969. GRP78 and Integrin β1/α3 Play Disparate Roles in Epithelium Invasion During Mucormycosis

Abstract

BackgroundMucormycosis is a lethal fungal infection caused by Mucorales. Inhalation is the major route of entry resulting in rhino-orbital or pulmonary infections. Nasal and lung epithelial cells are among the first cells that encounter inhaled spores. We sought to identify the nasal and lung epithelial cell receptors interacting with Rhizopus during tissue invasion.Methods R. delemar-induced nasal (CCL30) or lung epithelial (A549) cell invasion was studied using Uvetix dye, while host cell injury was determined by 51Cr-release assay. Epithelial cell receptors were isolated by affinity purification of biotinylated host cell membrane proteins and then identified by LC-MS. Blocking antibodies were used to confirm the role of the receptor in the invasion/injury assays. For survival studies, ICR mice were immunosuppressed with cyclophosphamide and cortisone acetate on day-2, +3, and +8. Mice were infected with 2.5 × 105R. delemar spores intratracheally, and then treated with a single dose of 100 μg (i.p.) anti-β1 integrin antibody. Placebo mice received 100 µg of isotype-matching IgG.Results R. delemar invades and damages both cells in a time-dependent manner. Nasal Grp78 and alveolar β1α3 integrin were isolated as putative receptors. Polyclonal antibodies targeting Grp78 or β1 integrin blocked R. delemar-mediated endocytosis of nasal and lung cells by ~70%. Also, anti-Grp78 and anti-β1 integrin antibodies blocked R. delemar-induced nasal and lung cell injury by ~60% (P < 0.001). Elevated glucose, iron, or BHB increased the expression of nasal Grp78 by 2- to 6-fold which resulted in enhanced R. delemar-mediated invasion and injury of host cells, while having no effect on β1α3 integrin expression. Finally, β1 antibodies protected mice from mucormycosis with median survival time of 16 days for treated mice versus 11 days for placebo and an overall survival of 30% versus 0% for placebo mice (P = 0.0006).ConclusionThe upregulation of Grp78 on nasal epithelial cells in response to physiological elevated concentrations of glucose, iron, and BHB and subsequent enhanced invasion likely to provide insights into why diabetics in ketoacidosis are infected with the rhino-orbital mucormycosis rather than pulmonary disease. Our studies also provide a foundation for therapeutic interventions against mucormycosis.Disclosures All authors: No reported disclosures.