An international team led by researchers at the University of Toronto has found a new RNA virus that they believe binds to a common human parasite.
The virus, called Apocryptovirus odysseus, along with 18 others that are closely related to it, was discovered through a computational screen of human neuron data, an effort aimed at elucidating the connection between RNA viruses and neuroinflammatory diseases. The virus is associated with severe inflammation in humans infected with the parasite. Toxoplasma gondiileading the team to hypothesize that it exacerbates the disease of toxoplasmosis.
“We discovered A. odysseus in human neurons using the Serratus open science platform to search more than 150,000 RNA viruses,” said Purav Gupta, first author of the study, a recent high school graduate and current undergraduate at the Donnelly Center for Cellular and Biomolecular Research at the U of T. “Serratus identifies RNA viruses from public data by tagging an enzyme called RNA-dependent RNA polymerase, which facilitates viral RNA replication. “This enzyme allows the virus to reproduce and the infection to spread.”
The study was recently published in the journal Virus Evolution.
The parasite T. gondii It has a wide reach and is estimated to infect a third of the world’s population. It can live in any type of non-blood cell, including neurons, forming cysts within the cells. The parasite is transmitted to nearby cells when the infected cell ruptures.
T. gondii Infections often go undetected because they only cause symptoms in rare cases. Still, toxoplasmosis deserves investigation considering its extent and the potential effects it can have on pregnant women and immunocompromised people, Gupta said.
“We believe that the virus and the parasite work hand in hand to cause disease in the human host, where the virus hides inside the parasite, like a soldier on a Trojan horse, to enter the human brain,” Gupta said. “Our research marks the first time scientists have linked toxoplasmosis to a virus.”
the newly discovered A. odysseus It is found in two hypervirulent strains of the T. gondii parasite, called RUB and COUGAR.
In French Guinea, RUB has been documented to cause severe fever and organ failure, while in British Columbia, COUGAR has been shown to be linked to ocular toxoplasmosis, the leading cause of infectious blindness. The researchers found the strains in different geographic locations and at different times, demonstrating their potentially wide-ranging impacts.
The symptoms of toxoplasmosis can be aggravated by an overactivated human immune response. The parasite carrying the virus triggers this type of response when the immune system detects the virus’s foreign RNA.
“The group of 19 RNA viruses we found are strong biomarkers of parasitic infection,” said Artem Babaian, principal investigator of the study and assistant professor of molecular genetics at the Donnelly Center and Temerty School of Medicine. “It is obvious now that the A. odysseus The virus could be a valuable marker for infections that cause disease, such as severe toxoplasmosis, in humans or other animals. “The next step is to test whether this raises the possibility that treating a parasite’s viruses could be an effective means of treating symptoms arising from parasitic infections.”
Zoonotic viruses that infect other living things in our environment to reach us are expected to cause most emerging infectious diseases in humans, Babaian said. “This study underscores the importance of looking beyond viruses that infect humans directly to the widespread virome,” she said.
This research was supported by the Canadian Institutes of Health Research.