Bacillus Calmette-Guerin (BCG) induces superior anti-tumour responses by Vδ2+ T cells compared with the aminobisphosphonate drug zoledronic acid

γδ T cells and the PD-1/PD-L1 axis: a love-hate relationship in the tumor microenvironment

Gamma delta (γδ) T cells demonstrate strong cytotoxicity against diverse cancer cell types in an MHC-independent manner, rendering them promising contenders for cancer therapy. Although amplification and adoptive transfer of γδ T cells are being evaluated in the clinic, their therapeutic efficacy remains unsatisfactory, primarily due to the influence of the immunosuppressive tumor microenvironment (TME). Currently, the utilization of targeted therapeutic antibodies against inhibitory immune checkpoint (ICP) molecules is a viable approach to counteract the immunosuppressive consequences of the TME. Notably, PD-1/PD-L1 checkpoint inhibitors are considered primary treatment options for diverse malignancies, with the objective of preserving the response of αβ T cells. However, γδ T cells also infiltrate various human cancers and are important participants in cancer immunity, thereby influencing patient prognosis. Hence, it is imperative to comprehend the reciprocal impact of the PD-1/PD-L1 axis on γδ T cells. This understanding can serve as a therapeutic foundation for improving γδ T cells adoptive transfer therapy and may offer a novel avenue for future combined immunotherapeutic approaches.

Risedronate-functionalized manganese-hydroxyapatite amorphous particles: A potent adjuvant for subunit vaccines and cancer immunotherapy

The cGAS-STING pathway and the Mevalonate Pathway are druggable targets for vaccine adjuvant discovery. Manganese (Mn) and bisphosphonates are known to exert adjuvant effects by targeting these two pathways, respectively. This study found the synergistic potential of the two pathways in enhancing immune response. Risedronate (Ris) significantly amplified the Mn adjuvant early antibody response by 166-fold and fortified its cellular immunity. However, direct combination of Mn2+ and Ris resulted in increased adjuvant toxicity (40% mouse mortality). By the combination of doping property of hydroxyapatite (HA) and its high affinity for Ris, we designed Ris-functionalized Mn-HA micro-nanoparticles as an organic-inorganic hybrid adjuvant, named MnHARis. MnHARis alleviated adjuvant toxicity (100% vs. 60% survival rate) and exhibited good long-term stability. When formulated with the varicella-zoster virus glycoprotein E (gE) antigen, MnHARis triggered a 274.3-fold increase in IgG titers and a 61.3-fold surge in neutralization titers while maintaining a better long-term humoral immunity compared to the aluminum adjuvant. Its efficacy spanned other antigens, including ovalbumin, HPV18 VLP, and SARS-CoV-2 spike protein. Notably, the cellular immunity elicited by the group of gE + MnHARis was comparable to the renowned Shingrix®. Moreover, intratumoral co-administration with an anti-trophoblast cell surface antigen 2 nanobody revealed synergistic antitumor capabilities. These findings underscore the potential of MnHARis as a potent adjuvant for augmenting vaccine immune responses and improving cancer immunotherapy outcomes.

Releasing the restraints of Vγ9Vδ2 T-cells in cancer immunotherapy

Objectives

Vγ9Vδ2 T-cells are a subset of T-cells with a crucial role in immunosurveillance which can be activated and expanded by multiple means to stimulate effector responses. Little is known about the expression of checkpoint molecules on this cell population and whether the ligation of these molecules can regulate their activity. The aim of this study was to assess the expression of both activatory and inhibitory receptors on Vγ9Vδ2 T-cells to assess potential avenues of regulation to target with immunotherapy.

Methods

Expression of various activatory and inhibitory receptors was assessed on Vγ9Vδ2 T-cells by flow cytometry following activation and expansion using zoledronic acid (ZA) and Bacillus Calmette-Guérin (BCG). Expression of these markers and production of effector molecules was also examined following co-culture with various tumour cell targets. The effect of immune checkpoint blockade on Vγ9Vδ2 T-cells was also explored.

Results

Vγ9Vδ2 T-cells expressed high levels of activatory markers both at baseline and following stimulation. Vγ9Vδ2 T-cells expressed variable levels of inhibitory checkpoint receptors with many being upregulated following stimulation. Expression of these markers is further modulated upon co-culture with tumour cells with changes reflecting activation and effector functions. Despite their high expression of inhibitory receptors when cultured with tumour cells expressing cognate ligands there was no effect on Vδ2+ T-cell cytotoxic capacity or cytokine production with immune checkpoint blockade.

Conclusions

Our work suggests the expression of checkpoint receptors present on Vγ9Vδ2 T-cells which may provide a mechanism with the potential to be utilised by tumour cells to subvert Vγ9Vδ2 T-cell cytotoxicity. This work suggests important candidates for blockade by ICI therapy in order to increase the successful use of Vγ9Vδ2 T-cells in immunotherapy.

BCG-activation of leukocytes is sufficient for the generation of donor-independent innate anti-tumor NK and γδ T-cells that can be further expanded in vitro

Bacillus Calmette-Guérin (BCG), the nonpathogenic Mycobacterium bovis strain used as tuberculosis vaccine, has been successfully used as treatment for non-muscle invasive bladder cancer for decades, and suggested to potentiate cellular and humoral immune responses. However, the exact mechanism of action is not fully understood. We previously described that BCG mainly activated anti-tumor cytotoxic NK cells with upregulation of CD56 and a CD16⁺ phenotype. Now, we show that stimulation of human peripheral blood mononuclear cells with iBCG, a preparation based on BCG-Moreau, expands oligoclonal γδ T-cells, with a cytotoxic phenotype, together with anti-tumor CD56^high CD16⁺ NK cells. We have used scRNA-seq, flow cytometry, and functional assays to characterize these BCG-activated γδ T-cells in detail. They had a high IFNγ secretion signature with expression of CD27⁺ and formed conjugates with bladder cancer cells. BCG-activated γδ T-cells proliferated strongly in response to minimal doses of cytokines and had anti-tumor functions, although not fully based on degranulation. BCG was sufficient to stimulate proliferation of γδ T-cells when cultured with other PBMC; however, BCG alone did not stimulate expansion of purified γδ T-cells. The characterization of these non-donor restricted lymphocyte populations, which can be expanded in vitro, could provide a new approach to prepare cell-based immunotherapy tools.