Immuno-assays – strategie used in diagnosis of human Infectious diseases

Enzyme-linked immunosorbent assays (ELISAs) incorporate the sensitivity of simple enzyme assays with the specificity of antibodies, by employing antigens or antibodies coupled to an easily-assayed enzyme. As such ELISA is much more rapid method than immunoblotting to detect specific viral protein from a cell, tissue, organ, or body fluid. There are two main variations of ELISAs: antigen-capture ELISA (detecting viral proteins), involve attachment of a capture antibody to a solid matrix for the viral protein of interest, while antibody-capture ELISA measures the specific antibody level in a sample, by coating viral antigen protein on a solid surface. There are two principles based on antigen-capture and antibody-capture ELISAs. In a general, ELISAs are considered a highly sensitive method that can detect a fairly low number of proteins at the range of picomolar to nanomolar range (10-12 to 10-9 moles per liter). ELISA has been one of the most widely used serologic tests for detecting antibody to HIV-1. ELISA method was found useful as a diagnostic tool to detect influenza viral antigen much quicker than other conventional virus detection methods [15]. In another previous study, comparison of ELISA, with conventional methods has demonstrated ELISA superiority for the rapid detection and identification of influenza A virus [16]. A simplified and standardized neutralization enzyme immunoassay (Nt-EIA) was developed to detect measles virus growth in Vero cells and to quantify measles neutralizing antibody [17]. Newer EIA formats for hepatitis C virus diagnostics have been constantly evaluated [18,19]. As such ELISAs are being used for plethora of application both in experimental and diagnostic virology including HIV-1, dengue, and influenza [20-22]. On the other hand, although rapid than traditional plaque assays or TCID50, ELISA assays sometimes could be quite expensive, due to the cost of reagents used. Unfortunately, sometimes required antibodies may not be commercially developed as well. In contrast, attempts to develop antibodies in-house may be quite expensive. Additional variability may also be introduced due to high background signals generated by non-specific binding, or cross-reactivity with non-viral protein targets.