Invasive fungal infections (IFIs) typically occur in a context of severe immunosuppression (prolonged neutropenia after chemotherapy, transplantation), prolonged corticotherapy, breaches in anatomical barriers (catheters, ...). Candida genus, responsible of 70-90% of all IFIs is associated with significant mortality. Currently, treatment of these infections is characterized by the toxicity of some reference molecules and the existence of phenomena of molecular and clinical resistance explaining the need to propose urgently new therapeutic alternatives. The developed projects try to bring, by complementary approaches, elements of response in terms of bypassing resistance, host-parasite interaction, therapeutic targets and new chemical families.

Circumventing resistance to azoles

Elucidation of mechanisms of resistance

From a data bank of clinical isolates of C. albicans, mechanisms of resistance to azoles have been characterized (overexpression of efflux pumps mRNA and Erg11p, mutations in pumps transcription factors and in ERG11). 

Among the new mutations described in ERG11 (P82), the formal involvement of N136Y and Y447H substitutions in resistance was carried out by site-directed mutagenesis using a novel Pichia Pastoris model and confirmed in a model of invasive candidiasis (P94) model. These substitutions must be taken into account in optimizing the 3D model of CaCYP51, essential tools in the rational design of novel 14 alpha-demethylase inhibitors. Other mechanisms of resistance were highlighted such as mutations and deletions on ERG3 (P104). Aspergillus fumigatus resistance to azoles has also been described and the involvement of TR/L98H was confirmed (P103).

Synthesis and biological evaluation of new azole derivatives

Multifunctional azoles, both inhibitors of efflux pumps and insensitive to major ERG11p substitutions, were synthesized to extend our first molecules in order to overcome the mutations near the heme. Two derivatives display significant activity against C. albicans resistant to fluconazole and a broad-spectrum activity against Candida (C. krusei, C. parapsilosis, C. glabrata) (P87, P91, P96).

New experimental models

Granulomatous hepatic candidiasis is a location described during infection of immunocompromised patients. In addition, the more rare brain aspergillosis, but more often granulomatous, display a more reserved prognosis: 60 to 100% mortality. In these two clinical entities antifungal resistance is strongly suggested. To date, no granuloma model generated in vitro allows to explore the phenotypic and the genotypic modifications of the fungal cell population within the granuloma and to identify the molecular factors of resistance. EA 1155 proposed the first model of fungal granuloma (P105) for an exploration of these factors.


Kinases: targets for anti-infective agents

Over many years, the Laboratory has developed imidazolylalkylindole-based antileishmanial agents (P20, P39, P77). The compounds are likely to interfere with the synthesis of ergosterol, an essential constituent of the parasite plasma membrane (P52).

Meanwhile, the laboratory has demonstrated that imidazolidin-2-ones showed antileishmanial activity by inhibiting parasitic PKC activity and process of host cell invasion by the parasite (P16), confirming the relevance of protein kinases as therapeutic targets for the design of new antileishmanial compounds (P80).

More recently, 2,3-diarylimidazo[1,2-a]pyridines (P99) provided promising antileishmanial activity on promastigote and intracellular amastigote stages of parasite, associated with low cytotoxicity (P108). The involvement of LmCK1 and other parasitic kinases is under study to explain the antileishmanial effect of the most active compounds.

Data banks of clinical strains

In close collaboration with the hospital laboratory of Parasitology, Medical Mycology and Parasitic Immunology (CHU Nantes) and many national and international teams, EA 1155 maintains a bank of clinical isolates regularly incremented by new isolates (P83, P89, P93, P95, P101, P102).