Japanese scientists move closer to developing single vaccine against all coronaviruses

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Japanese scientists have developed a vaccination approach that could lead to protection against a wide range of coronaviruses – not just the one that causes Covid-19.

Developing a more widely applicable vaccine has been a major goal of the researchers, as some existing vaccines have been shown to be less effective against emerging variants of Sars-CoV-2.

The strategy of researchers in Japan could potentially be used to provide protection even against new pandemics caused by different coronaviruses. Their strategy, described in an article recently published in the Journal of Experimental Medicine, involved genetically modified Sars-CoV-2 proteins.

At the heart of the research was the virus spike protein, which includes the receptor binding domain that attaches to a receptor on human cells called ACE2. Once the spike protein attaches to ACE2, the virus enters cells and multiplies.

Part of the receptor binding domain, known as the head region, is highly specialized, but another section, the central region, is in contrast similar in several coronaviruses.

Vaccination-induced immunity usually involves the production of antibodies against the specialized head region, making the protection very specific to a particular coronavirus.

To get around this problem, researchers at Osaka University in Japan genetically modified the receptor binding domain of the spike protein so that sugar molecules were attached to the head region.

Mice exposed to these modified proteins produced a greater proportion of antibodies against the central region instead of, as would normally be the case, the head region.

The antibodies they made were a type of what scientists call largely neutralizing antibodies, and in tests they were found to neutralize not only Sars-CoV-2, but also Sars-CoV-1, which caused the 2002 Sars epidemic.

They were also effective against three similar coronaviruses in pangolins and bats, an important finding because coronaviruses currently found in some animals could, in the future, infect humans.

“Since previous coronavirus outbreaks such as Sars-CoV-1 and Mers-CoV [Middle East Respiratory Syndrome] occurred due to zoonotic coronaviruses crossing the species barrier, the potential for similar viruses to emerge in the future poses a significant threat to global public health, even in the face of effective vaccines against current viruses, ”a researcher involved in the study, Professor Tomohiro Kurosaki, from the WPI Immunology Frontier Research Center at Osaka University in Japan, said.

How some current Covid-19 vaccines are less effective against emerging variants of Sars-CoV-2, particularly the Delta variant, demonstrates that the immunity they confer is highly specific.

Updated vaccines that cope with a wider variety of variants are in development, but their production takes time and people then need to be revaccinated, so a universal coronavirus vaccine would be preferable.

While researchers in Japan focused on antigens (foreign substances that stimulate an immune response) common to different coronaviruses, researchers in the United States, also working in mice, took a different approach.

In a study published in February, they described how mice could be immunized against a range of coronaviruses with a “mosaic vaccine” made up of several antigens.

Due to challenges such as ensuring that immunity is long-lasting and broad enough to deal with emerging diseases, scientists have predicted that it could take several years to develop a universal vaccine against the coronavirus.

Dr Andrew Freedman, an infectious disease specialist at Cardiff University in the UK, said he had not analyzed the latest study in mice, but that it was “probably realistic” to hope that ‘a universal vaccine against the coronavirus could be developed.

“There is almost certainly cross-immunity,” he said.

“We know you can get repeated coronavirus infections, so immunity is not perfect, but part of the immune response to a coronavirus will almost certainly give you cross-immunity to other coronaviruses. There are shared parts of coronaviruses. “

He warned, however, that with the latest study in mice, “there would be a long way to go” before such broad protection in humans can be created.

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Update: October 10, 2021 6:46 am