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Journal of Virology, February 2000, p. 1761-1766, Vol. 74, No. 4
Department of Preclinical Biology and
Immunology, Cell Genesys Inc., Foster City, California 94404
Received 23 July 1999/Accepted 10 November 1999
Recombinant adeno-associated virus type 2 (AAV) is a common vector
used in human gene therapy protocols. We characterized the humoral
immune response to AAV and observed that 80% of normal human subjects
have anti-AAV antibodies and that 18% have neutralizing antibodies. To
analyze the effect of neutralizing antibodies on AAV
readministration, we attempted to deliver recombinant AAV expressing
human factor IX (AAV-hFIX) intraportally into the livers of mice
which had been preexposed to AAV and shown to harbor a neutralizing antibody response. While all naive control mice
expressed hFIX following administration of AAV-hFIX, none of the mice
with preexisting immunity expressed hFIX, even after transient
immunosuppression at the time of the second administration with
anti-CD4 or anti-CD40L antibodies. This suggests that preexisting
immunity to AAV, as measured by a neutralizing antibody response,
may limit AAV-mediated gene delivery. Using human sera in an
enzyme-linked immunosorbent assay for AAV and a capsid peptide scan
library to block antibody binding, we mapped seven regions of the AAV
capsid containing immunogenic epitopes. Using pools of these peptides
to inhibit the binding of neutralizing antibodies, we have identified a
subset of six peptides which potentially reconstitute a single
neutralizing epitope. This information may allow the design of reverse
genetic approaches to circumvent the preexisting immunity that can be encountered in some individuals.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Epitope Mapping of Human Anti-Adeno-Associated Virus Type 2 Neutralizing Antibodies: Implications for Gene Therapy and
Virus Structure
*
Corresponding author. Mailing address: Cell Genesys
Inc., Department of Preclinical Biology and Immunology, 324 Lakeside
Dr., Foster City, CA 94404. Phone: (650) 425-4420. Fax: (650) 358-0645. E-mail: spatel{at}cellgenesys.com.
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