Induction of the measles virus receptor SLAM (CD150) on monocytes

Wild-type strains of measles virus (MV) isolated in B95a cells use the sign alling lymphocyte activation molecule (SLAM; also known as CD1 50) as a cel lular receptor, whereas the Edmonston strain and its derivative vaccine str ains can use both SLAM and the ubiquitously expressed CD46 as receptors. Am ong the major target cells for MV, lymphocytes and dendritic cells are know n to express SLAM after activation, but monocytes have been reported to be SLAM-negative. In this study, SLAM expression on monocytes was examined und er different conditions. When freshly isolated from the peripheral blood, m onocytes did not express SLAM on the cell surface. However, monocytes becam e SLAM-positive after incubation with phytohaemagglutinin, bacterial lipopo lysaccharide or MV. Anti-SLAM monoclonal antibodies efficiently blocked inf ection of activated monocytes with a wild-type strain of MV. These results indicate that SLAM is readily induced and acts as a monocyte receptor for M V.