Ultimately, all biologicals are immunogenic leading to the formation of anti-drug antibodies (ADA). In most cases, these antibodies are of IgG isotype. In some cases though, the antibodies are of IgE isotype, which are usually associated with type I reaction leading to signs and symptoms of allergic reactions such as rash or flushing, urticarial, dyspnea, or hypotension. Some patients may even develop potentially life-threatening anaphylaxis. Type I reactions occur within 15-30 minutes after exposure and are caused by specific IgE against allergens bound to effector cells like mast cells or granulocytes. In fact, some biological drugs can act as allergens. The allergenic risk of a biological drug depends on multiple factors, of which the glycosylation pattern is one.

The most prominent cause of allergic reactions against a biological is cetuximab, a chimeric IgG1 monoclonal antibody against the epidermal growth factor receptor (Chung et al NEJM, 2008). The authors describe a study in which 25 out of 76 patients treated with cetuximab showed a hypersensitivity reaction to the drug. The antibodies recognize a specific carbohydrate pattern called galactose-α-1,3-galactose. While IgE antibodies recognized galactose-α-1,3-galactose in cetuximab, they cross-reacted with the same carbohydrate pattern of a regional tick mainly prevalent in the area of Tennessee, Arkansas, and North Carolina. My colleagues and I also recently published an interesting article on cross-reactivity with red meat allergens (Jappe et al, 2018).

The observation of drug-specific IgE antibodies which may cause anaphylaxis prompts the need to test for these drug-specific IgE antibodies – and because IgE are 2000-fold less prevalent than IgG antibodies, a very sensitive detection method is required. For BioAgilytix, the ImmunoCAP® platform at our European headquarters in Hamburg, Germany provides an ideal system to analyze IgE-mediated drug hypersensitivities.

How the ImmunoCAP® Platform Works
The ImmunoCAP® platform is designed as a sandwich immunoassay using biotinylated drug, which is bound to streptavdine-coated solid phase to react with the drug-specific IgE in a serum sample. Each solid phase consists of a cellulose derivative enclosed in a capsule to enable high binding capacity per mg cellulose. As a result, all relevant antibodies are bound regardless of antibody affinity.

Post washing, enzyme-labeled antibodies against IgE are added to form a complex, and after incubation, the unbound enzyme-labeled anti-IgE is washed away.

For a full validation and for precise sample analysis, drug-specific IgE positive controls are required. These might be generated by genetic Fc-shuffling of drug-specific IgG antibodies. Alternatively, a drug-specific IgG positive control can be conjugated with human IgE. This complex can subsequently serve as positive control.

Automated Processing & Reproducible Results
The key advantages of the ImmunoCAP® technology lie in its ability to detect IgE in the low ng- or pg range with high precision and with high reproducibility via automated processing. Additionally, due to the protein binding capacity, drug tolerance is high. As a result, type I hypersensitivity reaction against biologicals can be measured with excellent consistency and reliability.

BioAgilytix’s Platform Expertise
Our veteran team of large molecule experts brings extensive experience working with ImmunoCAP to deliver highly reliable immunoassays and to effectively interpret the data derived for accurate IgE-mediated hyperreactivity analysis. Our Platform Comparisons Guide can help you decide if ImmunoCAP is right for your project, or you can speak to our scientists about your specific testing needs today.