FDA develops simple and rapid poliovirus test to speed evaluation of vaccines and support global polio eradication campaign
Scientists at the US Food and Drug Administration (FDA) have developed a test that can quickly and accurately determine how well the immune system responds to poliovirus vaccines.
The new test, which identifies all three types of the so-called Sabin strains of the virus in stool samples, will enable scientists to evaluate the ability of newly developed polio vaccines to trigger mucosal immune responses. Mucosal immune responses protect the body from infection through the mucus membranes, such as those in the intestine. In addition, because the test is a relatively simple, one-step procedure, it could enable faster processing of a large number of specimens compared to traditional virological procedures. This test could contribute significantly to the poliomyelitis eradication campaign led by the World Health Organization (WHO), according to the FDA scientists, who reported their findings in the April 2013 issue of the Journal of Virological Methods.
WHO has administered live oral polio vaccine (OPV) for the eradication campaign. However, their goal is to develop a new inactivated poliovirus vaccine (IPV), one that induces mucosal immunity, for future use. In order to evaluate the ability of the IPV to trigger protective intestinal immune responses, individuals receiving the vaccine would subsequently receive live oral polio vaccine (OPV). This vaccine would act as a surrogate (“stand-in”) for an actual virus infection. By testing stool samples, scientists could determine if the mucosal immune response was vigorous enough to eliminate the OPV by determining the amount of virus in the samples. This faster test could reduce the time it takes to evaluate IPV’s ability to trigger immune protection from several days to a single day, without the need for an elaborate laboratory.
Another application of the proposed method is for monitoring of polioviruses circulation. The WHO campaign requires continuous vaccination programs and thorough follow-up testing to ensure that communities stay free of infection. This requires testing of stool samples from large numbers of individuals to determine if vaccine-derived polioviruses still circulate in the community.
The current procedure for detecting polioviruses requires the use of cell cultures, special solutions for measuring the quantity of virus in samples and differentiating among the three types of polioviruses, and access to a specially built laboratory required for handling live viruses. This technique comprises many time-consuming steps and is therefore not appropriate for testing the very large numbers of samples needed for global surveillance of poliovirus.
In contrast, the new FDA test enables scientists to identify and measure extremely small quantities of viral genetic material using an existing technique called Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) that they modified to make simpler and faster. RT-PCR acts like a miniature, computer-based factory that churns out millions of copies of specific genes. The simple one-step version of this technique developed by the FDA scientists is designed to identify all three types of polioviruses (Sabin serotypes) generally found in stool specimens. This makes it suitable for testing the very large numbers of stool samples collected during poliovirus outbreaks and for follow-up testing after vaccination programs, to determine if any individuals are still infected.
The FDA scientists work at the Center for Biologics Evaluation and Research (CBER) in the Office of Vaccines Research and Review.
“Quantitative one-step RT-PCR assay for rapid and sensitive identification and titration of polioviruses in clinical specimens.”
Journal of Virological Methods Volume 189, Issue 1, April 2013, Pages 7-1
Majid Laassri*, Anthony DiPazza, Bella Bidzhieva, Tatiana Zagorodnyaya, Konstantin Chumakov
Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, MD 20852