A few years ago, a new foe took the world by storm. A coronavirus spread throughout the world, causing a new disease known as COVID-19, with unknown long-term consequences. Scientists from King’s College in London have analyzed the gastrointestinal (GI) tracts of people with a wide spectrum of COVID-19 related deaths. They hypothesized a star player in our gut’s immunity could be compromised by COVID-19 infections.
The scientists focused on a type of tissue found in the GI tract, called lymphoid tissue. These gut-residing lymphoid tissues are the link between our gut and immune system, and play a key role in keeping us healthy and thriving. The gut is also home to a plethora of bacteria inhabiting this tissue. These bacteria play important roles in digestion, and help to fend off other, more harmful bacteria.
Specific types of lymphoid tissue found in the gut, called Peyer’s patches, regulate the growth and kinds of bacteria in the gut, helping to maintain a healthy gut microbiome. The UK researchers wanted to determine if Peyer’s patches were affected by COVID-19 in the gut. The team performed genetic testing to determine the presence or absence of COVID-19 in the gut of patients whose deaths were related to the infection.
The scientists first extracted genetic material from samples of gut tissue. They used molecular methods to amplify and detect any DNA matching the COVID-19 virus in the samples. Then they stained and imaged COVID-19-positive gut tissues and COVID-19-negative control specimens to determine how a COVID-19 infected GI tract looked different from one without infection.
The researchers interpreted their images to reveal irregularities in one of the critical parts of Peyer’s patches. The ‘control center’ of production for the immune system’s antivirals is known as the germinal center. This rounded structure houses these antivirals, called antibodies, which are replicated and mobilized to fight infection when a virus is detected.
A normal germinal center supports a healthy and consistent gut microbiome, but when normal immune processes fail, harmful bacteria can take over. The UK scientists found the germinal center in gut samples with COVID-19 was often misshapen, shrunken, or underdeveloped.
In fact, the researchers found that Peyer’s patch tissues were similarly damaged or interfered with in samples from patients with COVID-19, whether or not the virus was actually identified in the gut tissues. Their finding goes hand in hand with symptoms reported during COVID-19 infection, where a small percentage of people infected also reported GI issues.
The human gut serves as one of the biggest players for our immune system. It sifts through the myriad of harmful substances and organisms we encounter through the things we eat and drink. These researchers concluded the depletion of germinal centers by COVID-19 could inhibit the body’s ability to mount an immune response in the gut, thus affecting the entire immune system. They suggested ex-COVID patients could experience frequent ‘stomach bugs,’ or potentially chronic GI ailments in the long run.
Scientists have not extensively studied the recovery of Peyer’s patch and their germinal centers. The UK team suggested further research focusing on how to regenerate lymphoid tissues in the gut could potentially help to mitigate and control the long-term effects of COVID-19.