On Our Way to Covid-19 Immunity

13/04/2021 - 6 minutes

Safely developing immunity will be key to exiting the Covid-19 pandemic. Can testing for neutralizing antibodies against SARS-CoV-2 help pave the way?

As the first reports of the newly emerging respiratory disease trickled in, most of us could not imagine that it would disrupt everyday life around the world for over a year. Yet it did. According to the World Health Organization, over 131 million infections with the new SARS-CoV-2 virus and almost 2.9 million associated deaths from Covid-19 were confirmed over the last sixteen months. 

To slow the spread of the coronavirus and protect healthcare systems, governments implemented restrictive lockdowns. While these drastic measures upended the global economy and caused major recessions, they also helped decrease infection rates, hospitalizations, and deaths. 

Many experts believe that reaching herd immunity – the point when most people are immune and the virus cannot rapidly spread – will be critical to ending the Covid-19 pandemic and returning to a new normal.

Safe immunity is key to exiting the pandemic 

Antibodies are part of the immune response against viruses, such as SARS-CoV-2

People who catch SARS-CoV-2 develop natural immunity, but the degree and duration of this protection are poorly understood, and vary from person to person.

When we get infected with a new virus, such as SARS-CoV-2, our bodies activate an innate immune response, releasing cytokines to trigger inflammation and kill the virus and infected cells.

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The adaptive immune response comes next. Our bodies learn to recognize the virus and produce antibodies and immune cells, which can specifically neutralize it and kill infected cells upon subsequent exposures to the virus.

But with SARS-CoV-2, the initial inflammatory response can be too strong and severely damage healthy cells and tissues, while the virus continues to replicate. Thus, many experts advise that vaccination is the safest route to immunity, as it avoids the risk of serious illness and death.

“Vaccines introduce our bodies to pathogenic proteins that train our immune systems to recognize the pathogen and protect us against it. They do this without the risk of disease and severe inflammation that can occur in natural infections,” explained Shuting Xu, a field application scientist at the US firm GenScript Biotech.

Training the immune system to fight Covid-19

The SARS-CoV-2 virus uses a protein on its surface called spike protein to infect our cells. DNA and mRNA vaccines enter our cells and produce copies of the spike protein based on the introduced nucleic acids. Inactivated virus and protein-based vaccines can be directly recognized by our immune cells.

As our immune cells make contact with the copies of the viral spike protein, they activate a response and trigger the proliferation of various types of immune cells: killer T cells will be able to recognize and specifically kill cells with the SARS-CoV-2 spike protein on their surface, B cells produce neutralizing antibodies that can recognize the viral spike protein, and memory B and T cells store information about the virus for many years. 

If we are exposed to SARS-CoV-2 at a later point in time, those neutralizing antibodies bind to the spike protein on the virus’s surface and neutralize the virus, preventing it from infecting our cells. The memory B and T cells are also ready to initiate a rapid and specific attack if needed. 

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The importance of SARS-CoV-2 neutralizing antibodies

Neutralizing antibodies prevent the virus from spreading to healthy cells and eliminate the infection during early stages

The presence of neutralizing antibodies in our bodies has been shown to correlate with protection from viral infection. Hence, these molecules play an important role in SARS-CoV-2 vaccine and treatment research and development.

Most of the SARS-CoV-2 vaccines in use or under investigation aim to produce neutralizing antibodies specific for the spike protein on the outside of the virus particles. The spike protein facilitates fusion between the virus and our cell membranes and allows viral material to enter the cell. 

Neutralizing antibodies against the spike protein can prevent the interaction between the virus and our cells and help eliminate an infection during its early stages. Thus, measuring the abundance of these antibodies is one of the key parameters for evaluating potential SARS-CoV-2 vaccines. 

“Scientists are racing to develop vaccines that induce neutralizing antibodies against the SARS-CoV-2 spike protein,” explained Xu. “This approach has been used with many successful viral vaccines, and there’s hope that it will provide long-lasting protection here, too.”

Specific neutralizing antibody-based therapies are also being used to treat people already infected with the virus, and so far, these are showing great promise in reducing hospitalizations and death.

Neutralizing antibodies are important to a variety of SARS-CoV-2 research applications as well. Their abundance can indicate the potential therapeutic quality of plasma donated by previously infected individuals, and they can reveal how many people in a population have already been infected. 

Neutralizing antibodies can further our understanding of SARS-CoV-2 infection in pets, livestock, and other animals, allowing us to act smartly to protect both ourselves and the animals.

And neutralizing antibodies might also play an important role in determining an individual’s basal immunity following vaccination or infection. 

We just don’t know yet how long the protective effect from a vaccine or infection lasts,” said Xu. “If the protection fades over time, or if we need to show immunity passports for travel, measuring basal immunity will become very important.”

Testing for antibodies that neutralize SARS-CoV-2 

The current gold standard method for detecting neutralizing antibodies is the plaque reduction neutralization test (PRNT), a multi-day procedure that requires infecting cells with live viruses in highly contained biosafety facilities. GenScript Biotech offers a better solution: the cPass SARS-CoV-2 Neutralization Antibody Detection kit. 

The novel cPass technology is a surrogate virus neutralization test, because it perfectly mimics the entry of SARS-CoV-2 into host cells,” explained Xu.

covid-10, neutralizing antibodies, SARS-CoV-2
GenScript’s cPass SARS-CoV-2 Neutralization Antibody Detection Kit

This test works on human and animal samples and is fast, safe, and accessible. It can also be easily scaled up for high-throughput, automated testing.

“This kit is the first of its kind and so far, it is the only commercial test with FDA emergency use authorization that can directly detect circulating neutralizing antibodies against SARS-CoV-2,” Xu said.

Visit GenScript to learn more about the novel cPass technology and SARS-CoV-2 neutralizing antibody detection.

Images via Shutterstock.com & GenScript

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