COVID-19 testing stories, Ads and articles are commonplace. With antigen lateral flow tests and PCR tests probably being most familiar. But are they the only testing solution for supporting a pathway out of the COVID-19 pandemic? They certainly play a role. However, there is another solution that has the potential to be more powerful: neutralising antibody rapid tests.
You will notice we used the term ‘neutralising antibody test’ rather than just ‘antibody test’. There is an important reason for this which will be explained.
What are neutralising antibodies?
Before moving on it is important to know what neutralising antibodies are.
Following infection, the body produces antibodies targeting specific parts of the SARS-CoV-2 (COVID-19) virus with the Nucleocapsid protein and the Spike protein being of importance in the context of antibody tests. The coronavirus nucleocapsid protein is a multi-functional protein1 and the spike protein is integral in penetrating human cells and initiating infection.
IgG neutralising antibodies target the SARS-CoV-2 Spike protein and interfere with the virus’ ability to enter human cells. IgG antibodies are the most common antibody in blood and have a large part to play in conferring immunity to bacteria or viruses.
Immunologically, antibodies to the Nucleocapsid protein are necessary but in the context of pandemic, IgG neutralising antibodies to Spike protein hold the key.
What are COVID-19 neutralising antibody rapid tests?
A neutralising antibody rapid test, such as AbC-19TM Rapid Test, is a lateral flow test that detects IgG antibodies to the full trimeric spike protein of the SARS-CoV-2 virus, from a small finger prick of blood in only 20 minutes. AbC-19TM is a point of care test for use in multiple testing locations and has high sensitivity and specificity. Meaning it has the potential to play a vital supporting role out of the pandemic.
Currently, antibody tests detect antibodies targeting two different proteins on the SARS-CoV-2 virus:
- the Nucleocapsid protein
- the Spike protein
A positive result using each test can confirm prior infection with SARS-CoV-2. However, a positive result with a neutralising antibody rapid test detecting antibodies to the SARS-CoV-2 spike protein holds more significance. This is owing to their infection neutralising capabilities.2
In contrast, a positive test detecting antibodies to the Nucleocapsid protein does not prove whether the body has developed the capability to defeat the infection.
Why use neutralising antibody tests?
There are 3 main uses for neutralising antibody tests:
- Monitor or detect prior COVID-19 infection
- Confirm if someone has produced an immune response following infection
- Monitor antibody vaccine response
Antibody testing use to solely focus on monitoring COVID-19 throughout populations. As more is known about COVID-19 and as governments fight to save economies, antibody testing is increasingly more important. But, as mentioned earlier, testing needs to be focused on neutralising antibodies.
Antigen testing holds an important role but if you get a negative antigen test result, what next? Have you had the virus? Do you have IgG neutralising antibodies to SAR-CoV-2?
This is where the ability to test an immune response becomes vital, especially in multiple testing locations. Something the aviation and transport industries could possibly agree with.
On this subject, new-medical.net succinctly paraphrased research from Queen’s University Belfast by saying:
‘Largescale antibody testing would help to identify immune individuals, allowing them to enjoy the benefits of social activity. But, critical for contagion, negative antibody testing would identify those that are not immune, compelling…individuals to be more cautious…’
These comments are particularly relevant when considering anxiety in the workplace and a desire for employers’ to offer a safe and convenient return to the work.
Vaccine research is mainly focused on the spike protein as the target. These vaccines are designed to “train” the immune system to recognise the Spike protein. Meaning the body produces antibodies to neutralize the effect of SARS-CoV-2.
Using companion neutralising antibody tests with SARS-CoV-2 vaccines has the potential to help further understand the longevity of immunity. Opening the discussion on the value of pre-screening patients prior to vaccination, which could help support immunisation usage and deployment.
In addition, monitoring IgG antibody response in the months and years following vaccination – or indeed following infection – provides data to help guide who has produced the desired immune response and therefore less likely to be at risk. This a powerful tool to inform a country’s management of easing and maintain fewer social restrictions.
Performance data for the use of rapid neutralising antibody tests with the Pfizer-BioNTech vaccine can be found here.
The importance of neutralising antibodies
In May 2021 in Nature.com. Italy’s ISS national health institute published research on the study of 162 patients with symptomatic coronavirus Neutralizing antibody titers progressively drop after 5–8 weeks but are still detectable up to 8 months in the majority of recovered patients regardless of age or co-morbidities, with IgG to spike antigens providing the best correlate of neutralization.
In the New England Medical Journal in April 2021 Rose (National Institute of Allergy and Infectious Diseases) et al published interim results from a phase 3 trial of the Moderna mRNA-1273 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine indicated 94% efficacy in preventing coronavirus disease 2019 (Covid-19) indicating by the persistence of neutralizing antibodies through 6 Months after the Second Dose. A person’s levels of neutralising antibodies following covid-19 vaccination or natural infection could help predict their level of immune protection, the study suggested.
As reported in the New Scientist in May 2021 David Khoury at the University of New South Wales in Sydney, Australia, and colleagues analysed data from seven covid-19 vaccine studies and one study of people who had been infected with the coronavirus and recovered. The researchers modelled the relationship between neutralising antibody levels and protection from disease and found that neutralising antibody levels were highly predictive of immune protection.
Driving a return to normal life
Greece identified the need for antibody testing and announced it was prepared to allow Britons into the country if they can prove they have COVID-19 antibodies3. But considering 34.2 million arrivals were recorded at travel accommodation in Greece in 2019 (Source: Statista.com), COVID-19 antibody testing programmes need to employ rapid diagnostic methods.
Some reading this will say, “just use laboratory testing in advance of arriving at the airport”. This can play a role. However, you cannot time when COVID-19 infection happens or when asymptomatic individuals produce antibodies etc. Testing must take place as close to the point of need as possible.
COVID-19 vaccines are being deployed in the millions and there is a sense in some countries of nearing the end of social restrictions. But, of course, evidence gathering, and appropriate management tools and strategies are needed to avoid complacency.
Understanding immunity and response to vaccination must be part of any ‘COVID-19 pandemic exit strategy’. And Abingdon Health strongly believes rapid neutralising antibody testing needs to be front and centre. To learn more, read our article series about how antibody testing can unlock hard-hit sections of the economy.
There is a changing view on antibody testing, with Hong Kong announcing [June 2021] that “fully vaccinated travellers who also test positive for antibodies could undergo a seven-day quarantine” rather than the standard 21 days.4 Placing even more importance on antibodies to SARS-CoV-2 virus in supporting vaccine efficacy and determining who is safe to travel.
To further answer ‘what are COVID-19 neutralising antibody rapid tests and why use them?’, Abingdon Health has produced a White Paper. It explains the use AbC-19TM Rapid Test as a companion test to SARS-CoV-2 vaccination. Alternatively, visit the AbC-19TM product page.
- McBride, R et al.The Coronavirus Nucleocapsid Is a Multifunctional Protein. Viruses. 2014 Aug; 6(8): 2991–3018. doi: 10.3390/v6082991.
- McAndrews, KM et al. Heterogeneous antibodies against SARS-CoV-2 spike receptor binding domain and nucleocapsid with implications for COVID-19 immunity. JCI Insight. 2020 Sep 17;5(18):e142386.
Updated 23rd June 2021