AbstractTo understand the impact of a hypovirus infection on the secretome of the chestnut blight fungus, Cryphonectria parasitica, a phytopathogenic filamentous fungus, two-dimensional electrophoresis (2-DE) and isobaric tag for relative and absolute quantitation (iTRAQ) technology were employed to identify and quantify the secreted proteins. A total of 403 unique proteins were identified from the secretome of the wild type virus-free strain EP155. Of these proteins, 329 were predicted to be involved in known secretory pathways and they are primarily composed of metabolic enzymes, biological regulators, responders to stimulus and components involved in plant-pathogen interactions. When infected with the hypovirus CHV1-EP713, 99 proteins were found to be differentially expressed as compared to the wild type strain EP155. These proteins were mainly related to plant cell wall degradation, response to host defense, fungal virulence and intracellular structure. The effects of CHV1 on secreted proteins may reveal a relationship between physiological pathways and hypovirulence.