Differential signaling patterns of stimulated bone marrow-derived dendritic cells under α1-antitrypsin-enriched conditions.

Dendritic cells (DCs) mature upon an inflammatory trigger. However, an inflammatory trigger can lead to a semi-mature phenotype, allowing DCs to evoke tolerance and expedite the resolution of inflammation. This duality likely involves context-dependent modulation of inflammatory signaling. Human α1-antitrypsin (hAAT) promotes semimature DCs. We examined changes in a wide spectrum of signaling cascades in stimulated murine bone marrow-derived cells with hAAT. Upon stimulation by IL-1ß+IFNγ, hAAT-treated cells depicted an attenuated calcium flux. Disrupting PKA or NF-κB pathways revoked only some hAAT-mediated outcomes. hAAT-treated cells exhibited a distict pattern of kinase phosphorylation. hAAT-mediated increase in Treg cells in-vitro required intact inflammatory signaling pathways. Taken together, hAAT appears to require a stimulated microenvironment to promote inflammatory resolution, setting it aside from classical anti-inflammatory agents. Further studies are required to identify the specific molecules targeted by hAAT that mediate these and other outcomes.

Role of Homologous Fc Fragment in the Potency and Efficacy of Anti-Botulinum Antibody Preparations.

The only approved treatment for botulism relies on passive immunity which is mostly based on antibody preparations collected from hyper-immune horses. The IgG Fc fragment is commonly removed from these heterologous preparations to reduce the incidence of hyper-sensitivity reactions. New-generation therapies entering the pipeline are based on a combination of humanized monoclonal antibodies (MAbs), which exhibit improved safety and pharmacokinetics. In the current study, a systematic and quantitative approach was applied to measure the direct contribution of homologous Fc to the potency of monoclonal and polyclonal antitoxin preparations in mice. Homologous Fc increased the potency of three individual anti-botulinum toxin MAbs by up to one order of magnitude. Moreover, Fc fragment removal almost completely abolished the synergistic potency obtained from a combined preparation of these three MAbs. The MAb mixture neutralized a 400-mouse median lethal dose (MsLD50) of botulinum toxin, whereas the F(ab')2 combination failed to neutralize 10 MsLD50 of botulinum toxin. Notably, increased avidity did not compensate for this phenomenon, as a polyclonal, hyper-immune, homologous preparation lost 90% of its potency as well upon Fc removal. Finally, the addition of homologous Fc arms to a heterologous pharmaceutical anti-botulinum toxin polyclonal horse F(ab')2 preparation improved its efficacy when administered to intoxicated symptomatic mice. Our study extends the aspects by which switching from animal-based to human-based antitoxins will improve not only the safety but also the potency and efficacy of passive immunity against toxins.

Exploration of α1-antitrypsin treatment protocol for islet transplantation: dosing plan and route of administration.

Life-long weekly infusions of human α1-antitrypsin (hAAT) are currently administered as augmentation therapy for patients with genetic AAT deficiency (AATD). Several recent clinical trials attempt to extend hAAT therapy to conditions outside AATD, including type 1 diabetes. Since the endpoint for AATD is primarily the reduction of risk for pulmonary emphysema, the present study explores hAAT dose protocols and routes of administration in attempt to optimize hAAT therapy for islet-related injury. Islet-grafted mice were treated with hAAT (Glassia™; i.p. or s.c.) under an array of clinically relevant dosing plans. Serum hAAT and immunocyte cell membrane association were examined, as well as parameters of islet survival. Results indicate that dividing the commonly prescribed 60 mg/kg i.p. dose to three 20 mg/kg injections is superior in affording islet graft survival; in addition, a short dynamic descending dose protocol (240→120→60→60 mg/kg i.p.) is comparable in outcomes to indefinite 60 mg/kg injections. While hAAT pharmacokinetics after i.p. administration in mice resembles exogenous hAAT treatment in humans, s.c. administration better imitated the physiological progressive rise of hAAT during acute phase responses; nonetheless, only the 60 mg/kg dose depicted an advantage using the s.c. route. Taken together, this study provides a platform for extrapolating an islet-relevant clinical protocol from animal models that use hAAT to protect islets. In addition, the study places emphasis on outcome-oriented analyses of drug efficacy, particularly important when considering that hAAT is presently at an era of drug-repurposing towards an extended list of clinical indications outside genetic AATD.

Development of an Innovative in Vitro Potency Assay for Anti-Botulinum Antitoxins.

Botulinum neurotoxins are bacterial proteins that cause botulism, a life-threatening disease. Therapy relies mostly on post-intoxication antibody treatment. The only accepted method to measure the potency of, and to approve, antitoxin preparations is the mouse lethality neutralization bioassay. However, this assay is time-consuming, labor-intensive, costly, and raises ethical issues related to the large numbers of laboratory animals needed. Until now, all efforts to develop an alternative in vitro assay have not provided a valid replacement to the mouse potency assay. In the present study, we report the development of an innovative in vitro assay for determining botulinum antitoxin potency, using botulinum type B as a model. The concept of the assay is to mimic two fundamental steps in botulinum intoxication: receptor binding and catalytic activity. By simulating these steps in vitro we were able to accurately determine the potency of antitoxin preparations. The reproducibility of the assay was high with a CV < 13%. Most importantly, the antitoxin potency measured by the in vitro assay highly correlated with that measured by the standard in vivo mouse assay (r = 0.9842, p < 0.0001). Thus, this new in vitro assay has the potential to be considered, after validation, as a replacement to the mouse assay for quantitating neutralizing antibody concentrations in pharmaceutical botulinum antitoxin preparations. Future adoption of this in vitro assay would minimize the use of laboratory animals, speed up the time, and reduce the cost of botulinum antitoxin approval.

Early, Real-Time Medical Diagnosis of Botulism by Endopeptidase-Mass Spectrometry.

Botulinum toxin was detected in patient serum using Endopeptidase-mass-spectrometry assay, although all conventional tests provided negative results. Antitoxin was administered, resulting in patient improvement. Implementing this highly sensitive and rapid assay will improve preparedness for foodborne botulism and deliberate exposure.

Monoclonal Antibody Combinations that Present Synergistic Neutralizing Activity: A Platform for Next-Generation Anti-Toxin Drugs.

Monoclonal antibodies (MAbs) are among the fastest-growing therapeutics and are being developed for a broad range of indications, including the neutralization of toxins, bacteria and viruses. Nevertheless, MAbs potency is still relatively low when compared to conventional polyclonal Ab preparations. Moreover, the efficacy of an individual neutralizing MAb may significantly be hampered by the potential absence or modification of its target epitope in a mutant or subtype of the infectious agent. These limitations of individual neutralizing MAbs can be overcome by using oligoclonal combinations of several MAbs with different specificities to the target antigen. Studies conducted in our lab and by others show that such combined MAb preparation may present substantial synergy in its potency over the calculated additive potency of its individual MAb components. Moreover, oligoclonal preparation is expected to be better suited to compensating for reduced efficacy due to epitope variation. In this review, the synergistic neutralization properties of combined oligoclonal Ab preparations are described. The effect of Ab affinity, autologous Fc fraction, and targeting a critical number of epitopes, as well as the unexpected contribution of non-neutralizing clones to the synergistic neutralizing effect are presented and discussed.

α1-antitrypsin increases interleukin-1 receptor antagonist production during pancreatic islet graft transplantation.

Although islet transplantation for individuals with type 1 diabetes has been shown to yield superior blood glucose control, it remains inadequate for long-term control. This is partly due to islet injuries and stresses that can lead to beta cell loss. Inhibition of excess IL-1ß activity might minimize islet injuries, thus preserving function. The IL-1 receptor antagonist (IL-1Ra), an endogenous inhibitor of IL-1ß, protects islets from cytokine-induced necrosis and apoptosis. Therefore, an imbalance between IL-1ß and IL-1Ra might influence the courses of allogeneic and autoimmune responses to islets. Our group previously demonstrated that the circulating serine-protease inhibitor human alpha-1-antitrypsin (hAAT), the levels of which increase in circulation during acute-phase immune responses, exhibits anti-inflammatory and islet-protective properties, as well as immunomodulatory activity. In the present study, we sought to determine whether the pancreatic islet allograft-protective activity of hAAT was mediated by IL-1Ra induction. Our results demonstrated that hAAT led to a 2.04-fold increase in IL-1Ra expression in stimulated macrophages and that hAAT-pre-treated islet grafts exhibited a 4.851-fold increase in IL-1Ra transcript levels, which were associated with a moderate inflammatory profile. Unexpectedly, islets that were isolated from IL-1Ra-knockout mice and pre-treated with hAAT before grafting into wild-type mice yielded an increase in intragraft IL-1Ra expression that was presumably derived from infiltrating host cells, albeit in the absence of hAAT treatment of the host. Indeed, hAAT-pre-treated islets generated hAAT-free conditioned medium that could induce IL-1Ra production in cultured macrophages. Finally, we demonstrated that hAAT promoted a distinct phosphorylation and nuclear translocation pattern for p65, a key transcription factor required for IL-1Ra expression.

Revascularization of pancreatic islet allografts is enhanced by α-1-antitrypsin under anti-inflammatory conditions.

Pancreatic islets are a highly vascularized entity, and their transplantation into diabetic individuals requires optimal revascularization. In addition, ß-cells in islets are extremely sensitive to inflammation. α-1-Antitrypsin (AAT), a circulating serine-protease inhibitor that is available for clinical use as an affinity-purified human product, has been shown to protect islets from graft failure in mouse transplantation models and to achieve readily vascularized islet grafts. AAT is known to induce vascular endothelial growth factor (VEGF) expression and release, as well as protect from proteolytic cleavage of VEGF by elastase, promote viability of endothelial cells, and enhance migration of myocytes. Our aim was to examine whether AAT enhances vasculogenesis toward islet grafts. We employed Matrigel-islet plugs as means to introduce islets in an explantable isolated compartment and examined vessel formation, vessel maturation, and inflammatory profile of explants 9 days after implantation. Also, we examined primary epithelial cell grafts that were prepared from lungs of mice that are transgenic for human AAT. In addition, aortic ring sprouting assay was performed, and HUVEC tube formation assays were studied in the presence of AAT. Our findings indicate that islet grafts exhibit mature vessels in the presence of AAT, as demonstrated by morphology, as well as expression of endothelial CD31, smooth muscle actin (SMA), and von Willebrand factor (vWF). Epithelial cells that express human AAT achieved a similar positive outcome. Aortic ring sprouting was enhanced in AAT-treated cultures and also in cultures that contained primary epithelial cells from human AAT transgenic animals in the absence of added AAT. According to the tube formation assay, HUVECs exhibited superior responses in the presence of AAT. We conclude that vasculogenesis toward islet grafts is enhanced in the presence of AAT. Together with the remarkable safety profile of AAT, the study supports its use in the relevant clinical setups.

The mitochondrial Na+/Ca2+ exchanger upregulates glucose dependent Ca2+ signalling linked to insulin secretion.

Mitochondria mediate dual metabolic and Ca(2+) shuttling activities. While the former is required for Ca(2+) signalling linked to insulin secretion, the role of the latter in ß cell function has not been well understood, primarily because the molecular identity of the mitochondrial Ca(2+) transporters were elusive and the selectivity of their inhibitors was questionable. This study focuses on NCLX, the recently discovered mitochondrial Na(+)/Ca(2+) exchanger that is linked to Ca(2+) signalling in MIN6 and primary ß cells. Suppression either of NCLX expression, using a siRNA construct (siNCLX) or of its activity, by a dominant negative construct (dnNCLX), enhanced mitochondrial Ca(2+) influx and blocked efflux induced by glucose or by cell depolarization. In addition, NCLX regulated basal, but not glucose-dependent changes, in metabolic rate, mitochondrial membrane potential and mitochondrial resting Ca(2+). Importantly, NCLX controlled the rate and amplitude of cytosolic Ca(2+) changes induced by depolarization or high glucose, indicating that NCLX is a critical and rate limiting component in the cross talk between mitochondrial and plasma membrane Ca(2+) signalling. Finally, knockdown of NCLX expression was followed by a delay in glucose-dependent insulin secretion. These findings suggest that the mitochondrial Na(+)/Ca(2+) exchanger, NCLX, shapes glucose-dependent mitochondrial and cytosolic Ca(2+) signals thereby regulating the temporal pattern of insulin secretion in ß cells.

α-1 antitrypsin promotes semimature, IL-10-producing and readily migrating tolerogenic dendritic cells.

Tolerogenic IL-10-positive CCR7-positive dendritic cells (DC) promote T regulatory (Treg) cell differentiation upon CCR7-dependent migration to draining lymph nodes (DLN). Indeed, in human DC deficiencies, Treg levels are low. α-1 antitrypsin (AAT) has been shown to reduce inflammatory markers, promote a semimature LPS-induced DC phenotype, facilitate Treg expansion, and protect pancreatic islets from alloimmune and autoimmune responses in mice. However, the mechanism behind these activities of AAT is poorly understood. In this study, we examine interactions among DC, CD4(+) T cells, and AAT in vitro and in vivo. IL-1ß/IFN-γ-mediated DC maturation and effect on Treg development were examined using OT-II cells and human AAT (0.5 mg/ml). CCL19/21-dependent migration of isolated DC and resident islet DC was assessed, and CCR7 surface levels were examined. Migration toward DLN was evaluated by FITC skin painting, transgenic GFP skin tissue grafting, and footpad DC injection. AAT-treated stimulated DC displayed reduced MHC class II, CD40, CD86, and IL-6, but produced more IL-10 and maintained inducible CCR7. Upon exposure of CD4(+) T cells to OVA-loaded AAT-treated DC, 2.7-fold more Foxp3(+) Treg cells were obtained. AAT-treated cells displayed enhanced chemokine-dependent migration and low surface CD40. Under AAT treatment (60 mg/kg), DLN contained twice more fluorescence after FITC skin painting and twice more donor DC after footpad injection, whereas migrating DC expressed less CD40, MHC class II, and CD86. Intracellular DC IL-10 was 2-fold higher in the AAT group. Taken together, these results suggest that inducible functional CCR7 is maintained during AAT-mediated anti-inflammatory conditions. Further studies are required to elucidate the mechanism behind the favorable tolerogenic activities of AAT.

α-1-antitrypsin gene delivery reduces inflammation, increases T-regulatory cell population size and prevents islet allograft rejection.

Antiinflammatory clinical-grade, plasma-derived human α-1 antitrypsin (hAAT) protects islets from allorejection as well as from autoimmune destruction. hAAT also interferes with disease progression in experimental autoimmune encephalomyelitis (EAE) and in collagen-induced arthritis (CIA) mouse models. hAAT increases IL-1 receptor antagonist expression in human mononuclear cells and T-regulatory (Treg) cell population size in animal models. Clinical-grade hAAT contains plasma impurities, multiple hAAT isoforms and various states of inactive hAAT. We thus wished to establish islet-protective activities and effect on Treg cells of plasmid-derived circulating hAAT in whole animals. Islet function was assessed in mice that received allogeneic islet transplants after mice were given hydrodynamic tail-vein injection with pEF-hAAT, a previously described Epstein-Barr virus (EBV) plasmid construct containing the EBV nuclear antigen 1 (EBNA1) and the family of repeat EBNA1 binding site components (designated "EF") alongside the hAAT gene. Sera collected from hAAT-expressing mice were added to lipopolysaccharide (LPS)-stimulated macrophages to assess macrophage responsiveness. Also, maturation of peritoneal cells from hAAT-expressing mice was evaluated. hAAT-expressing mice accepted islet allografts (n = 11), whereas phosphate-buffered saline-injected animals (n = 11), as well as mice treated with truncated-hAAT-plasmid (n = 6) and untreated animals (n = 20) rapidly rejected islet allografts. In hAAT-expressing animals, local Treg cells were abundant at graft sites, and the IL-1 receptor antagonist was elevated in grafts and circulation. Sera from hAAT-expressing mice, but not control mice, inhibited macrophage responses. Finally, peritoneal cells from hAAT-expressing mice exhibited a semimature phenotype. We conclude that plasmid-derived circulating hAAT protects islet allografts from acute rejection, and human plasma impurities are unrelated to islet protection. Future studies may use this in vivo approach to examine the structure-function characteristics of the protective activities of AAT by manipulation of the hAAT plasmid.

Sustained expression of circulating human alpha-1 antitrypsin reduces inflammation, increases CD4+FoxP3+ Treg cell population and prevents signs of experimental autoimmune encephalomyelitis in mice.

Alpha-1-antitrypsin (AAT) is the primary circulating serine protease inhibitor, and is known to exert potent anti-inflammatory effects and to inhibit the progression of several autoimmune diseases. In this study, transgenic mice that over-express surfactant-driven human (h)AAT on the C57BL/6 background were evaluated for resistance to MOG-35-55 peptide-induced experimental autoimmune encephalomyelitis (EAE), compared to WT C57BL/6 control mice. According to the results, sustained levels of circulating hAAT profoundly inhibited induction of clinical signs, inflammatory lesions and demyelination observed in WT mice with EAE, concomitant with enhanced levels of CD4+FoxP3+ Treg cells, reduced secretion of MOG peptide-induced pro-inflammatory cytokines, IL-17, IL-1ß & IL-6, diminished expression of caspase-1 and enhanced expression of CCR6. These results implicate hAAT as a potent immunoregulatory agent worthy of further investigation as a potential therapy in human autoimmune diseases including multiple sclerosis.