Lennart Well

Molecular imaging of tumors with nanobodies and antibodies: Timing and dosage are crucial factors for improved in vivo detection

The utility of nanobodies and conventional antibodies for in vivo imaging is well known, but optimum dosing and timing schedules for one versus the other have not been established. We aimed to improve specific tumor imaging in vivo with nanobodies and conventional antibodies using near-infrared fluorescence (NIRF) imaging. We used ARTC2 expressed on lymphoma cells as a model target antigen. ARTC2-specific nanobody s+16a and conventional antibody Nika102 were labeled with NIRF-dye AF680. In vivo NIRF-imaging of ARTC2-positive and ARTC2-negative xenografts was performed over 24 h post-injection of 5, 10, 25, or 50 µg of each conjugate. Specific target-binding and tissue-penetration were verified by NIRF imaging ex vivo, flow cytometry and fluorescence microscopy. NIRF-imaging of s+16a(680) in vivo revealed a six times faster tumor accumulation than of Nika102(680). Using 50 µg of s+16a(680) increased the specific signals of ARTC2-positive tumors without increasing background signals, allowing a tumor-to-background (T/B) ratio of 12.4 ± 4.2 within 6 h post-injection. Fifty micrograms of Nika102(680) increased specific signals of ARTC2-positive tumors but also of ARTC2-negative tumors and background, thereby limiting the T/B ratio to 6.1 ± 2.0. Ten micrograms of Nika102(680) only slightly reduced specific tumor signals but dramatically reduced background signals. Ex vivo analyses confirmed a faster and deeper tumor penetration with s+16a(680). Using nanobody s+16a allowed same-day imaging with a high T/B ratio, whereas antibody Nika102 gave optimal imaging results only 24 h post injection. Nanobody s+16a required a high dose, whereas antibody Nika102 had the best T/B-ratio at a low dose. Therefore, timing and dosage should be addressed when comparing nanobodies and conventional antibodies for molecular imaging purposes.

Transgenic overexpression of toxin-related ecto-ADP-ribosyltransferase ART2.2 sensitizes T cells but not B cells to NAD-induced cell death ☆

T cells constitutively express low amounts of a toxin-related ADP-ribosylating ecto-enzyme, ART2.2. In inflammatory settings, cells release NAD, the substrate for ART2.2. The ART2.2 catalyzed ADP-ribosylation of cell surface proteins induces cell death. However, the low expression levels of ART2.2 have hampered analysis of ART2.2 in physiological settings. Here we report the generation of transgenic mice over-expressing ART2.2 under the control of the H2K promoter and Igμ enhancer. ART2.2 transgenic mice were healthy and fertile and exhibited normal development of the major lymphocyte subsets. Most T cells and a small subpopulation of B cells from transgenic mice showed more than 10-fold higher levels of ART2.2 expression than their wild-type counterparts. Exposure of ART2.2-transgenic T cells to low, submicromolar concentrations of NAD caused cell membrane alterations including uptake of propidium iodide, externalization of phosphatidylserine, and shedding of CD62L, while ART2.2-transgenic B cells were resistant to NAD. The ART2.2-overexpressing animals described here confirm that ART2.2 is an essential component for the regulation of T-cell functions by extracellular NAD and provide a useful tool to further elucidate the function of ART2.2 in vivo.

Transient Severe Motion Artifact Related to Gadoxetate Disodium-Enhanced Liver MRI: Frequency and Risk Evaluation at a German Institution

Purpose Varying frequencies (5 - 18 %) of contrast-related transient severe motion (TSM) imaging artifacts during gadoxetate disodium-enhanced arterial phase liver MRI have been reported. Since previous reports originated from the United States and Japan, we aimed to determine the frequency of TSM at a German institution and to correlate it with potential risk factors and previously published results. Materials and Methods Two age- and sex-matched groups were retrospectively selected (gadoxetate disodium n = 89; gadobenate dimeglumine n = 89) from dynamic contrast-enhanced MRI examinations in a single center. Respiratory motion-related artifacts in non-enhanced and dynamic phases were assessed independently by two readers blinded to contrast agents on a 4-point scale. Scores of ≥ 3 were considered as severe motion artifacts. Severe motion artifacts in arterial phases were considered as TSM if scores in all other phases were < 3. Potential risk factors for TSM were evaluated via logistic regression analysis. Results For gadoxetate disodium, the mean score for respiratory motion artifacts was significantly higher in the arterial phase (2.2 ± 0.9) compared to all other phases (1.6 ± 0.7) (p < 0.05). The frequency of TSM was significantly higher with gadoxetate disodium (n = 19; 21.1 %) than with gadobenate dimeglumine (n = 1; 1.1 %) (p < 0.001). The frequency of TSM at our institution is similar to some, but not all previously published findings. Logistic regression analysis did not show any significant correlation between TSM and risk factors (all p > 0.05). Conclusion We revealed a high frequency of TSM after injection of gadoxetate disodium at a German institution, substantiating the importance of a diagnosis-limiting phenomenon that so far has only been reported from the United States and Japan. In accordance with previous studies, we did not identify associated risk factors for TSM. Key Points:  · Gadoxetate disodium causes TSM in a relevant number of patients.. · The frequency of TSM is similar between the USA, Japan and Germany.. · To date, no validated risk factors for TSM could be identified.. Citation Format · Well L, Rausch VH, Adam G et al. Transient Severe Motion Artifact Related to Gadoxetate Disodium-Enhanced Liver MRI: Frequency and Risk Evaluation at a German Institution. Fortschr Röntgenstr 2017; 189: 651 - 660.

Prediction of the estimated 5-year risk of sudden cardiac death and syncope or non-sustained ventricular tachycardia in patients with hypertrophic cardiomyopathy using late gadolinium enhancement and extracellular volume CMR

AbstractObjectivesTo evaluate the ability of late gadolinium enhancement (LGE) and mapping cardiac magnetic resonance (CMR) including native T1 and global extracellular volume (ECV) to identify hypertrophic cardiomyopathy (HCM) patients at risk for sudden cardiac death (SCD) and to predict syncope or non-sustained ventricular tachycardia (VT).MethodsA 1.5-T CMR was performed in 73 HCM patients and 16 controls. LGE size was quantified using the 3SD, 5SD and full width at half maximum (FWHM) method. T1 and ECV maps were generated by a 3(3)5 modified Look-Locker inversion recovery sequence. Receiver-operating curve analysis evaluated the best parameter to identify patients with increased SCD risk ≥4% and patients with syncope or non-sustained VT.ResultsGlobal ECV was the best predictor of SCD risk with an area under the curve (AUC) of 0.83. LGE size was significantly inferior to global ECV with an AUC of 0.68, 0.70 and 0.70 (all P < 0.05) for 3SD-, 5SD- and FWHM-LGE, respectively. Combined use of the SCD risk score and global ECV significantly improved the diagnostic accuracy to identify HCM patients with syncope or non-sustained VT.ConclusionsCombined use of the SCD risk score and global ECV has the potential to improve HCM patient selection, benefiting most implantable cardioverter defibrillators.Key Points• Global ECV identified the best HCM patients with increased SCD risk. • Global ECV performed equally well compared to a SCD risk score. • Combined use of the SCD risk score and global ECV improved test accuracy. • Combined use potentially improves selection of HCM patients for ICD implantation.

Comparison of global extracellular volume (ECV) and late gadolinium enhancement (LGE) to predict the estimated 5 year risk of sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM)

University Medical Center Hamburg-Eppendorf, Hamburg, Germany Full list of author information is available at the end of the article Figure 1 Correlation of global ECV (R = 0.68, p < 0.01) and global LGE with the SCD Risk Score (R = 0.39, p = 0.08). Dashed lines define a 95% confidence interval. Continuous line represents the fitting line. Avanesov et al. Journal of Cardiovascular Magnetic Resonance 2016, 18(Suppl 1):P127 http://www.jcmr-online.com/content/18/S1/P127

Effects on blood pressure, cardiac mass and function after renal denervation in patients with resistant hypertension

Background In recent years, catheter-based renal denervation (RDN) has been investigated as a promising strategy in the treatment of resistant hypertension. Due to a reduction of whole body sympathetic activity, additional benefits on cardiac adaptation have been proposed. The purpose of this study was to investigate the effect of RDN on blood pressure (BP) as well as cardiac mass and function via cardiac magnetic resonance imaging (CMRI).