Washington:
Scientists have created a protein-based COVID-19 vaccine candidate that mimics the shape of the virus to trigger robust antibody response in animals.
In the study published in the journal ACS Central Science, the researchers immunised mice with nanoparticles that mimic SARS-CoV-2, the virus that causes COVID-19, by displaying numerous copies of the receptor binding domain (RBD) antigen.
Most protein-based vaccines train the immune technique to recognise the RBD, a portion of the SARS-CoV-2 spike protein, which the virus utilizes to enter and infect human cells.
The spike protein binds to the ACE-2 receptor on host cell surfaces, that acts as a gateway for the entry of the virus.
However, not all vaccines elicit each antibody and T cell responses, each of which are believed to be essential for longer-lasting immunity.
The researchers from the University of Chicago, US, had previously created a vaccine delivery tool referred to as polymersomes — self-assembling, spherical nanoparticles that can encapsulate antigens and adjuvants — and then release them inside immune cells.
Adjuvents are helper molecules that increase the immune response.
Polymersomes trigger robust T cell immunity, the researchers mentioned.
The group wondered if they could additional increase the antibody response by engineering the nanoparticles to mimic viruses by displaying numerous copies of the RBD on their surfaces.
The researchers made polymersomes that had been related in size to SARS-CoV-2 and decorated them with numerous RBDs.
After characterising the nanoparticles in lab, they injected them into mice, along with separate polymersomes containing an adjuvant, in two doses that had been 3 weeks apart.
For comparison, they immunised yet another group of mice with polymersomes that encapsulated the RBD, along with the nanoparticles containing the adjuvant.
Although each groups of mice created higher levels of RBD-precise antibodies, only the surface-decorated polymersomes generated neutralising antibodies that prevented SARS-CoV-2 infection in cells.
Both the surface-decorated and encapsulated RBDs triggered robust T cell responses, the researchers mentioned.
Although the new vaccine nevertheless demands to be tested for security and efficacy in humans, it could have benefits more than mRNA vaccines with regard to widespread distribution in resource-restricted regions, they mentioned.
That is mainly because the surface-decorated polymersomes are steady and active for at least six months with refrigeration, the researchers mentioned.
In contrast, mRNA vaccines demand subzero temperature storage, they added.
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