MAC-ELISA

MAC-ELISA

The MAC-ELISA (IgM Antibody Capture Enzyme-Linked Immunosorbent Assay) is a diagnostic test used to detect specific IgM antibodies in a patient's serum. This test is particularly useful for diagnosing recent infections caused by various viruses, including those responsible for diseases such as dengue fever, Zika virus, and West Nile virus. The presence of IgM antibodies indicates a recent or current infection, as these antibodies are typically produced by the immune system shortly after exposure to an antigen.

Principle of MAC-ELISA

The MAC-ELISA is based on the principle of capturing IgM antibodies from a patient's serum using an antigen-coated surface. The steps involved in the assay are as follows:

1. Coating the Plate: The wells of a microtiter plate are coated with anti-human IgM antibodies. These antibodies are specific for the Fc region of human IgM, allowing them to capture IgM antibodies from the serum.

2. Sample Addition: The patient's serum is added to the wells. If IgM antibodies specific to the target antigen are present, they will bind to the anti-IgM antibodies on the plate.

3. Antigen Addition: A known antigen, specific to the virus or pathogen of interest, is added to the wells. This antigen will bind to the captured IgM antibodies if they are specific to it.

4. Detection: An enzyme-linked secondary antibody, which is specific to the antigen, is added. This secondary antibody is conjugated to an enzyme such as horseradish peroxidase (HRP) or alkaline phosphatase.

5. Substrate Addition: A substrate for the enzyme is added. The enzyme catalyzes a reaction that produces a color change, which can be measured spectrophotometrically. The intensity of the color is proportional to the amount of IgM antibodies present in the sample.

Applications

MAC-ELISA is widely used in clinical laboratories for the diagnosis of:

- Dengue Fever: Detecting IgM antibodies against dengue virus. - Zika Virus: Identifying recent Zika virus infections. - West Nile Virus: Diagnosing West Nile virus infections.

Advantages and Limitations

Advantages: - Specificity: High specificity for IgM antibodies, reducing cross-reactivity with other immunoglobulins. - Early Detection: Useful for early detection of infections, as IgM is produced shortly after infection.

Limitations: - Cross-Reactivity: Potential for cross-reactivity with other flaviviruses, which can complicate diagnosis in areas where multiple viruses are endemic. - Time-Dependent: IgM levels may decline after the acute phase of infection, leading to false negatives if testing is delayed.

Also see

- ELISA - Dengue Fever - Zika Virus - West Nile Virus - Immunoglobulin M