Increased In Vivo Antibody Activity Against Interferon α, Interleukin-1α, and Interleukin-6 After High-Dose Ig Therapy

INTRAVENOUS ADMINISTRATION of pooled human IgG has been used as a substitution therapy in hypogammaglobulinemia or agammaglobulinemia and in infectious diseases and as an immunomodulatory therapy in disorders such as autoimmune thrombocytopenic purpura, myasthenia gravis, the Guillain-Barré syndrome and other types of polyneuropathies, dermatomyositis, and Kawasaki disease.1-3 Blockade of Fc-receptor function on phagocytes, complement absorption, changes in the distribution and function of T-cell subsets, and antigen-specific immunomodulation through antibodies to microbial components or anti-idiotypic antibodies have been proposed to underlie the effects of IgG therapy.1-4 

Pharmaceutically prepared IgG preparations modulate cytokines in vitro and in vivo, and cytokine modulation has been proposed as a possible contributor to the clinical efficacy of IgG therapy, particularly in situations where anti-inflammatory and immunomodulatory effects appear to be a central mechanism of action.5-8 

We have previously demonstrated specific, high-avidity and in vitro neutralizing antibodies to interferon α (IFNα), interleukin-1α (IL-1α), and IL-6 in pharmaceutically prepared IgG.8-11 In the present study, we investigated the levels of these naturally occurring anticytokine antibodies in sera from patients with autoimmune diseases before and after IgG infusion. We also tested the effects of the administered anticytokine antibodies on endogenous blood cytokines and antiviral activity in these sera.

Patients and study design.Eight patients were included in the study (1 man and seven women; median age, 40 years; range, 26 to 47 years). Six patients suffered from systemic lupus erythematosus (SLE), one had polymyositis, and one had mixed connective tissue disease (MCTD), based on the American Rheumatism Association's criteria.12 All patients had previously been treated with IgG (>4 weeks before the study). Four patients received hydroxychloroquin, one received prednisolone, and one received azathioprin. None of the patients had signs of infection before treatment with IgG. All patients had active disease at the time of entering the study.

The IgG preparations were Gammagard (Baxter, Allerød, Denmark) and Sandoglobulin (Sandoz, Basel, Switzerland). All patients received 0.4 g IgG/kg/d over 3 consecutive days, and blood sampling was performed before therapy and 1 hour after the last infusion. This regimen was administered three times to three patients, two times to one patient, and once to four patients. The study was approved by the local ethics committee.

Cytokines and antibody.Human recombinant IFNα2A (Roceron) and monoclonal antibody against IFNα2A were kindly donated by Hoffmann La-Roche (Basel, Switzerland), and leukocyte IFN-α (le-IFNα; Alfanative) by Bionative (Uppsala, Sweden). Human recombinant IL-1–α and IL-6 were generous gifts from Dainippon Pharmaceutical Co (Osaka, Japan), and Sandoz (Basel, Switzerland), respectively. IL-1α and IL-6 were calibrated with the corresponding international reference preparations (National Institute of Biological Standards and Control, Potters Bar, Hertfordshire, UK). IFNα2A was titrated against the international standard GxA01-901-535 (National Institutes of Health [NIH], Bethesda, MD).

Radiolabeling of cytokines and binding assay.The cytokines were radiolabeled by the chloramine T method and handled further as described previously.9,10 After iodination, the radiolabeled cytokines were chromatographed on Sephadex G-75 superfine microcolumns to remove aggregates and salt fractions. ¹²⁵I–IL-1α and ¹²⁵I–IL-6 had preserved receptor binding capacity and bioactivities,13 14 and the antiviral activity of ¹²⁵I-IFNα2A was confirmed using the antiviral bioassay (AVB) described below.

Binding of ¹²⁵I-labeled cytokines was detected using protein-G affinity chromatography at twofold dilutions of the samples.9 10 Sera, at a maximum concentration of 80% (vol/vol), were incubated with 100 pg ¹²⁵I-IFNα2A/mL, 400 pg ¹²⁵I–IL-1α/mL or 200 pg ¹²⁵I–IL-6/mL, with and without 1,000 times surplus of the respective unlabelled cytokine. After 18 hours at 4°C, duplicate samples of 100 mL were added to protein-G for separation of IgG-bound (B) and free (F ) cytokine molecules. Binding of ¹²⁵I-labeled cytokine to IgG preparations was assayed up to concentrations of 20 mg/mL IgG.

Antiviral bioassay.AVB was performed using encephalomyocarditis (EMC) virus, donated by Dr A.R. Thomsen (Institute of Microbiology and Immunology, University of Copenhagen, Denmark), and a sensitive subclone, SC-3, made by limiting dilution from A549 cells (CCL 185; American Type Culture Collection, Bethesda, MD), as described.10 Briefly, cells were seeded in microtrays at a concentration of 10,000 cells/well and incubated at 37°C in a 5% CO₂ humidified air atmosphere. The endogenous antiviral effect was tested on 20 × diluted sera to avoid toxicity; samples used to test for IFNα-neutralizing activity were added 3 IU IFNα/mL. After 24 hours, EMC virus was added at a concentration, which by itself, caused 100% cell death after 24 hours. After another 24 hours, the antiviral effects of sera or IFNα were measured using a 3-(4,5 dimethyl thiazol-2-yl)-2,5-difenyl tetrazolium bromid assay .15 At 10 mg IgG/mL, none of the IgG preparations showed detectable antiviral activity.

Assay for IgG.The IgG contents of serum and IgG preparations were determined by turbidimetry using rabbit antibody to human IgG, code Q 331 (Dako, Copenhagen, Denmark) and HOO-03 reference serum from Janssen Biochemical (Beerse, Belgium).

Assays for immunoreactive IL-1α and IL-6.Enzyme-linked immunosorbent assay (ELISA) for IL-1α was performed using specific rabbit IgG to human IL-1α, as previously detailed.16 The sensitivity limit was 30 pg/mL. This assay does not detect IL-1α in the presence of natural antibody.9 The serum levels of IL-6 were measured by a high sensitivity IL-6 ELISA (R&D Systems, Abingdon, UK) with a detection limit of 0.1 pg/mL. This ELISA detects free IL-6 and, in addition, IL-6 bound to IgG with an efficiency of 30% to 75%.17 None of the IgG preparations contained detectable IL-1α or IL-6 (measured at 10 mg IgG/mL).

Statistics.The Mann Whitney's U-test, the Wilcoxon's matched pairs test, and the Spearmans rank order correlation test were used. P values < .05 were considered significant.

Anticytokine antibodies in different IgG preparations.Variable binding capacities to IFNα2A, IL-1α, and IL-6 were detected in the different batches of IgG (Fig 1). The Gammagard preparations had the highest binding of IFNα2A followed by IL-1α, whereas the opposite was seen in the Sandoglobulin preparations. The anti-IFNα antibodies were specific in that excess IL-1α, IL-6, or IFNγ failed to interfere with the binding to ¹²⁵I-IFNα2A. The binding to the cytokines was saturable and the anti-IFNα2A antibodies neutralized the antiviral activity of both IFNα2A and le-IFNα in vitro.10 There was a significant positive correlation between the IFNα2A binding capacity and the neutralization of antiviral activity (R = 0.82, P < .00001).

Increased anticytokine binding in sera after IgG administration.As shown in Fig 2, the highest binding capacity in sera collected before IgG therapy was against IL-1α with a median of 25% bound. This increased to 82% after therapy. The corresponding values were 16% to 60% (IFNα2A) and 5% to 27% (IL-6). The incremental bindings afforded by IgG therapy were statistically highly significant in all cases.

Correlations between anticytokine antibodies in IgG and increases in serum binding of the corresponding cytokines.Significant positive correlations were found between the cytokine binding capacities of the infused IgG preparations and the increased serum binding of the three cytokines (Fig 3). When measured directly for IgG, the mean increase in serum after infusion was 12.9 mg/mL ± 2.3 (standard deviation [SD] n = 15).

To compare recoveries of the different anticytokine antibodies, the IgG increments estimated from the binding data (Fig 3) were divided by those measured directly, using the formula:

As shown in Fig 4, the recovery of IFNα2A antibody was significantly reduced, whereas IL-1α and IL-6 antibodies appeared to be more fully recovered.

Suppression of IFNα antiviral activity, but not IL-6 immunoreactivity, after IgG administration.All antiviral activity of the seven positive sera was neutralized ex vivo by specific monoclonal antibody to IFNα2A (data not shown). As shown in Fig 5 (left panel), sera exhibited markedly reduced antiviral activities after IgG infusion compared with matched sera collected before therapy. The infused IgG neutralized pretreatment IFN activity in vitro. The IFNα2A binding of the pretreatment sera did not increase after acid treatment, suggesting that they contained few or no IFNα immune complexes. Because none of the sera collected before and after IgG therapy contained detectable levels of IL-1α, we were unable to measure a possible effect of IgG therapy on circulating IL-1α. IL-6 was demonstrated by ELISA in all sera, but the slight differences between the levels before and after IgG infusions were insignificant (Fig 5, right panel).

Previously, IgG therapy was intended as a supplement given to patients suffering from hypo- or agammaglobulinemia, or to patients thought to benefit from the provision of specific antibodies to infectious agents. It has now become clear that high-dose IgG therapy is an effective treatment of several autoimmune and inflammatory diseases, including some infectious diseases where infusion of specific antimicrobial antibodies is unlikely to play a major therapeutic role.18-21 

Cytokines play a major role in infectious and other immunoinflammatory conditions,22,23 and the recent findings of high-avidity and in vitro neutralizing antibodies to IFNα, IL-1α, and IL-6 in human IgG preparations may explain, at least in part, the immunosuppressive and anti-inflammatory effects of high-dose IgG therapy.7-11 For example, IgG preparations transiently suppress the in vitro production of cytokines such as IL-2, IL-3, IL-4, IL-10, tumor necrosis factor β, and granulocyte-macrophage colony-stimulating factor.5,24 Also, increases in the levels of the IL-1 receptor antagonist have been reported after IgG administration,6,24,25 although this may be an in vitro phenomenon depending on adherence of serum and plasma constituents to plastic.26 The levels of the antibodies to IFNα, IL-1α, and IL-6 have varied significantly between different IgG batches and with preparations from different manufacturers. Very high anti-IFNα antibody levels have been found in some hyperimmune antiviral IgG preparations.10 

IL-1α antibodies are the most frequently found anticytokine antibodies in normal sera as well as in human IgG.8 While easily demonstrated in pharmaceutically prepared IgG, natural antibodies to IL-6 and, particularly, to IFNα can be difficult to detect in serum and plasma from healthy individuals. The reason for this is unclear. For example, attempts to separate antigen-antibody complexes have failed to increase the IFN-binding capacity of individual sera (Ross et al, unpublished). This could be because of the very high affinity of these antibodies or the presence of other factors that interfere with the antibodies and/or IFNα-antibody complexes. Another possibility is that very high-tittered IFNα antibodies, present in only a few healthy individuals, may contribute to the anti-IFNα activity found in pooled human IgG.

Endogenous antiviral activity was demonstrated in seven of 15 sera in this study, and this was significantly reduced by the IgG in preinfusion sera and after IgG administration. This indicates direct neutralization of IFNα in the blood by the specific antibodies in the administered IgG preparations. The lack of a significant reduction in the levels of circulating IL-6 could be due to the relatively low levels of anti–IL-6 antibodies in the IgG preparations.

In conclusion, high-dose IgG therapy increased the binding of cytokines to IgG in patients' sera, most likely because of the presence of specific anticytokine antibodies in the IgG preparations. The endogenous antiviral effect in these sera was significantly reduced after the infusion of anti-IFNα antibody positive IgG. While it may prove useful to select IgG preparations with high anticytokine levels for the management of certain immunoinflammatory diseases, it may also be beneficial to administer IgG preparations depleted of anti-IFNα antibodies, particularly if given to patients with known or suspected viral diseases.

The expert technical assistance by Merete Tjalve, Susanne Meldgaard, and Ole Christensen is greatly acknowledged.