Comprehensive Flow Cytometry Profiling of the Immune System in COVID-19 Convalescent Individuals

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.

High baseline expression of IL-6 and IL-10 decreased CCR7 B cells in individuals with previous SARS-CoV-2 infection during BNT162b2 vaccination

“…In the case of IL-6, it is thought that this pro-inflammatory cytokine could be part of an innate inflammatory response that precedes an adaptive response in natural infection, including SARS-CoV-2 infection ( 24 , 25 ). Thus, the basal concentration is higher in individuals with the previous disease ( Figure 4 ), i.e., it could be related to an earlier induction of an adaptive response, promoting a rapid humoral reaction mediated by the differentiation and proliferation of B cells ( 24 ), and therefore with the higher concentration of antibodies in these same individuals.…”

Cellular and Humoral Immunity and Infection Responses to SARS-CoV-2:Immune Biomolecular Mechanisms by Case Study within SARS-CoV-2 Pathogenesis and Other Infections

“…Helper T cell Historically T cells were classified as TH1 and/or TH2 types or rather CD4 + and CD8 + with HIV infection allowed increased understanding CD4+ receptor mediated entry some 30 years ago now, however between 2000-2014 discoveries and classification of chemokines as predominant homing ligands and receptors occurred of key relevance to the overall context of T cell development, profileration and also effector functions. Gil analysis comparing a control v covid group (=51) within recovered COVID-19 individuals to demonstrate a significant cluster at 10 months following recovery of CD4 + CD45RA -CCR4 -CCR10 -CD27 + CCR6 -CXCR3 + CD127 + T cells inferring that there is a response within the circulating TFH1, plasmablast, and follicular dendritic cells (foDC) axis of note showing that these TFH1 cells within the SARS-CoV-2 group did express ICOS + and PD-1+ which is relevant as as TFH and B lymphocyte impairment within follicular zones or extra-follicular areas outside the GC can occur [9] .…”

“…Technological advancement since 2017 has also allowed greater phenotypic analysis and therefore it is clearer now that SARS-CoV-2 proteins do have different host roles with M protein vital for assembly spike protein S for receptor entry, N protein but also E protein a potential pore forming protein [5,6]. Single cell RNA sequencing (scRNA-Seq), spectral flow cytometry (FACS) and mass cytometry (CyTOF) can detect markers enabling phenotypic analysis of all immune cell subsets [7][8][9][10]. SARS-CoV-2 infects cells via respiratory pathways and type II pneumocytes using angiotensin converting enzyme 2 (ACE-2) as the predominant receptor for entry [11] Disruption and infection of type II pneumocytes expressing ACE2 occurs through phospholipid membranes.…”

Innate and Adaptive Immunity during SARS-CoV-2 Infection: Biomolecular Cellular Markers and Mechanisms

“…Analyses have confirmed that M protein is vital for assembling, S protein is for cellular receptor entry, and N and E proteins appear to be potential pore forming proteins [ 13 , 14 ]. Single cell RNA sequencing (scRNA-Seq), spectral flow cytometry (FACS), and mass cytometry (CyTOF) can detect markers enabling phenotypic analysis of all immune cell subsets [ 15 , 16 , 17 , 18 ]. It is noteworthy that antibody proteins involved in testing for SARS-CoV-2 infections have variable factors and human antibody concentrations.…”