The key difference between Elisa and western blot is that Elisa or enzyme-linked immunoassay is a diagnostic tool that detects whether the patient has been exposed to a particular type of virus or another infectious agent while western blot is a technique which detects a specific protein from a protein sample.
AIDS has become a global problem, and the incidence of this deadly disease has increased alarmingly in the last few decades. HIV tests detect the presence of human immunodeficiency virus ((HIV) that causes this syndrome. Out of different HIV tests, ELISA and Western Blot are very popular today. ELISA stands for enzyme-linked immunosorbent assay, which is a plate-based assay technique. It is an enzyme immunoassay used to detect HIV antibodies. Western blot detects a specific protein from a protein mixture by the use of a labelled antibody.
Key Difference
1. Overview and Key Difference
2. What is an Elisa
3. What is a Western Blot
4. Similarities Between Elisa and Western Blot
5. Side by Side Comparison – Elisa vs Western Blot in Tabular Form
6. Summary
What is Elisa?
ELISA, which stands for enzyme-linked immunosorbent assay, was the first test designed primarily for HIV detection. It is a plate-based assay. It is used to detect HIV antibodies, and this test shows high sensitivity. In this technique, the antigens in the sample bind with the immobilized antibodies on a solid surface. Once immobilized, the antigens form complexes with antibodies linked to enzymes. Then these conjugated enzymes incubate with the respective substrate.
Figure 01: ELISA
Enzyme-substrate reaction produces a measurable coloured product. By measuring the amount of the product, the number of antigens present in the sample can be quantified. Therefore, ELISA is a very specific and sophisticated technique that requires the attention of well-skilled technicians. It is also a time-consuming process with a requirement of advanced equipment.
What is Western Blot?
Western blotting is a technique that enables the detection of a specific protein from a protein mixture. Western blot is the membrane used during the blotting procedure to get the mirror image of the protein patterns in the SDS- polyacrylamide gel. The membrane used for western blotting is mostly made up of nitrocellulose or polyvinylidene difluoride (PVDF). The membrane with the transferred protein can be used to identify a particular protein. A high-quality antibody is required for the detection of the desired protein by hybridization. The antibody binds with its specific antigen and reveals the presence of the desired antigen, which is a protein.
Figure 02: Western Blot
Transferring of the proteins from the SDS polyacrylamide gel to the western blot is performed by electroblotting. It is an effective and fast method which causes the proteins to electrophorese out of the gel and pass onto the nitrocellulose membrane (western blot).
Western blotting is useful in the detection of anti-HIV antibodies in the human serum sample. Western blot can also be used as a confirmatory test for Hepatitis B infection and a definitive test for mad cow disease.
What are the Similarities Between Elisa and Western Blot?
- Elisa and western blot are two types of techniques used to diagnose HIV.
- Both methods are based on immunodetection.
- They are based on the formation of the antibody-protein complex.
- Both methods can analyze proteins.
- Elisa and western blotting are time-consuming techniques.
- Well trained and skilled personnel are required to carry out these techniques.
What is the Difference Between Elisa and Western Blot?
ELISA is a very sensitive and very sophisticated method that detects the presence of antigen and antibody in the patient’s blood, while western blot is a technique that detects a specific protein from a protein mixture. This is the key difference between Elisa and western blot. Elisa is qualitative as well as quantitative. In contrast, western blot is qualitative. Sometimes it is semi-quantitative. When considering the time taken for the test, Elisa test is time-consuming while western blot is more time consuming than Elisa.
The below infographic summarizes the difference between Elisa and western blot.
Summary – Elisa vs Western Blot
ELISA is a very sensitive and very sophisticated method that detects the presence of antigen and antibody in our blood. On the other hand, Western blotting technique is developed to identify a specific protein from a protein mixture. This is the key difference between Elisa and Western blot. ELISA was the first test designed for the detection of HIV. In order to confirm the results of the ELISA test, Western Blot can be used. Both ELISA and Western Blot are considered indirect methods for detection of HIV.
Reference:
1. Kinman, Tricia. “ELISA: Purpose, Procedure, and Results.” Healthline, Healthline Media, 17 Sept. 2018, Available here.
2. “Western Blot.” Scitable, Nature Publishing Group, Available here.
Image Courtesy:
1. “ELISA” By BiotechMichael – Own work (Public Domain) via Commons Wikimedia
2. “Western Blotting” By Cawang – Own work (CC0) via Commons Wikimedia