High therapeutic potential for systemic delivery of a liposome-conjugated herpes simplex virus.

PURPOSE: Oncolytic viral therapy is a newly developed modality to treat tumors. Many clinical trials worldwide have examined the efficacy of locally injected oncolytic viruses. However, systemic intravascular injections are limited by the humoral immune response, which dramatically decreases the level of infection. To overcome this limitation, we encapsulated the oncolytic virus in liposomes. METHODS: The infectious properties of the herpes simplex virus type 1 (HSV-1) mutant, hrR3, with or without liposomes in the presence of neutralizing antibodies were evaluated using replication and cytotoxicity assays in vitro. To evaluate the efficacy of intravascular virus therapy with liposomes in the presence of neutralizing antibodies, immunized mice bearing multiple liver metastases were intraportally or peritoneally administered hrR3 or hrR3 complexed with liposomes. RESULTS: Anti-HSV antibodies attenuated the infectiousness and cytotoxicity of hrR3, whereas hrR3/liposome complexes were not attenuated by these anti-HSV antibodies. Although the survival rate of non-immunized mice treated with hrR3 alone was similar to that of mice treated with the hrR3/liposome complexes, the survival rates of immunized mice treated with hrR3 alone were significantly reduced compared to mice treated with the hrR3/liposome complexes. CONCLUSIONS: This systemic intravascular delivery of hrR3/liposome complexes in the presence of pre-existing neutralizing antibodies is effective to treat multiple liver metastases.

Considerations for intravascular administration of oncolytic herpes virus for the treatment of multiple liver metastases.

PURPOSE: Oncolytic viral therapy is a newly developed modality for treating tumors. Many clinical trials using oncolytic virus have been performed worldwide, but most of them have used local injection in the tumor. Determination of the effect and safety of intravascular virus injection instead of local injection is necessary for clinical use against multiple liver metastases and systemic metastases. METHODS: To evaluate the efficacy and safety of intravascular virus therapy, mice bearing multiple liver metastases were treated by intraportal or intravenous administration of the herpes simplex virus type 1 (HSV-1) mutant, hrR3. Mice treated with hrR3 were killed and organs were harvested for lacZ staining and PCR analysis. Inactivation of oncolytic virus in bloodstream was assessed by neutralization assay in vitro. Infectious activity of hrR3 with vascular endothelial cells was evaluated by replication and cytotoxicity assay. RESULTS: The survival rate of animals treated by hrR3 was significantly improved compared with the untreated group. lacZ staining and PCR analysis demonstrated detectable virus in the tumor but not in normal tissue or other organs except for the adrenal glands. We also showed that vascular endothelial cells allowed virus replication, while normal hepatocytes did not, and human anti-HSV antibody revealed attenuation of the infectious activity of hrR3. CONCLUSIONS: Intravascular delivery of hrR3 is effective in treating multiple liver metastases, however, several points must be kept in mind at the time of human clinical trials using intravascular virus administration in order to avoid critical side effects.