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Antimicrobial Agents and Chemotherapy, December 1998, p. 3269-3275, Vol. 42, No. 12
Departments of Anesthesia and Medicine, The
University of California, San Francisco, California
94143,1 and
Palo Alto Institute of
Molecular Medicine, Mountain View, California
940432
Received 28 May 1998/Returned for modification 6 August
1998/Accepted 12 September 1998
CAP18 (cationic antimicrobial protein; 18 kDa) is a
neutrophil-derived protein that can bind to and inhibit various
activities of lipopolysaccharide (LPS). The 37 C-terminal amino acids
of CAP18 make up the LPS-binding domain. A truncated 32-amino-acid C-terminal fragment of CAP18 had potent activity against
Pseudomonas aeruginosa in vitro. We studied the
antimicrobial and LPS-neutralizing effects of this synthetic truncated
CAP18 peptide (CAP18106-137) on lung injury in mice
infected with cytotoxic P. aeruginosa. To determine its
maximal effect, the CAP18106-137 peptide was mixed with
bacteria just prior to tracheal instillation, and lung injury was
evaluated by determining the amount of leakage of an alveolar protein
tracer (125I-albumin) into the circulation and by the
quantification of lung edema. The lung injury caused by the
instillation of 5 × 105 CFU of P. aeruginosa was significantly reduced by the concomitant instillation of CAP18106-137. However, the administration of CAP18106-137 alone, without bacteria, induced lung
edema, suggesting that it has some toxicity. Also, the peptide did not significantly reduce the number of bacteria that had been
simultaneously instilled, nor did it significantly improve the survival
of the infected mice. The addition of CAP18106-137 to
aztreonam along with the bacteria did decrease the level of
antibiotic-induced release of inflammatory mediators including tumor
necrosis factor alpha, interleukin-6, and nitric oxide and also
improved the survival of the mice. Therefore, more investigations are
needed to confirm the toxicities and the therapeutic benefits of
CAP18106-137 as an adjunctive therapy to antibiotics in
the treatment of infections caused by gram-negative bacteria.
0066-4804/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Evaluation of Antimicrobial and
Lipopolysaccharide-Neutralizing Effects of a Synthetic CAP18 Fragment
against Pseudomonas aeruginosa in a Mouse Model
*
Corresponding author. Mailing address: Departments of
Anesthesia and Medicine, The University of California, San Francisco, CA 94143. Phone: (415) 476-8968. Fax: (415) 476-8841. E-mail: jwk{at}jemo.ucsf.edu.
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