Neutrophil extracellular trap-formation following Blastomyces dermatitidis yeast stimulation

Abstract

Blastomycosis, a potentially fatal infection results from an infection developing from a thermo-dimorphic fungal pathogen Blastomyces dermatitidis. The pivotal points driving the pathogenesis associated with the varied clinical presentations are not understood. The invasive morphotype of Blastomyces dermatitidis, the yeast are large (up to 20μm diameter) making phagocytosis, an internal mechanism used by neutrophils difficult. Neutrophils, predominant immune response cells, also have an extracellular mechanism, Neutrophil Extracellular Trap (NET) formation. Blastomyces dermatitidis yeast express an essential virulence factor, Blastomyces ADhesin factor (BAD1). Neutrophils were stimulated with a wild type B. dermatitidis expressing the virulence factor BAD1+ or with knock out B. dermatitidis BAD- not expressing the virulence factor to determine if BAD1modulates NET-formation. Neutrophil elastase (NE) activity was measured to indirectly quantify NET-formation and a Colony Forming Unit (CFU) assay measured the percent surviving yeast allowing for assessment of the NET’s fungicidal/fungistatic ability. The level of NET-formation and the percent surviving yeast for each yeast strain were compared when neutrophils from different donors were stimulated. The ability of yeast to evade a powerful extracellular mechanism used by the host immune response would allow continued pathogenesis.