Pneumonia Severity and Phase Linked to Virus-Specific T Cell Responses with Distinct Immune Checkpoints during pH1N1...

Area of Science:

• Immunology
• Virology
• Respiratory Medicine

Background:

• The longitudinal dynamics of influenza-specific T cell responses in naturally infected individuals are not fully understood.
• The relationship between T cell responses and disease severity in pH1N1 infection requires further elucidation.

Purpose of the Study:

• To characterize longitudinal influenza-specific CD4+ and CD8+ T cell responses in pH1N1-infected patients.
• To investigate T cell activation, immune checkpoint expression, and cytokine/chemokine profiles in relation to disease severity and lung injury.

Main Methods:

• Analysis of peripheral blood mononuclear cells (PBMCs) from pH1N1-infected patients with varying disease severity.
• Flow cytometry to assess T cell subsets, memory markers, and immune checkpoint expression (PD1, CTLA4, LAG3).
• Measurement of migration-related cytokines and chemokines.

Main Results:

• Both CD4+ and CD8+ T cell responses were higher in severe infections compared to mild ones, with distinct longitudinal patterns.
• Effector CD8+ T cells predominated early (7±3 days), while effector memory CD4+ T cells with high immune checkpoint expression were elevated later (21±3 days) in severe cases.
• T cell magnitude, activation status, and cytokine/chemokine levels strongly correlated with disease severity and lung injury.

Conclusions:

• Distinct longitudinal profiles of influenza-specific CD4+ and CD8+ T cell responses and immune checkpoint expression are associated with pH1N1 infection severity.
• These findings highlight the dynamic immune activation patterns and their correlation with lung injury in pH1N1 patients.