Current coronavirus vaccines are humanity's lethal weapon against a single virus, SARS-CoV-2. But SARS-CoV-2 is not the first coronavirus to hop from animals to humans — and it will not be the last.
To prevent a future coronavirus pandemic, a group of researchers recently developed a "pan-coronavirus" vaccine, designed to protect against many different strains of coronaviruses known to infect humans and bats. Their vaccine turned out to be very effective in monkeys, but it's not yet known if it will confer the same protection in people, according to the study published May 10 in the journal Nature.
While no one knows what kind of virus will cause the next pandemic, coronaviruses are "definitely a threat," said lead author Kevin Saunders, the director of research at the Duke Human Vaccine Institute in North Carolina. For the past few decades, "about every eight years or so there seems to be a coronavirus that comes along that causes an outbreak."
SARS-CoV-1 — which caused an outbreak in 2003 — and SARS-CoV-2 both use what's called a spike protein to grab hold of the ACE2 receptor on human cells and infect them. These spikes lock into human cells at a specific viral region known as the "receptor binding domain." But these two viruses are not the only coronaviruses that use this method of invasion; similar coronaviruses that use ACE2 as their gateway to infection are known to currently circulate in civets, bats and pangolins, according to the study.
"That's why we're testing whether or not the vaccines are effective against the bat coronaviruses as well as the human coronaviruses," Saunders told Live Science. Saunders and his team designed the novel coronavirus vaccine, which they hope could elicit an immune response across different coronaviruses that use the RBD to enter human cells.
They started with an antibody that was taken from a person infected with SARS-CoV-1, which disarmed multiple different coronaviruses.
They designed a vaccine that uses nanoparticles with bits of RBD attached to its surface in such a way that "you get a molecule that looks like a virus," which the immune system can then recognize and respond to, Saunders said. (Most current vaccines target the full-length spike protein whereas this vaccine specifically targets the RBD). They included an adjuvant, a substance that boosts the immune response.
In monkeys, the vaccine stopped all infections with SARS-CoV-2 and spurred more neutralizing antibodies than either current vaccines or natural infection spurs in humans. Four out of five monkeys did not have any trace of the virus; one monkey had a very low level of virus that could only be detected with very sensitive tests and that went away in two days, Saunders said.
What's more, in monkeys, the vaccine also spurred neutralizing antibodies against some bat coronaviruses, SARS-CoV-1 and common variants of SARS-CoV-2: B.1.1.7 that was first found in the United Kingdom, P.1 that was first found in Brazil, and B.1.351 that was first found in South Africa.
Current mRNA vaccines — developed by Modern and Pfizer — also elicit antibodies that react against multiple different coronaviruses, but at lower levels, Saunders said.
Eventually, the hope is that a pan-coronavirus vaccine could have an even broader response to help fight more divergent coronaviruses as well, Saunders said.
"Now, although these experiments [were] conducted in a nonhuman primate — and we always have to have a caveat when you’re dealing in a nonhuman primate — nonetheless, this is an extremely important proof of concept that we will be aggressively pursuing as we get into the development of human trials," Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases (and not involved with the work) said about this study at a White House Briefing on May 13.
"There's no data yet to say how this will translate to humans," Saunders said. But, "What's encouraging is that the vaccine was based off of an antibody that we found from a human."
Now, the researchers are hoping to design a small clinical trial to first test the safety of their vaccine in humans.
Originally published on Live Science.
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Yasemin is a staff writer at Live Science, covering health, neuroscience and biology. Her work has appeared in Scientific American, Science and the San Jose Mercury News. She has a bachelor's degree in biomedical engineering from the University of Connecticut and a graduate certificate in science communication from the University of California, Santa Cruz.