A microassay for measurement of Fc function of human immunoglobulin preparations by using tetanus toxoid as antigen

In order to minimize possible adverse reactions, the functional integrity of proteins in products derived from human plasma has to be unaffected by methods of preparation and storage conditions. Numerous biologically relevant functions of IgG, a major component of immunoglobulin for intravenous use preparations (IVIG), rely on the integrity of Fc fragments. Manufacturers are obliged to prove that Fc-mediated functions are maintained in IVIG preparations. The European Pharmacopoeia's monograph proposes a Rubella antigen-based test for Fc function of immunoglobulins. We present a modification of the proposed method achieved by using more convenient and readily available tetanus toxoid as an alternative antigen target and by adapting the procedure for the use on microtitre plates, thus greatly enhancing its feasibility and sample throughput. The test conditions were optimized so that batch-to-batch variability in tetanus antibody content did not influence the result. The precision of the test was within +/- 5%. By using this test, we compared Fc functionality of 9 commercial IVIG-7S preparations, which were prepared by using different virus inactivation/removal approaches. No significant differences between them have been found.

Toward Molecular Targeting With Specific Intravenous Immunoglobulin Preparation

Intravenous immunoglobulin (IVIg) is used successfully for therapy of inflammatory and autoimmune diseases, especially in cases of conventional therapy resistance. Within the broad spectrum of immunoregulatory activities of IVIg in vitro and in vivo, the anti-idiotypic activity neutralizing the related idiotypes is one of the main mechanisms. Furthermore, IVIg addresses integrins associated with inflammation and immune response thrombosis, such as the RGD (Arg-Gly-Asp) motif, expressed on a large number of cell surface and matrix proteins. In addition, during the last years, anti-Fas activity of IVIg was reported. We fractionated IVIg specific preparation (sIVIg) based on the multispecificities of the IVIg compound. We have generated an IVIg fraction that will show specific activity for lupus idiotypes in vitro. In NZBxW.F1 mice, results showed 200 times more beneficial effect. Using a peptide phage display library technology, we have identified a panel of lupus-related synthetic idiotypes that are mimetics of the idiotypes presented in patients with systemic lupus erythematosus. A column composed of these synthetic lupus-related idiotypes was used to prepare a large amount lupus-specific IVIg. Using the same approach, we prepared anti-anti-beta-2-glycoprotein-I (beta2GPI) specific IVIg for antiphospholipid syndrome (APS). This APS-specific IVIg reduced the fetal loss induced by anti-beta2GPI antibodies by improving the implantation process in a mouse model. Others prepared specific preparations of IVIg to RGD or for Fas. The molecular targeting with specific IVIg may be used for therapeutical purposes, using a smaller amount of IVIg, and targeting more specifically autoimmune diseases, thrombosis, or inflammatory condition.

Immunologic manipulation for the threatened fetus

Management of the pregnant woman with the antiphospholipid syndrome (APLS) has improved over the last 10 years. The recurrent pregnancy loss that is associated with this disease is managed with prophylactic low dose aspirin and heparin therapy. This therapy leads to a 40% absolute risk reduction in pregnancy loss. However, many women still fail to deliver a live infant despite this therapy so immunologic manipulation of the mother's disease in this group needs to be considered. Intravenous immunoglobulin and plasma exchange may have a role. New immunosuppressive drugs such as tacrolimus have yet to be tried. Monoclonal antibodies to B cells, B-cell growth factors, complement proteins and integrin molecules, all of which appear to play a role in the disease process, may also offer patients some hope. Similarly, biologics such as C1 esterase inhibitor protein, cell surface complement regulator proteins or interleukin-3 need to be tried given their efficacy in models of antibody-induced cell injury.

Acute humoral rejection of human lung allografts and elevation of C4d in bronchoalveolar lavage fluid

Antibody-mediated rejection is well established for renal allografts but remains controversial for lung allografts. Cardinal features of antibody-mediated rejection in renal allografts include antibodies to donor human leukocyte antigen (HLA) and evidence for antibody action, such as complement activation demonstrated by C4d deposition. We report a lung allograft recipient with circulating antibodies to donor HLA who failed treatment for acute cellular rejection but responded to therapy for humoral rejection. To address the second criteria for antibody-mediated rejection, we determined whether complement activation could be detected by measuring C4d in bronchoalveolar lavage fluid (BALF) by ELISA. Airway allergen challenge of asthmatics activates the complement pathway; therefore, we used BALF from asthmatics pre- and post-allergen challenge to measure C4d. These controls demonstrated that ELISA could detect increases in C4d after allergen challenge. BALF from the index patient had elevated C4d concomitant with graft dysfunction and anti-donor HLA in the absence of infection. Analysis of BALF from 25 additional lung allograft recipients showed that C4d concentrations >100 ng/mL were correlated with anti-HLA antibodies (p = 0.006), but were also observed with infection and in asyptomatic patients. The findings support the occurrence of anti-HLA-mediated lung allograft rejection and suggest that C4d measurement in BALF may be useful in diagnosis.

In vitro glycation of human immunoglobulin G

BACKGROUND

Glucose can covalently bind to the proteins by nonenzymatic process often termed glycation. Glycation of IgG is of special interest due to its possible influence on the functionality of immunoglobulins and overall immunocompetence.

METHODS

The glycation of IgG was studied using radioactive D-[U-14C]-glucose.

RESULTS

The kinetics, concentration/temperature dependence and distribution of glycation binding sites of human IgG were studied under various conditions. (a) In average, 0.7 glucose molecules were found to be bound per IgG after 90 days of incubation at 37 degrees C with normal serum IgG and glucose concentrations, and 3.1 molecules after incubation with glucose in the concentration characteristic for diabetics. (b) Incubation of the same solutions for 270 days at 4-8 degrees C resulted in binding of 0.3 and 0.8 glucose molecules per IgG, respectively. (c) After 90 days at 37 degrees C in the presence of 0.56 mol/l of glucose, IgG was glycated with averagely 47 glucose molecules per IgG and with 9 after 270 days at 4-8 degrees C. (d) At very high glucose concentration (1.67 mol/l) in concentrated IgG solution (87 g/l), the molar ratio glucose/IgG reached 41 after incubation at 60 degrees C for 10 h.

CONCLUSIONS

Glycation of IgG with glucose nearly resembled the first order reaction kinetics. No preferential glycation sites were found as bound glucose was equally distributed throughout F(ab)2 and Fc fragments as well as on the light and heavy immunoglobulin chains.

[Feasibility of administering Tegeline at home. Retrospective study of efficacy, safety and tolerance]

OBJECTIVE

To demonstrate the feasibility of administration Tegeline at home from a point of view of efficacy, safety, tolerance, to validate the pertinence of the selection and the training of patients who could benefit from this type of administration and to assess the long term efficacy and safety.

METHOD

This retrospective study was conducted in patients exhibiting primary immune deficiency and formerly treated with intravenous immunoglobulins at least six months in hospital settings, trained by the centre for the training of children in the home (Centre de formation au traitement à domicile de l'enfant--CFTDE) and having received at least one administration of Tegeline at home from January 1st 2000. Tegeline contains a mean of 97.6% of whole IgG (58.8% of IgG1, 34.1% of IgG2, 5.4% of IgG3 and 1.7% of IgG4).

RESULTS

Two hundred and eighteen follow-up sheets were completed by 13 patients in whom all the eligibility criteria were fulfilled. The total number of infusions per patient ranged from 4 to 41. No difficulty in administration was reported in 10 patients, difficulties in placing the needle were encountered in 3 other patients and motivating their return to the hospital for treatment (after 6 and 10 months) in 2 cases. The infusion flow rate was usually of 2 to 3 ml/kg/h. During the follow-up period, no episode of infection was noted in 5 patients and 8 presented infections that were treated with antibiotics. Regarding safety, the security 'kits' (corticosteroids, adrenalin) that were supplied to each patient were never used. Over time, the median duration of the infusions at home was of 5 years and 6 months.

CONCLUSION

In trained and selected patients, this study demonstrated the efficacy, safety and tolerance to the administration of Tegeline at home.

An immunoglobulin agent (IVIG) inhibits NF-kappaB activation in cultured endothelial cells of coronary arteries in vitro

OBJECTIVE

Kawasaki disease (KD) is an acute febrile vasculitis of unknown etiology that may lead to cardiovascular disorders. High-dose intravenous immunoglobulin (IVIG) therapy is well established as a standard therapy for KD. Tumor necrosis factor-alpha (TNF-alpha) is responsible for the pathogenesis of acute KD. We examined whether or not IVIG inhibits TNF-alpha-induced activation of transcription factor NF-kappaB, a factor that is essential for the expression of proinflammatory cytokines, in human coronary artery endothelial cells (CAEC).

METHODS

The inhibitory effect of IVIG on NF-kappaB activation induced by TNF-alpha was evaluated by Western blot analysis and ELISA. Moreover, the inhibitory effects of IVIG on IkappaBalpha degradation, interleukin-6 (IL-6) production, and E-selectin expression induced by TNF-alpha were evaluated by Western blot analysis, ELISA, and flow cytometry, respectively.

RESULTS

Western blot analysis and ELISA demonstrated that IVIG inhibits NF-kappaB activation induced by TNF-alpha in CAEC. Moreover, IVIG inhibited IkappaBalpha degradation, IL-6 production, and E-selectin expression induced by TNF-alpha in CAEC.

CONCLUSION

The data suggest that IVIG inhibits NF-kappaB activation induced by TNF-alpha in CAEC, thereby possibly modulating IL-6 production and E-selectin expression.

The appearance and disappearance of antiphospholipid autoantibodies subsequent to oxidation–reduction reactions

The mechanisms that cause the appearance of autoantibodies are not understood. Compared to normal antibody production, factors responsible for autoantibody synthesis are more complex; they are thought to disrupt the normal mechanisms proposed to eliminate or down-regulate self-antibodies or to interfere with anti-self-receptor editing. Data presented show that autoantibodies exist in the blood of all normal individuals. The autoantibodies appear after simple oxidation-reduction (redox) reactions and react by ELISA, immunofluorescence, flow cytometry, Western blots, and in lupus anticoagulant (LA) assays. Antiphospholipid antibody (aPL) specificities detected after redox are cardiolipin (aCL), antiphosphatidylserine (aPS), antiphosphatidylethanolamine (aPE), antiphosphatidylcholine (aPC), and LA. These antibody activities were confirmed in several outside laboratories. The aPL isotypes detected in ELISA are plasma protein-dependent and include IgG, IgA, and IgM. Oxidizing agents tested to date include hemin, KMnO4, and NaIO4. Furthermore, aPL appear after exposure to direct current (DC)-mediated electromotive force. Alternating current (AC) is ineffective. Commercial IvIg preparations, also a source of IgG autoantibodies, provide a less complex milieu than plasma or serum for studying the biology of aPL redox-mediated mechanisms. Inhibition of hemin-mediated IvIg aPL conversion can be achieved by the addition of antioxidants, e.g., ascorbic acid, hemopexin, apotransferrin, and by addition of normal plasma or serum. Remarkably, the aPL specificities in the blood of autoimmunity patients disappear subsequent to application of redox reactions. These data document the hitherto unknown existence of redox-reactive autoantibodies in all normal individuals. The evolutionary persistence of these redox-sensitive antibodies raises interesting possibilities about their potentially beneficial role in immunological homeostasis.

Gamma irradiation of intravenous immunoglobulin

This paper describes gamma irradiation of a biotherapeutic product under conditions (the Clearant Process") that protect proteins and foster inactivation of viruses and other pathogens. The treated product was immunoglobulin paste from cold ethanol fractionation of human plasma, a process intermediate in the production of intravenous immunoglobulin (IGIV). The frozen paste was irradiated on dry ice to 45 kGy, conditions that inactivate > or = 4 log10 of non-enveloped viruses and > or = 6 log10 of enveloped viruses. When IGIV purified from the irradiated paste was characterized, no protein aggregation, fragmentation, oxidation or denaturation was detected and Fab functionality remained intact.

Hypotension with intravenous immunoglobulin therapy: importance of pH and dimer formation

Therapy with intravenous immunoglobulin preparations has been used effectively in a wide range of conditions. Although generally well tolerated, intravenous immunoglobulin preparations may be associated with transient hypotension in some patients. This study examined the role of different immunoglobulin G fractions in the development of intravenous immunoglobulin-induced hypotension in an anaesthetized rat model and assessed the effects of a new liquid immunoglobulin prepared at a low pH on both the formation of immunoglobulin G dimers and the development of hypotension. The effects of this new preparation in an experimental autoimmune encephalomyelitis model were also evaluated. Results from the haemodynamic studies indicated that immunoglobulin G dimers in polyclonal immunoglobulin G are responsible for the hypotensive events associated with some immunoglobulin preparations. They also showed that adjustment to an acidic pH results in the rapid dissociation of immunoglobulin G dimers and prevents the development of hypotension. Additional experiments demonstrated that only immunoglobulin G dimers with a functional Fc fragment can bind to Fcgamma receptors on macrophages to induce the release of blood pressure-lowering mediators. Moreover, essentially monomeric Fc fragments can block the blood pressure-lowering effects of immunoglobulin G dimers. Preparation of a new liquid intravenous immunoglobulin with the pH adjusted to 4.3 prevents the formation of immunoglobulin G dimers even over long-term storage and does not significantly affect blood pressure in a rat model. This preparation is as effective as other intravenous immunoglobulin preparations in ameliorating symptoms of experimental autoimmune encephalomyelitis. These results, like those from previous studies, indicate that preparation of intravenous immunoglobulin at a low pH substantially reduces immunoglobulin G dimerization; this effect significantly decreases the potential for intravenous immunoglobulin to induce hypotension without reducing its clinically relevant biological activity.

Polyreactive autoantibodies purified from human intravenous immunoglobulins prevent the development of experimental autoimmune diseases

Intravenous immunoglobulins (IVIg) are therapeutic preparations of normal human polyclonal Ig G (IgG) that exert immunomodulatory effects in patients with autoimmune or systemic inflammatory diseases. Two different IgG subfractions were evaluated for their respective immunomodulatory effects in the treatment of experimental autoimmune diseases: a fraction enriched in antibodies that recognize the F(ab')(2) portion of IVIg and a fraction of natural polyreactive autoantibodies purified on a dinitrophenyl (DNP)-Affiprep immunoadsorbent. A very small fraction of IgG interacting with DNP but not with F(ab')(2) fragments expressed an increased ability to bind to self-antigens. The anti-DNP fraction, but not the anti-idiotype fraction, protected against inflammation observed in collagen-induced arthritis and experimental autoimmune encephalomyelitis in rats. Furthermore, it was able to reduce the occurrence of spontaneous diabetes mellitus in nonobese diabetic mice at lower concentrations than unfractionated IVIg. The therapeutic benefit of the anti-DNP fraction was associated with the inhibition of secretion of proinflammatory cytokines and stimulation of secretion of IL-1 receptor antagonist. Our results provide evidence that polyreactive autoantibodies play a role in the protective effect of IVIg in experimental models of autoimmune diseases in which inflammatory reactions are part of the disease process.

Cytokine levels in various intravenous immunoglobulin (IVIg) preparations

The mechanisms of action of intravenous immunoglobulin (IVIg) in autoimmune diseases include modulation of cytokine levels. We examined therefore whether direct infusion of abnormally high levels of 13 different cytokines or cytokine-inhibitors within 5 different IVIg preparations have any role in modulation of their levels. None of the measured cytokines in any of the IVIg preparations tested were above the normal levels, and regarding some no traces could be detected. Hence, modulation of cytokine levels following IVIg therapy involves other mechanisms such as interference with their secretion or cytokine-specific blocking antibodies, rather than direct infusion of cytokines.

[Determination of IgG content of IVIG by improved rocket immune electrophoresis]

OBJECTIVE

To establish a specific method for determination of IgG in IVIG.

METHODS

The IVIG samples were disposed by acylation and analyzed by Rocket Immunoelectrophoresis. The amount of the IgG in IVIG was calculated by an IgG standard curve.

RESULTS

The standard curve by this method has a very good linear relationship: r = 0.9967. The reproducibilities with 3 bathes of IVIG samples (n = 6) are 5.37% +/- 0.21%, 5.28% +/- 0.39% and 5.80% +/- 0.30%.

CONCLUSION

This method could be adapted to regular assay in blood products.

Temporal profile of anti-ganglioside antibodies and their relation to clinical parameters and treatment in Guillain-Barré syndrome

Elevated anti-ganglioside antibody levels mainly of anti-GM1 and anti-GD1a specificities have been reported in THE serum of patients with Guillain-Barré syndrome (GBS). The relevance of anti-ganglioside antibodies other than anti-GM1 and anti-GD1a IgG antibodies and the temporal profile of anti-ganglioside antibodies in GBS is less clear. We studied serum antibodies to GM1, GD1a, GD1b, GQ1b, sulfatide and cardiolipin of the IgM, IgG and IgA classes over the course of GBS in patients who were untreated or treated with high dose intravenous immunoglobulin (IvIg). Antibodies to GD1b, GQ1b, sulfatide and cardiolipin were not detected in the sera of the GBS patients examined in this study. Anti-GM1 IgG titers peaked around 40 days and anti-GD1a IgM around 90 days after GBS onset. Titers of anti-GM1 IgG antibodies decreased following IvIg treatment. Patients with antibody peaks, defined as fivefold or higher increase in antibody titer compared to the lowest antibody titer over the course of GBS, had higher disability scores during the first two weeks of GBS and a worse clinical outcome (anti-GM1 IgG and anti-GD1a IgM antibody peaks) and axonal damage (anti-GD1a IgM antibody peaks), compared to patients without peak antibody titers. Anti-GM1 IgG and anti-GD1a IgM antibodies are thus strongly associated with more severe- and predominantly axonal cases of GBS. The appearance of anti-GM1 IgG and anti-GD1a antibody peaks in the serum after the termination of the acute phase of GBS suggests that these antibodies are produced secondary to nerve damage in GBS. The data does not exclude the possibility that secondarily secreted anti-GM1 IgG and anti-GD1a IgM antibodies may themselves be biologically active and play a role in disease propagation and/or recovery from disease in some patients with GBS.

Enhanced efficacy of anti-D immunoglobulin for treating ITP is not explained by higher immunoglobulin polymer content

Several reports have suggested that low dose anti-D immunoglobulin is superior to high dose immunoglobulin for treatment of idiopathic thrombocytopenia purpura (ITP). However, some findings suggest that it is not the anti-D activity per se that is responsible for efficacy for treatment of ITP with anti-D immunoglobulin. Amongst alternative explanations for the mechanism of action is a relatively higher immunoglobulin polymer content of anti-D compared to other immunoglobulin products, which is more efficient in causing reticuloendothelial Fc receptor blockade. In order to investigate this we have evaluated the polymeric IgG content of anti-D and other immunoglobulin products. Different products showed considerable variation in immunoglobulin polymer content. There was no clear correlation between aggregate or dimer content and product type and anti-D as a class of product did not contain higher amounts of either dimer or aggregate compared to other products. Some manufacturers' products increased in polymer content on storage, but others did not show this effect. Therefore, higher immunoglobulin dimer and/or aggregate content cannot explain the increased efficacy of anti-D immunoglobulin for treatment of ITP. The role of polymeric Ig in efficacy for treatment of ITP is unclear.

Solid-phase immunoassays for HCV antibodies in Gamimune N

BACKGROUND AND OBJECTIVES

Occasional false-positive results for the presence of HCV antibodies occur when testing pH 4 Gamimune N immune globulin intravenous (human) (IGIV) using commercially available immunoassay kits. We investigated the causes.

MATERIALS AND METHODS

EIA test results were compared with Nile red hydrophobic dye binding.

RESULTS

There was a strict correlation of reactive EIA results with a larger relative proportion of molecules in a low pH-dependent hydrophobic conformation. Conversely, the greater the hydrophilic contribution to the population of IgG molecules (favored at neutral pH), the more nonreactive the EIA test results became for the same lots. An IGIV test preparation procedure consisting of pH neutralization followed by 48-hour incubation at 37 degrees C decreased positive test result outcomes in four different immunoassay formats by shifting the IgG population to a more hydrophilic conformation.

CONCLUSIONS

The hydrophobic conformation of IgG favored at low pH appears to give rise to significant levels of nonspecific binding in solid phase immunoassays.

Coagulation factor XI is a contaminant in intravenous immunoglobulin preparations

A small number of thromboembolic events, including deep venous thrombosis and myocardial infarction, have been reported in patients receiving IVIG. These events have primarily occurred in patients receiving high-dose IVIG and have been attributed to an increase in blood viscosity. To test the hypothesis that a procoagulant might be present in IgG preparations, twenty-nine samples of intravenous immunoglobulin (IVIG) from eight different manufacturers were assayed for procoagulant activity. Twenty-six of these samples shortened the clotting time of factor XI-deficient plasma. Of these, fourteen samples had factor XI activities greater than 0.001 U/ml of normal pooled plasma. The remaining samples possessed less than 0. 001 U/ml of normal plasma activity. The procoagulant activity in these samples could be inhibited by an anti-factor XI polyclonal antibody, suggesting that the procoagulant activity was factor XI. The procoagulant activity increased in two samples after storage at 4 degrees C for 4 weeks, likely as a result of factor XIa autoactivation. Additionally, activity in some IVIG samples was able to directly activate factor IX, indicating that activated factor XI was present in these samples. Finally, the degree of factor XI(a) contamination in the samples was correlated with the manufacturer, suggesting that variations in the manufacturing process or source plasma affect the level of factor XI in the IVIG product. Because addition of small amounts of factor XIa to plasma can lead to production of significant amounts of thrombin, we suggest that factor XIa present in some IVIG preparations could contribute to the in vivo risk of thrombosis after IVIG therapy.

Human intravenous immunoglobulin preparation and virus inactivation by pasteurization and solvent detergent treatment

Human intravenous immunoglobulin (IVIG) solutions were prepared by two different methods and compared to each other. The crude immunoglobulin fraction obtained from Cohn-Oncley fractionation of plasma was further purified and subjected to virus inactivation, either by polyethylene glycol precipitation and pasteurization at 60 degrees C for 10 hours, or by ion exchange chromatography and solvent/detergent treatment. The final preparations, formulated in 5% immunoglobulin solutions were characterized by in vitro analyses of biochemical and biological properties and compared with the samples of other manufacturer's IVIG solution products. The critical properties evaluated in this study were purity, molecular intactness, and the biological functions such as Fc function and anticomplementary activity. Virus inactivation and removal by processing steps and by deliberate virucidal steps, as described above, were tested on various human pathogenic viruses, such as human immunodeficiency and experimental model viruses. The tested viruses were successfully inactivated and removed. We conclude that the intravenous immunoglobulins prepared by two different methods, as described above, provide an equivalent viral safety and quality.

Monitoring of two intravenous immunoglobulin. Preparations for immunoglobulin G subclasses and specific antibodies to bacterial surface antigens and relation with their levels in treated immunodeficient patients

Patients with antibody deficiency disorders are highly susceptible to bacterial infections. Replacement therapy with intravenous immunoglobulin preparations (IVIG) has been established in such patients for two decades. The efficacy of IVIG treatment depends on the amount of functional pathogen-specific antibodies provided. The present study was undertaken to determine the levels of immunoglobulin classes, IgG subclasses, and specific antibodies to bacterial surface antigens in two different IVIG preparations (Sandoglobulin and Gamimmune) and blood sera of IVIG-treated immunodeficient patients. The levels of IgG, IgA, IgM and IgG subclasses were determined in both IVIG preparations and in patients' sera and were compared with those of healthy individuals. Sandoglobulin contained significantly higher concentrations of IgA, IgG, and IgG4 than Gamimmune. The latter contained higher concentrations of IgG1. Patients treated with Gamimmune) had significantly lower concentration of IgG4 as compared with healthy individuals and Sandoglobulin-treated patients. This finding was related to the preparation's composition. Screening of 20 lots from each preparation for antibodies to frequent clinically isolated strains of Escherichia coli, Staphylococcus aureus, S. epidermidis. Klebsiella pneumoniae and Enterococci spp. showed a high lot-to-lot variability. In order to overcome the lot-to-lot variability and correlate the observed effects with each IVIG preparation, the administered IVIG lots were selected so that their titers were in the interval of mean value +/- S.D. for each pathogen. The two tested preparations showed significant differences in their content of specific antibodies that ultimately affected the levels of these antibodies in treated patients. More specifically, Sandoglobulin contained higher levels of antibodies to E. coli and S. epidermidis strains. Infusion of this preparation maintained the respective antibodies in the recipients significantly higher than those of healthy individuals. Gamimmune infusion led to similar and comparable levels. Both IVIG preparations had comparable antibody titers towards K. pneumoniae, provided high amounts of antibodies, and kept recipients' specific IgG at levels significantly higher than those of the healthy individuals. Enterococci spp. specific antibodies were significantly higher in Gamimmune, whereas titers of antibodies towards S. aureus were comparable. Levels of antibodies against both Enterococci spp. and S. epidermidis after administration of both preparations were close to those in healthy individuals. None of the patients developed infection during the time of the study. In conclusion, most of the lots of the two IVIG preparations studied, despite some quantitative differences, provide patients with sufficient amounts of antibodies to bacterial surface antigens that protect them against infections.

Prevalence of hepatitis G virus in healthy children in liver disease, and human immunodeficiency virus-1 infection: response to interferon

BACKGROUND

A new virus of the Flaviviridae family, the hepatitis G virus (HGV/HGBV-C), has been identified recently. The purpose of this study was to determine the prevalence of HGV infection in healthy children, in patients with liver disease, and in human immunodeficiency virus (HIV)-1-infected patients. The role of HGV in the clinical course of chronic HCV, the response to interferon-alpha2b, and the possible implications of intravenous gamma-globulin in the transmission of the virus were also evaluated.

METHODS

Fifty healthy children, 66 patients with a variety of liver diseases, 19 patients with acquired immune deficiency syndrome (AIDS), and various batches of commercial intravenous immunoglobulins were investigated. Viral HGV RNA (5'NCR-NS5) and anti-HGV envelope protein E2 were assayed.

RESULTS

The prevalence of HGV infection was 6% in the healthy children and 42% in the liver disease group. Viremia and anti-E2 were found in 11% and 79% of patients with AIDS. Four (27%) of 15 patients with chronic HCV, receiving treatment with interferon, were coinfected by HGV and became HGV-RNA negative during therapy. One year after the end of interferon therapy, three of them were again HGV RNA positive.

CONCLUSIONS

The prevalence of HGV infection is high in healthy children higher in children affected with liver disease, but its potential pathologic implication is questionable, and further studies are warranted. Hepatitis G virus is sensitive to interferon therapy, although the infection often recurs after discontinuation of treatment.

Monocyte-macrophage system as targets for immunomodulation by intravenous immunoglobulin

Pooled human intravenous immunoglobulin (IVIg) has been used successfully to treat or ameliorate the clinical manifestations of humoral immune deficiencies, haematological disorders, HIV infection and many other diseases states. However, the mechanism of action of IVIg remains unclear. Several mechanisms of action of IVIg have been proposed. These include Fcy receptor blockade, accelerated clearance of endogenous pathogenic auto-antibodies, inhibition of components of the complement cascade, neutralization of super-antigens and bacterial toxins as well as anti-cytokine and anti-idiotype effects. A major contributor to host immunity and immune surveillance against infection, tissue or cell damage and malignancy is the monocyte/macrophage system. Monocyte-directed inflammation is a desirable consequence of microbiological or malignant challenge. However, monocyte hyperactivity may contribute to certain pathological conditions. These include the systemic inflammatory response syndrome (SIRS), septic shock, other dysregulated inflammatory disorders and auto-immunity. Novel therapies that can suppress the hyperactive state or correct monocyte/macrophage dysfunction without compromising normal host cell-mediated immunity are desirable. In this review, we discuss the immunomodulatory effects of IVIg focussing particularly upon the monocyte/macrophage system in pertinent disease states.

Epitope-specific glutamic acid decarboxylase-65 autoantibodies in intravenous immunoglobulin preparations

Intravenous immunoglobulin (IVIG) has been used to treat many autoimmune disorders including Stiff-Man Syndrome (SMS). SMS is a neurological disorder associated with an immune-mediated deficiency of gamma-aminobutyric acid (GABA) due to autoantibodies against the GABA synthesizing enzyme glutamic acid decarboxylase-65 (GAD65). GAD65 autoantibodies are present among 1-2% of healthy individuals. It can therefore not be excluded that GAD65 autoantibodies may be present in IVIG, which is prepared from multiple blood donors. We report here that GAD65 but not IA-2 autoantibodies were present in commercial IVIG preparations. The presence of autoantibodies may affect the outcome of IVIG treatment and screening commercial preparations of IVIG for GAD65 autoantibodies is therefore recommended before treating patients.

In vivo administration of intravenous immunoglobulin (IVIg) can lead to enhanced erythrocyte sequestration

Enhanced erythrocyte sequestration is one of the very few major adverse effects of intravenous immunoglobulin (IVIg). IVIg contains high molecular weight IgG complexes ( approximately 300 kDa) which, in the presence of serum, mimic immune complexes by activating complement, binding to CR1 of red blood cells (RBC) (CD35) and mediating erythrophagocytosis. Four of seven patients undergoing IVIg therapy showed significant drops in haematocrit and haemoglobin that were not due to isoantibodies in the IVIg. Prior to treatment, patients' RBC carried IgG and complement (C') 3d that were not bound as immune complexes via CR1 (CD35). The patients whose RBC bound immune complex-like moieties and showed drops in haematocrit and haemoglobin subsequent to IVIg were young adults (22-35 years); older patients (50-69 years) showed no ill effects. In the presence of complement, RBC of young patients bound IVIg complexes in vitro while those of older patients did not. It is not the absolute levels of erythrocyte-associated IgG or C'3 fragments, neither pre- nor post-therapy, which are predictive of IVIg associated decreases in haematocrit and haemoglobin levels. Patient age and RBC inability to bind the IVIg immune complex-like moieties in vitro both appear to be predictors of resistance to sequestration after in vivo treatment with IVIg.

Administration of intravenous immunoglobulin (IVIG) in vivo--down-regulatory effects on the IL-1 system

Modulation of the cytokine network may be of importance for the beneficial effects of therapy with IVIG seen in a wide range of immune-mediated disorders. In the present study we investigate the effect of IVIG administration in vivo on the IL-1 system in 12 patients with primary hypogammaglobulinaemia. Before IVIG infusion these patients had significantly elevated levels of IL-1alpha and IL-1beta both in plasma and in supernatants from peripheral blood mononuclear cells (PBMC) compared with healthy controls. After one bolus infusion with IVIG (0.4 g/kg) we found a significant change in the profile of the components of the IL-1 system: a marked increase in levels of IL-1 receptor antagonist (IL-1Ra) and neutralizing antibodies against IL-1alpha, a moderate decrease in levels of IL-1alpha, IL-1beta and soluble (s) IL-1 receptor type I and a significant increase in sIL-1 receptor type II levels. These changes were found both in plasma and in PBMC isolated after IVIG administration. Furthermore, pooled serum obtained after IVIG infusion suppressed lipopolysaccharide- and staphylococcal enterotoxin B-stimulated, but not phorbol myristate acetate-stimulated, release of IL-1alpha and IL-1beta from PBMC isolated from healthy controls. Finally, these changes in circulating levels of various IL-1 modulators after IVIG infusion appeared to cause a significantly impaired ability of IL-1 to stimulate PBMC for tumour necrosis factor-alpha release. Our findings suggest that IVIG administration may not only down-regulate the activity in the IL-1 system, but also hamper IL-1 stimulation of PBMC.