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Journal of Virology, August 2001, p. 6841-6849, Vol. 75, No. 15
Division of Human Biology, Fred Hutchinson
Cancer Research Center,1 and Program in
Molecular and Cellular Biology3 and
Department of Microbiology,4 University
of Washington, Seattle, Washington, and Laboratory of Cell
Biology, National Institute of Mental Health, Bethesda,
Maryland2
Received 11 December 2000/Accepted 4 May 2001
The retroviral vector systems that are in common use for gene
therapy are designed to infect cells expressing either of two widely
expressed phosphate transporter proteins, Pit1 or Pit2. Subgroup B
feline leukemia viruses (FeLV-Bs) use the gibbon ape leukemia virus
receptor, Pit1, as a receptor for entry. Our previous studies showed
that some chimeric envelope proteins encoding portions of FeLV-B could
also enter cells by using a related receptor protein, Pit2, which
serves as the amphotropic murine leukemia virus receptor (S. Boomer, M. Eiden, C. C. Burns, and J. Overbaugh, J. Virol. 71:8116-8123,
1997). Here we show that an arginine at position 73 within variable
region A (VRA) of the FeLV-B envelope surface unit (SU) is necessary
for viral entry into cells via the human Pit2 receptor. However,
C-terminal SU sequences have a dominant effect in determining human
Pit2 entry, even though this portion of the protein is outside known
receptor binding domains. This suggests that a combination of specific
VRA sequences and C-terminal sequences may influence interactions
between FeLV-B SU and the human Pit2 receptor. Binding studies suggest
that the C-terminal sequences may affect a postbinding step in viral
entry via the Pit2 receptor, although in all cases, binding of FeLV-B
SU to human Pit2 was weak. In contrast, neither the arginine 73 nor specific C-terminal sequences are required for efficient binding or
infection with Pit1. Taken together, these data suggest that different
residues in SU may interact with these two receptors. The specific
FeLV-Bs described here, which can enter cells using either human Pit
receptor, may be useful as envelope pseudotypes for viruses used in
gene therapy.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.15.6841-6849.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Identification of Envelope Determinants of Feline
Leukemia Virus Subgroup B That Permit Infection and Gene Transfer to
Cells Expressing Human Pit1 or Pit2
*
Corresponding author. Mailing address: Division of
Human Biology, Fred Hutchinson Cancer Center, 1100 Fairview Ave. N.,
C3-168, Seattle, WA 98109-1024. Phone: (206) 667-3524. Fax: (206)
667-1535. E-mail: joverbau{at}fhcrc.org.
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