Jan. 31, 2019
Three Northern Arizona University researchers were part of an interdisciplinary team that identified a polio-like virus as a potential cause of an outbreak of a disease known as acute flaccid myelitis (AFM), a crippling condition that causes muscle weakness and paralysis usually among children.
Paul Keim, Regent’s professor of biological sciences and executive director of the Pathogen and Microbiome Institute; Viacheslav (Slava) Fofanov, assistant professor in the School of Informatics, Computing, and Cyber Systems; and research coordinator Krystal Sheridan collaborated with lead researcher Dr. David Engelthaler, co-director of Translational Genomics Research Institute’s Pathogen and Microbiome Division and the study’s senior author. The researchers aimed to identify the microbial cause of the outbreak of AFM among as many as 11 patients at a Phoenix-area hospital in September 2016.
Using multiple cutting-edge genomic sequencing tests analyzing different samples, including a program Fofanov wrote, researchers identified a specific non-polio enterovirus—EV-D68—in at least four of the children, according to a study published in January in the scientific journal mBio. This finding strongly implicates the EV-D68 virus with the polio-like disease.
Above: Slava Fofanov
“As a result of this study, we developed novel EV-D68 tests that now can be used for other investigations, and for larger-scale surveillance to better understand the spread of EV-D68 and its linkage to AFM,” said Jolene Bowers, a research assistant professor at TGen North and the study’s lead author.
The study also got researchers closer to answering another question: why do some children have such severe reactions to this virus and others don’t? One hypothesis was the presence of another pathogen that exacerbated the effects of the enterovirus. Keim said the researchers did two tests: a biased test, looking specifically for EV-D68, and an unbiased test, which examined everything in each sample that had DNA to see what it was.
The first test is fairly simple. The second involves the metagenomics analysis of a massive amount of data run through NAU’s supercomputer; Fofanov designed a novel and powerful approach to run this data that wasn’t possible even a few years ago, analyzed the genomic sequence data for each sample and established the level of statistical confidence in the team’s calls.
They found no other pathogens, Keim said.
“What that does is it starts to point fingers more and more back at EV-D68 and less and less at a second pathogen we didn’t know about,” he said. “It detected what we thought might be there and it didn’t detect anything else, which narrows the bulls-eye of what’s causing the illness.”
Sheridan constructed libraries for metagenomic sequencing on different instruments, including extracting RNA and
DNA from most of the patient samples and preparing gDNA and cDNA for sequencing.
“Though the sample size was small for our study, the findings add to the growing body of research that show a link between enterovirus D68 and AFM,” Sheridan said. “It gives some direction for further inquiry and could point to a potential target for diagnostics. There is currently no specific treatment or diagnostic tool for AFM, and the disease can have severe symptoms and dire outcomes, so I hope this research helps to move the scientific and clinical communities toward further discovery.”
What is acute flaccid myelitis?
AFM is a neuromuscular disorder that involves the spinal cord and messaging signals between the brain and muscle nerve cells. Symptoms include loss of muscle reflexes in arms and legs, resulting in a polio-like paralysis, but also include face drooping and respiratory failure. There is no identified cause, no vaccine and few ways to diagnose or treat the disease. AFM remains rare, annually affecting fewer than one in 1 million children in the United States. This disease is one of many on which researchers at TGen and NAU collaborate; a recent study looked at West Nile and its presence in Arizona.