Bat Organoids Reveal Key to Their Resilience Against Deadly Viruses

Bats are natural reservoirs for several highly pathogenic viruses, including coronaviruses related to Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS), as well as Marburg and Nipah viruses. Unlike humans, who often suffer severe symptoms upon infection, bats typically remain asymptomatic. To investigate this phenomenon, an international team led by the Helmholtz Centre for Infection Research (HZI) in Germany has developed an innovative organoid-based research platform, revealing the antiviral defense mechanisms of bat mucosal tissues. The findings were published in Nature Immunology.

Focusing on the Egyptian fruit bat—a natural host of the Marburg virus—the researchers cultivated organoids from respiratory and intestinal tissues to model how viruses invade mucosal barriers. Due to the challenges of studying live bats, organoids serve as an ideal alternative. In a Biosafety Level 4 (BSL-4) facility, the team compared the response of bat and human airway organoids to Marburg virus infection. Remarkably, bat cells exhibited stronger baseline antiviral activity even before infection occurred.

Further analysis revealed that bat mucosal epithelial cells possess a highly efficient innate immune system, particularly with regard to interferon responses. Type III interferons play a pivotal role: upon infection, bat organoids rapidly produce large quantities of these interferons, maintaining long-term protection through a self-amplifying mechanism. Gene editing experiments confirmed that disruption of this interferon system significantly reduced antiviral defense. This mechanism allows bats to suppress viral replication early, while delayed responses in human cells contribute to uncontrolled viral spread.

This study not only highlights the unique adaptability of the bat immune system but also offers valuable insights for preparing against future viral threats.