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INTRODUCTION: Although the adaptive immune responses to the CoronaVac vaccine are known, their dynamics in indigenous communities remain unclear. In this study, we assessed the humoral and cellular immune responses to CoronaVac (Sinovac Biotech Life Sciences, 2021 NCT05225285, Beijing, China), in immunized Brazilian indigenous individuals. METHODS: We conducted a prospective cohort study on indigenous Brazilian people between February 2021 and June 2021. Analyses of immune responses were carried out before (T1) and after a vaccination schedule was completed (T2). Demographic data were collected using a questionnaire. RESULTS: We initially included 328 patients; among them, 120 (36.6%) had no SARS-CoV-2 antibodies. Peripheral blood mononuclear cells (PBMCs) were collected from 106 patients during follow-up visits, of which 91 samples were analyzed by immunophenotyping assay to detect SARS-CoV-2-specific memory T-cell response. Post-vaccination, the levels of memory B-cells and Natural Killer T-lymphocytes increased. Bororó village residents, females, and Terena ethnic group members had higher levels of anti-spike IgG antibodies post-vaccination, whereas alcohol and tobacco users had lower concentrations. CONCLUSIONS: To our best knowledge, this was the first comprehensive assessment of antibody and T-cell responses against CoronaVac vaccination in indigenous patients. Our findings showed that antibody response and T-cell immunity against SARS-CoV-2 were present in most patients following the vaccination schedule.
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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus responsible for coronavirus 2019 (COVID-19), which was declared a pandemic in March 2020 by the World Health Organization due the rapid spread representing a global health crisis. The disease is characterized by a wide clinical spectrum ranging from asymptomatic forms until severe viral pneumonia, which can to evolve to severe acute respiratory syndrome, especially in elderly patients and/or with comorbidities. An efficient assembly of the immunological response of the patients becomes fundamental against SARS-CoV-2 infection and it has been demonstrating a significant relationship between the severity of the disease and expression profile of the immune cells and the levels of pro-inflammatory cytokines. This review aims to presents the main immunological mechanisms developed during the infection by SARS-CoV-2 in the evolution of the severe cases of COVID-19. The immune dysregulation of the Th1 cellular response standard, the instability in the production of neutralizing antibodies by plasma B cells, the difference in tropism of CD8+ T cells against virus proteins in early infection, late infection and reinfections, dynamic of alveolar macrophages and pulmonary innate lymphoid cells (TCR γδ) of the natural imune response and the high level of pro-inflammatory cytokines can determine the main cause of breath tissues damages and, consequently, a greater severity of the disease. Therefore, a complete understanding of the main immunological changes involved in SARS-CoV-2 infection can identify possible biomarkers in the evaluation of early prognosis of the severe cases of COVID-19, making possible better therapeutic success to the patients.