Scientists have developed a protein-based COVID-19 vaccine candidate that mimics the shape of the virus to trigger a robust antibody response in animals.
In the study published in the journal ACS Central Science, the researchers immunized mice with nanoparticles that mimic SARS-CoV-2, the virus that causes COVID-19, by displaying multiple copies of the receptor binding domain (RBD) antigen.
Most protein-based vaccines train the immune system to recognize the RBD, part of the SARS-CoV-2 spike protein, which the virus uses to invade and infect human cells.
The spike protein binds to the ACE-2 receptor on the surface of the host cell, which acts as a gateway for virus entry.
However, not all vaccines elicit both antibody and T-cell responses, both of which are believed to be important for longer-lasting immunity.
The researchers from the University of Chicago, USA, had previously developed a tool for delivering vaccines called polymersomes — self-assembling, spherical nanoparticles that can encapsulate antigens and adjuvants — and then release them into immune cells.
Adjuvents are auxiliary molecules that enhance the immune response.
Polymersomes cause robust T-cell immunity, the researchers said.
The team wondered if they could further enhance the antibody response by manipulating the nanoparticles to mimic viruses by displaying multiple copies of the RBD on their surface.
The researchers made polymersomes similar in size to SARS-CoV-2 and decorated them with lots of RBDs.
After characterizing the nanoparticles in the lab, they injected them into mice, along with separate polymersomes containing an adjuvant, at two doses three weeks apart.
For comparison, they immunized another group of mice with polymersomes that encapsulated the RBD, along with the nanoparticles containing the adjuvant.
Although both groups of mice produced high levels of RBD-specific antibodies, only the surface-decorated polymersomes generated neutralizing antibodies that prevented SARS-CoV-2 infection in cells.
Both the surface-decorated and encapsulated RBDs elicited robust T-cell responses, the researchers said.
While the new vaccine has yet to be tested for safety and efficacy in humans, it could have advantages over mRNA vaccines in terms of widespread distribution in resource-limited areas, they said.
That’s because the surface-decorated polymersomes are stable and active for at least six months with refrigeration, the researchers said.
In contrast, mRNA vaccines require storage at sub-zero temperatures, she added.
(This story was not edited by NewsMadura staff and was generated automatically from a syndicated feed.)