New lab experiments are shedding light on how the Ebola virus can survive unnoticed in the body for months or even years after initial infection, with the potential to trigger a relapse.
Infectious Ebola virus has been detected in semen for months or even a year after infection, and it can also persist in the central nervous system, particularly the brain, researchers explain in discussing their study published in Nature Microbiology.
That’s because testicles – the source of semen – and the central nervous system are considered to be “immune-privileged,” meaning the immune system reacts in a weakened and controlled manner in these areas in order to protect sensitive tissue. As a result, it cannot always eliminate the virus completely.
To learn more, researchers programmed human stem cells to grow into so-called cerebral organoids, spherical brain-like structures consisting of central nervous system cells.
The Ebola virus infected multiple cell types in the cerebral organoids and could replicate for up to 120 days, they found.
The virus was able to spread in the cerebral organoids in two ways: directly from an infected cell to a neighboring cell, and by budding from the host cell, which is the classical way the virus spreads.
“These cerebral organoids enable us to investigate in detail the mechanisms that Ebola virus and other filoviruses use to persist in the human central nervous system,” study leader Lina Widerspick of the Bundeswehr Institute of Microbiology in Munich said in a statement.
“Through experiments in this model system, we can gain insights that help us improve our understanding of the long-term effects of persistence, like the severe and sometimes fatal inflammation seen in Ebola virus disease survivors with meningoencephalitis.”
Studying the infected organoids, the researchers discovered genome mutations that may be helping the virus to lurk undetected, including some mutations that had not previously been described in Ebola survivors.
They called for further studies, particularly into less well understood strains, such as the Bundibugyo virus causing the current outbreak in Africa.