Enhancement of lipopolysaccharide-induced tumor necrosis factor secretion by hyperimmune serum from chronic infected patients

Abstract

Patients with cystic fibrosis (CF) and chronic Pseudomonas aeruginosa lung infection have a very high load of endotoxins in their lungs. However, sepsis practically never occurs in this group of patients and the presence of tumor necrosis factor (TNF)-alpha (one of the mediators of septic shock) in serum from chronically infected CF patients is contentious. The purpose of this study was to investigate the effect of hyperimmune serum from patients with CF on lipopolysaccharide (LPS, endotoxin)-induced TNF secretion from human peripheral blood mononuclear cells (PBMC). PBMC were purified from healthy donors and stimulated with a mixture of purified LPS from P. aeruginosa and serum from chronically infected CF patients or healthy controls. TNF in the cell supernatants was detected by an enzyme-linked immunosorbent assay method. CF sera showed a pronounced potentiating effect on TNF secretion from human PBMC induced by LPS from P. aeruginosa. In comparison, serum from healthy controls did not have this effect. By contrast, CF serum and serum from healthy controls showed only little potentiating effect when using LPS from Salmonella abortus equi at concentrations above 0.01 microgram/ml per 2 x 10(6) PBMC. This indicates a specific interaction between P. aeruginosa LPS and CF serum which enhances TNF secretion. The TNF responses varied depending on the sera used in the preincubation with LPS, and correlated positively to the specific IgG, IgA, and IgM anti-P. aeruginosa LPS titers of the sera. However, since TNF is hardly detectable in sera from these patients another LPS- and/or TNF-inhibitory activity may be present in these sera.

Experimental chronic Pseudomonas aeruginosa lung infection in rats

“…The P. aeruginosa LPS in the P. aeruginosa sonicate did not show the same effect as E. coli LPS. This is on account of the lower concentration of LPS in the sonicate (only part of the 100 pg antigen used) and the lower potency of P. aeruginosa LPS (10,11,20). It has been shown that approximately 100 to 1000 times more P. aeruginosa LPS than E. coli LPS is required to induce E-selectin necessary for PMNs trafficking from the vascular compartment to extravascular tissues (lo).…”

“…Furthermore, LPS is responsible for the complement activation leading to inflammation around P. aeruginosa biofilms (14). In the presence of specific antibodies, P. aeruginosa LPS and other antigens are even stronger complement MN and PMN activators (20,21,28). The reason for the improved survival of rats stimulated with E. coli LPS or vaccinated with P. aeruginosa sonicate is therefore probably a more efficient recruitment of PMNs to combat the challenging bacteria within the first 48 h after challenge.…”