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Journal of Virology, January 2001, p. 726-737, Vol. 75, No. 2
Molecular Medicine Program, Mayo Clinic and
Mayo Foundation, Rochester, Minnesota 55905
Received 12 January 2000/Accepted 13 October 2000
To better understand retroviral entry, we have
characterized the interactions between subgroup A avian leukosis virus
[ALV(A)] envelope glycoproteins and Tva, the receptor for ALV(A),
that result in receptor interference. We have recently shown that
soluble forms of the chicken and quail Tva receptor (sTva), expressed from genes delivered by retroviral vectors, block ALV(A) infection of
cultured chicken cells (~200-fold antiviral effect) and chickens (>98% of the birds were not infected). We hypothesized that
inhibition of viral replication by sTva would select virus variants
with mutations in the surface glycoprotein (SU) that altered the
binding affinity of the subgroup A SU for the sTva protein and/or
altered the normal receptor usage of the virus. Virus propagation in
the presence of quail sTva-mIgG, the quail Tva extracellular region fused to the constant region of the mouse immunoglobulin G (IgG) protein, identified viruses with three mutations in the subgroup A hr1
region of SU, E149K, Y142N, and Y142N/E149K. These mutations reduced
the binding affinity of the subgroup A envelope glycoproteins for quail
sTva-mIgG (32-, 324-, and 4,739-fold, respectively) but did not alter
their binding affinity for chicken sTva-mIgG. The ALV(A) mutants
efficiently infected cells expressing the chicken Tva receptor but were
2-fold (E149K), 10-fold (Y142N), and 600-fold (Y142N/E149K) less
efficient at infecting cells expressing the quail Tva receptor. These
mutations identify key determinants of the interaction between the
ALV(A) glycoproteins and the Tva receptor. We also conclude from these
results that, at least for the wild-type and variant ALV(A)s tested,
the receptor binding affinity was directly related to infection efficiency.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.2.726-737.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Identification of Key Residues in Subgroup A Avian Leukosis Virus
Envelope Determining Receptor Binding Affinity and Infectivity of
Cells Expressing Chicken or Quail Tva Receptor

*
Corresponding author. Mailing address: Mayo Foundation,
200 First St., SW, Rochester, MN 55905. Phone: (507) 284-8895. Fax: (507) 266-2122. E-mail: federspiel.mark{at}mayo.edu.
Present address: Van Andel Research Institute, Grand Rapids, MI 49503.
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