Antibodies develop to varying degrees during treatment with human proteins, including insulin, growth hormone, granulocyte-macrophage colony-stimulating factor, factor VIII, erythropoietin, and interferons. These antibodies may reduce the clinical efficacy of these agents by blocking or neutralizing their biologic activity and may have other biologic effects. For example, antibodies develop in 20 % to 40% of patients with severe hemophilia treated with human factor VIII; the presence of these antibodies can result in tolerance to the clotting effects of this agent. Similarly, a proportion of patients treated with interferon alpha develop antibodies, which inhibit its therapeutic effects. Therefore, it is important to test for neutralizing antibodies during treatment with these agents, particularly in patients who are unresponsive to treatment or have breakthrough disease. This article reviews the incidence and clinical impact of antibodies that develop in response to some of the commonly used protein therapeutic agents.

Immunogenicity of recombinant human proteins: causes and consequences.

The importance of establishing a common method of reporting neutralizing antibody levels is emphasized by the fact that patients injected repeatedly with a human interferon (HuIFN) may develop such antibodies that can abrogate the beneficial effects of the treatment. The earlier experimental and theoretical constructs of Kawade led to certain recommendations by the World Health Organization (WHO) concerning the methodology of neutralization tests and how to report the resultant data. A WHO international collaborative study on two human sera with antibodies against HuIFN-alpha and HuIFN-beta provided the opportunity not only to test the theoretical concepts concerning the neutralization reaction with data obtained in different bioassay systems in different laboratories but also to obtain enough data points for statistical evaluation with bioassays having a great range of sensitivity to IFN. The analyses substantiate and extend the original conclusions of Kawade that the neutralization follows the reaction mode of low-affinity antibody, in accord with the constant proportion hypothesis by which antibody reduces IFN activity in a set ratio of added/residual biologically active IFN, a consequence of the low molar concentration of free IFN at the neutralization end point. The present results support the recommendation that the preferred way to state the index of neutralization of antibodies is a titer (t), calculated by the formula t = f(n - 1)/9, where f is the reciprocal of the antibody dilution achieving the end point, and n is the IFN concentration measured in that day's titration. The tenfold reduction unit (TRU) of neutralization is proposed for use in expressing the quantity, or unitage, of IFN neutralizing antibody. The utility of its application is explained. The use of the index of neutralization described and the proposed derivative term of antibody unitage, TRU, should help make the results from different laboratories employing different bioassay systems more readily comparable and interpretable, provided the bioassays are sufficiently sensitive to IFN.

The Neutralization of Interferons by Antibody. II. Neutralizing Antibody Unitage and Its Relationship to Bioassay Sensitivity: The Tenfold Reduction Unit

Natural interferon-alpha in combination with melphalan/prednisone versus melphalan/prednisone in the treatment of multiple myeloma stages II and III: a randomized study from the Myeloma Group of Central Sweden

A retrospective chart review was conducted to determine the effect of alpha-Interferon (alpha-IFN) on disease progresssion, symptom palliation, and survival in HIV-associated Progressive Multifocal...

/pdf/survival-prolongation-in-hiv-associated-progressive-1x27ttt1lw.pdf

Survival prolongation in HIV-associated progressive multifocal leukoencephalopathy treated with alpha-interferon: an observational study.

Interferon in the treatment of hairy-cell leukemia

Previous studies have reported a low (less than 3%) incidence of anti-interferon (IFN) serum neutralizing antibodies following treatment with IFN-alpha 2b. Since this result contrasts with a higher incidence reported with IFN-alpha 2a, the question has been raised whether differences in assay techniques and patient comparability rather than inherent differences in the molecules might account for the reported differences in antibody incidence. In this report two patient groups, 151 hairy cell leukemia (HCL) patients and 101 patients with other malignancies, who have received long-term dosing with IFN-alpha 2b, are reported. The sera of both groups were studied before, during and after treatment by various assay methodologies. Utilizing three assay techniques, a less than 3% overall incidence of serum antibody formation was confirmed in these retested samples. With over 575 samples tested in multiple assays, the radioimmunoassay, as utilized in prior reports, demonstrated 99% agreement with a bioassay. Therefore, prior speculation that the assay technique for IFN-alpha 2b might produce a high false-negative rate was disproven. Additionally, the clinical outcome of these patients also failed to demonstrate a pattern of clinical relapse. In summary, these new analyses confirm the low (less than 3%) incidence of neutralizing antibody development following treatment with IFN-alpha 2b and confirm that no high rates of clinical relapse have developed in patients treated with chronic long-term dosing. Assay methodology does not appear to be a likely explanation for the low incidence of antibody formation reported with IFN-alpha 2. Rather, the unique molecular structure and pharmaceutical formulation of IFN-alpha 2b remains the most likely explanation of its minimal antigenicity.

Anti-interferon antibodies to interferon-alpha 2b: results of comparative assays and clinical perspective.

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Anti-interferon antibodies to interferon-alpha 2b: results of comparative assays and clinical perspective.