SARS-CoV-2 specific T-cell immunity in COVID-19 convalescent patients and unexposed controls measured by ex vivo ELISpot assay

• Published in: Clinical microbiology and infection Vol. 27; no. 7; pp. 1029 - 1034
• Main Authors: Cassaniti, Irene, Percivalle, Elena, Bergami, Federica, Piralla, Antonio, Comolli, Giuditta, Bruno, Raffaele, Vecchia, Marco, Sambo, Margherita, Colaneri, Marta, Zuccaro, Valentina, Benazzo, Marco, Robotti, Carlo, Calastri, Anna, Maiorano, Eugenia, Ferrari, Alessandro, Cambiè, Giuseppe, Baldanti, Fausto
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2021; European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd
• Subjects: ELISpot; Humoral response; Neutralizing antibodies; Original; SARS-CoV-2; T-cell response; SARS-CoV-2; Humoral response; Neutralizing antibodies; ELISpot; T-cell response
• ISSN: 1198-743X; 1469-0691; 1469-0691
• DOI: 10.1016/j.cmi.2021.03.010

SARS-CoV-2 T-cell response characterization represents a crucial issue for defining the role of immune protection against COVID-19. The aim of the study was to assess the SARS-CoV-2 T-cell response in a cohort of COVID-19 convalescent patients and in a group of unexposed subjects. SARS-CoV-2 T-cell response was quantified from peripheral blood mononuclear cells (PBMCs) of 87 COVID-19 convalescent subjects (range 7–239 days after symptom onset) and 33 unexposed donors by ex vivo ELISpot assay. Follow-up of SARS-CoV-2 T-cell response was performed in ten subjects up to 12 months after symptom onset. The role of SARS-CoV-2 specific CD4 and CD8 T cells was characterized in a group of COVID-19 convalescent subjects. Moreover, neutralizing antibodies were determined in serum samples. In 14/33 (42.4%) unexposed donors and 85/87 (97.7%) COVID-19 convalescent subjects a positive result for at least one SARS-CoV-2 antigen was observed. A positive response was observed up to 12 months after COVID-19 infection (median 246 days after symptom onset; range 118–362 days). Of note, SARS-CoV-2 T-cell response seems to be mainly mediated by CD4 T cells. A weak positive correlation was observed between Spike-specific T-cell response and neutralizing antibody titre (p 0.0028; r2 = 0.2891) and positive SARS-CoV-2 T-cell response was observed in 8/9 (88.9%) COVID-19 convalescent subjects with undetectable SARS-CoV-2 neutralizing antibodies. Cross-reactive SARS-CoV-2 T-cell response in uninfected patients may be due to previous infections with other common coronaviruses. Our data suggest that long-term SARS-CoV-2 T-cell response might accompany a waning humoral response.