Comparative analyses for plant virus-based cancer immunotherapy drug development

Cowpea mosaic virus (CPMV) is a plant virus with potent anti-tumor efficacy. Intratumoral CPMV, but not cowpea chlorotic mottle virus (CCMV), reprograms the tumor microenvironment priming durable, systemic anti-tumor immunity. Here, we performed a side-by-side mechanism of action comparison between CPMV and CCMV. Through immune-multiplexing and trafficking studies we observed that CPMV and CCMV are taken up by innate immune cells at similar rates but are processed differently. While CCMV induces proinflammatory interleukins 22, 23, and 27, CPMV is a strong inducer of type I, II, and III interferons, which contribute to the activation and enhancement of immune cell function. We observed that CPMV RNAs activate Toll-like receptor (TLR) 7 upon delivery-and not CCMV RNAs; CPMV RNAs persist longer within cells compared with CCMV. Taken together, this work identifies determinants for CPMV's unique mechanism for intratumoral immunotherapy. It also broadens our understanding of the utility of plant viruses for biomedical applications.