Mapping regions of herpes simplex virus type 1 glycoprotein I required for formation of the viral Fc receptor for monomeric IgG.
Glycoprotein E (gE) and glycoprotein I (gI) of herpes simplex virus type 1 (HSV-1) form a complex that binds the Fc domain of monomeric IgG. In this study, we used two approaches to map the regions of gI-1 required for formation of the HSV-1 Fc receptor for monomeric IgG. First, we constructed six plasmids encoding gD-1/gI-1 fusion proteins. Each fusion protein contains a large gI-1 peptide inserted into the ectodomain of gD-1. gD-1/gI-1 fusion proteins were coexpressed with gE-1 using a transfection-infection assay in which cells were transfected with individual fusion protein constructs and then infected with a gE+/gI- virus. Cells were then assayed for monomeric IgG binding using immunofluorescence microscopy. Transfection-infection with two of six fusion proteins conferred monomeric IgG binding activity to cells, whereas cells infected with gE+/gI- virus alone failed to bind IgG monomers. The smallest gI-1 peptide to confer monomeric IgG binding activity contained amino acids 43 to 192. To more precisely map the region of gI-1 required for monomeric IgG binding, we constructed a panel of 10 gI-1 linker insertion mutants. Transfection-infection studies identified two mutants containing linker insertions at gI-1 amino acids 128 and 145, which failed to bind monomeric IgG. The other eight mutants demonstrated wild-type IgG binding activity. Taken together, these results indicate that the region of gI-1 between amino acids 128 and 145 is required for formation of the HSV-1 Fc receptor for monomeric IgG.
Basu
S
S
Infectious Disease Division, Department of Medicine, University of Pennsylvania, Philadelphia 19104, USA.
Dubin
G
G
Nagashunmugam
T
T
Basu
M
M
Goldstein
L T
LT
Wang
L
L
Weeks
B
B
Friedman
H M
HM
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000914:Antibodies, Viral / Q000276:immunology*; D002460:Cell Line; D018604:Epitope Mapping / Q000379:methods*; D019084:Fluorescent Antibody Technique, Indirect; D051379:Mice; D016254:Mutagenesis, Insertional / Q000276:immunology; D017452:Receptors, IgG / Q000032:analysis*; D018139:Simplexvirus / Q000276:immunology; D014759:Viral Envelope Proteins / Q000032:analysis*
D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D017452:Receptors, IgG; D014759:Viral Envelope Proteins; C039447:glycoprotein D, Human herpesvirus 1; C044768:glycoprotein E, herpes simplex virus type 1; C064959:glycoprotein I, herpes simplex virus type 1