Journal of Virology, August 2001, p. 7351-7361, Vol. 75, No. 16
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.16.7351-7361.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
The Leukocyte Immunochemistry Laboratory, Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland
Received 7 September 2000/Accepted 4 May 2001
We have previously shown that erythroleukemia cells
(K562) transfected with vascular adhesion molecule 1 (VCAM-1) are
susceptible to human T-cell leukemia virus type 1 (HTLV-1)-induced
syncytium formation. Since expression of VCAM-1 alone is not sufficient to render cells susceptible to HTLV-1 fusion, K562 cells appear to
express a second molecule critical for HTLV-induced syncytium formation. By immunizing mice with K562 cells, we have isolated four
monoclonal antibodies (MAbs), K5.M1, K5.M2, K5.M3, and K5.M4, that
inhibit HTLV-induced syncytium formation between infected MT2 cells and
susceptible K562/VCAM1 cells. These MAbs recognize distinct proteins on
the surface of cells as determined by cell phenotyping,
immunoprecipitation, and Western blot analysis. Since three of the
proteins recognized by the MAbs appear to be GPI linked, we isolated
lipid rafts and determined by immunoblot analysis that all four MAbs
recognize proteins that sort entirely or in large part to lipid rafts.
Dispersion of lipid rafts on the cells by cholesterol depletion with
-cyclodextrin resulted in inhibition of syncytium formation, and
this effect was not seen when the
-cyclodextrin was preloaded with
cholesterol before treating the cells. The results of these studies
suggest that lipid rafts may play an important role in HTLV-1 syncytium formation.
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