ELISA – Conception and Applications
19th August 2015
By: Laura McAleer, Technical Services Scientist,
Since its conception in the early 1970’s the Enzyme Linked Immunosorbent Assay (ELISA) has been a primary method of analyte detection. In its four decades it has become a fundamental tool in a wide range of scientific fields, its diverse nature demonstrated by its range of uses. The ELISA was the first screening test widely used for HIV due to its high sensitivity. It is now also used in the in vitro diagnosis of various diseases such as the mycobacterium that causes Tuberculosis and Hepatitis B in serum. ELISAs are so versatile and effective that, adaptations to the technology means anyone (well, almost…) can do one at home – using the home pregnancy test which utilizes the principle of a sandwich ELISA on a stick! Prior to the introduction of ELISA for detecting pregnancy in the 1960’s, the urine of a potentially pregnant women was injected into a frog. If the frog spawned within 18 hours the women was pregnant. While the frogs were not hurt through this procedure, an ELISA is certainly a better alternative.
More recently, ELISAs have also been developed in a similar way as the pregnancy test but will detect gluten in food and drink – levels as low as 10ppm!
In the age of technology, why is such a basic technique still so widely used?
Over the past 40 years, technology in everyday life has transformed the world around us. Mobile phones have been available in the UK since the 1980 but it wasn’t until the early 2000 they really took off with around 50% of the population owning one. Now very few people in the UK would be without and the figure now stands at approximately 90%. And let’s not forget about the internet…who could live without that now?!
We have also witnessed technology quickly become totally obsolete – Apple’s Macintosh computer, along with its software Claris Works was replaced in a short space of time, by its own creators, with the iMac.
In the same way, technology has also transformed many areas of scientific research. Polymerase chain reaction was initially carried out by manually incubating the reaction mix in waterbaths at different temperatures for varying times. Automated thermocyclers revolutionized the method by eliminating the labour intensive incubation steps and dramatically increasing the reproducibility between reactions.
However, (unlike the Macintosh) and despite all the advances and new technologies, the ELISA has remained much the same as it once was. Certainly, there have been improvements and new takes on the classic ELISA but with the range and various types of ELISA available this was inevitable. Why?
For one thing, it is a safer alternative to its predecessor – radioimmunoassay. While radioimmunoassays are sensitive methods which are far from obsolete, they use radioisotopes which require special precautions to protect the user and special licensing.
Automation or partial automation designed to carry out full assays or individual steps, such as the delicate wash process reduce the set up time and standardize the steps, providing greater accuracy and sensitivity.
Moreover, the numerous variants of the ELISA (See Diagram A) and multitude of detection’s available provide versatility and vast possibilities for future development and investigations with the assay.
Mass Spectrometric Immunoassay (MSIA) is a new technology which is designed to provide fast and reproducible data using high throughput testing of large biomolecules. This new technology may be the future of immunoassays but due to high set up costs, along with training on the equipment, method and analysis, ELISAs will remain a firm favourite for the foreseeable future.
What is next for the ELISA?
Along with being a great diagnostic tool, the different types of ELISAs have been employed by researchers as a highly sensitive analytical method. This holds especially true in the rapidly growing biosimilars market.
As one of the many methods available to characterize the similarity of a biosimilar molecule to its innovator, ELISAs have been at the forefront of this field. More recently, the FDAs demand for “fingerprint like” identity of biosimilars has placed emphasis on the importance of a comprehensive and orthogonal characterization approach to maximize the potential to detect differences. To this end, ELISAs provide an important side of this approach – to define the similarity of biosimilar binding in comparison to the innovator drug. Exciting new ways to utilize the classic method in relation to the biosimilars characterization are being developed such as bridging ADCC ELISA which provides a link between the cells based ADCC assay and ELISA and ultimately demonstrate we can use an ELISA to measure ADCC.
The continued popularity of the ELISA and its evolution means that it’s likely to stick around as a core laboratory method for the foreseeable future! And, like in the 1960’s, the ELISA is once again bridging the gap between cells.