Introduction: Tumor-associated macrophages (TAMs) promote immunosuppression, hindering immune checkpoint blockade and immunotherapy efficacy. To overcome this, we developed a novel multifunctional nanovaccine based on hepatitis B core virus-like particles (HBc VLP) to synergistically remodel the immunosuppressive tumor microenvironment through integrated TAM reprogramming and B7-H3 checkpoint blockade. Methods: The core VLP co-displayed tumor antigen peptide MAGE-A10 and TAM-targeting peptide M2pep via fusion expression. Immunostimulatory CpG oligodeoxynucleotide 1826 (CpG) was encapsulated within VLP. Anti-B7-H3 antibody (αB7-H3) and polyethylene glycol (PEG) were chemically conjugated to the surface for checkpoint blockade and prolonged circulation, forming CpG@VLP-αB7-H3-PEG. Results: Structural characterization using transmission electron microscopy and dynamic light scattering confirmed the hollow spherical self-assembly of VLP. Nanovaccines efficiently targeted TAMs in vitro and in vivo. Following CpG encapsulation (5.60 μg/mg), the nanovaccine reprogrammed M2-like TAMs into an M1-like phenotype. This was achieved by elevating the M1/M2 ratios of CD86/CD206 and MHC II/CD206 to 15.50-fold and 3.11-fold, respectively, as determined by flow cytometry. Further conjugation of αB7-H3 (250 μg/mg) significantly enhanced T-cell activation in TAM-T cell co-culture assays. In B16-F10 melanoma-bearing mice, reprogrammed iNOS⁺ M1-like macrophages triggered robust antitumor immunity, achieving a tumor inhibition rate of 63.47%. These macrophages also function as antigen-presenting cells and increase the proportion of tumor-infiltrating Granzyme B⁺CD8⁺ T cells. αB7-H3 conjugation further boosted infiltrating immune cells, M1-like macrophages, activated CD69⁺CD4⁺/CD8⁺ T cells, and cytotoxic T lymphocytes. PEGylation amplified systemic tumor-specific immunity and increased tumor inhibition by 80.12%. Conclusion: This HBc VLP-based nanovaccine constitutes a pioneering multifunctional platform designed to overcome TAM-mediated immunosuppression through synergistic integration of three modalities: antigen presentation, TAM phenotype reprogramming, and B7-H3 checkpoint blockade. To the best of our knowledge, this is the first nanovaccine architecture to enable coordinated immunomodulation. Its modular design supports the clinical translation of solid tumors and personalized immunotherapy.

Nano-adjuvant vaccines could induce immune responses and enhance immunogenicity. However, the application and manufacturing of nano-adjuvant is hampered by its challenging scale-up, poor reproducibility, and low security. Therefore, the present study aimed to optimize the preparation nanoparticles (NPs) using FDA-approved biopolymer materials poly(lactic acid) (PLA) and cationic lipid didodecyl-dimethyl-ammonium bromide (DDAB), develop the scale-up process, and evaluate the stability and biosafety of it. The optimum preparation conditions of DDAB/PLA NPs on a small scale were as follows: DDAB amount of 30 mg, aqueous phase volume of 90 mL, stirring rate at 550 rpm, and solidifying time of 12 h. Under the optimum conditions, the size of the NPs was about 170 nm. In scale-up preparation experiments, the vacuum rotary evaporation of 6 h and the Tangential flow ultrafiltration (TFU) method were the optimum conditions. The results suggested that DDAB/PLA NPs exhibited a uniform particle size distribution, with an average size of 150.3 ± 10.4 nm and a narrow polydispersity index (PDI) of 0.090 ± 0.13, coupled with a high antigen loading capacity of 85.4 ± 4.0%. In addition, the DDAB/PLA NPs can be stored stably for 30 days and do not have side effects caused by residual solvents. For biosafety, the acute toxicity experiments showed good tolerance of the vaccine formulation even at a high adjuvant dose. The local irritation experiment demonstrated the reversibility of muscular irritation, and the repeated toxicity experiment revealed no significant necrosis or severe lesions in mice injected with the high-dose vaccine formulation. Overall, the DDAB/PLA NPs exhibit potential for clinical translation as a safe candidate vaccine adjuvant.

Acute myeloid leukemia (AML) remains challenging due to chemotherapeutic drug-resistance (CDR). Aberrant expression B7 family proteins are involved in tumors evasion. We wonder whether B7 family protein alteration in AML CDR further supports tumor escape. Here, we establish AML cytarabine-resistant cell line U937/Ara-C and report on the expression MHC molecule and B7 family member. HLA-ABC was highly expressed similarly on both cell lines. MIC (MHC class I chain related) A/B and B7-H6 was moderately expressed on the surface of U937 and decreased dramatically by U937/Ara-C. In contrast, enhanced expression of B7-H1 and B7-H7 by U937/Ara-C was observed. HLA-DR and other B7 family members including CD80, CD86, B7-DC, B7-H2, B7-H3, B7-H4, and B7-H5 were not detected by both cell lines. Compared co-cultured with U937, peripheral blood mononuclear cells showed a decreased cytotoxicity when incubated with U937/Ara-C, as indicated by decreased levels of granzyme B and perforin production, accompanied with less TNF-α and lactate dehydrogenase secretion. In conclusion, AML CDR further evades the anti-tumor immune response which may through MHC molecule and B7 family members.