Abstracts (complete list) - Wissenschaft Online

Irene Wittmman, Diana Aichele, Gerhard Groer, André Gessner, Markus Schnare
Modulation of innate immune responses by recombinant
murine bactericidal permeability / increasing protein through
neutralizaton of LPS and Gram-negative bacteria
Rationale: Recognition of LPS by TLR4 initiates inflammatory responses inducing potent
anti-microbial immunity. However, uncontrolled inflammatory responses can be
detrimental. In order to prevent the development of septic shock during an infection
with Gram-negative bacteria the immune system has developed regulatory mechanisms
to neutralize LPS by specialized proteins. Here we report the recombinant expression
and functional characterization of the mouse homolog of human bactericidal
permeability / increasing protein (BPI).
Methods: Mouse BPI was stably expressed and highly purified by affinity
chromatography. RAW 267.4 cells as well as bone marrow derived dendritic cells were
stimulated with various TLR-ligands in the presence or absence of recombinant mouse
BPI (rmBPI). Activation of the cells was determined by ELISA (TNF, IL-12), NO-assay as
well as flow cytometry (CD86). In addition RAW macrophages expressing a NFκBreporter
construct were stimulated with UV-treated Gram-negative (E. coli, S.
typhimurium, N. meningitis, P. aeruginosa) as well as Gram-positive (Staph. aureus, L.
monocytogenes, group B Streptococcus) bacteria in the presence or absence of rmBPI.
The cellular activation was determined by TNF-ELISA and NFκB activity. Finally
replicating E. coli were cultured with RAW macrophages in the presence or absence of
rmBPI. The bacterial numbers as well as the cell activation was analyzed.
Results: Purified rmBPI is a 60kD protein that was able to specifically neutralize LPSmediated
activation of macrophages and to block LPS-dependent maturation of dendritic
cells. Importantly, rmBPI neutralized the capacity of UV-irradiated and live Gramnegative
bacteria to activate immune cells but it did not influence the stimulatory
properties of Gram-positive bacteria. Finally rmBPI did not influence the bacterial
growth.
Conclusion: Together these data demonstrate that murine BPI is a potent LPS
neutralizing protein that may play an important role as a negative modulator of innate
immune responses during Gram-negative infections.