Understanding the dissemination of Cryptococcus neoformans and Cryptococcus gattii - a longitudinal in vivo imaging study.

Cryptococcus neoformans and C. gattii are encapsulated yeasts that are opportunistic pathogens, affecting 1 million people/ year, predominantly by inhalation, leading to latent pneumonia. However, the most common and severe presentation is infection of the brain. The traversal of cryptococci across the blood-brain barrier (BBB) is a crucial step in its pathogenesis; but how and when this happens is still enigmatic. Experimental data suggests that the host immune cells (monocytes/macrophages) play a key role, providing a vehicle for BBB crossing and dissemination. Their well-studied genetics and virulence factors combined with the availability of reliable animal models have made cryptococcosis a model system for studying hostpathogen interactions. Studying in vivo infection models typically requires host sacrifice and enumeration of micro-organisms from individual organs to determine the extent and dissemination during infection. Such single time point studies are limited as they do not provide dynamic information on cell interactions. We have developed in vivo imaging methods that permit spatiotemporal monitoring of disease progression and different cell populations. The main objective of this project is to use these novel tools to dynamically monitor immune cells and cryptococci in vivo to resolve their interactions during infection. Hereby, we will focus on when and how cryptococci cross natural barriers and disseminate, which might contribute to identify treatment targets.