Region of Difference 2 Contributes to Virulence of<i>Mycobacterium tuberculosis</i>
Bibliographic record
Abstract
Mycobacterium bovis BCG strains are live, attenuated vaccines generated through decades of in vitro passage. Because in vitro growth does not select for interaction with the host, it has been hypothesized that genetic loci lost from BCG code for virulence determinants that are dispensable for growth in the laboratory, as exemplified by Region of Difference 1 (RD1), which was lost during the original derivation of BCG between 1908 and 1921. Region of Difference 2 (RD2) was lost during the ongoing propagation of BCG between 1927 and 1931, a time that coincides with reports of the ongoing attenuation of the vaccine. In this study, RD2 has been disrupted in M. tuberculosis H37Rv to test whether its loss contributed to the further attenuation of BCG. The deletion of RD2 did not affect in vitro growth; in contrast, the mutant manifested a decrease in pulmonary and splenic bacterial burdens and reduced pathology in C57BL/6 mice at early time points. This attenuated phenotype was complemented by reintroducing the genes Rv1979c to Rv1982 (including mpt64) but not Rv1985c to Rv1986. In RAW 264.7 macrophages, H37Rv:ΔRD2 showed a decreased proliferation and impaired modulation of the host innate immune response; both observations were complemented with Rv1979c to Rv1982. To test the effect of RD2 disruption on innate immunity, Rag(-/-) mice were infected; H37Rv:ΔRD2 had increased survival times compared those of H37Rv. These findings support the notion that the safety profile of certain BCG vaccines stems from multiple attenuating mutations, with the RD2 deletion resulting in a less-virulent organism through the impaired bacterial manipulation of the host innate immune response.
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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 | 0.000 | 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".