Figure 6.

Amino acid transport-deficient Histoplasma yeasts are fully virulent in macrophages and in vivo.

(a-b) Cultured transgenic P388D1 LacZ-expressing macrophages were inoculated with either wild type (“WT,” black circles) or amino acid permease-deficient (“gap3 dip5 gai1,” red squares) Histoplasma yeasts. (a) At 24 and 48 hours post-infection, macrophages were lysed and intracellular yeast were quantified by enumerating colony forming units (CFU). (b) At 6, 7, and 8 days post-infection, macrophage viability was quantified using the remaining LacZ activity relative to uninfected controls to indicate Histoplasma lysis of macrophages. (c) Respiratory infections of C57BL/6 mice indicate in vivo virulence. Mice were infected intranasally with wild type (“WT,” black circles) or amino acid permease-deficient (“gap3 dip5 gai1,” red squares) Histoplasma yeasts. After 8 days post-infection, the fungal burdens in mouse lungs and spleens were quantified by plating of tissue homogenates. Data is plotted relative to the inoculum. In (a), points represent biological replicates. In (b), error bars represent standard deviation among 3 biological replicates. In (c), points represent CFU counts from individual mice. Asterisks denote statistically significant differences in growth as determined via Student’s t test (*, p < 0.05; n.s., not significant).