This is the latest in a series of studies that uncover multiple facets of the complicated immune system reaction that can weigh the balance between good and bad results.
October 1, 2020 Share on FacebookShare Share on TwitterTweet Share on WhatsAppShare
A doctor observes a patient in the Intensive Care Unit at the Emilio Ribas hospital in Sao Paulo (Brazil). EFE / Sebastiao Moreira / Archive
One of the most chilling mysteries of COVID-19 is why some people experience moderate symptoms or no symptoms while others die quickly , and scientists are beginning to unravel it.
An international team of scientists found that, in some people with severe manifestations of COVID-19, the body attacks one of its own immune defenses rather than the coronavirus. The majority were men, which helps explain why the virus is affecting men more severely than women.
And another study indicates that children respond much better than adults to infection, thanks to “first responder” immune cells whose presence diminishes with age.
It is the latest in a series of studies that uncover multiple facets of the complicated immune system reaction that can weigh the balance between good and bad . The next thing is to determine if these new leads offer ways to intervene.
“We have the knowledge and the ability to really strengthen many aspects of the immune system. But we should not use a mallet, ”warned Dr. Betsy Herold of the Albert Einstein School of Medicine in New York, a co-author of the study with children.
In general, children who are infected with the new coronavirus show less severe symptoms than adults. EFE / Peter Foley / Archive
Adding to the complexity is the fact that the varying degrees of reactions in people also reflect other factors, such as how healthy they were prior to infection and how much virus they were exposed to.
” Infection and what happens after infection is very dynamic, ” said Alessandro Sette, a scientist at the La Jolla Institute of Immunology in San Diego, who studies another part of the immune response.
IMMEDIATE IMMEDIATE DEFENSE
The immune system has two main units. Innate immunity is the body's first line of defense. As soon as the body detects an intruder, important molecules like interferons and cytokines – the latter causing inflammation – launch a large-scale attack.
Innate immune cells also alert the slowest “adaptive” unit of the immune system, germ-specific snipers, to be ready. B cells begin to produce antibodies to fight a virus, proteins that get a lot of attention in the search for a vaccine.
However, antibodies are not everything. Other elements of adaptive immunity are the “killer” T cells that destroy cells infected with the virus, and the “memory” T and B cells that remember an infection to act more quickly in case of re-encountering the virus. same germ.
Queues for PCR tests in a health center. EFE / Enric Fontcuberta / Archive
Typically, when a virus invades a cell, proteins called Type 1 interferons come into play, defending the cell by interfering with viral growth. But new studies show that those crucial molecules were basically absent in people with severe manifestations of COVID-19.
An international project discovered two reasons. In the blood of nearly 1,000 patients with severe COVID-19 cases, the researchers found that 1 in 10 had what are known as autoantibodies – antibodies that mistakenly attack those who fight the virus . Particularly surprising was that 95% of these COVID-19 patients were men, even though autoimmune diseases are more common in women.
The scientists did not find the harmful molecules in patients with mild manifestations of COVID-19 or in asymptomatic patients.
In another 660 seriously ill patients, the same team found that 3.5% had genetic mutations that did not produce Type 1 interferons.
Each of those silent vulnerabilities was enough to tip the balance in favor of the virus in the early part of the infection, said Dr. Jean-Laurent Casanova, an infectious disease geneticist at Rockefeller University in New York , who co-directs COVID Human Genetic. Effort. The specialist is paid by the Howard Hughes Medical Institute, which also helps fund The Associated Press Department of Health and Science.
Certain interferons are used as medications and are currently being studied as a possible treatment for COVID-19. The discovery of the autoantibody adds another factor to consider.
The highest frequency is in Bangladesh, where an estimated 63% of the population carries at least one specimen of the Neanderthal risk haplotype. EFE / EPA / MONIRUL ALAM / Archive
ACCELERATED CHILD IMMUNITY
The reason why children appear to be less at risk from COVID-19 is unknown . However, they occasionally get sick enough to be hospitalized, giving Herold's team the opportunity to compare 60 adults and 65 children and adolescents in New York's Montefiore Health System.
Children produced much higher levels of certain cytokines that are among the first elements of the innate immune system to respond to infection . When the next phase of the immune system is activated, both adults and children created antibodies that attacked the coronavirus. Here's the problem: The adaptive immune reaction in adults was more of the type that can trigger an excessive inflammatory reaction.
The findings suggest that the energetic initial reaction of minors allows their immune system to get ahead of the virus, reducing the possibility of an overreaction “and that is what protects them,” Herold said.
The coronavirus that causes COVID-19 is new to humans. However, Sette's team studied blood samples that were stored in refrigerators before the pandemic and found that they contained some memory T cells that recognized a small portion of the new virus in laboratory tests.
“ You can tell that it is an experienced T cell. He's already been in combat , ”Sette said. Researchers in Germany, Great Britain, and other countries made similar findings.
The new coronavirus has cousins that cause up to 30% of ordinary colds, so researchers believe these T cells could be remnants of previous colds.
However, despite speculation, “we still don't know” that having these T cells makes any difference to who gets seriously ill with COVID-19 , said Rory de Vries, co-author of a study in the Netherlands that also found such T cells in old blood samples.
File image of medical personnel treating a patient suffering from COVID-19, the disease caused by the coronavirus, in the Intensive Care Unit (ICU) of Scripps Mercy Hospital in Chula Vista, California, United States. May 12, 2020. REUTERS / Lucy Nicholson / Archive
All of these findings require a deeper understanding of the myriad ways some people are more susceptible than others.
” We need to observe widely and not rush to conclusions about any particular facet of the immune system ,” said Stanford University immunologist Bali Pulendran. He also found some innate immune cells “in a state of hibernation” in seriously ill adults and is looking for differences before and after people became ill.
But “it's not just about the immune system, ” said Dr. Anita McElroy, an expert in viral immunity at the University of Pittsburgh, who is closely following the research. A way to tell in advance who is most at risk? “We are still very, very far from that.”
With information from AP