Rapid imaging of experimental infection with technetium-99m-DTPA after anti-DTPA monoclonal antibody priming.
Antibodies accumulate nonspecifically in infectious foci due to the locally increased vascular permeability. This study describes a method of infection imaging in which 99mTc-DTPA (diethylenetriaminepentaacetic acid) is trapped at the target by a previously administered anti-DTPA monoclonal antibody. DTIn1.


METHODS
Rats with Staphylococcus aureus-infected calf muscle were injected intravenously with DTIn1. Two to 24 hr after the DTIn1 injection, 99mTc-DTPA was injected intravenously. In separate experiments, excess DTIn1 was cleared from the circulation 2 hr after injection with bovine serum albumin (BSA)-DTPA-In, galactosylated BSA-DTPA-In, goat antimouse IgG or avidin. Additionally, the effect of DTIn1 dose on 99mTc-DTPA abscess uptake was determined in a three-step protocol. The distribution of the radiolabels was studied by gamma counting of dissected tissue and gamma camera imaging.


RESULTS
Priming with DTIn1 resulted in specific retention of 99mTc-DTPA in the abscess. Such 99mTc-DTPA abscess uptake was not dependent on the interval between the DTIn1 and the 99mTc-DTPA injection: Optimal 99mTc-DTPA abscess uptake was already achieved within a 2-hr time span between the DTIn1 and DTPA injections. However, relatively high 99mTc-DTPA background was observed due to slowly clearing DTIn1-99mTc-DTPA complexes. Background reduction with various agents had a prominent effect on DTIn1 as well as 99mTc-DTPA biodistribution. The best reduction was obtained using BSA-DTPA-In. Optimal 99mTc-DTPA abscess uptake in the three-step protocol was obtained at higher DTIn1 doses (> 100 micrograms).


CONCLUSIONS
Infectious foci in a rat model can be imaged earlier with extremely low background levels after priming with DTIn1, followed by BSA-DTPA-In and imaging with 99mTc-DTPA, as compared with directly labeled IgG.
Kranenborg
M H
MH
Department of Nuclear Medicine, University Hospital Nijmegen, The Netherlands.
Oyen
W J
WJ
Corstens
F H
FH
Oosterwijk
E
E
van der Meer
J W
JW
Boerman
O C
OC
D000038:Abscess / Q000000981:diagnostic imaging*; D000818:Animals; D000911:Antibodies, Monoclonal; D002417:Cattle; D006041:Goats; D006801:Humans; D008297:Male; D016719:Radioimmunodetection / Q000379:methods*; D051381:Rats; D017208:Rats, Wistar; D012710:Serum Albumin, Bovine; D013203:Staphylococcal Infections / Q000000981:diagnostic imaging*; D016284:Technetium Tc 99m Pentetate; D014018:Tissue Distribution
D000911:Antibodies, Monoclonal; D012710:Serum Albumin, Bovine; D016284:Technetium Tc 99m Pentetate