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News & Blogs » Antibody News » What is an Anti-Idiotypic Antibody?
An Introduction to Therapeutic Chimeric Antigen Receptor T Cells

How Anti-Idiotypic Antibodies are Essential to Drug Discovery

What is an Anti-Idiotypic Antibody?

Jan 19, 2018

As shown in figure 1, an anti-idiotypic (Anti-ID) antibody binds to the idiotype of another antibody, usually an antibody drug. An idiotype can be defined as the specific combination of idiotopes present within an antibodies complement determining regions (CDRs). A single idiotope, is a specific region within an antibodies Fv region which binds to the paratope (antigenic epitope binding site) of a different antibody. Therefore, and idiotope can be considered almost synonymous with an antigenic determinant of an antibody.

A: Antibody Drug Targeting Antigenic Epitope

B: Anti-Idiotype Antibody targeting Antibody Drug

Figure 1. Structure of anti-idiotype antibody. (A) The paratope of an antibody drug will bind to the epitope of a target antigen within the antibody drugs CDR region. (B) The paratope of an anti-ID will bind to the idiotope of its target antibody drug. The idiotope is within the antibody drug CDR region and could be next to, identical too, or far from the antibody drugs antigen binding site.

Types of Anti-Idiotype Antibodies

There are three main classifications of detection based anti-ID antibodies as shown in figure 2. The first is an antigen blocking anti-ID antibody, named so because the targeting antibodies paratope and idiotope overlap with one another. Because of this, the antibody drug’s target antigen and the anti-ID antibody will compete with one another. Therefore, this form of anti-ID antibody will only detect free antibody drug. The second classification of anti-ID antibody is called non blocking because the antibody drug’s paratope and idiotope do not overlap. Therefore, the anti-ID antibody and the antigen can simultaneously bind to the antibody drug without affecting one another's binding capability. Because of this, non-blocking anti-ID antibodies are used to detect all forms of available antibody drug (free or antigen bound). The third classification of anti-ID antibody is a complex specific anti-ID. This is because the anti-ID antibody cannot bind to the antibody drug unless the drug is already bound to its antigen. Therefore, this type of anti-ID antibody is only able to detect bound antibody drug.

A: Antigen Blocking Anti-ID Antibody

B: Non-Blocking Anti-ID Antibody

C: Complex Specific Anti-ID Antibody

Paratope-Specific
Inhibitory
Neutralizing
Detects Free Drug

Not Paratope-Specific
Not Inhibitory
Detects Total Drug (free, partially bound, and fully bound)

Drug-Target Complex Specific
Not Inhibitory
Detects Bound Drug

Figure 2. Types of anti-idiotype antibodies. (A) Antigen blocking anti-IDs bind directly to the antigen binding site of an antibody drug, directly competing with target antigen. (B) The idiotype which non-blocking anti-IDs bind too does not overlap at all with the paratope of the antibody drug, allowing the antibody drug to bind its target antigen and an anti-ID simultaneously. (c) Complex specific anti-IDs will only bind to the idiotope of an antibody drug when that drug is already bound to its appropriate antigen.

Uses of Anti-Idiotype Antibodies

Pharmacokinetic Assays

Since most anti-ID antibodies are generated against a specific antibody drug, they are commonly used in preclinical practices for pharmacokinetic (PK) analysis. PK is the study of drug metabolism throughout the body. Specifically, clinicians will determine the rate of drug absorption, distribution, bioavailability, and excretion in various cohorts of patients. In order to accomplish this, researchers need to be able to track antibody drugs which are bound or unbound to their designated target at various time points post delivery. Through the use of anti-IDs, primarily mAb’s, various forms of antibody therapeutics can be easily tracked and quantified in patient serum, blood, urine, or other bodily fluids. Examples of pharmacokinetic assays (ELISA format) using anti-IDs are shown in figure 3.

Figure 3. Types of ELISA Based PK Assays. There are 4 common ways of performing an ELISA based PK assay. (1) The antigen capture assay involves an antigen coated plate which is aloud to bind free antibody drug. A labeled anti-ID is then washed over the antibody drug, bound, and visualized. A similar visualization protocol is used for the other three types of PK assays. (2) An Anti-ID bridging assay involves an anti-ID coated plate which is washed over with a free antibody drug followed by a labeled anti-ID. (3) An anti-ID capture sandwich assay involves an anti-ID coated plate washed with a labeled anti-constant region IgG. (4) An anti-ID antigen-bridging assay is when an anti-ID coated plate is washed with antibody drug bound to a labeled antigen.

Immunogenicity Assays

Polyclonal anti-IDs are commonly used for immunogenicity assays as reference controls. Immunogenicity is the ability of a therapeutic, such as an antibody drug, to induce a humoral and/or cell-mediated immune response which leads to development of anti-drug- antibodies (ADAs). ADAs lead to the negation of all antibody drug related effects, essentially completely inhibiting the therapeutic aspect of the drug. Therefore, it is extremely important for researchers to analyze the immunogenicity of a new antibody drug during preclinical analysis. An ADA is very similar to an anti-IDs since both bind to the same antibody drug, therefore a pool of polyclonal anti-IDs can be used as positive controls when analyzing for the presence of ADAs within patient samples. An example of an ELISA based immunogenicity assay using an anti-ID as a positive control is shown in figure 4.

Figure 4. Types of Immunogenicity Assays. (A) If an antibody drug induces the development of ADAs, the ADAs can be visualized through a direct binding ELISA. In this assay, an antibody drug coated plate is washed with serum. The plate is then washed with a labeled IgG which only binds to the constant region of ADAs. Therefore, the ELISA will only fluoresce if there are ADAs present in the sample serum. (B) A bridging ELISA assay is when an antibody drug coated plate will be exposed to ADA containing serum which binds to one ScFv region of an antibody drug. The remaining ADA ScFv region will bind to a labeled version of the same antibody drug. Both of these assays need be analyzed via a positive control, such as anti-IDs.

GenScripts Anti-Idiotype Antibody Generation Packages

GenScript now offers distinct anti-ID generation packages, which are specific to the downstream application, host species, and clonality of your choosing. GenScript’s anti-ID generation packages include….

Rodent mAb: Immunize mice or rats with your antibody drug to develop strong anti-ID antibodies generated in as little as 3 months time for the perfect price! The deliverables include stable hybridoma cell lines, purified mAb, and a fully comprehensive COA report analyzing blocking type and specificity testing.

Rabbit mAb: Anti-ID antibodies generated using GenScripts MonoRabTM platform bind with the highest specificity and sensitivity on the market. After in house parental clone supernatant analysis, positive clones go through V region sequencing, allowing for optimum recombinant expression of your selected mAb. This package also includes guaranteed delivery of a second biotin conjugated anti-ID mAb pair to allow for easy generation of sandwich ELISA based PK analysis.

Rabbit pAb: GenScript’s rabbit pAbs provide a convenient turn around time and price range for customers interested in using polyclonal anti-ID’s for immunogenicity analysis. Using our express antibody generation protocol and extensive purification and screening process, GenScript rabbit anti-ID pAb’s are a reliable option for your next project.

Click here to learn about ready-made anti-idiotype antibody products against blockbuster drugs.

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