As a powerful diagnostic tool offering a multi-faceted snapshot of a patient’s immune system, ELISA can be used during testing and treatment for a range of serious diseases, including HIV and Covid-19. ELISA, which stands for enzyme-linked immunosorbent assay, is a type of plate-based assay. It is most commonly referred to as a blood test, though ELISA methods may also be used for testing various other fluids, including urine or serums. ELISA has been in use since the early 1970s.
ELISA can be used by doctors and researchers to detect and measure a variety of soluble substances in serum, blood samples, or urine samples. The targeted substance might be a protein, an antigen, or a hormone.
The process of ELISA testing involves immobilizing a target antigen and then introducing a reporter enzyme to it. This enzyme is linked to an antibody that targets the antigen, so the antibody activity can be detected and quantified by observing and measuring the reporter enzyme.
ELISA testing is dependent on this interaction between specific antibodies and antigens, so every ELISA will be set up to detect a different antigen. Because the detection of the target molecule is based on its reaction with a labelling enzyme, the data must be obtained over a short time span.
Types of ELISA
The first ELISA test was developed in 1971. As technology and diagnostic needs evolved, ELISA technology achieved several new iterations:
- An early precursor to ELISA testing, immunofluorescence involves labelling an antibody with a fluorescent dye rather than an enzyme. Because the dyed antibodies then bind to the antigens, this method can mark the location of the antigens inside a tissue.
- Competitive ELISA. An early offshoot of the original 1971 ELISA test, competitive ELISA is named for the mechanism by which it detects hormones. In a competitive ELISA, the action being observed and quantified is a conjugated substrate “competing” with a protein of interest. The competitive ELISA was specifically designed to detect the human choriogonadotropin hormone.
- Sandwich ELISA. The Sandwich ELISA, so-called because a target antigen is placed between two antibodies, is still widely used. The mechanism of a Sandwich ELISA occurs in four steps:
- The plate is coated with the capture antibody. This antibody reacts to the antigen of interest, and binds the antigen to the plate to keep it immobilized for the subsequent steps.
- The sample of blood, serum, or other bodily fluid is added atop the coated plate. Any antigen present in the sample will then bind to the capture antibody on the plate and remain held in place.
- A second antibody, called the detection antibody, is then added. The detection antibody is linked to an enzyme—here, alkaline phosphatase is commonly used. This detection antibody will then react as it targets and binds to any target antigens that have already been bound to the plate by the capture antibody.
- A substrate, or series of substrates, is added last. The substrate is usually in the form of a coloured substance whose action can be readily observed and measured.
- Indirect ELISA. Indirect ELISA is another method that relies on the addition of a second antibody to aid in detection. Indirect ELISA was originally developed to aid in the detection of human serum albumin.
Benefits of ELISA Testing
ELISA testing demonstrates numerous benefits when it comes to targeted measurements. These benefits include, but are not limited to:
- High sensitivity—ELISA testing can detect target particles at low levels.
- Adaptability—commercially available ELISA kits are typically produced in a 96-well plate format but can be readily converted to work with 384-well plates. ELISA can also handle a variety of sample types, including serum, plasma, cell tissue, saliva, and urine.
- Ease of use and training—the protocols for running an ELISA test are fairly straightforward, and the assay requires almost no hands-on work by personnel.
- Quantitative measurements—an ELISA doesn’t just detect the presence of the target molecules; it can measure them to determine the precise concentration present in the sample.
Using ELISA to Help Fight Antigens
The role of ELISA in fighting disease-causing antigens is largely preventative. As a detection and diagnosis tool, ELISA allows doctors to detect a variety of issues or anomalies in the immune system. This can result in the early detection of diseases, which can lead to shorter and more effective treatments for patients.
ELISA methods are not merely beneficial for the initial detection and measurement of the target antigens, proteins, and hormones. The same sorts of assays may be used throughout the course of a patient’s treatment to accurately track how well various treatment options are working to strengthen the immune system and neutralize antigens.
Choose the ELISA Platform that Meets Your Needs
As demonstrated by the history of the ELISA test, ELISA has undergone several crucial adaptations to adjust to the demands of the biotech industry and the ever-evolving disease types appearing within the human population. Choosing the ELISA platform that best meets your assaying needs is critical whether you are targeting hormones, albumin, or SARS-CoV-2 antibodies. Through diligent research and attention to quality testing with the right ELISA platform, your research can truly effect positive change.