Immune proteins are also easier to measure than T cells and can be used to assess a previous infection.
Antibodies have become a household word in the era of the pandemic, perhaps suggesting they are the best hope in keeping the deadly coronavirus at bay. But when crucial vaccine data emerged this week, the spotlight turned to an unrecognized immune player: T cells.
AstraZeneca Plc, Pfizer Inc. and its partner BioNTech SE, as well as CanSino Biologics Inc. in China, all hailed the presence of these white blood cells in vaccine recipients as a sign that their experimental shots are promising.
Developed by recent studies, T cells serve as a reminder that the body’s defenses rely on more than one weapon, and much of the immune response to Covid-19 is still a mystery – especially after researchers have revealed that the most praised antibodies are lacking. holding power.
“Antibodies are only a very small part of the picture,” said Paul Griffin, associate professor of medicine at the University of Queensland in Brisbane, who is leading clinical studies in Australia on two potential vaccines against Covid-19. But “we’re really not there yet to fully understand” people’s immunity to the novel coronavirus.
As the pandemic took the world by storm, scientists initially focused on antibodies – proteins that stick to and neutralize foreign invaders – because obtaining them is the basis of most effective vaccines. Immune proteins are also easier to measure than T cells and can be used to assess a previous infection.
The study showing that they decline rapidly in patients with mild illness has hurt hopes that the antibodies would provide a lasting form of immunity.
Unsung warriors
T cells, on the other hand, are able to kill cells infected with the virus, remember diseases of the past for decades, and awaken new antibody soldiers long after the first have left the battlefield. People infected with another coronavirus that caused the SARS outbreak in 2003, for example, still have a T-cell response to the disease 17 years later.
This suggests that T cells could still, at least hypothetically, be ready to protect SARS survivors from infection almost two decades later, and could strengthen their defense against Covid-19, Griffin said. “They might have a slightly milder or shorter duration in terms of their disease progression, but I certainly don’t think that would be protective, unfortunately,” he said.
A study found that some patients with no symptoms of Covid-19 had T lymphocytes that recognized the virus – even when they did not have detectable antibodies. Another pointed to a level of immunity in people who have never encountered the pathogen, possibly due to exposure to one or more of the coronaviruses that cause the common cold.
Balancing Act
More research is needed to determine whether pre-existing T cells that cross-react with the SARS-CoV-2 virus may explain why some Covid patients are barely affected while others get very sick and even die. What is clear is that a balance of antibodies and T cells is necessary for optimal defense, according to Griffin.
Corey Smith, head of translational and human immunology at QIMR Berghofer Medical Research Institute in Brisbane, says the short-lived findings of antibodies do not mean that immunity wanes completely, precisely because of T cells.
So-called helper T cells, as well as memory T and B cells are able to prime antibodies to respond to subsequent infection before it causes severe symptoms, said Smith, who studies the immune response to the virus. SARS-CoV-2.
The virus, like other coronaviruses that cause the common cold, may have a way of evading antibodies, leading to reinfection, Smith said. “But cellular immunity is sufficient to alleviate severe symptoms.”
So T cells are what ultimately subdue and blunt the pandemic virus that has killed over 600,000 people in less than seven months.
“If we can’t eradicate it, does it end up becoming some kind of circulating virus, another cold virus?” Smith said. “I’m not sure, but it’s interesting.”
(This story was not edited by GalacticGaming staff and is auto-generated from a syndicated feed.)
