Of antibodies and immunity: Research to learn more about post-infection protection from COVID-19

Dr. Steven Drews

Although we are starting to learn a lot more about SARS-CoV-2, the virus that causes COVID-19 disease, researchers around the world are still investigating how our immune systems could protect us from it.

"We know that, generally, people who have been infected with SARS-CoV-2 produce antibodies against it—but do those antibodies protect against reinfection? If so, are there limits to that protection?" asks Dr. Steven Drews, a microbiologist at the University of Alberta and associate director of microbiology at Canadian Blood Services. "And, assuming there is at least some protection, what does it look like in the Canadian population? These are questions that we're still trying to answer."

Dr. Drews is now leading a team that will analyze thousands of retained blood samples from anonymized Canadian Blood Services donors as part of a new project to learn more about potential immunity in people who have recovered from COVID-19. Throughout the year-long study, the team will test each blood sample for SARS-CoV-2 antibodies—in part to help researchers estimate how many people have been infected in Canada, but also to look for clues about whether there are region- or age-specific immunity patterns taking shape across the country.

This is a tall order because, as Dr. Drews is quick to point out, antibodies and immunity are not the same thing, and immunity research tends to highlight "more nuances than absolutes."

"Even if people have antibodies, those antibodies may not mean that a person is protected from future infection," he continues. "At the same time, people with no antibodies may still have other parts of the immune system protecting them. Immunity and infection are complex problems that may present differently between different people for a wide variety of reasons, which is why we need so much high-quality research to move forward. "   

With his own research, Dr. Drews is aiming to gain a better understanding of the finer details of the antibody response after infection. All the blood samples in the study that test positive for SARS-CoV-2 antibodies will undergo further testing to determine the concentration of antibodies per sample and whether those antibodies are capable of "neutralizing" the virus, a process that involves sticking to certain parts of the virus to prevent it from entering the host cell and proliferating. If a person's antibodies can effectively neutralize the virus, for example, then they likely will have at least some natural defense against letting a new infection take hold.

Studies have already shown that levels (concentration) of SARS-CoV-2 antibodies in some people decrease after three or four months, but we don't yet know if that means the potential protection fades with them. Dr. Drews is hoping to get a better sense of whether antibody levels have an impact on protection, but he is also hoping the team's data will shed light on how strongly the antibodies can bind to the virus in the first place.

"In particular, we are interested in seeing whether people can make a really strong neutralizing antibody that may not be present in large amounts," he explains. "And, if there is such an antibody, is it only present in certain groups or people of certain ages? These are the types of things that public health officials would need to keep in mind when they consider where vulnerabilities exist in different populations."

By early 2021, Dr. Drews and his team will have preliminary data about these antibody responses in representatives from the Canadian population, which will "yield important information about the disease and about short- or long-term protection, right here at home."

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