Gene Therapy with Lipopolysaccharide Binding Protein for Gram-Negative Pneumonia: Respiratory Physiology

Abstract

Lipopolysaccharide binding protein (LBP) plays an essential role in the pulmonary immune response to gram-negative bacterial infection. LBP knockout mice with gram-negative pneumonia have increased mortality compared with wild-type controls. This mortality difference can be abolished with systemic LBP gene therapy. We postulate that LBP knockout mice will develop derangements in lung physiology from gram-negative pneumonia and that these changes can be reversed with systemic LBP gene therapy. Twelve- to 16-week-old C57BL/6 wild-type mice and/or sex, age, matched LBP knockout mice were administered 1 × 103 colony-forming units/mouse of Klebsiella pneumoniae by intratracheal inoculation. Treated mice were administered 5 × 109 plaque-forming units of recombinant adenovirus containing either the gene for LBP or the irrelevant control protein β-galactosidase by intravenous injection 2 days before bacterial inoculation. Respiratory physiology parameters were measured preinoculation and 24 hours postbacterial inoculation. Administration of LBP by systemic gene therapy to LBP knockout mice improved 7-day survival from Klebsiella pneumonia to a level equivalent to wild-type mice exposed to the same dose of bacteria (42 vs. 43% survival). LBP knockout mice given the LBP gene therapy demonstrated increased 14-day survival from Klebsiella pneumonia when compared with controls treated with β-galactosidase (28 vs. 0%, p < 0.001). LBP knockout mice developed significant differences in respiratory rate, minute ventilation, and enhanced pause (Penh), when compared with wild-type mice with Klebsiella pneumonia. These respiratory derangements were prevented with adenoviral delivery of the LBP gene before K. pneumoniae inoculation. Gram-negative pneumonia produces measurable changes in mortality and respiratory physiology between wild-type and LBP knockout mice. These changes can be prevented in LBP knockout mice by systemic gene therapy to restore innate immunity.