Virus-Specific Stem Cell Memory CD8+ T Cells May Indicate a Long-Term Protection against Evolving SARS-CoV-2

Area of Science:

• Immunology
• Virology
• Infectious Diseases

Background:

• Immune memory is vital for controlling SARS-CoV-2 spread and achieving herd immunity.
• Understanding the longevity and characteristics of T-cell protection against evolving viruses is critical.
• Mild to moderate SARS-CoV-2 infections were studied to assess long-term T-cell responses.

Purpose of the Study:

• To identify reliable methods and biomarkers for assessing long-term T-cell memory in peripheral blood after SARS-CoV-2 infection.
• To evaluate SARS-CoV-2-specific CD4+ and CD8+ T-cell responses over 18 months post-infection.
• To compare different T-cell markers for their efficacy in reflecting durable immunity.

Main Methods:

• A cross-sectional study analyzed 107 samples from 95 donors infected with SARS-CoV-2.
• T-cell responses were measured using ELISpot for IFNγ+ T cells and flow cytometry for AIM+ CD4+ and CD8+ T_SCM cells.
• Cells were stimulated with peptide pools representing original and delta SARS-CoV-2 variants.

Main Results:

• AIM+ virus-specific CD4+ and CD8+ T_SCM cells are superior markers for T-cell memory compared to IFNγ+ T cells, persisting beyond 18 months.
• CD8+ T_SCM cells demonstrated remarkable stability and effector function, providing immediate protection irrespective of the initial infecting strain.
• This finding holds true even with the emergence of new SARS-CoV-2 variants like alpha and delta.

Conclusions:

• AIM+ CD4+ and CD8+ T_SCM cells are more accurate indicators of sustained SARS-CoV-2 T-cell memory than IFNγ+ T cells.
• CD8+ T_SCM cells offer a stable and effective mechanism for long-term immunity against SARS-CoV-2, adapting to viral evolution.
• These findings are crucial for understanding and predicting long-term protection against SARS-CoV-2 and other emerging infectious diseases.