The genetic plasticity of viruses with RNA genomes results from high mutation rates and genetic recombination, facilitating the emergence of new epidemic viral strains. We study genetic and biological aspects of these viruses from fundamental and public-health standpoints, focusing on enteroviruses.
Human enteroviruses belong to the Picornaviridae family, a large group of human and animal pathogens. They mostly cause asymptomatic intestinal infections, but they can also cause acute damage to the central nervous system leading to meningitis, encephalitis, or even flaccid paralysis, which is mostly due to infections with poliovirus (poliomyelitis) and enterovirus A71 (EV-A71).
In 1988, the WHO established a poliomyelitis eradication program based on massive vaccination campaigns with oral polio vaccine (OPV). This vaccine consists of live attenuated strains that multiply to high titers in the intestine. There is also an inactivated virus vaccine. Following this campaign, a marked decrease in the frequency of poliomyelitis (99%) due to wild-type viruses was observed worldwide. However, the disease has not yet been eradicated, due to low vaccine coverage in some areas. This low vaccine coverage is also thought to allow the emergence of pathogenic, circulating vaccine-derived polioviruses (cVDPVs). These cVDPVs have recently caused iatrogenic epidemics of paralytic poliomyelitis in several regions of the world, including Madagascar, and are subject to the same meticulous surveillance as wild poliovuruses. Most cVDPVs are recombinants between poliovirus and other non-poliovirus enteroviruses, such as coxsackie A viruses (CAV) in particular.
In parallel with the campaign to eradicate polioviruses, there has been an increase in the prevalence of other neurotropic enteroviruses, such as EV-A71. EV-A71 causes major outbreaks of hand, foot and mouth disease (a mild maculopapular syndrome) but also neurological manifestation similar to those associated with polioviruses. The largest outbreaks of EV-A71 have been seen in the Asia-Pacific region. There is currently no vaccine or treatment against EV-A71.
The research of our unit is based on studies of the mechanisms of genetic plasticity, including genetic recombination between HEVs, and the impact of genetic exchanges on viral biodiversity, emergence and pathogenicity.