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ACS Appl Mater Interfaces ; 13(34): 40342-40353, 2021 Sep 01.
Article in English | MEDLINE | ID: covidwho-1366784


Sensitive point-of-care methods for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens in clinical specimens are urgently needed to achieve rapid screening of viral infection. We developed a magnetic quantum dot-based dual-mode lateral flow immunoassay (LFIA) biosensor for the high-sensitivity simultaneous detection of SARS-CoV-2 spike (S) and nucleocapsid protein (NP) antigens, which is beneficial for improving the detection accuracy and efficiency of SARS-CoV-2 infection in the point-of-care testing area. A high-performance magnetic quantum dot with a triple-QD shell (MagTQD) nanotag was first fabricated and integrated into the LFIA system to provide superior fluorescence signals, enrichment ability, and detectability for S/NP antigen testing. Two detection modes were provided by the proposed MagTQD-LFIA. The direct mode was used for rapid screening or urgent detection of suspected samples within 10 min, and the enrichment mode was used for the highly sensitive and quantitative analysis of SARS-CoV-2 antigens in biological samples without the interference of the "hook effect." The simultaneous detection of SARS-CoV-2 S/NP antigens was conducted in one LFIA strip, and the detection limits for two antigens under direct and enrichment modes were 1 and 0.5 pg/mL, respectively. The MagTQD-LFIA showed high accuracy, specificity, and stability in saliva and nasal swab samples and is an efficient tool with flexibility to meet the testing requirements for SARS-CoV-2 antigens in various situations.

Antigens, Viral/analysis , Biosensing Techniques/methods , Coronavirus Nucleocapsid Proteins/analysis , SARS-CoV-2/chemistry , Spike Glycoprotein, Coronavirus/analysis , Antibodies, Immobilized/immunology , Antibodies, Monoclonal/immunology , Antigens, Viral/immunology , Coronavirus Nucleocapsid Proteins/immunology , Fluorescence , Fluorescent Dyes/chemistry , Humans , Immunoassay/methods , Limit of Detection , Magnetite Nanoparticles/chemistry , Nasopharynx/virology , Phosphoproteins/analysis , Phosphoproteins/immunology , Quantum Dots/chemistry , Saliva/virology , Sensitivity and Specificity , Spike Glycoprotein, Coronavirus/immunology
Front Immunol ; 12: 700152, 2021.
Article in English | MEDLINE | ID: covidwho-1359189


Background: Mucosal-associated invariant T (MAIT) cells are considered to participate of the host immune response against acute severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection; however, single-cell transcriptomic profiling of MAIT cells in patients with COVID-19 remains unexplored. Methods: We performed single-cell RNA sequencing analyses on peripheral MAIT cells from 13 patients with COVID-19 and 5 healthy donors. The transcriptional profiles of MAIT cells, together with assembled T-cell receptor sequences, were analyzed. Flow cytometry analysis was also performed to investigate the properties of MAIT cells. Results: We identified that differentially expressed genes (DEGs) of MAIT cells were involved in myeloid leukocyte activation and lymphocyte activation in patients with COVID-19. In addition, in MAIT cells from severe cases, more DEGs were enriched in adaptive cellular and humoral immune responses compared with those in moderate cases. Further analysis indicated that the increase of cell cytotoxicity (killing), chemotaxis, and apoptosis levels in MAIT cells were consistent with disease severity and displayed the highest levels in patients with severe disease. Interestingly, flow cytometry analysis showed that the frequencies of pyroptotic MAIT cells, but not the frequencies of apoptotic MAIT cells, were increased significantly in patients with COVID-19, suggesting pyroptosis is one of leading causes of MAIT cell deaths during SARS-CoV-2 infection. Importantly, there were more clonal expansions of MAIT cells in severe cases than in moderate cases. Conclusions: The results of the present study suggest that MAIT cells are likely to be involved in the host immune response against SARS-CoV-2 infection. Simultaneously, the transcriptomic data from MAIT cells provides a deeper understanding of the immune pathogenesis of the disease.

COVID-19/immunology , Mucosal-Associated Invariant T Cells/immunology , SARS-CoV-2/immunology , Transcriptome/genetics , Base Sequence , COVID-19/pathology , Gene Expression Profiling , Gene Expression Regulation/genetics , Gene Expression Regulation/immunology , Humans , Lymphocyte Activation/genetics , Pyroptosis/physiology , Sequence Analysis, RNA , Severity of Illness Index , VDJ Exons/genetics