Title: Roles of Cryptococcus cell wall dynamics during infection and antifungal drug resistance
Funder: The Academy of Medical Sciences

Abstract: This project aims to understand how antifungal drugs affect the Cryptococcus neoformans cell wall composition during infection. Fungal meningitis caused by Cryptococcus neoformans is associated with extremely high mortality ranging from 40% to 70% all patients in high income and low income countries, respectively. New interventions are required to mitigate this unmet clinical need. In order to generate new drugs, we need to better understand the mechanisms used by C. neoformans to cause disease. The cell wall has been extensively studies in other fungal pathogens and is a target of antifungal drugs such Echinocandins. Yet, there is very little published information on the C. neoformans cell wall during infection. Using biochemical and structural analyses, I will determine the cell wall composition of C. neoformans strains grown under host mimicking conditions in the presence and absence of antifungal drugs. The strains will be exposed to individual drugs and to drug combinations mimicking clinically used anti-Cryptococcus therapies. Importantly, I will correlate my findings with analyses of cell wall of isolates taken directly from patients in Uganda before antifungal treatment and after 7 days of therapy to determine how antifungals affect the cell wall in vivo. In addition, I will examine how antifungal drugs in clinical use influence the expression of cell wall biosynthesis genes in drug sensitive and drug-resistant clinical isolates. These studies will reveal critical new insights into C. neoformans cell wall dynamics during antifungal therapy, and will likely identify cell wall components to target for future antifungal drug development.

Lay abstract: Meningitis caused by the fungal pathogen Cryptococcus neoformans kills many people with weakened immunity, such as those with cancer, organ transplant recipients and HIV/AIDS. In HIV/AIDS patients alone, this meningitis kills over 181,000 people each year even with antifungal treatment. Therefore, better drugs are urgently needed to treat Cryptococcus infection. To develop new drugs, we need a better understanding of the fungal pathogen causing the disease. Cryptococcus has a shield made of two layers; the capsule and the cell wall. This shield protects Cryptococcus from harsh environmental conditions and the immune system. Many studies have focused on the role of the capsule in Cryptococcus infections while the knowledge about the cell wall has lagged behind, despite it being a major target for the treatment of other fungal infections. In this project, I will determine how the cell wall changes in the presence of drugs used to treat patients suffering from Cryptococcus Meningitis. I will compare the cell wall composition of Cryptococcus cells grown in the laboratory with and without antifungal drugs, and Cryptococcus cells isolated directly from patients before treatment and 7 days into treatment. I will also identify how genes responsible for cell wall components are controlled in the presence of these antifungal drugs. The cell wall is absent in human cells, and hence is a great target for antifungal drug development. Thus, this project will provide crucial new information about the Cryptococcus cell wall that will be required for future drug development.

Research activity codes: 2.1 BIOLOGICAL AND ENDOGENOUS FACTORS;2.2 FACTORS RELATING TO PHYSICAL ENVIRONMENT
Health categories: INFECTION