Antimicrobial Peptides as Infection Imaging Agents: Better Than Radiolabeled Antibiotics

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.

Leukocyte and bacteria imaging in prosthetic joint infection

“…The basis of their antimicrobial activity is the direct interaction with the bacterial plasma membrane by electrostatic and hydrophobic interaction (Chianelli et al, 2008). A range of human antimicrobial peptides, e.g., human lactoferrin (hLF), ubiquicidin 29-41 peptide fragment (UBI 29-41), human neutrophil peptide 1-3 (HNP 1-3), bacteriophage and synthetic peptides derived from these natural peptides, have been investigated as radiopharmaceuticals for imaging of infections (Akhtar et al, 2012). 99m Tc-UBI 29-41, radiolabelled synthetic fragment of ubiquicidin, is an antimicrobial peptide that preferentially binds to bacteria and fungi in vitro and accumulates at the site of infection in experimental animal studies, with fast renal clearance with minimal hepatobiliary excretion and the ability to detect infection foci in humans.…”

Patient and Personnel Radiation Exposure in Sentinel Lymph Node Practice

“…Antimikrobiyal aktiviteleri bakteri plazma membranı ile direkt ilişki halinde ortaya çıkar. İnsan laktoferrini (hLF; Candida albicansa öncelikli bağlanır), ubiquisidin 29-41 sentetik peptid fragmanı (UBI 29-41), insan nötrofil peptidi 1-3, bakteriyofaj ve doğal peptidlerden üretilen sentetik peptid deriveleri gibi pek çok insan antimikrobiyal peptidleri, enfeksiyon görüntülemede radyofarmasötik olarak araştırılmıştır (64,65,66). Deneysel hayvan çalışmalarında, renal klirensi hızlı, hepatobiliyer atılımı çok az olan Tc-99m işaretli UBI 29-41, in vitro olarak bakteri ve funguslara bağlanmış ve enfeksiyon odağında tutulmuştur.…”

curácia da cintilografia com 99mTc-Ubiquicidina (29-41) no diagnóstico diferencial de infecções musculoesqueléticas e processos inflamatórios estéreis

“…Esse método tem mostrado elevada acurácia em estudos que avaliam o diagnóstico diferencial entre infecção e inflamação estéril de tecidos ósseos, partes moles, pé diabético e próteses [1][2][3][4][5] . A ubiquicidina é um polipeptídeo presente naturalmente em humanos 6 que foi isolado inicialmente de macrófagos de camundongos [7][8] . Seu fragmento de aminoácidos 29-41 é carregado positivamente e se liga de maneira específica à superfície celular de bactérias e fungos, que são carregadas negativamente [9][10] .…”

“…Seu fragmento de aminoácidos 29-41 é carregado positivamente e se liga de maneira específica à superfície celular de bactérias e fungos, que são carregadas negativamente [9][10] . Esse peptídeo não se liga à superfície de bactérias mortas 7 . O radiofármaco possui excreção renal 10 Tc-ubiquicidina (29-41).…”