A co-formulated vaccine of irradiated cancer cells and cowpea mosaic virus improves ovarian cancer rejection.

Ovarian cancer ranks fifth in cancer deaths amongst women, and most patients are diagnosed with late-stage and disseminated diseases. Surgical debulking and chemotherapy remove most of the tumor burden and provide a short period of remission; however, most patients experience cancer relapse and eventually succumb to the disease. Therefore, there is an urgent need for the development of vaccines to prime anti-tumor immunity and prevent its recurrence. Here we developed vaccine formulations composed of a mixture of irradiated cancer cells (ICCs, providing the antigen) and cowpea mosaic virus (CPMV) adjuvants. More specifically we compared the efficacy of co-formulated vs. mixtures of ICCs and CPMV. Specifically, we compared co-formulations where the ICCs and CPMV are bonded through natural CPMV-cell interactions or chemical coupling vs. mixtures of PEGylated CPMV and ICCs, where PEGylation of CPMV prevents ICC interactions. Flow cytometry and confocal imaging provided insights into the composition of the vaccines and their efficacy was tested using a mouse model of disseminated ovarian cancer. 67% of the mice receiving the co-formulated CPMV-ICCs survived the initial tumor challenge, and 60% of the surviving mice rejected tumors in a re-challenge experiment. In stark contrast, simple mixtures of the ICCs and (PEGylated) CPMV adjuvants were ineffective. Overall, this study highlights the importance of the co-delivery of cancer antigens and adjuvants in ovarian cancer vaccine development.