Many of us ask: Have I already been exposed to the coronavirus and am immune to more … [+]
Many of us ask: Have I already been exposed to the coronavirus and am immune to further infection?
A new fast, easy, and sensitive antibody test detects specific biomarkers of long-term immune protection against SARS-CoV-2 that may answer that question.
If Covid is here for the foreseeable future, and waves of infections from Brazil to the US and India suggest it, then we will have to find ways to keep the economy safe despite it.
One way is to try to understand how much of the population is immune to the virus and how long that immunity lasts. This could help us understand if a vaccine could be effective in the long term and also if solutions such as immunity passports could be a viable option.
Unfortunately, currently no evidence can give us any guarantee of this. We know from related coronaviruses, such as those that cause the common cold, that immunity is often short-lived, and people can be reinfected with the same virus.
Some studies also suggest that antibodies drop to undetectable levels in just a few months after Covid infection, boosting the widely circulated perception in recent weeks that immunity to the disease is only temporary. Antibody tests that are currently used lose this vital part of the image.
GenScript, a leading life science company, has a new antibody test that could raise the bar for testing and give us a clearer idea of how to fight the coronavirus. Today, in the prestigious scientific journal Nature, GenScript describes the first results of the test, which targets specialized antibodies against the virus known as neutralizing antibodies The results suggests that we may rethink our understanding of long-term immunity to Covid, and offers hope for the effectiveness of a future vaccine.
Neutralizing a pathogen
When a virus infects our body, our immune system kicks in to fight it in various ways. A part of that immune response involves antibodies, the tiny proteins that recognize and attach to a virus. But not all antibodies are created equal.
“When you have a virus, you generate all of these antibodies, but only a small fraction binds to the virus in a way that prevents it from infecting a cell,” explains Eric Wang of GenScript. “Those are the neutralizing antibodies.”
Neutralizing antibodies make up less than 1% of total antibodies measured by current commercial tests, and Wang says he is missing them. That means we might be underestimating how many people are already protected against reinfection with the virus.
Neutralizing antibodies are not sufficient in all cases. But based on the body’s response to other viruses, neutralizing antibodies are a good indicator of protective immunity in most patients who have recovered from illness.
“All antibody tests at this time look at total antibodies, and these can be significantly reduced just a few months after a patient recovers from Covid,” says Wang. “But as long as he has a small amount of neutralizing antibody, the patient still it may be immune to the virus. “
Recent studies have indicated that total antibodies, including neutralizing antibodies, are lowered in asymptomatic and symptomatic Covid survivors. A team in the United Kingdom last week suggested that this seemingly transient immune response, which included a reduction in neutralizing antibodies, could be related to the severity of the initial disease.
However, a study led by Dr. Lin-fa Wang, Director of Duke-NUS’s Emerging Infectious Diseases program, suggests that we might rethink what this means for long-term immunity to Covid.
Research shows that the novel, specific and more sensitive GenScript antibody test could detect significant levels of neutralizing antibodies, even in patients who show low levels of antibodies overall. This effect was confirmed in cohorts of patients in two different countries: Singapore and China.
Another promising finding was obtained from the blood serum of patients previously infected with the 2003 SARS virus, who still had detectable neutralizing antibodies 17 years after recovery, indicating the possibility of long-term protection against a similar virus.
Introducing the first SARS-CoV-2 neutralization test
According to GenScript, the cPass test, or SARS-CoV-2 Substitute Virus Neutralization Test (sVNT), is safer, faster, easier, and more responsive than traditional virus-based or cell-based tests with comparable specificity. It is under review by the FDA, but it already has CE-IVD authorization in Europe and received provisional authorization for clinical use in Singapore.
David Martz, Vice President of New Product Development at the GenScript Life Sciences Group, said: “This document demonstrates that sVNT can detect neutralizing antibodies, better known as immunity biomarkers, with a sensitivity of 95-100% and a specificity of 99.93%. In addition, this new method also provides the means to perform standardized tests. “
So how does it work?
“It uses a different principle,” says Wang. “We don’t detect the antibody itself, but we look in the blood for anything that blocks the binding of the virus. [spike protein] to the hACE2 receptor in human cells. It is a functional assay that specifically looks for the neutralizing antibody. “
At the moment, the company cannot say with certainty that this test, even if it detects neutralizing antibodies, guarantees immunity against reinfection with Covid. That still requires more research. However, the test could offer a vital step in trying to discover our current levels of collective immunity, for example, or if that is possible without a vaccine. When a vaccine appears, it can also help show if it is effective.
“We need something to assess whether people who receive the vaccines generate neutralizing antibodies,” says Wang. “And not just any antibody. It has to be the neutralizing antibody. “
They are neutralizing antibodies that will offer long-term protection against Covid, stopping the disease before it takes root.
The Covid Mysteries
A recent study from Spain published in The Lancet found that 5% of the population carried antibodies to Covid. The study was carried out using non-specific antibody tests, which is useful to measure how much the virus had spread to the Spanish population. But no conclusions can be drawn about the potential immunity of the herd among those already exposed.
Imagine if scientists had access to the cPass test. They could not only accurately determine the total level of neutralizing antibodies, but also use this test to assess the immunity of the herd, “added Martz. “We are very excited to see how this will shed new light on Covid’s current mysteries.”
Covid remains a puzzle in many ways, and it’s still unclear how long immunity to the virus will last. However, neutralizing antibodies are a fairly good indicator of immunity, and improved antibody tests provide us with a much more detailed understanding of the effects the virus is having on the general population, aiding us in the ongoing fight against the pandemic.
Follow me on Twitter at @johncumbers and @synbiobeta. Subscribe to my weekly newsletters on synthetic biology. Thanks to Peter Bickerton for additional research and reporting in this article. I am the founder of SynBioBeta, and some of the companies I write about, including GenScript, are sponsors of SynBioBeta Conference and weekly summary. Here is the full list of SynBioBeta sponsors.
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