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The assay assesses the ability of antibodies to neutralize the Ebola virus.
On July 7, 2017, FDA announced that agency scientists have developed an assay to assess the ability of antibodies to neutralize the Ebola virus. The assay uses a technique that does not require the use of the Ebola virus and can be automated for rapid testing of large numbers of samples.
Most licensed viral vaccines are determined to be effective based on their ability to trigger production of neutralizing antibodies, FDA notes. The new assay is based on micro-neutralization, “which measures the ability of antibodies to prevent viruses from infecting animal cells and reproducing themselves. The greater the neutralization of a virus by antibodies, the fewer the number of viruses are able to infect cells and the less the viruses can replicate themselves by making copies of viral genetic material,” FDA reported in a press statement.
The assay uses vesicular stomatitis virus (VSV), a genetically modified, non-disease-causing virus, which carries part of the genome from the Ebola virus. VSV can substitute for Ebola in certain assays. Use of the VSV eliminates the need for additional precautions such as a BSL-4 laboratory, according to the agency, because the modified virus cannot cause Ebola. Therefore, the assay can be used in BSL-2 laboratories that are widely used and does not require BSL-4 containment requirements.
Different versions of VSV were genetically modified so that “each one carried on its surface one of four variations of a molecule called an envelope glycoprotein (GP) found on different strains of the Ebola virus.” Quantitative polymerase chain reaction was then used to measure the amount of genetic material produced by the hybrid VSV after exposure to commercially available antibodies to the Ebola virus. According to FDA, “the assay can determine within 6 to 16 hours if antibodies are effective against the Ebola virus.”
The assay assessed whether specific antibodies targeting each GP neutralized the different hybrid VSV variants. The results were consistent with other, more complex assays currently used. FDA stated that the assay might be adapted to assess antibodies against other viral pathogens.