Host-parasite relationships in the yeastlike form of Paracoccidioides brasiliensis strain IVIC Pb9.

The yeastlike form of Paracoccidioides brasiliensis strain IVIC Pb9 reduced the amount of alpha-1,3-glucan in its cell wall from 45 to 3% when subcultured in vitro for several years. This strain regained its alpha-1,3-glucan up to 25% of the total cell wall when grown in vivo. A mutant strain of P. brasiliensis Pb9, named IVIC Pb140, reported to have 1,3-mannan instead of alpha-glucan in the cell wall, could not be recovered from experimentally infected animals. The existence of some relationship between the presence of alpha-1,3-glucan in the cell wall of the yeastlike form and the pathogenicity of this fungus is suggested in this report.