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 (gl) of herpes simplex virus ty pe 1 (HSV-1) form a complex that binds the Fe domain of monomeric IgG, In this study, we used two approaches to map the regions of gl-1 requ ired for formation of the HSV-1 Fc receptor for monomeric Igc, First, we constructed six plasmids encoding gD-1/gl-1 fusion proteins, Each f usion protein contains a large gl-1 peptide inserted into the ectodoma in of gD-1, gD-1/gl-1 fusion proteins were coexpressed with gE-1 using a transfection-infection assay in which cells were transfected with i ndividual fusion protein constructs and then infected with a gE(+)/gl( -) virus, Cells were then assayed for monomeric IgG binding using immu nofluorescence microscopy. Transfection-infection with two of six fusi on proteins conferred monomeric IgG binding activity to cells, whereas cells infected with gE(+)/gl(-) virus alone failed to bind IgG monome rs. The smallest gl-1 peptide to confer monomeric Ige binding activity contained amino acids 43 to 192, To more precisely map the region of gl-1 required for monomeric IgG binding, we constructed a panel of 10 gl-1 linker insertion mutants, Transfection-infection studies identifi ed two mutants containing linker insertions at gl-1 amino acids 128 an d 145, which failed to bind monomeric IgG, The other eight mutants dem onstrated wild-type IgG binding activity, Taken together, these result s indicate that the region of gl-1 between amino acids 128 and 145 is required for formation of the HSV-1 Fc receptor for monomeric IgG.