Replication-competent oncolytic adenoviruses (OAds) are promising anticancer therapeutics. Adenoviruses have a lytic life cycle and can be engineered to selectively replicate in tumor cells. An important attribute of OAds is their immunogenicity. When they infect and subsequently kill tumor cells, OAds elicit robust local and systemic immune responses that can counteract an immunosuppressive tumor microenvironment. Neoantigens released during a lytic infection can stimulate T cell activation by professional antigen presenting cells, thereby increasing the immune response to the tumor. Unfortunately, immune responses are primarily directed against the virus itself; cross reactivity against the targeted tumor is frequently limited. To enhance anti-tumor immunity in the context of an active infection, we have developed OAds that can reconstitute pHLA-immunopeptide complexes on the surface of infected cells.

We employed a platform technology called AdenoBuilder to create OAds that stimulate robust immune responses to antigenic peptides incorporated into the viral capsid. With the AdenoBuilder platform, synthetic adenovirus genomes are enzymatically assembled from plasmid components and directly packaged. This modular approach permits the rapid production of recombinant viral vectors with modifications across the viral genome. Our personalized OAds enhance neoantigen presentation by the transgenic expression of tumor-specific neoantigens and compatible HLA alleles that can be matched to the allelotype of individual patients. To further enhance antigen presentation, our current replication-competent OAds also express β-2-microglobin and the IL-12 complex.

We tested a prototype OAd designed to elicit specific T cell responses against the public neoantigen HMTEVVRHC (derived from the p53R175H mutant protein) which was systematically modified to enhance its binding affinity for HLA-A*0201. The optimized peptide sequence was incorporated into the capsid of an OAd that also expressed HLA-A*0201, β-2-microglobin and the IL-12 complex. We demonstrated that this neoantigen-expressing OAd could stimulate robust, neoantigen-specific anti-tumor responses in an HLA-A2-transgenic mouse model.

OAds that express specified pHLA-immunopeptide complexes are an emerging form of precision immunotherapy. This study demonstrates the feasibility of using the AdenoBuilder system to rapidly generate OAds that are personalized to individual patients and their tumors.