Staphylococcal protein A inhibits complement activation by interfering with IgG hexamer formation

Cruz, Ana Rita; Boer, Maurits A. den; Strasser, Jürgen; Beurskens, Frank J.; Haas, Carla J. C. de; Aerts, Piet C.; Wang, G.; Jong, Rob N. de; Bagnoli, Fábio; Strijp, Jos A. G. van; Kessel, Kok P. M. van; Schuurman, Janine; Preiner, Johannes; Heck, Albert J. R.; Rooijakkers, Suzan H. M.

doi:10.1101/2020.07.20.212118

Cited by 5 publications

(17 citation statements)

References 83 publications

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“…In line with recent results, IgG1 and IgG3 antibodies against WTA elicit effective C3b deposition on S. aureus (Fig. 1A) 34 . Furthermore, IgG4 did not activate complement on S. aureus ( Fig.…”

Section: Igg-mediated Complement Activation Does Not Always Correlatesupporting

confidence: 92%

“…NheI and BsiWI were used as the 3' cloning sites for VH and VL, respectively, in order to preserve the immunoglobulin heavy and kappa light chain amino acid sequence. Sequences of IgG1, IgG2, IgG3, IgG4 variable and constant heavy and light chains were previously described 51,85 (Supplemental Table 1). VH and VL sequences were derived from previously described anti-WTA GlcNAc-β-4497 (anti-WTA-4497; based on patent WO/2014/193722) 86 and anti-DNP 87 (Supplemental Table 1).…”

Section: Conflict Of Interestmentioning

confidence: 99%

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C1q binding to surface-bound IgG is stabilized by C1r₂s₂proteases

Zwarthoff

Widmer

Kuipers

et al. 2021

Preprint

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Complement is an important effector mechanism for antibody-mediated clearance of infections and tumor cells. Upon binding to target cells, the antibody's constant (Fc) domain recruits complement component C1 to initiate a proteolytic cascade that generates lytic pores and stimulates phagocytosis. The C1 complex (C1qr2s2) consists of the large recognition protein C1q and a heterotetramer of proteases C1r and C1s (C1r2s2). While interactions between C1 and IgG-Fc's are believed to be mediated by the globular heads of C1q, we here find that C1r2s2 proteases affect the capacity of C1q to form an avid complex with surface-bound IgG molecules (on various DNP-coated surfaces and pathogenic Staphylococcus aureus). The extent to which C1r2s2 contribute to C1q-IgG stability strongly differs between human IgG subclasses. Using antibody engineering of monoclonal IgG we reveal that hexamer-enhancing mutations improve C1q-IgG stability, both in absence and presence of C1r2s2. In addition, hexamer-enhanced IgGs targeting S. aureus mediate improved complement-dependent phagocytosis by human neutrophils. Altogether, these molecular insights into complement binding to surface-bound IgGs could be important for optimal design of antibody therapies.

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Section: Igg-mediated Complement Activation Does Not Always Correlatesupporting

confidence: 92%

Section: Conflict Of Interestmentioning

confidence: 99%

C1q binding to surface-bound IgG is stabilized by C1r₂s₂proteases

Zwarthoff

Widmer

Kuipers

et al. 2021

Preprint

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“…This is due to an amino acid substitution in position 435, where an histidine in IgG1, IgG2 and IgG4 becomes an arginine in most of IgG3 allotypes (19, 20). Therefore, the effector functions of IgG3 remain unaffected by the presence of SpA (21).…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…We and others showed that SpA protects S. aureus from phagocytic killing by binding the IgG-Fc fragment (21–23). In our previous study, we unveiled how SpA blocks IgG-mediated complement activation and subsequent killing of S. aureus (21). We showed that SpA binds competitively to the Fc-Fc interaction interface on IgG monomers, which effectively prevents IgGs from forming IgG hexamers (21).…”

Section: Introductionmentioning

confidence: 99%

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Staphylococcal protein A inhibits IgG-mediated phagocytosis by blocking the interaction of IgGs with FcγRs and FcRn

Cruz

Bentlage

Blonk

et al. 2022

Preprint

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Immunoglobulin G molecules are crucial for the human immune response against bacterial infections. IgGs can trigger phagocytosis by innate immune cells, like neutrophils. To do so, IgGs should bind to the bacterial surface via their variable Fab regions and interact with Fcγ receptors (FcγRs) and complement C1 via the constant Fc domain. C1 binding to IgG-labeled bacteria activates the complement cascade, which results in bacterial decoration with C3-derived molecules that are recognized by complement receptors (CRs) on neutrophils. Next to FcγRs and CRs on the membrane, neutrophils also express the intracellular neonatal Fc receptor (FcRn). We previously reported that staphylococcal protein A (SpA), a key immune evasion protein of Staphylococcus aureus, potently blocks IgG-mediated complement activation and killing of S. aureus by interfering with IgG hexamer formation. SpA is also known to block IgG-mediated phagocytosis in absence of complement but the mechanism behind it remains unclear. Here we demonstrate that SpA blocks IgG-mediated phagocytosis and killing of S. aureus through inhibition of the interaction of IgGs with FcγRs (FcγRIIa and FcγRIIIb, but not FcγRI) and FcRn. Furthermore, our data show that multiple SpA domains are needed to effectively block IgG1-mediated phagocytosis. This provides a rationale for the fact that SpA from S. aureus contains four to five repeats. Taken together, our study elucidates the molecular mechanism by which SpA blocks IgG-mediated phagocytosis and supports the idea that next to FcγRs, also the intracellular FcRn receptor is essential for efficient phagocytosis and killing of bacteria by neutrophils.

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Engineered human antibodies for the opsonization and killing ofStaphylococcus aureus

Chen

Schneewind

Missiakas

2022

Proc. Natl. Acad. Sci. U.S.A.

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Gram-positive organisms with their thick envelope cannot be lysed by complement alone. Nonetheless, antibody-binding on the surface can recruit complement and mark these invaders for uptake and killing by phagocytes, a process known as opsonophagocytosis. The crystallizable fragment of immunoglobulins (Fcγ) is key for complement recruitment. The cell surface of S. aureus is coated with Staphylococcal protein A (SpA). SpA captures the Fcγ domain of IgG and interferes with opsonization by anti-S. aureus antibodies. In principle, the Fcγ domain of therapeutic antibodies could be engineered to avoid the inhibitory activity of SpA. However, the SpA-binding site on Fcγ overlaps with that of the neonatal Fc receptor (FcRn), an interaction that is critical for prolonging the half-life of serum IgG. This evolutionary adaptation poses a challenge for the exploration of Fcγ mutants that can both weaken SpA–IgG interactions and retain stability. Here, we use both wild-type and transgenic human FcRn mice to identify antibodies with enhanced half-life and increased opsonophagocytic killing in models of S. aureus infection and demonstrate that antibody-based immunotherapy can be improved by modifying Fcγ. Our experiments also show that by competing for FcRn-binding, staphylococci effectively reduce the half-life of antibodies during infection. These observations may have profound impact in treating cancer, autoimmune, and asthma patients colonized or infected with S. aureus and undergoing monoclonal antibody treatment.

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Staphylococcal protein A inhibits complement activation by interfering with IgG hexamer formation

Cited by 5 publications

References 83 publications

C1q binding to surface-bound IgG is stabilized by C1r₂s₂proteases

C1q binding to surface-bound IgG is stabilized by C1r₂s₂proteases

Staphylococcal protein A inhibits IgG-mediated phagocytosis by blocking the interaction of IgGs with FcγRs and FcRn

Engineered human antibodies for the opsonization and killing ofStaphylococcus aureus

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Staphylococcal protein A inhibits complement activation by interfering with IgG hexamer formation

Cited by 5 publications

References 83 publications

C1q binding to surface-bound IgG is stabilized by C1r2s2proteases

C1q binding to surface-bound IgG is stabilized by C1r2s2proteases

Staphylococcal protein A inhibits IgG-mediated phagocytosis by blocking the interaction of IgGs with FcγRs and FcRn

Engineered human antibodies for the opsonization and killing ofStaphylococcus aureus

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C1q binding to surface-bound IgG is stabilized by C1r₂s₂proteases

C1q binding to surface-bound IgG is stabilized by C1r₂s₂proteases