New Vaccine Development Shows Promise in Eradicating Polio
A group of American researchers have made a significant breakthrough in the fight against polio. The team has developed a trivalent vaccine for mice that reduces the risk of vaccine-derived poliovirus, according to the journal Nature.
Although polio vaccines have been essential in containing the ravages of this infectious disease, the goal of its eradication is becoming more elusive than was estimated decades ago. American researchers from the University of California at San Francisco and the Centers for Disease Control and Prevention in Atlanta have published the results of their work in Nature, which paves the way for the disappearance of the disease.
The Challenge of Poliovirus
Poliovirus consists of three serotypes, WPV1, WPV2, and WPV3, capable of causing poliomyelitis. Although vaccines have eradicated WPV2 and WPV3, WPV1 is still causing outbreaks in Afghanistan and Pakistan. There is also concern about the circulation of strains of vaccine-derived poliovirus (VDPV) that lead to cases of vaccine-associated paralytic poliomyelitis.
The Types of Polio Vaccines
Two types of vaccines are currently used against polio: the injectable inactivated virus (salk vaccine) and oral attenuated virus (OPV or Sabin vaccine). The most recent oral vaccine, nOPV2, is a modified version of the mOPV2 that is genetically more stable. Researchers have used the reverse genetics approach to develop new vaccines for serotypes WPV1 and WPV3, known as nOPV1 and nOPV3. The team incorporated genes encoding components of the protein coat structure of OPV1 and OPV2 vaccine virus.
Stable and Safe Vaccines
In a trial with mice, both nOPV1 and nOPV3 vaccines were shown to be highly immunogenic and safe. Even if mutations occur after vaccination, the vaccines remained attenuated.
The New Protective Shield Against Polio
The team found that the administration of a trivalent vaccine, including nOPV1, nOPV2, and nOPV3, in mice resulted in the production of antibodies against all three poliovirus serotypes, protecting the mice against the disease. This finding indicates that there was no interference between the three viruses in terms of their ability to multiply simultaneously, explains Allan Barrett, a researcher at the Sealy Institute of Vaccine Sciences. The mouse model indicates that a trivalent nOPV vaccine could work in humans.
Towards Polio Eradication
These results have led to a phase I clinical trial with these new vaccines, results of which are expected to be available this year. This first study in humans will give further clues about its safety profile, immunogenicity and genetic stability. The new vaccines could be key in eliminating WPV1 and controlling cases of vaccine-derived poliovirus and cases of associated paralytic poliomyelitis.
According to the researchers, the eradication of poliovirus is achievable. Based on the success of their study, Barrett called the science behind this advancement “impressive.” While poliovirus eradication was first thought of as feasible by 2000, the initiative still proved elusive. The new vaccines developed using reverse genetics offer a promising solution to finally eradicate polio.
It is worth noting that, in the past, only two infectious diseases have been eradicated through vaccination: smallpox and rinderpest. Until gut immunity falls over time, the risk of vaccine-derived type 1 and 3 viruses will need to be controlled in high-risk or potentially even high-risk areas, warn the researchers.
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