Structure and characterization of a high affinity C5a monoclonal antibody that blocks binding to C5aR1 and C5aR2 receptors

Abstract

C5a is a potent anaphylatoxin that modulates inflammation through the C5aR1 and C5aR2 receptors. The molecular interactions between C5a–C5aR1 receptor are well defined, whereas C5a–C5aR2 receptor interactions are poorly understood. Here, we describe the generation of a human antibody, MEDI7814, that neutralizes C5a and C5adesArg binding to the C5aR1 and C5aR2 receptors, without affecting complement–mediated bacterial cell killing. Unlike other anti–C5a mAbs described, this antibody has been shown to inhibit the effects of C5a by blocking C5a binding to both C5aR1 and C5aR2 receptors. The crystal structure of the antibody in complex with human C5a reveals a discontinuous epitope of 22 amino acids. This is the first time the epitope for an antibody that blocks C5aR1 and C5aR2 receptors has been described, and this work provides a basis for molecular studies aimed at further understanding the C5a–C5aR2 receptor interaction. MEDI7814 has therapeutic potential for the treatment of acute inflammatory conditions in which both C5a receptors may mediate inflammation, such as sepsis or renal ischemia–reperfusion injury.

C5a anaphylatoxin and its role in critical illness‐induced organ dysfunction

“…From the conflicting data presented, it is difficult to make generalisations about the relative role of C5aR2, and indeed any effects are almost certainly context‐dependent. The advent of new tools that allow us to target C5a‐C5aR1/2 interactions selectively will undoubtedly shed light on these complexities . A recent review by Zhang and colleagues provides further detail on this subject …”

“…Newer monoclonal antibodies which selectively target C5aR1 and/or 2 without inhibiting membrane attack complex formation are currently in various stages of development for indications as diverse as macular degeneration and vasculitis . Of key relevance to critical illness is IFX‐1, a monoclonal antibody which has enjoyed success in phase II dose‐escalation trials for early sepsis‐induced organ dysfunction, although full trial results have not yet been reported .…”

“…The advent of new tools that allow us to target C5a-C5aR1/2 interactions selectively will undoubtedly shed light on these complexities. 55,56 A recent review by Zhang and colleagues provides further detail on this subject. 57…”

“…115 Newer monoclonal antibodies which selectively target C5aR1 and/or 2 without inhibiting membrane attack complex formation are currently in various stages of development for indications as diverse as macular degeneration and vasculitis. 56,[116][117][118] Of key relevance to critical illness is IFX-1, a monoclonal antibody which has enjoyed success in phase II dose-escalation trials for early sepsisinduced organ dysfunction, although full trial results have not yet been reported. 119 Going forward, we suggest that the following points are of critical importance if newer therapeutic options are to be successfully licensed for use in critically ill patients: drug design must be informed by a detailed understanding of the underlying biology in the context of critically ill humans including time courses of responses, the inflammatory signalling network in which the target operates and clinically useable immunophenotyping tools.…”

A sound strategy for homology modeling-based affinity maturation of a HIF-1α single-domain intrabody

“…Display methods are used to improve affinity of antibodies via affinity maturation in vitro. Nevertheless, they are laborious and time-consuming (10)(11)(12). In these cases, developing a technological platform for high-efficiency affinity maturation of nanobodies is an urgent problem that must be solved.…”