Targeting vaccinia to solid tumors with local hyperthermia.

Area of Science:

• Oncolytic virotherapy
• Cancer research
• Biomedical engineering

Background:

• Mutant vaccinia viruses show promise as vectors for tumor-directed gene therapy.
• Hyperthermia is known to increase endothelial vasculature permeability to nanoparticles.
• Previous studies demonstrated vaccinia virus targeting of tumors after systemic delivery.

Purpose of the Study:

• To investigate whether hyperthermia can augment vaccinia virus delivery to tumors following systemic injection.
• To assess the impact of hyperthermia on vaccinia virus infectivity, gene expression, and cytopathogenicity in tumor cells.
• To evaluate the in vivo efficacy of hyperthermia-combined vaccinia virus therapy in a mouse tumor model.

Main Methods:

• In vitro assessment of hyperthermia's effect on tumor cell susceptibility to vaccinia virus and viral gene expression.
• In vitro endothelial cell monolayer model to evaluate hyperthermia-induced changes in vascular permeability to vaccinia virus.
• In vivo studies in mice with subcutaneous tumors, comparing systemic vaccinia virus delivery with and without regional hyperthermia (41.5°C for 30 min).
• Measurement of vaccinia marker gene activity in tumors and assessment of tumor volume and regression.

Main Results:

• Hyperthermia did not alter tumor cell susceptibility to vaccinia virus or affect viral infectivity and gene expression in vitro.
• Hyperthermia significantly increased endothelial cell monolayer permeability to vaccinia virus in vitro, an effect that was reversible.
• In vivo, tumors treated with systemic vaccinia under hyperthermia showed over 100-fold higher vaccinia marker gene activity compared to normothermic conditions.
• Mice treated with hyperthermia and vaccinia virus exhibited complete tumor regression in 50% of cases and significantly reduced tumor volume compared to controls.

Conclusions:

• Regional hyperthermia enhances the targeting of systemically delivered vaccinia virus to tumors.
• The improved tumor targeting mediated by hyperthermia significantly enhances the antitumor response.
• Hyperthermia-combined vaccinia virus therapy represents a promising strategy for improving oncolytic virotherapy outcomes.