Cover photograph (Copyright © 2008, American Society for Microbiology. All Rights Reserved.): Immunofluorescence microscopy showing expression of the vaccinia virus complement control protein (VCP) on the surface of vaccinia virus (VACV)- infected cells. Cells were infected overnight and surface stained for VCP by using a monoclonal antibody (green). Cells were counterstained with DAPI (blue) to label nuclei and analyzed using fluorescence microscopy. VCP has previously been characterized as the major protein secreted from VACV-infected cells. VCP surface expression on infected cells is due to an interaction with the VACV A56 membrane protein and functions to protect infected cells from complement-mediated lysis. (See related article on p. 4205.)