Membrane Glycoproteins of Enveloped Viruses

Glycosylated components induced in African swine fever (ASF) virus-infected Vero cells

African swine fever (ASF) virus production was inhibited more than 100 fold by 5 mM glucosamine, 2 mM 2-deoxyglucose and 3 microM tunicamycin. ASF virus induced in Vero cells the synthesis of 19 glycosylated components of molecular weights ranging from 9K to 220K, the major ones being those of 9K, 13K, 14K, 74K and 220K. At least five of the induced glycosylated components, of molecular weights 13K, 33K, 34K, 38K and 220K, were probably virus-coded glycoproteins, as suggested by a comparative analysis of the time course of synthesis and the antigenicity of these components in extracts from [35S]methionine or [14C]glucosamine-labeled infected cells. The non-protein glycosylated components present in extracellular ASF virus particles had a cellular origin.

Resolution of two surface glycoproteins from human parainfluenza-3 virus by crossed immunoelectrophoresis

The technique of two-dimensional crossed immunoelectrophoresis (CIE) was used to resolve two glycoproteins from purified human parainfluenza type 3 virus. Virus preparations were extracted with Triton X-100 and fractionated by centrifugation in a Beckman airfuge. Two immunoprecipitates were detected by CIE in the supernatant fractions, but were not found in the pellets from extracted virus. Viral glycoproteins labeled with [35S]methionine were isolated by affinity chromatography on concanavalin A (Con A) agarose columns, resolved by CIE and detected by autoradiography. Resolution of two glycoprotein peaks from as little as 4.5 micrograms of protein from extracted virus is consistent with results from polyacrylamide gel patterns showing two unique glycoproteins with molecular weights of 48 kd and 65 kd.

Glycopeptides of murine leukemia viruses. II. Comparison of xenotropic and dual-tropic viruses

The glycosylation patterns of the gp70 glycoproteins of xenotropic and dualtropic murine leukemia virus (MuLV) were compared with those of ecotropic viruses. Ecotropic viruses contain a large glycopeptide size class designated G1 (molecular weight, approximately 5100), and such glycopeptides were not detected in xenotropic viruses grown in mink cells nor in dual-tropic viruses grown in mouse or mink lung cells. Both xenotropic and dual-tropic MuLV had glycopeptide size classes designated G2, G3, and G4 (molecular weights, approximately 2900, 2,200, and 1,500, respectively). G2 glycopeptides of xenotropic and dual-tropic MuLV were shown to be resistant to endo-beta-N-acetylglucosaminidase H, whereas G3 and G4 glycopeptides were susceptible. The relative abudance of glycopeptide G3 was increased in xenotropic and dual-tropic viruses as compared with ecotropic viruses, whereas the relative amount of G4 was decreased in xenotropic viruses. The similarity in the glycosylation patterns of a number of xenotropic and dual-tropic viruses suggests that glycosylation sites are highly conserved within the env gene products of each of these classes of viruses.

Antibody-mediated destruction of virus-infected cells

This chapter describes the effect of antibody on virus-infected cells with special reference to the human system. The destruction by antibody of the infected cells through the mediation of complement is described in detail based in considerable part on the contributions of the authors. Activation of the alternative pathway by the various infected cells is of special interest. The interesting effect of the antibody-dependent cell-mediated cytotoxicity (ADCC) system involving viral antigens in cell killing is also presented. Multiple additional topics are also covered, such as the effect of antibody on the expression of viral proteins both on the surface of the cell and intracellularly. Serum antibody, produced in response to virus infections, is of major importance in preventing the spread of infection by virtue of neutralizing free virus in extracellular fluids. Virus neutralization by antibody is enhanced by complement. Antibody binding to the surface of virus-infected cells can affect virus production and release in the absence of an effector system. Immunoglobulin (IgG) antibody can mediate the destruction of virus-infected cells in conjunction with complement or cytotoxic lymphocytes. In addition, at a conceptual level there is evidence to suggest that antibody may enhance and confer specificity on basic nonspecific humoral and cell-mediated defense mechanisms.