Treatment of rheumatoid arthritis with humanized anti-interleukin-6 receptor antibody: A multicenter, double-blind, placebo-controlled trial

OBJECTIVE

Interleukin-6 (IL-6) is a pleiotropic cytokine that regulates the immune response, inflammation, and hematopoiesis. Overproduction of IL-6 plays pathologic roles in rheumatoid arthritis (RA), and the blockade of IL-6 may be therapeutically effective for the disease. This study was undertaken to evaluate the safety and efficacy of a humanized anti-IL-6 receptor antibody, MRA, in patients with RA.

METHODS

In a multicenter, double-blind, placebo-controlled trial, 164 patients with refractory RA were randomized to receive either MRA (4 mg/kg body weight or 8 mg/kg body weight) or placebo. MRA was administered intravenously every 4 weeks for a total of 3 months. The clinical responses were measured using the American College of Rheumatology (ACR) criteria.

RESULTS

Treatment with MRA reduced disease activity in a dose-dependent manner. At 3 months, 78% of patients in the 8-mg group, 57% in the 4-mg group, and 11% in the placebo group achieved at least a 20% improvement in disease activity according to the ACR criteria (an ACR20 response) (P < 0.001 for 8-mg group versus placebo). Forty percent of patients in the 8-mg group and 1.9% in the placebo group achieved an ACR50 response (P < 0.001). The overall incidences of adverse events were 56%, 59%, and 51% in the placebo, 4-mg, and 8-mg groups, respectively, and the adverse events were not dose dependent. A blood cholesterol increase was observed in 44.0% of the patients. Liver function disorders and decreases in white blood cell counts were also observed, but these were mild and transient. There was no increase in antinuclear antibodies or anti-DNA antibodies. Anti-MRA antibodies were detected in 2 patients.

CONCLUSION

Treatment with MRA was generally well tolerated and significantly reduced the disease activity of RA.

Humanized anti-interleukin-6 receptor antibody treatment of multicentric Castleman disease

Multicentric Castleman disease (MCD) is an atypical lymphoproliferative disorder characterized by systemic lymphadenopathy and constitutional inflammatory symptoms. Dysregulated overproduction of interleukin-6 is responsible for the clinical abnormalities. This multicenter prospective study was undertaken to evaluate the safety and efficacy of a humanized anti-human interleukin-6 (IL-6) receptor monoclonal antibody (MRA) in patients with MCD. We report here results of the first 60 weeks of the study enrolling 28 patients. The initial dosing period consisted of 8 infusions of 8 mg/kg MRA administered biweekly. Adjustments in the dose and treatment interval were allowed for each patient in an extension phase after 16 weeks. Within 16 weeks, treatment with MRA consistently alleviated lymphadenopathy and all the inflammatory parameters. Hemoglobin, albumin, and total cholesterol levels, high-density lipoprotein cholesterol values, and body mass index all increased significantly. In addition, fatigue diminished. Chronic inflammatory symptoms were successfully managed over 60 weeks. In 8 (28.6%) patients, the MRA dose was decreased or the treatment interval was extended without exacerbation. Eleven (73.3%) of 15 patients who had received oral corticosteroids before study entry were able to do well on a reduced corticosteroid dose. Most adverse events were mild to moderate in severity. MRA was tolerated well and significantly alleviated chronic inflammatory symptoms and wasting in patients with MCD.

Anti-PEG antibodies: Properties, formation, testing and role in adverse immune reactions to PEGylated nano-biopharmaceuticals

Conjugation of polyethylene glycols (PEGs) to proteins or drug delivery nanosystems is a widely accepted method to increase the therapeutic index of complex nano-biopharmaceuticals. Nevertheless, these drugs and agents are often immunogenic, triggering the rise of anti-drug antibodies (ADAs). Among these ADAs, anti-PEG IgG and IgM were shown to account for efficacy loss due to accelerated blood clearance of the drug (ABC phenomenon) and hypersensitivity reactions (HSRs) entailing severe allergic symptoms with occasionally fatal anaphylaxis. In addition to recapitulating the basic information on PEG and its applications, this review expands on the physicochemical factors influencing its immunogenicity, the prevalence, features, mechanism of formation and detection of anti-PEG IgG and IgM and the mechanisms by which these antibodies (Abs) induce ABC and HSRs. In particular, we highlight the in vitro, animal and human data attesting to anti-PEG Ab-induced complement (C) activation as common underlying cause of both adverse effects. A main message is that correct measurement of anti-PEG Abs and individual proneness for C activation might predict the rise of adverse immune reactions to PEGylated drugs and thereby increase their efficacy and safety.

Inflammatory cell adhesion molecules in ischemic cerebrovascular disease

BACKGROUND

In this review we discuss the role of inflammatory cell adhesion molecules (CAMs) in ischemic stroke and in delayed cerebral ischemia after subarachnoid hemorrhage. Vascular endothelial cells and leukocytes express several inflammatory adhesion receptors, the most important of which are the selectins, immunoglobulin gene superfamily CAMs, and beta2 integrins. They mediate the transmigration process of leukocytes to the abluminal side of the endothelium.

SUMMARY OF REVIEW

There is ample evidence from animal models of middle cerebral artery occlusion that expression of CAMs is associated with cerebral infarct size. Absence of CAMs in knockout animals resulted in reduced infarct size. When middle cerebral artery occlusion in experimental stroke was followed by reperfusion, administration of anti-CAM antibodies decreased infarct size. Thus far, anti-CAM treatment has not been successful in patients with ischemic stroke. Inflammatory CAM may also play a role in the pathogenesis of delayed cerebral ischemia after subarachnoid hemorrhage. In animal models, increased expression of CAMs has been observed in vasospastic arteries. Increased concentrations of CAMs have also been found in cerebrospinal fluid of patients with subarachnoid hemorrhage.

CONCLUSIONS

Further research on the role of inflammatory CAMs in the pathogenesis of ischemic cerebrovascular disorders should lead to new diagnostic and therapeutic strategies.

Antibodies to watch in 2021

In this 12th annual installment of the Antibodies to Watch article series, we discuss key events in antibody therapeutics development that occurred in 2020 and forecast events that might occur in 2021. The coronavirus disease 2019 (COVID-19) pandemic posed an array of challenges and opportunities to the healthcare system in 2020, and it will continue to do so in 2021. Remarkably, by late November 2020, two anti-SARS-CoV antibody products, bamlanivimab and the casirivimab and imdevimab cocktail, were authorized for emergency use by the US Food and Drug Administration (FDA) and the repurposed antibodies levilimab and itolizumab had been registered for emergency use as treatments for COVID-19 in Russia and India, respectively. Despite the pandemic, 10 antibody therapeutics had been granted the first approval in the US or EU in 2020, as of November, and 2 more (tanezumab and margetuximab) may be granted approvals in December 2020.* In addition, prolgolimab and olokizumab had been granted first approvals in Russia and cetuximab saratolacan sodium was first approved in Japan. The number of approvals in 2021 may set a record, as marketing applications for 16 investigational antibody therapeutics are already undergoing regulatory review by either the FDA or the European Medicines Agency. Of these 16 mAbs, 11 are possible treatments for non-cancer indications and 5 are potential treatments for cancer. Based on the information publicly available as of November 2020, 44 antibody therapeutics are in late-stage clinical studies for non-cancer indications, including 6 for COVID-19, and marketing applications for at least 6 (leronlimab, tezepelumab, faricimab, ligelizumab, garetosmab, and fasinumab) are planned in 2021. In addition, 44 antibody therapeutics are in late-stage clinical studies for cancer indications. Of these 44, marketing application submissions for 13 may be submitted by the end of 2021. *Note added in proof on key events announced during December 1-21, 2020: margetuximab-cmkb and ansuvimab-zykl were approved by FDA on December 16 and 21, 2020, respectively; biologics license applications were submitted for ublituximab and amivantamab.

Reducing the renal uptake of radiolabeled antibody fragments and peptides for diagnosis and therapy: present status, future prospects and limitations

Elevated renal uptake and prolonged retention of radiolabeled antibody fragments and peptides is a problem in the therapeutic application of such agents. Over recent years, one of the focuses of research has therefore been to develop suitable methods to reduce this renal uptake, and to evaluate whether the resulting methodology will benefit therapy with antibody fragments and peptides. In these studies it has been shown that the kidney uptake of antibody fragments in animals can be reduced in a dose-dependent manner by almost one order of magnitude by the systemic administration of cationic amino acids and their derivatives, whereas the uptake in all other organs, as well as the tumor, remains unaffected. A similar reduction in renal retention is achieved for all intracellularly retained radionuclides (e.g., radiometals) or radioiodinated immunoconjugates, as well as for smaller peptides. Lysine is usually the preferred agent, and its d- and l-isomers are equally effective whether given intraperitoneally or orally. Amino sugars are effective, but their N-acetyl derivatives, lacking the positive charge, are not. Basic polypeptides are also effective, and their potency increases with increasing molecular weight (i.e., the amount of positive charges per molecule). Urine analysis of treated individuals shows the excretion of unmetabolized, intact fragments or peptides, in contrast to mostly low-molecular-weight metabolites in untreated controls. In therapy studies using radiometal-conjugated Fab fragments, the kidney is the first dose-limiting organ. Administration of cationic amino acids results in a substantial increase in the maximum tolerated dose of such Fab fragments. No biochemical or histological evidence of renal damage has been observed under these conditions. As was the case in animal studies, in pilot clinical trials the renal uptake in patients injected with Fab' fragments and given amino acids could be decreased significantly, whereas the uptake by all other organs remained unaffected. These recent studies indicate that a variety of basic compounds are capable of inhibiting the tubular reabsorption of peptides and proteins, thus significantly lowering the renal uptake of antibody fragments or peptides in both animals and patients. On a molecular basis, the effect seems to rely essentially on the presence of a positively charged amino group. Thus, radiation nephrotoxicity of antibody fragments and peptides can be overcome successfully; this may provide new prospects for cancer therapy with radiolabeled antibody fragments and peptides.

Bleeding complications with the chimeric antibody to platelet glycoprotein IIb/IIIa integrin in patients undergoing percutaneous coronary intervention. EPIC Investigators

BACKGROUND

The potential for novel antiplatelet and antithrombin agents to contribute to periprocedural bleeding complications of percutaneous coronary revascularization is poorly defined. In the Evaluation of c7E3 Fab in Preventing Ischemic Complications of High-Risk Angioplasty (EPIC) trial, the periprocedural use of aspirin, heparin, and a chimeric antibody to the platelet glycoprotein IIb/IIIa integrin c7E3 Fab in 2099 patients significantly reduced postprocedural ischemic complications and 6-month clinical restenosis but was associated with increased procedural bleeding complications. We review these complications and describe clinical and procedural variables associated with increased bleeding complications in the EPIC trial.

METHODS AND RESULTS

Patients with high-risk clinical or lesion morphological characteristics were randomized to receive placebo bolus plus placebo infusion, c7E3 Fab bolus plus placebo infusion, or c7E3 Fab bolus plus c7E3 Fab infusion. Patients received periprocedural aspirin and intravenous heparin continued for a minimum of 12 hours after the procedure. Outcomes reflecting bleeding complications were measured: transfusions, decreased hemoglobin, and an index including both parameters. Major bleeding complications unrelated to bypass surgery occurred in 3.3%, 8.6%, and 10.6%, and blood product transfusions were used in 7.5%, 14.0%, and 16.8% of patients treated with placebo, bolus c7E3 Fab, and bolus plus infusion c7E3 Fab, respectively (both P < .001). Most major bleeding complications occurred at the femoral access site, regardless of treatment. Intracranial hemorrhage (0.3%) and death (0.09%) attributable to major bleeding complications were rare. Multivariable regression analyses identified several variables significantly and independently related to major bleeding complications or greater blood loss, including greater age, female sex, lower weight, c7E3 Fab therapy, and duration and complexity of the index procedure. Major bleeding complications and blood loss in patients receiving bolus plus infusion were not significantly greater than in those receiving bolus alone (P = .38 and P = .14, respectively).

CONCLUSIONS

Bleeding complications unrelated to bypass surgery were two to three times more frequent in patients receiving c7E3 Fab than in those receiving placebo, but most were transient and well tolerated. Risk-factor analysis and modification of concomitant antithrombotic and antiplatelet treatment strategies may aid in reducing bleeding complications and enhancing clinical benefit in patients receiving c7E3 Fab during percutaneous coronary revascularization.

Immunological responses to exogenous insulin

Regardless of purity and origin, therapeutic insulins continue to be immunogenic in humans. However, severe immunological complications occur rarely, and less severe events affect a small minority of patients. Insulin autoantibodies (IAAs) may be detectable in insulin-naive individuals who have a high likelihood of developing type 1 diabetes or in patients who have had viral disorders, have been treated with various drugs, or have autoimmune disorders or paraneoplastic syndromes. This suggests that under certain circumstances, immune tolerance to insulin can be overcome. Factors that can lead to more or less susceptibility to humoral responses to exogenous insulin include the recipient's immune response genes, age, the presence of sufficient circulating autologous insulin, and the site of insulin delivery. Little proof exists, however, that the development of insulin antibodies (IAs) to exogenous insulin therapy affects integrated glucose control, insulin dose requirements, and incidence of hypoglycemia, or contributes to beta-cell failure or to long-term complications of diabetes. Studies in which pregnant women with diabetes were monitored for glycemic control argue against a connection between IAs and fetal risk. Although studies have shown increased levels of immune complexes in patients with diabetic microangiopathic complications, these immune complexes often do not contain insulin or IAs, and insulin administration does not contribute to their formation. The majority of studies have shown no relationship between IAs and diabetic angiopathic complications, including nephropathy, retinopathy, and neuropathy. With the advent of novel insulin formulations and delivery systems, such as insulin pumps and inhaled insulin, examination of these issues is increasingly relevant.

Phase 1 Trial of Antibody NI006 for Depletion of Cardiac Transthyretin Amyloid

BACKGROUND

Transthyretin amyloid (ATTR) cardiomyopathy is a progressive and fatal disease caused by misfolded transthyretin. Despite advances in slowing disease progression, there is no available treatment that depletes ATTR from the heart for the amelioration of cardiac dysfunction. NI006 is a recombinant human anti-ATTR antibody that was developed for the removal of ATTR by phagocytic immune cells.

METHODS

In this phase 1, double-blind trial, we randomly assigned (in a 2:1 ratio) 40 patients with wild-type or variant ATTR cardiomyopathy and chronic heart failure to receive intravenous infusions of either NI006 or placebo every 4 weeks for 4 months. Patients were sequentially enrolled in six cohorts that received ascending doses (ranging from 0.3 to 60 mg per kilogram of body weight). After four infusions, patients were enrolled in an open-label extension phase in which they received eight infusions of NI006 with stepwise increases in the dose. The safety and pharmacokinetic profiles of NI006 were assessed, and cardiac imaging studies were performed.

RESULTS

The use of NI006 was associated with no apparent drug-related serious adverse events. The pharmacokinetic profile of NI006 was consistent with that of an IgG antibody, and no antidrug antibodies were detected. At doses of at least 10 mg per kilogram, cardiac tracer uptake on scintigraphy and extracellular volume on cardiac magnetic resonance imaging, both of which are imaging-based surrogate markers of cardiac amyloid load, appeared to be reduced over a period of 12 months. The median N-terminal pro-B-type natriuretic peptide and troponin T levels also seemed to be reduced.

CONCLUSIONS

In this phase 1 trial of the recombinant human antibody NI006 for the treatment of patients with ATTR cardiomyopathy and heart failure, the use of NI006 was associated with no apparent drug-related serious adverse events. (Funded by Neurimmune; NI006-101 ClinicalTrials.gov number, NCT04360434.).

Glomerular expression of nephrin and synaptopodin, but not podocin, is decreased in kidney sections from women with preeclampsia

BACKGROUND

Preeclampsia is a pregnancy-specific disorder characterized by hypertension and proteinuria. In other disease states, proteinuria has been linked to altered expressions of podocyte foot-process proteins, but this has not been studied in women with preeclampsia. We sought to test the hypothesis that proteinuria in preeclampsia is associated with dysregulated expression of the podocyte cytoskeleton and/or tight junction proteins.

METHODS

Renal tissue was obtained from autopsy material from seven women who had severe preeclampsia during the second half of their pregnancies up to 48 h after delivery, and who subsequently died. As controls, we used autopsy material from two women who died accidentally during the second half of their otherwise normal pregnancies. Immunohistochemical stains for nephrin, synaptopodin and podocin were performed on representative sections prepared from paraffin-embedded material.

RESULTS

Expression of both nephrin and synaptopodin was markedly decreased in preeclamptic compared with control kidney sections. By contrast, both cases and controls demonstrated strong staining for podocin.

CONCLUSIONS

We conclude that down-regulation of nephrin and synaptopodin is associated with proteinuria in women with preeclampsia. Recent studies have demonstrated that soluble vascular endothelial growth factor receptor 1 (sFlt-1) levels are elevated in preeclampsia compared with normal pregnancy. Studies in mice have shown that sFlt-1 may play a role in inducing proteinuria by neutralizing vascular endothelial growth factor (VEGF) and suppressing nephrin. Proteinuria and elevations of sFlt-1 in preeclampsia are temporally related, further supporting a possible role of sFlt-1 in the dysregulation of podocyte foot-process proteins.

Anti-platelet factor 4 antibodies causing VITT do not cross-react with SARS-CoV-2 spike protein

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a severe adverse effect of ChAdOx1 nCoV-19 COVID-19 vaccine (Vaxzevria) and Janssen Ad26.COV2.S COVID-19 vaccine, and it is associated with unusual thrombosis. VITT is caused by anti-platelet factor 4 (PF4) antibodies activating platelets through their FcγRIIa receptors. Antibodies that activate platelets through FcγRIIa receptors have also been identified in patients with COVID-19. These findings raise concern that vaccination-induced antibodies against anti-SARS-CoV-2 spike protein cause thrombosis by cross-reacting with PF4. Immunogenic epitopes of PF4 and SARS-CoV-2 spike protein were compared using in silico prediction tools and 3D modeling. The SARS-CoV-2 spike protein and PF4 share at least 1 similar epitope. Reactivity of purified anti-PF4 antibodies from patients with VITT was tested against recombinant SARS-CoV-2 spike protein. However, none of the affinity-purified anti-PF4 antibodies from 14 patients with VITT cross-reacted with SARS-CoV-2 spike protein. Sera from 222 polymerase chain reaction-confirmed patients with COVID-19 from 5 European centers were tested by PF4-heparin enzyme-linked immunosorbent assays and PF4-dependent platelet activation assays. We found anti-PF4 antibodies in sera from 19 (8.6%) of 222 patients with COVID-19. However, only 4 showed weak to moderate platelet activation in the presence of PF4, and none of those patients developed thrombotic complications. Among 10 (4.5%) of 222 patients who had COVID-19 with thrombosis, none showed PF4-dependent platelet-activating antibodies. In conclusion, antibodies against PF4 induced by vaccination do not cross-react with the SARS-CoV-2 spike protein, indicating that the intended vaccine-induced immune response against SARS-CoV-2 spike protein is not the trigger of VITT. PF4-reactive antibodies found in patients with COVID-19 in this study were not associated with thrombotic complications.

Significance of immune response to enzyme-replacement therapy for patients with a lysosomal storage disorder

Lysosomal storage disorders are collectively important because they cause significant morbidity and mortality. Patients can present with severe symptoms that include somatic tissue and bone pathology, developmental delay and neurological impairment. Enzyme-replacement therapy has been developed as a treatment strategy for patients with a lysosomal storage disorder, and for many of these disorders this treatment is either in clinical trial or clinical practice. One major complication arising from enzyme infusion into patients with a lysosomal storage disorder is an immune response to the replacement protein. From clinical trials, it is clear that there is considerable variability in the level of immune response to enzyme-replacement therapy, dependent upon the replacement protein being infused and the individual patient. Hypersensitivity reactions, neutralizing antibodies to the replacement protein and altered enzyme targeting or turnover are potential concerns for patients exhibiting an immune response to enzyme-replacement therapy. The relative occurrence and significance of these issues have been appraised.

Endogenous leukemia inhibitory factor production limits autoimmune demyelination and oligodendrocyte loss

Autoimmune injury to oligodendrocytes evokes an endogenous response in the central nervous system, which initially limits the acute injury to oligodendrocytes and myelin, and subsequently promotes remyelination. The key molecular and cellular events responsible for this beneficial outcome are incompletely understood. In this article, we utilize murine autoimmune encephalomyelitis (EAE) to focus on the effect of endogenously produced leukemia inhibitory factor (LIF) upon mature oligodendrocyte survival after demyelinating injury. We show that the mRNA for LIF is markedly upregulated in the spinal cord in the context of acute inflammatory demyelination. After clinical disease onset, administration of neutralizing anti-LIF antibodies over a four day period significantly worsens disease severity in two different murine EAE models. We also show that administration of neutralizing antibodies results in reduced activation of the cognate LIF receptor components in the spinal cord. Histologically, anti-LIF antibody administration increases the extent of acute demyelination (P < 0.01) and doubles the oligodendrocyte loss already induced by EAE (P < 0.05), without altering the extent of inflammatory infiltration into the spinal cord. Although acute EAE induces a rapid, three-fold increase in the proliferation of NG2 positive oligodendrocyte progenitors (P < 0.001), this response is not diminished by antagonism of endogenous LIF. We conclude that endogenous LIF is induced in response to autoimmune demyelination in the spinal cord and protects mature oligodendrocytes from demyelinating injury and cell death, thereby resulting in attenuation of clinical disease severity.

Targeting the Notch Signaling Pathway in Chronic Inflammatory Diseases

The Notch signaling pathway regulates developmental cell-fate decisions and has recently also been linked to inflammatory diseases. Although therapies targeting Notch signaling in inflammation in theory are attractive, their design and implementation have proven difficult, at least partly due to the broad involvement of Notch signaling in regenerative and homeostatic processes. In this review, we summarize the supporting role of Notch signaling in various inflammation-driven diseases, and highlight efforts to intervene with this pathway by targeting Notch ligands and/or receptors with distinct therapeutic strategies, including antibody designs. We discuss this in light of lessons learned from Notch targeting in cancer treatment. Finally, we elaborate on the impact of individual Notch members in inflammation, which may lay the foundation for development of therapeutic strategies in chronic inflammatory diseases.

Novel complement inhibitor limits severity of experimentally myasthenia gravis

OBJECTIVE

Complement mediated injury of the neuromuscular junction is considered a primary disease mechanism in human myasthenia gravis and animal models of experimentally acquired myasthenia gravis (EAMG). We utilized active and passive models of EAMG to investigate the efficacy of a novel C5 complement inhibitor rEV576, recombinantly produced protein derived from tick saliva, in moderating disease severity.

METHODS

Standardized disease severity assessment, serum complement hemolytic activity, serum cytotoxicity, acetylcholine receptor (AChR) antibody concentration, IgG subclassification, and C9 deposition at the neuromuscular junction were used to assess the effect of complement inhibition on EAMG induced by administration of AChR antibody or immunization with purified AChR.

RESULTS

Administration of rEV576 in passive transfer EAMG limited disease severity as evidenced by 100% survival rate and a low disease severity score. In active EAMG, rats with severe and mild EAMG were protected from worsening of disease and had limited weight loss. Serum complement activity (CH(50)) in severe and mild EAMG was reduced to undetectable levels during treatment, and C9 deposition at the neuromuscular junction was reduced. Treatment with rEV576 resulted in reduction of toxicity of serum from severe and mild EAMG rats. Levels of total AChR IgG, and IgG(2a) antibodies were similar, but unexpectedly, the concentration of complement fixing IgG(1) antibodies was lower in a group of rEV576-treated animals, suggesting an effect of rEV576 on cellular immunity.

INTERPRETATION

Inhibition of complement significantly reduced weakness in two models of EAMG. C5 inhibition could prove to be of significant therapeutic value in human myasthenia gravis.

Pemphigus vulgaris and pemphigus foliaceus antibodies are pathogenic in plasminogen activator knockout mice

Previous studies have suggested that urokinase plasminogen activator is required for blister formation in pemphigus vulgaris and pemphigus foliaceus. Other studies, however, have shown that downregulation of plasminogen activator does not inhibit blisters induced by pemphigus immunoglobulin G. To eliminate the possibility that small amounts of urokinase plasminogen activator might be sufficient for blister formation, we passively transferred pemphigus immunoglobulin G to urokinase plasminogen activator knockout neonatal mice. Pemphigus foliaceus and pemphigus vulgaris immunoglobulin G caused gross blisters and acantholysis in the superficial and suprabasal epidermis, respectively, to the same degree in knockout and control mice, demonstrating that urokinase plasminogen activator is not absolutely required for antibody-induced blisters. Some studies have shown elevated tissue-type plasminogen activator in pemphigus lesions. Tissue-type plasminogen activator, however, is not necessary for blister formation, because pemphigus foliaceus and pemphigus vulgaris immunoglobulin G caused blisters to the same degree in tissue-type plasminogen activator knockout and control mice. To rule out that one plasminogen activator might compensate for the other in the knockout mice, we bred urokinase plasminogen activator, tissue-type plasminogen activator double knockouts. After passive transfer of pemphigus foliaceus and pemphigus vulgaris immunoglobulin G these mice blistered to the same degree as the single knockout and control mice, and histology indicated blisters at the expected level of the epidermis. These data definitively demonstrate that plasminogen activator is not necessary for pemphigus immunoglobulin G to induce acantholysis in the neonatal mouse model of pemphigus.

Protective roles of mast cells and mast cell-derived TNF in murine malaria

TNF plays important roles in the protection and onset of malaria. Although mast cells are known as a source of TNF, little is known about the relationship between mast cells and pathogenesis of malaria. In this study, mast cell-deficient WBB6F1-W/W(v) (W/W(v)) and the control littermate WBB6F1+/+ (+/+) mice were infected with 1 x 10(5) of Plasmodium berghei ANKA. +/+ mice had lower parasitemia with higher TNF levels, as compared with W/W(v) mice. Diminished resistance in W/W(v) mice was considered to be due to mast cells and TNF. This fact was confirmed by experiments in W/W(v) mice reconstituted with bone marrow-derived mast cells (BMMCs) of +/+ mice or of TNF-/- mice. W/W(v) mice with BMMCs of +/+ mice exhibit lower parasitemia and mortality accompanying significantly higher TNF levels than those of W/W(v) mice. Parasitemia in W/W(v) mice with BMMCs of TNF-/- mice was higher than that in +/+ mice. Activation of mast cells by anti-IgE or compound 48/80 resulted in release of TNF and decrease of parasitemia. In addition, splenic hypertrophy and increased number of mast cells in the spleen were observed after infection in +/+ mice and W/W(v) mice reconstituted with BMMCs of +/+ mice as compared with W/W(v) mice. These findings propose a novel mechanism that mast cells and mast cell-derived TNF play protective roles in malaria.

Brain Disposition of Antibody-Based Therapeutics: Dogma, Approaches and Perspectives

Due to their high specificity, monoclonal antibodies have been widely investigated for their application in drug delivery to the central nervous system (CNS) for the treatment of neurological diseases such as stroke, Alzheimer’s, and Parkinson’s disease. Research in the past few decades has revealed that one of the biggest challenges in the development of antibodies for drug delivery to the CNS is the presence of blood–brain barrier (BBB), which acts to restrict drug delivery and contributes to the limited uptake (0.1–0.2% of injected dose) of circulating antibodies into the brain. This article reviews the various methods currently used for antibody delivery to the CNS at the preclinical stage of development and the underlying mechanisms of BBB penetration. It also describes efforts to improve or modulate the physicochemical and biochemical properties of antibodies (e.g., charge, Fc receptor binding affinity, and target affinity), to adapt their pharmacokinetics (PK), and to influence their distribution and disposition into the brain. Finally, a distinction is made between approaches that seek to modify BBB permeability and those that use a physiological approach or antibody engineering to increase uptake in the CNS. Although there are currently inherent difficulties in developing safe and efficacious antibodies that will cross the BBB, the future prospects of brain-targeted delivery of antibody-based agents are believed to be excellent.

Osthole prevents anti-Fas antibody-induced hepatitis in mice by affecting the caspase-3-mediated apoptotic pathway

Fas (Apo-1/CD95) ligand, which is a type II membrane protein, is a major inducer of apoptosis. Osthole is a coumarin derivative present in medicinal plants. The effect of osthole on hepatitis induced by anti-Fas antibody in mice was studied. Pretreatment of mice with osthole (10, 50, and 100 mg/kg, i.p.) prevented the elevation of plasma alanine aminotransferase (ALT) caused by anti-Fas antibody (175 microg/kg, i.v.). Administration of osthole to mice even at a dose of 10 mg/kg significantly inhibited of anti-Fas antibody-induced elevation of plasma ALT. Capase-3 is a cysteine protease, and treatment of mice with anti-Fas antibody caused an elevation of caspase-3 activity at 3.5 and 6 hr. Pretreatment of mice with osthole (100 mg/kg, i.p.) inhibited the elevation of caspase-3 activity caused by anti-Fas antibody. However, the addition of osthole (up to 10(-4)M) to a liver cytosol fraction isolated from mice treated with anti-Fas antibody did not inhibit caspase-3 activity in vitro. Thus, treatment of mice with osthole inhibited caspase-3 activity by an effect upstream of caspase-3 activation. The livers of mice treated with anti-Fas antibody contained apoptotic and dead cells; osthole attenuated the development of this apoptosis and cell death. The present results show that osthole prevented anti-Fas antibody-induced hepatitis by inhibiting the Fas-mediated apoptotic pathway.

CD25 regulatory T cells determine secondary but not primary remission in EAE: Impact on long-term disease progression

Multiple sclerosis (MS) is often characterized by several relapses and remissions during long-term disease, but neither the responsible cells nor the mechanisms are known to date. Using an animal model of multiple sclerosis, relapsing experimental autoimmune encephalomyelitis (R-EAE) CD4+CD25+ Treg cells expressing Foxp3 and CTLA-4 intracellularly and T lymphocytes expressing surface CTLA-4 were identified in the CNS. The first remission occurred even after depletion of Treg cells, but secondary remissions from EAE were ablated. Despite the unaltered first remission autoantigen rechallenge revealed already an amplified cytokine response during acute phase. These results indicate that the cellular composition during first attack of MS predicts long-term disease progression.