Project description:β-glucans, which can activate innate immune responses, are a major component in the cell wall of the cyst form of Pneumocystis. In the current study we examined whether β-1,3 glucans are masked by surface proteins in Pneumocystis, and what role β-glucans play in Pneumocystis-associated inflammation. For 3 species, including P. jirovecii, which causes Pneumocystis pneumonia (PCP) in humans, P. carinii, and P. murina, β-1,3 glucans were masked in most organisms, as demonstrated by increased exposure following trypsin treatment. Using Q-PCR and microarray techniques, we demonstrated in a mouse model of PCP that treatment with caspofungin, an inhibitor of β-1,3 glucan synthesis, for 21 days, decreased expression of a broad panel of inflammatory markers, including IFN-γ, TNF-α, IL-1β, IL-6, and multiple chemokines/chemokine ligands. Thus, β-glucans in Pneumocystis cysts are largely masked, which likely decreases innate immune activation; this mechanism presumably was developed for interactions with immunocompetent hosts, in whom organism loads are substantially lower. In immunosuppressed hosts with a high organism burden, organism death and release of glucans appears to be an important contributor to deleterious host inflammatory responses.
Project description:An IRF4 de novo mutation affecting the DNA binding domain of encoded IRF4 protein (mutDBD) was identified in a patient presenting with combined immunodeficiency. The patient exhibited profound susceptibility to opportunistic infections notably Pneumocystis jirovecii and humoral immunodeficiency caused by a failure of terminal B cell differentiation. A heterozygous IRF4 missense variant resulting in a phenylalanine-to-leucine replacement within the interferon activation domain of the encoded IRF4 protein (mutIAD) was identified in three patients from a multigenerational family suffering from a novel autosomal dominant disease predominantly presenting as a hypogammaglobulinemia with recurrent infections. In this experiment we aimed to investigate the effect of the two different mutations on IRF4 genomic binding.