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J. Virol., 05 1995, 2850-2857, Vol 69, No. 5
SC Stevenson, M Rollence, B White, L Weaver and A McClelland
The adenovirus fiber protein is responsible for attachment of the virion to
cell surface receptors. The identity of the cellular receptor which
mediates binding is unknown, although there is evidence suggesting that two
distinct adenovirus receptors interact with the group C (adenovirus type 5
[Ad5]) and the group B (Ad3) adenoviruses. In order to define the
determinants of adenovirus receptor specificity, we have carried out a
series of competition binding experiments using recombinant native fiber
polypeptides from Ad5 and Ad3 and chimeric fiber proteins in which the head
domains of Ad5 and Ad3 were exchanged. Specific binding of fiber to HeLa
cell receptors was assessed with radiolabeled protein synthesized in vitro,
and by competition analysis with baculovirus-expressed fiber protein. Fiber
produced in vitro was found as both monomer and trimer, but only the
assembled trimers had receptor binding activity. Competition data support
the conclusion that Ad5 and Ad3 interact with different cellular receptors.
The Ad5 receptor distribution on several cell lines was assessed with a
fiber binding flow cytometric assay. HeLa cells were found to express high
levels of receptor, while CHO and human diploid fibroblasts did not. A
chimeric fiber containing the Ad5 fiber head domain blocked the binding of
Ad5 fiber but not Ad3 fiber. Similarly, a chimeric fiber containing the Ad3
fiber head blocked the binding of labeled Ad3 fiber but not Ad5 fiber. In
addition, the isolated Ad3 fiber head domain competed effectively with
labeled Ad3 fiber for binding to HeLa cell receptors. These results
demonstrate that the determinants of receptor binding are located in the
head domain of the fiber and that the isolated head domain is capable of
trimerization and binding to cellular receptors. Our results also show that
it is possible to change the receptor specificity of the fiber protein by
manipulation of sequences contained in the head domain. Modification or
replacement of the fiber head domain with novel ligands may permit
adenovirus vectors with new receptor specificities which could be useful
for targeted gene delivery in vivo to be engineered.
Copyright © 1995, American Society for Microbiology
Human adenovirus serotypes 3 and 5 bind to two different cellular receptors via the fiber head domain
Department of Molecular and Cell Biology, Genetic Therapy, Inc., Gaithersburg, Maryland 20878, USA.
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