While various biopharmas are working on vaccines that could protect against multiple strains of COVID-19, researchers in the U.S. have reported early success in a shot that goes even further—offering protection against a range of other coronaviruses like SARS.
In the results of a study published Oct. 18 in Cell Reports (PDF), researchers from Duke University Medical Center’s Duke Human Vaccine Institute demonstrated that a pan-coronavirus vaccine targeting SARS-CoV-2, the Middle East respiratory syndrome (MERS) coronavirus and a bat-like coronavirus that hasn’t yet jumped from animals to humans protected mice from illness following exposure to mouse forms of the pathogens.
“We are making important progress toward a broadly protective coronavirus vaccine,” senior author Kevin Saunders, Ph.D., said in a press release. “These are pathogens that cause or have the potential to cause significant human infections and loss of life, and a single vaccine that provides protection could slow down or even prevent another pandemic.”
The vaccine contains nanoparticles carrying each of the viruses’ receptor binding domains, or RBD, a component that enables them to bind to and infect cells. Upon injection, the immune system forms antibodies to the RBDs so it can recognize the viruses later.
After seeing that the vaccines generated antibodies to all three viruses in mice, the researchers immunized groups of older adult animals with the vaccine and exposed them to dangerous mouse versions of the original SARS-CoV virus, which causes severe acute respiratory syndrome (SARS), and the virus that causes Middle East Respiratory Syndrome, or MERS. In another group of mice, they tested a monovalent vaccine containing only nanoparticles that would generate antibodies to SARS-CoV-2 to see if it afforded cross-protection against the other two viruses. Mice that received two doses of the trivalent vaccine were protected from dying of both SARS and MERS.
While two shots were enough to prevent viral replication and severe disease from SARS, a third was required to provide this level of protection from MERS, the researchers noted. As for the monovalent COVID-19 vaccine, it didn’t protect the mice against severe disease from MERS, but did work against SARS, the researchers noted. Antibodies produced by the trivalent vaccine worked against several other types of coronaviruses as well, with three doses generating greater responses than two.
“This vaccine is an advance over current SARS-CoV-2 mRNA vaccines, which lack protection against other [coronaviruses such as SARS and MERS],” the researchers wrote in the paper.
One limitation of the study is that it's not clear how long protection lasts, the scientists wrote. They also didn't assess whether the vaccine generates other T cell and B cell responses in the lungs and nasal passages in addition to generating antibodies against the viruses.
There is no vaccine approved yet for MERS or SARS, though some for MERS, such as the ChAdOx1 vaccine from the University of Oxford, are in development. A few other groups besides Duke are pursuing pan-coronavirus vaccines, such as the U.S. military’s Walter Reed Army Institute of Research and VBI Vaccines, which recently presented interim data from a phase 1 clinical trial against various COVID-19 variants as well as bat and pangolin coronaviruses.
Meanwhile, Duke has already demonstrated that the monovalent version of its receptor-binding domain COVID-19 vaccine works against multiple variants of the virus in primates and mice. The team plans to take the candidate into clinical trials next year.