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A protein particle hidden within the SARS-CoV-2 virus could lead to longer-lasting, more protective vaccines for COVID-19.

Scientists from La Trobe University and Kumamoto University in Japan have discovered that the body's immune system strongly reacts to an internal protein from SARS-CoV-2, the virus that causes COVID-19, which mutates less frequently than the surface-spike protein currently targeted by vaccines.

New research in Nature Communications shows that these protein particles, known as peptides, appear on the surface of infected cells via an immune molecule called HLA-C, which killer T cells then use to identify and eliminate infection.

La Trobe University lead researcher Distinguished Professor Stephanie Gras, Deputy Director of the La Trobe Institute for Molecular Science (LIMS), said the discovery could open the way for the development of new vaccines and treatments that offer protection across multiple strains of the SARS-CoV-2 virus.

"Currently, vaccines target the spike proteins that decorate the surface of the virus—but they mutate frequently as they are constantly under pressure by our immune cells, which means we might need a new vaccine for each new variant," Professor Gras said.

"We found that the killer T cells, which also fight infection, can be activated by a protein that forms a part of the shell that protects the virus's genetic material, like the yolk of an egg.

"Because this protein is inside the virus, it mutates much less frequently—knowledge which could guide the development of vaccines and therapeutics that are still effective as the virus evolves."

Professor Gras said the development of a longer-lasting vaccine could mean that people would need fewer booster vaccines to fight COVID, and help protect against the development of long COVID.

"The more people get vaccinated, the more we're protecting the population, which helps to reduce the virus's death toll and the impact of the infection itself," Professor Gras said.

"But there is more than just COVID—we now know that about 10% of the population is impacted by long COVID and the more you catch the virus, the more likely you can develop long COVID."

Professor Gras, Dr. Demetra Chatzileontiadou, Dr. Janesha Maddumage, and Ph.D. candidate You Min Ahn led the research team at LIMS and La Trobe University's School of Biomedicine, Agriculture and Environment (SABE).

The research was done in collaboration with Associate Professor Chihiro Motozono and Yoshihiko Goto from the Joint Research Center for Human Retrovirus Infection at Kumamoto University in Japan, with data collection by the Australian Synchrotron.