Mechanisms of pathogenic fungal host adaptation: Morphogenesis in Cryptococcus neoformans

One of the main mechanisms by which fungi are able to cause disease in humans is their ability to evade the immune response and adapt to the environmental conditions found in the host. In this regard, one of the yeasts that has the greatest ability to adapt to the host is Cryptococcus neoformans. This fungus is found in the environment, and is acquired by inhalation, although the most typical picture is meningitis in immunocompromised patients, mainly HIV+. The main phenotypic characteristic is the presence of a polysaccharide capsule surrounding the cell, which is considered a virulence factor. In addition, C. neoformans is able to increase cell size significantly forming “titan” cells, which can reach a diameter of more than 70 microns. In the laboratory, we are interested in the role of these titan cells in the virulence of C. neoformans. Recently, we have described in vitro media in which C. neoformans forms pseudo-titan cells, which has allowed us to identify new factors and pathways involved in this process.

Mechanisms of action of antifungals

In parallel, we have a line whose main objective is to characterize the mechanisms of action of antifungals. Specifically, we have focused our work on the effect of Amphotericin B (AmB). For decades it has been thought that this antifungal causes cell death after binding to ergosterol and pore formation. Our results indicate that this antifungal also induces strong oxidative stress in the cell, which occurs before cell integrity is lost. Furthermore, we have shown that oxidative stress is necessary for the fungicidal action of AmB. These results open the door to design new strategies to improve its efficiency in patients.

New therapeutic strategies

Work with AmB has led to research aimed at improving antifungal therapies. In particular, we have used the strategy of “off-patent” drug repositioning to search for new activities. Using this approach, we have identified several drugs that increase the effectiveness of AmB against major pathogenic yeasts, such as the antibiotic erythromycin. This approach has allowed us to identify drugs with antifungal activity against emerging pathogens, such as Candida auris.