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Infectious Diseases

Updated 17 September 2020

Antibody responses in Covid-19 patients: What latest study reveals

A recent analysis of antibody responses in Covid-19 patients may help to inform decisions into antibody-based intervention and vaccine design.

  • A team of Chinese researchers studied the antibody responses of Covid-19 patients.
  • Patients included in their research had both mild and severe Covid-19 disease.
  • Their findings will help provide a better understanding of antibody responses against SARS-CoV-2.

A new comprehensive analysis of antibody responses in Covid-19 patients showed that the neutralising activity of antibodies from the recovered patients was typically not strong, and declined sharply within one month of hospital discharge.

Researchers Chao Wu and Rui Huang, of Nanjing University Medical School in China, monitored the SARS-CoV-2-specific antibody responses in 19 non-severe and seven severe Covid-19 patients for seven weeks from disease onset.

They wrote that the results of their study, published in PLOS Pathogens this month, may serve as fundamental information for developing a Covid-19 vaccine, as well as effective treatments for the disease.

Neutralising antibodies

Neutralising antibodies, as explained in a previous Health24 article, is an important line of defence in the fight against Covid-19. They do their job by binding to specific parts of the virus, and neutralise the virus’s damaging effects.

If antibodies are found to be present, they indicate that the person has previously had a SARS-CoV-2 infection (as the antibodies are only produced by infection), and that if that same person encountered the virus again, the presence of antibodies would likely result in a level of protection.

What the latest study found

In the Chinese study, the researchers found that the majority of patients generated antibody responses against SARS-CoV-2.

They also wrote that just over 80% of recovered Covid-19 patients had varying levels of antibody neutralisation activity against the virus, but that only a small group of patients elicited a potent level of neutralisation activity.

This result only means that blood samples from recovered patients using antibody neutralisation assays prior to transfusion into other Covid-19 patients will need to be carefully considered going forward.

The blood samples mentioned by the authors refer to convalescent plasma – a form of therapy that uses blood from people who've recovered from diseases, such as Covid-19, to help others recover.

According to a Health24 article, Covid-19 survivors’ blood can be a rich source of antibodies that the immune system makes to attack the virus. 

Significant decline in antibodies post-hospital discharge

The sharp decline of neutralising antibodies in the patients studied were seen three to four weeks after hospital discharge, which means that recovered Covid-19 patients may be susceptible to reinfection with SARS-CoV-2 – something that was seen in a Hong Kong case just last month.

Non-neutralising antibodies, which may contribute to antibody-dependent enhancement of infection, were also seen in the severe Covid-19 patients studied.

Based on the findings as a whole, these could all offer insights for serological testing, antibody-based intervention, and Covid-19 vaccine design.

READ | Three things scientists still need to learn about Covid-19 reinfections

READ | Covid-19: Understanding immunity and what it means for a vaccine

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Image: Getty/SDI Productions