Arianna Creech
Research Mentor(s): Michal Olszewski
Research Mentor School/College/Department: School of Medicine, Department of Internal Medicine, Division of Pulmonary and Critical Care
Presentation Date: 08/03/2022
Presentation Type: Oral presentation
Poster Number:
Session: Session I: 12:30 – 1:20pm
Room: Vandenberg
Authors: Arianna Creech, Kristie Goughenour, PhD, Jintao Xu, PhD, Michal Olszewski, DVM, PhD.
Abstract
Cryptococcus neoformans is an opportunistic fungi found naturally in the environment and can cause lung infection complicated with meningoencephalitis in immunocompromised individuals. Symptoms are often nonspecific and may include headache, fever, and nausea, leading to a delayed diagnosis and high mortality reaching 200,000 deaths yearly worldwide. Current anti-fungal medications are limited to a few classes of drugs and often have significant toxicity for the patients as the medication attacks both fungal and mammalian cells due to their fundamental similarity (eukaryotic). Thus, there is a significant need to direct attention to novel drug targets found in fungi and not mammals.
Trehalose sugar is found in fungi, bacteria, plants, and invertebrates, but not in mammals, which makes it an excellent potential therapeutic target. Trehalose helps C. neoformans during stress responses, including thermotolerance and resistance to oxidation and dehydration, hence it is required for virulence. In Cryptococcus neoformans, there is a biosynthetic pathway that converts glucose-6-phosphate into the sugar trehalose is initiated by an enzyme TPS1. To determine how absence of trehalose biosynthesis would allow the host to better clear the fungus a murine model of pulmonary cryptococcosis is used. Three groups of mice were infected via inhalation of 107 cells of C. neoformans: 1) a clinical isolate wildtype strain (H99), or 2) TPS1-deleted strain (tps1Δ), lacking trehalose production, and 3) the complemented strain, with TPS1 gene restored back to tps1Δ.
Relative to TPS1-producing strains which grew in the lungs, tps1Δ- infected mice showed rapid fungal clearance pattern. At day one post infection, 99% clearance was observed. This rapid fungal suppression could not be explained by the inflammatory cell response since they have not been recruited to the lungs until day 2. We hypothesized that tps1Δ strain could become sensitive to alveolar surfactant proteins known to express some antimicrobial function, i.e. surfactant protein A (SPA) and surfactant protein D (SPD). We co-cultured SPA and or SPD with both the wildtype and tps1Δ Cryptococcus in vitro to measure if these proteins have an immediate fungicidal effects on tps1Δ. After incubation at one and four hour timepoints, we found that SPA caused a significantly higher percent inhibition of tps1Δ than the wildtype H99. A similar effect was demonstrated for SPD at four hours of incubation.
Thus in the absence of TPS1, SPA and SPD are better at inhibiting fungal growth, suggesting that trehalose protects Cryptococcus from the effects of SPA and SPD, preventing the rapid pulmonary elimination of fungus by these naturally-present surfactant proteins. Further directions include understanding this temporally and in vivo. The mechanism behind the fungal persistence afforded by trehalose biosynthesis, will enable rational design of antifungal drugs targeting this pathway.
