At present, it is difficult to distinguish between
bacterial infections and sterile inflammatory processes using
radiopharmaceuticals. This is so for a variety of reasons, including binding to bacteria with low affinity (e.g.
infection) and binding to a specific micro-organism (e.g. radiolabelled
monoclonal antibodies or F(ab)2 fragments thereof against micro-organisms). In this review, we propose that radiolabelled
antimicrobial peptides should be the first choice in the development of new
radiopharmaceuticals for imaging of
bacterial infections.
Antimicrobial peptides are a recently discovered component of the innate defence system of plants, animals and humans. These
peptides, which now number more than 100, with proven microbicidal activity against a variety of micro-organisms, share certain properties, such as their small size and cationic charge. The latter allows them to bind preferentially to a broad spectrum of micro-organisms. We have recently demonstrated that radiolabelled human
defensins allow the rapid visualization of
bacterial infections in mice. Furthermore, binding of this
antimicrobial peptide to bacteria is the major factor contributing to the accumulation of this tracer in
bacterial infections. Based on these considerations, we believe that radiolabelled
antimicrobial peptides will be an important asset in the imaging of
infections in patients.