196P - Local glycan engineering induces systemic antitumor immune reactions via antigen cross-presentation

Background

New therapies that aim to remodel the tumor glycosylation and reactivate the immune system are being explored. In particular, approaches that target the sialoglycan-Siglec as glyco-immune checkpoint.

Methods

An adeno-associated virus was constructed to express influenza A sialidase (AAVsia). Efficacy of sialidase production in transduced cells and activity were tested in vitro and mouse tumor models after intratumoral injection. Combination therapy with checkpoint inhibitors (PD-1 and CTLA-4) and FUCA-1 (human fucosidase) were performed. In addition, efficacy of immune reactivation against tumors and cancer control was tested in syngeneic mouse models. Immune reactions were further characterized by flow cytometry and single cell RNA sequencing. To access the impact of desialylation in cross-presentation, bone marrow derived dendritic cells were pulsed with cancer cells and co-cultured with OT-I cells with sialidase. Proliferation and activation were evaluated by flow cytometry.

Results

Upon AAV-sia treatment, cancer cells express sialidase on the cell surface and are able to cleave sialic acid in the tumor microenvironment in mouse models. We are further able to show an inhibitory effect on tumor growth and survival in syngeneic tumor models responsive and unresponsive to PD-1 blockade. A relevant synergism combining AAV-sia and anti-PD-1 treatment was observed. Combination with human fucosidase (FUCA-1), sialidase and PD-1 was able to increase survival and the rate of complete cure up to 36%.Mechanistic studies have demonstrated an increased activation of T cells, a polarization of myeloid cells towards an anti-tumor phenotype and an increase in conventional dendritic cell infiltration. In addition, scRNAseq data shows an up-regulation of M1-like genes. Despite local injection and desialylation, we observed also a growth inhibition on distant tumor sites and an increase in tumor-specific T cells suggesting a systemic immune activation. We observed that cross- presentation is increased upon sialidase treatment.

Conclusions

Taken together, AAV-sia removes the immune-suppressant carbohydrate sialic acid from the tumor microenvironment and cancer cells rendering them more vulnerable for destruction by immune cells.

Legal entity responsible for the study

The authors.

Funding

SNF and KLBB.

Disclosure

N. Rodrigues Mantuano: Financial Interests, Personal and Institutional, Member of Board of Directors: Glycocalyx. H. Läubli: Financial Interests, Personal and Institutional, Member of Board of Directors: Glycocalyx. All other authors have declared no conflicts of interest.