TY - JOUR

T1 - Preclinical evaluation of potential infection-imaging probe [68Ga]Ga-DOTA-K-A9 in sterile and infectious inflammation

AU - Nielsen, Karin M.

AU - Jørgensen, Nis P.

AU - Kyneb, Majbritt H.

AU - Borghammer, Per

AU - Meyer, Rikke L.

AU - Thomsen, Trine R.

AU - Bender, Dirk

AU - Jensen, Svend B.

AU - Nielsen, Ole L.

AU - Alstrup, Aage K.O.

PY - 2018

Y1 - 2018

N2 - The development of bacteria-specific infection radiotracers is of considerable interest to improve diagnostic accuracy and enabling therapy monitoring. The aim of this study was to determine if the previously reported radiolabelled 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid (DOTA) conjugated peptide [68Ga]Ga-DOTA-K-A9 could detect a staphylococcal infection in vivo and distinguish it from aseptic inflammation. An optimized [68Ga]Ga-DOTA-K-A9 synthesis omitting the use of acetone was developed, yielding 93 ± 0.9% radiochemical purity. The in vivo infection binding specificity of [68Ga]Ga-DOTA-K-A9 was evaluated by micro positron emission tomography/magnetic resonance imaging of 15 mice with either subcutaneous Staphylococcus aureus infection or turpentine-induced inflammation and compared with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG). The scans showed that [68Ga]Ga-DOTA-K-A9 accumulated in all the infected mice at injected doses ≥3.6 MBq. However, the tracer was not found to be selective towards infection, since the [68Ga]Ga-DOTA-K-A9 also accumulated in mice with inflammation. In a concurrent in vitro binding evaluation performed with a 5-carboxytetramethylrhodamine (TAMRA) fluorescence analogue of the peptide, TAMRA-K-A9, the microscopy results suggested that TAMRA-K-A9 bound to an intracellular epitope and therefore preferentially targeted dead bacteria. Thus, the [68Ga]Ga-DOTA-K-A9 uptake observed in vivo is presumably a combination of local hyperemia, vascular leakiness and/or binding to an epitope present in dead bacteria.

AB - The development of bacteria-specific infection radiotracers is of considerable interest to improve diagnostic accuracy and enabling therapy monitoring. The aim of this study was to determine if the previously reported radiolabelled 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid (DOTA) conjugated peptide [68Ga]Ga-DOTA-K-A9 could detect a staphylococcal infection in vivo and distinguish it from aseptic inflammation. An optimized [68Ga]Ga-DOTA-K-A9 synthesis omitting the use of acetone was developed, yielding 93 ± 0.9% radiochemical purity. The in vivo infection binding specificity of [68Ga]Ga-DOTA-K-A9 was evaluated by micro positron emission tomography/magnetic resonance imaging of 15 mice with either subcutaneous Staphylococcus aureus infection or turpentine-induced inflammation and compared with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG). The scans showed that [68Ga]Ga-DOTA-K-A9 accumulated in all the infected mice at injected doses ≥3.6 MBq. However, the tracer was not found to be selective towards infection, since the [68Ga]Ga-DOTA-K-A9 also accumulated in mice with inflammation. In a concurrent in vitro binding evaluation performed with a 5-carboxytetramethylrhodamine (TAMRA) fluorescence analogue of the peptide, TAMRA-K-A9, the microscopy results suggested that TAMRA-K-A9 bound to an intracellular epitope and therefore preferentially targeted dead bacteria. Thus, the [68Ga]Ga-DOTA-K-A9 uptake observed in vivo is presumably a combination of local hyperemia, vascular leakiness and/or binding to an epitope present in dead bacteria.

KW - bacterial infection

KW - fluorescence

KW - gallium-68

KW - murine models

KW - PET

KW - S aureus

KW - [Ga]Ga-DOTA-K-A9

U2 - 10.1002/jlcr.3640

DO - 10.1002/jlcr.3640

M3 - Journal article

C2 - 29790580

AN - SCOPUS:85051436957

VL - 61

SP - 780

EP - 795

JO - Journal of Labelled Compounds and Radiopharmaceuticals

JF - Journal of Labelled Compounds and Radiopharmaceuticals

SN - 0362-4803

IS - 10

ER -