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Journal of Virology, December 1998, p. 9544-9552, Vol. 72, No. 12
Leukocyte Immunochemistry Laboratory,
Department of Pharmacology and Molecular Sciences, Johns Hopkins
University School of Medicine, Baltimore, Maryland 21205
Received 16 July 1998/Accepted 11 September 1998
Four new monoclonal antibodies (MAbs) that inhibit human T-cell
lymphotropic virus type 1 (HTLV-1)-induced syncytium formation were
produced by immunizing BALB/c mice with HTLV-1-infected MT2 cells.
Immunoprecipitation studies and binding assays of transfected mouse
cells showed that these MAbs recognize class II major
histocompatibility complex (MHC) molecules. Previously produced
anti-class II MHC antibodies also blocked HTLV-1-induced cell fusion.
Coimmunoprecipitation and competitive MAb binding studies indicated
that class II MHC molecules and HTLV-1 envelope glycoproteins are not
associated in infected cells. Anti-MHC antibodies had no effect on
human immunodeficiency virus type 1 (HIV-1) syncytium formation by
cells coinfected with HIV-1 and HTLV-1, ruling out a generalized
disruption of cell membrane function by the antibodies. High expression
of MHC molecules suggested that steric effects of bound anti-MHC antibodies might explain their inhibition of HTLV-1 fusion. An anti-class I MHC antibody and a polyclonal antibody consisting of
several nonblocking MAbs against other molecules bound to MT2 cells at
levels similar to those of class II MHC antibodies, and they also
blocked HTLV-1 syncytium formation. Dose-response experiments showed
that inhibition of HTLV-1 syncytium formation correlated with levels of
antibody bound to the surface of infected cells. The results show that
HTLV-1 syncytium formation can be blocked by protein crowding or steric
effects caused by large numbers of immunoglobulin molecules bound to
the surface of infected cells and have implications for the structure
of the cellular HTLV-1 receptor(s).
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Syncytium-Inhibiting Monoclonal Antibodies Produced
against Human T-Cell Lymphotropic Virus Type 1-Infected Cells Recognize
Class II Major Histocompatibility Complex Molecules and Block by
Protein Crowding
*
Mailing address: Department of Pharmacology and
Molecular Sciences, Biophysics Bldg., Rm. 311, Johns Hopkins University
School of Medicine, 725 North Wolfe St., Baltimore, MD 21205. Phone: (410) 955-3017. Fax: (410) 955-1894. E-mail:
jhildret{at}jhmi.edu.
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