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M9490425.TXT
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1994-09-19
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Document 0425
DOCN M9490425
TI Fusogenic mechanisms of enveloped-virus glycoproteins analyzed by a
novel recombinant vaccinia virus-based assay quantitating cell
fusion-dependent reporter gene activation.
DT 9411
AU Nussbaum O; Broder CC; Berger EA; Laboratory of Viral Diseases, National
Institute of Allergy and; Infectious Diseases, National Institutes of
Health, Bethesda, MD; 20892.
SO J Virol. 1994 Sep;68(9):5411-22. Unique Identifier : AIDSLINE
MED/94335053
AB The fusogenic activities of enveloped-virus glycoproteins were analyzed
by using a quantitative, sensitive, rapid, and highly versatile
recombinant vaccinia virus-based assay measuring activation of a
reporter gene upon fusion of two distinct cell populations. One
population uniformly expressed vaccinia virus-encoded viral
glycoproteins mediating specific binding and fusion activities; the
other expressed the corresponding cellular receptor(s). The cytoplasm of
one population also contained vaccinia virus-encoded bacteriophage T7
RNA polymerase; the cytoplasm of the other contained a transfected
plasmid with the Escherichia coli lacZ gene linked to the T7 promoter.
When the two populations were mixed, cell fusion resulted in activation
of the LacZ gene in the cytoplasm of the fused cells; beta-galactosidase
activity was assessed by colorimetric assay of detergent cell lysates or
by in situ staining. We applied this approach to study the human
immunodeficiency virus type 1 envelope glycoprotein (Env)-CD4
interaction. Beta-Galactosidase was detected within 1 h after cell
mixing and accumulated over the next several hours. Cell fusion
dependence was demonstrated by the strict requirement for both CD4 and
functional Env expression and by the inhibitory effects of known
fusion-blocking monoclonal antibodies and pharmacological agents.
Quantitative measurements indicated much higher sensitivity compared
with analysis of syncytium formation. The assay was used to probe
mechanisms of the cell type specificity for Env-CD4-mediated fusion. In
agreement with known restrictions, cell fusion occurred only when CD4
was expressed on a human cell type. Membrane vesicle transfer
experiments indicated that CD4 initially produced in either human or
nonhuman cells was functional when delivered to human cells, suggesting
that the fusion deficiency with nonhuman cells was not associated with
irreversible defects in CD4. We also demonstrated that the infectivity
specificities of different human immunodeficiency virus type 1 isolates
for peripheral blood lymphocytes versus continuous CD4+ cell lines were
associated with corresponding fusion selectivities of the respective
recombinant Env proteins. The assay enabled analysis of the fusogenic
activity of the fusion glycoprotein/hemagglutinin-neuraminidase of the
paramyxovirus simian virus 5. This system provides a powerful tool to
study fusion mechanisms mediated by enveloped-virus glycoproteins, as
well as to screen fusion-blocking antibodies and pharmacological agents.
DE Antigens, CD4/METABOLISM *Cell Fusion Cell Line HIV Envelope Protein
gp120/*PHYSIOLOGY HIV-1/PHYSIOLOGY HN Protein/PHYSIOLOGY
Paramyxovirus/*PHYSIOLOGY Recombinant Proteins Support, U.S. Gov't,
P.H.S. Vaccinia Virus Viral Envelope Proteins/PHYSIOLOGY Viral Fusion
Proteins/*PHYSIOLOGY JOURNAL ARTICLE
SOURCE: National Library of Medicine. NOTICE: This material may be
protected by Copyright Law (Title 17, U.S.Code).