Search

Background: We previously demonstrated an essential role for lipopolysaccharide binding protein (LBP) in the pulmonary immune response to Gram-negative bacterial infection. LBP knockout mice had significantly higher mortality, greater rates of bacteremia, and higher counts of viable bacteria in their lungs at sacrifice compared with wild-type controls. We postulate that systemic LBP gene therapy will reconstitute a protective innate immune response in LBP knockout mice and that overexpression of LBP in wild-type mice may offer a survival advantage., Methods: 12-16 week old female C57BL/6 wild-type mice and age matched LBP knockout mice were given 5 x 10(9) PFU of recombinant adenovirus containing either the gene for LBP or the irrelevant control protein beta-galactosidase by tail vein injection. 72 hours later each mouse was administered 1 x 10(3) CFU of Klebsiella pneumoniae by intratracheal injection., Results: Administration of LBP by systemic gene therapy to LBP knockout mice improved survival from Klebsiella pneumonia to a level equivalent or better than wild-type mice exposed to the same dose of bacteria (36 versus 25%). Wild-type mice given the LBP gene therapy demonstrated increased 7 day survival from Klebsiella pneumonia when compared with controls treated with beta-galactosidase (68 versus 30%, p = 0.03)., Conclusions: Systemic gene therapy with intravenous adenoviral vector transfer of LBP significantly improves survival in LBP knockout mice. Overexpression of LBP in wild-type mice improves survival from Klebsiella pneumonia. Raising levels of LBP in the setting of Gram-negative pneumonia may be of therapeutic benefit.

Lipopolysaccharide (LPS)-binding protein (LBP) greatly facilitates LPS activation of monocytic cells through the CD14 receptor, triggering activation of innate immune responses. An acute phase protein, LBP is produced predominantly by the liver; however, we and others have shown that LBP is produced extrahepatically in multiple locations, including the lung. The importance of LBP in the lung has remained unclear. LBP may make the host more acutely sensitive to LPS and development of septic complications; alternatively, it may be protective, aiding in detection, opsonization, and killing of bacteria. Our objective was to determine the role LBP plays in local pulmonary immune defenses to bacterial challenge. LBP knockout mice and age-matched C57BL/6 wild-type controls were challenged with direct intratracheal inoculation of Klebsiella pneumoniae. We observed a significant increase in mortality, earlier onset of bacteremia, and greater pulmonary bacterial loads in LBP knockout mice compared with controls. Total lung myeloperoxidase (MPO) activity, neutrophil recruitment to the alveolar space, and levels of KC--a chemokine involved in neutrophil recruitment--in bronchoalveolar lavage (BAL) fluid and lung homogenates were found to be significantly diminished in knockout mice compared with controls. Together, our findings suggest that LBP is essential in local pulmonary innate immune responses against bacteria.

Objective: Septic complications and the emergence of drug-resistant microbes represent serious risks to patients. Recently, naturally occurring peptides have been discovered that possess potent and broad-spectrum antimicrobial activity. Protegrin-1 is particularly attractive for clinical use in human wounds because, unlike defensins, protegrin-1 retains broad antimicrobial and antifungal activity at physiologic salt concentration and in the presence of serum. The objective of this study was to examine the efficacy of protegrin-1 in killing multiple drug-resistant microbes isolated from human burn patients., Design: For thein vitroexperiment, bilayer radial diffusion was performed comparing standard antibiotics with protegrin-1 on multiple-drug-resistant microbial organisms isolated from infected burn wounds. In vivo, rats received a 20% total body surface area partial-thickness burn by immersion in 60 degrees C water for 20 secs followed by wound seeding with 106 colony forming units of Silvadene-resistant Pseudomonas aeruginosa., Setting: University of Michigan research laboratory., Subjects: Adult, male Sprague-Dawley rats., Interventions: Rats were randomized into three groups: those receiving synthetic protegrin-1, acetic acid (carrier), or gentamicin (positive control). Protegrin-1 was administered by topical application or intradermal injection. Wound tissues were harvested aseptically at different time points for quantitative bacterial counts., Measurements and Main Results: In vivo and in vitro experiments revealed rapid and significant decreases in bacterial counts for protegrin-1-treated groups compared with controls., Conclusions: This study shows that protegrin-1 potentially may be used as an alternative or adjunct therapy to standard agents used to treat wound infections.