Mouse Toxicity and Cytokine Release by Verotoxin 1 B Subunit Mutants
Bibliographic record
Abstract
The crystal structure of the verotoxin 1 (VT1) B subunit complexed with a globotriaosylceramide (Gb(3)) analogue showed the presence of three receptor binding sites per monomer. We wished to study the effects of altering the three sites, singly or in combination, on animal toxicity and cytokine induction in vitro. We found that while the site 1 and 2 mutants were modestly (two- to sevenfold) reduced in their ability to cause disease in BALB/c mice, the site 3 mutant, W34A, was as toxic as VT1. However, all the double-mutant proteins, irrespective of which two sites were mutated, exhibited approximately a 100-fold reduction in their 50% lethal doses for mice. These results suggest that multivalent receptor binding is important in vivo and that all three binding sites make a similar contribution to the latter process. The triple-mutant holotoxin, F30A G62T W34A, administered intraperitoneally without adjuvant, stimulated a strong antibody response in BALB/c mice, and the immune sera neutralized the activity of VT1 in vitro. Induction of tumor neurosis factor alpha release from differentiated human monocytes (THP-1 cells) was relatively impaired for site 1 and site 2 but not site 3 mutants, suggesting an auxiliary role for the latter site in mediation of cytokine release in vitro. Cytotoxicity assays on undifferentiated THP-1 cells have also demonstrated the importance of sites 1 and 2 and the relatively small role played by site 3 in causing cell death. These data suggest an association between the cytotoxicity of the protein and its ability to induce cytokine release.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".