A study published in the journal Nature by British scientists on unvaccinated medical staff at high risk of exposure to SARS-CoV-2 shows that some of them were able to eradicate the virus in very early stages of infection without even developing antibodies.
A similar phenomenon of sterile immunity before the development of antibodies has been seen in clinical trials of vaccines where immune protection appeared to begin around 5 days after the first dose, before neutralizing antibodies were developed.
Professors of the Medical School of the National and Kapodistrian University of Athens, Gikas Majorkinis and Thanos Dimopoulos (Rector of EKPA) report that the researchers found clear evidence of an immune response from the T-cells of the immune system which coincided with the time of exposure. The medical staff studied had higher levels of T-cells reactive to SARS-CoV-2 than their pre-pandemic counterparts.
This means that these T cells pre-existed but expanded during the treatment of the pandemic to healthcare staff after exposure but which was nevertheless sterilized by this immune response. The researchers showed that the proteins most likely to target these T cells are the coronavirus (polymerase) proliferation complex. The hypothesis is that these T cells have been trained in past infections by other coronaviruses.
As the proliferative complex is well conserved between coronaviruses, this results in a cross-immune response and the development of an immune memory covering a wider range of coronaviruses. This discovery puts the proliferation complex as an important candidate for the development of vaccines that will target a wider range of coronaviruses.
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