Clark M. Edson

Epstein-Barr Virus Antigens–A Challenge to Modern Biochemistry

Publisher Summary This chapter focuses on the ability of the Epstein-Barr virus (EBV) to transform human lymphocytes and role it plays in human disease. EBV has two fascinating features in its biology. The first is its ability to transform human B lymphocytes in vitro. The ability to convert small, normal, resting B lymphocytes into exponentially proliferating, transformed lymphoblasts is one of the most dramatic events that may be witnessed in tissue culture. The second is its association with human disease, in particular malignant disease. The biology of EBV has been studied primarily in terms of serologically defined antigens that can be grouped into three classes depending on the stage of the virus lytic cycle. These are—namely, transformation antigens, early antigens, and late antigens. Moreover, besides the molecular biological aspects of EB antigens, the chapter discusses its role in the immune response and the control of EBV infection.

Varicella-zoster virus envelope glycoproteins: biochemical characterization and identification in clinical material.

Varicella-zoster virus (VZV)-infected human foreskin fibroblasts synthesize viral glycoproteins of 125,000 (gp125), 118,000 (gp118), 92,000 (gp92), 63,000 (gp63), 59,000 (gp59), and 47,000 (gp47) Da. In biochemical studies, all of these VZV glycoproteins were shown to contain asparagine-linked (N-linked) oligosaccharide chains and, except for gp125 and gp47, to be sialoglycoproteins. Experiments with endo-beta-N-acetylglucosaminidase H (endo H) demonstrated that gp92 contained only complex type (endo H-resistant) N-linked glycosyl chains, while the other mature glycoproteins contained both high-mannose (endo H-sensitive) and complex-type oligosaccharides. Monoclonal antibodies recognizing multiple glycoproteins, gp63/gp125 or gp92/gp59/gp47, neutralized virus infection, suggesting the glycoproteins were important components of the virus envelope. This was confirmed for gp92/gp59/gp47 by immunoelectron microscopy, which revealed dense staining localized exclusively to the virion envelope and to the plasma membrane of virus-producer cells. The mature forms of all of these glycoproteins were also present in viral material isolated from vesicles of varicella and zoster patients, indicating that in infected individuals the viral glycoproteins are synthesized and processed in a manner similar to that in tissue culture cells.

Varicella-zoster virus gpl and herpes simplex virus gE: Phosphorylation and Fc binding

gpI, the predominant varicella-zoster virus (VZV) envelope glycoprotein, was shown to be phosphorylated exclusively on serine and threonine residues, and phosphorylated gpI was detected in isolated virions. In cells infected with herpes simplex virus type 1 (HSV-1), a related neurotropic alpha-herpesvirus, HSV gE, the homolog to VZV gpI, and HSV gB, the homolog to VZV gpII, were also phosphorylated. The phosphate on gB and gE was alkali labile and resistant to endo H, suggesting linkage to serine and/or threonine. Although VZV gpI and HSV gE share sequence homology and similar post-translational modifications, no Fc-binding activity similar to that associated with gE was detected for gpI or any of the VZV glycoproteins.

A rapid procedure for the enrichment of undenaturated, antigenically active herpes simplex virus glycoproteins

The usefulness of lentil lectin affinity chromatography for the rapid enrichment of HSV glycoproteins in an undenatured state for both research and clinical purposes was investigated. In order to compare the lentil lectin-binding characteristics and immunologic specificities of undenatured HSV-1 and HSV-2 glycoproteins, [35S]methionine-labelled extracts of virus-infected HEp-2 cells were subjected to lentil lectin affinity chromatography. Individual HSV-1 and HSV-2 glycoproteins in bound and unbound fractions were identified using monoclonal antibodies. With the exception of a portion of pgD and gD, all major viral glycoprotein species (gA, gB, gC, gD, gE and gF) and their glycosylated processive intermediates bound to lentil lectin indicating that all possess predominantly mannosyl and/or glucosyl carbohydrate moieties. Although the unbound pgD and gD species were glycosylated, no gD and only a portion of pgD bound to lentil lectin when reapplied to the column indicating that these subspecies possess alterations in factors required for efficient lectin binding. Immunoprecipitation of undenatured lectin-bound glycoproteins from infected cells using HSV-1 and HSV-2-specific rabbit and human antisera confirmed previous findings that the predominant type-specific glycoproteins of HSV-1 and HSV-2 are gC and gE/gF, respectively.