The ABC transporter-encoding gene AFR1 affects the resistance of Cryptococcus neoformans to microglia-mediated antifungal activity by delaying phagosomal maturation

The pathogenic yeast Cryptococcus neoformans has evolved several strategies to survive within phagocytes. Recently, it has been demonstrated that upregulation of the ATP binding cassette transporter-encoding gene antifungal resistance 1 (AFR1) is important not only for determining the resistance of C. neoformans to fluconazole but also in influencing fungal virulence. In the present study, we showed that the fluconazole-resistant AFR1-overexpressing mutant strain was not sensitive to microglia-mediated anticryptococcal activity, as compared with the fluconazole-susceptible isogenic strains, the wild type and the afr1Δ mutant. Interestingly, although the three strains were phagocytosed to a similar extent, reduced acidification and delayed maturation were observed in phagosomes containing the AFR1-overexpressing strain with respect to the others. These findings provide the first evidence that upregulation of the AFR1 gene affects C. neoformans–microglia interplay, adding insights to the complexity of cryptococcal virulence and to its unexpected link with azole resistance.