Lipopolysaccharide-mediated protection against Klebsiella pneumoniae-induced lobar pneumonia: intranasal vs. intramuscular route of immunization.

Immunoprotective potential of delivered lipopolysaccharide (LPS) preparation from Klebsiella pneumoniae was determined in a murine model of lobar pneumonia. Protection was assessed with three doses of LPS (25, 50 and 100 microg; without any adjuvant) administered intranasally or intramuscularly. After evaluation of lung tissue (bacterial load and histopathology), no significant protection was observed at 25 microg with either application. A significant decrease in lung bacterial load coupled with fall in severity of lung lesions was observed with 50 microg (again both applications). At 100 microg dose, with intramuscular route, a further decrease in the lung bacterial load was shown compared to the 50 microg dose. In contrast, 100 microg LPS, when given intranasally, resulted in a higher bacterial colonization of the lung tissue and higher lung pathology; thus we recommend intramuscular instead of the intranasal route for developing protection against K. pneumoniae-mediated pneumonia with intact LPS-based vaccines.