Abstract 4371: Preclinical potential of γδ T cells in novel virus-like particle vaccines for triple-negative breast cancer

Abstract Triple-negative breast cancer (TNBC) is an aggressive subtype with limited treatment options, high recurrence rates and poor outcomes. The conventional treatment among the standard of care strategies fail to elicit a long-term benefit for these patients. Personalized cancer vaccines using virus-like particles (VLPs), represent a promising strategy with the potential to induce durable immune responses. Recent research has highlighted the innate and adaptive properties of γδ T cells, underscoring their potential in cancer immunotherapy. However, how VLPs interact with γδ T cells, and their clinical efficacy to enhance their antitumor activity remains poorly understood and requires further investigation. We designed and developed novel next-generation VLPs engineered to incorporate cell-adjuvanted innate ligands and present tumor-neoantigens on their surface from a preclinical model of TNBC. We validated them by Cryo-EM and biochemical assays. We evaluated the interaction of VLPs with γδ T cells in wildtype and transgenic mice by transmission imaging techniques. Tumor in vivo experimentation was carried out in the 4T1 TNBC model. We compared three subcutaneous (s.c.) administration routes: systemic, targeting tumor-draining lymph nodes (tdLNs), and targeting non-tdLNs. Survival was assessed under different dosing and immune checkpoint inhibitor co-treatment. CD4, CD8, and γδ T cells were depleted to determine their contributions. We performed immunohistochemistry, flow cytometry, and RNA-seq analysis to evaluate the immune response. Our results show that γδ T cells efficiently engulfed VLPs in wild-type mice while this interaction is hindered in transgenic mice lacking key components of innate immune sensing pathways. Our novel VLPs expanded γδ T cells in tdLNs, promoting antitumor subsets and phenotypes. Subtype analysis revealed distinct activation profiles of γδ T cells subsets Vγ-1 and Vγ-4. Evaluation of tdLNs and tumors revealed early expansion of γδ T cells, highlighting innate properties. Depletion of γδ T cells abolished antitumor efficacy of the immunotherapy, suggesting adaptive properties. Furthermore, our personalized vaccine enhanced tumor infiltration of CD4, CD8 and γδ T cells, increased cytotoxic markers, reduced recurrence and metastasis, and improved survival despite low tumor mutational burden. Our findings reveal novel innate and adaptive properties of γδ T cells in response to our next-generation VLPs loaded with diverse innate immune stimuli and presenting tumor-neoantigens from 4T1 cells. These findings have the potential to reshape the field of cancer vaccines by harnessing γδ T cells as key players in anti-tumor immunity. (AI tools were used only to improve the clarity of the text in this abstract. All content was reviewed and verified by the authors.) Citation Format: Arnau Solé Casaramona, Anish Ghimire, Romano Josi, Sanjana Marar, Anita Ogriņa-Komarova, Simone De Brot, Chang Wang, David Wiggins, Wendao Liu, Sarat Kumar Kottarath, Martin F. Bachmann, Eva M. Sevick, Mona O. Mohsen. Preclinical potential of γδ T cells in novel virus-like particle vaccines for triple-negative breast cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4371.