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Infect. Immun., 01 1995, 43-50, Vol 63, No. 1
M Kelleher, SF Moody, P Mirabile, AH Osborn, A Bacic and E Handman
Promastigotes of the intracellular protozoan parasite Leishmania major
invade mononuclear phagocytes by a direct interaction between the cell
surface lipophosphoglycan found on all Leishmania species and macrophage
receptors. This interaction is mediated by phosphoglycan repeats containing
oligomers of beta (1-3)Gal residues specific to L. major. We show here that
although amastigotes also use lipophosphoglycan to bind to both primary
macrophages and a cell line, this interaction is independent of the beta
(1-3)Gal residues employed by promastigotes. Binding of amastigotes to
macrophages could be blocked by intact lipophosphoglycan from L. major
amastigotes as well as by lipophosphoglycan from promastigotes of several
other Leishmania species, suggesting involvement of a conserved domain.
Binding of amastigotes to macrophages could be blocked significantly by the
monoclonal antibody WIC 108.3, directed to the lipophosphoglycan backbone.
The glycan core of lipophosphoglycan could also inhibit attachment of
amastigotes, but to a considerably lesser extent. The glycan core structure
is also present in the type 2 glycoinositolphospholipids which are
expressed on the surface of amastigotes at 100-fold-higher levels than
lipophosphoglycan. However, their inhibitory effect could not be increased
even when they were used at a 300-fold-higher concentration than
lipophosphoglycan, indicating that lipophosphoglycan is the major
macrophage-binding molecule on amastigotes of L. major. In the presence of
complement, the attachment of amastigotes to macrophages was not altered,
suggesting that lipophosphoglycan interacts directly with macrophage
receptors.
Copyright © 1995, American Society for Microbiology
Lipophosphoglycan blocks attachment of Leishmania major amastigotes to macrophages
Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Victoria, Australia.
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