Modulation of Immune Defenses in Pathobiology of Chronic Infections

Veterans Health Administration, Decatur PA

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Abstract

DESCRIPTION (provided by applicant): Cryptococcus neoformans is a common and devastating opportunistic fungal pathogen that causes substantial mortality worldwide. Current therapies for veterans infected with C. neoformans or related fungal pathogens are lengthy, frequently toxic, and often ineffective. Generation and maintenance of this type 1 or classically-activated immune response over extended time is required to achieve complete clearance of C. neoformans and to prevent the all too common development of persistent infection and/or relapses. One of the side effects of the increasingly prescribed anti-inflammatory TNF?eutralizing monoclonal antibody therapy is susceptibility to fungal infections (including C. neoformans). Our preliminary data strongly suggest that TNF?s a central molecule required for programing of type 1 dendritic cell (DC1) and the subsequent development of a stable, protective Th1/Th17 response. The present studies are designed to determine how TNF?ontributes to programming of myeloid DC to sustain a protective Th1/Th17 response throughout the extended time period required for clearance of C. neoformans. Hypothesis: Our central hypothesis is that effective clearance of C. neoformans requires the TNF?ediated DC1 programming of myeloid DC to sustain a protective Th1/Th17 response throughout the extended time period required for clearance of C. neoformans. We further hypothesize that TNF?ignaling in DC and/or their myeloid precursors contributes to execution of epigenetic modifications that support stability of the DC1 phenotype and prevents the development of a DC2 phenotype. The following aims have been constructed to rigorously test this hypothesis. Aim 1: To determine whether TNF?s required for stable DC1-programing during the protective response to cryptococcal infection. Aim 2: To determine if TNF?ediates epigenetic programing of the DC1 phenotype in myeloid precursors and/or DC in C. neoformans infected lungs. Aim 3: To determine whether TNF?nduced DC1 programming is necessary and sufficient for generating protective immune responses to C. neoformans. Research Plan and Methods: Our proposal utilizes highly translational model of infection of CBA/J mice with the moderately virulent C. neoformans strain 24067 and series of in vitro studies that will define the effects of transient TNF?epletion using one dose of monoclonal antibodies at the time of infection. These studies will allow us to define whether, and to what degree, TNF?nduces stability of the DC1 program. We will define at which stage of DC development (bone marrow precursor, DC differentiation or maturation) TNF?tabilizes DC. We will determine whether the DC1 phenotype stability can be attributed to changes in enzymes responsible for epigenetic chromatin modification and resultant changes in histone methylation signatures at gene promoter regions crucial for execution of DC1 program. The contribution of DC and their myeloid precursors to the execution of stable protective immune responses in the lungs will be then tested in a series of adoptive transfer experiments. Completion of these studies will demonstrate a novel role of TNF?n stabilization of a protective immune response to C. neoformans. This translational study will provide a link between epigenetic chromatin modification and biological effects of TNF?n vivo and provide an insight into a potential mechanism of increased risk of fungal infections in patients treated with anti-TNF?ntibodies, which our lab's mouse model very effectively mimics.