As the number of people who have fought off SARS-CoV-2 climbs ever higher, a serious question has grown in importance: How long will their immunity to the novel Coronavirus last? A new Rockefeller study offers an encouraging answer, suggesting that those who recover from COVID-19 are protected against the virus for at least six months and likely much longer.
The findings, published in Nature, provide the strongest evidence yet that the immune system “remembers” the virus and remarked, continue to improve the quality of antibodies produced months after the infection showed increased ability to block SARS-CoV-2 as well as its mutated version such as the South African Variant.
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The researchers found that these improved antibiotics are produced by immune cells that have kept evolving apparently due to continued exposure to the remnants of the virus hidden in the gut tissue.
Based on these findings, researchers suspect that when the recovered patient next encounter the virus, the response would be both faster and more effective preventing re-infection to occur.
“This is really an exciting news, the type of immune response we see here could potentially provide protection for quite some time by allowing the body to mount a rapid and effective response to the virus upon re-exposure,“ says professionals and head of the laboratory of molecular immunology whose team has been tracking and identifying antibody responses in COVID- 19 patient since the onset of the pandemic.
Long-lasting memory
The antibody which the body creates in response to infection lingers in the blood plasma for several weeks or months but their levels significantly drop with time.
The immune system has a more efficient way of developing with pathogens instead of producing antibodies all the time, it creates memory B cells that recognize the pathogen and can quickly release a new round of antibodies when they encounter it a second time.
But how well this memory works depends on the pathogen, to understand the case with SARS-CoV2, Nussenzweig and his colleagues studied the antibody responses of 87 individual at two-time points: one month after infection and again six months later. As expected, they found that although antibodies were still obvious by the six-month point, their numbers had noticeably decreased. Laboratory experiments showed that the ability of the participants’ plasma samples to neutralise the virus was reduced by five folds.
In distinction, the patient’s memory B cells specifically those that produce antibodies against SARSCov-2 did not lessen in number and even slightly increased in some cases. The overall number of the memory B cells that produced antibodies attacking the Achilles ‘heel of the virus known as a receptor-binding domain stayed the same “ says Christian Gaebler a physician and immunologist in Nussenzweig’s laboratory. That’s good news because those are the ones that you need if you encounter the virus again.
Viral escapees
A direct look at the memory B cells revealed something surprising; these cells had gone through numerous rounds of mutations even after the infection resolved and as a result, the antibodies they produced were much more effective than the originals. Afterwards, laboratory experiments showed this new set of antibodies superior able to latch on tightly to the virus and could recognize even mutated version of it.
Nussenzweig says “we were surprised to see the memory B cells had kept evolving during this time. That often happens in chronic infections like HIV, herpes where the virus lingers in the body but we weren’t expecting to see it with SARS-CoV-2, which is thought to leave the body after the infection has resolved.”
SARS-CoV-2 reproduces in certain cells in the lungs upper throat and small intestine and residual viral particles hiding within these tissues could be driving the evolution of memory cells. To look into this supposition, the researchers have teamed up with a former Rockefeller scientist and currently a physician at Mount Sinai hospital who has been examining biopsies of intestinal tissue from people who had recovered from COVID-19 on average three months earlier.
In seven of the fourteen individuals studied test shows the presence of SARS-CoV-2 genetic material and its proteins in the cells that line the intestine.
The researchers don’t know whether those viral left over are still infectious or are simply the remains of the dead viruses. So it is advisable to continue maintaining social distance, wear your noise masks and wash your hands frequently.
By: Peace Chigozie
