Vesicular stomatitis virus expressing destabilized tumor associated antigens with enhanced MHC class I presentation to improve anti-tumor T cell responses

• Published in: The Journal of immunology (1950) 2020-05, Vol.204 (1_Supplement), p.91-91.16
• Main Authors: Huff, Amanda, Evgin, Laura, Thompson, Jill, Kottke, Tim, Wongthida, Phonphimon, Driscoll, Christopher, Shim, Kevin G., Scheulke, Matthew, Vile, Richard G.
• Format: Article
• Language: English
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.204.Supp.91.16

We have previously shown that vesicular stomatitis virus (VSV) vectors encoding truncated tumor antigens, NRAS, Cytochrome C1, and TYRP1, prime superior systemic anti-tumor T cell responses and provide enhanced therapeutic benefit compared to vectors expressing full-length forms of the protein. Mapping of the roughly 20 amino C-terminal truncated regions onto structural domains of each protein suggested the truncations disrupted the stability and localization of each protein. Indeed, immunofluorescent staining and radiolabeled pulse chase found that truncated TYRP1 (ΔTYRP1) had an altered localization pattern and a significantly reduced half-life compared to full-length TYRP1. Thus, we hypothesized that expression of destabilized antigens from VSV would provide superior therapy compared to expression of wild-type antigens. To test this, we introduced point-mutations into structurally important domains of the model antigen ovalbumin (OVA). We identified one mutant which was significantly destabilized (OVAmut), which resulted in enhanced MHC Class I presentation of the immunogenic SIINFEKL epitope on transfected cell in vitro. Expression of OVAmut resulted in better recognition by cognate CD8 OTI T cells, enhanced T cell activation, proliferation, and effector cytokine production. Finally, a VSV vector expressing OVmut was better able to prime OTI T cells in vitro as well as in vivo. Ongoing studies aim to identify the changes in the quantity and repertoire of immunogenic epitopes presented from cells infected with VSV vectors expressing destabilized antigens. These studies provide insight into the capacity of the VSV platform to successfully encode unstable antigens with the goal improve immunogenic responses.