A deep cut into early cryptococcal pathogenesis.

Dissemination from one organ system to another is common to many pathogens and often the key process separating simple illness from fatal infection. The pathogenic species offer a prime example. Cryptococcal infection is thought to begin in the lungs, as a mild or asymptomatic pneumonia. However, bloodborne dissemination from the lungs to the brain is responsible for the most devastating forms of infection. As with other disseminating infections, the transition likely depends on rare but crucial events, such as the crossing of a tissue barrier. By their nature, these events are difficult to study. Francis et al. (mBio 15:e03078-23, 2024, https://doi.org/10.1128/mbio.03078-23) have addressed this difficulty by developing a powerful imaging pipeline to scan through unprecedented volumes of tissue from mice infected with at multiple stages of infection. Their observations challenge some of our basic assumptions about cryptococcal pathogenesis, including when and how the organism reaches the bloodstream and the central nervous system.