Viral-fighting antibodies have been found in Kiwi Covid-19 patients for up to eight months after they were infected – a finding that could bode well for the upcoming vaccine rollout.
The new research, released before peer review, has also proven to be of global importance, given that antibodies persist even when no viruses are circulating in the community.
The study analyzed antibodies in a group of 112 New Zealand patients previously infected with the SARS-CoV-2 virus, most of whom had mild symptoms.
Antibodies play an important role in the immune system against pathogens such as the coronavirus.
Once a new virus is recognized, antibodies are specially crafted to bind to the “spike protein” and stop it from entering our cells – while signaling other parts of the immune system to destroy foreign invaders.
“Because antibodies are very specific for an invading pathogen or virus, they also provide a way to track and study a person’s history of infection,” said Dr. Nikki Moreland, an immunologist and biomedical scientist at the University of Auckland.
“In other words, by taking a blood sample of someone, and seeing if there are specific antibodies for SARS-CoV-2 in circulation, it’s possible to determine if they have previously had Covid-19.”
This is useful for diagnosis – especially when the swab has no more virus due to infection several weeks or months ago.
“By studying the level and function of circulating antibodies, it is also possible to determine whether a person has the types of antibodies that might provide protection if they encounter certain viruses or pathogens again.”
The new collaborative study, carried out by PhD student Alana Whitcombe and research scientist Dr Reuben McGregor on the Moreland team, investigates not only the quantity of antibodies in previously infected people – but also their quality.
“Specifically, do people have antibodies that bind to viral spike proteins, can these antibodies neutralize the virus, and how long do these antibodies last?” McGregor said.
In the laboratory, the researchers measured levels of circulating antibodies that bind to spike proteins, as well as whether those antibodies neutralized.
“Since we had samples from people who were infected months earlier, we can use this measurement to see how long the antibodies last.”
“The good news is we observed that the majority of people have neutralizing antibodies that bind to the spike protein and they can be detected for up to eight months after infection.”
While overseas research shows this too, the main difference is that this effect has been demonstrated in countries where Covid-19 has been successfully eliminated.
“People in New Zealand are not re-exposed to the virus like they are in countries with high community transmission rates,” Moreland said.
When someone is re-exposed, he explained, their immune system boosts, which can affect levels of circulating antibodies.
That makes similar data from abroad more difficult to interpret, given it’s unclear whether antibodies were there simply as a result of re-exposure.
“In New Zealand we are fortunate not to have that problem to consider when looking at our data,” said Moreland.
“We believe the antibodies we measured came from the initial infection, so seeing these antibodies last up to eight months was really encouraging.”
What does the vaccine launch mean?
Moreland said the study offers some “positive signals”, given the data from vaccine trials showing the agent induces similar – and in some cases higher – levels of neutralizing antibodies for natural infections.
“So the protection from the vaccine is also likely to last for months and maybe even longer,” he said.
“But we are still studying in real-time, every month we see that the antibodies last one month longer.
“Also, there are several different vaccines and it is important to track the antibody response to different vaccines to measure whether there is a difference in the quality and quantity of the antibodies they produce, and how long the neutralizing antibodies to vaccines last.”
Further studies showed that scientists could accurately measure spike antibodies from finger prick blood samples.
“This could drastically improve the feasibility of large-scale studies to track vaccine antibody responses.” Whitcombe said.
The paper, uploaded to medRxiv’s pre-print server, involved doctors and scientists from the University of Otago, New Zealand Blood Service, Te Punaha Matatini, Callaghan Innovations, the Maurice Wilkins Center, Southern Community Laboratory and the City of Auckland, Starship and Kidz First Children’s Hospital .
“This work would not have been possible without a national network of doctors, nurses, researchers and scientists and highlighted the collaborative nature of New Zealand’s science during the pandemic,” said Moreland.