A multitargeting nanoparticle-based vaccine for enhanced anticancer immunotherapy in HER2-Positive breast cancer.

Tumor vaccines represent promising strategies for cancer immunotherapy. However, their application remains restricted in HER2-positive breast cancer due to poor immunogenicity and inefficient antigen presentation. Herein, a multitargeting HER2 nanoparticle vaccine, HER2_aHPF, is developed by co-displaying the HER2 extracellular domain and AE37 T-cell epitope on a Helicobacter pylori ferritin nanoparticle via SpyTag/SpyCatcher conjugation. The nanoparticle vaccine exhibits structural homogeneity, enhanced lymphatic drainage, and high stability during freeze-thaw cycles and long-term storage, with retained immunogenicity after repeated freeze-thaw treatment. WH peptide-mediated DC targeting, in combination with the ferritin scaffold, enhances antigen uptake and DC maturation. In BALB/c mice, CpG and fullerenol dual-adjuvanted HER2_aHPF elicits robust HER2-specific humoral and cellular immunity, characterized by high-titer antibodies, polyfunctional CD4+ and CD8+ T cells, and expanded effector-memory T cells. Prophylactic and therapeutic vaccination markedly inhibits primary tumor growth and lung metastasis in mouse and human HER2-positive 4T1 models. Mechanistically, HER2_aHPF reduces myeloid-derived suppressor cells and regulatory T cells, increases cytotoxic T-cell infiltration, and maintains a favorable in vivo safety profile. Combination with anti-PD-1 and anti-CD47 antibodies further enhances T-cell activity and tumor control, demonstrating strong synergy between active vaccination and dual immune checkpoint blockade. These findings establish HER2_aHPF as a versatile nanoparticle vaccine platform with clinical translation potential for HER2-positive cancer immunotherapy.