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J. Virol., May 1995, 2801-2810, Vol 69, No. 5
HR Choe and J Sodroski
Human immunodeficiency virus (HIV-1) was adapted to replicate efficiently
in cells expressing an altered form of the CD4 viral receptor. The mutant
CD4 (46 K/D) contained a single amino acid change (lysine 46 to aspartic
acid) in the CDR2 loop of domain 1, which results in a 15-fold reduction in
affinity for the viral gp120 glycoprotein. The ability of the adapted virus
to replicate in CD4 46 K/D-expressing cells was independently enhanced by
single amino acid changes in the V2 variable loop, the V3 variable loop,
and the fourth conserved (C4) region of the gp120 glycoprotein.
Combinations of these amino acids in the same envelope glycoprotein
resulted in additive enhancement of virus replication in cells expressing
the CD4 46 K/D molecule. In cells expressing the wild-type CD4
glycoproteins, the same V2 and V3 residue changes also increased the
efficiency of replication of a virus exhibiting decreased receptor-binding
ability due to an amino acid change (aspartic acid 368 to glutamic acid) in
the gp120 glycoprotein. In neither instance did the adaptive changes
restore the binding ability of the monomeric gp120 glycoprotein or the
oligomeric envelope glycoprotein complex for the mutant or wild-type CD4
glycoproteins, respectively. Thus, particular conformations of the gp120 V2
and V3 variable loops and of the C4 region allow postreceptor binding
events in the membrane fusion process to occur in the context of less than
optimal receptor binding. These results suggest that the fusion-related
functions of the V2, V3, and C4 regions of gp120 are modulated by CD4
binding.
Copyright © 1995, American Society for Microbiology
Adaptation of human immunodeficiency virus type 1 to cells expressing a binding-deficient CD4 mutant (lysine 46 to aspartic acid)
Division of Human Retrovirology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
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