Marker gene transfer and oncolysis of human Y79 retinoblastoma cells mediated by herpes simplex virus mutants

Three different herpes simplex virus (HSV) mutants, designated hrR3, MGH-1 and R3616, were used to infect Y79 retinoblastoma cells grown in suspension. Two parameters were assayed: (a) vector-mediated gene expression, measured by histochemical staining of a transferred LacZ transgene, and (b) virus-mediated oncolysis, determined by the inability of infected cells to exclude trypan blue dye. The tested HSV mutants were found to infect cells grown in suspension at a relatively low multiplicity of infection (MOI = 0.01) and were capable of transferring the LacZ gene as early as 2 days after infection. Furthermore, differences in oncolytic activity were observed amongst the tested viruses: MGH-1 and R3616 exhibited 50% cell kill at a MOI of 0.1 over a period of 6 days, whereas hrR3-mediated oncolysis appeared less efficient. These studies provide a rationale for further exploitation of oncolytic herpes viruses as a potential treatment of intraocular tumors.