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We report a systematic study of the rhenium-based borides, ReB 2 , Re 7 B 3 , and Re 3 B, by means of the 11 B nuclear magnetic resonance ͑NMR͒ spectroscopy. While Re 7 B 3 and Re 3 B are superconductors, ReB 2 exhibits no superconducting signature but is of current interest due to its superhard mechanical property. Since the major focus of this investigation is their electronic characteristics in the normal states, we performed the measurements at temperatures between 77 and 295 K. For Re 7 B 3 and Re 3 B, s-character electrons were found to be responsible for the observed 11 B NMR Knight shift and spin-lattice relaxation rate ͑1 / T 1 ͒. From T 1 analysis, we thus deduce the partial B s Fermi-level density of states ͑DOS͒ of both borides. On the other hand, the relaxation rate of ReB 2 is mainly associated with p electrons, similar to the cases of OsB 2 and RuB 2 . In addition, the extracted B 2p Fermi-level DOS is in good agreement with the theoretical prediction from band-structure calculations.

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Background Neoantigens are considered ideal targets for immunotherapy, especially tumor vaccine, because of their strong specificity and immunogenicity. Here, we developed a neoantigen nanovaccine used liposomes with lymph-node targeting characteristic. Methods Our nanovaccine was composed of neoantigens, an amphiphilic liposome and an adjuvant Montanide™ ISA 51. Small animal imaging system and immunofluorescence staining were used to identify the distribution of nanovaccines. A subcutaneous-tumor-resection mouse model of melanoma was established to evaluate the anti-tumor efficacy. Flow cytometry was performed to assay the immune responses initiated by nanovaccines. Results Nanovaccines could traffic to lymph nodes, be uptaken by CD11c+ DCs and promote DCs maturity. After the treatment of our neoantigen nanovaccines, the average recurrence time was extended from 11 to 16 days and the median survival time was even prolonged 7.5 days relative to the control group (NS group). Nanovaccines increased neoantigen-specific T cells to 10-fold of free vaccines, and upregulated Th1 cytokines, such as IFN-γ and TNF-α. The anti-tumor activity of spleen lymphocytes in the nanovaccine group was significantly stronger than that of other groups. However, some immune-inhibitory cells or molecules in tumor microenvironment have been detected upregulated under the immune pressure of neoantigen nanovaccines, such as Tregs and PD-L1. The efficacy of the neoantigen nanovaccine combined with anti-PD1 antibody or Treg inhibiting peptide P60 was better than that of the single treatment. Conclusions We developed a general vaccine strategy, triggering specific T cell responses, and provided feasible combination strategies for better anti-tumor efficacy. Graphical abstract

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