How COVID-19 stimulates antibodies against the common cold

“, said Andrew Ward, PhD, professor of Integrative Structural and Computational Biology at Scripps Research and senior author of the new paper, published online this week in the journal Science Advances.

The SARS-CoV-2 virus that causes COVID-19 is just one of a large and diverse family of coronaviruses. Some of its relatives are equally contagious and virulent, causing Middle East respiratory syndrome (MERS) and the 2002-2004 SARS outbreak, while others, are considered common cold viruses. often, causing much milder symptoms.

Collectively, many of these coronaviruses have only a quarter to one-half of the genetic material in common with SARS-CoV-2, but individual parts of the virus’s structure — most notably, the mutated protein protruding from each coronavirus. — considered to be relatively similar among family members.

Since the start of the COVID-19 pandemic, scientists have wondered whether people’s previous exposure to those common cold viruses affects their immunity to SARS. -CoV-2 and whether COVID-19 infection could change how the immune system recognizes the common coronavirus.

The immune system’s antibodies against a coronavirus spike protein could potentially also recognize other similarly mutated proteins as pathogens.

For the new study, Ward’s team studied serum samples from 11 people. Eight of the samples were dated to pre-COVID-19 to ensure donors had never been exposed to the SARS-CoV-2 virus, while three were taken from donors who had recently contracted COVID. -19.

In each case, the researchers measured the responses of the samples to mutant proteins isolated from different coronaviruses – OC43 and HKU1, both of which are associated with the common cold, along with SARS- CoV-1, MERS-CoV and SARS-CoV-2.

Not surprisingly, only the sera of recovered COVID-19 patients reacted with the mutant proteins of SARS-CoV-2. However, these COVID-19 patient samples were also more reactive than pre-pandemic samples to other mutated proteins.

Most people have this basic immunity to the common coronavirus, and exposure to SARS-CoV-2 increases levels of these antibodies.“Sandhya Bangaru, first author of the new paper, said”.

Ward, Bangaru and their colleagues performed high-resolution structural studies of serum antibodies from three healthy donors and two COVID-19 patients to locate the mutant proteins. variable to which each antibody binds.

They found that most pre-pandemic coronavirus antibodies recognized a part of the OC43 and HKU1 spike protein called the S1 subunit, which tends to vary greatly between coronaviruses.

However, in samples of COVID-19 patients, the researchers identified a broader range of antibodies, including those that recognize the S2 subunit — little changed between different coronaviruses. Indeed, some antibodies from COVID-19 patients bind not only to the common cold coronavirus but also to the SARS-CoV- and MERS-CoV spike proteins.

The ultimate goal of this is to rationally design vaccines that can recognize many different types of coronavirus“Bangaru said.

Our results show that certain conserved patches on the S2 subunit are targeted by antibodies naturally produced during infection, which we wanted to focus on.. “

Because these studies were performed directly on serum antibodies, the researchers do not know whether the presence of these antibodies is, in any case, sufficient to provide adequate immunity. sufficient for the coronavirus in the more complex environment of the human immune system.

The increased ability of convalescent sera to respond to common coronaviruses appears to be the result of both increased production of novel antibodies that can recognize some coronaviruses and also increased levels of antibodies. preexisting virus specificity.

However, it is not clear how much each of these phenomena contributes to the overall increase and how they will affect the natural course of COVID. In the future, they want to compare antibodies from the same individual before and after infection with COVID-19.

Our work provides the baseline characterization of people’s antibody responses to endemic coronaviruses prior to SARS-CoV-2 exposure, but many open questions remain.“Bangaru said.”We hope this leads to more research. “

Source: Medindia

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