Study finds viral infections could promote neurodegeneration

Some viral diseases could possibly contribute to neurodegeneration, according to new research published in the journal Nature Communications.

The study is based on laboratory experiments in which they were able to show that certain viral molecules facilitate intercellular spreading of protein aggregates that are hallmarks of brain diseases like Alzheimer’s disease.

Aggregates of misfolded proteins, which occur in so-called prion diseases such as Creutzfeldt-Jakob disease, can pass from one cell to another, where they transfer their abnormal shape to proteins of the same kind. As a result, the disease spreads across the brain. A similar phenomenon is discussed for Alzheimer’s and Parkinson’s disease, which also exhibit assemblies of misfolded proteins. Transmission of aggregates could involve direct cell-to-cell contact, the release of “naked” aggregates into extracellular space or packaging in vesicles, which are tiny bubbles surrounded by a lipid envelope that are secreted for communication between cells, the researchers said.

For the study, researchers performed an extensive series of studies with different cell cultures. Thereby, they investigated the intercellular transfer of either prions or aggregates of tau proteins, as they occur in similar form in prion diseases or Alzheimer’s disease and other “tauopathies”. Mimicking what happens because of viral infection, the researchers induced cells to produce viral proteins that mediate target cell binding and membrane fusion. Two proteins were chosen as prime examples: SARS-CoV-2 spike protein S, which stems from the virus causing COVID-19, and vesicular stomatitis virus glycoprotein VSV-G, which occurs in a pathogen that infects cattle and other animals. Moreover, cells expressed receptors for these viral proteins, namely the LDL receptor family, which act as docking ports for VSV-G, and human ACE2, the receptor for the spike protein.

The findings may provide clues how acute or chronic viral infections could contribute to neurodegeneration, the researchers said.