The Company’s proprietary virus-like vesicle (VLV) technology is a hybrid of components from two unrelated animal viruses: the alphavirus Semliki Forest virus (SFV) and rhabdovirus vesicular stomatitis virus (VSV), producing particles that have limited replication-competence in vivo. Unlike other viral-based vector vaccines, human infection with SFV and VSV is rare, so the general population is free of pre-existing, virus-neutralizing antibodies that could compromise vaccine efficacy. The VLVs generated can enter into cells of treated subject where, although limited, they propagate sufficiently to express the VLV-encoded antigens to be presented to the host immune system.
Figure 1: Diagram of the hybrid Alphavirus-Rhabdovirus vector for production of VLV. DNA sequence encoding Semliki Forest Virus (SFV) replicase complex (SFVnsp1-4, green) plus Vesicular Stomatitis Virus G-glycoprotein (VSV-G, burgundy) were cloned into the VLV-producing DNA plasmid (circle), separated by SFV SGP (sub-genomic promoter; indicated by the large open arrow). Upon introduction (transfection) into mammalian cell lines, such as BHK-21, transcription from the CMV promoter (small open arrow) produces a hybrid vRNA, from which both the SFV replicase and the VSV-G protein are expressed. The latter protein is produced in the endoplasmic reticulum (ER) and transported through the Golgi apparatus to the plasma membrane. Non-specific interactions between the VSV-G cytoplasmic domain and the hybrid vRNA leads to the release of “virus-like vesicles” (VLVs) able to transfer vRNA to new cells. Introduction of coding sequence for various components (proteins, antigens, cytokines, shRNA) downstream of the SGP allows for delivery and expression of these components in VLV-infected cells (Rose et al., PNAS 2014, 111(47):16866-16871).