Cells infected with the Covid-19 virus can ‘explode,’ contributing to the development of severe disease, researchers have shown.
Scientists from the US and UK looked at blood samples from people infected with Covid and found that about about six per cent of monocytes — immune cells that patrol the body for foreign invaders — were undergoing a type of cell death associated with inflammation, known as pyroptosis, having been infected by the virus.
A small proportion of macrophages, another type of immune cell, which engulf and destroy foreign celluar debris, also became inflamed after being infected by Sars-CoV-2.
In the case of the two cell types, it’s believed the virus activated what are known as inflammasomes, large molecules that trigger a cascade of inflammatory responses that can culminate in cell death.
Research has long suggested that severe Covid disease is driven by inflammation, leading to lung and other organ damage.
Previous studies have shown that the immune system in people with Covid can effectively turn on the body by releasing infection-fighting proteins, known as cytokines, which then attack healthy tissue. These ‘cytokine storms’ have been associated with serious disease.
The new research, undertaken by scientists at London’s Royal Free Hospital, in conjunction with Boston Children’s Hospital, now suggests that pyroptosis also plays a role in the escalation of severe disease.
“Inflammation and cell death are both important factors in severe Covid, and our research shows pyroptosis is often the culprit,” Dr Gautam Mehta, a consultant hepatologist at the Royal Free Hospital, told The Mail On Sunday.
Dr Mehta said the pyroptosis pathway acts as an “alarm system” for the body. “If it senses bacterial or viral particles within the cell it leads to an ‘explosion’ of the cell and the release of pro-inflammatory contents.
“This has the benefit of eliminating the infection but can lead to severe inflammation as a result. Pyroptosis literally implies a ‘fiery’ mode of cell death.”
The infected immune cells could offer a potential target for drug development, scientists believe, raising hope that new treatments could be designed to prevent a person infected with Covid from falling severelly ill.
“It’s a major finding because currently our Covid treatments are geared towards the virus itself,” said Dr Mehta.
“If we can target the process that causes the severe disease, we could develop an effective treatment which works even in patients for whom the vaccines are not effective.”
A separate study, which has yet to be peer-reviewed, also showed how Sars-CoV-2 can enter immune cells – a previous point of puzzlement for scientists given these cells don’t carry many ACE2 receptors, which the virus uses to gain entry.
Scientists from Yale University School of Medicine found that the virus is capable of sneaking into human cells via another surface protein, known as as the Fcγ receptor, with the help of antibodies.