The Impact of SARS-CoV-2 Immune Dysregulation on Antifungal Immunity

Project Summary Despite hundreds of published articles, meta-analyses, and reviews describing the clinical syndrome of COVID-Associated Pulmonary Aspergillosis (CAPA), there have been zero publications to date exploring the mechanism by which individuals with severe SARS-2 infection succumb to 2° mold infection. This proposal seeks to evaluate the novel conceptual advancement that immune responses targeting intracellular viral pathogens, like SARS-2, promote 2° mold infection via release of bioavailable iron, delayed neutrophil (PMN) recruitment, and decreased antifungal effector (αFE) expression. In Aims 1-3, we explore the hypotheses that lytic programmed cell death (PCD) in pulmonary epithelial cells (PEC) and red blood cell hemolysis increase the availability of nutrients including iron/heme which drive siderophore- dependent acceleration in mold growth. Concurrently, SARS-2 and the antiviral cytokine milieu mitigate PMN recruitment and activation resulting in spore germination into large invasive hyphae that overwhelm αFE mechanisms enabling 2° mold infection in an otherwise immunocompetent host. In Aim1, we will quantify iron, heme, divalent cations, host metal sequestration proteins (MSP), antiviral cytokines, and PMN-recruiting chemokines in SARS-2 BALs vs control infection cohorts (IC). We will also use immunofluorescence (IF) and spatial transcriptomics to characterize lytic PCD, viral ORF3a-mediated cell lysis, and αFE expression in FFPE lung tissues and utilize isogenic mutant fungi to identify critical host and microbial factors mediating mold growth in BALs. In Aim2, we will utilize novel Calu-3 knockout (KO) cell lines and 1°normal human bronchiole epithelial (NHBE) air liquid interface cell cultures to study the impact of the lower airway milieu and direct SARS-2 infection on PEC: lytic PCD, IFN synthesis, αFE secretion, metal sequestration, and ability to respond to 2° fungal stimuli. We will also utilize isogenic mutant fungi to identify critical pathways mediating mold growth and an innovative PMN airway transmigration model to determine the impact of Type I and III IFNs, iron/heme toxicity, and SARS-2 uptake on PMN recruitment, activation, and fungal killing. In Aim3, we will utilize novel conditional KO mice, fluorescent viral and fungal reporter strains, IF, flow cytometry, and single cell sequencing to assess the potential of SARS-2 variants to induce lytic PCD, define the role of lytic PCD and IFN signaling in PECs, macrophages (Mφ), and PMNs, and evaluate their impact on lung pathology, metal release, PMN- recruitment, spore viability, fungal growth, and infection outcome. We will also dissect key host MSP and fungal pathways mediating mold growth, evaluate the role of Mφ and PMN hACE2 on viral and fungal clearance and determine if small molecule inhibitors of lytic PCD, iron chelators, and siderophore biosynthesis inhibitors prevent or mitigate the development of 2° mold infection. We believe that the results of the proposed study will shed new light on the fundamental biology mediating CAPA and may enable the development of improved therapeutic regimens that mitigate the risk of acquiring and succumbing to this devastating infection.