Merck

Histoplasma capsulatum depends on de novo vitamin biosynthesis for intraphagosomal proliferation.

Infection and immunity (2013-11-06)
Andrew L Garfoot, Olga Zemska, Chad A Rappleye
RESUMO

During infection of the mammalian host, Histoplasma capsulatum yeasts survive and reside within macrophages of the immune system. Whereas some intracellular pathogens escape into the host cytosol, Histoplasma yeasts remain within the macrophage phagosome. This intracellular Histoplasma-containing compartment imposes nutritional challenges for yeast growth and replication. We identified and annotated vitamin synthesis pathways encoded in the Histoplasma genome and confirmed by growth in minimal medium that Histoplasma yeasts can synthesize all essential vitamins with the exception of thiamine. Riboflavin, pantothenate, and biotin auxotrophs of Histoplasma were generated to probe whether these vitamins are available to intracellular yeasts. Disruption of the RIB2 gene (riboflavin biosynthesis) prevented growth and proliferation of yeasts in macrophages and severely attenuated Histoplasma virulence in a murine model of respiratory histoplasmosis. Rib2-deficient yeasts were not cleared from lung tissue but persisted, consistent with functional survival mechanisms but inability to replicate in vivo. In addition, depletion of Pan6 (pantothenate biosynthesis) but not Bio2 function (biotin synthesis) also impaired Histoplasma virulence. These results indicate that the Histoplasma-containing phagosome is limiting for riboflavin and pantothenate and that Histoplasma virulence requires de novo synthesis of these cofactor precursors. Since mammalian hosts do not rely on vitamin synthesis but instead acquire essential vitamins through diet, vitamin synthesis pathways represent druggable targets for therapeutics.

MATERIAIS
Número do produto
Marca
Descrição do produto

Sigma-Aldrich
Biotin, meets USP testing specifications
Sigma-Aldrich
Biotin, powder, BioReagent, suitable for cell culture, suitable for insect cell culture, suitable for plant cell culture, ≥99%
Sigma-Aldrich
Biotin, ≥99.0% (T)
Sigma-Aldrich
Biotin, tested according to Ph. Eur.
Supelco
Riboflavin (B2), analytical standard
Biotin, European Pharmacopoeia (EP) Reference Standard
Supelco
Biotin, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
Biotin, certified reference material, TraceCERT®
Sigma-Aldrich
(−)-Riboflavin, from Eremothecium ashbyii, ≥98%
Sigma-Aldrich
(−)-Riboflavin, BioReagent, suitable for cell culture, suitable for insect cell culture, ≥98%
Sigma-Aldrich
(−)-Riboflavin, meets USP testing specifications
Supelco
Riboflavin, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
Monoclonal ANTI-FLAG® M2 antibody produced in mouse, 1 mg/mL, clone M2, affinity isolated antibody, buffered aqueous solution (50% glycerol, 10 mM sodium phosphate, and 150 mM NaCl, pH 7.4)