Article ; Online: Selection of single domain anti-transferrin receptor antibodies for blood-brain barrier transcytosis using a neurotensin based assay and histological assessment of target engagement in a mouse model of Alzheimer's related amyloid-beta pathology.
2022 Volume 17, Issue 10, Page(s) e0276107
Abstract: The blood-brain barrier (BBB) presents a major obstacle in developing specific diagnostic imaging agents for many neurological disorders. In this study we aimed to generate single domain anti-mouse transferrin receptor antibodies (anti-mTfR VHHs) to ... ...
| Abstract | The blood-brain barrier (BBB) presents a major obstacle in developing specific diagnostic imaging agents for many neurological disorders. In this study we aimed to generate single domain anti-mouse transferrin receptor antibodies (anti-mTfR VHHs) to mediate BBB transcytosis as components of novel MRI molecular contrast imaging agents. Anti-mTfR VHHs were produced by immunizing a llama with mTfR, generation of a VHH phage display library, immunopanning, and in vitro characterization of candidates. Site directed mutagenesis was used to generate additional variants. VHH fusions with neurotensin (NT) allowed rapid, hypothermia-based screening for VHH-mediated BBB transcytosis in wild-type mice. One anti-mTfR VHH variant was fused with an anti-amyloid-beta (Aβ) VHH dimer and labeled with fluorescent dye for direct assessment of in vivo target engagement in a mouse model of AD-related Aβ plaque pathology. An anti-mTfR VHH called M1 and variants had binding affinities to mTfR of <1nM to 1.52nM. The affinity of the VHH binding to mTfR correlated with the efficiency of the VHH-NT induced hypothermia effects after intravenous injection of 600 nmol/kg body weight, ranging from undetectable for nonbinding mutants to -6°C for the best mutants. The anti-mTfR VHH variant M1P96H with the strongest hypothermia effect was fused to the anti-Aβ VHH dimer and labeled with Alexa647; the dye-labeled VHH fusion construct still bound both mTfR and Aβ plaques at concentrations as low as 0.22 nM. However, after intravenous injection at 600 nmol/kg body weight into APP/PS1 transgenic mice, there was no detectible labeling of plaques above control levels. Thus, NT-induced hypothermia did not correlate with direct target engagement in cortex, likely because the concentration required for NT-induced hypothermia was lower than the concentration required to produce in situ labeling. These findings reveal an important dissociation between NT-induced hypothermia, presumably mediated by hypothalamus, and direct engagement with Aβ-plaques in cortex. Additional methods to assess anti-mTfR VHH BBB transcytosis will need to be developed for anti-mTfR VHH screening and the development of novel MRI molecular contrast agents. |
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| MeSH term(s) | Animals ; Mice ; Blood-Brain Barrier/metabolism ; Neurotensin/metabolism ; Alzheimer Disease/metabolism ; Contrast Media/metabolism ; Hypothermia/metabolism ; Fluorescent Dyes/metabolism ; Brain/metabolism ; Amyloid beta-Peptides/metabolism ; Plaque, Amyloid/pathology ; Mice, Transgenic ; Disease Models, Animal ; Camelids, New World ; Transcytosis ; Body Weight |
| Chemical Substances | Neurotensin (39379-15-2) ; Contrast Media ; Fluorescent Dyes ; Amyloid beta-Peptides |
| Language | English |
| Publishing date | 2022-10-18 |
| Publishing country | United States |
| Document type | Journal Article ; Research Support, N.I.H., Intramural ; Research Support, U.S. Gov't, Non-P.H.S. |
| ZDB-ID | 2267670-3 |
| ISSN | 1932-6203 ; 1932-6203 |
| ISSN (online) | 1932-6203 |
| ISSN | 1932-6203 |
| DOI | 10.1371/journal.pone.0276107 |
| Database | MEDical Literature Analysis and Retrieval System OnLINE |
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