ELISA (Enzyme-Linked Immunosorbent Assay) is a widely used technique for detecting antigens or antibodies. It involves coating a microtiter plate with an antigen or antibody and detecting its binding with an enzyme-linked secondary antibody. There are several types of ELISA including direct, indirect, sandwich, and competitive ELISA, which differ in their detection methods and targets. ELISA has many applications, such as detecting antibodies for diseases like tuberculosis, hepatitis B, and HIV, as well as detecting food allergens and bacterial toxins.

1. ELISA TEST
by Neelma nayab

2. CONTENT
• INTRODUCTION
• NOMENCLATURE OF ELISA
• BASIC PRINCIPLE OF ELISA
• MATERIAL REQUIRED FOR ELISA TEST
• TYPES OF ELISA
• APPLICATIONS OF ELISA

3. INTRODUCTION
• ELISA(Enzyme Linked ImmunoSorbent assay) is a widely used
technique for detection of antigen (Ag) or antibody(Ab).
• The technique was developed in 1971 by Peter Perlmann and Eva
Engvall at Stockholm University, Sweden.
• A technique to prepare something like immunosorbent to fix antibody
or antigen to the surface of a container was published by Wide and
Jerker Porath in 1966 Eva Engvall Peter Perlmann

4. • EL: The second antibody is attached to an enzyme (‘enzyme-linked’)
• I: Antigen is recognized by specific antibody (‘immuno’)
• S: Antigen of interest is absorbed on to plastic surface (‘sorbent’)
• A: Substrate reacts with enzyme to produce a product, usually
colored, which can be assessed (‘assay’)
ELISA NOMENCLATURE

5. BASIC PRINCIPLE OF ELISA
• Enzyme is used to detect the binding of Antibody – Antigen
• Enzyme converts colorless substrate into colored product, indicating
the presence of Antibody - Antigen complex
• ELISA can be used to detect either presence of Antigens or Antibodies

6. ELISA: MATERIAL REQUIRED
substrate
Antibody (1st and
2nd)AntigenMicrotiter well
Blocking buffer
TESTING
SAMPLE
Washing buffer

7. Types of ELISA
• DIRECT ELISA
• INDIRECT ELISA
• SANDWICH ELISA
• COMPETENT ELISA

8. DIRECT ELISA
• Direct ELISA detects the presence of antigen in a sample
• Microtiter wells are initially coated with antigen to be detected which
is followed by an antibody linked to an enzyme conjugate.
• This follows the addition of substrate which produces colour
detected using ELISA detector.

10. INDIRECT ELISA
• It is used for detection of an antibody in the given sample.
• Microtiter wells are initially coated with antigen specific for antibody
to be detected, followed by the addition of sample.
• Enzyme conjugated Secondary Antibody is added followed by the
substrate which forms a coloured reaction product.

12. SANDWICH ELISA
• It is used for detecting an antigen in the given sample.
• Microtiter wells are initially coated with monoclonal
antibodies(called capture antibody) raised against antigen to be
detected, followed by addition of sample.
• Any trace of antigen is detected by adding primary antibody (a
MAb),followed by enzyme conjugated secondary Ab and a
chromogenic substrate; or by directly adding an enzyme conjugated
primary Ab.

14. COMPETENT ELISA
• This variation of ELISA is used to quantitatively estimate the amount
of antigen in the given sample
• Ag and Ab are initially incubated so that they form Ag-Ab complex.
• This mixture is then added to microtiter wells coated with synthetic
analogue of antigen to be detected, any free antibody binds to these
antigens .
• This complex is estimated by enzyme conjugated secondary antibody
by chromogenic detection .More the amount of antigen in the
sample, lesser is the antibody available to bind to microtiter wells.

15. COMPETENT ELISA

16. APPLICATIONS OF ELISA TEST
• ELISA can detect both antigen and antibody it is a useful tool for
determining serum antibody concentrations .
• It has also found applications in the food industry in detecting
potential food allergens, such as milk, peanuts, walnuts, almonds, and
eggs.
• The other uses of ELISA include:
A. Detection of Mycobacterium antibodies in tuberculosis
B. Detection of hepatitis B markers in serum
C. Detection of enterotoxin of E. coli in feces
D. Detection of HIV antibodies in blood samples