Bactericidal and endotoxin neutralizing activity of a peptide derived from Limulus antilipopolysaccharide factor.
BACKGROUND
Release of lipopolysaccharide (endotoxin, LPS) is a critical inciting event in the development of sepsis syndrome due to gram-negative bacteria, and mortality associated with this entity remains approximately 40%. Limulus anti-LPS factor (LALF) is a naturally occurring horseshoe crab derived protein that, unlike antibiotics, is both bactericidal for gram-negative bacteria and capable of neutralizing LPS. We hypothesized that a peptide derived from the active domain of LALF (LALF #28-54) would exhibit potent biologic activity similar to that of LALF itself and could potentially be useful as a therapeutic agent.


METHODS
The effects of LALF, synthetic peptide LALF #28-54, polymyxin B (PmB), and a biologically inactive synthetic peptide were examined in several models. In vitro bactericidal activity was determined against Pseudomonas aeruginosa, and LPS-neutralizing capacity was determined via inhibition of LPS-induced tumor necrosis factor-alpha (TNF-alpha) secretion by RAW 264.7 cells. In vivo biologic activity was determined via pretreatment following which P aeruginosa endotoxemia or bacteremia was induced; serum TNF-alpha levels, bacterial clearance, and survival were assessed.


RESULTS
LALF and LALF #28-54 exhibited potent in vitro bactericidal and LPS-neutralizing activity comparable to PmB (P <.01). However, although LALF #28-54 diminished systemic TNF-alpha production and aided bacterial clearance similar to that observed for LALF (P <.01), it did not provide significant protective capacity (P >.1).


CONCLUSIONS
These data demonstrate that peptide LALF #28-54 retained the LPS-neutralizing and bactericidal biologic activity of LALF but failed to protect during overwhelming P aeruginosa bacteremia, perhaps due to short serum half-life.
Department of Surgery, University of Minnesota, Minneapolis 55455, USA.
C A
CA
Weiss
K R
KR
Wasiluk
T A
TA
Kellogg
D L
DL
Dunn
D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides; D060829:Arthropod Proteins; D002460:Cell Line; D006737:Horseshoe Crabs; D007447:Invertebrate Hormones / Q000737:chemistry / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000633:toxicity*; D008264:Macrophages / Q000187:drug effects / Q000382:microbiology / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000494:pharmacology*; D011112:Polymyxin B / Q000494:pharmacology; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000254:growth & development; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D060829:Arthropod Proteins; D007447:Invertebrate Hormones; D008070:Lipopolysaccharides; D010446:Peptide Fragments; D014409:Tumor Necrosis Factor-alpha; C034705:antilipopolysaccharide factor (Limulus); D011112:Polymyxin B