UC Riverside study reveals how tick-borne viruses evade human immunity

UC Riverside study reveals how tick-borne viruses evade human immunity

A study led by a biomedical scientist at the University of California, Riverside (UCR) has uncovered the mechanisms used by a family of tick-borne viruses known as orthonairoviruses to bypass human immune defenses. The research, published in ACS Infectious Diseases, identifies how these pathogens disarm the body's ability to detect and fight infection, signaling a potential pandemic risk associated with the Nairoviridae family.

The research focused on specialized viral proteins called ovarian tumor domain proteases, or OTUs. Under normal conditions, human cells utilize small proteins—specifically ISG15 and ubiquitin—to regulate immune responses. However, the study found that viral OTUs can remove these molecular signals, effectively blunting the body's defenses.

"The virus uses these proteins to disarm the body's immune defenses at multiple stages, making it easier for the infection to take hold,"

Scott Pegan, professor of biomedical sciences in the UCR School of Medicine, via miragenews.com

Pegan noted that the study also revealed a third function of these proteins that contributes to immune evasion, though its specific function remains unknown. The findings are particularly concerning because the mechanisms used by the Pacific Coast tick orthonairovirus to suppress immunity are highly compatible with humans, according to Pegan.

The Pacific Coast tick is already known to transmit several viral and bacterial pathogens, including Pacific Coast tick fever and Rocky Mountain spotted fever. Pegan warned that because this virus is carried by a species that already infects people, it may be circulating undetected. He emphasized the need for further research to determine if the virus is currently infecting humans within the tick's geographic range.

The Growing Threat of Tick-Borne Illnesses

The UCR research arrives as other tick-borne threats are seeing an unprecedented surge in the United States. The Powassan virus, a rare and potentially fatal illness, has reached historic highs. According to data from the Centers for Disease Control and Prevention (CDC), 76 Americans were diagnosed with the virus in 2025, the highest annual total on record. This is a sharp increase from the historical U.S. Average of seven to eight diagnoses per year.

Powassan virus is primarily spread by the deer tick (also known as the blacklegged tick) and the woodchuck tick. It is most prevalent from late spring through mid-fall. Experts highlight the virus's rapid transmission speed as a primary danger. While Lyme disease typically requires a 36- to 48-hour attachment time for transmission, Powassan can be transmitted in as little as 15 minutes.

The virus follows a dangerous clinical path:

• Incubation: A silent period of one to four weeks.
• Initial Symptoms: Fever, headache, vomiting, and weakness.
• Severe Complications: The virus can attack the nervous system, leading to meningitis (spinal cord membrane inflammation) and encephalitis (brain inflammation).
• Critical Symptoms: Seizures, loss of coordination, difficulty speaking, and severe confusion.

The mortality rate for symptomatic cases of Powassan virus is reported between 10% and 15%.

Environmental and Clinical Challenges

The rise of these illnesses is linked to broader environmental shifts. Climate change has resulted in warmer winters and longer springs and autumns, extending the period during which ticks are active. Milder winters have also boosted populations of rodents and deer, which serve as reproductive hosts. In parts of Eastern Massachusetts, deer density has reached levels where management is considered functionally impossible, while Martha's Vineyard and Nantucket have estimates of more than 100 deer per square mile.

Medical professionals have struggled to keep pace with these emerging threats. Some doctors report a lack of awareness regarding the Powassan virus, leading to delayed diagnoses and confusion with other conditions like strokes. Furthermore, there are currently no specific vaccines or medications to treat or prevent the Powassan virus; medical care is limited to supportive therapy, such as respiratory support and intravenous fluids.

While a replacement Lyme disease vaccine is nearing availability after Pfizer and Valneva completed phase 3 clinical trials in March, other tick-borne threats remain without pharmaceutical countermeasures. In May, Health and Human Services Secretary Robert F. Kennedy Jr. Announced new funds for control and

Pegan and other health experts urge the public to remain vigilant, noting that different tick species carry different diseases that may not be routinely monitored.