Rapid detection of SARS-CoV-2-specific memory T-cell immunity in recovered COVID-19 cases

Objectives: There is emerging evidence that SARS-CoV-2-specific memory T-cell responses are likely to provide critical long-term protection against COVID-19. Strategies to rapidly assess T-cell responses are therefore likely to be important for assessing immunity in the global population.

Methods: Here, we have developed a rapid immune-monitoring strategy to assess virus-specific memory T-cell responses in the peripheral blood of COVID-19 convalescent individuals. We validated SARS-CoV-2-specific memory T-cell responses detected in whole blood using in vitro expansion with SARS-CoV-2 proteins.

Results: T-cell immunity characterised by the production of IFN-γ and IL-2 could be consistently detected in the whole blood of recovered participants. T cells predominantly recognised structural SARS-CoV-2 proteins. In vitro expansion demonstrated that while CD8⁺ T cells recognised nucleocapsid protein, spike protein and ORF3a, CD4⁺ T cells more broadly targeted multiple SARS-CoV-2 proteins.

Conclusion: These observations provide a timely monitoring approach for identifying SARS-CoV-2 cellular immunity and may serve as a diagnostic for the stratification of risk in immunocompromised and other at-risk individuals.