An international team of researchers has identified the specific protein that tick-borne encephalitis virus (TBEV) uses to infect human cells, marking a significant breakthrough in understanding how the virus causes neurological disease. The study, co-led by scientists from Albert Einstein College of Medicine, Karolinska Institutet, and the United States Army Medical Research Institute of Infectious Diseases (USAMRIID), was published on September 24, 2025 in the journal Nature. This discovery represents the first time researchers have conclusively identified an essential host-cell protein receptor for any flavivirus.

TBEV belongs to the flavivirus genus, which includes other serious mosquito- and tick-borne pathogens such as dengue virus, yellow fever virus, Zika virus, and Japanese encephalitis virus. Until now, scientists had been unable to identify the critical protein receptors that these viruses use to enter human cells. "By conclusively demonstrating that TBEV requires a critical protein receptor to infect human cells, we open the field to discovering receptors for other flaviviruses and devising therapies for the devastating infections they cause," said study co-leader Kartik Chandran, Ph.D., professor of microbiology & immunology at Einstein.

The research team identified LRP8 as the crucial protein that acts as a receptor for TBEV infection. Using a sophisticated screening method, researchers exposed thousands of cell variants with different genes removed to TBEV and found that cells lacking the LRP8 gene survived exposure. "LRP8 is a protein on the cell surface that is highly expressed in brain cells," explained Sara Gredmark Russ, Associate Professor of Infectious Diseases at Karolinska Institutet, who led the study at KI. The protein essentially functions as a "door opener" for the virus to enter human cells.

This discovery has significant implications for developing new treatments for tick-borne encephalitis, a disease that currently has no specific antiviral therapies available despite the existence of a preventive vaccine. TBEV is transmitted through tick bites and can infect the brain and spinal cord, causing severe and sometimes life-threatening neurological disease. With the virus endemic throughout Northern, Central and Eastern Europe, and Central and East Asia, and cases expected to increase due to climate change and expanding tick habitats, this breakthrough provides a crucial foundation for future antiviral drug development.

Finnair is gradually restoring its Airbus A321 fleet to service after an uncertified cleaning procedure forced the grounding of eight aircraft. The airline confirmed that seat covers were washed with water, a method not properly certified to ensure fire protection standards were maintained. This safety concern prompted the removal of the affected aircraft from service, leading to operational disruptions across Finnair's European network.

The situation began improving over the weekend as Finnair started installing new seat covers on the grounded aircraft. The first A321 returned to service on Sunday, operating a flight from Helsinki to Rhodes. However, seven aircraft remain out of service with no confirmed timeline for their full return. The A321s typically seat approximately 200 passengers and are crucial for Finnair's European route operations.

The grounding has resulted in significant passenger disruptions, with Finnair implementing extensive rebooking procedures. On Sunday alone, approximately 460 passengers were moved to different flights due to aircraft downgrades. The airline has prioritized high-frequency routes such as Helsinki-Stockholm and Helsinki-London, ensuring alternative options are available. In some cases, Finnair has used smaller replacement aircraft and offered incentives for volunteers to switch flights.

To manage the capacity shortfall, Finnair has wet-leased two aircraft with crews from Danish carrier DAT since Wednesday. While flight cancellations have decreased to single digits in recent days, with some days passing without any cancellations, the airline acknowledges that irregularities may continue through the coming week. Finnair is providing accommodation and compensation to affected passengers in accordance with EU air passenger rights regulations as it works to fully resolve the operational challenges.