Rapid and Inexpensive Characterisation of Immunoassay Conjugates (RIChIC)

Fleet Bioprocessing Ltd. are experts in the development of immunoassays, widely-used tests for the diagnosis of diseases which rely on the well-known specificity of antibodies to detect specific molecules. Examples in common use include tests for detecting HIV and hepatitis, for diagnosing thyroid hormone abnormalities, or for differentiating heart attacks from other conditions such as angina which may display similar symptoms. New immunoassays are under development all the time, e.g. to improve the detection of cancer tumours or to monitor factors associated with the development of Alzheimer's disease.

Immunoassays rely on the successful chemical "labelling" of antibodies and related proteins, so for example that they can be detected efficiently via the presence of a fluorescent dye - and Fleet are expert in the bioconjugation techniques required for this purpose. Fleet routinely use simple analytical techniques to characterise these labelled antibody conjugates, allowing us to determine basic information such as the antibody concentration and the mean number of dye molecules per antibody molecule.

However these techniques tell us nothing about whether the labelled antibody conjugate has retained its ability to detect the molecule of interest, or has been damaged in the labelling process. For example it is possible to attach too many dye molecules to an antibody, with the result that its ability to bind the target molecule is compromised. It would be very useful to have access to a rapid, inexpensive analytical method allowing us to confirm that the conjugate has successfully retained its structure during the labelling procedure.

Fleet have evaluated several techniques for this purpose, but to date all have failed to meet our requirements; simple techniques based on spectroscopy which would meet our needs of being rapid and inexpensive have not shown adequate sensitivity to differentiate between "good" and "bad" conjugates, while techniques capable of achieving the required sensitivity have proved prohibitively expensive and/or time-consuming.

An initial project with LGC and NPL (completed in March 2019) identified techniques with exciting potential to fill this knowledge gap, and to better understand the mechanism of conjugate inactivation. This follow-up project aims to confirm the potential of these techniques. Fleet will prepare a range of antibody conjugates for evaluation and assess them in a model immunoassay, while LGC and NPL will characterise them using a range of candidate analytical techniques. This will hopefully allow us to confirm the capability of these techniques for routine use by Fleet Bioprocessing Ltd.