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Published April 30, 2020 | Published + Supplemental Material
Journal Article Open

Positron emission tomography imaging of novel AAV capsids maps rapid brain accumulation


Adeno-associated viruses (AAVs) are typically single-stranded deoxyribonucleic acid (ssDNA) encapsulated within 25-nm protein capsids. Recently, tissue-specific AAV capsids (e.g. PHP.eB) have been shown to enhance brain delivery in rodents via the LY6A receptor on brain endothelial cells. Here, we create a non-invasive positron emission tomography (PET) methodology to track viruses. To provide the sensitivity required to track AAVs injected at picomolar levels, a unique multichelator construct labeled with a positron emitter (Cu-64, t_(1/2) = 12.7 h) is coupled to the viral capsid. We find that brain accumulation of the PHP.eB capsid 1) exceeds that reported in any previous PET study of brain uptake of targeted therapies and 2) is correlated with optical reporter gene transduction of the brain. The PHP.eB capsid brain endothelial receptor affinity is nearly 20-fold greater than that of AAV9. The results suggest that novel PET imaging techniques can be applied to inform and optimize capsid design.

Additional Information

© The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Received 31 August 2019; Accepted 31 March 2020; Published 30 April 2020. We thank Dr. James Wilson for the gift of AAV9, Dr. Hua Zhang for technical assistance in fluorescence microscopy of optically labeled AAVs, Dr. Soichiro Yamada for supporting confocal microscope time, the California Behavioral Health Center of Excellence Pilot Award, the Foundation for Angelman Syndrome Therapeutics, Dr. Siobhan Brady for vibratome usage and Yaping Lei and Dr. Alice Tarantal for technical advice on qPCR, Sarah Tom and Charles Smith in the Center for Molecular Genomic Imaging at UC Davis for PET/CT imaging assistance, Marina Raie for technical assistance and the CLOVER Center in the Beckman Institute at Caltech for producing AAVs. This work was supported by NIHCA112356, NIHEB028646, NIHUG3TR002866, NIFACADMCB-7399-H and 17IRG33420114. Data availability: The raw data files from mass spectrometer were processed using Byonic v 2.14.27 (Protein Metrics, San Carlos, CA) to identify peptides and subsequently infer proteins using the Mus musculus database from the Universal Protein Resource (UniProt, http://www.uniprot.org) along with the sequences of capsid proteins. Protein Data Bank (PDB ID:3Ux1) was used to display capsid structure. Analyzed viral protein sequence data are available in the source data. The authors declare that image and quantitative data supporting the findings of this study are available within the paper and the source data and supplementary files. The raw PET images and associated data that support the findings of this study are available from the corresponding author upon reasonable request. Author Contributions: J.W.S. and K.W.F. designed and implemented the study, produced data, and wrote the paper with significant input from V.G., J.W.S., and L.M. performed PET imaging and analysis. B.W., S.A., P.J., and M.J., performed and commented on classical in vivo qPCR studies. M.C., E.S.I., and S.T. assessed titers, performed flow cytometry, and analyzed data. S.S. performed in vitro assays of AAVs in HEK293T cells. M.B. and R.H.C. acquired and analyzed cryoEM images. N.G., N.C.F., and T.D. provided AAVs and X.D. provided X-ray capsid images and identified critical capsid peptide sequences. K.S. and R.L. at the Stanford University Mass Spectrometry core performed viral protein mass analysis. D.S. and E.S. advised on viral vector handling and in vitro cell assays, respectively. All authors discussed the results and contributed to the completion of the paper. The authors declare no competing interests.

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August 22, 2023
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