In a new study, researchers found new targets for COVID-19 vaccines and tests that go beyond the current focus on COVID antibodies.
The study was designed to focus on T cells, as opposed to the more common focus on B cells, and it has strongly increased the understanding of how the immune system’s T cells mount a response to SARS-Co-V2, the coronavirus that causes COVID-19.
The research was conducted by a team at Atlantic Health System.
B cells and T cells are white blood cells that each take a different approach to fight infection from bacteria and viruses.
B cells produce antibodies to the foreign invader and form memory cells that remember the same pathogen for faster antibody production in future infections.
T cells can develop into memory cells, just as B cells can, but they do not produce antibodies. T cells directly kill virus-infected cells and are known as “killer T cells.”
Sometimes people with a very vigorous T cell immune response will be protected from an invader even though they produce low amounts of antibodies from B cells.
The team says killer T cells clear viral infections and may be necessary for long-term immunity to coronaviruses.
To conduct the study, the team drew blood samples from 35 recovered COVID-19 patients who volunteered for the study.
The blood samples were sent to TScan Therapeutics, where scientists used their core T cell target identification technology to examine patients’ T cells, in order to determine which parts of the virus these cells were targeting.
They found that patients’ T cells recognize the same, relatively small number of targets that are unique to COVID-19 and don’t tend to mutate.
These findings pave the way for diagnostic tests that detect COVID immunity based on T cells instead of antibodies. Interestingly, TScan also found that 90% of T cells recognize targets outside of the spike protein.
The spike protein has been the focus of the development of COVID vaccines, including those now in Phase 3 trials.
Research has shown that this approach, which is targeted at generating neutralizing antibodies rather than T cells, may not be sufficient to induce long term immunity.
The new discoveries suggest that second-generation vaccines will need to incorporate T cell targets if they are to generate lasting COVID-19 immunity.
The team says COVID-19 vaccine development efforts have been progressing rapidly, but to date remain largely focused on causing a neutralizing antibody response against the virus’ spike protein.
An increasing body of evidence suggests that a T cell response is important in the defense against COVID-19, and T cells that recognize coronaviruses tend to persist much longer than antibodies.
By identifying a short list of the most critical T cell targets, the researchers have provided a roadmap to the development of follow-on vaccines.
One author of the study is Angela Alistar, MD, medical director of GI Medical Oncology and the Breakthrough Treatment Center.
The study is posted on medRxiv.
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