Clinical link between MHC class II haplotype and interferon-beta (IFN-beta) immunogenicity

Auditing protein therapeutics management by professional APCs: toward prevention of immune responses against therapeutic proteins

Alloimmunization is a crippling concern in the management of patients undergoing administration of protein therapeutics as evidenced in replacement therapy and other treatment procedures. Several issues in the genesis and modulation of such deleterious immune responses have been studied. While authors have focused on the downstream events of the specific immune response and suggested modification of protein therapeutics to eliminate epitopes that interact with B cell receptors, T cell receptors, or MHCII molecules, the mechanisms underlying Ag interaction with APCs, a step upstream of immune effectors, have been grossly neglected. We wish to emphasize that the recent knowledge in understanding the capacities of an APC to handle an Ag and the importance of the surrounding microenvironment in this process are crucial for designing novel protein therapeutics with reduced immunogenicity.

Using measurements of neutralizing antibodies: the challenge of IFN-? therapy

Although the occurrence of neutralizing antibodies (NAbs) to interferon (IFN)-beta has been acknowledged since the pivotal trials of IFN-beta in multiple sclerosis (MS), the effect of these antibodies has for several reasons been debated. The main reason for the controversies has been insufficient knowledge of the fact that clinically relevant NAbs do not appear until 12-18 months after initiation of IFN-beta therapy which make studies of 2 years or less unsuited to assess the clinical relevance of NAbs. Further, changes in NAb affinity occur and contribute to increase NAb effects by time. The present paper reviews our current knowledge of NAbs and stresses the importance of using measurements of NAbs routinely. It is concluded that NAb titres are important for the biological response to IFN-beta. Patients with low or intermediate titres may have preserved a full or partial biological response and might still benefit from IFN-beta therapy. However, persistent high titres of NAbs indicate an abrogation of the biological response and, hence, absence of therapeutic efficacy, and this observation should lead to a change of therapy. The application of the existing information about NAbs in clinical practice would lead to improved efficacy of IFN-beta treatment for the benefit of patients with MS.

Clinical validation of the "in silico" prediction of immunogenicity of a human recombinant therapeutic protein

Antibodies elicited by protein therapeutics can cause serious side effects in humans. We studied immunogenicity of a recombinant fusion protein (FPX) consisting of two identical, biologically active, peptides attached to human Fc fragment. EpiMatrix, an in silico epitope-mapping tool, predicted promiscuous T-cell epitope(s) within the 14-amino-acid carboxy-terminal region of the peptide portion of FPX. On administration of FPX in 76 healthy human subjects, 37% developed antibodies after a single injection. A memory T-cell response against the above carboxy-terminus of the peptide was observed in antibody-positive but not in antibody-negative subjects. Promiscuity of the predicted T-cell epitope(s) was confirmed by representation of all common HLA alleles in antibody-positive subjects. As predicted by EpiMatrix, HLA haplotype DRB1*0701/1501 was associated with the highest T-cell and antibody response. In conclusion, in silico prediction can be successfully used to identify Class II restricted T-cell epitopes within therapeutic proteins and predict immunogenicity thereof in humans.

Neutralizing antibodies in multiple sclerosis: a complex impact on interferon responses, magnetic resonance imaging findings and clinical outcomes

Interferon beta (IFN-β) therapy reduces relapse rate, MRI lesion development, and delays the progression of disability in relapsing forms of multiple sclerosis. As with other protein therapies, some patients develop neutralizing antibodies (NAbs) that could limit the efficacy of IFN-β. The clinical impact of NAbs is hotly debated. Non-standardized NAb assays, NAb persistence and disappearance, plus a six-month lag before a clinical effect, different IFN-β species and formulations, variable trial duration, have made interpretation of the significance of NAbs a challenging task. There is a correlation between the presence of NAb and reduced efficacy of IFN-β therapy in two- to four-year trials. However, patients destined to become NAb positive do better in the first year of IFN-β therapy. Patients with clinical worsening have surprisingly low NAb frequency and titers. Understanding the true clinical implications of NAbs will require well-controlled longitudinal studies instead of simple cross-sectional analyses, plus innovative trial designs with immune biomarkers. Multiple Sclerosis 2007; 13: S53—S62. http://msj.sagepub.com

Assessment of the immunogenicity of different interferon beta-1a formulations using ex vivo T-cell assays

Recombinant homologues of human proteins have the potential to induce an immunogenic response when used therapeutically. Each of the three interferon (IFN) beta therapies currently approved for multiple sclerosis can induce the development of neutralising antibodies, the full effects of which on IFN beta therapy remain unclear. To investigate the immunogenicity of the currently licensed formulation of subcutaneous IFN beta-1a, 22 or 44 microg three times weekly (Rebif), two new formulations of IFN beta-1a (Rebif) New Formulation [RNF]1 and RNF2) have been developed. In this study, the immunogenicity of the current formulation was investigated against RNF1, RNF2 and an IFN beta standard using ex vivo T-cells. Dendritic cells, isolated from peripheral blood monocytes donated by 26 healthy volunteers, were matured in vitro and incubated with the test antigens for 6h. Autologous CD4(+) T-cells from the same donors were added and further incubated before cytokine release was assessed by ELISpot assay and proliferation by [(3)H]thymidine pulse. Secretion of T-cell-derived interleukin-2 was 79%, 66% and 105% in incubations with RNF1, RNF2 and the current formulation, respectively (normalised to secretion with the IFN standard; p<0.05, RNF2 versus the current formulation). Secretion of IFN gamma was highly variable between donors, with no significant difference observed between formulations. Normalised values for T-cell proliferation were 56%, 44% and 88% with RNF1, RNF2 and the current formulation, respectively (p<0.05, RNF2 versus the current formulation). The immunogenic potential of RNF2 is significantly lower than that of the current formulation when tested ex vivo. This result is now being confirmed through ongoing clinical trials.

Measuring and management of anti-interferon beta antibodies in subjects with multiple sclerosis

Interferon Beta is well established as a first line agent to treat relapsing remitting Multiple Sclerosis. It frequently induces the formation of neutralising anti-Interferon Beta Antibodies (Nabs) which may abrogate the clinical efficacy of the drug. Numerous studies have shown a loss of bioactivity of the drug in the presence of Nabs. The focus has shifted to reliable quantification of Nabs and their appropriate incorporation into clinical practice. Here we review the development and persistence of Nabs, the effect on Interferon beta bioactivity, clinical and para-clinical autocome measures in trials, Nab assays and discuss management strategies to optimise the use of Interferon beta in relapsing remitting MS.

A molecular immunology approach to antibody humanization and functional optimization

We introduce a new method of humanization based on a novel and immunologically relevant metric of antibody humanness, termed human string content (HSC), that quantifies a sequence at the level of potential MHC/T-cell epitopes. Use of this quantity rather than global identity as an optimization goal enables the sampling of human diversity from distinct human germline sequences across the framework and CDR regions, and allows for the generation of multiple diverse candidate sequences. As a result engineering is carried out at finer sequence resolution relative to standard CDR grafting methods, providing for the optimization of antibody properties beyond immunogenicity such as antigen affinity and solution behavior. We have applied this method to the humanization of four antibodies with different antigen specificities. The resulting variable domains differ fundamentally from CDR-grafted antibodies in that they are immunologically more human and their humanness is derived from several discrete germline sequences. Furthermore, these antibodies bind their respective antigens better than or comparable to those of the parent antibodies without the need for affinity maturation.

Protein therapeutics: new applications for pharmacogenetics

Pharmacogenetic studies have traditionally focused on genes involved in processes that affect the pharmacokinetics of small-molecule drugs, such as drug metabolism. However, attention is shifting to the effects of genetic variations in drug targets and associated pathway components on drug responses. We describe how these variations are important for understanding differences in responses to the growing number of protein therapeutics that are entering clinical practice. Pharmacogenetic studies of these drugs are surveyed, and issues important to the success of such endeavours are discussed. As novel protein therapeutics are introduced, we anticipate that the use of pharmacogenetics will assume a key role in their development and clinical application.