Studies since the start of the pandemic have indicated that pigs can become infected with the COVID-19 virus if exposed to high doses. But the infection is self-limited and the pigs do not show clinical signs of disease or transmit the virus to other animals.
COVID-19 and pigs: could lead to new ways of treating humans
So Rahul Nelli, research assistant professor of veterinary diagnostics and production animal medicine at Iowa State University. As well as Luis Gimenez-Lirola, associate professor of veterinary diagnostics and production animal medicine. They set out to find out why in a new study in CellDeath.
What they found could lead to new ways to treat humans who contract COVID-19. The disease that results from infection with the SARS-CoV-2 virus, the researchers say.
Nelli and Gimenez-Lirola have studied how COVID-19 affects pigs for years. They have developed models that allow them to study in detail how viruses infect pigs and pig cells and how cells respond to fight infection. For the latest experiments, they introduced the virus into cultured human and porcine respiratory epithelial cells. Which cover most of the respiratory tract.
They found that pig cells underwent apoptosis, or controlled cell death, in response to infection at a higher rate than human epithelial cells.
“When we looked under the microscope, there was an interesting phenomenon inside the cells,” says Nelli. “The nuclei of the infected pig cells were beginning to fragment, but not the uninfected pig cells.”
Pig cells are about 100 times more likely to undergo apoptosis
That nucleus shredding is a telltale sign of apoptosis, which may be key to helping pigs avoid symptoms after exposure to SARS-CoV-2. Activating apoptosis in the early stages of infection essentially causes minimal tissue damage and limits viral replication. What limits serious disease.
According to the study, pig cells are about 100 times more likely to undergo apoptosis than human cells.
Human cells are more likely to undergo necrosis, another form of cell death less controlled than apoptosis. During necrosis, the contents of a cell are released into the surrounding space, causing a strong hyperimmune response that is not triggered during apoptosis.
Further study could lead to therapies designed to trigger apoptosis in human cells
The researchers hypothesize that a large-scale apoptotic response is helpful in staving off disease because it kills infected cells quickly without overreacting to the immune system, whereas large-scale necrosis and the resulting hyperimmune response are less favorable for cells. Guest.
“We don’t want to conclude too much, but this response is probably something intrinsic to the pig’s immune system that is innate and not acquired,” says Giminez-Lirola. “The idea is to kill the virus subtly but quickly enough that an excessive immune response is not triggered.”
The researchers say that further study could lead to therapies designed to trigger apoptosis in human cells. Which would allow people infected with the coronavirus to avoid severe symptoms.
The researchers’ next step is to identify all the genes activated during the infectious process and compare them with other animal species in which those genes are present. That could give them more clues about how and why other animals, such as deer, can carry the virus without suffering symptoms of illness.
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