Wellington Pham

Codeletion of chromosome 1p and 19q arms in a subset of gliomas has been shown to associate with the accumulation of cystathionine in the tumor. Here, we report the analyses of cystathionine and 2‐hydroxyglutarate (2HG) in 38 biopsy‐proven glioma patients, as measured with TE 97‐ms point‐resolved spectroscopy (PRESS) at 3 T. Following the confirmation of in‐house calculated cystathionine basis signals in a phantom solution, LCModel spectral fitting was performed to decompose metabolite signals, and the millimolar concentrations of metabolites were estimated with reference to water. Cystathionine was estimated to be significantly higher in IDH mutated 1p/19q codeleted gliomas than in noncodeleted gliomas (1.4 ± 1.1 vs. 0.3 ± 0.4 mM; n = 15 and 14; p = 0.002). 2HG estimation was significantly higher in IDH‐mutant gliomas compared to IDH‐wildtype gliomas (3.7 ± 3.3 vs. 0.1 ± 0.1 mM; n = 29 and 9; p = 0.002). Using cutoff values from receiver operating characteristic curve analysis, the sensitivity and specificity of the cystathionine measures with respect to 1p/19q status were estimated to be 0.8 and 0.79 (cutoff at 0.6 mM), and those of 2HG measures with respect to IDH status were both unity (cutoff at 0.5 mM). A TE 113‐ms PRESS sequence was designed to improve detection of the cystathionine C4‐proton resonance at 2.72 ppm. Data from two glioma patients showed that cystathionine can be detected with minimal interference from the overlapping aspartate signal. 2D chemical‐shift imaging of cystathionine using the TE 113‐ms PRESS is demonstrated. Our MRS data confirm elevation of cystathionine in 1p/19q codeleted gliomas, as demonstrated in prior studies, and suggest that relatively high estimates of cystathionine may provide a biomarker of 1p/19q codeleted gliomas.

The classical amyloid cascade hypothesis postulates that the aggregation of amyloid plaques and the accumulation of intracellular hyperphosphorylated Tau tangles, together, lead to profound neuronal death. However, emerging research has demonstrated that soluble amyloid-β oligomers (SAβOs) accumulate early, prior to amyloid plaque formation. SAβOs induce memory impairment and disrupt cognitive function independent of amyloid-β plaques, and even in the absence of plaque formation. This work describes the development and characterization of a novel anti-SAβO (E3) nanobody generated from an alpaca immunized with SAβO. In-vitro assays and in-vivo studies using 5XFAD mice indicate that the fluorescein (FAM)-labeled E3 nanobody recognizes both SAβOs and amyloid-β plaques. The E3 nanobody traverses across the blood–brain barrier and binds to amyloid species in the brain of 5XFAD mice. Imaging of mouse brains reveals that SAβO and amyloid-β plaques are not only different in size, shape, and morphology, but also have a distinct spatial distribution in the brain. SAβOs are associated with neurons, while amyloid plaques reside in the extracellular matrix. The results of this study demonstrate that the SAβO nanobody can serve as a diagnostic agent with potential theragnostic applications in Alzheimer’s disease.

Several new lines of research have demonstrated that a significant number of amyloid-β peptides found in Alzheimer's disease (AD) are truncated and undergo post-translational modification by glutaminyl cyclase (QC) at the N-terminal. Notably, QC's products of Abeta-pE3 and Abeta-pE11 have been active targets for investigational drug development. This work describes the design, synthesis, characterization, and in vivo validation of a novel PET radioligand, [¹⁸F]PB0822, for targeted imaging of QC. We report herein a simplified and robust chemistry for the synthesis of the standard compound, [¹⁹F]PB0822, and the corresponding [¹⁸F]PB0822 radioligand. The PET probe was developed with 99.9% radiochemical purity, a molar activity of 965 Ci.mmol^-1, and an IC₅₀ of 56.3 nM, comparable to those of the parent PQ912 inhibitor (62.5 nM). Noninvasive PET imaging showed that the probe is distributed in the brain 5 min after intravenous injection. Further, in vivo PET imaging with [¹⁸F]PB0822 revealed that AD 5XFAD mice harbor significantly higher QC activity than WT counterparts. The data also suggested that QC activity is found across different brain regions of the tested animals.

The classical amyloid cascade hypothesis postulates that the aggregation of amyloid plaques and the accumulation of intracellular hyperphosphorylated Tau tangles, together, lead to profound neuronal death. However, emerging research has demonstrated that soluble amyloid-b oligomers (SAbOs) accumulate early, prior to amyloid plaque formation. SAbOs induce memory impairment and disrupt cognitive function independent of amyloid-b plaques, and even in the absence of plaque formation. This work describes the development and characterization of a novel anti-SAbO (E3) nanobody generated from an alpaca immunized with SAbO. In-vitro assays and in-vivo studies using 5XFAD mice indicate that the fluorescein (FAM)-labeled E3 nanobody recognizes both SAbOs and amyloid-b plaques. The E3 nanobody traverses across the blood-brain barrier and binds to amyloid species in the brain of 5XFAD mice. Imaging of mouse brains reveals that SAbO and amyloid-b plaques are not only different in size, shape, and morphology, but also have a distinct spatial distribution in the brain. SAbOs are associated with neurons, while amyloid plaques reside in the extracellular matrix. The results of this study demonstrate that the SAbO nanobody can serve as a diagnostic agent with potential theragnostic applications in Alzheimer’s disease.