David L. Dunn, Principal Investigator
Karen R. Wasiluk, Co-Principal Investigator

Protection During Gram-negative Bacterial Sepsis

Gram-negative bacterial sepsis and shock continue to be significant causes of morbidity and mortality for surgical patients. Despite improvements in antibiotic therapy and intensive care, mortality associated with this condition remains at approximately 40%. Increasing evidence indicates that the lipid A portion of the lipopolysaccharide (LPS, endotoxin), an integral portion of the gram-negative bacterial membrane, interacts with a variety of host defenses to cause the release of cytokine mediators of sepsis, such as tumor necrosis factor-alpha, interleukin-1-beta, interleukin-6, and interleukin-8.

The objective of this project is to develop, characterize, and test LPS antagonists. There are two specific aims. The first is to develop and characterize in vitro the inhibitory activity of a large number of LPS antagonists. The second is to examine the protective capacity and to determine the mechanism(s) of action of each of these LPS antagonists in vivo in animal models of experimental gram-negative bacterial sepsis and endotoxemia. In addition to survival, the researchers are quantifying the neutralization and clearance of LPS, bacterial activity and bacterial clearance, and cytokine transcription, translation, and secretion in the local tissue milieu and the systemic circulation. The researchers compare and contrast the in vitro and in vivo results obtained from testing each type of LPS antagonist. Comparisons at the molecular level are being undertaken using sequencing and cloning techniques, to identify those critical regions of the molecule that are responsible for anti-LPS activity. This information will be used to delineate the molecular basis of endotoxin antagonism and to develop additional potent LPS antagonists.