How human cells slow down the Ebola virus

The Ebola virus can cause severe, often life-threatening disease in humans. To replicate, it must enter human cells and exploit their cellular processes. In doing so, it encounters natural defense mechanisms that can make infection more difficult.

A research team led by Professor Michael Schindler from the Institute of Medical Virology and Epidemiology of Viral Diseases at Tübingen University Hospital has now investigated one such protective mechanism. The study also involved researchers from the Friedrich Loeffler Institute and the Bernhard Nocht Institute for Tropical Medicine.

CD81 Inhibits Viral Replication

The researchers set out to investigate how the Ebola virus alters the surface of human cells. They analyzed 332 cell surface proteins and identified CD81 as one of the proteins of particular interest. CD81 belongs to a family of proteins known as tetraspanins, which are involved in various processes at the cell membrane.

Further experiments showed that CD81 can interfere with Ebola virus replication. To investigate this, the research team used virus-like particles that mimic key stages of Ebola virus infection. When CD81 was absent from the cells studied, certain steps of viral replication were enhanced. Conversely, increasing the amount of CD81 inhibited these processes. CD81 also restricted the entry of virus-like particles into cells.

Two Viral Proteins Counteract CD81

The study also reveals how the Ebola virus interferes with this cellular defense mechanism. Both the viral surface glycoprotein GP and the matrix protein VP40 reduce the amount of CD81 in the cells studied and on their surface.

“What we found particularly exciting was that not just one, but two viral proteins act against CD81, even though the Ebola virus only has in total seven proteins. This suggests that this cellular defense mechanism poses a serious obstacle for the virus,” explains Elena Hagelauer, who shares first authorship of the study with Dan Hu. Both are researchers at Tübingen University Hospital.

The team also investigated how CD81 affects signaling pathways within the cell. They found evidence that CD81 influences a signaling pathway activated by the viral protein VP40. This pathway is involved, among other things, in inflammatory responses, which play an important role in severe cases of Ebola. This effect may contribute to the observed inhibition of viral replication.

Antibody Reduces Infection in Cell Cultures

In another experiment, the researchers investigated whether CD81 could be specifically targeted. An antibody that binds to CD81 reduced infection with authentic Ebola virus in cell culture experiments. The team also observed changes in CD81 levels during infection with authentic Ebola virus, including in human immune cells.

These findings provide initial evidence that CD81 may also play an inhibitory role during infection with authentic Ebola virus. However, the underlying mechanisms require further investigation, and it remains unclear whether these findings could lead to a treatment.

“Our results show that human cells possess a CD81-mediated protective mechanism that the Ebola virus must overcome. If we gain a better understanding of how this mechanism works, it could lead to a new therapeutic approach for treating Ebola infections,” says study leader Professor Michael Schindler.