Promising results new vaccination strategy with whole coronavirus

This strategy may provide better and longer-lasting protection than the current corona vaccines

Researchers at the Leiden University Medical Center (LUMC) have made a MERS corona vaccine with the entire virus instead of just the spike protein. The candidate vaccine provides strong protection against the MERS coronavirus in a mouse model. This strategy may provide better and longer-lasting protection than the current corona vaccines.

Long before the corona crisis, virologist Marjolein Kikkert and colleagues discovered that all coronaviruses contain a protein that is essential for the virus to multiply in our body. This protein also ensures that part of our immune system is suppressed, making it easier for the virus to do its thing. In Nature Communications the researchers write that coronaviruses in which subtle changes have been made to this protein offer very good protection against infections with the normal coronavirus in a mouse model. This makes the modified virus a potential new vaccine candidate.

Fully immune after one vaccination
This concept in itself is not new. There are already several vaccines that use weakened virus particles, such as those for yellow fever, mumps and measles. “The virus particles are usually weakened by multiplying them many times in cultured cells or laboratory animals, which causes changes in the viral genome and they no longer cause disease,” says Kikkert. “In this case, we made a very specific modification in the genome. As a result, the virus was no longer pathogenic and gave the immune system the opportunity to respond more optimally and build up protection.” According to Kikkert, this is because the modified virus can continue to multiply for a while and no longer suppresses our immune system. And that worked well. “After just 1 vaccination, mice were completely immune.”

MERS and SARS: 2 different coronaviruses
In their study, the researchers used the MERS coronavirus, which has been responsible for several outbreaks in Saudi Arabia since 2012. The virus is different from the coronavirus that caused the corona crisis in 2020 (SARS-CoV-2), but they are very similar.

Superior vaccine
According to Kikkert, a vaccine with a weakened virus probably provides better and longer protection than the current corona vaccines. “The immune system gets the chance to ‘see’ all aspects of the virus. In addition, in this specific way the entire arsenal that our immune system has in house, and in particular the innate immune response, is better activated. This happens much less with all current vaccines that only contain the spike protein.”

Why was such a vaccine not used earlier? “Although this vaccine strategy is often superior, it also carries safety risks. This can cause problems, especially in people with a weakened immune system. The development of these types of vaccines therefore requires even more safety tests, and therefore takes longer,” says Kikkert.

Does it also work for SARS-CoV-2?
The now well-known SARS coronavirus contains the same protein as the MERS virus. “We are now investigating whether the same ‘trick’ also works for this virus,” says Kikkert. With this research, they also learn more about exactly how coronaviruses work. “This knowledge is essential to manage the general ‘coronavirus problem’ in a sustainable way.”

A possible new corona vaccine is therefore definitely not too late, says Kikkert. “The SARS-CoV-2 virus and other variants will continue to plague humanity for now. As with the flu virus, it is important to protect the population against serious outbreaks.” The current corona vaccines have a relatively very temporary effect and regular ‘boosting’ is required. “A vaccine with a weakened virus may work longer, so that instead of every season, you may have to get a repeat shot every 5 years.”

Bron: LUMC