Synthetic Peptides That Exert Antimicrobial Activities in Whole Blood and
Blood-Derived Matrices
Michael R.
Yeaman,1,2,3*
Kimberly D. Gank,2 Arnold S.
Bayer,1,2,3 and Eric P.
Brass2,3,4
Department of Medicine, Division of Infectious Diseases,1 Center
for Clinical Pharmacology, Harbor-UCLA Medical Center,4 Research and
Education Institute at Harbor-UCLA, Torrance, California 90502,2
Department of Medicine, UCLA School of Medicine, Los Angeles, California
900253
Received 18 April 2002/ Returned for modification 18 June 2002/ Accepted 12
September 2002
Peptides that exert antimicrobial activity in artificial
mediamay lack activity within blood or other complex biological
matrices.To facilitate the evaluation of antimicrobial peptides for
possibletherapeutic utility, an ex vivo assay was developed to
assessthe extent and durability of peptide antimicrobial
activitiesin complex fluid biomatrices of whole blood, plasma, and
serumcompared with those in conventional media. Novel
antimicrobialpeptides (RP-1 and RP-11) were designed based in part
on plateletmicrobicidal proteins. RP-1, RP-11, or gentamicin was
introducedinto biomatrices either coincident with, or 2 h prior to,
inoculationwith an Escherichia coli target organism.
Antimicrobial activitiesof peptides were assessed by quantitative
culture 2 h afterbacterial inoculation and compared to those of
peptide-freeand gentamicin controls. In whole blood and homologous
plasmaor serum, introduction of RP-1 or RP-11 coincident with E.
coliwas associated with a significant reduction in CFU per
milliliterversus the respective peptide-free controls. Moreover,
substantialantimicrobial activity remained when RP-1 or RP-11 was
placedinto whole blood or plasma 2 h prior to E. coli
inoculation.These results suggest that the peptides were not rapidly
inactivatedwithin these biomatrices. Peptide antimicrobial
activities werenegatively affected by preincubation in serum or in
heat-inactivatedserum, compared with those of the respective
controls. PeptidesRP-1 and RP-11 were consistently effective at
lower concentrationsin biomatrices than in artificial media,
indicating favorableantimicrobial interactions with components of
blood or bloodfractions. Collectively, these findings support the
conceptthat synthetic peptides can be designed to exert potent
antimicrobialactivities in relevant and complex biological
matrices.
* Corresponding author. Mailing address: Division
of Infectious Diseases, Harbor-UCLA Medical Center, St. John's Cardiovascular
Research Center, Harbor-UCLA Research and Education Institute, 1124 West Carson
St., Torrance, CA 90502. Phone: (310) 222-6428. Fax: (310) 782-2016. E-mail:
mryeaman{at}ucla.edu
.
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