Selective blockade of the inhibitory Fcγ receptor (FcγRIIB) in human dendritic cells and monocytes induces a type I interferon response program

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the presence of pathogenic autoantibodies, many of which are directed against nuclear antigens, in particular double-stranded (ds) DNA. Both clinical studies and animal models have shown that anti-dsDNA antibodies contribute to kidney disease, which is present in 50% of lupus patients and is a major cause of mortality. We previously demonstrated that a subset of nephrotoxic anti-dsDNA antibodies also recognizes the pentapeptide consensus sequence D/E W D/E Y S/G (DWEYS) present in the NR2A and NR2B subunits of the N -methyl- d -aspartate receptor (NMDAR). Autoantibodies with this specificity are present in ≈40% of lupus patient sera and are both nephrotoxic and neurotoxic. Elevated titers are present in cerebrospinal fluid of patients with central nervous system manifestations of SLE. Administration of the nonnaturally occurring D form of the DWEYS pentapeptide prevents these antibodies from depositing in glomeruli and from mediating neuronal excitotoxicity. To craft a more useful therapeutic, we used the structural features of the DWEYS peptide to design a unique, selective, and potent small molecule peptidomimetic, FISLE-412, which neutralizes anti-dsDNA/NMDAR lupus autoantibodies and prevents their pathogenic interaction with tissue antigens. This compound, or others derived from it, may provide a unique strategy for the development of lupus therapeutics.

Section: Discussionmentioning

confidence: 99%

Generation of a unique small molecule peptidomimetic that neutralizes lupus autoantibody activity

Bloom

Cheng

et al. 2011

“…However, entry through the activating FcγR pathway would pose no replicative benefit to DENV unless it is able to overcome the ITAM-Syk-STAT-1 signaling axis that leads to ISG induction (7,13). The findings here thus indicate that coligation of LILRB1 is a critical first step for successful antibody-dependent DENV infection (SI Appendix, Fig.…”

Section: Discussionmentioning

confidence: 62%

Leukocyte immunoglobulin-like receptor B1 is critical for antibody-dependent dengue

Chan

Ong

Tan

et al. 2014

103

104

Viruses must evade the host innate defenses for replication and dengue is no exception. During secondary infection with a heterologous dengue virus (DENV) serotype, DENV is opsonized with sub-or nonneutralizing antibodies that enhance infection of monocytes, macrophages, and dendritic cells via the Fc-gamma receptor (FcγR), a process termed antibody-dependent enhancement of DENV infection. However, this enhancement of DENV infection is curious as cross-linking of activating FcγRs signals an early antiviral response by inducing the type-I IFN-stimulated genes (ISGs). Entry through activating FcγR would thus place DENV in an intracellular environment unfavorable for enhanced replication. Here we demonstrate that, to escape this antiviral response, antibody-opsonized DENV coligates leukocyte Ig-like receptor-B1 (LILRB1) to inhibit FcγR signaling for ISG expression. This immunoreceptor tyrosine-based inhibition motif-bearing receptor recruits Src homology phosphatase-1 to dephosphorylate spleen tyrosine kinase (Syk). As Syk is a key intermediate of FcγR signaling, LILRB1 coligation resulted in reduced ISG expression for enhanced DENV replication. Our findings suggest a unique mechanism for DENV to evade an early antiviral response for enhanced infection.early innate immune response | innate immune signaling | immune evasion D espite long-lived serotype-specific immunity upon initial infection, predicted global prevalence of dengue now surpasses World Health Organization estimates by more than threefold with 390 million cases annually (1). Furthermore, the risk of severe disease is augmented by cross-reactive or subneutralizing levels of antibody (2, 3), which opsonize dengue virus (DENV) to ligate Fc-gamma receptor (FcγR) for entry into monocytes, macrophages, and dendritic cells, a phenomenon known as antibody-dependent enhancement (ADE) of DENV infection (4, 5). The resultant greater viral burden leads to increased systemic inflammation that precipitates plasma leakage, a hallmark of dengue hemorrhagic fever (6). However, ligation of the activating FcγRs by immune complexes has been shown to induce type-I IFN stimulated genes (ISGs), independent of autocrine or paracrine IFN activity, unless the inhibitory FcγRIIB is coligated (7). We and others reported recently that coligation of FcγRIIB by DENV immune complexes requires high antibody concentration, and such coligation inhibited the entry of DENV immune complexes into monocytes (8, 9). At low antibody concentrations where ADE occurs, the inhibitory FcγRIIB is not coligated (9). Ligation of the activating FcγRs by DENV opsonized with subneutralizing levels of antibody would thus induce the expression of ISGs and hinder DENV replication (10). Here, we demonstrate that DENV employs a unique evasive mechanism by coligating LILRB1 to down-regulate the early antiviral responses triggered by activating FcγRs for ADE.Results ADE Differs in THP-1 Subclones. Our work was enabled by the isolation of subclones of THP-1 cells with different phenotypes to ADE. The low rate of...

“…Cross-linking of activating FcγRs by immune complexes results in ITAM phosphorylation, subsequent activation of phosphoinositide 3-kinase and generation of phosphatidylinositol-3,4,5-trisphosphate (PIP 3 ), calcium mobilization, and further downstream signaling events that lead to cell activation. In contrast, FcγRIIB contains an immunoreceptor tyrosine-based inhibitory motif (ITIM), and its phosphorylation leads to the recruitment of SH2 domain-containing inositol 5-phosphatase (SHIP), which interferes with activating signaling pathways by hydrolyzing PIP 3 .…”

mentioning

confidence: 99%

Antitumor activities of agonistic anti-TNFR antibodies require differential FcγRIIB coengagement in vivo

Ravetch

2013

Self Cite

Significance Agonistic antibodies targeting key TNF receptor (TNFR) molecules involved in antitumor responses have been demonstrated as potent antitumor therapies in preclinical studies. However, no effective agonistic anti-TNFR therapies have been successfully developed to date. In contrast, cytotoxic antitumor antibodies targeting tumor antigens or antagonistic antibodies blocking key inhibitory checkpoints are widely used in clinical settings. One explanation for this discrepancy has been recently provided by the finding that agonistic anti-TNFR antibodies have a previously unappreciated requirement for inhibitory Fcγ receptor FcγRIIB coengagement. Understanding the differential FcγRIIB coengagement requirement by different antibodies and the in vivo cross-linking function of FcγRIIB, as defined by this study, not only has implications for the development of potent agonistic anti-TNFR therapies but also for the understanding of TNFR activation mechanisms.