Crystallographic approaches to study the interaction modes of PD-1- and CTLA-4-blocking antibodies

Abstract

The programmed death 1 (PD-1) and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) are negative regulators of T-cell immune function. Removal of these "brakes" in T cells results in increased activation of the immune system and controlling and eradicating tumor. The development of immune checkpoint inhibitors (ICIs) is a revolutionary milestone in tumor immunotherapy. Obtaining the atomic structure of the human immune checkpoint receptor/ICI therapeutic antibody complex is essential for understanding its inhibition mechanism and the rational design of improved biotherapeutics. In this chapter, we describe the methods for efficient production of extracellular domain of human immune checkpoint receptors and Fv fragments of ICI therapeutic antibodies in milligram quantities sufficient for structural studies, taking examples of the PD-1/pembrolizumab Fv and CTLA-4-ipilimumab Fv complexes.

Keywords: Crystallography; Cytotoxic T-lymphocyte–associated antigen 4 (CTLA-4); Fv fragment; Immune checkpoint inhibitors (ICIs); Programmed death 1 (PD-1); Secretory expression; Therapeutic antibody.