Abstract A059: Tracking myeloid cell dynamics in response to intraperitoneal administration of a fluorescently tagged cellular autologous vaccine presenting TLR agonists in mice with advanced ovarian cancer

Abstract The Macrophage Disappearance Reaction (MDR) is a phenomenon where resident macrophages rapidly disappear from the peritoneal cavity and migrate to the omentum in response to inflammatory stimuli. In response to inflammatory stimuli, peritoneal macrophages have been shown to cluster and adhere to the mesothelium. In addition, neutrophil extracellular traps (NETs), mesh-like structures, trap microorganisms as part of the defense mechanism. Following intraperitoneal administration of fluorescent pathogen mimetic silicified cancer cells (aka vaccine), myeloid cells with internalized vaccine have been shown to accumulate in the omentum. This study explores the role of MDR and its dependence or independence from NETs in trafficking of vaccine-laden macrophages to the omentum. In mice with advanced ovarian cancer, peritoneal myeloid cells exist in peritoneal fluid as independent cells and in association with cancer spheroids. Using acoustic flow cytometry, myeloid internalization of vaccine and association with cancer spheroids was temporally regulated. Within one hour, vaccine was found in association with the periphery of the omentum. Ongoing studies are aimed at characterizing cell types present in macrophage-vaccine clusters as they adhere to mesothelial cells lining the omentum and then migrate to milky spots using multiplex fluorescent microscopy. The main objective of this study is to determine if TLR agonist modified vaccine cell trafficking in the peritoneal cavity mimics the transport of microbes and to verify which elements mediate the process. Citation Format: Arshia Chhabra, Rita E. Serda, Madigan I. Morrison. Tracking myeloid cell dynamics in response to intraperitoneal administration of a fluorescently tagged cellular autologous vaccine presenting TLR agonists in mice with advanced ovarian cancer abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Ovarian Cancer Research; 2025 Sep 19-21; Denver, CO. Philadelphia (PA): AACR; Cancer Res 2025;85 (18Suppl): Abstract nr A059.