Researchers still know very little about how Coronavirus infects the lungs. After all, it’s hard to study the impact of a disease on a person while you’re scrambling to save their life. To work around this, scientists at Cambridge used donated tissue to grow “mini-lungs” in three dimensions to track the impact of SARS-CoV-2 on organs. The timeline they uncovered is shocking.
Tissue of a strain of Coronavirus was taken from a South Korean patient who was infected in Wuhan, China. The lab-grown 3D models (“mini-lungs”) were exposed to the infected tissue. Scientists then used fluorescence imaging and single cell genetic analysis to study the damage to the lung tissue as the virus progressed.
The virus replication accelerated rapidly, reaching full cellular infection in only six hours after the initial infection. This rapid expansion allows the virus to move quickly throughout the body, infecting cells and other tissue, and helps explain why the virus spreads so easily from host to host.
Almost immediately after full cellular infection, cells began producing interferons, the proteins that warn other cells of the infection. Within 48 yours, interferons had triggered a full immune response and cells began fighting back against the COVID-19 infection.
Although the body’s response to the virus seem timely, the virus’ simply outpaces the body’s abilities. Just 12 hours after the immune response, only 60 hours into the infection, the virus had already begun causing the disintegration of alveolar cells leading to the death of lung tissue.
In less than 3 days after the initial infection, the virus had already begun destroying lung tissue. However, clinical symptoms of COVID-19 can take more than 10 days after exposure to appear. This allows the virus a full 7+ days to wreck unencumbered havoc before the infected person even knows something is wrong. This gives the virus more than enough time to cause severe damage to a person’s lungs before treatment can begin.
The study has been published in journal Cell Stem Cell. Jeonghwan Youk et al. Three-dimensional human alveolar stem cell culture models reveal infection response to SARS-CoV-2. Cell Stem Cell; 21 Oct 2020; DOI: 10.1016/j.stem.2020.10.004