The RGS protein Crg2 is required for establishment and progression of murine pulmonary cryptococcosis

Cryptococcal regulators of G protein signaling (CRG) are important for growth, differentiation, and virulence of Cryptococcus neoformans. Disruption of CRG2 resulted in dysregulated cAMP signaling and attenuated virulence, whereas disruption of CRG1 increased pheromone responses and enhanced virulence in the archetypal H99 strain. In tests with newly constructed near congenic mutants, a distinction between crg2Δ and crg1Δ gene expression was not apparent during macrophage interaction. Intranasal inoculation indicated that crg2Δ, crg1Δ, and wild-type strains reached the lungs within 0.5 hours of infection. However, CFUs were significantly decreased for crg2Δ at 2, 7, and 14 days post-infection. In contrast, crg1Δ proliferated to the same extent as the wild type (WT). Lung edema was not apparent in mice infected with crg2Δ 0.5 hours post-infection, which showed little cellular infiltrate in comparison to WT. Alveolar septal thickening was most evident in mice infected with crg1Δ, while mice infected with WT exhibited decreased septal thickening at later time points. Consistent with these observations, crg2Δ was less efficient in the elicitation of Th2 immune responses in a multiplex cytokine assay. Our results suggest that Crg2 is critical for establishment of early pulmonary infection and for persistence of infection, Crg1 regulates virulence in a strain-specific manner, and crg2Δ, crg1Δ and WT can all be distinguished on the basis of host tissue responses.