Will it cleave? How lipopolysaccharide structures affect complement activation 3029

Abstract Description Sepsis is currently one of the leading causes of death within hospitals. Due to overactivation of immune responses, this infection can rapidly become fatal if left untreated. Toll-like receptor 4 (TLR4) is a canonical receptor for lipopolysaccharide (LPS), the Gram-negative bacterial lipid that induces endotoxemia and associated symptoms of septic shock. In murine models of endotoxemia, without the presence of TLR4, physiologic symptoms of sepsis are not observed. To compensate for the lack of TLR4, previous research in our lab has shown that the complement cascade is activated and adverse outcomes such as internal blood clotting are still observed. Western blot was used to investigate the contribution of the lipid A portion of LPS to complement activation, lipid A structural arrangement did not change activation levels of serum complement protein C3. To quantify the correlation of length of LPS O-antigen to its ability to activate the complement cascade. Sandwich ELISAs are used to measure the amount of activated serum complement protein (C5) in the presence of endotoxin with differing lengths of O-antigen. A 5-log dilution series from 10µM to 1 nM of LPS, LOS, and Kdo2 is used. Identifying the contribution of these compensatory pathways being activated in the absence of classic receptors can help develop therapeutics to result in better prognoses for immune suppressed patients in septic shock. Funding Sources Supported by the Undergraduate Research Grant from Towson University’s Fisher College of Science and Mathematics. Topic Categories Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)