(1451) Removal of Circulating Mitochondrial N-Formyl Peptides Rescues Neutrophil Chemotaxis During Sepsis

Introduction: Circulating mitochondrial N-formyl peptides (mtFPs) contribute to the development of secondary nosocomial infections in sepsis patients, at least partly by suppressing formyl peptide receptor 1 (FPR1)-mediated neutrophil (polymorphonuclear leukocyte, PMN) chemotaxis, thus worsening clinical outcomes. Therefore, we hypothesized that removing circulating mtFPs from sepsis environments could rescue PMN chemotactic responses to secondarily inoculated bacteria by preventing the re-occupancy of surface FPR1 by residual mtFPs.

Methods: First, to study the effects of circulating mtFPs and mtFP clearance on PMN chemotaxis, we performed in vitro mechanistic experiments using a model system mimicking the sites of secondary infection during sepsis. Second, we investigated the ability of anti-mtFP antibodies to inhibit mtFP activities. Third, we made a beads-based anti-mtFP antibody cocktail by combining protein A/sepharose with antibodies specific for high potency human mtFPs. Finally, we investigated whether the beads-anti-mtFP cocktail could eliminate targeted mtFPs from plasma and restore PMN chemotaxis in sepsis environments by performing ex vivo experiments using blood samples obtained from patients with septic shock.

Results: We found that removal of circulating mtFPs restored FPR1-mediated PMN chemotaxis that had been suppressed by previous mtFP exposure. Further, an exposure to septic shock plasma suppressed PMN chemotactic responses to bacterial FPs. Anti-mtFP antibodies alone failed to eliminate circulating mtFPs or inhibit mtFP activities. However, the beads-anti-mtFP cocktail therapy successfully eliminated high potency mtFPs from septic shock plasma without altering other cytokine and chemokine levels. In addition, the beads-anti-mtFP cocktail therapy restored PMN chemotactic function that had been suppressed by septic shock plasma exposure.

Conclusions: Removal of circulating mtFPs from sepsis environments by anti-mtFP antibodies linked to beads rescued PMN chemotactic responses to secondary bacterial FPs. Incorporating these findings into therapeutic strategies may help improve clinical outcomes in sepsis patients by preventing development of secondary nosocomial infections.