Artificial Membrane-Binding Proteins to improve the performance of immune cell therapies in cancer.

Abstract

Recognition of the immune system’s pivotal role in controlling cancer has driven immunotherapy development to enhance antitumour responses. Cell-based immunotherapies have revolutionized hematologic cancer treatment but remain limited in solid tumours due to the immunosuppressive tumour microenvironment (TME). Within the TME, natural killer (NK) cells—key mediators of antitumour immunity—are impaired by hypoxia, cytokine sinks, and inhibitory signals.

This thesis introduces a novel strategy to enhance immune cell function by functionalizing NK cells with hyaluronic acid (HA) conjugated to cytokine-containing artificial membrane-binding proteins (AMBPs). While HA is widely used for tumour-targeted drug delivery, its potential as a live cell coating remains underexplored. By covalently linking HA to bi-functional AMBPs, this approach offers a flexible, potentially safer alternative to genetic modification, while preserving cell viability and function. Tested on NK cells, the method demonstrates promise and could be adapted for other immune and therapeutic cell types.

An optimized fusion protein system was engineered by integrating interleukin-15 (IL-15), crucial for NK cell activation and survival, with a supercharged myoglobin variant (MyoE9) developed for enhanced membrane retention and bioactivity. Structural and functional analyses confirmed that both domains remain functional post-fusion, with IL-15 retaining its bioactivity after HA conjugation. Importantly, ~40% of NK-92 cells were successfully coated within 24 hours, maintaining viability comparable to untreated NK-92 cells, which exhibited only 9% coating in flow cytometry experiments. This highlights the role of HA conjugation in facilitating the successful membrane display of AMBPs.

Functional assays further demonstrated that [HA][IL15_MyoE9]-coated NK cells retained potent cytotoxicity against MDA-MB-231 breast cancer cells, suggesting a promising tumour-targeting mechanism via HA-CD44 interactions. With further optimisation, this modular strategy offers a versatile platform for enhancing cell-based therapies against solid tumours.

Date of Award	30 Sept 2025
Original language	English
Awarding Institution	University of Bristol
Supervisor	Laura Rivino (Supervisor) & Adam W Perriman (Supervisor)