Enzyme-linked immunosorbent assay antigen detection

Laboratory confirmation is vital to effective treatment of HSV, especially in individuals in whom a clinical diagnosis cannot be obtained. There are several methods by which a definitive diagnosis may be acquired, and these include virologic typing, serologic diagnosis, rapid point-of-care antigen detection, enzyme-linked immunosorbent assay (ELISA), immunoblot, and DNA polymerase chain reaction.27... 

In a direct immunoassay the immobilized antibody binds to the corresponding antigen. The competitive immunoassay relies upon the competition of the analyte with a labelled analyte for antibody binding. These formats are widely used for high throughput affinity arrays. A sandwich immunoassay is based on the trapping or capture of the analyte by another antibody. In ELISA (enzyme linked immunosorbent assays) the second antibody is conjugated with an enzyme. The bound enzyme labelled antibody is detected by its ability to break down its substrate to a colored product. 

Liposome conjugates may be used in various immunoassay procedures. The lipid vesicle can provide a multivalent surface to accommodate numerous antigen-antibody interactions and thus increase the sensitivity of an assay. At the same time, it can function as a vessel to carry encapsulated detection components needed for the assay system. This type of enzyme-linked immunosorbent assay (ELISA) is called a liposome immunosorbent assay or LISA. One method of using liposomes in an immunoassay is to modify the surface so that it can interact to form biotin-avidin or biotin-streptavidin complexes. The avidin-biotin interaction can be used to increase detectability or sensitivity in immunoassay tests (Chapter 23) (Savage et al., 1992). 

ELISA (Enzyme-linked immunosorbent assay) An immunoassay in which antibody or antigen is detected. To detect antibody, antigen is first adsorbed... 

Fluoroimmunoassays comprise a subclass of extrinsic labehng methods where various selective antigen (Ag)- antibody (Ab) immunoassay fluorescent labeling schemes yield a emission signal. One common scheme involves an enzyme-linked immunosorbent assay (ELISA) depicted in Figure 11.2 where the free Ab is tagged with a fluorophore. Numerous analytes can be detected via these types of selective lock-and-key methods. ... 

Further improvement of microchemical methods for proteinaceous media was based on immunological techniques. The high specificity of the antigen-antibody reaction enables the discrimination of the same protein coming from different species, or the detection of multiple antigens in the same sample. Application to the analysis of artwork has been reported in two types of immunological techniques immunofluorescence microscopy (IFM), and enzyme-linked immunosorbent assays (ELISA) [31]. 

Enzyme immunoassay (El A) is one of such methods that label antigen or antibody with enzyme. The most representative form of El A is the enzyme-linked immunosorbent assay (ELISA) in which bound antigen or antibody is detected by a linked enzyme that converts a colorless substrate into a colored product (Figure 6.11). 

Antibodies can be combined with enzymes and color reagents or radioactive antigens to produce quantitative testing for drugs. The ELISA or Enzyme-Linked ImmunoSorbant Assay uses antibodies generated against the Ag to be tested for covalently linked to an enzyme which can catalyze a color change reaction such as the NADH to NAD conversion (Xmax at 340 nm). When the Ag-Ab complex is formed the enzyme is activated and the color can be detected. 

Among the many immunological assay methods, the enzyme-linked immunosorbent assay methods (ELISA) are the most popular methods. ELISA can detect both antigen molecules and antibody molecules with only a slight modification of the procedure. The direct-binding and sandwich methods that are used for the... 

Additional reports include the covalent bonding of antibodies to functionalized sol-gel films55, the entrapment of polyclonal fluorescein56, the development of a sol-gel enzyme-linked immunosorbent assay (ELISA) test for antigenic parasitic protozoa57 and an immunoassay for the detection of 1-nitropyrene58. 

This chapter presents an approach to perform enzyme linked immunosorbent assays (ELISA) in a microfluidic format with electrochemical detection. This field of analytical chemistry has shown a strong activity in recent years, and many reports have presented the use of capillary-sized reactors for running immunoassays either in homogeneous format (where the antigen-antibody complex and the labelled revelation reagents are separated prior to detection, as for instance by capillary electrophoresis [1-3]) or in heterogeneous format (where the antibody is immobilised on the inner surface of the microsensor device [4] or on microbeads [5,6]). 

Specific antibodies can also be used to quantify the amount of the corresponding antigen in a biological sample. Several types of immunological assays exist. An increasingly popular version is enzyme-linked immunosorbent assay (ELISA) (see Fig. 1) which can readily detect and quantify less than a nanogram of a specific antigenic protein. In ELISA, the specific antibody is coupled to a solid support. A convenient format for ELISA is to use a plastic tray that has molded... 

Newer techniques have equal sensitivity and greater specificity Enzyme-linked immunosorbent assay (ELISA) tests can identify C. trachomatis, HSV-1 and -2, and adenoviruses through the detection of microbial antigens. In the direct ELISA, an enzyme is covalently linked to an antigen-specific monoclonal or polyclonal antibody. 

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