Major breakthrough in our understanding of tick-borne virus encephalitis

In a landmark study, scientists have unearthed a mechanism by which a dangerous virus enters brain cells to cause encephalitis.

Introduction

Tick-borne encephalitis virus (TBEV) has been spreading in Europe and Asia in recent years, causing life-threatening encephalitis. A new study by an international team of researchers has identified a key protein that the virus uses to invade cells. This work, published in September in the prestigious journal Nature, may lead to new ways to prevent and treat this serious condition.

The discovery

Researchers have identified LRP8 (also called ApoER2) as a cell receptor that TBEV uses to enter cells. LRP8 stands for low-density lipoprotein receptor-related protein 8 and is highly expressed in the brain.

Using a powerful tool known as CRISPR gene-editing, the team found that cells that lacked LRP8 were less susceptible to TBEV infection. The discovery of an interaction between LRP8 and TBEV now helps to explain why this virus specifically targets the central nervous system (CNS).

Significantly, this is also the first identification of a host protein acting as a receptor for a flavivirus, a family of viruses which includes the encephalitis-causing viruses Japanese encephalitis virus, West Nile virus, and dengue virus.

What is tick-borne encephalitis?

Tick-borne encephalitis (TBE) is a viral infection that is primarily transmitted through tick bites. It can also spread through unpasteurised dairy products from infected animals.

“Most people infected with Tick-borne encephalitis virus show no symptoms at all” says Chief Executive of Encephalitis International, Dr Ava Easton. “In those that do have symptoms (2-30%), they typically appear about one to two weeks after the tick-bite. From those, around one-third will develop neurological symptoms indicating a more serious illness. Some people will recover completely. Others may have long lasting problems such as paralysis, difficulties with walking and coordination, head pain, fatigue, and cognitive problems such as thinking and memory problems.”

Conclusion

This breakthrough opens up several new avenues for research. First and foremost, it helps scientists develop specific antiviral treatments for TBE. Development of prevention strategies alongside vaccination will also be informed. Importantly, the successful use of gene editing methods in this study fuels hope for similar research on other types of viral encephalitis.

While this important work springs promise for future development of treatments for TBE, the best protection against the condition remains vaccination. This is especially important for travellers or those who spend time outdoors. “If walking in affected wooded or rural areas,” advises Dr Easton, “it is recommended to wear long trousers/sleeves to cover exposed skin, use an insect repellent that is effective against ticks, and inspect your skin for ticks regularly, removing them as quickly as possible if found.”

• For more information on tick-borne encephalitis, read our factsheet here.
• To view a video overview of tick-borne encephalitis by Professor Michael Haditsch click here.
• For information on prevention and vaccination, visit our website encephalitis.info/encephalitis-guidelines-for-travellers.