Functional and Structural Characterization of a Potent C1q Inhibitor Targeting the Classical Pathway of the Complement System

TY - JOUR

T1 - Functional and Structural Characterization of a Potent C1q Inhibitor Targeting the Classical Pathway of the Complement System

AU - Laursen, Nick S.

AU - Pedersen, Dennis V.

AU - Gytz, Heidi

AU - Zarantonello, Alessandra

AU - Bernth Jensen, Jens Magnus

AU - Hansen, Annette G.

AU - Thiel, Steffen

AU - Andersen, Gregers R.

PY - 2020

Y1 - 2020

N2 - The classical pathway of complement is important for protection against pathogens and in maintaining tissue homeostasis, but excessive or aberrant activation is directly linked to numerous pathologies. We describe the development and in vitro characterization of C1qNb75, a single domain antibody (nanobody) specific for C1q, the pattern recognition molecule of the classical pathway. C1qNb75 binds to the globular head modules of human C1q with sub-nanomolar affinity and impedes classical pathway mediated hemolysis by IgG and IgM. Crystal structure analysis revealed that C1qNb75 recognizes an epitope primarily located in the C1q B-chain that overlaps with the binding sites of IgG and IgM. Thus, C1qNb75 competitively prevents C1q from binding to IgG and IgM causing blockade of complement activation by the classical pathway. Overall, C1qNb75 represents a high-affinity nanobody-based inhibitor of IgG- and IgM-mediated activation of the classical pathway and may serve as a valuable reagent in mechanistic and functional studies of complement, and as an efficient inhibitor of complement under conditions of excessive CP activation.

AB - The classical pathway of complement is important for protection against pathogens and in maintaining tissue homeostasis, but excessive or aberrant activation is directly linked to numerous pathologies. We describe the development and in vitro characterization of C1qNb75, a single domain antibody (nanobody) specific for C1q, the pattern recognition molecule of the classical pathway. C1qNb75 binds to the globular head modules of human C1q with sub-nanomolar affinity and impedes classical pathway mediated hemolysis by IgG and IgM. Crystal structure analysis revealed that C1qNb75 recognizes an epitope primarily located in the C1q B-chain that overlaps with the binding sites of IgG and IgM. Thus, C1qNb75 competitively prevents C1q from binding to IgG and IgM causing blockade of complement activation by the classical pathway. Overall, C1qNb75 represents a high-affinity nanobody-based inhibitor of IgG- and IgM-mediated activation of the classical pathway and may serve as a valuable reagent in mechanistic and functional studies of complement, and as an efficient inhibitor of complement under conditions of excessive CP activation.

KW - antibody

KW - C1q

KW - complement system

KW - crystal structure

KW - inhibitor

KW - nanobody

UR - http://www.scopus.com/inward/record.url?scp=85087769491&partnerID=8YFLogxK

U2 - 10.3389/fimmu.2020.01504

DO - 10.3389/fimmu.2020.01504

M3 - Journal article

C2 - 32849513

AN - SCOPUS:85087769491

SN - 1664-3224

VL - 11

JO - Frontiers in Immunology

JF - Frontiers in Immunology

M1 - 1504

ER -