What is ELIZA (ENZYME LINKED IMMUNOSORBENT ASSAY)?

ELISA is useful in the early diagnosis of a disease.

It is based on the principle of antigen-antibody interaction.

When a foreign body such as bacteria or virus enters inside a human body, it acts as an antigen and antibodies are produced against them. So, every antigen has a particular type of antibody. Now the question is how biotechnology uses the antigen-antibody interaction to diagnose a disease? 

Procedure:

Two types of antibodies are used; the first one is a normal antibody for that particular antigen. The second antibody is called enzyme-linked antibody. The main function of enzyme-linked antibody is that it imparts a particular color in the antigen-antibody interaction. 

An ELISA medium is used where normal antibodies get attached to the solid substrate. The blood sample of an individual carrying that disease is added to the medium. If antigens are present in the sample, it will bind to the antibodies present in the medium.  Other antigens are washed out. The antigen-antibody interaction cannot be seen by the naked eye.

In the next process, the enzyme-linked antibodies are added to the medium. Antigen is sandwiched between two antibodies (one normal antibody and the other enzyme-linked). When the enzyme-linked antibodies react with antigens, color reaction takes place by the enzyme linked to those antibodies. 

To measure the antigen-antibody reaction, a substrate is added which causes the enzyme to produce detectable signal, like an amplifier (YELLOW COLOR). The rate of color formation is directly proportional to the amount of antigen.

Application of ELISA Test:

• Screening test for HIV/AIDS

• HCG Pregnancy Test

• Detection of potential food allergens