Detection of IgG and IgM to West Nile Virus

First a little essential vocabulary.
Immunoglobulin G (IgG) and immunoglobulin M (IgM) are two classes of antibodies found in the circulatory fluids. IgG is the most common class of antibodies, while IgM is built from five IgG monomers. Both of these immunological responses can be triggered by viruses and other foreign material. These antibodies are often specific to a certain pathogen, and IgM is usually much more specific than IgG.

How can we tell that IgG and IgM are present in a Serum Sample?
Typically, there are a number of assays that can be used to identify IgM and IgG in the body’s serums. A method that has been commonly used is the ELISA method, or the Enzyme-Linked Immunoabsorbent Assay. This technique takes an antibody (or the antigen), and links it to an enzyme that can be measured by certain analytic methods. The particular technique, which captures the antibody, is referred to as MAC-ELISA.

Another type of detection is immunoflourescence assay (IFA), which depends upon a chemical linkage between an antibody (or the antigen) and a fluorescent molecule. The fluorescent molecule (a fluorochrome) will fluoresce only after this linkage has been established.

Why did they do this research?
Rapid detection of West Nile Virus in a population is important for both treatment of the disease, as well as detection and movement of the virus in a geographic area. The research reviewed in the following paragraphs was performed in order to examine the techniques, which typically are used to identify West Nile Virus. This paper focused on methods of secondary detection of the virus. In other words the authors examined ways of detecting responses to a particular antibody, instead of detecting the actual virus. The authors compared two types of analyses to a new type, which they developed.
Detection of an antibody to this virus was formerly conducted using either ELISA or MAC-ELISA techniques. These techniques require a constant supply of the actual antigen, which is not usually available in the case of West Nile Virus. The authors developed an IFA technique, which relied on similar serum collections and detection of the same antibodies. The IFA technique does not require a supply of the antigen, so may be more cost effective and practical for many institutions.