Scientists at the U.S. Food and Drug Administration (FDA) have developed a poliovirus assay that is faster and more versatile than those now used to monitor polio vaccine production, assess patient responses to polio vaccines during clinical trials, and do environmental surveillance of vaccine poliovirus. The assay is also the first to measure the amount of several different strains simultaneously in a mixture of polioviruses.
Unlike standard poliovirus assays, the new assay does not detect viruses by measuring their ability to damage or kill cells in a culture (cytopathic effect, CPE), a procedure that is time-consuming.
Instead, the new assay directly measures viral DNA using quantitative multiplex polymerase-chain-reaction (PCR) as an endpoint. In the multiplex PCR-based titration (MPBT) assay, cell cultures are infected with serial dilutions of test samples, lysed after two-day incubation, and subjected to a quantitative multiplex one-step reverse-transcriptase PCR. All three serotypes of poliovirus are identified and quantified in a single assay.
The development of the assay is important because it has key advantages for poliovirus vaccine development and production, as well as public health responses to the virus. The ability to identify and determine the quantity of several different viruses simultaneously enables it to rapidly process the large number of fecal samples collected from subjects during clinical trials, which is more time-consuming using the current techniques.
The assay is also suitable for public health surveillance of vaccine virus in the environment, which could make it easier to track the poliovirus. In addition, the assay can be automated for high-throughput processing of samples, further simplifying and speeding sample processing for medical and public health applications.
To determine if the MPBT assay could reliably replace current assays, the FDA scientists used it to measure concentrations of three Sabin virus strains used to make Sabin oral poliovirus vaccines. Then they compared those results to those obtained using the conventional CPE-based assay. The results were similar and the tests showed similar sensitivity. In addition, the assay identified all three subtypes of polioviruses in the same sample, unlike with the CPE assay, which can identify only one subtype at a time. Moreover, the MPBT assay was completed in two to three days instead of ten days for the conventional assay. FDA hopes that the assay will be useful for the Global Polio Eradication Initiative in its goal of eradicating polio worldwide.
Multiplex PCR-based titration (MPBT) assay for determination of infectious titers of the three Sabin 3 strains of live poliovirus vaccine
American Society for Virology, 38th Annual Meeting; 7/20/2019; University of Minnesota, Minneapolis, MN
Hasmik Manukyan, Elvira Rodionova, Tatiana Zagorodnyaya, Tsai-Lien Lin, Konstantin Chumakov, and Majid Laassri*
Center for Biologics Evaluation and Research, US Food and Drug Administration, 10903 6 New Hampshire Avenue, Silver Spring, MD 20993, USA