An isolated clonal LIVP strain other than a clonal strain whose genome comprises the sequence of nucleotides set forth in SEQ ID NO:10, wherein: the clonal strain does not contain non-viral heterologous nucleic acid containing an open reading frame encoding a non-viral heterologous protein; the clonal strain comprises a sequence of nucleotides that has at least 90% sequence identity with the sequence of nucleotides set forth in SEQ ID NO:10; and the clonal strain has greater anti-tumorigenicity and/or reduced toxicity compared to GLV-1h68, wherein GLV-1h68 has the sequence of nucleotides set forth in SEQ ID NO:9; and the isolated clonal strain comprises the sequence of nucleotides selected from: a) nucleotides 2256 - 181,114 of SEQ ID NO:1, nucleotides 11,243-182,721 of SEQ ID NO:2, nucleotides 6,264- 181,390 of SEQ ID NO:4, nucleotides 7,044 - 181,820 of SEQ ID NO:5, nucleotides 6,674 - 181,409 of SEQ ID NO:6, nucleotides 6,716 - 181,367 of SEQ ID NO:7 or nucleotides 6,899 - 181,870 of SEQ ID NO:8; or b) a sequence of nucleotides that has at least 99% sequence identity to the sequence of nucleotides 2256 - 181,114 of SEQ ID NO:1, nucleotides 11,243 -182,721 of SEQ ID NO:2, nucleotides 6,264 - 181,390 of SEQ ID NO:4, nucleotides 7,044 - 181,820 of SEQ ID NO:5, nucleotides 6,674 - 181,409 of SEQ ID NO:6, nucleotides 6,716 - 181,367 of SEQ ID NO:7 or nucleotides 6,899 - 181,870 of SEQ ID NO:8. the clonal strain does not contain non-viral heterologous nucleic acid containing an open reading frame encoding a non-viral heterologous protein; the clonal strain comprises a sequence of nucleotides that has at least 90% sequence identity with the sequence of nucleotides set forth in SEQ ID NO:10; and the clonal strain has greater anti-tumorigenicity and/or reduced toxicity compared to GLV-1h68, wherein GLV-1h68 has the sequence of nucleotides set forth in SEQ ID NO:9; and the isolated clonal strain comprises the sequence of nucleotides selected from: a) nucleotides 2256 - 181,114 of SEQ ID NO:1, nucleotides 11,243-182,721 of SEQ ID NO:2, nucleotides 6,264- 181,390 of SEQ ID NO:4, nucleotides 7,044 - 181,820 of SEQ ID NO:5, nucleotides 6,674 - 181,409 of SEQ ID NO:6, nucleotides 6,716 - 181,367 of SEQ ID NO:7 or nucleotides 6,899 - 181,870 of SEQ ID NO:8; or b) a sequence of nucleotides that has at least 99% sequence identity to the sequence of nucleotides 2256 - 181,114 of SEQ ID NO:1, nucleotides 11,243 -182,721 of SEQ ID NO:2, nucleotides 6,264 - 181,390 of SEQ ID NO:4, nucleotides 7,044 - 181,820 of SEQ ID NO:5, nucleotides 6,674 - 181,409 of SEQ ID NO:6, nucleotides 6,716 - 181,367 of SEQ ID NO:7 or nucleotides 6,899 - 181,870 of SEQ ID NO:8. a) nucleotides 2256 - 181,114 of SEQ ID NO:1, nucleotides 11,243-182,721 of SEQ ID NO:2, nucleotides 6,264- 181,390 of SEQ ID NO:4, nucleotides 7,044 - 181,820 of SEQ ID NO:5, nucleotides 6,674 - 181,409 of SEQ ID NO:6, nucleotides 6,716 - 181,367 of SEQ ID NO:7 or nucleotides 6,899 - 181,870 of SEQ ID NO:8; or b) a sequence of nucleotides that has at least 99% sequence identity to the sequence of nucleotides 2256 - 181,114 of SEQ ID NO:1, nucleotides 11,243 -182,721 of SEQ ID NO:2, nucleotides 6,264 - 181,390 of SEQ ID NO:4, nucleotides 7,044 - 181,820 of SEQ ID NO:5, nucleotides 6,674 - 181,409 of SEQ ID NO:6, nucleotides 6,716 - 181,367 of SEQ ID NO:7 or nucleotides 6,899 - 181,870 of SEQ ID NO:8.