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J. Virol., 11 1997, 8230-8236, Vol 71, No. 11
B Labrosse, O Pleskoff, N Sol, C Jones, Y Henin and M Alizon
A triterpene derived from betulinic acid (RPR103611) blocks human
immunodeficiency virus type 1 (HIV-1) infection and fusion of CD4+ cells
with cells expressing HIV-1 envelope proteins (gp120 and gp41), suggesting
an effect on virus entry. This compound did not block infection by a
subtype D HIV-1 strain (NDK) or cell-cell fusion mediated by the NDK
envelope proteins. The genetic basis of drug resistance was therefore
addressed by testing envelope chimeras derived from NDK and a
drug-sensitive HIV-1 strain (LAI, subtype B). A drug- resistant phenotype
was observed for all chimeras bearing the ectodomain of NDK gp41, while the
origins of gp120 and of the membrane anchor and cytoplasmic domains of gp41
had no apparent role. The envelope gene of a LAI variant, fully resistant
to the antiviral effect of RPR103611, was cloned and sequenced. Its product
differed from the parental sequence at two positions in gp41, with changes
of arginine 22 to alanine (R22A) and isoleucine 84 to serine (I84S), the
gp120 being identical. In the context of LAI gp41, the I84S substitution
was sufficient for drug resistance. Therefore, in two different systems,
differences in gp41 were associated with sensitivity or resistance to
RPR103611. Modifications of gp41 can affect the quaternary structure of
gp120 and gp41 and the accessibility of gp120 to antiviral agents such as
neutralizing antibodies. However, a direct effect of RPR103611 on a gp41
target must also be envisioned, in agreement with the blocking of
apparently late steps of HIV-1 entry. This compound could be a valuable
tool for structure-function studies of gp41.
Copyright © 1997, American Society for Microbiology
Resistance to a drug blocking human immunodeficiency virus type 1 entry (RPR103611) is conferred by mutations in gp41
INSERM, Institut Cochin de Genetique Moleculaire, Paris, France.
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