Respuesta inmunitaria frente a SARS CoV-2 tras infección natural y tras vacunación

Abstract

This dissertation is based on the comparative analysis of the different elements of the immune response (both innate and adaptative), triggered against SARS-CoV-2 after natural infection and after vaccination. Such analysis is based on two cohorts studied at the Hospital Universitario Marqués de Valdecilla. To this end, the main epidemiological characteristics, immunological parameters and in-hospital evolution of 155 COVID-19 positive patients were first analysed. The patients were divided into two groups (mild and moderate-severe), according to their oxygen therapy requirements at admission. Moreover, the immune response of 52 healthcare professionals after being vaccinated with a double dose of the BNT162b2 Pfizer-BioNTech vaccine was also analysed. On the one hand, it was observed that patients classified as moderate-severe were noted to be older and had significantly higher levels of ferritin, D-dimer, C-reactive protein, troponin, IL-6, neutrophils and depleted CD8 T lymphocytes, as well as lymphopenia and reduced levels of Th1 lymphocytes and Treg cells. Conversely, patients classified in the mild group had significantly higher levels of non-classical monocytes, innate lymphoid cells and NK cells in peripheral blood. Furthermore, those classified as moderate-severe required more chronic treatment on admission and were more often treated in-hospital. On the other hand, regarding the vaccinated group of healthcare workers, an increase in memory Th1 helper lymphocytes, peripheral follicular T helper memory cells and memory B lymphocytes with isotype change was observed after the administration of the second dose of the vaccine. There was also evidence of an activation of the immune system by means of a specific anti-S T response.