Project description:We developed a seminested PCR for the diagnosis of histoplasmosis that amplifies a portion of the Histoplasma capsulatum H antigen gene. This assay is highly sensitive and specific, being able to detect genomic material corresponding to less than 10 yeast cells without cross-reaction against other bacterial or fungal pathogens.
Project description:Allergens such as house dust mites (HDM) and papain induce strong Th2 responses, including elevated IL-4, IL-5, and IL-13 and marked eosinophilia in the airways. Histoplasma capsulatum is a dimorphic fungal pathogen that induces a strong Th1 response marked by IFN-? and TNF-? production, leading to rapid clearance in nonimmunocompromised hosts. Th1 responses are generally dominant and overwhelm the Th2 response when stimuli for both are present, although there are instances when Th2 stimuli downregulate a Th1 response. We determined if the Th2 response to allergens prevents the host from mounting a Th1 response to H. capsulatum in vivo. C57BL/6 mice exposed to HDM or papain and infected with H. capsulatum exhibited a dominant Th2 response early, characterized by enhanced eosinophilia and elevated Th2 cytokines in lungs. These mice manifested exacerbated fungal burdens, suggesting that animals skewed toward a Th2 response by an allergen are less able to clear the H. capsulatum infection despite an intact Th1 response. In contrast, secondary infection is not exacerbated by allergen exposure, indicating that the memory response may suppress the Th2 response to HDM and quickly clear the infection. In conclusion, an in vivo skewing toward Th2 by allergens exacerbates fungal infection, even though there is a concurrent and unimpaired Th1 response to H. capsulatum.
Project description:Histoplasma capsulatum var. duboisii (Hcd) infections have been well documented to cause chronic granulomatous disease, mainly involving the skin of baboons and humans in African countries primarily. This retrospective study classified the subspecies of Histoplasma and developed a phylogenetic tree utilizing DNA sequences extracted from formalin-fixed, paraffin embedded (FFPE) tissues from 9 baboons from a research colony in Texas histologically diagnosed with Hcd. Based on sequence analysis of ITS-2, Tub-1, and ARF, Hcd isolated from the archived samples closely aligns with the African clade and has 88% sequence homology with a sample isolated from an individual in Senegal.