An oncolytic vaccinia virus expressing the human sodium iodine symporter prolongs survival and facilitates SPECT/CT imaging in an orthotopic model of malignant pleural mesothelioma.

Background. The purpose of this work was to examine the ability of an oncolytic vaccinia virus expressing the human sodium iodine transporter (hNIS) to provide real time monitoring of viral therapy and effective treatment of malignant pleural mesothelioma (MPM). Methods. Infectivity and cytotoxic effects of GLV-1h153 on mesothelioma cell lines of all histologic subtypes were assayed in vitro. Viral replication was examined by standard viral plaque assay. Orthotopic MPM xenografts were generated in athymic nude mice, treated with intrapleural GLV-1h153, and assessed for effect on tumor burden and survival. Orthotopic tumors were also imaged on single photon emission computed tomography (SPECT)/computed tomography (CT) after I-131 administration. Results. GLV-1h153 infected and killed all cell lines in a time- and concentration-dependent manner. Viral replication demonstrated a >2.5-log increase in titer over 4 days. Intrapleural treatment of orthotopic MPM xenografts resulted in a significant decrease in tumor burden 1 week after treatment and an improvement in survival. Infection of orthotopic xenografts was both therapeutic and facilitated monitoring by I-131-SPECT/CT via expression of hNIS in infected tissue. Conclusion. Our results suggest that GLV-1h153 may be a promising therapeutic agent for MPM and warrants further investigation.