Researchers in Sweden have developed tiny vesicles that reduced damage to brain cells in mice infected with bacteria that cause meningitis. 

Bacterial meningitis affects the protective lining of the brain and spinal cord and is commonly caused by Streptococcus pneumoniae infection. Although antibiotics kill the bacteria, the infection can still cause long-term neurological damage. One contributor is pneumolysin, a toxin released by the bacteria that can damage neurones and trigger harmful inflammation. 

Researchers from EARA member Karolinska Institutet developed different types of extracellular vesicles, small particles naturally produced by cells that traverse the cell membrane, and tested them in laboratory-grown human neurones and immune cells, as well as in mice infected with S. pneumoniae. The vesicles captured pneumolysin and reduced damage to neurones and inflammatory signals in both cells and mice. When given through the bloodstream, they reached the brains of infected mice, delayed the development of severe disease and increased survival compared with untreated mice. 

The treatment did not reduce the amount of bacteria in the brain or elsewhere in the body, indicating that the benefit came from limiting toxin-related damage and inflammation rather than killing the bacteria.  

“Our results suggest that the extracellular vesicles act as decoys, capturing pneumolysin before the toxin can reach and damage neurones. Importantly, the same biomaterial also acts as a suppressor of severe and harmful inflammation,” said Federico Iovino from the Karolinska Institutet and senior author of the study published in the Journal of Extracellular Vesicles. 

The researchers are now testing the treatment alongside antibiotics to evaluate whether the combination can kill the bacteria while reducing toxin-related neurological damage.