Scientists report that a substance can increase mice's immune response to experimental COVID-19 vaccine by 25 times compared to vaccine injection alone.

ironically, some vaccines need their own "boosters". An ingredient known as an adjuvant is added to the vaccine to help elicit a stronger immune response and better train the body to fight pathogens. Scientists report that a substance can increase mice's immune response to experimental COVID-19 vaccine by 25 times compared to vaccine injection alone.

A new paper published today (August 31, 2022) in the journal ACS Infectious Diseases describes the details of the study.

Although the first COVID-19 vaccines authorized in the United States use state-of-the-art mRNA gene technology, the proven strategy of using pathogen proteins can produce vaccines that are cheaper to manufacture and easier to store. So far, the U.S. Food and Drug Administration (FDA) has approved only one protein vaccine against SARS-CoV-2 produced by Novavax. However, many of the currently available vaccinations for other diseases rely on proteins or fragments of proteins, which contain adjuvants to improve their effectiveness.

Scientists have discovered that molecules derived from α-galactose glyceramide (αGC), a compound from marine sponge, can act as an adjuvant. They work by stimulating a small population of immune cells, which are very important to defend against viral infections in the body. Rui Luo, Zheng Liu and their colleagues have designed a version of αGC to significantly improve the immune response caused by a protein-based COVID-19 vaccine.

This group made four analogues of αGC. They added each to an experimental vaccine containing SARS-CoV-2 spike protein, which uses spike protein to infect cells. The mice were injected three times in 29 days, and the researchers followed their immune response until day 35.

To measure the effect of the adjuvant, scientists carefully studied various aspects of immune function, including two ways in which the immune system eliminates pathogens: through T cells (directly killing diseased cells) and antibodies (catching the immune proteins that invade microorganisms).

None of these four substances improves the T cell response, but they all make the immune system produce antibodies that are much more capable of interfering with the virus. A similar substance called αGC-CPOEt gave birth to antibodies with maximum neutralization capacity—25 times larger than a vaccine without adjuvant.

According to the researchers, these results suggest that αGC-CPOEt deserves further investigation as a potential adjuvant to combat COVID-19 and other infectious diseases.