Studies carried out by The Pirbright Institute and the University of Oxford have shown that Oxford’s new potential vaccine against COVID-19, named RBD-SpyVLP, produces a strong antibody response in mice and pigs. Researchers say this could be vital information to further development of vaccines.
“Although this type of vaccine is not a competitor for the first wave of vaccines, it is hoped that it will be useful as a standalone vaccine or as a booster for individuals primed with a different COVID-19 vaccine,” Pirbright said in a release.
Vaccine development has progressed at an unprecedented pace, with the World Health Organization (WHO) reporting 173 vaccine candidates in preclinical trials, 64 that have moved to human clinical trials and three that have received temporary authorization for use in the UK, the release said.
The Oxford-produced RBD-SpyVLP vaccine candidate contains part of the SARS-CoV-2 spike protein called the receptor binding domain (RBD), which a range of protective neutralizing antibodies can bind to in a way that blocks infection, researchers explained.
The RBD is attached to a virus-like particle (VLP) that contains no genetic material using Oxford’s SpyTag/SpyCatcher technology, which acts like a protein ‘superglue.’ This was shown to generate a greater antibody response in mice than administering the RBD alone, the release said. The vaccine was also tested in pigs as a large animal model to establish if different dosages would affect the immune response.
The research, published in Nature Communications, demonstrated that RBD-SpyVLP produces a strong neutralizing antibody response. The study also compared samples taken from the nose and mouth of vaccinated pigs and found SARS-CoV-2 specific antibodies present.
Pirbright reports this is a promising discovery since antibodies at the site of entry for SARS-CoV-2 could be important for providing robust protection. However, no difference was found in the magnitude of antibody response when comparing vaccine dose levels, the article said. This suggests the smaller dose tested, which is the same as intended for human administration, may provide equal protection to larger doses or that even lower doses of the vaccine could be effective.
“These results offer valuable insights into the kind of immune responses that the RBD-SpyVLP vaccine could trigger in humans,” said Simon Graham, a professor who led the pig studies at Pirbright. “Further understanding the dose required to elicit a strong immune response is key for the progression of vaccine development and scaling up for manufacture.”
The researchers evaluated the vaccine’s stability and discovered RBD-SpyVLP is highly resilient, stable at room temperature and can be freeze dried without losing its power to immunize. These properties would facilitate global distribution and reduce dependence on cold chains for transport and storage.
“These latest results into the immune response from the Oxford COVID-19 vaccine candidate, RBD-SpyVLP, are both exciting and promising. By drawing on scientific knowledge from multiple disciplines, researchers have collectively demonstrated the ability to improve and advance development of the vaccine,” said Melanie Welham, professor and executive chair at the Biotechnology and Biological Sciences Research Council, part of UK Research and Innovation.
The article “A COVID-19 vaccine candidate using SpyCatcher multimerization of the SARS-CoV-2 spike protein receptor-binding domain induces potent neutralising antibody responses” appears in Nature Communications.
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