Radiolabelled antimicrobial peptides for imaging of infections: A review

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 mo noclonal 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 ima ging of bacterial infections. Antimicrobial peptides are a recently discove red component of the innate defence system of plants, animals and humans. T hese peptides, which now number more than 100, with proven microbicidal act ivity against a variety of micro-organisms, share certain properties, such as their small size and cationic charge. The latter allows them to bind pre ferentially to a broad spectrum of micro organisms. We have recently demons trated that radiolabelled human defensins allow the rapid visualization of bacterial infections in mice. Furthermore, binding of this antimicrobial pe ptide to bacteria is the major factor contributing to the accumulation of t his tracer in bacterial infections. Based on these considerations, we belie ve that radiolabelled antimicrobial peptides will be an important asset in the imaging of infections in patients. ((C) 1998 Lippincott Williams & Wilk ins).