Fully recombinant IgG2a Fc multimers (stradomers) effectively treat collagen-induced arthritis and prevent idiopathic thrombocytopenic purpura in mice

Abstract

IntroductionSoluble immune aggregates bearing intact Fc fragments are effective treatment for a variety of autoimmune disorders in mice. The better to understand the mechanisms by which Fc-bearing immune complexes suppress autoimmunity, and to develop a platform for clinical translation, we created a series of fully recombinant forms of polyvalent IgG2a Fc, termed stradomers, and tested their efficacy in a therapeutic model of collagen-induced arthritis (CIA) and preventive models of both idiopathic thrombocytopenic purpura (ITP) and graft-versus-host disease (GVHD).MethodsStradomers were created by engineering either the human IgG2 hinge sequence (IgG2H) or the isoleucine zipper (ILZ) onto either the carboxy or amino termini of murine IgG2a Fc. Multimerization and binding to the canonical Fc receptors and the C-type lectin SIGN-RI were evaluated by using sodium dodecylsulfate-polymerase chain reaction (SDS-PAGE) and Biacore/Octet assays. The efficacy of stradomers in alleviating CIA and preventing ITP and GVHD was compared with "gold standard" therapies, including prednisolone and intravenous immune globulin (IVIG).ResultsStradomers exist as both homodimeric and highly ordered sequential multimers. Higher-order multimers demonstrate increasingly stable associations with the canonic Fcγ receptors (FcγRs), and SIGN-R1, and are more effective than Fc homodimers in treating CIA. Furthermore, stradomers confer partial protection against platelet loss in a murine model ITP, but do not prevent GVHD.ConclusionThese data suggest that fully human stradomers might serve as valuable tools for the treatment of selected autoimmune disorders and as reagents to study the function of Fc:FcR interactions in vivo.

Anti-CD20 Antibody with Multimerized Fc Domains: A Novel Strategy To Deplete B Cells and Augment Treatment of Autoimmune Disease

“…However, the concentrations of GB4542 required to mediate these inhibitory effects were ∼100 times lower than those of IVIG. These data may reflect the fact that IVIG contains only a small portion of multimerized IgGs and are consistent with our animal data in which stradomers could treat or protect animals from autoimmune diseases at a significantly lower dose than IVIG (25). Similarly, although GB2542 blocked Fc multimer binding to all of the low-moderateaffinity human FcgRs tested, IVIG was less effective in blocking FcgRIIb interactions.…”

“…1A) (33-36). We previously used this strategy to generate recombinant murine IgG Fc multimers and a recombinant anti-human EGFR sAb (25,28). SDS-PAGE analysis proved that the resultant protein, GB4542, exists as a homodimer and higher-order multimers.…”

“…The amino acid sequence for rituximab was obtained from the ImMunoGeneTics database (http://www.imgt.org), and DNA fragments were synthesized at Blue Heron Biotechnology (Bothell, WA). G001, recombinant human IgG1 Fc; GL-2045, recombinant human IgG1 multimer; GB2500, recombinant anti-Her-2 mAb; and GB2542, recombinant anti-Her-2 sAb were all prepared by Gliknik (Baltimore, MD) (25,28).…”

“…However, several reports suggest that many of the tolerogenic properties of IVIG can be recapitulated by Fc aggregates (16)(17)(18)(19)(20)(21)(22)(23)(24). As a first step in translating the use of Fc aggregates into clinical practice, we created fully recombinant murine Fc multimers, termed stradomers, which are composed of the Fc fragment of mouse IgG2a and a human IgG2 multimerization domain, and demonstrated that these compounds can effectively treat idiopathic thrombocytopenic purpura and collagen-induced arthritis in mice (25). The anti-inflammatory properties of these or similar stradomers have been reproduced by other investigators in murine models of experimental autoimmune neuritis and myasthenia gravis (26,27).…”

Therapeutic Effect of IVIG on Inflammatory Arthritis in Mice Is Dependent on the Fc Portion and Independent of Sialylation or Basophils

“…However, the scientific basis of its effect has not been rigorously examined in animal disease models and remains controversial (34). In models of inflammatory arthritis, IVIG alleviated adjuvant-induced arthritis in rats (42) and K/BxN serum transfer arthritis in mice (43-45) but showed only a weak effect against murine collagen-induced arthritis (46). Detailed investigations into IVIG protection from inflammatory arthritis have focused on prophylactic studies in the K/BxN serum transfer model, and it is unclear how universal the proposed mechanisms of action are.…”