Could immunity last 17 YEARS? Singaporean researchers discover that SARS patients still have crucial T cells
Hope for long-term Covid-19 immunity was sparked today after scientists discovered that SARS patients still have crucial disease-fighting cells.
SARS – another type of coronavirus very similar to the type that causes Covid-19 – was behind an epidemic that mainly affected Asia in 2003. No cases have been identified for 15 years.
But some infected during the outbreak still have important white T cells, suggesting they would be protected from ever becoming infected again.
Research by scientists in Singapore offers hope that the same is true for SARS-CoV-2 – the name of the coronavirus behind the pandemic.
With some viruses, such as chickenpox, protection is lifelong and it is not possible to get sick again. But others, like the common cold, are short-lived.
Experts are still baffled at how long the immunity to Covid-19 lasts, since it only existed since December 2019. Antibody studies have suggested that it may only provide short-lived immunity like other coronaviruses.
But T cells – which cannot be detected by the ‘have you had it’ antibody tests – created in response to the infection, can provide a form of immunity that lasts several times longer.
Other scientific studies have shown that people who have had a cold in the past two years have T cells that show ‘cross-reactive protection’ against Covid-19.
Singaporean researchers have found that patients with SARS have immunity for up to 17 years. It gives hope that the same could be true of the closely related coronavirus causing the current global pandemic called SARS-2. Depicted, an illustration of a coronavirus attacked by immune cells
The study led by Duke-NUS Medical School in Singapore, published in the scientific journal Nature yesterday, involved 23 SARS patients.
They collected blood samples and tested whether they still contain immune cells that were effective against SARS.
All patients had T cells, suggesting that they are an important part of fighting this infection.
T cells are a type of white blood cells that are an important part of the immune system and help fight disease.
WHAT ARE T-CELLS?
When the body is invaded by bacteria, a virus, such as SARS-CoV-2, or parasites, an immune alarm is triggered, triggering a chain reaction of cellular activity in the immune system.
T lymphocytes (T cells) are white blood cells that are an important part of the immune system.
They are part of the adaptive immune system, which is considered to be the more specialized response. They use past interactions to remember foreign threats and how to attack them.
The adaptive immune system takes effect after the innate immune system, the direct response to a virus or ‘first line of defense’.
There are different types of T cells, some of which do not understand their functions.
Killer T cells directly kill cells already infected by a foreign invader, while T helper cells stimulate other parts of the immune response, such as B cells.
B cells are also part of the adaptive immune system. They help make antibodies specific to each pathogen.
Antibodies can block the new coronavirus by attaching to it and marking it for destruction by other immune cells.
“Killer T cells” fight a pathogen, while “helper T cells” signal that action is being taken in other parts of the immune system when they see that a cell has been invaded.
Research has shown that all patients still have long-term memory T cells that are reactive to the virus.
The findings “support the idea that Covid-19 patients will develop long-term T cell immunity,” the researchers wrote.
This can be important for vaccine research, as it helps scientists understand how long a vaccine would protect a person before a booster shot is needed.
In further experiments, the scientists mixed blood samples with fragments of SARS-CoV-2 to see what happened.
The cells showed ‘robust’ reactivity to SARS-2 in all patients by connecting them.
To further investigate the subject of immunity, 37 volunteers were recruited who had never been infected with SARS-1 or SARS-2.
They wanted to see if infection with other human coronaviruses that have been around for centuries offered some form of protection against Covid-19.
The researchers found 50 percent (19) of the participants found ‘notable’ levels of T cells that could attach to the Covid-19 virus.
“Surprisingly, we also often discovered SARS-CoV-2 specific T cells in individuals with no history of SARS, Covid-19 or contact with SARS / Covid-19 patients,” the authors wrote.
They believe that these T cells may exist as a result of a previous infection with another coronavirus – seven of which can infect humans.
It could not be excluded that the T cells came from other animal coronaviruses – which are believed to come from bats – rather than human coronaviruses.
Principal investigator Dr. Antonio Bertoletti said The Telegraph these T cells may be more common in Asia than in the rest of the world.
He did not explain why, but he may have referred to the fact that zoonoses – those that jump from animals to humans – have emerged more often in Asia.
It could explain why the continent remained relatively unscathed compared to Europe and the US during the Covid-19 pandemic.
The team said that strong immunity to closely related viruses can reduce the susceptibility or serious illness associated with SARS-2.
But it is not certain whether these T cells would protect someone if they were exposed to Covid-19.
Either way, the researchers said this ‘pre-existing’ population-scale protection should be considered, as it could mean fewer people are at risk of getting sick with Covid-19 than thought.
Scientists at the La Jolla Institute for Immunology in California have also previously said that it is “ tempting to speculate ” that a cold can provide some form of immunity.
They found blood samples from people donated in 2015-2018, contained T cells that recognized and responded to SARS-Cov-2, and published their findings in the journal Cell.
Researchers at the La Jolla Institute for Immunology in California analyzed blood samples from recovered COVID-19 patients (left) and frozen blood samples from people two years ago. They found that both had T cells that recognize SARS-CoV-2 and some that can kill it
T cells have become an increasingly debated topic during the Covid-19 pandemic, once eclipsed by interest in antibodies.
T cells are part of adaptive immunity, the first line of defense against a foreign substance. On the other hand, antibodies activated by B cells don’t start to help until a few days later.
They may not be needed if T cells and other parts of the immune system have already wiped out the virus.
For that reason, some people may not have antibodies to Covid-19 in their blood, despite having been infected with the coronavirus in the past, scientists say.
The Singaporean team said their previous research found that antibodies to SARS-1 were undetectable after two or three years.
Therefore, antibody tests would suggest that they can be reinfected, when in fact protected by T cells.
In terms of SARS-2, Professor Karol Sikora, a World Health Organization advisor, previously told MailOnline that he believes that only 10 percent of people infected with the coronavirus develop antibodies.
The Karolinska Institutet and Karolinska University Hospital, in Sweden, have recently shown that many people with mild or asymptomatic Covid-19 T cell immunity to the disease and do not test positive for antibodies.
The research suggests that immunity among the population is higher than the testing of antibodies.
Some parts of the immune response remain a complete mystery to scientists and cannot be measured.