Fabio Fischetti

Risk factors for a first thrombotic event in antiphospholipid antibody carriers: a prospective multicentre follow-up study

Objectives To assess risk factors for a first thrombotic event in confirmed antiphospholipid (aPL) antibody carriers and to evaluate the efficacy of prophylactic treatments. Methods Inclusion criteria were age 18–65 years, no history of thrombosis and two consecutive positive aPL results. Demographic, laboratory and clinical parameters were collected at enrolment, once a year during the follow-up and at the time of the thrombotic event, whenever that occurred. Results 258 subjects were prospectively observed between October 2004 and October 2008. The mean±SD follow-up was 35.0±11.9 months (range 1–48). A first thrombotic event (9 venous, 4 arterial and 1 transient ischaemic attack) occurred in 14 subjects (5.4%, annual incidence rate 1.86%). Hypertension and lupus anticoagulant (LA) were significantly predictive of thrombosis (both at p<0.05) and thromboprophylaxis was significantly protective during high-risk periods (p<0.05) according to univariate analysis. Hypertension and LA were identified by multivariate logistic regression analysis as independent risk factors for thrombosis (HR 3.8, 95% CI 1.3 to 11.1, p<0.05, and HR 3.9, 95% CI 1.1 to 14, p<0.05, respectively). Conclusions Hypertension and LA are independent risk factors for thrombosis in aPL carriers. Thromboprophylaxis in these subjects should probably be limited to high-risk situations.

Complement-endothelial cell interactions: pathophysiological implications.

The function of the endothelial cells can be modulated by humoral factors present in the circulation and in the extravascular fluid, including proteins of the complement system. This review examines the multiple interactions between the complement system and the endothelial cells and their functional consequences on inflammation, coagulation and regulation of vascular tone. The implications of these interactions in the induction and progression of the vascular lesions occurring in atherosclerosis, ischemia/reperfusion and xenotransplantation and the possible therapeutic approaches in terms of complement regulation are also discussed.

Platelet-Activating Factor and Kinin-Dependent Vascular Leakage as a Novel Functional Activity of the Soluble Terminal Complement Complex

The infrequent occurrence of septic shock in patients with inherited deficiencies of the terminal complement components experiencing meningococcal disease led us to suspect that the terminal complement complex is involved in vascular leakage. To this end, the permeabilizing effect of the cytolytically inactive soluble terminal complement complex (SC5b-9) was tested in a Transwell system measuring the amount of fluorescein-labeled BSA (FITC-BSA) leaked through a monolayer of endothelial cells. The complex caused increased permeability to FITC-BSA after 15 min as opposed to the prompt response to bradykinin (BK). The effect of SC5b-9 was partially reduced by HOE-140 or CV-3988, two selective antagonists of BK B2 and platelet-activating factor receptors, respectively, and was completely neutralized by the mixture of the two antagonists. Also, DX-88, a specific inhibitor of kallikrein, partially inhibited the activity of SC5b-9. The permeabilizing factor(s) released after 30 min of incubation of endothelial cells with SC5b-9 caused a prompt leakage of albumin like BK. Intravital microscopy confirmed both the extravasation of circulating FITC-BSA across mesenteric microvessels 15 min after topical application of SC5b-9 and the complete neutralization by the mixture of HOE-140 and CV-3988. SC5b-9 induced opening of interendothelial junctions in mesenteric endothelium documented by transmission electron microscopy.

The Neutrophil-Activating Protein of Helicobacter pylori Crosses Endothelia to Promote Neutrophil Adhesion In Vivo

Helicobacter pylori induces an acute inflammatory response followed by a chronic infection of the human gastric mucosa characterized by infiltration of neutrophils/polymorphonuclear cells (PMNs) and mononuclear cells. The H. pylori neutrophil-activating protein (HP-NAP) activates PMNs, monocytes, and mast cells, and promotes PMN adherence to the endothelium in vitro. By using intravital microscopy analysis of rat mesenteric venules exposed to HP-NAP, we demonstrated, for the first time in vivo, that HP-NAP efficiently crosses the endothelium and promotes a rapid PMN adhesion. This HP-NAP-induced adhesion depends on the acquisition of a high affinity state of β2 integrin on the plasma membrane of PMNs, and this conformational change requires a functional p38 MAPK. We also show that HP-NAP stimulates human PMNs to synthesize and release a number of chemokines, including CXCL8, CCL3, and CCL4. Collectively, these data strongly support a central role for HP-NAP in the inflammation process in vivo: indeed, HP-NAP not only recruits leukocytes from the vascular lumen, but also stimulates them to produce messengers that may contribute to the maintenance of the flogosis associated with the H. pylori infection.

Novel pathogenic mechanism and therapeutic approaches to angioedema associated with C1 inhibitor deficiency.

BACKGROUND Activation of bradykinin-mediated B2 receptor has been shown to play an important role in the onset of angioedema associated with C1 inhibitor deficiency. This finding has led to the development of novel therapeutic drugs such as the B2 receptor antagonist icatibant. However, it is unclear whether other receptors expressed on endothelial cells contribute to the release of kinins and vascular leakage in these patients. The recognition of their role may have obvious therapeutic implications. OBJECTIVE Our aim was to investigate the involvement of B1 and gC1q receptors in in vitro and in vivo models of vascular leakage induced by plasma samples obtained from patients with C1 inhibitor deficiency. METHODS The vascular leakage was evaluated in vitro on endothelial cells by a transwell model system and in vivo on rat mesentery microvessels by intravital microscopy. RESULTS We observed that the attack phase plasma from C1 inhibitor-deficient patients caused a delayed fluorescein-labeled albumin leakage as opposed to the rapid effect of bradykinin, whereas remission plasma elicited a modest effect compared with control plasma. The plasma permeabilizing effect was prevented by blocking the gC1q receptor-high-molecular-weight kininogen interaction, was partially inhibited by B2 receptor or B1 receptor antagonists, and was totally prevented by the mixture of the 2 antagonists. Involvement of B1 receptor was supported by the finding that albumin leakage caused by attack phase plasma was enhanced by IL-1beta and was markedly reduced by brefeldin A. CONCLUSION Our data suggest that both B1 receptor and gC1q receptor are involved in the vascular leakage induced by hereditary and acquired angioedema plasma.

Cross-talk between the complement system and endothelial cells in physiologic conditions and in vascular diseases

The endothelial layer represents a continuous physical barrier that controls coagulation and allows selective passage of soluble molecules and circulating cells across the vessel wall into the tissue. The functional activity of the endothelial cells may be influenced by their interaction with components of the complement system. In this review we shall discuss the complex interplay that can be established between the endothelium and complement proteins or activation products. Endothelial cells may also secrete several complement components which contribute to the circulating pool. This process can be regulated by cytokines and other pro-inflammatory stimuli. In addition, complement activation products stimulate endothelial cells to acquire a pro-inflammatory and pro-coagulant status. Expression of regulatory molecules on the cell surface provides protection against an undesired attack by complement activation products. Unrestricted complement activation under pathological conditions may lead to structural and functional changes of the endothelium resulting in vascular disease.

The cleavage site of C5 from man and animals as a common target for neutralizing human monoclonal antibodies: in vitro and in vivo studies

The isolation of an anti‐C5 single‐chain fragment variable (scFv) antibody, TS‐A12/22, from a human phage display library, is described. This antibody inhibits the activation of C5 and the assembly of the terminal complement complex implicated in cell and tissue damage. Using antibody‐sensitized sheep erythrocytes and rabbit red cells as target cells in hemolytic assays, we found that TS‐A12/22 inhibited the activation of C5 by the convertases of both classical and alternative pathways. Western blot analysis and competition experiments with synthetic peptides showed that TS‐A12/22 reacted with the α chain of C5 and recognized the cleavage site of this complement component by the C5 convertase. As a result, the antibody prevented splitting of C5 and inhibited the generation of C5a and of the terminal complement complex. The identification of the TS‐A12/22 recognition site as a conserved sequence in man, mouse, rat and rabbit enabled the demonstration of in vitro inhibition of complement activity in these species. The scFv TS‐A12/22 was tested in a rat model of antigen‐induced arthritis and proved to be effective in preventing influx of polymorphonuclear cells into the knee joint and C9 deposition on synovial tissue.

The CC homozygosis of the -174G>C IL-6 polymorphism predicts a lower efficacy of rituximab therapy in rheumatoid arthritis

Identification of genetic biomarkers of response to biologics in rheumatoid arthritis (RA) is a relevant issue. Being IL-6 a key cytokine for B cell survival, the interleukin-6 (IL-6) -174G>C and the IL-6 receptor (IL-6R) D358A gene polymorphisms were investigated in 158 RA patients treated with rituximab (RTX). One hundred and twenty-eight (81.0%) were RF positive and 126 (79.7%) were anti-CCP positive. Response to therapy was evaluated at the end of the sixth month after the first RTX infusion, by using both the EULAR and the ACR criteria. The possible relationship with IL-6 serum levels was also studied. By univariate analysis, lack of response by the EULAR criteria was more prevalent in RA patients with the IL-6 -174 CC genotypes (39.1%), than in the GC/GG patients (18.5%) (OR 2.83; 95%CI=1.10-7.27; p=0.031). A good response was noticed in only one patient (4.3%) with the IL-6 -174 CC genotype, while it was present in 24.4% of GG/GC cases (p=0.06). By stepwise multivariate analysis (including RA duration, baseline DAS28, baseline HAQ, RF status, anti-CCP status and IL-6 genotype as covariates), the IL-6 -174CC genotype was selected as an independent predictor of no response to RTX by both EULAR and ACR≥50 criteria, while the IL-6R polymorphism resulted as not associated. No definite association between gene polymorphisms and IL-6 serum levels was noticed. Present results suggest a possible role for IL-6 genotyping to better plan treatment with RTX in RA, and larger studies are worthwhile.

The 158VV Fcgamma receptor 3A genotype is associated with response to rituximab in rheumatoid arthritis: results of an Italian multicentre study

Objective The polymorphism 158V/F of Fc fragment of IgG (FCGR) type 3A may influence the response to rituximab (RTX) in rheumatoid arthritis (RA). We investigated the FCG3A polymorphism in a large cohort of RA patients treated with RTX, also by considering the possible loss of response from month +4 to +6 after RTX and the presence of established predictors of response. Methods The study analysed 212 RA patients. European League Against Rheumatism (EULAR) response was evaluated at months +4 and +6 after the first RTX infusion. The FCGR3A polymorphism was analysed by PCR followed by Sanger sequencing. Results The FCGR3A genotypes were associated with EULAR response (good or moderate) at month +6 (response in 34/38 (89.5%) VV vs 70/106 (66%) VF and in 51/77 (66.2%) FF patients; p=0.01), but not at month +4 (response in 32/37 (86.5%) VV vs 69/102 (67.6%) VF and 53/73 (72.6%) FF patients; p=0.09). Loss of response was observed only in VF and FF carriers ((VV vs VF vs FF: 0/37 (0%) vs 11/102 (10.8%) vs 12/73 (16.4%); p=0.02)). Probability of response at month +6 was very high when at least two of the three following items selected by multivariate analysis were present: positive rheumatoid factor and/or anticyclic citrullinated peptide antibodies, previous treatment with ≤1 anti-tumor necrosis factor (TNF) agent, and 158VV FCGR3A genotype (p<0.0001; OR 7.9, 95% CI 4.1 to 15.1). Conclusions The 158VV FCGR3A genotype was associated with response to RTX in a large cohort of RA patients. Patient genotyping may be helpful to plan RTX treatment, and may be integrated with clinical predictors.

Treatment of experimental arthritis by targeting synovial endothelium with a neutralizing recombinant antibody to C5

OBJECTIVE To show that a new recombinant protein (MT07) obtained by fusing a synovial-homing peptide to a neutralizing antibody to C5 can be selectively delivered to inflamed synovium and can effectively control joint inflammation in experimental models of arthritis. METHODS Binding of MT07 to human, rat, and mouse synovial tissue was evaluated in vitro by immunofluorescence, and selective localization in the inflamed joints of rats was documented in vivo using time-domain optical imaging. The antiinflammatory effect of MT07 was tested in a rat model of antigen-induced arthritis (AIA) and in a mouse model of collagen antibody-induced arthritis (CAIA). RESULTS MT07 was able to bind to samples of inflamed synovium from humans, mice, and rats while failing to recognize uninflamed synovium as well as inflamed mouse lung or rat kidney. In vivo analysis of the biodistribution of MT07 confirmed its preferential homing to inflamed joints, with negligible inhibition of circulating C5 levels. MT07 prevented and resolved established inflammation in a rat model of AIA, as demonstrated by changes in joint swelling, polymorphonuclear cell counts in synovial washes, release of interleukin-6 and tumor necrosis factor α, and tissue damage. A similar therapeutic effect was obtained testing MT07 in a CAIA model. CONCLUSION Our findings show that the novel recombinant molecule MT07 has the unique ability to selectively target inflamed joints and to exert local control of the inflammatory process by neutralizing the complement system without interfering with circulating C5 levels. We believe that this approach can be extended to other antiinflammatory drugs currently used to treat patients with rheumatoid arthritis.