Chronic viral infection impairs immune memory to a different pathogen

Area of Science:

• Immunology
• Infectious Diseases
• T cell biology

Background:

• Chronic viral infections impair T cell function, affecting pathogen clearance and immune memory.
• The impact of chronic viral infections on pre-existing immune memory to other pathogens is poorly understood.

Purpose of the Study:

• To investigate how chronic viral infections affect established bacteria-specific memory T cells.
• To determine if bystander immune memory is compromised during chronic lymphocytic choriomeningitis virus (LCMV) infection.

Main Methods:

• Mice were immunized with Listeria monocytogenes expressing OVA (Lm-OVA) to generate OVA-specific memory T (Tm) cells.
• Mice were then infected with LCMV strain Cl-13 to establish chronic infection.
• OVA-specific Tm cell numbers, cytokine production, and recall responses were analyzed after Listeria re-challenge.

Main Results:

• Chronically infected mice showed impaired protection against Listeria re-challenge.
• OVA-specific Tm cells decreased in number and effector function during chronic LCMV infection.
• OVA-specific Tm cells did not upregulate inhibitory receptors, unlike virus-specific exhausted T cells, and failed to mount a robust recall response.

Conclusions:

• Established bacteria-specific memory T cells become functionally impaired during unrelated chronic viral infections.
• This impairment may contribute to reduced immunity against other pathogens in individuals with chronic viral infections.