UK researchers identify T-cell targets for future COVID vaccines

Immunity against COVID-19 is a complex picture, and while there is evidence of decreased antibody levels six months after vaccination, T-cells are also believed to play an important role in providing protection.

University College London (UCL) researchers screened 731 healthcare workers at two London hospitals during the first wave of the COVID-19 pandemic, and found that many had not tested positive despite possible exposure to the original coronavirus.

They found that, while a subset of workers did not generate antibodies or test positive with PCR tests, they still produced a large and widespread T-cell response following potential exposure.

This suggests that rather than workers avoiding exposure to the coronavirus, the T-cells had cleared the virus before there were any symptoms or a positive test result – a so-called “abortion infection”, the researchers said.

“We know that some individuals remain uninfected despite potential exposure to the virus,” said study lead author Leo Swadling, which was published in the science journal Nature.

“What is really informative is that the T-cells found in these individuals, where the virus has failed to establish a successful infection, preferentially target the different regions of the virus seen after infection.”

Current vaccines, which provide high protection against serious disease but do not completely prevent transmission or re-infection, target the spike protein of the coronavirus.

In contrast, T-cell responses recognized and targeted the abortive infection rather than “replication proteins” in the UCL study.

The researchers said that while such T-cells were associated with protection against detectable infection, they alone were not necessarily sufficient for protection, and the study did not look at whether people at re-exposure had protection.

He said replication proteins are minimally altered in coronaviruses by mutation, and that exposure to other coronaviruses may be one reason why few healthcare workers were able to mount such accelerated T cell responses.

This also means that a vaccine targeting these proteins in addition to the spike protein should currently work against a broad range of coronaviruses, including the dominant delta variant, the researchers said.

“This is a strong argument for the inclusion of these proteins to complement the spike in the next generation of vaccines,” Swadling told reporters.

This story has been published without modification in text from a wire agency feed.