Journal of Virology, May 2000, p. 4433-4440, Vol. 74, No. 9
Department of Cancer Immunology and AIDS,
Dana-Farber Cancer Institute, Department of Pathology, Harvard
Medical School,1 and Department of
Immunology and Infectious Diseases, Harvard School of Public
Health,2 Boston, Massachusetts 02115
Received 8 October 1999/Accepted 8 February 2000
Changes in the envelope glycoprotein ectodomains of a nonpathogenic
simian-human immunodeficiency virus (SHIV-89.6) that was serially
passaged in vivo have been shown to be responsible for the increased
pathogenicity of the resulting virus, SHIV-KB9 (G. B. Karlsson, et
al., J. Exp. Med. 188:1159-1171, 1998). The 12 amino acid changes in
the envelope glycoprotein ectodomains resulted in increased chemokine
receptor-binding and syncytium-forming abilities. Here we identify the
envelope glycoprotein determinants of these properties. A single amino
acid change in the gp120 third variable (V3) loop was both necessary
and sufficient for the observed increase in the binding of the SHIV-KB9
gp120 glycoprotein to the CCR5 chemokine receptor. The increased
syncytium-forming ability of SHIV-KB9 involved, in addition to the V3
loop change, changes in the second conserved (C2) region of gp120
(residue 225) and in the gp41 ectodomain (residues 564 and 567). The C2
and gp41 ectodomain changes influenced syncytium formation in a
cooperative manner. Changes in the V1/V2 gp120 variable loops exerted a
negative effect on syncytium formation and chemokine receptor binding, supporting a previously described role of these changes in immune evasion. The definition of the passage-associated changes that determine the efficiency of chemokine receptor binding and membrane fusogenicity will allow evaluation of the contribution of these properties to in vivo CD4-positive lymphocyte depletion.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Envelope Glycoprotein Determinants of Increased
Fusogenicity in a Pathogenic Simian-Human Immunodeficiency Virus
(SHIV-KB9) Passaged In Vivo
*
Corresponding author. Mailing address: JFB824,
Dana-Farber Cancer Institute, 44 Binney St., Boston, MA 02115. Phone:
(617) 632-3371. Fax: (617) 632-4338. E-mail:
joseph_sodroski{at}dfci.harvard.edu.
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