Mold was nominated to the NTP for toxicological characterization and based on their inhalation, mycological, and immunological expertise, NIOSH was engaged as a partner to conduct multiple sub-chronic (13-week) exposure studies to individual organisms or mixtures of molds mimicking a real-world exposure. NIOSH has developed a system that allows for precisely controlled exposures to particulates via inhalation. This approach overcomes a number of limitations associated with previous mold exposure studies in experimental animal models that have used less relevant means of exposure to assess fungal toxicity. The acoustical generation system (AGS) developed as part of this partnership delivers fungal test articles to mice in a manner that simulates natural indoor fungal contaminant exposure. NIOSH continues to use the AGS and state-of-the-art methodologies to characterize toxicological endpoints following subchronic dry fungal spore and particle exposures. Following the completion of an NTP Study to evaluate the effects of exposure to Aspergillus fumigatus, NIOSH has begun studies to characterize pulmonary immune responses to Stachybotrys chartarum. In FY17, NIOSH drafted the report for the Aspergillus fumigatus studies, which will be submitted following internal NIOSH review. In FY17, NIOSH used the AGS to study pulmonary immune responses to both high and low mycotoxin producing chemotypes of S. chartarum. Preliminary datasets derived from 4 week and 13 week exposures showed an early Th2 response (4 weeks) that shifted toward a Th1 dominant response at 13 weeks of inhalation exposure to S. chartarum spores. Pulmonary arterial hyperplasia was the primary pathologic finding observed following histologic analysis of viable S. chartarum exposure group animals. Current efforts are focused on the analysis of miRNA, mRNA, and proteomic datasets derived from the processing of the lung homogenates of viable, nonviable and air-only control samples. A manuscript focused on the pulmonary immunological datasets is in preparation. Following the completion of the pulmonary immunology studies that evaluated the 2 strains of S. chartarum, 13-week toxicology studies were initiated. Mice were exposed to a mycotoxin producing chemotype of S. chartarum 2 times a week for thirteen weeks. The in-life phase of the toxicology study was completed in July and the pathology report was received in September. It is anticipated that the S. chartarum report will be completed in early FY18. NIOSH is currently optimizing growth and sporulation culture conditions for the study of Aspergillus versicolor. In FY17, NIOSH developed a method (optimized culture conditions) that results in reproducible growth and sporulation of A. versicolor on rice. In collaboration with the NIOSH Inhalation Team, the AGS and aerosolization parameters were optimized and a preliminary deposition study was completed. A modified local lymph node study has been completed and an estimated pulmonary deposition of 5x105 A. versicolor spores was shown to induce a 10X lymphocyte proliferation. Based on the results of the deposition and dosimetry studies, a 13 week pulmonary immunology study with A. versicolor began in May 2017. Toxicology studies with A. versicolor will be scheduled in FY18. A. alternata, mixed fungal exposures, and other occupationally relevant fungi identified in concurrent NTP funded diversity studies will be evaluated later in FY18. These toxicological studies will provide novel datasets that will be used to characterize the hazards that fungal exposure may represent to human health.
