Fc Receptor(s) Induced by Human Cytomegalovirus Bind Differentially with Human Immunoglobulin G Subclasses

Abstract

SUMMARYThe IgG subclass specificity of Fc receptor(s) induced on cells by infection with human cytomegalovirus (HCMV) was studied in a binding assay by using infected cells and purified iodinated IgG of various subclasses from HCMV seronegative healthy adult donors. All four human IgG subclasses bound to HCMV-infected cells, with the following relative magnitudes: IgG1 t> IgG4 > IgG2 > IgG3. The IgG subclass specificity of the Fc receptor was further analysed in an inhibition assay by using fragments prepared from purified human IgG by papain digestion, and using unlabelled subclass proteins. Fc but not Fab fragments inhibited the binding of 125I-labelled human IgG to HCMV-infected cells. The biological role of the Fc receptor in HCMV infection is discussed.

The Endoplasmic Reticulum Chaperone BiP/GRP78 Is Important in the Structure and Function of the Human Cytomegalovirus Assembly Compartment

“…We note that the antibodies that detect BiP in the perinuclear structure are rabbit polyclonal antibodies (BiPA, -S, -H, and -Y). This raises some concern that the rabbit antisera may be interacting, at least in part, with HCMV-encoded Fc receptors which have an affinity for rabbit immunoglobulin G (IgG) (28) and may cause spurious localization of IgG to the assembly compartment. However, one rabbit polyclonal antibody, BiPR, localizes BiP in the condensed cytoplasmic regions, not the perinuclear region.…”

Characterization of IgG Fc Receptors Induced by Human Cytomegalovirus

“…Human IgG was prepared by chromatography of HCMV-seronegative donor serum (as confirmed by indirect immunofluorescence assay and ELISA) on DEAE-cellulose and Protein A-Sepharose CL-4B (Pharmacia). Fc and Fab fragments of human IgG were prepared by papain digestion as described by Murayama et al (1986). Rabbit and mouse IgG were prepared by the method described above.…”

“…However, that induced by HCMV has not yet been well characterized biochemically, nor is it known whether it is a virus-encoded or cellular product. Recently we have demonstrated that the FcR induced by HCMV has subclass specificity with respect to IgG binding, and that the relative magnitude of binding is IgG1 >I IgG4 > IgG2 > IgG3 (Murayama et al, 1986). The present study was undertaken to characterize the FcR induced by HCMV in relation to that induced by HSV.…”

Identification and Expression of Human Cytomegalovirus Transcription Units Coding for Two Distinct Fcγ Receptor Homologs

“…Biochemical characterization of Fc-binding proteins (FcBPs) in HCMV-infected fibroblasts led to conflicting results, and a viral protein mediating this effect has not yet been identified (48,62,67). Alternatively, induction of a cFc␥R could account for this effect, although antibodies specific for known cFc␥Rs did not stain HCMV-infected cells (43).…”