A (99m)Tc-labeled dual-domain cytokine ligand for imaging of inflammation

Interleukin-18 and IL-18BP in inflammatory dermatological diseases

Interleukin (IL)-18, an interferon-γ inducer, belongs to the IL-1 family of pleiotropic pro-inflammatory factors, and IL-18 binding protein (IL-18BP) is a native antagonist of IL-18 in vivo, regulating its activity. Moreover, IL-18 exerts an influential function in host innate and adaptive immunity, and IL-18BP has elevated levels of interferon-γ in diverse cells, suggesting that IL-18BP is a negative feedback inhibitor of IL-18-mediated immunity. Similar to IL-1β, the IL-18 cytokine is produced as an indolent precursor that requires further processing into an active cytokine by caspase-1 and mediating downstream signaling pathways through MyD88. IL-18 has been implicated to play a role in psoriasis, atopic dermatitis, rosacea, and bullous pemphigoid in human inflammatory skin diseases. Currently, IL-18BP is less explored in treating inflammatory skin diseases, while IL-18BP is being tested in clinical trials for other diseases. Thereby, IL-18BP is a prospective therapeutic target.

A Second-Generation Nanoluc-IL27 Fusion Cytokine for Targeted-Gene-Therapy Applications

An emerging approach in treating skeletal malignancies utilizes osteoimmunology to investigate new multifunctional immune-stimulatory agents that can simultaneously combat tumor growth and promote bone repair. We have hypothesized that cytokine Interleukin-27 (IL-27) is an excellent candidate biologic to help rebalance the prostate tumor cells and bone cell environment. In this work, we examined the proof of principle for a short, secreted luciferase (Nanoluc or Nluc) fusion with IL-27 to produce a novel cytokine-based biologic (Nluc-27), whereby we examined its efficacy in vitro in reducing prostate tumor growth and rebalancing bone cell proliferation and differentiation. This work demonstrates the targeting and anti-tumor efficacy of the Nluc-27 fusion cytokine in cancer and bone cell models. The fusion cytokine is detectable in conditioned media, and bioactive in different cell systems. This novel Nluc-27 cytokine will allow flexible incorporation of other targeting domains and may serve as flexible tool to augment IL-27′s bioactivity and reengineer its efficacy against prostate tumor or bone cells, and may prove applicable to several other cell types for targeted gene therapy applications.

Radiotracers used for the scintigraphic detection of infection and inflammation

Over the last forty years, a small group of commercial radiopharmaceuticals have found their way into routine medical use, for the diagnostic imaging of patients with infection or inflammation. These molecular radiotracers usually participate in the immune response to an antigen, by tagging leukocytes or other molecules/cells that are endogenous to the process. Currently there is an advancing effort by researchers in the preclinical domain to design and develop new agents for this application. This review discusses radiopharmaceuticals used in the nuclear medicine clinic today, as well as those potential radiotracers that exploit an organism's defence mechanisms to an infectious or inflammatory event.

Inflammation imaging of atherosclerosis in Apo-E-deficient mice using a (99m)Tc-labeled dual-domain cytokine ligand

Interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) play a critical role in initiating and accelerating atherosclerosis. This study evaluated the imaging properties of (99m)Tc-TNFR2-Fc-IL-1RA ((99m)Tc-TFI), a dual-domain cytokine radioligand that targets TNF-α and IL-1β pathways, in assessing atherosclerosis development in apolipoprotein-E-deficient (ApoE(-)(/)(-)) mice.

METHODS

The feasibility and specificity of detecting atherosclerosis with (99m)Tc-TFI SPECT imaging were investigated in ApoE(-)(/)(-) and ApoE(+)(/)(+) mice. Fifty-four ApoE(-)(/)(-) mice were fed either an atherogenic diet (AGD) or a normal diet (ND) beginning at 5 weeks of age. Eighteen Apo-E wild-type (ApoE(+)(/)(+)) mice were fed an ND. Two groups of ApoE(-)(/)(-) mice (n=12 each group) on AGD and ND were imaged three times with (99m)Tc-TFI and a high-resolution SPECT system at 20-25, 30-40, and 48-52 weeks to study the evolution of atherosclerotic plaque.

RESULTS

Focal radioactive accumulations in the aortic arch region were observed in the ApoE(-)(/)(-) mice (n=12) on AGD but not in the ApoE(+)(/)(+) mice on ND (n=10). Apo-E(-)(/)(-) mice on ND (n=11) exhibited lower radioactive uptake than ApoE(-)(/)(-) mice on AGD (P<0.05). Co-injection of an excess of cold ligand with (99m)Tc-TFI resulted in significant reduction of (99m)Tc-TFI uptake in the ApoE(-)(/)(-) mice on AGD. Longitudinal studies showed that (99m)Tc-TFI uptake in the aortas of ApoE(-)(/)(-) mice progressively increased from 20 to 48 weeks. Real-time PCR assays demonstrated that atherosclerotic aortas expressed significantly higher IL-1β and TNF-α than the aortas from wild-type controls.

CONCLUSIONS

Atherosclerotic plaques were detected by (99m)Tc-TFI imaging in ApoE(-)(/)(-) mice. (99m)Tc-TFI is promising for specific detection of inflammatory response in atherosclerotic plaques.

Characterization of 99mTc-labeled cytokine ligands for inflammation imaging via TNF and IL-1 pathways

INTRODUCTION

TNFR2-Fc and IL-1ra-Fc are recombinant cytokine ligands that target TNF and IL-1. TNFR2-Fc-IL-1ra, a dual-domain agent that incorporates both ligands, allows bifunctional binding of IL-1 receptors and TNF. This study was designed to characterize (99m)Tc-labeled forms of these ligands, (99m)Tc-IL-1ra-Fc (IF), (99m)Tc-TNFR2-Fc (TF), and (99m)Tc-TNFR2-Fc-IL-1ra (TFI), for inflammation imaging.

METHODS

The cytokine ligands were labeled with (99m)Tc by a direct approach via 2-iminothiolane (2-IT) reduction at various 2-IT/protein molar ratios. In vivo inflammation targeting studies were carried out in a mouse ear edema model created by topical application of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) on the right ear of ICR mice.

RESULTS

Radiolabeling yields increased with increasing amounts of 2-IT. When the 2-IT/protein ratio reached 1000, the radiolabeling yield was greater than 90% without significant colloid production. TPA-treated ears showed high radioligand uptake, which was clearly detected by SPECT and autoradiographic imaging. The activities (%ID/g) in the inflamed and control ears at 3h after injection were 2.76 ± 0.20 vs. 0.69 ± 0.12 for IF, 5.86 ± 0.40 vs. 2.86 ± 0.61 for TF, and 7.61 ± 0.86 vs. 1.99 ± 0.31 for TFI (P<0.05 vs. controls). TFI showed significantly higher uptake in the inflamed ears compared to TF and IF (P<0.05). Blocking study results indicated specificity of radioligand binding with decreased radioactive uptake in the inflamed ears. Western blotting and ELISA analysis further confirmed a high expression of IL-1β and TNF-α in the inflamed ears.

CONCLUSIONS

(99m)Tc-labeled cytokine ligands are a promising approach for detecting and understanding the inflammatory process. TFI may be more useful than the single-domain ligands for noninvasive detection of inflammatory sites.

Real-time detection of implant-associated neutrophil responses using a formyl peptide receptor-targeting NIR nanoprobe

Neutrophils play an important role in implant-mediated inflammation and infection. Unfortunately, current methods which monitor neutrophil activity, including enzyme measurements and histological evaluation, require many animals and cannot be used to accurately depict the dynamic cellular responses. To understand the neutrophil interactions around implant-mediated inflammation and infection it is critical to develop methods which can monitor in vivo cellular activity in real time. In this study, formyl peptide receptor (FPR)-targeting near-infrared nanoprobes were fabricated. This was accomplished by conjugating near-infrared dye with specific peptides having a high affinity to the FPRs present on activated neutrophils. The ability of FPR-targeting nanoprobes to detect and quantify activated neutrophils was assessed both in vitro and in vivo. As expected, FPR-targeting nanoprobes preferentially accumulated on activated neutrophils in vitro. Following transplantation, FPR-targeting nanoprobes preferentially accumulated at the biomaterial implantation site. Equally important, a strong relationship was observed between the extent of fluorescence intensity in vivo and the number of recruited neutrophils at the implantation site. Furthermore, FPR-targeting nanoprobes may be used to detect and quantify the number of neutrophils responding to a catheter-associated infection. The results show that FPR-targeting nanoprobes may serve as a powerful tool to monitor and measure the extent of neutrophil responses to biomaterial implants in vivo.