RESUMO
Adjuvants for vaccines with characteristics of improving adaptive immunity particularly via leverage of antigen presenting cells (APCs) are currently lacking. In a previous work we obtained a new soluble 300 kDa homogeneous ß-glucan named GFPBW1 from the fruit bodies of Granola frondosa. GFPBW1 could activate macrophages by targeting dendritic cell associated C-type lectin 1 (Dectin-1)/Syk/NF-κB signaling to achieve antitumour effects. In this study the adjuvant effects of GFPBW1 were explored with OVA-antigen and B16-OVA tumor model. We showed that GFPBW1 (5, 50, 500 µg/mL) dose-dependently promoted activation and maturation of APCs in vitro by increasing CD80, CD86 and MHC II expression. We immunized female mice with OVA in combination with GFPBW1 (50 or 300 µg) twice with an interval of two weeks. GFPBW1 markedly and dose-dependently increased OVA-specific antibody titers of different subtypes including IgG1, IgG2a, IgG2b and IgG3, suggesting that it could serve as an adjuvant for both Th1 and Th2 type immune responses. Furthermore, GFPBW1 in combination with aluminum significantly increased the titers of OVA-specific IgG2a and IgG2b, but not those of IgG1, suggesting that GFPBW1 could be used as a co-adjuvant of aluminum to compensate for Th1 deficiency. For mice immunized with OVA plus GFPBW1, no obvious pathological injury was observed in either major organs or injection sites, and no abnormalities were noted for any of the hematological parameters. When GFPBW1 served as an adjuvant in the B16-OVA cancer vaccine models, it could accomplish entire tumor suppression with preventive vaccines, and enhance antitumour efficacy with therapeutic vaccines. Differentially expressed genes were found to be enriched in antigen processing process, specifically increased tumor infiltration of DCs, B1 cells and plasma cells in the OVA plus GFPBW1 group, in accordance with its activation and maturation function of APCs. Collectively, this study systematically describes the properties of GFPBW1 as a novel potent and safe adjuvant and highlights its great potential in vaccine development.
RESUMO
Inhibin beta A (INHBA) and its homodimer activin A have pleiotropic effects on modulation of immune responses and tumor progression, but it remains uncertain whether tumors may release activin A to regulate anti-tumor immunity. In this study we investigated the effects and mechanisms of tumor intrinsic INHBA on carcinogenesis, tumor immunity and PD-L1 blockade. Bioinformatic analysis on the TCGA database revealed that INHBA expression levels were elevated in 33 cancer types, including breast cancer (BRCA) and colon adenocarcinoma (COAD). In addition, survival analysis also corroborated that INHBA expression was negatively correlated with the prognosis of many types of cancer patients. We demonstrated that gain or loss function of Inhba did not alter in vitro growth of colorectal cancer CT26 cells, but had striking impact on mouse tumor models including CT26, MC38, B16 and 4T1 models. By using the TIMER 2.0 tool, we figured out that in most cancer types, Inhba expression in tumors was inversely associated with the infiltration of CD4+ T and CD8+ T cells. In CT26 tumor-bearing mice, overexpression of tumor INHBA eliminated the anti-tumor effect of the PD-L1 antibody atezolizumab, whereas INHBA deficiency enhanced the efficacy of atezolizumab. We revealed that tumor INHBA significantly downregulated the interferon-γ (IFN-γ) signaling pathway. Tumor INHBA overexpression led to lower expression of PD-L1 induced by IFN-γ, resulting in poor responsiveness to anti-PD-L1 treatment. On the other hand, decreased secretion of IFN-γ-stimulated chemokines, including C-X-C motif chemokine 9 (CXCL9) and 10 (CXCL10), impaired the infiltration of effector T cells into the tumor microenvironment (TME). Furthermore, the activin A-specific antibody garetosmab improved anti-tumor immunity and its combination with the anti-PD-L1 antibody atezolizumab showed a superior therapeutic effect to monotherapy with garetosmab or atezolizumab. We demonstrate that INHBA and activin A are involved in anti-tumor immunity by inhibiting the IFN-γ signaling pathway, which can be considered as potential targets to improve the responsive rate of PD-1/PD-L1 blockade.