Bioluminescence Imaging of <i>Toxoplasma gondii</i> Infection in Living Mice Reveals Dramatic Differences between Strains
Bibliographic record
Abstract
We examined the in vivo growth, dissemination, and reactivation of strains of the protozoan parasite Toxoplasma gondii using a bioluminescence-based imaging system. Two T. gondii strains, one with a highly virulent disease phenotype in mice (S23) and the other with a 1,000-fold-lower virulence phenotype (S22), were engineered to stably express the light-emitting protein luciferase. One clone of each wild-type strain was isolated, and the two clones (S23-luc7 and S22-luc2) were found to express similar levels of luciferase. Mice were infected intraperitoneally with S23-luc7 (50 or 5 parasites) or S22-luc2 (500, 50, or 5 parasites), and the progress of the infections was examined noninvasively following injection of the substrate for luciferase, d-luciferin. In mice infected with 50 S23-luc7 parasites, the parasites grew exponentially within the peritoneal cavity (as measured by light emitted from luciferase-expressing parasites) during days 1 to 10 p.i., and this proliferation continued until there was severe disease. In mice infected with 500 S22-luc2 parasites, the parasites proliferated in a fashion similar to the S23-luc7 proliferation during days 1 to 6, but this was followed by a precipitous drop in the signal to levels below the limit of detection. Using this technique, we were also able to observe the process of reactivation of T. gondii in chronically infected mice. After treatment with dexamethasone, we detected reactivation of toxoplasmosis in mice infected with S23-luc7 and S22-luc2. During reactivation, growth of S23-luc7 was initially detected primarily in the head and neck area, while in S22-luc2-infected mice the parasites were detected primarily in the abdomen. This method has great potential for identifying important differences in the dissemination and growth of different T. gondii strains, especially strains with dramatically different disease outcomes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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 source (direct Gemma or distilled Codex), 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".