Radiopharmaceuticals: New antimicrobial agents

Università di Pisa, Pisa, Tuscany, Italy
Trends in Biotechnology (Impact Factor: 11.96). 03/2003; 21(2):70-3. DOI: 10.1016/S0167-7799(02)00032-X
Source: PubMed


Small antimicrobial peptides are good candidates for new antimicrobial agents. A scintigraphic approach to studying the pharmacokinetics of antimicrobial peptides in animals has been developed. The peptides were safely and reproducibly labelled with technetium-99m and, after intravenous injection of the radiolabelled peptides into infected animals, scintigraphy allowed real-time quantification of the peptide in the various body compartments. Antimicrobial peptides rapidly accumulated at sites of infection but not at sites of sterile inflammation, indicating that radiolabelled antimicrobial peptides could be used in detection of infection. These radiopharmaceuticals enabled the efficacy of antibacterial therapy in animals to be monitored. The scintigraphic approach provides a useful method for investigating the pharmacokinetics of small peptides in animals.

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Available from: Antonella Lupetti
    • "Although antimicrobial peptides have different chemical structures, the basis of their antimicrobial activities is the interaction of the cationic (positively charged) domains of the peptides with the (negatively charged) surface of microorganisms (Figure 1). Given that microbial membranes expose negatively charged phospholipids, such as LPS or teichoic acids, on their surface, whereas mammalian cells segregate lipids with negatively charged head groups into the inner leaflet, it is conceivable that antimicrobial peptides bind preferentially to pathogens over mammalian cells [130]. "
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    ABSTRACT: Nuclear medicine imaging techniques offer whole body imaging for localization of number and site of infective foci inspite of limitation of spatial resolution. The innate human immune system contains a large member of important elements including antimicrobial peptides to combat any form of infection. However, development of antibiotics against bacteria progressed rapidly and gained popularity over antimicrobial peptides but even powerful antimicrobials failed to reduce morbidity and mortality due to emergence of mutant strains of bacteria resulting in antimicrobial resistance. Differentiation between infection and inflammation using radiolabeled compounds with nuclear medicine techniques has always been a dilemma which is still to be resolved. Starting from nonspecific tracers to specific radiolabeled tracers, the question is still unanswered. Specific radiolabeled tracers included antibiotics and antimicrobial peptides which bind directly to the bacteria for efficient localization with advanced nuclear medicine equipments. However, there are merits and demerits attributed to each. In the current paper, radiolabeled antibiotics and radiolabeled peptides for infection localization have been discussed starting with the background of primitive nonspecific tracers. Radiolabeled antimicrobial peptides have certain merits compared with labeled antibiotics which make them superior agents for localization of infective focus.
    No preview · Article · May 2012 · International Journal of Peptides
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    • "Recently, the binding of one specific (radiolabeled) synthetic fragment from UBI to various bacteria and fungi was established and enabled accumulation and visualization of experimental infections [18] [19] and the monitoring of antimicrobial therapy [14]. The observation that the synthetic fragments of UBI target to infection sites [12] opens perspectives for antimicrobial treatment with UBI derived peptides in patients [1] [13]. UBI 1–59 is of human origin and is not expected to be immunogenic for man and resistance induction is expected to be significantly lower than for classical antibiotics. "
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    ABSTRACT: The presence and antimicrobial activity of antimicrobial peptides (AMPs) has been widely recognized as an evolutionary preserved part of the innate immune system. Based on evidence in animal models and humans, AMPs are now positioned as novel anti-infective agents. The current study aimed to evaluate the potential antimicrobial activity of ubiquicidin and small synthetic fragments thereof towards methicillin resistant Staphylococcus aureus (MRSA), as a high priority target for novel antibiotics. In vitro killing of MRSA by synthetic peptides derived from the alpha-helix or beta-sheet domains of the human cationic peptide ubiquicidin (UBI 1-59), allowed selection of AMPs for possible treatment of MRSA infections. The strongest antibacterial activity was observed for the entire peptide UBI 1-59 and for synthetic fragments comprising amino acids 31-38. The availability, chemical synthesis opportunities, and size of these small peptides, combined with their strong antimicrobial activity towards MRSA make these compounds promising candidates for antimicrobial therapy and detection of infections in man.
    Full-text · Article · Dec 2006 · Peptides
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    ABSTRACT: Neutralization and sequestration of bacterial lipopolysaccharide which plays a key role in gram-negative sepsis is required to block the progression of sepsis at early stages in addition to destroying bacteria. Many of the host defense peptides which have antimicrobial activity are also able to bind to and neutralize LPS, however, these two activities do not necessarily correlate. Due to its toxicity application of polymyxin B as the prototype of LPS neutralizing peptide is limited to topical applications and extracorporeal removal of endotoxin. Development of novel endotoxin neutralizing peptides without the toxicity of polymyxin B have been based on the natural host defense peptides, fragments of LPS binding proteins and engineered peptides. Neutralization of LPS can be achieved through several different peptide fold motifs, which are reviewed in this article. Endogenous host defense peptides, fragments of endotoxin-binding proteins and synthetic anti-endotoxin peptides fold into alpha-helical, beta-hairpin, extended and compact conformations without regular secondary structure. In animal models many of the peptides have demonstrated good in vitro and in vivo endotoxin neutralizing activity but up to now none of the peptides has been approved for clinical application with an anti-endotoxin indication. Recent developments include preparation of novel types of endotoxin neutralizing compounds such as peptides modified by lipophilic moieties and non-peptidic molecules, particularly lipopolyamines and on the other hand additional medical applications such as extracorporeal endotoxin removal, targeting to inflammation sites or endotoxoid based vaccines.
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