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Peptide effectors of innate immunity
P a r t i c i p a n t s :
Maurizio Simmaco, Giuseppina Mignogna, professors;
M. Luisa Mangoni, Rossella Miele, researchers; Marina
Borro, Giovanna Gentile, post-doc fellows; Alessandra
Franco, technician.
C o l l a b o r a t i o n s :
Institute of Physiology and Pathophysiology, Paracelsus Medical
University, Salzburg, Austria (Prof. Günther Kreil); Centro de
Investigaciones Biológicas (CSIC) Madrid, Spain (Prof. Luis
Rivas); Department of Biological Chemistry, Weizmann Institute
of Science, Rehovot, Israel (Prof. Yechiel Shai).
Report of activity
Beside searching for novel antimicrobial peptides
from amphibian sources, we intend to exploit in
more detail the peptide parameters responsible for
the target selectivity of the peptides available in our
laboratory and to select natural peptides or design
analogues that, for their spectrum of activity, mechanism
of action, stability, lack of toxicity, low induction
of microbial resistance, may represent ideal
compounds for in vivo studies to better evaluate
their potential antimicrobial/anticancer effects.
Recent studies performed in our laboratory have
suggested that minor changes in the sequence of
even small peptides like temporins can significantly
affect their target selectivity and that both the
cationic character, amphipathicity and peptide
length are important determinants for the antibacterial
potency of these molecules.
Because of the increasing emergence of microbes
which are resistant to conventional antibiotics, the discovery
of new antimicrobial agents with a new mode
of action is urgently needed. Naturally occurring
antimicrobial peptides (AMPs), which are produced by
almost all forms of life, represent promising candidates
for the development of new anti-infective drugs.
Principal investigator: Donatella Barra
Professor of Biochemistry
Dipartimento di Scienze Biochimiche "A. Rossi Fanelli"
Tel: (+39) 06 4456663; Fax: (+39) 06 4440062
donatella.barra@uniroma1.it
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New antimicrobial and antiviral agents - AREA 6
Amphibian skin is one of the richest sources for such
molecules. In contrast with conventional antibiotics,
most AMPs interact with and increase the permeability
of the bacterial membrane as part of their
killing mechanism. However, before reaching it, they
need to cross the cell wall that, in Gram-negative
bacteria, is surrounded by the lipopolysaccharide
(LPS)-outer membrane, which forms a very efficient
barrier against a variety of hydrophilic and
hydrophobic compounds.
We first compared the in vitro bactericidal activities
of five AMPs from three different species of anurans
against multidrug-resistant clinical isolates
belonging to species often involved in nosocomial
infections (Staphylococcus aureus, Enterococcus faecium,
Pseudomonas aeruginosa, Stenotrophomonas maltophilia
and Acinetobacter baumannii). The peptides tested
were: the short and mildly cationic temporins A, B,
and G from Rana temporaria (13-residues long with
a net charge of +3); the 1-18 fragment of esculentin
1b [Esc(1-18)] from Rana esculenta; and the
20-residues bombinin H2 from Bombina variegata.
All these peptides were able to kill microorganims at
concentrations ranging from 0.5 to 48 microM, with
only few exceptions. In particular, temporins were
more active against Gram-positive bacteria, especially
when assayed in human serum; Esc(1-18) showed
a fast and strong bactericidal activity against the
Gram-negative species, at concentrations of 0.5-1
microM; bombinin H2 displayed a similar potency
towards all isolates. Interestingly, while in 20%
human serum temporins and bombinin H2 were
almost completely inhibited against the Gram-negative
species, Esc(1-18) partially preserved its antimicrobial
efficacy also in the presence of 40% serum.
This property renders the latter peptide an attractive
molecule for the development of new compounds for
the treatment of infectious diseases.
To address the issue that more than 10 isoforms of
temporins are produced within the same frog specimen,
we tested temporins A, B and L in combination