Researchers, including those from Stanford University in the United States, have developed a nanoparticle vaccine that elicits a virus-neutralizing antibody response even after a single dose.
The team said that the primary target for Covid-19 vaccines is the spike protein, which is necessary for SARS-CoV-2’s entry into cells.
For the study, published in the ACS Central Science journal, the team intended to explore a different approach: a vaccine consisting of multiple copies of the spike protein displayed on ferritin nanoparticles, in a mice-based experiment.
Ferritin is an iron storage protein found in many organisms that self-assembles into a larger nanoparticle.
For vaccine development, the researchers spliced spike protein and ferritin DNA together and then expressed the hybrid protein in cultured mammalian cells. The ferritin self-assembled into nanoparticles, each bearing eight copies of the spike protein trimer. The team purified the spike/ferritin particles and injected them into mice.
After a single immunization, mice produced neutralizing antibody titers that were at least two times higher than those in convalescent plasma from Covid-19 patients. It was significantly higher than those in mice immunized with the spike protein alone.
A second immunization 21 days later produced even higher antibody levels.
Although these results must be confirmed in human clinical trials, they suggest that the spike/ferritin nanoparticles may be a viable strategy for single-dose vaccination against Covid-19, the researchers said.
“Our goal is to make a single-shot vaccine that does not require a cold-chain for storage or transport. If we’re successful at doing it well, it should be cheap too,” said Kim, who is the Virginia and D. K. Ludwig Professor of Biochemistry.
“The target population for our vaccine is low- and middle-income countries,” he added.
Lead author Abigail Powell, a former postdoctoral scholar in the Kim lab said in the study: “This is really early stage and there is still lots of work to be done.”
He further added: “But we think it is a solid starting point for what could be a single-dose vaccine regimen that doesn’t rely on using a virus to generate protective antibodies following vaccination.”
