The rodent parvoviruses are known to be oncoselective, and lytically infect many transformed human cells. Because current therapeutic regimens for metastatic melanoma have a low response rates and have little effect on improving survival, this disease is a prime candidate for novel approaches to therapy, including oncolytic parvoviruses. Screening of low-passage, patient-derived melanoma cell lines for multiplicity-dependent killing by a panel of five rodent parvoviruses, identified LuIII as the most melanoma-lytic. This property was mapped to the LuIII capsid gene, and an efficiently melanomatropic chimeric virus shown to undergo three types of interaction with primary human melanoma cells: 1) complete lysis of cultures infected at very low multiplicities; 2) acute killing resulting from viral protein synthesis and DNA replication, without concomitant expansion of the infection, due to failure to export progeny virions efficiently; or 3) complete resistance that operates at an intracellular step following virion uptake, but preceding viral transcription.

The orphan parvovirus tumor virus X (TVX) has potent oncolytic activity. Compared to other viruses from the species Rodent protoparvovirus 1, TVX has a 111 nucleotide deletion in its nonstructural (NS) gene, a 24 nucleotide insertion in VP1, and a 93 nucleotide repeat initiating from the C-terminus of the capsid gene.

The protoparvovirus early promoters, e.g. P4 of Minute Virus of Mice (MVM), play a critical role during infection. Initial P4 activity depends on the host transcription machinery only. Since this is cell-type dependent, it is hypothesized that P4 is a host cell-type range determinant. Yet host range determinants have mapped mostly to capsid, never P4. Here we test the hypothesis using the mouse embryo as a model system. Disruption of the CRE element of P4 drastically decreased infection levels without altering range. However, when we swapped promoter elements of MVM P4 with those from equivalent regions of the closely related H1 virus, we observed elimination of infection in fibroblasts and chondrocytes and the acquisition of infection in skeletal muscle. We conclude that P4 is a host range determinant and a target for modifying the productive infection potential of the virus - an important consideration in adapting these viruses for oncotherapy.