Ebola virus disease (EVD) is a multisystemic human disease associated with an exceptionally high mortality rate. In survivors, inflammation can recur in tissues where the immune system is shielded or tightly regulated, such as the central nervous system. The viruses persist in the body. This persistence occurs through continuous replication of the Ebola virus genome beyond the acute phase of the disease, which can lead to the production of infectious viral particles outside of host cells. The persistence is associated with recurrent outbreaks of Ebola virus disease.

The research team wanted to investigate how the virus survives in its host over the long term. They developed brain organoids from human induced pluripotent stem cells (hiPSCs) that contained various types of brain cells (neurons, astrocytes, microglia, oligodendrocytes). The organoids were cultured for over 100 days and then infected with the Ebola virus for at least 120 days. For comparison, additional infections with other viruses (e.g., Lassa virus, LASV) were conducted, and various cell lines (Vero E6, Huh7, SH-SY5Y neuroblastoma cells) were also used. All samples were analyzed using molecular biology, immunohistochemistry, and electron microscopy, among other methods.

The team observed that the Ebola virus (EBOV) was able to establish a productive, long-lasting infection in human cerebral organoids (derived from induced pluripotent stem cells) for at least 120 days. Other filoviruses (Sudan, Marburg, and Reston viruses) were also capable of doing so, but the Lassa virus was not. The Ebola virus continuously infected astrocytes and neurons. It also recruited and infected microglia within the organoid. Oligodendrocytes were also infected. The infection spread from the periphery toward the center of the organoid. During the ongoing infection, genetic defects and subvariants of the virus also emerged. To spread, the virus utilized both the process of viral ejection and direct cell-to-cell transmission. 

Cell-specific innate immune responses occurred, particularly in the microglia. Astrocytes exhibited a weaker immune response despite the infection. The persistent infection led to late-onset, localized inflammation in the brain model.

According to a recent press release, organoids offer a unique opportunity to study the phenomenon in a human context rather than in an animal model. This could help reevaluate and optimize treatments such as antiviral drugs and, furthermore, open up avenues for reducing the use of animal models in infection research in the future.

Original publication:
Widerspick, L., Vidal Freire, S., Steffen, J.F. et al. Host–virus determinants of Ebola virus persistence in a human cerebral organoid model. Nat Microbiol (2026). https://doi.org/10.1038/s41564-026-02388-2

Further information:
https://www.bnitm.de/aktuelles/news/versteck-im-zentralen-nervensystem-mit-hirnorganoiden-die-biologie-des-ebola-virus-besser-verstehen