Circulating Vaccine-Derived Poliovirus type 2 (cVDPV2) caused outbreaks in several African countries after OPV2 removal from routine schedules in 2016. India uses novel OPV2 (nOPV2) in outbreak response since 2021. Which property of nOPV2 distinguishes it from the classical Sabin type 2 strain?
- A nOPV2 contains attenuating mutations that are genetically stabilized, reducing reversion to neurovirulence ✓
- B nOPV2 is an inactivated preparation and cannot replicate in the gut
- C nOPV2 does not stimulate intestinal mucosal immunity and relies entirely on systemic IgG
- D nOPV2 is a subunit vaccine containing only VP1 capsid protein of type 2 poliovirus
Explanation
Novel OPV2 (nOPV2) was developed specifically to address the problem of cVDPV2 outbreaks arising from the classical Sabin 2 strain, which reverts relatively easily to neurovirulence under immune pressure. nOPV2 retains the live attenuated nature (enabling intestinal replication and mucosal IgA generation), but its key attenuating mutations are stabilized using engineered genetic modifications (modified IRES domain, stabilized domain V of the 5'UTR), making reversion to neurovirulence far less likely. It is not inactivated, not a subunit vaccine, and does stimulate mucosal immunity.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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