Vaccine Additive Strengthens Immune Response, Offers Possibilities for Universal Flu Vaccine

Adding a vaccine additive called an adjuvant to a vaccination enhances the body’s response to the vaccine, and may offer possibilities for a universal flu vaccine, according to an Emory Vaccine Center study.¹

Investigators found that both rookie and veteran elements of the immune system responded much more efficiently to the presence of the virus when the adjuvant was added.¹

“We saw that an adjuvant makes it possible to efficiently engage both memory and naive B cells, expanding the repertoire of the antibody immune response to influenza,” said Ali Ellebedy, PhD, an author of the study.²

The study, which was published in the Proceedings of the National Academy of Sciences, consisted of 50 healthy young adults who all had been previously exposed to various flu viruses and vaccines. Two doses of the adjuvant AS03 to the H5N1 avian influenza virus vaccine were applied to the group, and the results were compared with those from a non-adjuvanted vaccine.

The first dosage affected pre-existing memory B cells and directed cross-reactive antibodies to attack the virus stem. The second dosage affected strain-specific naïve B cells and encouraged antibodies to attack the virus head. Together, both pre-existing memory B cells and naïve B cells contributed to a more efficient immune response.¹

Previous research had noted that, faced with an unfamiliar flu virus, the immune system would produce antibodies that could neutralize a much wider range of viruses. These antibodies skewed towards the “stem” of the viral hemagglutinin protein, as opposed to the “head,” as the stem does not mutate much and could still be recognized by the antibodies.²

The adjuvant trial demonstrates that an efficient immune response is tied to the recognition of a flu virus’s stem. If the immune system recognizes this but not the head, it can still launch antibodies towards the virus and negate it.

Such results open up new avenues for the development of a universal flu vaccine. But vaccine designers are already considering how to use adjuvants to optimize the immune responses against severe acute respiratory syndrome coronavirus 2 in order to overcome the body’s unfamiliarity with the virus. A vaccine that could induce a strong response from both memory and naïve B cells has the potential to be a strong alternative to other developmental mRNA-based vaccines.

As such, the adjuvant AS03 will be made available for COVID-19 vaccine trials, according to its manufacturer, GlaxoSmithKline.²

References

1. Ellebedy AH, Nachbagauer R, Jackson KJL, et al. Adjuvanted H5N1 influenza vaccine enhances both cross-reactive memory B cell and strain-specific naïve B cell responses in humans. Proceedings of the National Academy of Sciences of the United States of America. July 13, 2020. https://doi.org/10.1073/pnas.1906613117
2. Eastman, Q. Vaccine additives can enhance immune flexibility—implications for flu and SARS-CoV-2. News Release. Emory University. Published July 13, 2020. Accessed July 20, 2020. https://news.emory.edu/stories/2020/07/H5N1_adjuvants_ahmed/index.html