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Chapter 9 : Neutralization
The neutralization test has been used in virology longer than any other serologic procedure. To test for virus neutralization, virus and serum are mixed together, incubated under appropriate conditions, and then inoculated into a susceptible living host for detection of nonneutralized virus. Nonneutralized virus is detected by looking for viral growth, using indicators such as cytopathic effect (CPE), plaque formation, or metabolic inhibition. The use of standardized components is critical to performing neutralization assays. For viral identification, well-characterized pretitered antiserum or well-standardized immune serum pools are used. Similarly, to measure antibody response to a virus, a well-characterized, pretitered virus is required. Finally, to monitor for viral inactivation (neutralization), a living host system is required. The antiserum must be standardized for use in the neutralization test by titration against both its homologous virus and heterologous virus(es). Standardization of immune serum requires that the serum be tested in the neutralization assay against the virus used to immunize the animal and closely related viruses. The neutralization capacity of antiviral monoclonal antibodies (MAb) is determined by titration against the virus of interest. Neutralization is used for typing viruses and for diagnosing infection based on the host’s immune response. It is also a research tool for dissecting how antibodies protect the host from infection and probing viral function.