ß2 glycoprotein I participates in phagocytosis of apoptotic neurons and in vascular injury in experimental brain stroke.

Beta-2 Glycoprotein I (ß2-GPI) is the main target of anti-phospholipid antibodies (aPL) in the autoimmune anti-phospholipid syndrome, characterized by increased risk of stroke. We here investigated the antibody independent role of ß2-GPI after ischemia/reperfusion, modeled in vivo by transient middle cerebral artery occlusion (tMCAo) in male C57Bl/6J mice; in vitro by subjecting immortalized human brain microvascular endothelial cells (ihBMEC) to 16 h hypoxia and 4 h re-oxygenation. ApoH (coding for ß2-GPI) was upregulated selectively in the liver at 48 h after tMCAo. At the same time ß2-GPI circulating levels increased. ß2-GPI was detectable in brain parenchyma and endothelium at all time points after tMCAo. Parenchymal ß2-GPI recognized apoptotic neurons (positive for annexin V, C3 and TUNEL) cleared by CD68+ brain macrophages. Hypoxic ihBMEC showed increased release of IL-6, over-expression of thrombomodulin and IL-1α after re-oxygenation with ß2-GPI alone. ß2-GPI interacted with mannose-binding lectin in mouse plasma and ihBMEC medium, potentially involved in formation of thrombi. We show for the first time that brain ischemia triggers the hepatic production of ß2-GPI. ß2-GPI is present in the ischemic endothelium, enhancing vascular inflammation, and extravasates binding stressed neurons before their clearance by phagocytosis. Thus ß2-GPI may be a new mediator of brain injury following ischemic stroke.

Complement Activation and Thrombin Generation by MBL Bound to ß2-Glycoprotein I.

ß2-Glycoprotein I (ß2-GPI) is an abundant plasma glycoprotein with unknown physiological function and is currently recognized as the main target of antiphospholipid Abs responsible for complement activation and vascular thrombosis in patients with antiphospholipid syndrome (APS). In this study, we provide evidence that mannose-binding lectin (MBL) binds to ß2-GPI in Ca++ and a dose-dependent manner and that this interaction activates complement and promotes complement-dependent thrombin generation. Surprisingly, a significant binding was observed between MBL and isolated domains II and IV of ß2-GPI, whereas the carbohydrate chains, domain I and domain V, were not involved in the interaction, documenting a noncanonical binding mode between MBL and ß2-GPI. Importantly, this interaction may occur on endothelial cells because binding of MBL to ß2-GPI was detected on the surface of HUVECs, and colocalization of MBL with ß2-GPI was observed on the endothelium of a biopsy specimen of a femoral artery from an APS patient. Because ß2-GPI-mediated MBL-dependent thrombin generation was increased after priming the endothelium with TNF-α, our data suggests that this mechanism could play an important yet unrecognized role under physiological conditions and may be upregulated in pathological situations. Moreover, the complement activation and the procoagulant effects of the ß2-GPI/MBL complex may contribute to amplify similar activities of anti-ß2-GPI Abs in APS and possibly act independently of Abs, raising the issue of developing appropriate therapies to avoid recurrences and disability in patients at risk for these clinical conditions.

Personalized medicine in rheumatoid arthritis: How immunogenicity impacts use of TNF inhibitors.

Up to 40% of patients treated with tumor necrosis factor alpha inhibitors (TNFi) do not respond to therapy. Testing drug bioavailability and/or anti-drug antibody (ADAb) levels may justify dosage adjustment or switch to different drugs, enabling a personalized medicine approach. We report a multicenter cross-sectional study on different methods [ELISA and a cell based functional assay (reporter gene assay - RGA)] for drug/ADAb detection, and on the relationship between drug bioavailability and ADAb. 163 patients with rheumatoid arthritis (RA) treated with infliximab (IFX; n = 67), adalimumab (ADL; n = 49) or etanercept (ETA; n = 47) were tested for drug and ADAb levels. Furthermore, we report prospective data from additional 70 patients (59 RA and 11 juvenile idiopathic arthritis - JIA) tested for drug and ADAb levels at baseline (T0) and after 3 (T3) and 6 months (T6) of treatment with ADL or ETA only. IFX-treated patients were not included because of the increasing use of IFX biosimilars. Stringent inclusion criteria were used in order to avoid unwanted variables in both studies; none of the patients used TNFi before the study, and TNFi was used only in combination with methotrexate. Clinical response was defined according to EULAR response criteria. The two assays performed comparably in the comparison study. Accordingly, ELISA was selected for the prospective study because of its feasibility in the clinical setting. The cross-sectional study found ADAb in IFX and ADL treated groups only, that were associated with a decrease in pharmacological drug availability in the blood. Comparable results were found for the ADL-treated group in the prospective study which also showed a relationship between drug/ADAb levels and the loss of clinical response. Altogether our findings support drug and anti-drug Ab monitoring in the real-world clinical setting thus enabling individualized treatment and reducing disability in chronic inflammatory arthritis.

Antiphospholipid Antibodies and Infertility: A Gene Expression Study in Decidual Stromal Cells.

BACKGROUND: Antiphospholipid antibodies (aPL) have been advocated as potential mediators of unexplained female infertility, but no evidence has yet been raised to support such an association. OBJECTIVES: To test the hypothesis that aPL might interfere with uterine decidualization, a gene expression study was performed on decidual stromal cells treated with different aPL preparations. METHODS: Decidual stromal cells were isolated from first-trimester deciduas obtained from two women undergoing elective abortion, and treated with: (i) a ß2GPI-dependent aPL monoclonal antibody (IS3); (ii) IS3 plus TIFI, a synthetic peptide mimicking PL-binding region of ß2GPI; and (iii) IgG from healthy subjects (NHS). Gene expression data were acquired using human HT-12 v3 beadchip arrays (Illumina). Differential expression analysis was performed by fitting a gene-wise linear model using the treatment group and decidual source as covariates. RESULTS: In the comparison of IS3 versus IgG NHS-treated decidual cells, gene ontology (GO) enrichment was expressed in terms relating to well-characterized aPL-mediated cellular effects: "inflammatory response," "immune response," "response to stress," "oxydoreductase activity," "metalloendopeptidase activity," and "cytokine/chemokine activity." As expected, almost all genes were up-regulated by IS3 treatment. The same GO categories appeared to be differentially expressed when IS3 treatment was compared to IS3 + TIFI, but with most genes being down-regulated. CONCLUSIONS: Given the inflammatory response evinced on gene expression analysis of decidual stromal cells treated with a ß2GPI -dependent aPL monoclonal antibody, it is feasible that aPL might interfere with uterine decidualization, affecting the early stages of implantation and ultimately resulting in female infertility.

Anti-phospholipid induced murine fetal loss: novel protective effect of a peptide targeting the ß2 glycoprotein I phospholipid-binding site. Implications for human fetal loss.

ß2 glycoprotein I (ß2GPI)-dependent anti-phospholipid antibodies (aPL) induce thrombosis and affect pregnancy. The CMV-derived synthetic peptide TIFI mimics the PL-binding site of ß2GPI and inhibits ß2GPI cell-binding in vitro and aPL-mediated thrombosis in vivo. Here we investigated the effect of TIFI on aPL-induced fetal loss in mice. TIFI inhibitory effect on in vitro aPL binding to human trophoblasts was evaluated by indirect immunofluorescence and ELISA. TIFI effect on aPL-induced fetal loss was investigated in pregnant C57BL/6 mice treated with aPL or normal IgG (NHS). Placenta/fetus weight and histology and RNA expression were analyzed. TIFI, but not the control peptide VITT, displayed a dose-dependent inhibition of aPL binding to trophoblasts in vitro. Injection of low doses of aPL at day 0 of pregnancy caused growth retardation and increased fetal loss rate, both significantly reduced by TIFI but not VITT. Consistent with observations in humans, histological analysis showed no evidence of inflammation in this model, as confirmed by the absence of an inflammatory signature in gene expression analysis, which in turn revealed a TIFI-dependent modulation of molecules involved in differentiation and development processes. These findings support the non-inflammatory pathogenic role of aPL and suggest innovative therapeutic approaches to aPL-dependent fetal loss.