Analyzing the function of CIMG_00509 in Coccidioides spp. on a host immune system
Coccidioidomycosis, or valley fever, is a respiratory illness affecting 150,000 people each year, and is caused by the dimorphic fungi Coccidioides immitis and Coccidioides posadasii. These fungi are endemic to dry, arid regions such as the southwestern United States. The disease, coccidioidomycosis, develops from inhalation of Coccidioides arthroconidia into the lungs of a mammal, upon which it enters the parasitic phase of its life cycle. The specific interactions between Coccidioides and a host immune system are largely unknown. Previous literature has shown significant upregulation of select genes during the parasitic phase, including CIMG_00509. This gene demonstrates a 24-fold increase in transcription, is highly conserved among C. immitis and C. posadasii, and bears similarities to a toxic β-Defensin-like peptide. In order to characterize the effect of CIMG_00509 on host immune cells, two subunits of the predicted protein were manufactured into peptides, named the DNA-Binding Peptide (DBP) and Toxin Peptide (TP). Activated and unactivated alveolar macrophage cell cultures were exposed to these peptides. RNA extractions were performed on the macrophages at two and six hours post exposure with varying concentrations of each peptide and activation of macrophages with IFN-γ and lipopolysaccharides (LPS). Real Time RT-PCR was utilized to identify changes in cytokine mRNA expression levels among the treatments. The results of this study provide clues to the effect of CIMG_00509 on the host immune system. Future research will include measuring the response of various immune cells (neutrophils, dendritic cells, etc.), and the effect of a CIMG_00509 gene deletion in Coccidioides on virulence in vivo. The detection of this novel toxin-homolog has the potential to improve our understanding of the diverse nature of coccidioidomycosis disease phenotypes, and improve treatment.