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Orthonairoviruses, a family of tick-borne pathogens, can bypass human immune defenses using specialized proteins called ovarian tumor domain proteases (OTUs), according to a study led by University of California, Riverside (UCR). This mechanism allows viruses like the Crimean-Congo hemorrhagic fever virus to suppress the body’s ability to detect and fight infection, increasing pandemic risk.
How Orthonairoviruses Disable the Human Immune Response
The research, published in ACS Infectious Diseases, identifies how viral OTUs interfere with cellular communication. Normally, human cells rely on small proteins known as ubiquitin and ISG15 to regulate and trigger immune responses. Scott Pegan, a professor of biomedical sciences at the UCR School of Medicine, explains that OTUs remove these molecular signals.
By stripping away these signals, the virus effectively disarms the immune system at multiple stages. This process makes it significantly easier for an infection to take hold within the host. Pegan noted that the study also revealed a third, previously uncharacterized function of these proteins that contributes to immune evasion, though its specific role remains unknown.
Did you know? Orthonairoviruses include the Crimean-Congo hemorrhagic fever virus, which is known to cause severe hemorrhagic disease in humans.
The Threat of the Pacific Coast Tick in the U.S.
While some orthonairoviruses are known globally, the U.S. faces specific risks from the Pacific Coast tick. This species already transmits several dangerous pathogens, including those causing Pacific Coast tick fever and Rocky Mountain spotted fever. Previous research has identified a nairovirus specifically associated with these ticks.
Pegan states that the mechanism used by the Pacific Coast tick orthonairovirus to suppress immunity is “highly compatible with humans.” Because the tick already bites people, Pegan suggests the virus could be circulating among the human population undetected.
The study was a collaborative effort involving UCR researchers—including Adam Godzik, Lukasz Jaroszewski, and David S. Gonzalez—and Éric Bergeron from the Viral Special Pathogens Branch of the Centers for Disease Control and Prevention (CDC). Funding was provided by the National Institute of General Medical Sciences and the National Institute of Allergy and Infectious Diseases.
Pandemic Potential and Future Surveillance
The ability of these viruses to evolve and bypass human immune defenses underscores a significant pandemic potential for the Nairoviridae family. According to Pegan, the rapid identification of human-infecting orthonairoviruses is critical for global health security.
Future research must determine if these viruses are currently infecting humans and causing disease within the geographic range of the Pacific Coast tick. This data is essential for developing new diagnostics, surveillance tools, and medical countermeasures.
Comparing Tick-Borne Risks
Not all tick-borne pathogens operate the same way. While some cause bacterial infections like Rocky Mountain spotted fever, orthonairoviruses use complex protein manipulation (OTUs) to hide from the immune system. This makes them harder for the body to fight naturally compared to simpler pathogens.
Frequently Asked Questions
What are orthonairoviruses?
They are a family of viruses transmitted by ticks, some of which cause severe diseases like Crimean-Congo hemorrhagic fever.
How do these viruses evade the immune system?
They use ovarian tumor domain proteases (OTUs) to remove ubiquitin and ISG15 proteins, which the body needs to signal an infection.
Is there a risk of a pandemic?
According to Professor Scott Pegan, the ability of these viruses to evolve and bypass human defenses indicates a significant pandemic potential.
Which tick is of concern in the United States?
The Pacific Coast tick is a primary concern due to its ability to transmit various bacterial and viral pathogens to humans.
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