A3 - AAV Vectors - Capsid Engineering
120: Second Generation AAV Capsids Reprogrammed to Bind Human Transferrin Receptor are Targeted to the Brain and De-Targeted from the Liver in Human TFRC Knock-In Mice
Type: Oral Abstract Session
Presentation Details
Session Title: Breaking Barriers to the CNS via AAV Capsid Engineering
Developing vehicles that efficiently deliver genes throughout the human central nervous system (CNS) will broaden the range of treatable genetic diseases. We developed a high-throughput
in vitro screening approach to reprogram AAV9 to bind the human Transferrin Receptor (TfR1), a protein expressed on the blood-brain barrier (BBB). We showed that one TfR1-targeted capsid, BI-hTFR1, was actively transported across a human brain endothelial cell layer and achieved 40-50 times greater reporter expression in the CNS of human
TFRC knock-in mice compared to AAV9 in wild type mice after intravenous delivery. The enhanced tropism of BI-hTFR1 was CNS-specific and absent in wild type mice (Fig. 1A). Through sequence diversification, we identified a second generation capsid, BI-hTFR1.2, that was capable of transducing more than 60 percent of NeuN-positive neurons in the cortex of human
TFRC knock-in mice when dosed at 5E10 vg/mouse, while also being de-targeted from the liver (Fig. 1B). Similar to BI-hTFR1, BI-hTFR1.2 exclusively binds to human but not macaque or mouse TfR1. Using amino acid swaps between species, we pinpointed human-specific residues of TfR1 that are critical for the species-specific binding by BI-hTFR1 and BI-hTFR1.2. Importantly, there are no common human polymorphisms that would be predicted to directly impact the ability of these capsids to bind TfR1 in patients. Our work establishes these TfR1-targeting capsids as promising vectors for human CNS gene therapy.
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Figure 1. TfR1-targeted AAV capsids achieve efficient CNS-wide transgene expression in human TFRC knock-in mice. (A) BI-hTFR1 or AAV9 were intravenously injected into adult wild type C57BL/6J or
TFRC knock-in mice at 5E11 vg/animal. Representative sagittal brain section images from three weeks post-injection are shown.
(B) BI-hTFR1 or BI-hTFR1.2 were intravenously injected into adult
TFRC knock-in mice at 5E10 vg/animal (~2.5E12 vg/kg). Representative sagittal brain and liver section images from three weeks post-injection are shown.
Plain Language Summary
Viral vectors are reprogrammed to bind to a human receptor expressed on the blood brain-barrier as a way to deliver therapeutic genes into the brain.
Ken Y. Chan, Qin Huang
, Shan Lou
, Casey Keyes
, Jason Wu
, Nuria R. Botticello-Romero
, Qingxia Zheng
, Chin-Yen Lin
, Jencilin Johnston
, Allan Mills
, Pamela Brauer
, Gabrielle Clouse
, Simon Pacouret
, John W. Harvey
, Thomas Beddow
, Jenna K. Hurley
, Isabelle G. Tobey
, Megan Powell
, Catherine P. Pirtle
, Albert Chen
, Andrew J. Barry
, Fatma-Elzahraa Eid
, Yujia A. Chan
, Benjamin E. Deverman
Broad Institute of MIT and Harvard, Cambridge, MA"