Immune cell surface receptors are key regulators of immune activation and inhibition and represent attractive targets for immunotherapies. Therapeutic strategies such as immune cell engagers and checkpoint inhibitors require proteins that bind immune receptors with controlled affinities and specificities. However, there remains a strong demand for efficient systems to generate and characterise such receptor-binding proteins.
Nanobodies are small, stable antibody fragments with high epitope specificities that are well suited for immunotherapeutic applications. We have established a nanobody discovery workflow to generate nanobody binders against immune receptors using the Kruse yeast surface display platform (McMahon et al., 2018). This approach enabled efficient selection of candidate binders from the Kruse yeast library for immune receptor targeting. After target receptor protein expression, magnetic and fluorescence-activated cell sorting (MACS/FACS) are used to select and enrich yeast cells that display receptor-binding nanobodies.
Ongoing work focuses on biophysical and structural characterisation of nanobody-receptor binding. Binding affinity and kinetics will be assessed using surface plasmon resonance (SPR), while X-ray crystallography will be employed to define structural interfaces. In parallel, cell surface expression studies will evaluate nanobody functionality in a cellular context. Together, this work presents a system for identifying immune receptor-binding nanobodies, supporting the development of novel tools and therapeutics for immune cell engagement and checkpoint modulation.