Background
Practical methods of monitoring innate immune mucosal responsiveness are lacking. Lipopolysaccharide
(LPS) is a component of the cell wall of Gram negative bacteria and a potent
activator of Toll-like receptor (TLR)-4. To measure LPS responsiveness of the nasal
mucosa, we administered LPS as a nasal spray and quantified chemokine and cytokine levels
in mucosal lining fluid (MLF).
Methods
We performed a 5-way cross-over, single blind, placebo-controlled study in 15 healthy nonatopic
subjects (n = 14 per protocol). Doses of ultrapure LPS (1, 10, 30 or 100μg/100μl) or
placebo were administered by a single nasal spray to each nostril. Using the recently developed
method of nasosorption with synthetic adsorptive matrices (SAM), a series of samples
were taken. A panel of seven cytokines/chemokines were measured by multiplex immunoassay
in MLF. mRNA for intercellular cell adhesion molecule-1 (ICAM-1) was quantified
from nasal epithelial curettage samples taken before and after challenge.
Results
Topical nasal LPS was well tolerated, causing no symptoms and no visible changes to the
nasal mucosa. LPS induced dose-related increases in MLF levels of IL-1β, IL-6, CXCL8 (IL-
8) and CCL3 (MIP-1α) (AUC at 0.5 to 10h, compared to placebo, p<0.05 at 30 and 100μg
LPS). At 100μg LPS, IL-10, IFN-α and TNF-α were also increased (p<0.05). Dose-related
changes in mucosal ICAM-1 mRNA were also seen after challenge, and neutrophils
appeared to peak in MLF at 8h. However, 2 subjects with high baseline cytokine levels
showed prominent cytokine and chemokine responses to relatively low LPS doses (10μg
and 30μg LPS).