The dose response of inhaled LPS challenge in healthy subjects

Lipopolysaccharide (LPS) inhalation causes neutrophilic airway inflammation. We used LPS produced to Good Manufacturing Practice (GMP) standards to characterise the dose response. A total of 15 healthy non-smoking subjects inhaled 5-, 15- and 50-µg LPS. Whole blood cell counts and serum C-reactive protein (CRP) were measured at baseline and up to 24 h post challenge. Sputum was induced at baseline and 6 h post challenge for cell counts and quantification of myeloperoxidase (MPO), interleukin (IL)-1β, IL-6, IL-8 and tumour necrosis factor α (TNF-α) in supernatants. LPS inhalation was well tolerated. Blood neutrophil counts increased at 6 h post LPS with all doses. Serum CRP significantly increased with 15- and 50-µg LPS. All LPS doses significantly increased sputum neutrophil percentage (P < 0.001). IL-1β, IL-6 and TNF-α were significantly increased in sputum supernatant following challenge with 50-µg LPS, there was no change in MPO or IL-8. The 50-µg LPS was well tolerated and produced a robust inflammatory response. This study supports the use of 50-µg GMP-grade LPS as a suitable challenge agent in clinical trials.