Saturday, 6 June 2020

'Designer virus' is first new oral polio vaccine in 50 years

Phase 1 trial shows promise for completion of stalled eradication effort; offers lessons for COVID-19 vaccine development.

Virologists report promising Phase 1 clinical results for the first new oral polio vaccine in 50 years, which they have designed to be incapable of evolving the ability to cause disease in humans.

Before being halted due to the COVID-19 pandemic, a relentless vaccination campaign had nearly succeeded in eradicating polio from the world. Between 2000 and 2017, the World Health Organization (WHO) estimated that its campaign had reduced the burden of the disease by 99 percent, preventing more than 13 million children from becoming infected and risking potentially debilitating paralysis.

But in recent years, the eradication effort has been plagued by outbreaks of vaccine-derived polio -- in which the weakened virus used in oral polio vaccines evolved the ability to escape from vaccinated individuals and spread in communities with poor vaccination rates.
Now, with support from the Bill and Melinda Gates Foundation, UC San Francisco virologist Raul Andino, PhD and Andrew Macadam, PhD, of the UK's National Institute for Biological Standards and Control (NIBSC) report promising Phase 1 clinical results for the first new oral polio vaccine in 50 years, which they have designed to be incapable of evolving the ability to cause disease in humans.

In a 2017 study, Andino and colleagues discovered that in every vaccine-derived polio outbreak they studied, the virus had used the same three evolutionary steps to mutate from harmless vaccine into a regional menace.

In their new study, Andino, Macadam, and colleagues at the Gates Foundation, the Center for Vaccine Innovation and Access in Seattle, and the Centre for the Evaluation of Vaccination at the University of Antwerp have employed clever genetic wizardry based on decades of study of the poliovirus's biology to redesign the vaccine to ensure that is incapable of following this three-step pathway to re-evolve virulence. Specifically, they stabilized a region of the viral genome that is required for it to re-evolve the ability to infect humans, and ensured that the virus could not get rid of this modification even by exchanging genetic material with related viruses.


The trial found that the new designer polio vaccine was both more stable and more effective than the 50-year old Sabin vaccine from which it was derived. Specifically, the new vaccine caused participants to generate plentiful antibodies against the poliovirus, and despite shedding viral particles in their stool, those particles were unable to infect or cause paralysis in mice. In contrast, previous studies have found that when mice are exposed to viral samples shed by people vaccinated with the standard Sabin oral polio vaccine, as many as 90 percent develop paralysis.

See: Ming Te Yeh, Erika Bujaki, Patrick T. Dolan, Matthew Smith, Rahnuma Wahid, John Konz, Amy J. Weiner, Ananda S. Bandyopadhyay, Pierre Van Damme, Ilse De Coster, Hilde Revets, Andrew Macadam, Raul Andino. Engineering the Live-Attenuated Polio Vaccine to Prevent Reversion to Virulence. Cell Host & Microbe, 2020; DOI: 10.1016/j.chom.2020.04.003

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (http://www.pharmamicroresources.com/)

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