Prevention of autoimmune disease due to lymphocyte modulation by the B-subunit ofEscherichia coli heat-labile enterotoxin

Abstract

We demonstrate that the receptor binding moiety of Escherichia coli heat-labile enterotoxin (EtxB) can completely prevent autoimmune disease in a murine model of arthritis. Injection of male DBA͞1 mice at the base of the tail with type II collagen in the presence of complete Freund's adjuvant normally leads to arthritis, as evidenced by inf lammatory infiltration and swelling of the joints. A separate injection of EtxB at the same time as collagen challenge prevented leukocyte infiltration, synovial hyperplasia, and degeneration of the articular cartilage and reduced clinical symptoms of disease by 82%. The principle biological property of EtxB is its ability to bind to the ubiquitous cell surface receptor GM1 ganglioside, and to other galactose-containing glycolipids and galactoproteins. The importance of receptor interaction in mediating protection from arthritis was demonstrated by the failure of a non-receptor-binding mutant of EtxB to elicit any protective effect. Analysis of T cell responses to collagen, in cultures of draining lymph node cells, revealed that protection was associated with a marked increase in interleukin 4 production concomitant with a reduction in interferon ␥ levels. Furthermore, in protected mice there was a significant reduction in anti-collagen antibody levels as well as an increase in the IgG1͞IgG2a ratio. These observations show that protection is associated with a shift in the Th1͞Th2 balance as well as a general reduction in the extent of the anti-type II collagen immune response. This suggests that EtxB-receptor-mediated modulation of lymphocyte responses provides a means of preventing autoimmune disease.Autoimmune diseases remain a major health problem despite enormous efforts to understand the underlying causative mechanisms. The lack of clarity with regard to both the predisposing factors and the precise antigenic targets of the immune response have restricted the development of effective therapeutic approaches. However, recent evidence suggests that agents which modulate the nature of the immune response may be effective as a means of prophylaxis or treatment. We recently reported that the nontoxic B subunit of Escherichia coli heat-labile enterotoxin (EtxB) exerts profound modulatory effects on lymphocyte populations in vitro; notably it was shown to cause the polyclonal activation of B cells, to induce apoptosis in CD8 ϩ T cells, and to have a negligible direct effect on CD4 ϩ

Modulation of Innate and Acquired Immune Responses by Escherichia coli Heat-Labile Toxin: Distinct Pro- and Anti-Inflammatory Effects of the Nontoxic AB Complex and the Enzyme Activity

“…However, our data reveal that the enzyme activity can exhibit an immunomodulatory effect distinct from adjuvanticity. It has previously been reported that purified or recombinant B subunits of LT or CT are capable of inducing oral tolerance and suppressing inflammatory Th1 responses that mediate autoimmune diseases (2,18,29). This is compatible with reports that the B subunit may selectively stimulate the reciprocally regulated Th2 population.…”

“…Although it has been suggested that both CT and LT inhibit IL-12 production (11), it has also been reported that CT does not affect IL-12 production in LPS and IFN-␥-activated murine macrophages (17). Furthermore, it has been shown that LT-B could inhibit the development of Th1 responses and the development of disease in a murine model of collagen-induced arthritis (18). However, a nontoxic mutant of LT was found to enhance Th1 responses to coadministered Ags (9).…”

Cross-Linking of GM1 Ganglioside by Galectin-1 Mediates Regulatory T Cell Activity Involving TRPC5 Channel Activation: Possible Role in Suppressing Experimental Autoimmune Encephalomyelitis

“…Hence, our finding of parallel effects of Gal-1 and CtxB in suppressing Teff proliferation as well as EAE point to GM1 as the primary target of Gal-1 expressed by Treg cells. The B subunit of Escherichia coli heat-labile enterotoxin shows considerable structural and functional similarity to CtxB and these two GM1 cross-linking agents have been shown to suppress a variety of autoimmune disorders (37)(38)(39). Homodimeric Gal-1, also an effective GM1 cross-linker, similarly suppresses several animal models of autoimmunity (see below).…”

Escherichia coli heat‐labile enterotoxin B subunit prevents autoimmune arthritis through induction of regulatory CD4+ T cells

“…We previously reported that subcutaneous injection of EtxB in IFA can prevent CIA (21). Although injectable therapies may be appropriate for the treatment of RA, it would be advantageous if a noninvasive method of delivery could be used.…”

“…Data are presented as the mean Ϯ SEM clinical score for each group of mice. Histologic sections of stifle joints were examined for pathology using an established 4-point scoring system (21). All scoring of disease was performed under blinded conditions.…”