Serum interferon (IFN)-neutralizing antibodies and bioactivities of IFNs in patients with severe type II essential mixed cryoglobulinemia

Distinct Immunologic Properties of Soluble Versus Particulate Antigens

Antigens in particulate form have distinct immunologic properties relative to soluble antigens. An understanding of the mechanisms and functional consequences of the distinct immunologic pathways engaged by these different forms of antigen is particularly relevant to the design of vaccines. It is also relevant regarding the use of therapeutic human proteins in clinical medicine that have been shown to aggregate, and perhaps as a result, elicit autoantibodies.

Autologous albumin enhances the humoral immune response to capsular polysaccharide covalently coattached to bacteria-sized latex beads

Abundant autologous proteins, like serum albumin, should be immunologically inert. However, individuals with no apparent predisposition to autoimmune disease can develop immune responses to autologous therapeutic proteins. Protein aggregation is a potential major trigger of these responses. Adsorption of proteins to particles provides macromolecular size and may generate structural changes in the protein, resembling aggregation. Using aldehyde/sulfate latex beads coated with murine serum albumin (MSA), we found that BALB/c mice mounted MSA-specific IgG responses that were dependent on CD4(+) T cells. IgGs were specific for MSA adsorbed to solid surfaces and noncross-reactive with human, bovine, or pig albumins. T cells induced in response to MSA augmented the primary and induced boosted secondary IgG and IgM responses specific for the T cell-independent antigen, capsular polysaccharide of Streptococcus pneumoniae type 14 (PPS14), when the latter was attached to the same bead. Similar to the anti-MSA IgG response, the boosted PPS14-specific IgG secondary response was CD4(+) T-cell dependent, displayed a typical carrier effect, and was enhanced by, but did not require, Toll-like receptor stimulation. These results provide a potential mechanism for the induction of responses to autoantigens unable to induce specific T-cell responses, and provide new insights into polysaccharide-specific immunity.

Antiviral activity of the interferon α family: biological and pharmacological aspects of the treatment of chronic hepatitis C

INTRODUCTION

Type I interferons (IFNs) comprise a group of at least 13 structurally related subtypes of IFN-α with similar, but not identical, biological activities. Each subtype displays a unique activity profile; only IFN-α2a and IFN-α2b subtypes together with natural IFN-α preparations are currently used in the clinical practice, so that the remaining IFN-α subtypes are a still unexploited reservoir of opportunity also in the new era of direct-acting antiviral agents for the treatment of hepatitis C virus (HCV).

AREAS COVERED

This paper reviews recent progress in the study of the biology of IFN family, the antiviral action mechanism and the strategies employed by HCV to evade IFN action. Currently available IFN preparations for the treatment of chronic hepatitis C infection are described and what is currently known on the pharmacokinetics, pharmacodynamics and immunogenicity of IFN-α preparations used in clinical practice are summarized.

EXPERT OPINION

The characterization of multifunctional nature of IFN system together with recent advances in the identification of HCV IFN evasion strategies and the variety of host factors influencing IFN treatment response should be considered to improve HCV and other infectious diseases treatment in the future.

Development of a protein biochip to identify 6 monoclonal antibodies against subtypes of recombinant human interferons

Recombinant human interferons (rhIFNs) are broadly used as effective therapeutic agents with antiviral, antitumor, and immune-modulating properties. Advances in protein biochip technology have benefited the medical community greatly, making true parallelism, miniaturization, and high throughput possible. In this study, 5 rhIFN proteins (IFN-alpha1b, IFN-alpha2a, IFN-alpha2b, IFN-beta, and IFN-gamma) were immobilized onto an N-hydroxysuccinimide (NHS)-modified gold-based biochip. The protein biochip was incubated with 6 specific mouse IgG antibodies (AK1, AK2, AK3, AK4, BK1, and CK1) against the human IFNs and then with Cy3-conjugated goat anti-mouse IgG antibody. The results showed that monoclonal antibody AK1 presented a unique binding characteristic to IFN-alpha1b. AK2 reacted in immunoassays equally with IFN-alpha2a and IFN-alpha2b. AK3 detected IFN-alpha1b, IFN-alpha2a, and IFN-alpha2b. AK4 had positive immunological responses directed to both IFN-alpha1b and IFN-alpha2b. Monoclonal antibodies BK1 and CK1 recognized epitope of IFN-beta and IFN-gamma, specifically. The assay specificity of the biochip was further confirmed by enzyme-linked immunosorbent assay (ELISA) and western blotting. Finally, 88 serum samples from patients treated with rhIFN-alpha2b were simultaneously tested on a single biochip. The result demonstrated that 6.8% (6 of 88 cases) presented positive reactions to anti-IFN-alpha2b antibodies, indicating that the patients under rhIFN-alpha2b therapy produced neutralized antibody against the IFN. The biochip format would offer a competitive alternative tool not only for facilitating characterization of IFN subtypes but also potentially for enabling clinical serum detection of corresponding antibodies directed against IFNs.

Expression of biomarkers of interferon type I in patients suffering from chronic diseases

Interferons (IFNs) are used widely in the treatment of viral infections, tumours and neurological disorders. The aim of this study was to evaluate the endogenous expressions of various IFN-induced compounds [specifically: neopterin (NPT), beta2microglobulin (beta2mg) and 2-5 oligoadenylate synthetase (2-5 OAS)] in patients with various chronic diseases requiring treatment with IFN type I. The results showed that patients with such chronic diseases as hepatitis C virus-associated type II mixed cryoglobulinaemia (MC), chronic hepatitis C (CHC) and relapsing-remitting multiple sclerosis (RRMS) are characterized by different activations of the IFN system. Furthermore, the interindividual variability in baseline levels of IFN-induced biomarkers was higher in patients with chronic diseases than in healthy individuals. When levels of the above biomarkers were measured 24 h after the first injection of IFN in patients with CHC or RRMS, significant increases in expression levels of IFN-induced compounds were recorded but, again, there is a broad range of variability in the degree of increase. Further, a significant inverse correlation between baseline levels of NPT, beta2mg and 2-5 OAS activity and their relative increases after IFN administration was found in patients with CHC or RRMS. Together, the results are consistent with the observation that there is considerable interindividual heterogeneity in the clinical response to IFNs, which suggests that host factors other than disease markers must be taken into account in order to manage and optimize the IFN therapy.

Rapid and simple detection of IFN-neutralizing antibodies in chronic hepatitis C non-responsive to IFN-α

Different mechanisms have been proposed for the failure of interferon (IFN) therapy in patients with chronic hepatitis C and multiple sclerosis, for example, the presence of IFN-neutralizing antibodies. In this study, a novel assay system based on the IFN-inducible Mx-promoter was used to detect IFN-neutralizing antibodies in sera of patients with chronic hepatitis C. To monitor IFN bioactivity in IFN-treated patients, a real-time RT-PCR for MxA gene expression in PBMCs was established. Using these two methods, patients with chronic hepatitis C virus (HCV) infection receiving IFN therapy and patients with treatment induced HCV clearance were monitored. Importantly, neutralizing anti-IFN antibodies were detected in the sera of 3 of 38 chronically HCV-infected patients who failed to respond to therapy but none in sera of patients who cleared HCV after IFN therapy. Interestingly, the presence of these antibodies correlated with the lack of MxA induction in PBMCs after initiation of IFN-alpha therapy. Retrospective analysis of one patient's sera revealed that the anti-IFN-alpha antibodies had already developed after the first of four unsuccessful IFN therapies, suggesting that neutralizing antibodies may have contributed to the failure of previous IFN treatments. In summary, a novel screening assay was established that may be helpful for testing IFN non-responders for the presence of clinically relevant anti-IFN-alpha antibodies and for selecting alternative IFN preparations not neutralized by these antibodies.