Abstract
ABSTRACTEnterohemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC) are enteric bacterial pathogens of worldwide importance. Most EPEC and non-O157 EHEC strains express lymphostatin (also known as LifA), a chromosomally encoded 365-kDa protein. We previously demonstrated that lymphostatin is a putative glycosyltransferase that is important in intestinal colonization of cattle by EHEC serogroup O5, O111, and O26 strains. However, the nature and consequences of the interaction between lymphostatin and immune cells from the bovine host are ill defined. Using purified recombinant protein, we demonstrated that lymphostatin inhibits mitogen-activated proliferation of bovine T cells and, to a lesser extent, proliferation of cytokine-stimulated B cells, but not NK cells. It broadly affected the T cell compartment, inhibiting all cell subsets (CD4, CD8, WC-1, and γδ T cell receptor [γδ-TCR]) and cytokines examined (interleukin 2 [IL-2], IL-4, IL-10, IL-17A, and gamma interferon [IFN-γ]) and rendered T cells refractory to mitogen for a least 18 h after transient exposure. Lymphostatin was also able to inhibit proliferation of T cells stimulated by IL-2 and by antigen presentation using a Theileria-transformed cell line and autologous T cells from Theileria-infected cattle. We conclude that lymphostatin is likely to act early in T cell activation, as stimulation of T cells with concanavalin A, but not phorbol 12-myristate 13-acetate combined with ionomycin, was inhibited. Finally, a homologue of lymphostatin from E. coli O157:H7 (ToxB; L7095) was also found to possess comparable inhibitory activity against T cells, indicating a potentially conserved strategy for interference in adaptive responses by attaching and effacing E. coli.
Highlights
Enterohemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC) are enteric bacterial pathogens of worldwide importance
Given that all previous examination of the effect of lymphostatin has been in bulk PMBC preparations using predominantly T cell-affecting mitogens, we wished to determine whether the effect of lymphostatin is restricted to T cells or whether other lymphocytes might be affected
Incubation of B cells with lymphostatin, followed by stimulation by interleukin 4 (IL-4), an activator of B cell proliferation, showed that lymphostatin induced a reduction in the proliferative capacity of B cells compared to that of the control (Fig. 1B; black circles indicate treatment with lymphostatin, and black squares indicate treatment with a similar concentration of lymphostatin protein buffer)
Summary
Enterohemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC) are enteric bacterial pathogens of worldwide importance. Enteropathogenic E. coli (EPEC) shares many features with EHEC and is a major cause of acute diarrhea in infants in developing countries Both pathotypes colonize intestinal mucosa via the formation of attaching and effacing (AE) lesions in a manner that requires a type III protein secretion system (T3SS), as well as accessory virulence factors [1]. One such factor is lymphostatin ( known as LifA), a chromosomally encoded protein with a predicted molecular mass of 365 kDa that is expressed by most EPEC and non-O157 EHEC strains [2]. This suggests a potentially conserved strategy among AE E. coli to interfere with adaptive immune response and adds to the relatively small number of bacterial factors described to directly target adaptive immune function
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
