Michal Olszewski, D.V.M., Ph.D.
TNF is an encapsulated yeast that causes respiratory infection in over 1 million people and kills over 600,000 people worldwide each year. It is primarily an opportunistic pathogen, infecting immunocompromised populations such as people with AIDS and transplant recipients. A Th1/Th17 T cell mediated immune response is necessary for clearance of the microbe, while a Th2/Treg T cell mediated immune response results in non-protective immunity, persistent infection and/or cryptococcal dissemination to the central nervous system and subsequent death by meningoencephalitis. TNFα is a crucial factor in host defense: hypervirulent strains of C. neoformans causing infection in immunocompetent individuals modulate the host response to produce less TNFα; AIDS patients who can no longer make TNFα are at heightened risk of death from C. neoformans infection; and patients receiving TNFα blocking antibody therapy for autoimmune diseases are at heightened risk for C. neoformans infection and its complications. Previous work with C. neoformans infection during anti-TNFα antibody treatment at day 0 has shown that while TNFα levels recover by day 14, a non-protective immune response persists in the anti-TNFα treated mice through day 28 and beyond. The mechanism by which this occurs is unknown. My thesis project investigates the effect of this TNFα depletion on dendritic cells (DCs) during cryptococcal infection. I hypothesize that TNFα is necessary to promote continuous, stable DC priming of a Th1/Th17 –type immune response by inducing epigenetic modifications promoting classical (DC1) DC activation genes and suppressing alternative (DC2) DC activation genes. I have thoroughly characterized both DCs and T cell immune polarization in a mouse model and found that in infected mice treated with anti-TNFα antibody, DC show a DC2 activation profile throughout 28 days of infection and the T cells express more Th2 and Treg cytokines and transcription factors, while DC from infected and isotype antibody treated mice have a DC1 phenotype accompanied by a robust Th1/Th17 immune response. Modeling these findings in vitro using bone marrow derived DCs (BMDCs) incubated with pro-DC1 IFNγ or pro-DC2 IL-4 in the presence or absence of TNFα, I have found that DC treated with both IFNγ and TNFα have reduced plasticity of key DC1 and DC2 genes when subsequently exposed to IL-4, indicating that the combination if IFNγ and TNFα “stabilizes” the DC1 phenotype. To assess the mechanism by which this may be occurring, I have begun by quantifying histone methyltransferase and demethylase enzyme transcript levels to determine whether any of these enzymes are induced by IFNγ, IL-4, TNFα, or the IFNγ-TNFα combination and found that histone 3 lysine 4 methyltransferase MLL1 and histone 3 lysine 27 demethylase Jmjd3 are differentially regulated between the cytokine conditions above, and further are differentially regulated in vivo. My future studies will involve modulation of epigenetic modifications through specific inhibitors of methyltransferases and demethylases, chromatin immunoprecipitation to determine which key DC1 and DC2 genes are associated with activating or repressing histone modifications, and adoptive transfer studies of “TNFα-stabilized” DCs to anti-TNFα treated, infected mice to investigate whether stabilized DCs are sufficient to confer a protective immune response to C. neoformans.
Farnand AW, Eastman AJ, Herrero R, Hanson JF, Mongovin S, Altemeier WA, Matute-Bello G. Fas Activation in Alveolar Epithelial Cells Induces KC (CXCL1) Release by a MyD88-dependent Mechanism. Am J Respir Cell Mol Biol. 2011 Jan 21.
Eastman, AJ; He, X; Qiu, Y; Davis, M; Baht, P; Lyons, D; Park, Y; Hardison, S; Malachowski, A; Osterholzer, JJ; Wormley, F; Williamson, P; Olszewski, MA. Cryptococcal HSP70 homologue Ssa1 contributes to pulmonary expansion of C. neoformans during the afferent phase of the immune response by promoting macrophage M2 polarization. Midwestern Neglected Infectious Disease Conference, Poster, Notre Dame, IN, August 2014.
Rackham Predoctoral Fellowship, University of Michigan, 2014-15