A Novel Immunization Method to Induce Cytotoxic T-Lymphocyte Responses (CTL) Against Plasmid-Encoded Herpes Simplex Virus Type-1 Glycoprotein D

DNA molecules complexed with an asialoglycoprotein–polycation conjugate, consisting of asialoorosomucoid (ASOR) coupled to poly-l-lysine, can enter hepatocytes which bear receptors for ASOR. We used this receptor-mediated DNA delivery system to deliver plasmid DNA encoding glycoprotein D (gD) of herpes simplex virus type 1 to ASOR-positive cells. Maximum expression of gD protein was seen at 3 days after injection of this preparation in approximately 13% of cells from BALB/c mice [hepatocytes from mice injected intravenously (i.v.) or peritoneal exudate cells from mice injected intraperitoneally (i.p.)]. In comparison with mice injected with either the plasmid vector alone or the gD-containing plasmid uncomplexed to ASOR, mice immunized with gD-containing plasmid complexed with ASOR–poly-l-lysine induced marked antigen-specific CTL responses. BALB/c mice immunized with gD–DNA developed a T-cell-mediated CTL response against target cells expressing gD and MHC class II glycoproteins, but not against cells expressing only gD and MHC class I molecules. In C3H mice, gD–DNA induced a T-cell-mediated CTL response against target cells expressing gD and class I MHC molecules. Serum anti-gD antibody in low titers were produced in both strains of mice. DNA complexed with ASOR–poly-l-lysine induced CTL responses in mice.