Coronavirus and the immune system: SA study to shed light

• Scientists worldwide are trying to find out why the new coronavirus affects individuals so differently
• In a new study, researchers from UCT are trying to solve this puzzle
• Their study will run over three years, and will involve healthcare workers as primary participants

Understanding how the immune system responds to SARS-CoV-2, the virus that causes Covid-19, and why some individuals are affected more severely than others, have been on researchers’ agenda  since the very beginning of the pandemic.

Now, a team of researchers led by Associate Professor Wendy Burgers, a viral immunologist in the Division of Medical Virology at the University of Cape Town (UCT) will be working to gain insight into how long immune responses to the virus last; how strong those immune responses are; as well as understanding whether prior exposure to other related coronaviruses helps patients build a level of immunity to Covid-19.

“We’re trying to understand whether those patients who have been exposed to the common cold viruses (viruses related to Covid-19) build a level of immunity.

“In this case, T cells that can recognise SARS-CoV-2 might protect patients from contracting severe Covid-19,” Burgers said in a news release by the university.

Current study builds on previous study

The current study builds on previous research led by Dr Stephen Makatsa, a postdoctoral fellow in the Division of Medical Virology.

The study spanned three months (May to July 2020) and involved 77 participants. The research team established that an antibody assay (a biochemical test that measures the presence or concentration of antibodies in a patient’s blood) recognises the Covid-19 virus, and signals that infection has occurred and an immune response has formed.

“Results show that our test works really well in measuring antibodies in people who have been infected,” Burgers said.

The goal now, Burgers commented, is to use that same test to measure antibody responses and see how long they last in patients who have been previously infected.

The team is also studying the immune responses of healthcare workers who were infected with Covid-19, as well as a group of their peers who have not been infected with the virus.

Since healthcare workers have a high risk of exposure to the virus, they are primary participants in this study. The study will run for three years and study visits will occur every six months to obtain samples and perform tests.

What the data can offer

The antibody data available will allow researchers to measure antibodies in most people who have been infected with Covid-19, Burgers explained.

However, in some cases, patients have displayed very low antibody responses post-infection. This, Burgers added, could be related to the time period after infection, and whether individuals experienced mild or severe disease.

“This has caused quite a lot of alarm, but it’s important to remember that this is a normal immune response, where antibodies wane after the initial infection is cleared,” she said.

Taking into account the difficulty of measuring every individual exposed to the virus’s antibody responses, Burgers said that if previously infected individuals were to be re-exposed to the virus, immune memory could kick in and expand to very high levels, consequently protecting the person from reinfection.

For those participants who have not been infected with the virus, the researchers will study whether any “cross-reactive” T cells have any effect in modulating the outcome of infection or the course of Covid-19 disease, should they become infected over the course of the study.

A certain amount of protection

On the question whether patients can become reinfected with Covid-19, Burgers responded:

“Our basic understanding of immunology and our experience of the pandemic thus far suggest that there certainly are some months of immunity because there are no widespread reports of people becoming reinfected

“So, we can safely say that we do build a certain amount of immunity that protects us. We just don’t know for sure how long it lasts.”

Burgers believes that it’s important to understand the immune responses in South Africans.

“We need to determine whether findings are the same or different with South Africans compared to elsewhere in the world,” she explained. 

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