Weakened polio borrows genes to gain strength for outbreak
Genetic sleuthing has revealed how a dose of oral polio vaccine (OPV) can revert to the deadly poliovirus and cause an outbreak. The research highlights problems that global health organizations face completing their eradication of polio, and the urgency of that effort1.
"It reminds us that we need to be very careful in our development of a post-eradication policy," says Bruce Aylward, leader of the World Health Organization’s polio eradication program.
No wall of immunity
The Americas were declared free of wild poliovirus in 1999. Around this time a polio outbreak began on Hispaniola, a Caribbean island shared by the Dominican Republic and Haiti. The disease killed two children and paralysed a further 19.
From the genetic sequence of virus samples from each of these children, virologist Olen Kew at the US Centers for Disease Control and Prevention in Atlanta, Georgia, and his team have now deduced the origin of the deadly virus. "It came from a single dose of OPV given to a single [probably Haitian] child," says Kew.
Genes crucial to polio’s virulence are switched off in OPV. They had switched back on in the Hispaniola virus, the researchers found, probably through random mutation. This is hardly surprising because poliovirus "is one of the most rapidly evolving viruses we know", says Kew.
The researchers found other genes that didn’t belong to polio at all. The offending virus had borrowed genetic information from related gut pathogens called enteroviruses in the children it infected. This cut’n’paste trick may have enabled it to regain strength more quickly than it could by random mutation. "It is a great shortcut," says Mark Pallanch, a member of the CDC team.
Fortunately this kind of reversion can only happen in certain situations, says Pallanch. The situation in Hispaniola, it turns out, was perfect.
As many as 20% of children in some parts of Hispaniola had not been fully vaccinated with OPV. And wild poliovirus, which also causes immunity, had been absent from the island for many years. So there were sufficient children on the island who were susceptible enough to polio to carry and spread the virus
In Hispaniola "the process of reversion was not blocked by a wall of immunity", says Kew. OPV passed from child to child, replicating as it went. It reverted to a virulent form in about a year, the researchers estimate.
Time running out
Good vaccine coverage in most areas means that such outbreaks are rare. But two others recently in Egypt2 and the Philippines3 have raised concerns that the clock is ticking on efforts to eradicate polio globally4.
The big fear is a vaccine-derived outbreak devastating a completely susceptible child population, in the United States or Europe, which have been free of polio and OPV for decades, for instance.
To prevent this, OPV must be given to children in unvaccinated areas as quickly as possible and in a synchronized manner. The vaccine must then be withdrawn from use immediately. "The ongoing use of OPV poses a risk in itself," says Kew.
"It confirms something we already knew," says Aylward, who is concentrating on plans to phase out OPV. The recent OPV-related outbreaks have provided an idea of what to watch out for, he says. "We’ve now heightened our surveillance worldwide to catch this," he adds.
TOM CLARKE | Nature
Study suggests possible new target for treating and preventing Alzheimer's
02.12.2016 | Oregon Health & Science University
The first analysis of Ewing's sarcoma methyloma opens doors to new treatments
01.12.2016 | IDIBELL-Bellvitge Biomedical Research Institute
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy