Molecular Imaging and Biology

, Volume 14, Issue 2, pp 163–171

Targeting Apoptosis for Optical Imaging of Infection

Authors

    • Department of RadiologyThomas Jefferson University
  • Kaijun Zhang
    • Department of RadiologyThomas Jefferson University
  • Bishnuhari Paudyal
    • Department of RadiologyThomas Jefferson University
  • Devadhas Devakumar
    • Department of RadiologyThomas Jefferson University
  • Maria Y. Covarrubias
    • Bioimaging, Kimmel Cancer CenterThomas Jefferson University
  • Changpo Cheng
    • Department of Biochemistry Molecular BiologyThomas Jefferson University
  • Brian D. Gray
    • Molecular Targeting Technologies, Inc
  • Eric Wickstrom
    • Department of Biochemistry Molecular BiologyThomas Jefferson University
  • Koon Y. Pak
    • Molecular Targeting Technologies, Inc
Research Article

DOI: 10.1007/s11307-011-0490-6

Cite this article as:
Thakur, M., Zhang, K., Paudyal, B. et al. Mol Imaging Biol (2012) 14: 163. doi:10.1007/s11307-011-0490-6

Abstract

Purpose

Infection is ubiquitous and a major cause of morbidity and mortality. The most reliable method for localizing infection requires radiolabeling autologous white blood cells ex vivo. A compound that can be injected directly into a patient and can selectively image infectious foci will eliminate the drawbacks. The resolution of infection is associated with neutrophil apoptosis and necrosis presenting phosphatidylserine (PS) on the neutrophil outer leaflet. Targeting PS with intravenous administration of a PS-specific, near-infrared (NIR) fluorophore will permit localization of infectious foci by optical imaging.

Methods

Bacterial infection and sterile inflammation were induced in separate groups (n = 5) of mice. PS was targeted with a NIR fluorophore, PSVue®794 (2.7 pmol). Imaging was performed (ex = 730 nm, em = 830 nm) using Kodak Multispectral FX-Pro system. The contralateral normal thigh served as an individualized control. Confocal microscopy of normal and apoptotic neutrophils and bacteria confirmed PS specificity.

Results

Lesions, with a 10-s image acquisition, were unequivocally visible at 5 min post-injection. At 3 h post-injection, the lesion to background intensity ratios in the foci of infection (6.6 ± 0.2) were greater than those in inflammation (3.2 ± 0.5). Image fusions confirmed anatomical locations of the lesions. Confocal microscopy determined the fluorophore specificity for PS.

Conclusions

Targeting PS presented on the outer leaflet of apoptotic or necrotic neutrophils as well as gram-positive microorganism with PS-specific NIR fluorophore provides a sensitive means of imaging infection. Literature indicates that NIR fluorophores can be detected 7–14 cm deep in tissue. This observation together with the excellent results and the continued development of versatile imaging devices could make optical imaging a simple, specific, and rapid modality for imaging infection.

Key words

Infection imagingPSVue®794Optical imagingConfocal microscopyApoptotic neutrophils

Copyright information

© Academy of Molecular Imaging and Society for Molecular Imaging 2011