Since the pandemic’s beginning, studies have shown that pigs may be infected by the virus if exposed to large doses. Still, the infection is self-limiting, and the pigs do not display clinical indications of sickness or transfer the virus to other animals.
In a new study published in the academic journal Cell Death Discovery, Rahul Nelli, a research assistant professor of veterinary diagnostic and production animal medicine, and Luis Gimenez-Lirola, an associate professor of veterinary diagnostic and production animal medicine, set out to find out why.
According to Nelli and Gimenez-Lirola, these findings might lead to novel treatments for patients who get COVID-19, an illness caused by infection with the virus SARS-CoV-2.
Nelli and Gimenez-Lirola have spent years researching how coronaviruses impact pigs.
They’ve created models that enable them to investigate how viruses infect pigs and pig cells and how the cells react to the infection.
In the most recent trials, the virus was delivered to cultured porcine and human respiratory epithelial cells, which line most of the respiratory system.
They discovered that pig cells had a greater rate of apoptosis, or regulated cell death, in response to infection than human epithelial cells.
“When we looked under the microscope, there was an interesting phenomenon going on inside the cells. The nuclei of the infected pig cells were starting to shred into fragments but not uninfected pig cells.”
The shredding of the nucleus is a clear marker of apoptosis, which may be essential in preventing SARS-CoV-2 symptoms in pigs.
Early in the infection, inducing apoptosis produces minor tissue damage and limits viral reproduction, preventing severe sickness.
According to the research, human cells may also experience apoptosis in response to coronavirus infection, albeit considerably less often than swine cells.
According to the research, pig cells are 100 times more likely than human cells to suffer apoptosis.
Researchers Trying to Shift to Pigs’ Immune System to Escape Severe Symptoms
Human cells are more prone to undergo necrosis, a less regulated type of cell death than apoptosis.
The contents of a cell are released into the surrounding space during necrosis, eliciting a robust hyperimmune response that is not elicited during apoptosis.
The researchers believe that a wide-scale apoptotic response is beneficial for disease prevention because it eliminates contaminated cells fast without causing the immune system to overreact. Still, wide-scale necrosis and the ensuing hyperimmune reaction are less beneficial to host cells.
Giminez-Lirola stated it’s too early to want to jump to conclusions, but this reaction is presumably fundamental to the pig immune system, innate rather than acquired. The goal is to destroy the virus quietly yet quickly enough that an excessive immune reaction is not activated.
According to the researchers, future research might lead to medicines that induce apoptosis in human cells, enabling those infected with the coronavirus to escape severe symptoms.
The ISU research team’s next step will be to identify all of the active genes throughout the infectious process and compare them to other animal species that have those genes.
This might provide them with more information about how and why other species, such as deer, can carry the virus without showing indications of sickness.
In addition to Nelli and Gimenez-Lirola, the study team at Iowa State includes Kruttika Phadke, Gino Castillo, Lu Yen, and Bryan Bellaire.
In Maryland, Amy Saunders, Rolf Rauh, and William Nelson of Tetracore, Inc. are also cited as co-authors on the paper.
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