Recombinant Herpes Simplex Virus Type 1 Engineered for Targeted Binding to Erythropoietin Receptor-Bearing Cells

The utility of recombinant herpes simplex virus type 1 (HSV-1) vectors may be expanded by manipulation of the virus envelope to achieve cell-specific gene delivery. To this end, an HSV-1 mutant virus deleted for glycoprotein C (gC) and the heparan sulfate binding domain of gB (KgBpK⁻gC⁻) was engineered to encode different chimeric proteins composed of N-terminally truncated forms of gC and the full-length erythropoietin hormone (EPO). Biochemical analyses demonstrated that one gC-EPO chimeric molecule (gCEPO₂) was posttranslationally processed, incorporated into recombinant HSV-1 virus (KgBpK⁻gCEPO₂), and neutralized with antibodies directed against gC or EPO in a complement-dependent manner. Moreover, KgBpK⁻gCEPO₂ recombinant virus was specifically retained on a soluble EPO receptor column, was neutralized by soluble EPO receptor, and stimulated proliferation of FD-EPO cells, an EPO growth-dependent cell line. FD-EPO cells were nevertheless refractory to productive infection by both wild-type HSV-1 and recombinant KgBpK⁻gCEPO₂ virus. Transmission electron microscopy of FD-EPO cells infected with KgBpK⁻gCEPO₂ showed virus endocytosis leading to aborted infection. Despite the lack of productive infection, these data provide the first evidence of targeted HSV-1 binding to a non-HSV-1 cell surface receptor.