Characterization of domains of herpes simplex virus type 1 glycoprotein E involved in Fc binding activity for immunoglobulin G aggregates

Abstract

Herpes simplex virus type 1 glycoproteins gE and gI form receptors for the Fc domain of immunoglobulin G (IgG) which are expressed on the surface of infected cells and on the virion envelope and which protect the virus from immune attack. Glycoprotein gE-1 is a low-affinity Fc receptor (FcR) that binds IgG aggregates, while gE-1 and gI-1 form a complex which serves as a higher-affinity FcR capable of binding IgG monomers. In this study, we describe two approaches used to map an Fc binding domain on gE-1 for IgG aggregates. First, we constructed nine plasmids encoding gE-1/gD-i fusions proteins, each containing a large gE-1 peptide inserted into the ectodomain of gD-1. Fusion proteins were tested for FcR activity with IgG-sensitized erythrocytes in a rosetting assay. Three of the fusion proteins containing overlapping gE-1 peptides demonstrated FcR activity; the smallest peptide that retained Fc binding activity includes gE-1 amino acids 183 to 402. These results indicate that an Fc binding domain is located between gE-1 amino acids 183 and 402. To more precisely map the Fc binding domain, we tested a panel of 21 gE-i linker insertion mutants. Ten mutants with insertions between gE-i amino acids 235 and 380 failed to bind IgG-sensitized erythrocytes, while each of the remaining mutants demonstrated wild-type Fc binding activity. Taken together, these results indicate that the region of gE-i between amino acids 235 and 380 forms an FcR domain. A computer-assisted analysis of the amino acid sequence of gE-i demonstrates an immunoglobulin-like domain contained within this region (residues 322 to 359) which shares homology with mammalian FcRs.

In Vivo Immune Evasion Mediated by the Herpes Simplex Virus Type 1 Immunoglobulin G Fc Receptor

“…Wild-type HSV-1 strain NS is a low-passage-number clinical isolate and was used for the generation of mutant viruses (18). To construct a gE null virus (NS-gE null ), the entire gE coding sequence was excised from pCMV3gE-1 with XbaI and cloned into pSPT18 (14). A 1.1-kb HpaI-BglII fragment from amino acids 124 to 508 ( Fig.…”

“…Therefore, to study the role of the Fc␥R in virulence it was necessary to develop HSV-1 mutant viruses that are deficient in Fc binding while retaining other gE and gI functions. Using this rationale, an HSV-1 mutant virus that has a four-amino-acid insert within the gE IgG Fc binding domain was generated (3,14). This Fc␥R Ϫ virus remained intact for virus spread at the skin inoculation site in mice and caused disease comparable in severity to that caused by wild-type and marker-rescued viruses.…”

Herpesviral Fcγ receptors: culprits attenuating antiviral IgG?

“…gE and gI are exposed on the surface of infected cells and represent also the most abundant structural glycoproteins within the virus envelope. Alignment of a limited portion of the extracellular chain of gE reveals a low sequence similarity with the second domain of cFcgRs [92]. While gE alone binds only aggregated IgG with low affinity, complex formation with gI induces a high affinity receptor which is able to fix monomeric IgG.…”

“…The a-herpesviral FcgR is composed by the gE:gI complex. gE but not gI exhibits a low sequence similarity to the second domain of cFcgRs[92]. The Ig domains of FcgRII and FcgRIII are depicted in their bent orientation that is seen in the crystal structures.…”

Neutralizing Antibodies Inhibit Axonal Spread of Herpes Simplex Virus Type 1 to Epidermal Cells In Vitro

“…Polyclonal human sera (with high neutralizing titers for HSV-1 or HSV-2) were obtained from individuals with frequent recurrences of HSV-1 or HSV-2 and filtered. Monospecific rabbit polyclonal anti-gB1, anti-gC1, and anti-gD1 sera were kindly donated by G. Cohen and R. Eisenberg (University of Pennsylvania) (20,21), polyclonal rabbit anti-gG2 serum was kindly donated by R. Courtney (Pennsylvania State University) (43), and a polyclonal rabbit antibody to gE expressed in baculovirus was kindly donated by H. Friedman (University of Pennsylvania) (11). The human recombinant monoclonal anti-HSV-1 antibody (HSV8) used in this study was previously described (3,38,46).…”