Cowpea Mosaic Virus Outperforms Other Members of the Secoviridae as In Situ Vaccine for Cancer Immunotherapy

Abstract

In situ vaccination for cancer immunotherapy uses intratumoral administration of small molecules, proteins, nanoparticles, or viruses that activate pathogen recognition receptors (PRRs) to reprogram the tumor microenvironment and prime systemic antitumor immunity. Cowpea mosaic virus (CPMV) is a plant virus thatwhile noninfectious toward mammals activates mammalian PRRs. Application of CPMV as in situ vaccine (ISV) results in a potent and durable efficacy in tumor mouse models and canine patients; data indicate that CPMV outperforms small molecule PRR agonists and other nonrelated plant viruses and virus-like particles (VLPs). In this work, we set out to compare the potency of CPMV versus other plant viruses from the Secoviridae. We developed protocols to produce and isolate cowpea severe mosaic virus (CPSMV) and tobacco ring spot virus (TRSV) from plants. CPSMV, like CPMV, is a comovirus with genome and protein homology, while TRSV lacks homology and is from the genus nepovirus. When applied as ISV in a mouse model of dermal melanoma (using B16F10 cells and C57Bl6J mice), CPMV outperformed CPSMV and TRSVagain highlighting the unique potency of CPMV. Mechanistically, the increased potency is related to increased signaling through toll-like receptors (TLRs)in particular, CPMV signals through TLR2, 4, and 7. Using knockout (KO) mouse models, we demonstrate here that all three plant viruses signal through the adaptor molecule MyD88with CPSMV and TRSV predominantly activating TLR2 and 4. CPMV induced significantly more interferon β (IFNβ) compared to TRSV and CPSMV; therefore, IFNβ released upon signaling through TLR7 may be a differentiator for the observed potency of CPMV-ISV. Additionally, CPMV induced a different temporal pattern of intratumoral cytokine generation characterized by significantly increased inflammatory cytokines 4 days after the second of 2 weekly treatments, as if CPMV induced a "memory response". This higher, longer-lasting induction of cytokines may be another key differentiator that explains the unique potency of CPMV-ISV.

In situ vaccination with cowpea mosaic virus elicits systemic antitumor immunity and potentiates immune checkpoint blockade

“…This corresponds to our previous findings that proinflammatory cytokines were induced in treated TdLNs. 36 cDC1 efficiently cross-present antigens to CD8 + T cells and require the transcription factor BATF3 for development. 19 37 Thus, we tested whether cDC1s were necessary for treatment efficacy.…”

In Vivo Fate of Cowpea Mosaic Virus In Situ Vaccine: Biodistribution and Clearance

“…Here, we focused on translational studies for development of CPMV as an in situ vaccine for cancer therapy. In prior work, we discovered that intratumoral CPMV nanoparticles prime potent, durable, systemic antitumor immunity with demonstrated efficacy in mouse models and canine patients. ,− The work presented here was motivated as a prelude toward investigational new drug (IND)-enabling toxicology studies. We analyzed prevalence of anti-CPMV antibodies in humans and performed biodistribution and clearance studies to gain insight into the pharmacology and fate of CPMV (i.e., determine the degree of leaching and whether shedding occurs).…”

“…Our laboratory is developing a plant-virus-based in situ vaccine (ISV) with demonstrated efficacy in multiple tumor mouse models and canine patients. Specifically, cowpea mosaic virus (CPMV) − is used, and we capitalize on the immunostimulatory nature of the plant virus that when injected intratumorally (I.T.) activates innate immune cells within the tumor microenvironment (TME), therefore overcoming the immunosuppressive features of cold and aggressive tumors.…”

Advances in the Application of Nanomaterials to the Treatment of Melanoma

“…The tumor itself provides the antigen for ISV, and the treatment only uses the immune agent directly on the tumor. ISV is used for cancer immunotherapy, small-molecule proteins, or viral tumors to activate the pathogen recognition receptors that alter the tumor microenvironment and cause systemic antitumor immunity [ 155 ]. Various oncolytic viruses with ISV functions have been approved for treatment or are undergoing clinical trials, such as PVSRIPO, an engineered oncolytic poliovirus [ 156 ].…”

“…CPMV has been shown to bind specifically to the mammalian protein vimentin, a cytoskeletal protein involved in various cellular functions that can be surface-expressed or secreted in tumor cells, endothelial cells, and immune cells [ 157 ]. Studies have confirmed that the CPMV-ISV manages the IFNβ signaling pathway by activating the TLR7 in the mouse model of skin melanoma, showing a good antitumor effect [ 155 ]. Jiang et al researched the nano PC7A vaccine and confirmed that intratumoral delivery had stronger antitumor immunity and curative effects [ 158 ].…”