Alert! Coronavirus spike proteins may evolve to evade immune responses

Coronavirus spike proteins may evolve to evade human immune system

A recent study has revealed that SARS-CoV-2 which causes COVID-19 evolves in the same way as other coronaviruses. Can the existing vaccines still keep you safe? Read to know more.

Raising a big question on the long-term effectiveness of coronavirus vaccines to curb the ongoing pandemic, a study has revealed that some coronaviruses -- the family of viruses which includes the one causing COVID-19 -- can evolve to escape recognition by the host immune system.

Current Coronavirus Vaccine May Become Outdated!

The study which was conducted to see the effectiveness of the coronavirus vaccine has shown that if the novel coronavirus SARS-CoV-2 which causes COVID-19 evolves in the same way as other coronaviruses, current vaccines against the virus may become outdated, requiring new ones to be made to match future strains.

Let's have a quick look at what these strains are. Well, according to the experts, there are hundreds of coronaviruses that can be found in various animals such as pigs, bats, etc. Among all these various types of coronavirus, seven have been found to have infected humans. Some of the coronaviruses that can commonly infect humans are: 229E, NL63, OC43, and HKU1. Other than these, some of the most infectious coronaviruses are MERS-CoV, SARS-CoV, and SARS-CoV-2.

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Speaking to the media, study author Kathryn Kistler said, "Some coronavirus are known to reinfect humans but it is not clear to what extent this is due to our immune memory fading or antigenic drift".

She further added, "We wanted to investigate whether there is any evidence of coronavirus related to SARS-CoV-2 evolving to evade our immune responses".

What Happens After Your Body Receives The Vaccine Shot?

When a person is infected by a virus or vaccinated against it, cells part of their body's immune system produce antibodies that can recognize and bind to unique proteins on the virus' surface known as antigens.

In order to provide immunity against the virus, the immune system relies on being able to 'remember' the antigens that relate to a specific virus, the scientists explained.

However, the study stated that in some viruses, such as the seasonal flu, the antigens are likely to change and evolve in a process called antigenic drift, and the immune system may no longer respond to reinfection.

Antigens May Evolve Against The Human Immune System

In the current study, the scientists looked at the four seasonal human coronaviruses (HCoVs) which are related to SARS-CoV-2 but typically cause milder symptoms, such as the common cold.

HCoVs, the scientists said, have been circulating in the human population for 20-60 years, meaning their antigens may have faced pressure to evolve against the human immune system.

The researchers used computational methods to compare the genetic sequences of many different strains of HCoVs and saw how these viruses have evolved over the years.

High Rate Of Evolution In The Coronavirus' Protein Spike

They particularly assessed changes that might have occurred in proteins that could contain antigens, such as the viral spike proteins -- the projections on the surface of coronavirus that are particularly exposed to our immune system.

From the analysis, the scientists found a high rate of evolution in the spike proteins of two of the four viruses, OC43 and 229E.

According to the researchers, nearly all of the beneficial mutations appeared in a specific region of the spike proteins called S1, which helps the virus enter human cells.

Why Coronavirus Protein Spikes Are Undergoing Changes?

According to the researchers, reinfection by these two viruses can occur as a result of antigenic drift as they evolve to escape recognition by the immune system.

They also estimated that beneficial mutations in the spike proteins of OC43 and 229E appear roughly once every two to three years -- about half to one-third of the rate seen in the flu virus strain, H3N2.

"Due to the high complexity and diversity of HCoVs, it is not entirely clear if this means that other coronaviruses, such as SARS-CoV-2, will evolve in the same way," said study senior author Trevor Bedford from the Fred Hutchinson Cancer Research Center.

"The current vaccines against coronavirus, while highly effective, may need to be reformulated to match new strains, making it vital to continually monitor the evolution of the virus' antigens," Bedford said.

(With inputs from the Agencies)

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