Next Generation RNA/Protein-Carrying Vector With Pleiotropic Activity

Human parainfluenza virus type 2 (hPIV2), one of the causative agents of infantile common cold, is a non-segmented negative-sense RNA virus with a robust gene expression system. It infects recurrently throughout human life without causing severe disease. Because hPIV2 has a viral envelope that can carry ectopic proteins, we developed a non-propagative RNA/protein-carrying vector BC-PIV by deleting the F gene from hPIV2. BC-PIV can be vigorously proliferated in the stable packaging cell line Vero/BC-F cells expressing the hPIV2 F gene but not in other cells. BC-PIV can deliver exogenous gene(s) on a multigenic RNA genome as an inserted gene fragment(s) and simultaneously deliver exogenous protein(s) on its envelope in a membrane-anchored form. For example, influenza virus M2e protein, Ebola virus GP protein, and severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) spike protein were shown to be highly expressed in packaging cells and incorporated into the virion. The Ebola virus GP protein and SARS-CoV-2 spike protein, each delivered via BC-PIV, efficiently induced neutralising antibodies against each virus, even after prior treatment with recombinant BC-PIV in mice and hamsters, respectively. In this review, we describe the properties of BC-PIV as a promising vaccine vector, and also demonstrate its application as an anti-tumour virus.