B. Chesebro et al., MAPPING OF INDEPENDENT V3 ENVELOPE DETERMINANTS OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 MACROPHAGE TROPISM AND SYNCYTIUM FORMATION IN LYMPHOCYTES, Journal of virology, 70(12), 1996, pp. 9055-9059
The V3 region of the human immunodeficiency virus type 1 (HIV-1) envel
ope protein is known to have a major influence on macrophage tropism a
s well as the ability to cause syncytium formation or fusion in CD4-po
sitive lymphocyte cultures. Using infectious molecular HIV-1 clones, a
series of mutant clones was created which allowed detailed mapping of
V3 amino acid positions involved in these properties. In these experi
ments the non-syncytium-inducing phenotype in T cells did not always c
orrelate with macrophage tropism. Macrophage tropism appeared to depen
d on the presence of certain combinations of amino acids at five speci
fic positions within and just outside of the V3 loop itself, whereas s
yncytium formation in lymphocytes was influenced by substitution of pa
rticular residues at two to four positions within V3. In most cases, d
ifferent V3 amino acid positions were found to independently influence
macrophage tropism and syncytium formation in T cells and position 13
was the only V3 location which appeared to simultaneously influence b
oth macrophage tropism and syncytium formation in lymphocytes.