Adverse immune responses severely hamper the success of biopharmaceutical therapies. Possible clinical consequences include anaphylaxis, reduced drug half-life and neutralization of the therapeutic protein as well as the endogenous human homologue. Controlling potential triggers of the immune system helps to minimize the immunogenicity of biopharmaceuticals, a crucial consideration in biopharmaceutical manufacturing. This review summarizes the latest advancements that have been made towards insight into the impact of structural characteristics on the immunogenicity of therapeutic proteins. Examples are given to illustrate the role of critical quality attributes, such as protein conformation, glycosylation, chemical modifications and aggregation, in immunogenicity. During the development of biopharmaceutical products, it is important to not just assess the risk for immunogenicity in clinical trials, but to ensure product quality throughout drug design, cell-line selection, upstream and downstream processing, all the way to to the final product.

PurposeTo study the influence of protein aggregation on the immunogenicity of recombinant human interferon beta (rhIFNβ) in wild-type mice and transgenic, immune-tolerant mice, and to evaluate the induction of immunological memory.MethodsRhIFNβ-1b and three rhIFNβ-1a preparations with different aggregate levels were injected intraperitoneally in mice 15× during 3 weeks, and the mice were rechallenged with rhIFNβ-1a. The formation of binding (BABs) and neutralizing antibodies (NABs) was monitored.ResultsBulk rhIFNβ-1a contained large, mainly non-covalent aggregates and stressed rhIFNβ-1a mainly covalent, homogeneous (ca. 100 nm) aggregates. Reformulated rhIFNβ-1a was essentially aggregate-free. All products induced BABs and NABs in wild-type mice. Immunogenicity in the transgenic mice was product dependent. RhIFNβ-1b showed the highest and reformulated rhIFNβ-1a the lowest immunogenicity. In contrast with wild-type mice, transgenic mice did not show NABs, nor did they respond to the rechallenge.ConclusionsThe immunogenicity of the products in transgenic mice, unlike in wild-type mice, varied. In the transgenic mice, neither NABs nor immunological memory developed. The immunogenicity of rhIFNβ in a model reflecting the human immune system depends on the presence and the characteristics of aggregates.

PurposeTo study the effect of oxidation on the structure of recombinant human interferon beta-1a (rhIFNβ-1a) and its immunogenicity in wild-type and immune-tolerant transgenic mice.MethodsUntreated rhIFNβ-1a was degraded by metal-catalyzed oxidation, H2O2-mediated oxidation, and guanidine-mediated unfolding/refolding. Four rhIFNβ-1a preparations with different levels of oxidation and aggregation were injected intraperitoneally in mice 15× during 3 weeks. Both binding and neutralizing antibodies were measured.ResultsAll rhIFNβ-1a preparations contained substantial amounts of aggregates. Metal-catalyzed oxidized rhIFNβ-1a contained high levels of covalent aggregates as compared with untreated rhIFNβ-1a. H2O2-treated rhIFNβ-1a showed an increase in oligomer and unrecovered protein content by HP-SEC; RP-HPLC revealed protein oxidation. Guanidine-treated rhIFNβ-1a mostly consisted of dimers and oligomers and some non-covalent aggregates smaller in size than those in untreated rhIFNβ-1a. All degraded samples showed alterations in tertiary protein structure. Wild-type mice showed equally high antibody responses against all preparations. Transgenic mice were discriminative, showing elevated antibody responses against both metal-catalyzed oxidized and H2O2-treated rhIFNβ-1a as compared to untreated and guanidine-treated rhIFNβ-1a.ConclusionsOxidation-mediated aggregation increased the immunogenicity of rhIFNβ-1a in transgenic mice, whereas aggregated preparations devoid of measurable oxidation levels were hardly immunogenic.

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Ara h 1, a major peanut allergen, is known as a stable trimeric protein. Nevertheless, upon purification of native Ara h 1 from peanuts using only size exclusion chromatography, the allergen appeared to exist in an oligomeric structure, rather than as a trimeric structure. The oligomeric structure was independent of the salt concentration applied. Subjecting the allergen to anion exchange chromatography induced the allergen to dissociate into trimers. Ammonium sulfate precipitation did not bring about any structural changes, whereas exposing the allergen to hydrophobic interaction chromatography caused it to partly dissociate into trimers, with increasing amounts of trimers at higher ionic strengths. The (partial) dissociation into trimers led to a change in the tertiary structure of the monomeric subunits of the allergen, with the monomers in Ara h 1 oligomers having a more compact tertiary structure compared with the monomers in Ara h 1 trimers. As structural characteristics are important for a protein's allergenicity, this finding may imply a different allergenicity for Ara h 1 than previously described.

Like many other therapeutic proteins, recombinant human interferon beta (rhIFN-β) elicits undesirable immune responses. rhIFN-β-treated multiple sclerosis patients may form binding antibodies and neutralizing antibodies (NAbs), with the latter being responsible for inhibition of the therapeutic effect of the protein. The incidence of binding antibodies and NAbs against rhIFN-β as well as the titer and persistence of NAbs differ among the marketed products. The proportion of patients forming antibodies against rhIFN-β-1b is higher than that against rhIFN-β-1a, which is likely explained by the differences in protein structure and aggregation behavior between the 2 types of rhIFN-β. Here, we summarize the different factors influencing the immunogenicity of rhIFN-β in patients with multiple sclerosis and discuss the role played by rhIFN-β aggregates.

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