Vaccines were essential for the near eradication of major diseases such as polio and smallpox, and still play a major role in the fight. For example, the Sabin’s antipolio vaccine drastically reduced the global incidence of polio from an estimated 350,000 cases in 1988 to merely 176 cases in 2019! It may seem like the poliovirus is well on its way to be completely removed from the world, but unfortunately, in recent years, there have been emerging cases of polio again. Why is that so?
Currently, the main antipolio vaccine used in the world is the oral poliovirus vaccine (OPV), which contains weakened poliovirus that is unable to infect people. However, OPVs are risky, because the weakened poliovirus in OPVs could potentially mutate and evolve into a vaccine-derived poliovirus (VDPV), regaining their ability to become infectious. These VDPVs have already caused outbreaks of polio again in areas with low vaccination coverage. In order to completely end the circulation of all polioviruses in the world, scientists have designed a new, genetically-stable poliovirus vaccine, called the novel oral poliovirus vaccine type 2 (nOPV2).
Scientists painstakingly looked at all the possible mutations in the weakened poliovirus that resulted in VDPVs, and figured out the various regions in the genome, or the genetic material, of the virus that was the most susceptible to mutations. They made five modifications in different areas of the genome and created a new polio vaccine candidate, nOPV2, which is not susceptible to genetic mutations that could cause it to become infectious again. In mice models, this new vaccine does not mutate as much and does not induce paralysis within the safe dosage of the vaccine. Importantly, nOPV2 also confers similar immunity as the current OPV, with 75%–100% of vaccinated mice successfully generating antibodies against the poliovirus.
In addition to these promising results, the authors conducted a phase I human clinical trial testing for nOPV2’s safety in humans. They determined that nOPV2 is safe for humans and retains its genetic stability. They will move onto phase II and III clinical trials soon, which could result in a new and safer polio vaccine in the future. This is the first ever vaccine that was rationally designed through observing the evolution of the virus. We could definitely learn from the strategies of this designer vaccine in our pursuits of developing vaccines for other viruses.
Managing Correspondent: Wei Li
Press Article: ‘Designer virus’ is first new oral polio vaccine in 50 years. ScienceDaily.
Original Scientific Article: Engineering the Live-Attenuated Polio Vaccine to Prevent Reversion to Virulence. Cell Host & Microbes.