Two common respiratory viruses can fuse to form a hybrid virus capable of evading the human immune system and infecting lung cells – the first time such viral cooperation has been observed.
The researchers believe the findings could help explain why co-infections can lead to significantly worse illness for some patients, including difficult-to-treat viral pneumonia.
Each year, around 5 million people worldwide are hospitalized with influenza A, while respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infections in children under five years of age and can cause serious illness. in some children and adults. Adults
Although coinfections, in which a person is infected with both viruses at the same time, are thought to be relatively common, it was not clear how these viruses would respond if found within the same cell.
“Respiratory viruses exist as part of a community of many viruses targeting the same region of the body, as an ecological niche,” said Dr Joanne Haney of the MRC-University of Glasgow virus research centre, who led the study. study.
“We need to understand how these infections occur within the context of each other to get a more complete picture of the biology of each individual virus.”
To investigate, Haney and colleagues deliberately infected human lung cells with both viruses and found that instead of competing with each other as other viruses are known to do, they fused to form a hybrid palm-shaped virus, with RSV forming the trunk. , and influenza leaves.
“This type of hybrid virus had never been described before,” said Professor Pablo Murcia, who supervised the research, published in Nature Microbiology. “We are talking about viruses from two completely different families that are combined with the genomes and external proteins of both viruses. It is a new type of pathogenic virus.”
Once formed, the hybrid virus was also able to infect neighboring cells, even in the presence of influenza antibodies that would normally block infection. Although the antibodies still attached to influenza proteins on the surface of the hybrid virus, the virus simply used neighboring RSV proteins to infect lung cells. Murcia said: “The flu is using hybrid viral particles as a Trojan horse.”
As well as helping viruses evade the immune system, joining forces may also allow them to access a broader range of lung cells. While influenza generally infects cells in the nose, throat, and trachea, RSV tends to prefer cells in the trachea and lungs, although there is some overlap.
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It could possibly increase the chances that influenza will trigger a serious, and sometimes fatal, lung infection called viral pneumonia, said Dr. Stephen Griffin, a virologist at the University of Leeds. Although he cautioned that more research is needed to prove hybrid viruses are involved in human disease. “RSV tends to descend further down the lung than seasonal flu virus, and the more severe the illness the further the infection descends, the more likely it is,” he said.
“It’s another reason to avoid getting infected with multiple viruses, because this [hybridisation] it is likely to happen even more if we do not take precautions to protect our health.”
Significantly, the team showed that the hybrid viruses could infect cultured layers of cells as well as individual respiratory cells. “This is important because cells are authentically glued together and virus particles will have to get in and out the right way,” Griffin said.
The next step is to confirm whether hybrid viruses can be formed in patients with co-infections and, if so, which ones. “We need to know if this is just with influenza and RSV, or is it spreading to other combinations of viruses as well,” Murcia said. “My guess is yes. And, I would guess it extends to animals. [viruses] also. This is just the beginning of what I think will be a long journey of hopefully very interesting discoveries.”
Source: news.google.com