CD150 (SLAM) is a receptor for measles virus but is not involved in viral contact-mediated proliferation inhibition

Measles virus (MV) interacts with cellular receptors on the surface of peri pheral blood lymphocytes (PBL) which mediate virus binding and uptake. Simu ltaneously, the direct contact of the viral glycoproteins with the cell sur face induces a negative signal blocking progression to the S phase of the c ell cycle, resulting in a pronounced proliferation inhibition. We selected a monoclonal antibody (MAb, 5C6) directed to the surface of highly MV-susce ptible B cells (B95a), which inhibits binding to and infection of cells wit h MV wild-type and vaccine strains. By screening a retroviral cDNA library from human splenocytes (ViraPort; Stratagene) with this antibody, we cloned and identified the recognized molecule as signaling lymphocytic activation molecule (SLAM; CD150), which is identical to the MV receptor recently fou nd by H, Tatsuo et at. (Nature 406:893-897, 2000). After infection of cells , and after surface contact with MV envelope proteins, SLAM is downregulate d from the cell surface of activated PBL and cell lines, Although anti-SLAM and/or anti-CD46 antibodies block virus binding, they do not interfere wit h the contact-mediated proliferation inhibition. In addition, the cell-type -specific expression of SLAM does not correlate with the sensitivity of cel ls for proliferation inhibition. The data indicate that proliferation inhib ition induced by MV contact is independent of the presence or absence of th e virus-binding receptors SLAM and CD46.