnesses in children, including hemolytic uremic syndrome (HUS), a life-threatening complication. The binding of Stx2 by non-cellular blood components, human amyloid P component (HuSAP), significantly blocks Stx2 toxicity. In this study, we found that the soluble extracellular domain of Toll-like receptor 4 (TLR4) also binds Stx2 and forms complexes with Stx2 in blood, which allowed Stx2 to escape from capture by HuSAP and preserve its ability to damage human cells. Thus, soluble TLR4 could be considered as a positive regulator for Stx2 and it may play a critical role in HUS development during the natural course of STEC-infection.
Technical Abstract: Shiga toxin 2a (Stx2a) is the main virulence factor produced by Stx-producing E. coli (STEC) responsible for hemorrhagic colitis and the life-threatening sequela hemolytic uremic syndrome in children. The toxin released in the intestine by STEC targets the globotriaosylceramide receptor (Gb3Cer) present on the endothelial cells of the brain and the kidney after a transient blood phase during which Stx2a interacts with blood components, such as neutrophils, which, conversely, recognize Stx through Toll-like receptor 4 (TLR4). Among non-cellular blood constituents, human amyloid P component (HuSAP) is considered a negative modulating factor that specifically binds Stx2a and impairs its toxic action. Here we show that the soluble extracellular domain of TLR4 inhibits the binding of Stx2a to neutrophils, assessed by indirect flow cytometric analysis. Moreover, by using human sensitive Gb3Cer-expressing cells (Raji cells) we found that the complex, Stx2a/soluble TLR4, escaped from capture by HuSAP, allowing the toxin to target and damage human cells, as assayed by measuring translation inhibition, the typical Stx-induced functional impairment. Thus, soluble TLR4 stood out as a positive modulating factor for Stx2a. In the paper these findings have been discussed in the context of the pathogenesis of HUS.