Determining the role of epigenetic factors in antifungal drug resistance

Epigenetic factors are proteins that regulate gene expression by altering transcriptional machinery access to nucleosomes, DNA wrapped around histone proteins. Two classes of epigenetic factors are ATP-dependent chromatin remodelers and histone modifiers such as histone methyltransferases (HMTs), proteins that add methyl groups to histone tails. This study focuses on AIF4 (Antifungal-Induced Factor 4), a possible HMT induced upon neutral lipid depletion that we hypothesize is regulating antifungal drug resistance genes. Overexpression of AIF4 results in hypersensitivity to antifungal drugs. Studying epigenetic factors in the yeast Saccharomyces cerevisiae, including AIF4, can lead to better understanding of cell adaptation to their environments and insight into antifungal drug resistance of pathogenic yeast. This project will focus on identifying suppressors of AIF4’s hypersensitive phenotype and exploring whether genes in the neutral lipid pathway are necessary for AIF4 expression. To support our hypothesis, I will grow yeast colonies with overexpressed AIF4 on media containing antifungal drugs. Overexpressing AIF4 strains exposed to antifungal drugs over time suppressed the grow defect. Re-plating the suppressor colonies showed drug resistance, suggesting that a genetic mutation(s) occurred. Suppressor colonies will be analyzed for AIF4 expression and genome-wide sequencing to identify the suppressor mutation(s). In addition, I have generated deletions for genes that encode neutral lipid production enzymes, and I will determine if AIF4 expression is affected. Single and double deletions will determine if a particular neutral lipid is required for the expression of AIF4. Overall, my work will help to characterize a pathway required for AIF4 expression and drug resistance

Recently activated CD4 T cells in tuberculosis express OX40 as a target for host-directed immunotherapy

Abstract After Mycobacterium tuberculosis (Mtb) infection, many effector T cells traffic to the lungs, but few become activated. Here we use an antigen receptor reporter mouse (Nur77-GFP) to identify recently activated CD4 T cells in the lungs. These Nur77-GFPHI cells contain expanded TCR clonotypes, have elevated expression of co-stimulatory genes such as Tnfrsf4/OX40, and are functionally more protective than Nur77-GFPLO cells. By contrast, Nur77-GFPLO cells express markers of terminal exhaustion and cytotoxicity, and the trafficking receptor S1pr5, associated with vascular localization. A short course of immunotherapy targeting OX40+ cells transiently expands CD4 T cell numbers and shifts their phenotype towards parenchymal protective cells. Moreover, OX40 agonist immunotherapy decreases the lung bacterial burden and extends host survival, offering an additive benefit to antibiotics. CD4 T cells from the cerebrospinal fluid of humans with HIV-associated tuberculous meningitis commonly express surface OX40 protein, while CD8 T cells do not. Our data thus propose OX40 as a marker of recently activated CD4 T cells at the infection site and a potential target for immunotherapy in tuberculosis