Comparison of the relative toxicities of Shiga-like toxins type I and type II for mice

Abstract

In earlier studies using a streptomycin-treated mouse model of infection caused by enterohemorrhagic Escherichia coli (EHEC), animals fed Shiga-like toxin type II (SLT-II)-producing strains developed acute renal cortical necrosis and died, while mice fed Shiga-like toxin type I (SLT-I)-producing clones did not die (E. A. Wadolkowski, L. M. Sung, J. A. Burris, J. E. Samuel, and A. D. O'Brien, Infect. Immun. 58:3959-3965, 1990). To examine the bases for the differences we noted between the two toxins in the murine infection model, we injected mice with purified toxins and carried out histopathological examinations. Despite the genetic and structural similarities between the two toxins, SLT-II had a 50% lethal dose (LD50) which was approximately 400 times lower than that of SLT-I when injected intravenously or intraperitoneally into mice. Histopathologic examination of toxin-injected mice revealed that detectable damage was limited to renal cortical tubule epithelial cells. Passive administration of anti-SLT-II antibodies protected mice from SLT-II-mediated kidney damage and death. Immunofluorescence staining of normal murine kidney sections incubated with purified SLT-I or SLT-II demonstrated that both toxins bound to cortical tubule and medullary duct epithelial cells. Compared with SLT-I, SLT-II was more heat and pH stable, suggesting that SLT-II is a relatively more stable macromolecule. Although both toxins bound to globotriaosylceramide, SLT-I bound with a higher affinity in a solid-phase binding assay. Differences in enzymatic activity between the two toxins were not detected. These data suggest that structural/functional differences between the two toxins, possibly involving holotoxin stability and/or receptor affinity, may contribute to the differential LD50s in mice.

Shiga toxin-2 results in renal tubular injury but not thrombotic microangiopathy in heterozygous factor H-deficient mice

“…Consistent with our observations, many studies in which mice have either been inoculated with Stx-producing E. coli strains [18,29,30] or injected with purified Stx with [20,21,[25][26][27]31] or without LPS [22][23][24]32,33] have not developed evidence of glomerular thrombosis. We have summarized these studies in Table 2, where we list the experimental insult (e.g.…”

“…We have summarized these studies in Table 2, where we list the experimental insult (e.g. Stx-producing bacterial infection, purified Stx) together with the reported renal phenotype [18,[20][21][22][23][24][25][26][27][29][30][31][32][33]. The lack of typical glomerular pathological changes of TMA in these studies is striking.…”

“…Furthermore, the toxic effects of Stx are enhanced by concomitant administration of lipopolysaccharide (LPS) [19]. Hence, purified Stx-2, sometimes in combination with LPS, has been used by several groups in an attempt to induce HUS in mice [20][21][22][23][24][25][26][27]. Therefore, to test our hypothesis, we chose to treat Cfh +/mice with purified Stx-2 in the presence of LPS.…”

Antibodies anti-Shiga toxin 2 B subunit from chicken egg yolk: Isolation, purification and neutralization efficacy

“…Wang et al (2010) also evaluated the neutralizing capability of anti-Stx IgY antibodies by in vitro and in vivo experiments, but they tested the protective efficacy against Stx1. In this work, we demonstrate that hens, and also rabbits, can produce neutralizing IgY antibodies against Stx2, which is associated to more severe course of illness (Karmali et al, 1985) and when administered systemically it is about 400 times more lethal to mice than Stx1 (Tesh et al, 1993). Also in our work, we completely neutralize the activity of Shiga toxin in vitro and in vivo with an IgY concentration of about 700 times lower than that used in Wang et al (2010).…”

“…STEC strains produce Stx1, Stx2 (or their variants), or both of these toxins. Although the mechanisms of action of Stxs are thought to be similar, cytotoxicity of Stx2 may be stronger than that of Stx1; the 50% lethal dose in mice of purified Stx2 is 1 ng, whereas Stx1 has a 50% lethal dose of 400 ng (Tesh et al, 1993). Additionally, epidemiological data indicate that Stx2 producing strains are more frequently associated to severe illnesses such as HUS than Stx1 producing strains (Karmali et al, 1985).…”