title: The effects of beta-2-microglobulin on the infectivity of murine cytomegalovirus.
abstract: The role of beta-2-microglobulin (beta 2m) in murine cytomegalovirus (MCMV) infection of susceptible (H-2d) and resistant (H-2k) murine embryo fibroblasts (MEF) and peritoneal macrophages was evaluated using serum-free virus (SF-MCMV). The infectivity of SF-MCMV was significantly lower than virus propagated in serum, although the concentrations of virions were similar. Infection of cells with SF-MCMV was assessed by measuring the proportion of cells expressing viral antigens, the sizes of plaques formed in fibroblast monolayers and TCID50 titers. Infection of susceptible fibroblasts was significantly increased 1.6-4.7 fold by the addition of whole FCS, a less than 20 kDa FCS fraction, or purified human beta 2m. These supplements also significantly enhanced infection of susceptible macrophages and increased TCID50 titers by 3.5-10 fold in susceptible MEF. In relatively resistant H-2k cells, the TCID50 titer and the proportion of cells expressing viral antigens after infection with SF-MCMV were not affected by beta 2m or FCS, but plaque sizes were increased 2.5-3 fold in resistant BALB.K MEF. When human or murine beta 2m was added to infected cultures, immunogold electron microscopy revealed these proteins to be always associated extracellularly with the tegument material of disrupted multicapsid virions, but rarely with the envelope of intact virions. However, no murine beta 2m was found in association with the envelope or tegument of SF-MCMV. These relatively modest effects of beta 2m which were restricted to genetically susceptible cells, may be due to tegument-bound beta 2m facilitating infection by capsids, or the stabilisation of the conformation of Class 1 molecules by exogenous beta 2m, promoting MCMV binding to the target cell.
authors.affiliation: Department of Microbiology, University of Western Australia, Nedlands.
authors.forename: M N
authors.initials: MN
authors.lastname: Wykes
authors.forename: P
authors.initials: P
authors.lastname: Price
authors.forename: G R
authors.initials: GR
authors.lastname: Shellam
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001769:Blood; D002478:Cells, Cultured; D003587:Cytomegalovirus / Q000276:immunology / Q000472:pathogenicity* / Q000648:ultrastructure; D006183:H-2 Antigens / Q000276:immunology; D006801:Humans; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D016253:Microscopy, Immunoelectron; D001613:beta 2-Microglobulin / Q000502:physiology*
chemical_list: D006183:H-2 Antigens; D001613:beta 2-Microglobulin