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Cleavage of anti-PF4/heparin IgG by a bacterial protease and potential benefit in heparin-induced thrombocytopenia
Kizlik-Masson C, Deveuve Q, Zhou Y, Vayne C, Thibault G, McKenzie SE, Pouplard C, Loyau S, Gruel Y and Rollin J
Heparin-induced thrombocytopenia (HIT) is due to immunoglobulin G (IgG) antibodies, which bind platelet factor 4 (PF4) modified by polyanions, such as heparin (H). IgG/PF4/polyanion complexes directly activate platelets via Fc gamma type 2 receptor A (FcgRIIA) receptors. A bacterial protease, IgG-degrading enzyme of Streptococcus pyogenes (IdeS), cleaves the hinge region of heavy-chain IgG, abolishing its ability to bind FcgR, including FcgRIIA. We evaluated whether cleavage of anti-PF4/H IgG by IdeS could suppress the pathogenicity of HIT antibodies. IdeS quickly cleaved purified 5B9, a monoclonal chimeric anti-PF4/H IgG1, which led to the formation of single cleaved 5B9 (sc5B9), without any reduction in binding ability to the PF4/H complex. However, as compared with uncleaved 5B9, the affinity of sc5B9 for platelet FcgRIIA was greatly reduced, and sc5B9 was also unable to induce heparin-dependent platelet activation. In addition, incubating IdeS in whole blood containing 5B9 or HIT plasma samples led to cleavage of anti-PF4/H antibodies, which fully abolished the ability to induce heparin-dependent platelet aggregation and tissue factor messenger RNA synthesis by monocytes. Also, when whole blood was perfused in von Willebrand factor–coated microfluidic channels, platelet aggregation and fibrin formation induced by 5B9 with heparin was strongly reduced after IdeS treatment. Finally, IdeS prevented thrombocytopenia and hypercoagulability induced by 5B9 with heparin in transgenic mice expressing human PF4 and FcgRIIA receptors. In conclusion, cleavage of anti-PF4/H IgG by IdeS abolishes heparin-dependent cellular activation induced by HIT antibodies. IdeS injection could be a potential treatment of patients with severe HIT.
Radiolabelled polymeric IgA: from biodistribution to a new molecular imaging tool in colorectal cancer lung metastases
Oncotarget, Advance Publications 2017
Carpenet H, Cuvillier A, Perraud A, Martin O, Champier G, Jauberteau M-O, Monteil J and Quelven I
By radiolabelling monomeric (m) and polymeric (p) IgA with technetium 99m (99mTc), this study assessed IgA biodistribution and tumour-targeting potency. IgA directed against carcinoembryonic antigen (CEA), a colorectal cancer marker, was selected to involve IgA mucosal tropism.
Ig was radiolabelled with 99mTc-tricarbonyl after derivatisation by 2-iminothiolane. 99mTc-IgA was evaluated by in vitro analysis. The biodistributions of radiolabelled anti-CEA mIgA, pIgA and IgG were compared in normal mice. Anti-CEA pIgA tumour uptake was studied in mice bearing the WiDr caecal orthotopic graft.
IgA radiolabelling was obtained with a high yield, was stable in PBS and murine plasma, and did not alter IgA binding functionality (Kd ≈ 25 nM). Biodistribution studies in normal mice confirmed that radiolabelled pIgA – and to a lesser extent, mIgA – showed strong and fast mucosal tropism and a shorter serum half-life than IgG. In caecal tumour model mice, evaluation of the anti-CEA-pIgA biodistribution showed a high uptake in lung metastases, confirmed by histological analysis. However, no radioactivity uptake increase in the tumoural caecum was discerned from normal intestinal tissue, probably due to high IgA caecal natural tropism. In microSPECT/CT imaging, 99mTc-IgA confirmed its diagnostic potency of tumour in mucosal tissue, even if detection threshold by in vivo imaging was higher than post mortem studies. Contribution of the FcαRI receptor, studied with transgenic mouse model (Tsg SCIDCD89), did not appear to be determinant in 99mTc-IgA uptake.
Pre-clinical experiments highlighted significant differences between 99mTc-IgA and 99mTc-IgG biodistributions. Furthermore, tumoural model studies suggested potential targeting potency of pIgA in mucosal tissues.
5B9, a monoclonal antiplatelet factor 4/heparin IgG with a human Fc fragment that mimics heparin-induced thrombocytopenia antibodies
KIZLIK-MASSON C, VAYNE C, MCKENZIE SE, POUPON A, ZHOU Y, CHAMPIER G, POUPLARD C, GRUEL Y and ROLLIN J
The diagnosis of heparin-induced thrombocytopenia (HIT) is based on clinical and biological criteria, but a standard is lacking for laboratory assays. Moreover, no humanized HIT antibody is available for pathophysiological studies. Objective: To characterise 5B9, a chimeric monoclonal antibody, which fully mimics the effects of human HIT antibodies. Methods/Results: 5B9, a chimeric anti-platelet factor 4/heparin complexes IgG1 antibody, was obtained after immunizing specific transgenic mice. 5B9 induced heparin FccRIIA-dependent platelet aggregation and tissue factor mRNA synthesis in monocytes. It also induced significant thrombocytopenia ,and thrombin generation in mice expressing human PF4 and FccRIIA receptors. The binding of 5B9 to PF4/H complexes was inhibited by 15 of 25 HIT plasma samples and only three of 25 samples containing non-pathogenic anti-PF4/H antibodies. KKO, a murine IgG2b HIT antibody, also inhibited the binding of 5B9 to PF4/H, suggesting that epitopes recognized by both antibodies are close. A docking analysis based on VH and VL sequences of 5B9 showed that binding of 5B9 Fab to PF4 involved 12 and 12 residues in B and D monomers, respectively, including seven previously identified as critical to the formation of a PF4/KKO complex. Two regions (Asp-7 to Thr-15 and Ala-32 to Thr-38) therefore appeared important for the binding of 5B9 and KKO on PF4 modified by heparin. Conclusions: 5B9 is the first anti-PF4/H monoclonal antibody with a human Fc fragment, which induces similar cellular activation as HIT antibodies. Moreover, 5B9 binds epitopes within PF4 that are likely to be critical for the pathogenicity of HIT antibodies.
Ternary polysaccharide complexes: Colloidal drug delivery systems stabilized in physiological media.
Wu D, Ensinas A, Verrier B, Cuvillier A, Champier G, Paul S, Delair T.
Chitosan-hyaluronan (HYA) polyelectrolyte complexes (PECs) were designed to maintain their colloidal stabilities in physiological ionic strength and pH, via a new concept of ternary complexes. This strategy relied on the formation of a binary PEC between chitosan and a strong polyacid, dextran sulphate (DS) or heparin (HEP), and further functionalization with HYA. The major parameter leading to stabilized colloids was a high ratio of the degrees of polymerization of chitosan versus the strong polyacid. The process afforded either positive or negative particles when HYA was used in default or in excess (vs. chitosan) for the functionalization of the binary complexes. The most stable formulations were loaded with an antiretroviral drug tenofovir (TF), and could be surface functionalized with targeting IgAs. In vitro, the cationic TF loaded ternary complexes exhibited an inhibition of infection of PBMCs by the HIV-1 virus, superior to the free drug.
First Membrane Proximal External Region-Specific Anti-HIV1 Broadly Neutralizing Monoclonal IgA1 Presenting Short CDRH3 and Low Somatic Mutations
Benjelloun F, Oruc Z, Thielens N, Verrier B, Champier G, Vincent N, Rochereau N, Girard A, Jospin F, Chanut B, Genin C, Cogné M, Paul S.
Mucosal HIV-1-specific IgA have been described as being able to neutralize HIV-1 and to block viral transcytosis. In serum and saliva, the anti-HIV IgA response is predominantly raised against the envelope of HIV-1. In this work, we describe the in vivo generation of gp41-specific IgA1 in humanized α1KI mice to produce chimeric IgA1. Mice were immunized with a conformational immunogenic gp41-transfected cell line. Among 2300 clones screened by immunofluorescence microscopy, six different gp41-specific IgA with strong recognition of gp41 were identified. Two of them have strong neutralizing activity against primary HIV-1 tier 1, 2, and 3 strains and present a low rate of somatic mutations and autoreactivity, unlike what was described for classical gp41-specific IgG. Epitopes were identified and located in the hepted repeat 2/membrane proximal external region. These Abs could be of interest in prophylactic treatment to block HIV-1 penetration in mucosa or in chronically infected patients in combination with antiretroviral therapy to reduce viral load and reservoir.
Zinc-Stabilized Chitosan-Chondroitin Sulfate Nanocomplexes for HIV-1 Infection Inhibition Application.
Wu D, Ensinas A, Verrier B, Primard C, Cuvillier A, Champier G, Paul S, and Delair T
Polyelectrolyte complexes (PECs) constituted of chitosan and chondroitin sulfate (ChonS) were formed by the one-shot addition of default amounts of polyanion to an excess of polycation. Key variables of the formulation process (e.g., degree of depolymerization, charge mixing ratio, the concentration, and pH of polyelectrolyte solutions) were optimized based on the PECs sizes and polydispersities. The PECs maintained their colloidal stability at physiological salt concentration and pH thanks to the complexation of polyelectrolytes with zinc(II) ion during the nanoPECs formation process. The PECs were capable of encapsulating an antiretroviral drug tenofovir (TF) with a minimal alteration on the colloidal stability of the dispersion. Moreover, the particle interfaces could efficiently be functionalized with anti-OVA or anti-α4β7 antibodies with conservation of the antibody biorecognition properties over 1 week of storage in PBS at 4 °C. In vitro cytotoxicity studies showed that zinc(II) stabilized chitosan-ChonS nanoPECs were noncytotoxic to human peripheral blood mononuclear cells (PBMCs), and in vitro antiviral activity test demonstrated that nanoparticles formulations led to a dose-dependent reduction of HIV-1 infection. Using nanoparticles as a drug carrier system decreases the IC50 (50% inhibitory concentration) from an aqueous TF of 4.35 μmol·L(-1) to 1.95 μmol·L(-1). Significantly, zinc ions in this system also exhibited a synergistic effect in the antiviral potency. These data suggest that chitosan-ChonS nanoPECs can be promising drug delivery system to improve the antiviral potency of drugs to the viral reservoirs for the treatment of HIV infection.
IgA Structure Variations Associate with Immune Stimulations and IgA Mesangial Deposition.
Oruc Z, Oblet C, Boumediene A, Druilhe A, Pascal V, Le Rumeur E, Cuvillier A, El Hamel C, Lecardeur S, Leanderson T, Morelle W, Demengeot J, Aldigier JC, Cogné M.
IgA1 mesangial deposition is the hallmark of IgA nephropathy and Henoch-Schönlein purpura, the onset of which often follows infections. Deposited IgA has been reported as polymeric, J chain associated, and often, hypogalactosylated but with no information concerning the influence of the IgA repertoire or the link between immune stimuli and IgA structure. We explored these issues in the α1KI mouse model, which produces polyclonal human IgA1 prone to mesangial deposition. Compared with mice challenged by a conventional environment, mice in a specific pathogen-free environment had less IgA deposition. However, serum IgA of specific pathogen-free mice showed more galactosylation and much lower polymerization. Notably, wild-type, α1KI, and even J chain-deficient mice showed increased polymeric serum IgA on exposure to pathogens. Strict germfree conditions delayed but did not completely prevent deposition; mice housed in these conditions had very low serum IgA levels and produced essentially monomeric IgA. Finally, comparing monoclonal IgA1 that had different variable regions and mesangial deposition patterns indicated that, independently of glycosylation and polymerization, deposition might also depend on IgA carrying specific variable domains. Together with IgA quantities and constant region post-translational modifications, repertoire changes during immune responses might, thus, modulate IgA propensity to deposition. These IgA features are not associated with circulating immune complexes and C3 deposition and are more pertinent to an initial IgA deposition step preceding overt clinical symptoms in patients.
Anti-CD20 Immunoglobulin G Radiolabeling with a 99mTc-Tricarbonyl Core: In Vitro and In Vivo Evaluations.
In recent years, the diagnostic and therapeutic uses of radioisotopes have shown significant progress. Immunoglobulin (Ig) appears to be a promising tracer, particularly due to its ability to target selected antigens. The main objective of this study is to optimize and assess an Ig radiolabeling method with Technetium 99m (99mTc), an attractive radioelement used widely for diagnostic imaging. Monoclonal anti-CD20 IgG was retained to study in vitro and in vivo radiolabeling impact. After IgG derivatization with 2-iminothiolane, IgG-SH was radiolabeled by an indirect method, using a 99mTc-tricarbonyl core. Radiolabeling stability was evaluated over 24h by thin-layer chromatography. IgGintegrity was checked by sodium dodecyl sulfate-polyacrylamide gel electrophoresis coupled with Western blot and autoradiography. The radiolabeled Ig's immunoaffinity was assessed in vitro by a radioimmunoassay method and binding experiments with cells (EL4-hCD20 and EL4-WT). Biodistribution studies were performed in normal BALB/c mice. Tumor uptake was assessed in mice bearing EL4-hCD20 and EL4-WT subcutaneous xenografts. With optimized method, high radiolabeling yields were obtained (95.9 ± 3.5%). 99mTc-IgG-SH was stable in phosphate-buffered saline (4°C and 25°C) and in serum (37°C), even if important sensitivity to transchelation was observed. IgG was not degraded by derivatization and radiolabeling, as shown by Western blot and autoradiography results. 99mTc-anti-CD20 IgG-SH immunoaffinity was estimated with Kd = 35 nM by both methods. In vivo biodistribution studies for 48h showed significant accumulation of radioactivity in plasma, liver, spleen, lungs and kidneys. Planar scintigraphy of mice bearing tumors showed a significant uptake of 99mTc-anti-CD20 IgG-SH in CD20+ tumor versus CD20- tumor. Radiolabeling of derivatized IgG with 99mTc-tricarbonyl was effective, stable and required few antibody amounts. This attractive radiolabeling method is "antibody safe" and preserves Ig affinity for antigen, as shown by both in vitro and in vivo experiments. This method could easily be used with noncommercial IgG or other antibody isotypes.
Increased risk of thrombosis in FcγRIIA 131RR patients with HIT due to defective control of platelet activation by plasma IgG2.
Rollin J, Pouplard C, Sung HC, Leroux D, Saada A, Gouilleux-Gruart V, Thibault G, Gruel Y.
Thrombosis results in heparin-induced thrombocytopenia (HIT) from cellular activation involving Fc receptors. In this study, the FcγRIIA 131RR genotype was found to increase the risk of thrombosis in HIT patients (odds ratio: 5.9; 95% confidence interval: 1.7-20). When platelet aggregation tests (PATs) were performed with platelet-rich plasma (PRP), a shorter lag time was measured in 131RR donors compared to individuals with the HR and HH genotypes in response to HIT plasma or 5B9, a recently developed humanized monoclonal antibody to PF4/heparin. Importantly, this difference was no longer detectable when PATs were performed with washed platelets or immunoglobulin (Ig)G-depleted PRP. Moreover, polyclonal IgG or monoclonal IgG1 added to IgG-depleted PRP increased the lag time in response to 5B9. HH platelets were also sensitive to IgG2, which in contrast, failed to inhibit the response of 131RR platelets to 5B9. Finally, higher tissue factor messenger RNA levels were measured in the whole blood of 131RR donors after activation by HIT antibodies, with increased phospholipid procoagulant activity. These results demonstrate that HIT patients homozygous for the FcγRIIA 131R allele have a higher risk of thrombosis, probably due to increased cell activation by antibodies to PF4/heparin, with a lower inhibitory effect of endogenous IgG, especially from the IgG2 subclass.
Abnormal apical-to-basal transport of dietary ovalbumin by secretory IgA stimulates a mucosal Th1 response.
In celiac disease, enhanced permeability to gliadin peptides can result from their apico-basal transport by secretory immunoglobulin A1 (SIgA1) binding to the CD71 receptor ectopically expressed at the gut epithelial surface. Herein, we have established a mouse model in which there is apico-basal transport of the model antigen ovalbumin (OVA) by specific SIgA1 and have analyzed local T-cell activation. Transgenic DO11.10 mice were grafted with a hybridoma-secreting OVA-specific humanized IgA1, which could bind mouse CD71 and which were released in the intestinal lumen as SIgA. CD71 expression was induced at the gut apical surface by treating the mice with tyrphostin A8. Following gavage of the mice with OVA, OVA-specific CD4⁺ T cells isolated from the mesenteric lymph nodes displayed higher expression of the activation marker CD69 and produced more interferon gamma in mice bearing the hybridoma-secreting OVA-specific IgA1, than in ungrafted mice or in mice grafted with an irrelevant hybridoma. These results indicate that the protective role of SIgA1 might be jeopardized in human pathological conditions associated with ectopic expression of CD71 at the gut surface.
Anti-CD20 IgA can protect mice against lymphoma development: evaluation of the direct impact of IgA and cytotoxic effector recruitment on CD20 target cells.
Pascal V, Laffleur B, Debin A, Cuvillier A, van Egmond M, Drocourt D, Imbertie L, Pangault C, Tarte K, Tiraby G and Cogné M
Background: While most antibody-based therapies use IgG because of their well-known biological properties, some functional limitations of these antibodies call for the development of derivatives with other therapeutic functions. Although less abundant than IgG in serum, IgA is the most abundantly produced Ig class in humans. Besides the specific targeting of its dimeric form to mucosal areas, IgA was shown to recruit polymorphonuclear neutrophils against certain targets more efficiently than does IgG1.
Design and methods: In this study, we investigated the various pathways by which anti-tumor effects can be mediated by anti-CD20 IgAagainst lymphoma cells.
Results: We found that polymeric human IgA was significantly more effective than human IgG1 in mediating direct killing or growth inhibition of target cells in the absence of complement. We also demonstrated that this direct killing was able to indirectly induce the classical pathway of the complement cascade although to a lesser extent than direct recruitment of complement by IgG. Recruitment of the alternative complement pathway by specific IgA was also observed. In addition to activating complement for lysis of lymphoma cell lines or primary cellsfrom patients with lymphoma, we showed that monomeric anti-CD20 IgA can effectively protect mice against tumor development in a passive immunization strategy and we demonstrated that this protective effect may be enhanced in mice expressing the human FcαRI receptor on their neutrophils.
Conclusions: We show that anti-CD20 IgA antibodies have original therapeutic properties against lymphoma cells, with strong direct effects, ability to recruit neutrophils for cell cytotoxicity and even recruitment of complement, although largely through an indirect way.
Similarity of Fine Specificity of IgA Anti-gliadin Antibodies between Patients with Celiac Disease and Humanized α1KI Mice
Gliadins, and primarily α-gliadins containing several sequences such as aa 31−49, aa 56−88 (33-mer), aa 57−68, and aa 69−82, are critical in the induction of immune response or toxic reaction leading to the development of celiac disease (CLD). The role of IgA anti-gliadin antibodies (IgA AGA) is unknown. To this end, we prepared several humanized monoclonal IgA AGA using transgenic α1KI mice. Employing Pepscan with overlapping decapeptides of α-gliadin we observed a robust similarity between the specificity of humanized mouse monoclonal IgA AGA and IgA AGA from patients with florid CLD. The common immunodominant region included several sequential epitopes localized in the N-terminal part of α-gliadin (QFQGQQQPFPPQQPYPQPQPFP, aa 29−50, and QPFPSQQPYLQL, aa 47−58). Notably, IgA AGA produced by clones 8D12, 15B9, 9D12, and 18E2 had significant reactivity against sequences localized in the 33-mer, LQLQPFPQPQ (aa 56−65) and PQLPYPQPQPFL (aa 69−80). Humanized mouse monoclonal IgA AGA that have a known specificity are suitable as standard in ELISAs to detect serum IgA AGA of CLD patients and for studying the AGA pathogenic role in CLD, especially for analyzing the translocation of complex of specific IgA antibodies and individual gliadin peptides through enterocyte barrier.