Understanding plant virus-based adjuvants as therapeutics

This application is focused on the study of bioengineered plant virus-based adjuvant and vaccine technology. We discovered that some plant viruses serve as potent adjuvants in the context of infectious disease and cancer vaccines/immunotherapy. Cowpea mosaic virus (CPMV) was identified as a uniquely potent adjuvant with distinct mechanism of immunomodulation compared to small molecule agonists, other plant viruses, or oncolytic viruses. Recently we discovered that systemic CPMV administration prior to tumor challenge protects mice from onset of tumor growth. Data indicate that the innate immune stimulation by CPMV is durable and lasts for weeks after CPMV exposure when innate cells would have returned to a homeostasis state – therefore data are consistent with induction of trained immunity. Single cell sequencing analysis of human PBMCs after CPMV adjuvant exposure indicates stimulation of interferon signaling pathways along with metabolic changes, and epigenetic rewiring – also consistent with a mechanism involving trained immunity. Together our data suggest that CPMV could act as an inducer of trained immunity – to date there are no reports on the study of plant viruses in trained immunity. Proposed studies will help elucidate the foundational principles that make CPMV a uniquely potent immunomodulator. We will fulfil the following specific aims: (1) We will establish the mechanism of CPMV as a training agent in vitro using immune cells followed by LPS challenge; longitudinal studies will be carried out and analysis will include measure of pro- inflammatory cytokine as well as CHiP and ATAC sequencing to confirm epigenetic rewiring and metabolic cell changes. Structure-function studies of bioengineered viruses will provide foundational insights into differential potency. (2) We will establish the mechanism of CPMV as a training agent using the B16F10 tumor model using WT and Rag 1 vs CCR2 knockout (KO) mice to delineate the role of adaptative vs. innate immune cells (β-glucan will serve as benchmark). Hematopoietic stem cells (HSCs) and multipotent progenitors (MPPs) will be analyzed by single cell sequencing, CHiP and ATAC sequencing to delineate the mechanism of action. Studies will be paralleled with safety and biodistribution studies. (3) We will test the ability of the CPMV training agent to facilitate protection from influenza virus challenge; protection from influenza virus infection and pathology from CPMV will be benchmarked against FLUMIST and β-glucan. These studies could lay the foundation for continued and deeper studies of CPMV as an adjuvant technology towards the development of more broadly protective and efficacious vaccine formulations and immunoprevention strategies. Project Number: 1R21CA309173-01 | Fiscal Year: 2026 | NIH Institute/Center: National Cancer Institute (NCI) | Principal Investigator: Nicole Steinmetz | Institution: UNIVERSITY OF CALIFORNIA, SAN DIEGO, LA JOLLA, CA | Award Amount: $420,505 | Activity Code: R21 | Study Section: Innovations in Nanosystems and Nanotechnology Study Section [INN] View on NIH RePORTER: https://reporter.nih.gov/project-details/11281975