The antibodies we create after being infected with or vaccinated against a virus can be very potent. Typically, a virus spreads through our body by entering a cell and using it as a factory to create copies of itself, which then explode and find new cells to infect. Our antibodies work by binding to the virus and this can prevent them from binding to the cells and not entering our cells.
But what if a virus doesn’t need to leave the cell to spread to neighbors cells? Can our antibodies be effective against it?
Scientists recently asked this question for SARS-CoV-2, which causes COVID-19. This highly infectious coronavirus can change human cells, causing them to merge with two or more nearby cells. These supercells, with large fused cells, are excellent viral factories.
Supercells, known as syncytia, share multiple nuclei (the part of the cell that contains the genetic material) and an abundant cytoplasm (the gelatinous substance that surrounds the nucleus). Having more of these components in a giant cell helps the virus reproduce more efficiently. And by merging cells, SARS-CoV-2 increases its resources without being exposed to neutralizing antibodies that move outside our cells.
The study by Alex Sigal and colleagues tested two variants of coronavirus (alpha and beta) to determine their cell-to-cell transmission capacity and investigated whether this mode of transmission was sensitive to the neutralization of antibodies. The alpha variant (first identified in the UK) is sensitive to antibodies and the beta variant (first identified in South Africa) is less sensitive to these antibodies.
The Sigal study, which has not yet been published in a scientific journal, revealed that cell-to-cell transmission with both variants successfully evaded antibody neutralization. This shows that when the virus takes over, it will be more difficult to eliminate them in cells that can fuse together.
We have just published a new article in bioRxiv that shows that once cells are infected with SARS-CoV-2, they can infect other cells in ways that are very difficult to inhibit with antibodies.https://t.co/JtTbbwtidR
– Alex Sigal (@sigallab) June 2, 2021
Viruses have coexisted with humans and animals for millennia, so they have developed tricks to prevent ours from recognizing them. immune system. This immune evasion strategy is the direct cell-to-cell transmission, which does not always require cell fusion.
It is also possible for viruses to travel to nearby host cells by exploiting close associations between neighboring cells that protect them from antibodies. It is reasonable to assume that antibodies are more effective in preventing entry into the host cell and less effective in parts of the body where it is found. infection it is already established.
Does this mean that our vaccines will be ineffective against viruses that move directly from cell to cell? Luckily, our immune system has also evolved alongside viruses, and we’ve learned that build defenses which work in many ways.
It’s not the only line of defense
T cells are white blood cells that, after vaccination or infection, are trained to recognize and kill infected cells. They do not rely on recognizing the floating virus, so cell-to-cell transmission does not reduce their ability to search for and destroy viral factories. Like cells capable of producing antibodies, T cells can remember a previous infection and act quickly when the same virus reappears.
It is not advisable to put all the eggs in one basket, which is why vaccines induce both antibodies and virus-specific T cells. Antibodies bind to viruses before they enter our cells or after the release of new viruses after infection. T cells act to reduce fertile cell hosts for virus replication, until infection is eliminated. Many other cells (without immune memory) also work together to completely eradicate the virus from the body.
What happens to those of us who may have older or dysfunctional parts of our immune system? Coronavirus infection is usually controlled within two weeks in most healthy young adults and children. In people with dysfunctional T cell responses, cell-to-cell transmission could hinder neutralizing antibodies and thus prolong the infection. Persistent infection increases the chances of viruses to mutate and better adapt their life cycle to our body, leading to the potential appearance of variants of concern.
We don’t have to worry about cell-to-cell transmission disabling our vaccines, but it’s important to understand how a virus spreads so we can target it more effectively. A few years ago my classmates and I showed up that the hepatitis C virus transmits from cell to cell in the presence of neutralizers antibodies. This has not stopped scientists from developing antivirals with as much success as they can heal people who had been infected with hepatitis C for decades.
With effective vaccines and antivirals, we can try to eradicate viruses that do not integrate their genome with ours (such as SARS-CoV-2) from human populations as we have done. before. Extensive resistance to infection in humans achieved through vaccination if all work together means that if the same virus jumping back from animal guests, his transmission journey to people would be very short. The latest technologies that allow vaccines to be updated quickly can ensure effective control against emerging variants.
Citation: Coronavirus variants can bypass antibodies by spreading through supercells (2021, June 10) retrieved June 10, 2021 at https://medicalxpress.com/news/2021-06-coronavirus-variants-evade -antibodies-supercells.html
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