Fighting a SARS-CoV-2 infection is not solely the responsibility of antibodies, the proteins that adhere to the virus’s surface to prevent it from entering cells or mark it for destruction. Effective viral control appears to be exerted to a large extent by T lymphocytes, immune system cells capable of eliminating the cells that the coronavirus enters. A group of researchers led by immunologists Edécio Cunha Neto and Jorge Kalil Filho and geneticist Mayana Zatz, all from the University of São Paulo (USP), verified the importance of T lymphocytes in a small study carried out with two pairs of identical twins, all infected at least once by the novel coronavirus. Identical twins should produce a similar immune response since they have the same genes. But that did not turn out to be the case. In one of the pairs, one twin caught COVID-19 a second time and experienced more severe symptoms—it was probably a reinfection, although it is not possible to rule out the possibility that the virus had remained in the body since the first infection. When analyzing the immune response of the four participants, the research team found that the T lymphocytes of the individual who had the disease for the second time (a healthcare professional) performed worse than the other three participants (medRxiv, March 28). “Our work suggests that an effective immune response against SARS-CoV-2 by specific T lymphocytes is key to complete viral control and to preventing repeat infection or viral persistence,” the authors wrote.
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