Aspergillus fumigatusIn-Host HOG pathway mutation for Cystic Fibrosis Lung Microenvironment Persistence

Abstract

AbstractThe prevalence ofAspergillus fumigatuscolonization in individuals with Cystic Fibrosis (CF) and subsequent fungal persistence in the lung is increasingly recognized. However, there is no consensus for clinical management ofA. fumigatusin CF individuals, due largely to uncertainty surroundingA. fumigatusCF pathogenesis and virulence mechanisms. To address this gap in knowledge, a longitudinal series ofA. fumigatusisolates from an individual with CF were collected over 4.5 years. Isolate genotypes were defined with whole genome sequencing that revealed both transitory and persistentA. fumigatusin the lung. Persistent lineage isolates grew most readily in a low oxygen culture environment and conidia were more sensitive to oxidative stress inducing conditions compared to non-persistent isolates. Closely related persistent isolates harbor a unique allele of the high osmolarity glycerol (HOG) pathway mitogen activated protein kinase kinase, Pbs2 (pbs2C2). Data suggest this novelpbs2C2allele arosein vivoand is necessary for the fungal response to osmotic stress in a low oxygen environment through hyperactivation of the HOG (SakA) signaling pathway. Hyperactivation of the HOG pathway throughpbs2C2comes at the cost of decreased conidia stress resistance in the presence of atmospheric oxygen levels. These novel findings shed light on pathoadaptive mechanisms ofA. fumigatusin CF, lay the foundation for identifying persistentA. fumigatusisolates that may require antifungal therapy, and highlight considerations for successful culture of persistent fungal CF isolates.ImportanceAspergillus fumigatusinfection causes a spectrum of clinical manifestations. For individuals with Cystic Fibrosis (CF), Allergic Bronchopulmonary Aspergillosis (ABPA) is an established complication, but there is a growing appreciation forA. fumigatusairway persistence in CF disease progression. There currently is little consensus for clinical management ofA. fumigatuslong-term culture positivity in CF. A better understanding ofA. fumigatuspathogenesis mechanisms in CF is expected to yield insights into when antifungal therapies are warranted. Here, a 4.5-year longitudinal collection ofA. fumigatusisolates identified a persistent lineage that harbors a unique allele of the Pbs2 MAPKK necessary for unique CF-relevant stress phenotypes. Importantly forA. fumigatusCF patient diagnostics, this allele provides increased CF lung fitness at a cost of reducedin vitrogrowth in standard laboratory conditions. These data illustrate a molecular mechanism forA. fumigatusCF lung persistence with implications for diagnostics and antifungal therapy.