ANTIBODY PHAGE DISPLAY FOR DIAGNOSTIC APPLICATIONS

Is antibody cross-reactivity hindering your diagnostic application development? Maximize your antibody selectivity and reduce background noise by choosing our antibody phage display tailored for diagnostic applications. Generate highly selective antibodies, fully adapted to different diagnostic platforms in as little as 7 weeks. Benefit from the unique advantages of phage display to create the ideal tools for fast and differential diagnostics.

Antibodies for diagnostic applications are prized for their specificity and ability to target cryptic antigens. For these reasons, rabbit antibodies and camelid-derived nanobodies present considerable advantages in comparison to their mouse monoclonal counterparts.

Rabbit monoclonal antibodies, for instance, have naturally higher antigen-binding affinities and specificities, making them ideal to detect low abundance markers in complex samples, a vital property for robust early diagnostic tools. Furthermore, rabbit monoclonal antibodies are particularly useful when researchers and clinicians need to distinguish between different isoforms of the same disease marker (i.e. post-translational modifications, single-point mutations, etc.), a vital property of differential diagnostic tools for establishing disease severity and predict clinical outcomes as early as possible.

VHH single domain antibodies can be considered complementary to rabbit monoclonal antibodies for diagnostic applications. These small molecules distinguish themselves from their monoclonal counterparts in terms of size (15 kDa opposed to 150 kDa in monoclonal antibodies) and complexity (no glycans attached to their structures). These properties endow them with the ability to diffuse efficiently across tissues making them desirable for a plethora of different diagnostic techniques including advanced imaging.

Our phage display services for diagnostic applications

Naïve versus immune libraries for diagnostic applications

Choosing between naïve and immune libraries for phage display can be especially challenging. For this reason, we believe it should be done on a case-by-case basis, following a detailed analysis that considers the nature of the antigen and the intended format of the diagnostic application.

In general terms, naïve antibody libraries are less limited than their immune counterparts, as such, a single high-quality naïve library can be used to isolate binders against multiple antigens or epitopes, while an immune library is biased towards a specific antigen and serves only to isolate antibodies specific to a single antigen or pathogen.

Moreover, naïve libraries allow the generation of high-quality antibodies with moderate to high affinity in as little time as possible (about 7 weeks). This is particularly desirable for the development of fast response diagnostic platforms and extensive diagnostic screening applications based on lateral flow assays (LFA), enzyme-linked immunosorbent assay (ELISA), and clinical imaging.

Immune libraries as the result of antigen-challenged antibody repertoires and are sparsely used to achieve higher affinities in challenging and complex projects.

Unique advantages of antibody phage display for diagnostic applications

Fast and differential diagnostic platforms require highly selective (low cross-reactive) antibodies to detect low-abundance markers and distinguish between different isoforms. ELISA is one of the most popular formats during the early stages of diagnostic and wide-range population screening studies. ELISA tests are particularly flexible and can be designed to either target specific antibodies or antigens via several formats:

• Direct detection using labeled primary antibodies (bind to the main target)
• Indirect detection using primary antibodies and labeled secondary antibodies (bind to the primary antibodies)
• Sandwich detection using antibody pairs (bind to non-overlapping epitopes of the same antigen)

The use of antibody pairs is greatly beneficial when aiming to detect low abundance markers with high accuracy. However, developing robust antibody pairs can be challenging due to the need to exert precise control over which epitopes are recognized by both antibodies. Phage display technologies are well-fitted to solve this challenge since biopanning can be performed efficiently and quickly with different peptides (epitopes) ensuring these antibodies have no epitope cross-reactivity and can be used in the same custom assay.

Another particularly useful technique for fast, early, and differential diagnostics is flow cytometry. Typically employing fluorescence labeled antibodies, this technique can be used in multiplexing conditions to detect different markers in the same sample and estimate their relative abundances. These assays are also challenging to develop due to the need to ensure flow cytometry antibodies don’t bind off-target. For this reason, it is advisable to develop a single antibody panel (a mixture of antibodies binding to different antigens) in a single workflow and the flexibility of phage display is well adapted to tackle that challenge.

Must-have properties of robust diagnostic antibodies

Antibodies have become extremely important tools for current medical diagnostic technologies. Moreover, researchers are increasingly interested in designing antibodies able to detect even the slightest changes in a patient’s proteome for accurate early and differential diagnoses of diseases that are hard to detect.

For this reason, diagnostic antibodies should possess distinctive properties including:

• Enhanced stability ensuring the long shelf-life of these products and making them easier to send and distribute during disease outbreaks or to remote locations
• High selectivity high background noise can mask the detection of low-abundance markers, for this reason, it is important to minimize off-target binding to optimize the detection limit
• Validated in target application sample origin, preparation, and assay format dictate the efficiency of a given diagnostic antibody, for this reason, it is vital to validate the antibody in its target application and assay conditions to ensure it maintains its selectivity and binding efficiency

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