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The researchers have shown that the new coronavirus can infect and multiply in cells of the human intestine, a finding that may explain why many COVID-19 patients experience gastrointestinal symptoms such as diarrhea.
Scientists, including those from the Hubrecht Institute in the Netherlands, successfully propagated the new coronavirus, SARS-CoV-2, in cell culture models of the human intestine, and monitored the cells’ response to the virus.
They said the findings, published in the journal Science, could explain the observation that nearly a third of COVID-19 patients experience symptoms such as diarrhea, and the fact that the virus can often be detected in stool samples.
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COVID-19 patients show a variety of symptoms associated with the respiratory organs, including cough, sneezing, shortness of breath, and fever, and the disease is transmitted through tiny droplets that are spread mainly through coughing and sneezing. .
However, a third of patients also experience gastrointestinal symptoms, such as nausea and diarrhea, the researchers said.
Long after respiratory symptoms have resolved, the virus can be detected in human feces, they added, suggesting that SARS-CoV-2 may also be spread through so-called “fecal-oral transmission.”
Although the respiratory and gastrointestinal organs appear very different, the study noted some key similarities.
One observation, he said, is the presence of the ACE2 receptor through which the SARS-CoV-2 virus can enter cells.
The researchers said that the interior of the intestine is loaded with these receptors.
Until now, they said it was not known whether intestinal cells could become infected and produce virus particles.
So scientists tried to grow the viruses in human gut organoids, which are small versions of the human gut that can be grown in the laboratory.
“These organoids contain cells from the human intestinal lining, making them a compelling model for investigating SARS-CoV-2 infection,” said study co-author Hans Clevers of the Hubrecht Institute.
When the virus was added to the organoids, the cells quickly became infected, the study noted.
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According to scientists, the virus entered a subset of cells in the intestinal organoids, and the number of infected cells increased over time.
Using electron microscopy, an advanced way to visualize different components of the cell in great detail, the researchers found virus particles inside and outside the organoid cells.
“Due to the blockade, we all studied virtual slides of the infected organoids remotely from home,” said Peter Peters, co-author of the study at the University of Maastricht in the Netherlands.
By evaluating the organoid’s response to the virus, the researchers found that genes stimulated by the immune system’s chemical messenger, interferons, were activated in these cells.
They said that these genes are known to fight viral infection.
The researchers believe that future work focusing on these genes more carefully may help understand how they might be used to develop new treatments.
When the scientists cultured the organoids under different conditions, resulting in cells with higher and lower levels of the ACE2 receptor, they discovered that the cells infected with the virus had both high and low levels of the ACE2 receptor.
The study, the scientists said, may lead to new ways to block the virus from entering our cells.
They also believe that the findings may provide a new cell culture model for the COVID-19 study.
“The observations made in this study provide definitive evidence that SARS-CoV-2 can multiply in cells of the gastrointestinal tract. However, we do not yet know whether SARS-CoV-2, present in the intestines of patients with COVID-19 plays an important role in the transmission, “said Bart Haagmans, another co-author of the study.
“Our findings indicate that we should take a closer look at this possibility,” added Haagmans.
According to the study, special care may be needed for patients with gastrointestinal symptoms.
The researchers said that more extensive testing may be needed using not only nose and throat swabs, but also rectal swabs or stool samples.
In other studies, scientists said they hope to understand the differences between infections in the lung and intestine by comparing the intestinal and pulmonary organoids infected with SARS-CoV-2.
