Neuroattenuation of vesicular stomatitis virus through picornaviral internal ribosome entry sites

Vesicular stomatitis virus (VSV) is potent and a highly promising agent for the treatment of cancer. However, translation of VSV oncolytic virotherapy into the clinic is being hindered by its inherent neurotoxicity. It has been demonstrated that selected pi-cornaviral internal ribosome entry site (IRES) elements possess restricted activity in neuronal tissues. We therefore sought to determine whether the picornavirus IRES could be engineered into VSV to attenuate its neuropathogenicity. We have used IRES elements from human rhinovirus type 2 (HRV2) and foot-and-mouth disease virus (FMDV) to control the translation of the ma-trix gene (M), which plays a major role in VSV virulence. In vitro studies revealed slowed growth kinetics of IRES-controlled VSVs in most of the cell lines tested. However, in vivo studies explicitly demonstrated that IRES elements of HRV2 and FMDV severely attenuated the neurovirulence of VSV without perturbing its oncolytic potency. Vesicular stomatitis virus (VSV), a member of the Rhabdoviri-dae family, replicates selectively in variety of cancer cells (1– 5). VSV can infect a wide range of animals but primarily affects horses, donkeys, cattle, and swine. Human infection produces only influenza-like symptoms (6). VSV has a nonsegmented neg-ative-strand RNA genome of approximately 11 kb encoding five structural proteins: nucleoprotein (N), phosphoprotein (P), ma-trix protein (M), glycoprotein (G), and RNA polymerase (L). Th