An engineered immunomodulatory IgG1 Fc suppresses autoimmune inflammation through pathways shared with i.v. immunoglobulin
Sunny L. Sneed, Brian B. Reese, Ana F.S. Laureano, Sneha Ratnapriya, Isabella Fraschilla, Kate L. Jeffrey, Greg P. Coffey, Pamela B. Conley, Robert M. Anthony
Sunny L. Sneed, Brian B. Reese, Ana F.S. Laureano, Sneha Ratnapriya, Isabella Fraschilla, Kate L. Jeffrey, Greg P. Coffey, Pamela B. Conley, Robert M. Anthony
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Research Article Immunology

An engineered immunomodulatory IgG1 Fc suppresses autoimmune inflammation through pathways shared with i.v. immunoglobulin

Abstract

Immunoglobulin G (IgG) antibodies in the form of high-dose intravenous immunoglobulin (IVIG) exert immunomodulatory activity and are used in this capacity to treat inflammatory and autoimmune diseases. Reductionist approaches have revealed that terminal sialylation of the single asparagine-linked (N-linked) glycan at position 297 of the IgG1 Fc bestows antiinflammatory activity, which can be recapitulated by introduction of an F241A point mutation in the IgG1 Fc (FcF241A). Here, we examined the antiinflammatory activity of CHO-K1 cell–produced FcF241A in vivo in models of autoimmune inflammation and found it to be independent of sialylation. Intriguingly, sialylation markedly improved the half-life and bioavailability of FcF241A via impaired interaction with the asialoglycoprotein receptor ASGPR. Further, FcF241A suppressed inflammation through the same molecular pathways as IVIG and sialylated IgG1 Fc and required the C-type lectin SIGN-R1 in vivo. This contrasted with FcAbdeg (efgartigimod), an engineered IgG1 Fc with enhanced neonatal Fc receptor (FcRn) binding, which reduced total serum IgG concentrations, independent of SIGN-R1. When coadministered, FcF241A and FcAbdeg exhibited combinatorial antiinflammatory activity. Together, these results demonstrated that the antiinflammatory activity of FcF241A requires SIGN-R1, similarly to that of high-dose IVIG and sialylated IgG1, and can be used in combination with other antiinflammatory therapeutics that rely on divergent pathways, including FcAbdeg.

Authors

Sunny L. Sneed, Brian B. Reese, Ana F.S. Laureano, Sneha Ratnapriya, Isabella Fraschilla, Kate L. Jeffrey, Greg P. Coffey, Pamela B. Conley, Robert M. Anthony

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Figure 3

Divergent antiinflammatory pathways are elicited by FcF241A/B4ST6 and FcAbdeg.

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Divergent antiinflammatory pathways are elicited by FcF241A/B4ST6 and Fc...
(A) Sequence alignment and schematics of FcWT and FcAbdeg, with the gray boxes designating the locations of Abdeg mutations and the black box designating the location of N297. (B) Dissociation constants (KD, μM) and association constants (KA, M–1 s–1) determined by surface plasmon resonance (SPR) of FcWT, FcF241A/B4ST6, and FcAbdeg with mFcRn and hFcRn are plotted. (C) Female WT C57BL/6 (n = 3–9) and humanized homozygous FcRn (Tg32) mice (n = 3–4) were given 1 dose of 50 or 100 mg/kg of FcF241A/B4ST6 or 10 mg/kg of FcAbdeg, and serum mouse IgG was measured via ELISA out to day 7 post-dose. (D) Fold change of cell surface binding MFI of PBS, FcF241A/B4ST6, FcF241A/siSLC, or FcAbdeg to SIGN-R1+/+, SIGN-R1–/–, and hDC-SIGN+/SIGN-R1–/– murine bone marrow–derived macrophages (BMDMs) as detected by FACS. Plot shows the fold change in binding, represented as MFI, in comparison with PBS. (E) Female WT C57BL/6 mice (n = 5 per group) and female and male SIGN-R1–/– mice (n = 5) were given arthritogenic K/BxN serum alongside PBS, IVIG 1 g/kg, FcF241A/B4ST6 50 mg/kg, or FcAbdeg 10 mg/kg in a preventative manner, and joint swelling was clinically scored for 10 days. Day 7 clinical scores for each group, representing the maximum separation in clinical score between PBS and FcF241A-based treatments, are plotted. Bar graphs are plotted as means with SDs, and statistics are ordinary 1-way ANOVA with Tukey’s multiple comparisons in B, D, and E.