West Nile IgG ELISA
The West Nile IgG Test for exposure to West Nile Virus (WNV) is an ELISA assay system for the detection of antibodies in human serum to WNV derived recombinant antigen (WNRA) (1-3). This test is to aid in the diagnosis of human exposure to the West Nile Virus.
Exposure to West Nile Virus causes a disease with a number of symptoms including encephalitis (4-7). West Nile Virus is becoming widespread and has been detected in over half of the 50 states. This test has been developed and refined using reagents produced by CDC. The West Nile assay employs a recombinant antigen called WNRA, which can be used as a rapid serological marker for WNV infection. The WNRA protein is a recombinant antigen, which consists of a stretch of peptides from two WNV antigens.
The West Nile IgG ELISA consists of two enzymatically amplified “two-step” sandwich-type immunoassays. In this assay, the microtitration wells are incubated with standards, controls or unknown serum samples. The serum samples may be directly mixed with sample dilution buffer added in the wells (also see note below). After washing, the wells are treated with an antibody specific for human IgG and labeled with the enzyme horseradish peroxidase (HRP). After a second incubation and washing step, the wells are incubated with the tetramethylbenzidine (TMB) substrate.
Note: Depending on the strength of antibody response, sera can be diluted in a diluent provided in the kit.
An acidic stopping solution is then added and the degree of enzymatic turnover of the substrate is determined by absorbance measurement at 450 nanometers. Above a certain threshold, the ratio of the absorbances of the WNRA and the control wells accurately determines whether antibodies to WNV are present. A set of positive and negative samples is provided as internal controls in order to monitor the integrity of the kit components.
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