Western Blot Applications for Medical Diagnosis

In recent medical field, Western Blot has a wide range of applications in medical diagnosis, such as the application of medical diagnosis for HIV (Human Immunodeficiency Virus) infection, BSE (Bovine Spongiform Encephalopathy, also known as "mad cow disease"), FIV (Feline Immunodeficiency Virus), HBV (Hepatitis B Virus) infection, and so on.

Usually, Western Blot is used as a confirmatory test for these diseases, following a high sensitivity ELISA (Enzyme-Linked Immuno Sorbent Assay) test with positive results.

Western Blot medical diagnosis for different diseases

Western Blot application: as a confirmatory test for Lyme disease

Lyme disease is a multi-organ animal-borne disease, caused by spirochetes of Borrelia burgdorferi (Bb), which typically affect the skin, nervous system, musculoskeletal system and heart. A history of confirmed exposure to tick bites, typical signs and symptoms of Lyme borreliosis and positive tests for anti-Bb antibodies, are the basis of a diagnosis.

The U.S. Centers for Disease Control and Prevention (CDC) recommends a two-tier protocol using an enzyme-linked immunosorbent assay or Immunofluorescence Assay (IFA) initially, followed by the more specific Western blot to confirm the diagnosis when the assay samples are positive or equivocal. The reliability of testing in diagnosis remains controversial. Studies show the Western blot IgM has a specificity of 94–96% for patients with clinical symptoms of early Lyme disease. The initial ELISA test has a sensitivity of about 70%, and in two-tiered testing, the overall sensitivity is only 64%, although this rises to 100% in the subset of people with disseminated symptoms, such as arthritis.

Western Blot application: as a confirmatory test for HIV infection

Human Immunodeficiency Virus (HIV) can be divided into two major types, HIV type 1 (HIV-1) and HIV type 2 (HIV-2). HIV-1 is related to viruses found in chimpanzees and gorillas living in western Africa. HIV-2 is related to viruses found in sooty mangabeys. HIV-1 viruses may be further divided into groups. The HIV-1 group M viruses predominate and are responsible for the AIDS pandemic.

Western Blot is the benchmark test for confirming a diagnosed HIV infection followed by the ELISA test. However, since 2014, CDC have recommended discontinuing the Western blot test for HIV, as other tests are now more reliable and enable a faster diagnosis.

In the Western blot test, the sample is separated with an electrical current and transferred onto a piece of blotting paper. And an enzyme is added to cause color changes that signal the presence of HIV antibodies.

Western blot HIV tests usually look for antibodies against the following HIV proteins:
• Proteins from the HIV envelope: gp41, and gp120/gp160.
• Proteins from the core of the virus: p17, p24, p55
• Enzymes that HIV uses in the process of infection: p31, p51, p66

A drawing of results of a western blot test
#1: a control; #2: positive; #3: negative.

Western Blot application: as a confirmatory test for FIV infection

Feline immunodeficiency virus (FIV) is a lentivirus that causes an immunodeficiency syndrome in cats and is structurally similar to the human immunodeficiency virus (HIV).

Diagnosis of FIV requires an FIV antibody test. ELISA (enzyme-linked immunosorbent assay) is a simple test that can be done in most veterinary laboratories and clinics. Test results are available within 10 to 20 minutes. False positives can occur, so all cats that test positive should be retested with a Western blot assay. The Western blot detects the presence of FIV-antibodies in the cat's blood using slightly different technology. The Western Blot is considered the confirmatory test for FIV. If the western blot result shows positive, consider FIV-infected and continue appropriate management program and/or treatments. If the western blot shows a discrepant negative result, then the FIV infection may be in early stage or initial ELISA results may be incorrect.

Western Blot application: as a confirmatory test for BSE infection

Bovine spongiform encephalopathy (BSE), commonly known as "mad cow disease", is a type of transmissible spongiform encephalopathy (TSE). Transmissible spongiform encephalopathies (TSEs), or prion diseases, are fatal neurological disorders in both animals and humans. BSE can be divided into three distinct forms, classical (C-), low (L-) or high (H-) type.

Western Blot is recognized as a confirmatory test for BSE. The diagnosis is made by recognizing three distinctive bands that are identified as a result of a reaction with the anti-prion protein antibody. In addition to Western Blot, Immunohistochemistry (IHC) is also a confirmatory test for BSE.