As the new Corona virus mutates and evolves, so must the arsenal to fight it. To this end, the National Institutes of Health has begun testing booster doses in order to attack a new type of COVID-19 virus. The strain known as B.1.351 was discovered in South Africa and is of greater concern because, like other variants, it appears to spread more easily than the original virus. Recent research also indicates that it is able to circumvent the protection of the immune system resulting from vaccines or when the Corona virus is contracted naturally.
In an effort to stay on the cutting edge of the virus, the National Institute of Allergy and Infectious Diseases (NIAID) is working closely with the Massachusetts-based company, to test a modified version of its vaccine. The immune system is improved by genetic instructions that cause the immune system to recognize and attack the South African species. This first stage is a study, Which includes 210 healthy adults, will show whether the booster dose is safe and effective.
“The mutations are located in a very specific location, on the surface of the viral protein, which means that some antibodies do not” see “the protein,” explains John Mascula, director of the NIAID Vaccine Research Center. “These studies are being conducted to clarify whether the booster vaccine will provoke a broader immune response.”
Moderna’s potential new booster vaccine differs from the currently approved vaccine. Instead of stimulating the production of the spike protein that was present in the original strain of Sars-CoV-2, it directs the production of a spike protein that includes the mutations in the B.1.351 strain. Thus, the immune system recognizes a preview of the South African variant.
Like Moderna and the National Institutes of Health, Pfizer and BioNTech are exploring the possibility of creating vaccines against specific variants. But they also have a second strategy in mind: Simply implement A third dose From the original vaccine, already authorized by the FDA, the U.S. Food and Drug Administration. The hypothesis is that an additional dose could generate a greater secretion of antibodies to fight the new strains.
Booster doses are part of a more comprehensive strategy to mitigate the effect of mutant strains. Last February, The Biden government has appropriated $ 200 million To intensify monitoring and fund an early warning system that will send Sars-CoV-2 samples across the country, in order to better identify and track new variants. This initiative will be coordinated by the interagency group for Sars-CoV-2, within the Department of Health and Human Services. The aim of the project is to monitor and characterizeVariables of interest“Which pose greater threats because it is more contagious and deadly and is able to circumvent the body’s protective mechanisms.
Monitor development in real time
The sheer scale of the pandemic, which remains out of control, means that the virus has billions of hosts and, accordingly, trillions of opportunities to replicate and mutate.
In theory, this could generate an infinite variety of variants, some of which provide a selective advantage to the virus, making it nearly impossible to neutralize it, as in the case of the featured card game. And now it looks like there are many different releases coming, not only in the UK, South Africa, Brazil and India, but also In the states of California, Oregon and New York.
Most of the variants are not a cause for concern because their mutations are unique copies that disappear because they do not have an advantage for the virus. Public health officials only show their concerns if the strain is more contagious, makes us sicker, or allows the virus to penetrate the immune system. Unfortunately, the variants currently being traded in the United States have these factors.
“What we’re seeing is the virus evolving very quickly and in real time,” says Gregory Poland, an infectious disease specialist and director of the Vaccine Research Group at Mayo Clinic in Rochester, Minnesota. “Most of the mutations make the virus less suitable for survival and infection. But natural selection will favor mutations that are beneficial to the virus.”
Strain B.1.1.7For example, which was first discovered in December 2020 and devastated the United Kingdom, is very severe More contagious and deadly than the original virus. Now it is spreading rapidly across Europe and could become the dominant strain in the United States. The South African dynastyWhich appeared in October and have already been discovered, at least 25 statesAnd the And to p. 1, The variant that wiped out Brazil and arrived in the United States in January 2021 could re-infect people who have already been infected with the COVID-19 virus or have been vaccinated, because these are The variants contain a mutation That allow them to defeat the antibodies our immune system releases to defend against invaders.
Scientists call changes that allow viruses to bypass the arrival of antibodies from them Escape from the boom. It occurs when the virus is under pressure of natural selection. Viruses that can continue to infect cells and reproduce are those that have properties that allow them to escape antibodies. Now, the scientists who study mutations are Most worried about the E484K call, Who believe they are the main culprits behind the virus evasive maneuvers.
This mutation changes the shape of the spiky protein that graces the surface of the coronavirus. This virus typically uses a spike to bind to and enter receptors on the surface of human cells. The current vaccine arsenal stimulates the production of antibodies that bind to the native spike protein and prevent it from entering the human cell – just as sticking gum with a key prevents it from entering the lock and unlocking the door.
But there are still many unknown factors. For example, scientists still do not know how fast the SARS-CoV-2 virus is mutating. This is important because every time a mutation occurs, it can reduce the effectiveness of authorized vaccines that fight COVID-19 efficiently.
This situation is completely different from the measles virus. When it is mutated, the new strain remains Be cant To escape vaccine-neutralizing antibodies. That is why we do not need a booster dose every year, or change the vaccine formulation. “The measles vaccine was introduced in 1963 and we still use the same vaccine today,” says Cody Messner, director of the Department of Children’s Infectious Diseases at Tufts Children’s Hospital in Boston. But if we look at the influenza virus, we find that there are new strains that require new vaccines every year. We do not know where the Covid-19 virus will be with respect to these two extremes. This is the reason why all these different types of methods are investigated. We just don’t know. “
Convergent evolution is good news
although Initial studies It can give the impression that the world will always be one step behind this virus, recent research indicates that the news is not so bad. There is increasing evidence that more dangerous variants have certain common characteristics or mutations. For example, the South African variant, the Brazilian strain P.1 and the strain B.1.1.7 that afflicted Europe has the E484K mutation.
This is actually a good thing. Scientists call this phenomenon Convergent twist, Which happens when The same mutation arises independently With the passage of time in different regions In the world because it is an adaptation that aids in virus transmission and reproduction. “If we analyze the mutation that gives the virus more capacity, we can see it in the South African and Brazilian variants,” explains Alessandro Set, an immunologist at La Jolla Immunology Institute. “This is important, because at two different times and on two different continents, the bad variant has the same mutation. In other words, the virus has little bad repertoire.”
This limited amount of tricks suggests that mastering vaccines with new genetic instructions that encode specific mutations can have an effect against many dangerous variants simultaneously.
although Vaccine-induced antibodies They may not completely deviate from the South African variant, the vaccine is not a waste. In clinical trials in South Africa, where the variable is prevalent, although the vaccine is less effective in preventing infection, It was 100% effective in preventing deaths and hospitalizations. This is because the number of neutralizing antibodies stimulated by the vaccines was sufficient to compensate for the loss of efficacy. “The protection is still there,” says Seet. “It is not effective in warding off the virus.”
Saved by T cells?
As concern about the variants grows, it is imperative to remember that vaccines and antibodies are not the only form of defense. Individuals who are already infected or have been fully vaccinated have another ally if they become infected again with the virus or a new variant. The immune system’s so-called “killer” T cells could play a role if the virus leaves the antibodies overloaded. T cells help recognize and destroy affected cells. “If protection is violated and the virus enters the cell, the killer T cells are important for controlling and eliminating the infection,” Seet explains.
In a study published in MarchResearchers from the National Institute of Health analyzed blood cell samples from 30 people who had recovered from Covid-19 before the variants appeared. When a T cell type from these samples was exposed to the variant, the T cells were detected Get to know CD8 + all of them, Including the South African variant. “The regions in which T cells attack are not affected by mutations in the new variants,” says Andrew Reed, a scientist at the NIAID Immunoregulation Laboratory. In the vast majority of cases, he says, the T-cell response should prevent the disease, even if the virus manages to bypass the equivalent antibody.
The National Institutes of Health expects to complete inclusion in the booster tests by the end End of April. As the Food and Drug Administration clarified that it will grant emergency approval for vaccines designed to combat variants, a new immune system can be rapidly developed. However, despite all the good news, we must be on alert. “We are still in the early stages, and if people are tired of contracting the virus for economic or political reasons, it will be like pouring gas on a fire,” says Gerald Bolland of the Mayo Clinic. “We could be at the start of an exponential spread of a highly contagious variant. Nobody can predict what will happen next week.”
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