Intravenous immunoglobulin in neurological disorders: a mechanistic perspective

Mechanisms of action of intravenous immunoglobulin in septic encephalopathy

Acute brain dysfunction associated with sepsis is a serious complication that results in morbidity and mortality. Intravenous immunoglobulin (IVIg) treatment is known to alleviate behavioral deficits in the experimentally induced model of sepsis. To delineate the mechanisms by which IVIg treatment prevents neuronal dysfunction, an array of immunological and apoptosis markers was investigated. Our results suggest that IVIgG and IgGAM administration ameliorates neuronal dysfunction and behavioral deficits by reducing apoptotic cell death and glial cell proliferation. IgGAM treatment might suppress classical complement pathway by reducing C5a activity and proapoptotic NF-κB and Bax expressions, thereby, inhibiting major inflammation and apoptosis cascades. Future animal model experiments performed with specific C5aR and NF-κB agonists/antagonists or C5aR-deficient mice might more robustly disclose the significance of these pathways. C5a, C5aR, and NF-κB, which were shown to be the key molecules in brain injury pathogenesis in sepsis, might also be utilized as potential targets for future treatment trials of septic encephalopathy.

Evaluation and treatment of Langerhans cell histiocytosis patients with central nervous system abnormalities: Current views and new vistas

Central nervous system (CNS) involvement in Langerhans cell histiocytosis (LCH) can include mass lesions of the hypothalamic pituitary axis, choroid plexus, cerebrum, and cerebellum or magnetic resonance imaging (MRI) signal abnormalities of the cerebellum, pons, and basal ganglia. The term neurodegenerative (ND) CNS-LCH has been given to the MRI signal abnormalities and neurologic dysfunction, although initially patients may have no clinical symptoms. Standardized evaluations to better understand the natural history and response to therapy are needed. We propose guidelines for clinical, radiologic, and physiologic tests as a framework for developing the best methods of evaluation, which can then be tested in prospective treatment protocols.

Development, manufacturing and characterization of a highly purified, liquid immunoglobulin g preparation from human plasma

BACKGROUND

The use of plasma-derived immunoglobulin G (IgG) is increasing, and the number of diseases, including immunodeficiencies, neurological diseases and autoimmune conditions, treated with intravenous IgG (IVIG) is expanding. Consequently, there is a great need for high-yield production processes for plasma-derived IgG. The aim of this work was to develop a high-yield process leading to a highly purified, liquid, ready-to-use IgG for intravenous use.

METHODS

Plasma from healthy, voluntary, non-remunerated donors was fractionated by ethanol precipitation. IgG was extracted from fraction II + III using a phosphate/acetate buffer, pH 4, and purified by chromatography.

RESULTS

Precipitation with 6% polyethylene glycol at pH 7 removed high molecular-weight contaminating proteins, aggregates and contaminating viruses. Ion exchange chromatography at pH 5.7 on serially connected anion and cation exchange columns allowed for elution of IgG from the cation exchange column in good yield and high purity. Further safety was achieved by solvent/detergent treatment and repeated ion exchange chromatography. The product consisted of essentially only IgG monomers and dimers, and had a high purity with very low levels of IgM and IgA.

CONCLUSION

A process providing highly purified IVIG in good yield was developed.

Treatment of spinal cord injury with intravenous immunoglobulin G: preliminary evidence and future perspectives

Neuroinflammation plays an important role in the secondary pathophysiological mechanisms of spinal cord injury (SCI) and can exacerbate the primary trauma and thus worsen recovery. Although some aspects of the immune response are beneficial, it is thought that leukocyte recruitment and activation in the acute phase of injury results in the production of cytotoxic substances that are harmful to the nervous tissue. Therefore, suppression of excessive inflammation in the spinal cord could serve as a therapeutic strategy to attenuate tissue damage. The immunosuppressant methylprednisolone has been used in the setting of SCI, but there are complications which have attenuated the initial enthusiasm. Hence, there is interest in other immunomodulatory approaches, such as intravenous Immunoglobulin G (IVIg). Importantly, IVIg is used clinically for the treatment of several auto-immune neuropathies, such as Guillain-Barre syndrome, chronic inflammatory demyelinating polyneuropathy (CIPD) and Kawasaki disease, with a good safety profile. Thus, it is a promising treatment candidate for SCI. Indeed, IVIg has been shown by our team to attenuate the immune response and result in improved neurobehavioral recovery following cervical SCI in rats through a mechanism that involves the attenuation of neutrophil recruitment and reduction in the levels of cytokines and cytotoxic enzymes Nguyen et al. (J Neuroinflammation 9:224, 2012). Here we review published data in the context of relevant mechanisms of action that have been proposed for IVIg in other conditions. We hope that this discussion will trigger future research to provide supporting evidence for the efficiency and detailed mechanisms of action of this promising drug in the treatment of SCI, and to facilitate its clinical translation.

[Intravenous immunoglobulin: immunomodulatory key of the immune system]

The mechanisms of action of intravenous immunoglobulins (IVIG) are complex and mostly reproduce those of the natural immunoglobulin G (IgG) in our organism. The therapeutic doses used range from substitutive (200-400mg/kg of body weight) in immunodeficiencies to high doses (1-2g/kg of body weight) in autoimmune or inflammatory diseases. The paradoxical pro- or anti-inflammatory effects of IVIG are based on the modulation of the expression of activating versus inhibitory Fc receptors, the type and stage of maturation of the target cell. This huge diversity of actions may explain the extensive and varied range of clinical applications of IVIG nowadays (immunodeficiencies, autoimmune diseases, degenerative diseases such as Alzheimer's, and cancer). On the other hand, biological therapies with monoclonal antibodies mostly consist of IgG molecules with unique antigen specificity, and currently represent a therapeutic field expanding in various pathologies including cancer and diseases of immunological basis. The effects of IgG are added to their specific effects on molecules target.

Intravenous immunoglobulin therapy prevents development of autoimmune encephalomyelitis and suppresses activation of matrix metalloproteinases

Although intravenous immunoglobulin (IVIG) has been reported to improve the status of expanded disability status scale (EDSS) of multiple sclerosis (MS) patients and reduce the annual relapse rate, some studies did not find its beneficial effects. In the present study, using an animal model for MS, we found that prophylactic, but not therapeutic, treatment successfully suppressed the disease development. During the search for factors involved in the disease suppression by IVIG, we obtained evidence suggesting that IVIG exerts its function, at least in part, by suppressing activation of matrix metalloproteinases (MMP)-2 and -9. Gelatin zymography revealed that gelatinase activities were suppressed by IVIG treatment in the spinal cord, but not in plasma. This finding raises the possibility that IVIG blocks MMP activities at the interface between the blood stream and CNS. With in situ zymography, we also observed that gelatinase activities were expressed mainly in astrocytes in the inflamed spinal cord of control rats and that this expression was attenuated by the treatment. These findings provide useful information to set optimal conditions for IVIG treatment of MS and to obtain more beneficial effects.

Neuroprotection in stroke by complement inhibition and immunoglobulin therapy

Activation of the complement system occurs in a variety of neuroinflammatory diseases and neurodegenerative processes of the CNS. Studies in the last decade have demonstrated that essentially all of the activation components and receptors of the complement system are produced by astrocytes, microglia, and neurons. There is also rapidly growing evidence to indicate an active role of the complement system in cerebral ischemic injury. In addition to direct cell damage, regional cerebral ischemia and reperfusion (I/R) induces an inflammatory response involving complement activation and generation of active fragments, such as C3a and C5a anaphylatoxins, C3b, C4b, and iC3b. The use of specific inhibitors to block complement activation or their mediators such as C5a, can reduce local tissue injury after I/R. Consistent with therapeutic approaches that have been successful in models of autoimmune disorders, many of the same complement inhibition strategies are proving effective in animal models of cerebral I/R injury. One new form of therapy, which is less specific in its targeting of complement than monodrug administration, is the use of immunoglobulins. Intravenous immunoglobulin (IVIG) has the potential to inhibit multiple components of inflammation, including complement fragments, pro-inflammatory cytokine production and leukocyte cell adhesion. Thus, IVIG may directly protect neurons, reduce activation of intrinsic inflammatory cells (microglia) and inhibit transendothelial infiltration of leukocytes into the brain parenchyma following an ischemic stroke. The striking neuroprotective actions of IVIG in animal models of ischemic stroke suggest a potential therapeutic potential that merits consideration for clinical trials in stroke patients.

Stability over 36 months of a new liquid 10% polyclonal immunoglobulin product (IgPro10, Privigen) stabilized with L-proline

BACKGROUND AND OBJECTIVES

IgPro10 (Privigen) is a new liquid intravenous immunoglobulin (IVIG) product that is formulated with 250 mM L-proline at pH 4.8. A 3-year study was performed to assess its stability.

MATERIALS AND METHODS

Physicochemical, biological and immunological parameters of Privigen were assessed during storage under controlled conditions over up to 36 months at 25 degrees C.

RESULTS

Privigen was shown to be stable after storage for 3 years at room temperature (25 degrees C). Of all parameters tested, only a few showed changes during storage. The appearance of the solution complied with the specifications given by the European Pharmacopeia over the full study period, with a single exception. The IgG fraction in Privigen displayed high purity (> or = 98%), which did not change during storage over 36 months. No relevant amounts of aggregated IgG molecules were formed in Privigen samples and the ratio between monomers and dimers shifted slightly towards the equilibrium over time. Testing of reference antibody contents and the Fc function demonstrated that the biological activity and effector functions of Privigen were preserved over the full study period of 36 months.

CONCLUSION

Thirty-six months room temperature stability of Privigen was achieved at pH 4.8 with an innovative formulation containing the physiological stabilizer L-proline.

New advances in the treatment of neurological diseases using high dose intravenous immunoglobulins

Since the incidental discovery in 1981 that intravenous immunoglobulins (IVIg) are immunomodulatory, they have been investigated in a large number of putative autoimmune diseases. This has led to licensing for idiopathic thrombocytopenic purpura, Kawasaki disease, and in neurological disorders for Guillain-Barré syndrome (GBS). Although not licensed, randomized controlled trials have also shown IVIg efficacy in other neuroimmunological diseases such as multifocal motor neuropathy (MMN), chronic inflammatory demyelinating neuropathy (CIDP), myasthenia gravis, dermatomyositis, and stiff-person syndrome. However, other indications are currently being explored including Alzheimer's disease, postpolio syndrome, and narcolepsy. There are even reports from experimental studies in stroke. The results of recently published clinical trials in both the classical neuroimmunological disorders as well as for new indications are reported and their role in clinical practice is discussed.

Treatment of neurodegenerative CNS disease in Langerhans cell histiocytosis with a combination of intravenous immunoglobulin and chemotherapy

BACKGROUND

In rare cases, patients with Langerhans cell histiocytosis (LCH) develop neurodegenerative CNS disease (ND-CNS-LCH). Management of ND-CNS-LCH has not been established.

METHODS

We treated five pediatric patients with a combination of intravenous immunoglobulin (IVIG) and chemotherapy (steroid +/- vinblastine +/- 6-mercaptopurine +/- methotrexate). Prior to the therapy, three of the five patients had cerebellar ataxia while the remaining two had abnormal MRI findings without apparent neurological deficits. IVIG was given monthly or twice monthly at the dosage of 250-400 mg/kg/dose.

RESULTS

The four patients administered more than 23 doses of IVIG and chemotherapy remained in a stable condition and did not show significant progression signs in neurological deficits or brain MRI findings during the 30-month follow-up period (median; range: 19+ to 38+) following the initiation of therapy for ND-CNS-LCH.

CONCLUSION

The IVIG-containing treatment may be promising for ND-CNS-LCH; however, its effectiveness remains to be further tested in more patients as well as in a randomized trial.

Myasthenic crisis: guidelines for prevention and treatment

Management of myasthenic crisis (MC) requires admission of the patient into a neurological intensive care unit and timely institution of an efficient and safe treatment. Despite the growing clinical experience with disease modifying immunotherapy there is no clinical consensus regarding the use of plasma exchange or high dose immunoglobulin treatment in an ICU setting. The choice of treatment modalities seem to rely mostly on institutional preferences primarily due to a lack of well-designed clinical trials comparing currently available therapeutic options. In our experience and based on a review of recent literature we advocate the use of plasma exchange (PE) as a primary modality in the acute care setting, supported by other immunomodulatory medications such as corticosteroids. Pharmacological management cannot substitute for adequate intensive care management of the respiratory and bulbar insufficiency associated with MC. Every effort should be done to prevent myasthenic exacerbation/crisis and to develop a maintenance management that leads to effective prevention.

IVIg attenuates T cell-mediated killing of human neurons

Beneficial effects of intravenous immunoglobulin (IVIg) in relapsing-remitting multiple sclerosis (MS) have been described, including a decrease of brain atrophy. We have previously shown that activated T cells kill neurons in culture. In this manuscript, we show that the pretreatment of activated T cells with IVIg attenuates T cell neurotoxicity. This is attributed to the ability of IVIg to decrease the adhesion of T cells onto neurons, possibly through an effect on LFA-1, and by lowering the levels of Fas and FasL on T cells. Our results are relevant to understanding how therapies affect the MS disease process.