T-Cell Activation: Post-Infection Diagnostic Tool for COVID-19.

Area of Science:

• Immunology
• Virology
• Infectious Diseases

Background:

• COVID-19, caused by SARS-CoV-2, became a global pandemic in 2020.
• Cellular immunity is a crucial functional marker for disease assessment, particularly in asymptomatic infections.
• T-cell responses are vital for understanding adaptive immunity post-infection.

Purpose of the Study:

• To investigate T-cell activation as a potential biomarker for identifying individuals with a history of COVID-19.
• To quantify the cellular immune response to SARS-CoV-2 proteins in convalescent donors.
• To assess the persistence and characteristics of T-cell responses after SARS-CoV-2 infection.

Main Methods:

• Blood samples from 46 convalescent COVID-19 donors and 38 controls were analyzed.
• Quantification of T-cell response to SARS-CoV-2 proteins in vitro using interferon-gamma (IFN-γ) assays.
• Analysis of T-cell subpopulations, including CD4+ helper and CD8+ cytotoxic T cells, and their activation levels.

Main Results:

• Significantly higher numbers of activated T cells were observed in individuals with a history of COVID-19 compared to controls.
• Anti-SARS-CoV-2 T cells were detectable weeks after viral clearance.
• T-cell activation showed a decrease in intensity over five months in 79% of patients, with CD4+ T cells being the primary responders.
• Distinct viral proteins elicited differential activation in CD4+ and CD8+ T cells.

Conclusions:

• T-cell activation levels serve as reliable indicators for identifying individuals who have experienced COVID-19.
• The findings suggest that T-cell response quantification could be developed into a valuable diagnostic tool for past SARS-CoV-2 infections.
• Cellular immunity, particularly T-cell responses, plays a significant role in the long-term immune profile after COVID-19.