MAIT cells are activated during human viral infections

Area of Science:

• Immunology
• Virology
• Infectious Diseases

Background:

• Mucosal-associated invariant T (MAIT) cells are abundant immune cells primarily known for recognizing bacterial ligands.
• Their role in viral infections has been less understood.

Purpose of the Study:

• To investigate MAIT cell activation during human viral infections.
• To elucidate the mechanisms and potential implications of MAIT cell responses in viral pathogenesis.

Main Methods:

• Analysis of MAIT cell activation markers (cytokine release, Granzyme B upregulation) in patients with dengue virus, hepatitis C virus (HCV), and influenza virus infections.
• Investigating the role of cytokines (IL-18, IL-12, IL-15, IFN-α/β) and T-cell receptor (TCR) independence in MAIT cell activation.
• Assessing the correlation between MAIT cell activation, disease severity, and therapeutic responses.
• Evaluating the impact of TCR-independent MAIT cell activation on viral replication in vitro.

Main Results:

• MAIT cells are activated in vivo during dengue, HCV, and influenza infections.
• Activation is TCR-independent, requiring IL-18 in synergy with other cytokines (IL-12, IL-15, IFN-α/β).
• MAIT cell activation and IL-18 levels correlate with dengue disease severity.
• HCV treatment with interferon-α induces MAIT cell activation and enhances therapeutic response.
• TCR-independent MAIT cell activation reduces HCV replication in vitro via IFN-γ.

Conclusions:

• MAIT cells are activated by viral infections through a TCR-independent pathway.
• Cytokine signaling, particularly IL-18, is crucial for MAIT cell activation during viral infections.
• MAIT cells may play a significant role in host defense against viruses and contribute to immunopathology.