Effect of Deletion of the Ribonucleotide Reductase Gene in Wild Type and Virion Associated Host Shutoff (vhs-1) Mutant Herpes Simplex Virus-1 on Viral Proliferation and Infected-Carcinoma Cell Cultures Growth

Glioblastoma multiforme is the most prevalent and deadliest form of glioma and brain cancer, with a very poor prognosis. In an effort to develop an oncolytic viral vector for the treatment of Glioblastoma multiforme, we replaced the UL39 and UL40 genes encoding ribonucleotide reductase (RR) with green fluorescence protein and luciferase genes in wild type KOS and in the virion host shutoff mutant vhs-1, resulting in strains KOS-RR and Vhs-RR, respectively. KOS-RR and Vhs-RR caused death of infected U87 Glioblastoma multiforme cell cultures within one day after infection, whereas KOS and vhs-1-infected cells were more viable. All four viral strains caused apoptotic DNA laddering in infected H1299 lung cancer cells, while only Vhs-RR caused apoptosis in U87 cell cultures. Vhs-RR gave higher yields on U87 than on Vero cells, while it barely proliferated on non-dividing Goiter cells. These results indicate that Vhs-RR proliferates well in actively growing U87 Glioblastoma multiforme cells, causing their death in a mechanism involving apoptosis, while sparing non-dividing cells. Therefore, Vhs-RR is a promising candidate for oncolytic treatment of brain tumor malignancies.