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Imaging of bacterial infections with 99mTc-labeled human neutrophil peptide-1
M M Welling1, P H Nibbering, A Paulusma-Annema
1Department of Radiology, Leiden University Medical Center, The Netherlands.
Unlabelled:
This study was undertaken to evaluate whether 99mTc-labeled human neutrophil peptide (HNP)-1 can be used as a tracer for rapid visualization of bacterial infections.
Methods:
Mice were injected intramuscularly with 1 million Staphylococcus aureus or Klebsiella pneumoniae organisms and 5 min later were injected intravenously with 0.4 microg (0.8 MBq) 99mTc-HNP-1. At various intervals, detailed information about clearance and accumulation of this tracer at sites of infection and in various organs was obtained by scintigraphy. 99mTc-labeled immunoglobulin G (IgG), an established marker of infection and inflammation, was used for comparison.
Results:
After injection into S. aureus- or K. pneumoniae-injected mice, 99mTC-HNP-1 was rapidly removed from the circulation, mainly through the kidneys and bladder, with half-lives of 170 and 55 min, respectively. Similar half-lives were observed for 99mTc-IgG in these animals. Visualization of foci with S. aureus or K. pneumoniae, as indicated by a ratio of 1.3 or higher between the targeted thigh muscle (containing bacteria) and the nontargeted (contralateral) thigh muscle (T/NT), was already achieved 5 min after injection of 99mTc-HNP-1. Similar T/NTs for 99mTc-IgG were obtained 4 h after injection of the tracer, indicating that imaging of foci of bacteria with 99mTc-HNP-1 is much faster than with 99mTc-IgG. To obtain insight into factors that contribute to accumulation of 99mTc-HNP-1 at sites of infection, the binding of this tracer to bacteria and leukocytes was assessed using a peritoneal infection model. Binding of 99mTC-HNP-1 to bacteria was approximately 1000 times higher than binding to leukocytes. Although the number of bacteria in the peritoneum was 1000-fold lower than the number of leukocytes, a significant correlation between binding of 99mTc-HNP-1 to bacteria on the one hand and accumulation of tracer on the other was still found, in contrast to 99mTc-IgG.
Conclusion:
99mTc-HNP-1 allows rapid visualization of bacterial infections. Binding of this tracer to bacteria most likely contributes significantly to the accumulation of 99mTc-HNP-1 at sites of infection.
Insights
Technetium-99m-labeled human neutrophil peptide (99mTc-HNP)-1 enables rapid visualization of bacterial infections. This tracer demonstrates significantly higher binding to bacteria than to leukocytes, facilitating quicker infection imaging compared to 99mTc-IgG.
Area of Science:
- Nuclear medicine
- Infectious disease imaging
- Biomolecular imaging
Background:
- Bacterial infections pose a significant health challenge, necessitating effective diagnostic tools.
- Current imaging agents for infection detection can be slow, impacting timely treatment.
- Human neutrophil peptide (HNP)-1 is a promising candidate for infection localization.
Purpose of the Study:
- To evaluate the efficacy of 99mTc-labeled HNP-1 as a rapid imaging tracer for bacterial infections.
- To compare the performance of 99mTc-HNP-1 with a standard imaging agent, 99mTc-labeled immunoglobulin G (IgG).
Main Methods:
- Bacterial infections were induced in mice using Staphylococcus aureus or Klebsiella pneumoniae.
- Mice were intravenously injected with 99mTc-HNP-1 and imaged using scintigraphy at various intervals.
- Binding affinity of 99mTc-HNP-1 to bacteria and leukocytes was assessed in a peritoneal infection model.
Main Results:
- 99mTc-HNP-1 demonstrated rapid clearance from circulation, primarily via the kidneys and bladder.
- Visualization of bacterial infection foci was achieved as early as 5 minutes post-injection, with high target-to-non-target ratios.
- 99mTc-HNP-1 exhibited significantly higher binding affinity to bacteria (approximately 1000-fold) compared to leukocytes.
Conclusions:
- 99mTc-HNP-1 is a highly effective tracer for the rapid visualization of bacterial infections.
- The strong binding of 99mTc-HNP-1 to bacteria is a key factor in its efficient accumulation at infection sites.
- This tracer offers a significant advantage in speed over established agents like 99mTc-IgG for infection imaging.