[ad_1]
Scientists now have perhaps an answer to one of the most crucial questions about COVID-19: whether people develop long-term immunity.
An early wave of research has suggested that antibodies to coronavirus – blood proteins that protect the body against subsequent infections – can wear off within months. But in their concern about the implications of these findings, many people failed to take into account our immune system’s multi-layered defense against invading pathogens.
Specifically, they ruled out the role of white blood cells, which have impressive memory powers that can help your body mount another coronavirus attack if it returns. Memory T cells are a particularly key type, as they identify and destroy infected cells and instruct B cells on how to make new antibodies targeting the virus.
A study published in the journal Cell on Friday suggests that anyone who contracts COVID-19 – even people with mild or asymptomatic cases – will develop T cells capable of tracking down the coronavirus if exposed again later.
“Memory T cells are likely to be essential for long-term immune protection against COVID-19,” the study authors wrote, adding that they “could prevent recurrent episodes of severe COVID-19.”
This is because memory T cells can stick around for years, while antibody levels drop after infection.
Even patients without antibodies have virus-specific T cells
A human T lymphocyte (also called a T cell) from the immune system of a healthy donor.
NIAID
The authors of the new study examined the blood of 206 people in Sweden with COVID-19 with varying degrees of severity. They found that regardless of whether a person recovered from a mild or severe case, they still developed a robust T-cell response. Even coronavirus patients who did not test positive at all for the antibodies developed memory T cells, the results showed.
Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, called the T cell studies “good news.”
“There’s a lot of hot stuff right now” in T cell research, Fauci said in a NIAID Facebook Live interview on Thursday, adding: “People who don’t appear to have high titers of antibodies, but who are infected, or have been infected, have good T cell responses. “
Dr Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases.
Mandel Ngan / AFP via Getty Images
Other recent research reinforces the new findings.
A study published in July found that in a group of 36 recovered coronavirus patients, all produced memory T cells that recognize and are specifically designed to fight the novel coronavirus. Another recent study published in the journal Nature found that among 18 German patients with coronavirus, more than 80% developed virus-specific T cells.
Even people who have never been exposed to the novel coronavirus can have protective T cells
These two previous studies also resulted in a second, more surprising finding: Many people who have never had COVID-19 appear to have memory T cells capable of recognizing the new coronavirus.
This was true for more than half of a cohort of 37 people in the July study and at least a third of a group of 68 patients in the Nature study.
Clinicians are taking blood samples to test for antibodies to the coronavirus in a recovered COVID-19 patient.
REUTERS / Shannon Stapleton
The most likely explanation for these findings is a phenomenon called cross-reactivity: when T cells developed in response to another virus react to a similar, but previously unknown pathogen. In this case, experts believe these cross-reactive T cells are likely from previous exposure to other coronaviruses – the ones that cause the common cold.
Indeed, a study published earlier this month supports this hypothesis: Researchers reported that 25 people who had never had COVID-19 had memory T cells capable of recognizing both the novel coronavirus and the four types of common cold coronavirus.
“This could help explain why some people have milder disease symptoms while others get seriously ill,” said Alessandro Sette, co-author of this study, in a press release.
“You start off with a small advantage – a head start in the arms race between the virus that wants to reproduce and the immune system that wants to eliminate it,” Sette told Business Insider.
We still don’t know exactly how long this long-term immunity lasts.
Blood samples in vials are tested for anti-coronavirus antibodies at Keele University in the UK, June 30, 2020.
REUTERS / Carl Recine
While this news about T cells and coronavirus immunity is promising, scientists are still unsure how long people who recover from COVID-19 will be protected from future infection.
The authors of the new study said they detected T cells “months after infection, even in the absence of detectable circulating antibodies.”
Other preliminary research, published on Saturday, suggests that T cells not only last for at least three months after the onset of symptoms of the coronavirus, but in some cases increase in numbers during that time.
Additionally, clues gleaned from other coronaviruses, such as SARS, suggest that the lifespan of T cells could last for decades.
The July study also looked for T cells in blood samples from 23 people who survived SARS. Indeed, these survivors still had SARS-specific memory T cells 17 years after falling ill. These same T cells could also recognize the new coronavirus.
[ad_2]
Source link