Antimalarials and amphotericin B interact synergistically and are new options to treat cryptococcosis.

Cryptococcus gattii and Cryptococcus neoformans are the main etiological agents of cryptococcosis, an invasive mycosis treated with amphotericin B, 5-fluorocytosine, and fluconazole. This limited arsenal is toxic and is associated with antifungal resistance. Cryptococcosis and malaria pathogens are eukaryotic organisms that have a high incidence in Sub-Saharan Africa. The antimalarials (ATMs) halofantrine (HAL) and amodiaquine (AQ) block Plasmodium heme polymerase, and artesunate (ART) induces oxidative stress. Considering that Cryptococcus spp. is susceptible to reactive oxygen species and that iron is essential for metabolism, the repurposing of ATMs for treating cryptococcosis was tested. ATMs reduced fungal growth, induced oxidative and nitrosative stresses, and altered ergosterol content, melanin production, and polysaccharide capsule size in C. neoformans and C. gattii, revealing a dynamic effect on fungal physiology. A comprehensive chemical-genetic analysis using two mutant libraries demonstrated that the deletion of genes involved in synthesizing components of the plasma membrane and cell wall, and oxidative stress responses are essential for fungal susceptibility to ATMs. Interestingly, the amphotericin B (AMB) fungicidal concentrations were ∼10 times lower when combined with ATMs, demonstrating a synergistic interaction. Further, the combinations showed reduced toxicity to murine macrophages. Finally, HAL+AMB and AQ+AMB efficiently reduced lethality and fungal burden in the lungs and brain in murine cryptococcosis. These findings provide perspectives for further studies with ATMs against cryptococcosis and other fungal infections.

The Dynamics of Cryptococcus neoformans Cell and Transcriptional Remodeling during Infection.

The phenotypic plasticity of Cryptococcus neoformans is widely studied and demonstrated in vitro, but its influence on pathogenicity remains unclear. In this study, we investigated the dynamics of cryptococcal cell and transcriptional remodeling during pulmonary infection in a murine model. We showed that in Cryptococcus neoformans, cell size reduction (cell body ≤ 3 µm) is important for initial adaptation during infection. This change was associated with reproductive fitness and tissue invasion. Subsequently, the fungus develops mechanisms aimed at resistance to the host's immune response, which is determinant for virulence. We investigated the transcriptional changes involved in this cellular remodeling and found an upregulation of transcripts related to ribosome biogenesis at the beginning (6 h) of infection and a later (10 days) upregulation of transcripts involved in the inositol pathway, energy production, and the proteasome. Consistent with a role for the proteasome, we found that its inhibition delayed cell remodeling during infection with the H99 strain. Altogether, these results further our understanding of the infection biology of C. neoformans and provide perspectives to support therapeutic and diagnostic targets for cryptococcosis.

Exposure to itraconazole influences the susceptibility to antifungals, physiology, and virulence of Trichophyton interdigitale.

Dermatophytosis is the most common human skin infection worldwide caused by dermatophytes, such as Trichophyton interdigitale and Trichophyton rubrum. Itraconazole (ITZ) is one of the main antifungals used to treat these infections. However, especially for onychomycosis, the treatment requires long-term regimens, increasing the possibility of drug resistance. We evaluated the effects of ITZ in the physiology, virulence, and interaction of T. interdigitale with phagocytes and mice cutaneous infection. In a screening test, fungal growth in the presence of ITZ led to the spontaneous selection of less susceptible T. interdigitale and T. rubrum strains. Interestingly, this phenotype was permanent for some T. interdigitale strains. Then, we studied three T. interdigitale strains: one susceptible and two ITZ-adapted. The ITZ-adapted strains were also less susceptible to the cell wall and membrane stressors, suggesting a multidrug resistance (MDR) phenotype associated with the increased ERG11 and MDR3 expression. These strains also presented substantial alterations in ergosterol content, lipid peroxidation, biofilm, and extracellular matrix production. During interaction with macrophages, ITZ-adapted strains were less engulfed but increased the intracellular oxidative and nitrosative bursts. In addition, ITZ-adapted strains presented a reduced ability to grow in a murine model of dermatophytosis, although causing the same tissue damage as the parental strain. In conclusion, the T. interdigitale ITZ adaptation increases tolerance to antifungals and alters the interaction with macrophages and a mammalian host. We hypothesized that successive exposure to ITZ may influence the emergence of adapted strains and lead to the recalcitrance of dermatophytosis.

17-ß-Estradiol increases macrophage activity through activation of the G-protein-coupled estrogen receptor and improves the response of female mice to Cryptococcus gattii.

Cryptococcus gattii (Cg) is one of the agents of cryptococcosis, a severe systemic mycosis with a higher prevalence in men than women, but the influence of the female sex hormone, 17-ß-estradiol (E2), on cryptococcosis remains unclear. Our study shows that female mice presented delayed mortality, increased neutrophil recruitment in bronchoalveolar lavage fluid, and reduced fungal load after 24 hr of infection compared to male and ovariectomised female mice (OVX). E2 replacement restored OVX female survival. Female macrophages have more efficient fungicidal activity, which was increased by E2 and reversed by the antagonist of G-protein-coupled oestrogen receptor (GPER), which negatively modulates PI3K activation. Furthermore, E2 induces a reduction in Cg cell diameter, cell charge, and antioxidant peroxidase activity. In conclusion, female mice present improved control of Cg infection, and GPER is important for E2 modulation of the female response.