Studies carried out in the MRC Human Immunology Unit (MRC HIU) in collaboration with the Pirbright Institute have shown that a new potential vaccine against COVID-19, named RBD-SpyVLP, produces a strong antibody response in mice and pigs, providing vital information for the further development of the vaccine. 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.
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 neutralising antibodies can bind to in a way that blocks infection. The RBD is attached to a virus-like particle (VLP) that contains no genetic material using Oxford’s SpyTag/SpyCatcher technology, a kind of protein ‘superglue’. This was shown to generate a greater antibody response in mice than administering the RBD alone. Pirbright researchers tested the RBD-SpyVLP vaccine 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 neutralising antibody response. The study also examined samples taken from the nose and mouth of vaccinated pigs and found SARS-CoV-2 specific antibodies were present. This is a promising finding since antibodies at the site of entry for SARS-CoV-2 could be important for providing robust protection. Interestingly, no difference was found in the magnitude of antibody response when comparing vaccine dose levels. This suggests that 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.