Limits...
[(18)F]FDG-6-P as a novel in vivo tool for imaging staphylococcal infections.

Mills B, Awais RO, Luckett J, Turton D, Williams P, Perkins AC, Hill PJ - EJNMMI Res (2015)

Bottom Line: Yield, purity and stability were confirmed by RP-HPLC and iTLC.Despite conclusive in vitro validation, [(18)F]FDG-6-P did not behave as predicted in vivo.The bacterial UHPT can transport hexose phosphates other than glucose, and therefore alternative sugars may show differential biodistribution and provide a means for specific bacterial detection.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Centre for Biomolecular Sciences, University of Nottingham, University Boulevard, Nottingham, NG7 2RD UK.

ABSTRACT

Background: Management of infection is a major clinical problem. Staphylococcus aureus is a Gram-positive bacterium which colonises approximately one third of the adult human population. Staphylococcal infections can be life-threatening and are frequently complicated by multi-antibiotic resistant strains including methicillin-resistant S. aureus (MRSA). Fluorodeoxyglucose ([(18)F]FDG) imaging has been used to identify infection sites; however, it is unable to distinguish between sterile inflammation and bacterial load. We have modified [(18)F]FDG by phosphorylation, producing [(18)F]FDG-6-P to facilitate specific uptake and accumulation by S. aureus through hexose phosphate transporters, which are not present in mammalian cell membranes. This approach leads to the specific uptake of the radiopharmaceutical into the bacteria and not the sites of sterile inflammation.

Methods: [(18)F]FDG-6-P was synthesised from [(18)F]FDG. Yield, purity and stability were confirmed by RP-HPLC and iTLC. The specificity of [(18)F]FDG-6-P for the bacterial universal hexose phosphate transporter (UHPT) was confirmed with S. aureus and mammalian cell assays in vitro. Whole body biodistribution and accumulation of [(18)F]FDG-6-P at the sites of bioluminescent staphylococcal infection were established in a murine foreign body infection model.

Results: In vitro validation assays demonstrated that [(18)F]FDG-6-P was stable and specifically transported into S. aureus but not mammalian cells. [(18)F]FDG-6-P was elevated at the sites of S. aureus infection in vivo compared to uninfected controls; however, the increase in signal was not significant and unexpectedly, the whole-body biodistribution of [(18)F]FDG-6-P was similar to that of [(18)F]FDG.

Conclusions: Despite conclusive in vitro validation, [(18)F]FDG-6-P did not behave as predicted in vivo. However at the site of known infection, [(18)F]FDG-6-P levels were elevated compared with uninfected controls, providing a higher signal-to-noise ratio. The bacterial UHPT can transport hexose phosphates other than glucose, and therefore alternative sugars may show differential biodistribution and provide a means for specific bacterial detection.

No MeSH data available.


Related in: MedlinePlus

Stability of [18F]FDG-6-P in the blood. Blood extracted from mice was incubated with [18F]FDG or [18F]FDG-6-P for 1 h. The blood was analysed by iTLC to determine whether any additional peaks indicating dephosphorylation of [18F]FDG-6-P. The dotted line shows the peak for the [18F]FDG-6-P standard, and the dashed line shows the peak for the [18F]FDG standards which were not incubated with blood.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4385282&req=5

Fig4: Stability of [18F]FDG-6-P in the blood. Blood extracted from mice was incubated with [18F]FDG or [18F]FDG-6-P for 1 h. The blood was analysed by iTLC to determine whether any additional peaks indicating dephosphorylation of [18F]FDG-6-P. The dotted line shows the peak for the [18F]FDG-6-P standard, and the dashed line shows the peak for the [18F]FDG standards which were not incubated with blood.

Mentions: The in vivo biodistribution of [18F]FDG-6-P was highly unexpected. In order to explore whether the [18F]FDG-6-P was being dephosphorylated to produce [18F]FDG during systemic circulation, samples of mouse blood were collected and incubated with either [18F]FDG or [18F]FDG-6-P ex vivo for 1 h. The blood was analysed by iTLC to examine the peak profiles for each of the radiopharmaceuticals (Figure 4). As anticipated, the blood incubated with [18F]FDG showed two defined peaks; a large peak consistent with intracellular [18F]FDG-6-P (which arises from phosphorylation of [18F]FDG as it passes through glucose transporters into the cell) and a smaller [18F]FDG peak (indicating that some [18F]FDG had not yet been transported into the cells). The blood incubated with [18F]FDG-6-P had only one defined peak, consistent with the [18F]FDG-6-P standard which had not been incubated with blood, indicating that [18F]FDG-6-P was not being dephosphorylated to [18F]FDG.Figure 4


[(18)F]FDG-6-P as a novel in vivo tool for imaging staphylococcal infections.

Mills B, Awais RO, Luckett J, Turton D, Williams P, Perkins AC, Hill PJ - EJNMMI Res (2015)

Stability of [18F]FDG-6-P in the blood. Blood extracted from mice was incubated with [18F]FDG or [18F]FDG-6-P for 1 h. The blood was analysed by iTLC to determine whether any additional peaks indicating dephosphorylation of [18F]FDG-6-P. The dotted line shows the peak for the [18F]FDG-6-P standard, and the dashed line shows the peak for the [18F]FDG standards which were not incubated with blood.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385282&req=5

Fig4: Stability of [18F]FDG-6-P in the blood. Blood extracted from mice was incubated with [18F]FDG or [18F]FDG-6-P for 1 h. The blood was analysed by iTLC to determine whether any additional peaks indicating dephosphorylation of [18F]FDG-6-P. The dotted line shows the peak for the [18F]FDG-6-P standard, and the dashed line shows the peak for the [18F]FDG standards which were not incubated with blood.
Mentions: The in vivo biodistribution of [18F]FDG-6-P was highly unexpected. In order to explore whether the [18F]FDG-6-P was being dephosphorylated to produce [18F]FDG during systemic circulation, samples of mouse blood were collected and incubated with either [18F]FDG or [18F]FDG-6-P ex vivo for 1 h. The blood was analysed by iTLC to examine the peak profiles for each of the radiopharmaceuticals (Figure 4). As anticipated, the blood incubated with [18F]FDG showed two defined peaks; a large peak consistent with intracellular [18F]FDG-6-P (which arises from phosphorylation of [18F]FDG as it passes through glucose transporters into the cell) and a smaller [18F]FDG peak (indicating that some [18F]FDG had not yet been transported into the cells). The blood incubated with [18F]FDG-6-P had only one defined peak, consistent with the [18F]FDG-6-P standard which had not been incubated with blood, indicating that [18F]FDG-6-P was not being dephosphorylated to [18F]FDG.Figure 4

Bottom Line: Yield, purity and stability were confirmed by RP-HPLC and iTLC.Despite conclusive in vitro validation, [(18)F]FDG-6-P did not behave as predicted in vivo.The bacterial UHPT can transport hexose phosphates other than glucose, and therefore alternative sugars may show differential biodistribution and provide a means for specific bacterial detection.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Centre for Biomolecular Sciences, University of Nottingham, University Boulevard, Nottingham, NG7 2RD UK.

ABSTRACT

Background: Management of infection is a major clinical problem. Staphylococcus aureus is a Gram-positive bacterium which colonises approximately one third of the adult human population. Staphylococcal infections can be life-threatening and are frequently complicated by multi-antibiotic resistant strains including methicillin-resistant S. aureus (MRSA). Fluorodeoxyglucose ([(18)F]FDG) imaging has been used to identify infection sites; however, it is unable to distinguish between sterile inflammation and bacterial load. We have modified [(18)F]FDG by phosphorylation, producing [(18)F]FDG-6-P to facilitate specific uptake and accumulation by S. aureus through hexose phosphate transporters, which are not present in mammalian cell membranes. This approach leads to the specific uptake of the radiopharmaceutical into the bacteria and not the sites of sterile inflammation.

Methods: [(18)F]FDG-6-P was synthesised from [(18)F]FDG. Yield, purity and stability were confirmed by RP-HPLC and iTLC. The specificity of [(18)F]FDG-6-P for the bacterial universal hexose phosphate transporter (UHPT) was confirmed with S. aureus and mammalian cell assays in vitro. Whole body biodistribution and accumulation of [(18)F]FDG-6-P at the sites of bioluminescent staphylococcal infection were established in a murine foreign body infection model.

Results: In vitro validation assays demonstrated that [(18)F]FDG-6-P was stable and specifically transported into S. aureus but not mammalian cells. [(18)F]FDG-6-P was elevated at the sites of S. aureus infection in vivo compared to uninfected controls; however, the increase in signal was not significant and unexpectedly, the whole-body biodistribution of [(18)F]FDG-6-P was similar to that of [(18)F]FDG.

Conclusions: Despite conclusive in vitro validation, [(18)F]FDG-6-P did not behave as predicted in vivo. However at the site of known infection, [(18)F]FDG-6-P levels were elevated compared with uninfected controls, providing a higher signal-to-noise ratio. The bacterial UHPT can transport hexose phosphates other than glucose, and therefore alternative sugars may show differential biodistribution and provide a means for specific bacterial detection.

No MeSH data available.


Related in: MedlinePlus