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

Laursen, N.S.; Pedersen, Dennis; Gytz, Heidi; Zarantonello, Alessandra; Jensen, Jens Magnus Bernth; Hansen, Annette G.; Thiel, Steffen; Andersen, Gregers Rom

doi:10.3389/fimmu.2020.01504

Cited by 27 publications

(41 citation statements)

References 78 publications

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“…To clarify whether complement activation by IgG anti-αGal proceeded through the CP, we tested the effect of including the C1qNb75 nanobody, which binds the globular heads of C1q and inhibits C1q docking to immunoglobulin. 28 C1qNb75 abrogated deposition to levels that could not be distinguished from the background (i.e. a control without added HHS) ( Fig.…”

Section: Igg Anti-αgal Activates the Complement Cp On Pig Red Blood Cmentioning

confidence: 99%

“…26 Nanobodies were derived from heavy-chain antibodies from llamas, selected by phage display, expressed in bacteria and purified as described previously. 27 Four nanobodies were used: (i) C1qNb75 binds to the globular head of C1q, blocking C1q docking to immunoglobulin Fc domains; 28 (ii) hC3Nb1 binds C3, selectively blocking the C3 convertase of the alternative pathway (AP); ,27 (iii) hC3Nb2 binds C3, blocking both the CP and AP C3 convertases; 29 and (iv) KRA152, which was used as control.…”

Section: Complement Deposition On Cells and Inhibition Of Complement mentioning

confidence: 99%

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Complement activation by human IgG antibodies to galactose‐α‐1,3‐galactose

et al. 2020

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Summary Some human antibodies may paradoxically inhibit complement activation on bacteria and enhance pathogen survival in humans. This property was also claimed for IgG antibodies reacting with terminal galactose‐α‐1,3‐galactose (Galα3Gal; IgG anti‐αGal), a naturally occurring and abundant antibody in human plasma that targets numerous different pathogens. To reinvestigate these effects, we used IgG anti‐αGal affinity isolated from a pool of normal human IgG and human hypogammaglobulinaemia serum as a complement source. Flow cytometry was performed to examine antibody binding and complement deposition on pig erythrocytes, Escherichia coli O86 and Streptococcus pneumoniae serotype 9V. Specific nanobodies were used to block the effect of single complement factors and to delineate the complement pathways involved. IgG anti‐αGal was capable of activating the classical complement pathway on all the tested target cells. The degree of activation was exponentially related to the density of bound antibody on E. coli O86 and pig erythrocytes, but more linearly on S. pneumoniae 9V. The alternative pathway of complement amplified complement deposition. Deposited C3 fragments covered the activating IgG anti‐αGal, obstructing its detection and highlighting this as a likely general caveat in studies of antibody density and complement deposition. The inherent capacity for complement activation by the purified carbohydrate reactive IgG anti‐αGal was similar to that of normal human IgG. We propose that the previously reported complement inhibition by IgG anti‐αGal relates to suboptimal assay configurations, in contrast to the complement activating property of the antibodies demonstrated in this paper.

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Section: Igg Anti-αgal Activates the Complement Cp On Pig Red Blood Cmentioning

confidence: 99%

Section: Complement Deposition On Cells and Inhibition Of Complement mentioning

confidence: 99%

Complement activation by human IgG antibodies to galactose‐α‐1,3‐galactose

et al. 2020

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“…An additional intriguing observation was that hC3Nb3 inhibited the formation of the C5b-9 complex upon activation of both CP and LP, which was unexpected since hC3Nb3 did not affect C3 deposition by the CP C3 convertase [5] ( Figure 5B). To gain further insight into the apparent inhibition of the CP/LP C5 convertase, the effect of the nanobody on CP mediated lysis of sheep erythrocytes was tested.…”

Section: Hc3nb3 Provides Insight Into the Role Of C3b In C5 Convertasesmentioning

confidence: 88%

“…The C1q specific nanobody C1qNb75 was selected from a phage display library generated after immunization of a lama with human C1q [5]. C1qNb75 was chosen among a panel of C1q specific nanobodies based on its ability to inhibit CP activation by IgG when analyzed in C4 and C3 fragment deposition assays ( Figure 3A).…”

Section: C1qnb75 Inhibits Initiation Of the Classical Pathwaymentioning

confidence: 99%

“…In accordance with the inhibition of C3 deposition, C1qNb75 also prevented hemolysis (Figure 3B). Finally, to obtain the structural basis for C1qNb75 inhibition of the CP, we determined the structure of the nanobody in complex with the C1q globular domain[5]. The resulting crystal structure determined at 2.2 Å resolution demonstrated that C1qNb75 binds to chain B and chain C of C1q and revealed that C1qNb75 acts by imposing steric hindrance on the C1q globular domain such that the interaction with the Fc of IgG and IgM is prevented (Figure 3C-E).…”

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Nanobodies Provide Insight Into the Molecular Mechanisms of the Complement Cascade and Offer New Therapeutic Strategies

Zarantonello¹,

Pedersen²,

Laursen³

et al. 2021

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The complement system is part of the innate immune response, where it provides immediate protection from infectious agents and plays a fundamental role in homeostasis. Complement dysregulation occurs in several diseases, where the tightly regulated proteolytic cascade turns offensive. Prominent examples are atypical hemolytic uremic syndrome, paroxysmal nocturnal hemoglobinuria and Alzheimer’s disease. Therapeutic intervention targeting complement activation may allow treatment of such debilitating diseases. In this review, we describe a panel of complement targeting nanobodies that allow modulation at different steps of the proteolytic cascade, from the activation of the C1 complex in the classical pathway to formation of the C5 convertase in the terminal pathway. Thorough structural and functional characterization has provided a deep mechanistic understanding of the mode of inhibition for each of the nanobodies. These complement specific nanobodies are novel powerful probes for basic research and offer new opportunities for in vivo complement modulation.

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An in‐depth analysis of the immunomodulatory mechanisms of intervertebral disc degeneration

et al. 2022

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Intervertebral disc degeneration (IVDD) is the pathological basis of disc herniation, spinal stenosis, and other related diseases, and the lower back pain it produces lays a heavy financial burden on individuals and society. Thus, it is essential to comprehend IVDD's pathophysiology. Numerous factors, such as inflammatory factors, oxidative stress, apoptosis, matrix metalloproteinases, are linked to IVDD pathogenesis.Despite the fact that many researches has provided explanations for the pathophysiology of IVDD, these studies are typically singular, restricted, and isolated, expound only on one or two components, and do not systematically analyze and summarize the numerous influencing elements. In addition, we discovered that the incidence of many chronic diseases in the field of orthopedics may be thoroughly and systematically defined in terms of immunological systems. In order to provide a theoretical foundation for an in-depth understanding of the pathological process of IVDD and the formulation of more effective prevention and treatment measures, this review provides a comprehensive and systematic account of the pathogenesis of IVDD from the physical to the molecular barriers of the intervertebral disc, from the nucleus pulposus tissue to the cellular to the immune-molecular level.

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

Cited by 27 publications

References 78 publications

Complement activation by human IgG antibodies to galactose‐α‐1,3‐galactose

Complement activation by human IgG antibodies to galactose‐α‐1,3‐galactose

Nanobodies Provide Insight Into the Molecular Mechanisms of the Complement Cascade and Offer New Therapeutic Strategies

An in‐depth analysis of the immunomodulatory mechanisms of intervertebral disc degeneration

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