A recombinant herpes simplex virus type-1 (HSV-1) has been constructed that carries a deletion of one of the two viral γ1 34.5 genes and other immediate early genes, which render the virus able to selectively replicate in cancer cells but not efficiently replicate in normal cells, and in which specific mutations have been introduced to enable the virus to spread among cancer cells by virus-induced fusion. Specifically, syncytial mutations have been introduced in the genes coding for glycoprotein B and glycoprotein K of the virus, enabling high replication and spread of the virus in cancer cells in the presence of substantially lower amounts of γ1 34.5 protein, which is required for optimum infectious virus produced and virus-induced cell fusion. These altered viruses or the isolated bacterial chromosomes could be used to treat various cancers including breast, liver, colon, and other tissues.
