Wednesday, November 17, 2021  |
COVID-19 vaccines based on just a fragment of the Spike protein from SARS-CoV-2 may be more affordable for low- and middle-income countries to produce at scale than the many COVID-19 vaccines based on the entire Spike protein. However, the key Spike fragment that binds to people's cells—the receptor binding domain, or RBD—does not elicit a strong immune response on its own, especially in older individuals. To overcome this problem, researchers supported by the NIAID Adjuvant Discovery and Development Programs screened multiple vaccine adjuvants either alone or paired with aluminum hydroxide to find a formulation that would boost the immune response to the RBD protein the most. The investigators discovered that a vaccine combining the protein with two adjuvants, aluminum hydroxide and CpG (a short piece of DNA), worked best. Giving both young and aging mice this adjuvanted vaccine elicited neutralizing antibodies to SARS-CoV-2 at concentrations comparable to those induced by the Pfizer-BioNTech COVID-19 vaccine and protected aging mice from SARS-CoV-2 infection. The experimental vaccine also activated human immune cells donated by older adults. These findings, published Tuesday in Science Translational Medicine, suggest that the RBD protein formulated with aluminum hydroxide and CpG may represent a promising approach to expand the availability of effective COVID-19 vaccines for people of all ages worldwide.  |
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