Improved immune response and anti-tumor effect of WT1 peptide emulsion adjuvant vaccine for acute myeloid leukemia

To evaluate the stability, safety and immune enhancement and anti-tumor effects of Wilms' tumor gene 1 (WT1) peptide combined with AddaVax^TM emulsion vaccine for acute myeloid leukemia.

The stability of WT1 peptide in the adjuvant vaccine was evaluated using MALDI-TOF-MS time-of-flight mass spectrometry. Female C57BL/6 mice were randomly divided into PBS group, WT1 peptide group, and WT1 peptide+AddaVax^TM emulsion adjuvant vaccine group. The immunization was performed at a dose of 50 μg/mouse for antigen and 50 μg/mouse for adjuvant, with intramuscular injection on days 0, 14, and 28. HE staining was used to assess the toxicity of intramuscular vaccination on mouse organ tissues. Cytokine levels were detected by ELISA, and the number of IFN-γ-secreting splenocytes was measured by ELISpot. Flow cytometry was employed to detect the maturation of bone marrow-derived dendritic cells (BMDCs) promoted by the vaccine in vitro and the promotion for lymphocyte activation, and H-2Db WT1 tetramer was utilized to detect the proportion of specific CD8⁺ T cells. After establishing a mouse leukemia tumor model using the C1498-mWT1 stable cell line, the anti-tumor effects of the vaccine for prevention and treatment were evaluated.

The WT1 peptide stably existed in the vaccine without causing significant organ tissue changes in mice after intramuscular injection. Compared to the mice immunized with WT1 aqueous solution, the mice after intramuscular injection of the WT1 peptide emulsion adjuvant vaccine showed stronger immune responses of Th1 cells, including IFN-γ and TNF-α, as well as Th17 cells of IL-17A (P<0.05), and the mice had not only promoted number of IFN-γ secreting splenocytes (P<0.01) but also enhanced maturation of BMDCs, as indicated by an increase in the proportions of CD40⁺/CD11c⁺ and CD86⁺CD80⁺/CD11c⁺ cells (P<0.05). Additionally, there were increases in both the proportion of CD4⁺/CD3⁺ T and CD69⁺/CD8⁺ T cells (P<0.05) and the proportion of specific CD8⁺ T cells (P<0.05). In the anti-tumor effect study using the C1498-mWT1 mouse model, the median survival time of the WT1+AddaVax^TM group was extended by 6 d compared to the WT1 aqueous solution group. At day 50, the survival rate of mice in the WT1+AddaVax^TM group was still 28.5%, while all mice in the other groups had died (P<0.05).

The vaccine with the WT1 peptide and AddaVax^TM emulsion adjuvant exhibits good immunological and anti-tumor effects.