First steps to eradicate polio with a new generation of vaccines

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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. US researchers from the University of California at San Francisco and the Centers for Disease Control and Prevention in Atlanta publish in Nature the results of their work in developing vaccines that pave the way for the disappearance of the disease.

Poliovirus consists of three serotypes capable of causing poliomyelitis. Thanks to vaccines, it has been possible to eradicate wild poliovirus types 2 and 3 (WPV2 and WPV3, for its acronym in English). However, the WPV1 serotype still causes outbreaks with some frequency in Afghanistan and Pakistan. There is also concern about the circulation of strains of vaccine-derived poliovirus (VDPV) and cases of vaccine-associated paralytic poliomyelitiswhich is a rare complication of oral vaccination.

Two types of vaccines are currently used against poliomyelitis: the injectable inactivated virus (salk vaccine) and oral attenuated virus (OPV or Sabin vaccine). Among the oral vaccines, the new and recent vaccine against type 2 poliomyelitis stands out (nOPV2), which is a modified version of the monovalent oral vaccine of the same type (mOPV2).

nOPV2 is also an attenuated virus vaccine, which has shown efficacy in inducing an immune response, but is genetically more stable thanks to the modification of specific points in the genome of the vaccine strain that prevent the virus from recovering its virulence. Its development has been possible thanks to the application of the reverse geneticsan approach to vaccine development first described in 1981. This technology enables its use against vaccine-derived poliovirus variants, decreases the chances of new ones emerging, or causing vaccine-associated paralytic poliomyelitis.

Based on this approach, the team of Raul Andino (University of California) and Andrew Macadam (CDC) have designed new vaccines for serotypes WPV1 and WPV3 (nOPV1 and nOPV3). The authors used the genetic sequence of nOPV2 and incorporated genes encoding components of the protein coat structure of the OPV1 and OVP2 vaccine virus.

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