Intracellular parasitism by Histoplasma capsulatum: fungal virulence and calcium dependence.
Histoplasma capsulatum is an effective intracellular parasite of macrophages and causes the most prevalent fungal respiratory disease in the United States. A "dimorphic" fungus, H. capsulatum exists as a saprophytic mold in soil and converts to the parasitic yeast form after inhalation. Only the yeasts secrete a calcium-binding protein (CBP) and can grow in calcium-limiting conditions. To probe the relation between calcium limitation and intracellular parasitism, we designed a strategy to disrupt CBP1 in H. capsulatum using a telomeric linear plasmid and a two-step genetic selection. The resultingcbp1 yeasts no longer grew when deprived of calcium, and they were also unable to destroy macrophages in vitro or proliferate in a mouse model of pulmonary infection.
Sebghati
T S
TS
Department of Molecular Microbiology, Campus Box 8230, Washington University School of Medicine, St. Louis, MO 63110, USA.
Engle
J T
JT
Goldman
W E
WE
D000483:Alleles; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival; D018390:Gene Targeting; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D006658:Histoplasma / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000472:pathogenicity*; D006660:Histoplasmosis / Q000382:microbiology*; D008172:Lung Diseases, Fungal / Q000382:microbiology; D008264:Macrophages / Q000382:microbiology*; D051379:Mice; D016296:Mutagenesis; D010641:Phenotype; D010957:Plasmids; D011995:Recombination, Genetic; D014170:Transformation, Genetic; D014774:Virulence
D002135:Calcium-Binding Proteins; C416373:Cbp1 protein, histoplasma; D002118:Calcium