New research has shown that potential vaccines should not be affected by how SARS-CoV-2, the virus that causes COVID-19, has changed to date.

Most vaccines under development worldwide have been modeled on the original ‘D-strain’ of the virus, which were more common amongst sequences published early in the pandemic. Since then, the virus has evolved to the globally dominant ‘G-strain’, which now accounts for about 85% of published SARS-CoV-2 genomes. There had been fears the G-strain, or ‘D614G’ mutation within the main protein on the surface of the virus, would negatively impact on vaccines under development. However, researchers from the Commonwealth Scientific and Industrial Research Organization (CSIRO Canberra, Australia) have found no evidence that the change would adversely impact the efficacy of vaccine candidates. Their findings were based on a study in which CSIRO, Australia’s national science agency, tested blood samples from ferrets vaccinated with Inovio Pharmaceuticals’ INO-4800 candidate against virus strains that either possessed or lacked this ‘D614G’ mutation.

“Most COVID-19 vaccine candidates target the virus’ spike protein as this binds to the ACE2 receptors in our lungs and airways, which are the entry point to infect cells,” said Dr. S.S. Vasan, CSIRO’s Dangerous Pathogens Team Leader and the senior author of the paper. “Despite this ‘D614G’ mutation to the spike protein, we confirmed through experiments and modeling that vaccine candidates are still effective. “We’ve also found the G-strain is unlikely to require frequent ‘vaccine matching’ where new vaccines need to be developed seasonally to combat the virus strains in circulation, as is the case with influenza.”

Dr. Alex McAuley, CSIRO research scientist and first author of the paper, said ferrets vaccinated with INO-4800 demonstrated a strong immune response. “We found that ferrets vaccinated with Inovio Pharmaceuticals’ candidate developed a good B-cell response in terms of neutralizing antibodies against SARS-CoV-2 strains, which is important for the short-term efficacy of a vaccine,” Dr. McAuley said. “We are also studying the T-cell response which is important for long-term efficacy.”

The modeling enabled the interactions between the vaccine and virus to be simulated and visualized, according to Dr. Michael Kuiper, co-author and Team Leader of the Molecular & Materials Modeling Group at CSIRO’s Data61.

“If we understand the process of a viral infection, we paint a picture of its vulnerabilities. Bio-molecular modeling helps us to do this,” Dr. Kuiper said. “By visualizing molecular structure, we were able to support the study’s inference that the immune response generated by the vaccine candidate is equally effective against both D- and G- strains of SARS-CoV-2.”

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