Invasion of endothelial cells and arthritogenic potential of endocarditis-associated Corynebacterium diphtheriae

Abstract

Although infection by Corynebacterium diphtheriae is a model of extracellular mucosal pathogenesis, different clones have been also associated with invasive infections such as sepsis, endocarditis, septic arthritis and osteomyelitis. The mechanisms that promote C. diphtheriae infection and haematogenic dissemination need further investigation. In this study we evaluated the association and invasion mechanisms with human umbilical vein endothelial cells (HUVECs) and experimental arthritis in mice of endocarditis-associated strains and control non-invasive strains. C. diphtheriae strains were able to adhere to and invade HUVECs at different levels. The endocarditis-associated strains displayed an aggregative adherence pattern and a higher number of internalized viable cells in HUVECs. Transmission electron microscopy (TEM) analysis revealed intracellular bacteria free in the cytoplasm and/or contained in a host-membrane-confined compartment as single micro-organisms. Data showed bacterial internalization dependent on microfilament and microtubule stability and involvement of protein phosphorylation in the HUVEC signalling pathway. A high number of affected joints and high arthritis index in addition to the histopathological features indicated a strain-dependent ability of C. diphtheriae to cause severe polyarthritis. A correlation between the arthritis index and increased systemic levels of IL-6 and TNF-a was observed for endocarditis-associated strains. In conclusion, higher incidence of potential mechanisms by which C. diphtheriae may access the bloodstream through the endothelial barrier and stimulate the production of pro-inflammatory cytokines such as IL-6 and TNF-a, in addition to the ability to affect the joints and induce arthritis through haematogenic spread are thought to be related to the pathogenesis of endocarditis-associated strains.

Evolution, epidemiology and diversity of Corynebacterium diphtheriae : New perspectives on an old foe

“…Non-toxigenic C. diphtheriae strains by definition do not contain the tox carrying β-corynephage, but do vary in their abilities to adhere to host cells, intracellular viability and their ability to stimulate cytokine production by the host immune system which may influence the severity of the disease due to infection (Bertuccini et al, 2004;Hirata et al, 2002;Peixoto et al, 2014;Puliti et al, 2006). These strains differ from each other in the presence and organisation of different pilus gene clusters, spaA, spaD and spaH (Sangal et al, 2015;Trost et al, 2012).…”

Adherence and invasive properties of Corynebacterium diphtheriae strains correlates with the predicted membrane-associated and secreted proteome

“…An infection by a non-toxigenic C. diphtheriae strain may vary from a localized respiratory tract infection to more invasive endocarditis, septic arthritis and osteomyelitis [ 8 – 12 ]. The severity of the disease is dependent on the ability of C. diphtheriae strains to adhere to host cells, intracellular viability and the induction of cytokine production by the host immune system [ 13 – 16 ].…”

Of mice and men: Interaction of Corynebacterium diphtheriae strains with murine and human phagocytes

“…Binding of C. diphtheriae by TLR2 (1) leads on the one hand to upregulation of the C-type lectin receptor Mincle (2) and on the other hand, to phagocytosis of the bacteria (3), resulting in phagosome-lysosome fusion, which is somehow delayed by C. diphtheriae (4). Furthermore, binding of C. diphtheriae to Mincle (5) triggers the production of pro-inflammatory cytokines (6), which was confirmed by reduced cytokine production in Clec4e −/cells (7). Additionally, in Myd88deficient cells the cytokine production as well as the uptake of the bacteria was completely blocked (8).…”

“…The production of IL-6 and G-CSF leads to receptor-mediated activation of the JAK2/STAT3 (Janus Kinase/signal transducer and activator transcription) pathway [26,27], which subsequently leads to the induction of cell survival signals by producing increased levels of the anti-apoptotic proteins Bcl-2 and Bcl-X L. In case of C. diphtheriae, the knowledge about molecular signaling upon infection of macrophages is scarce. A number of studies showed that C. diphtheriae, once considered as strict extracellular pathogen, is able to cause severe invasive diseases, such as osteomyelitis, septic arthritis and endocarditis [6][7][8], which enhances the compelling need to focus on the infection mechanism of C. diphtheriae. In the study presented here, seven nontoxigenic C. diphtheriae isolates as well as two toxinproducing strains were characterized with regard to their interaction with BMM and human THP-1 cells.…”

“…Nevertheless, C. diphtheriae does not mandatorily produce the diphtheria toxin; it has to be infected by a toxin carrying β-corynephage, integrating into the genome of the bacteria [4]. Interestingly, toxigenic but also non-toxigenic C. diphtheriae strains are increasingly associated with invasive infections, such as endocarditis, osteomyelitis, splenic abscesses, meningitis, and septic arthritis [5][6][7]. Recent characterization of a non-toxigenic C. diphtheriae strain isolated from a cancer patient with osteomyelitis indicates that C. diphtheriae can colonize not only epithelia but can also infect deeper parts of the body [8].…”