Abstract
SARS-CoV-2 has infected more than 200 million people worldwide, with more than 4 million associated deaths. Although more than 80% of infected people develop asymptomatic or mild COVID-19, SARS-CoV-2 can induce a profound dysregulation of the immune system. Therefore, it is important to investigate whether clinically recovered individuals present immune sequelae. The potential presence of a long-term dysregulation of the immune system could constitute a risk factor for re-infection and the development of other pathologies. Here, we performed a deep analysis of the immune system in 35 COVID-19 recovered individuals previously infected with SARS-CoV-2 compared to 16 healthy donors, by flow cytometry. Samples from COVID-19 individuals were analysed from 12 days to 305 days post-infection. We observed that, 10 months post-infection, recovered COVID-19 patients presented alterations in the values of some T-cell, B-cell, and innate cell subsets compared to healthy controls. Moreover, we found in recovered COVID-19 individuals increased levels of circulating follicular helper type 1 (cTfh1), plasmablast/plasma cells, and follicular dendritic cells (foDC), which could indicate that the Tfh-B-foDC axis might be functional to produce specific immunoglobulins 10 months post-infection. The presence of this axis and the immune system alterations could constitute prognosis markers and could play an important role in potential re-infection or the presence of long-term symptoms in some individuals.
Highlights
Up to now, the COVID-19 pandemic has affected more than 230 million people and has claimed the lives of more than 4.8 million people worldwide
Blood samples and data questionnaires of donor characteristics during COVID-19 from SARS-CoV-2 convalescent donors were collected from June to December 2020, and healthy controls were collected from January to February 2021, at the General University Hospital Gregorio Marañón, Spain
Ninety-four percent of subjects were never hospitalised for COVID-19; 6% were hospitalised (n = 2), but none required intensive care unit (ICU) care
Summary
The COVID-19 pandemic has affected more than 230 million people and has claimed the lives of more than 4.8 million people worldwide. Infected individuals range from asymptomatic to presenting with severe symptoms, with a median fatality rate of 0.27% [1]. More than 80% of infected people are asymptomatic or develop mild symptoms [2]. The virus triggers an exacerbated immune response that goes from protecting to attacking the infected individual. An increase in pro-inflammatory cytokines, T cell activation, and T cell exhaustion was observed [4,5,6]. Decreases in regulatory cells, T-cell cytotoxicity, and T cells’ polyfunctionality were observed [5, 7,8,9]. Even when deeper dysregulation is linked to severe disease, it was observed that COVID-19 individuals, even with mild symptoms, present immune dysregulation [10]
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