Salmonella impairs CD8 T cell response through PD-1: PD-L axis

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Salmonella can persist long-term within host immune cells like B cells and plasma cells.
• The mechanisms by which Salmonella evades CD8 T cell responses during chronic infection are not fully understood.
• Pathogens can utilize the PD-1:PD-L pathway to inhibit CD8 T cell activity and establish chronic infections.

Purpose of the Study:

• To investigate the role of the PD-1:PD-L axis in Salmonella persistence.
• To determine if Salmonella-infected cells modulate PD-1 ligands to evade CD8 T cell surveillance.
• To assess the impact of blocking the PD-1:PD-L interaction on CD8 T cell function during chronic Salmonella infection.

Main Methods:

• Evaluation of PD-1 expression on antigen-specific CD8 T cells in infected hosts.
• Assessment of PD-1 ligand (PD-L1, PD-L2) expression on Salmonella-infected cells (B cells, macrophages).
• Inhibition of the PD-1:PD-L axis and subsequent analysis of CD8 T cell proliferation and cytotoxic activity against infected antigen-presenting cells (APCs).

Main Results:

• Salmonella-infected B cells and macrophages consistently express co-stimulatory (CD40, CD80, CD86) and inhibitory (PD-L1, PD-L2) molecules.
• Antigen-specific CD8 T cells exhibit sustained PD-1 expression during late stages of chronic Salmonella infection.
• Blocking the PD-1:PD-L interaction successfully restores CD8 T cell proliferation and their ability to eliminate infected APCs.

Conclusions:

• The PD-1:PD-L interaction is a key mechanism employed by Salmonella to suppress CD8 T cell cytotoxic responses.
• This immune evasion strategy allows Salmonella to maintain long-term persistence within the host.
• Targeting the PD-1:PD-L axis presents a potential therapeutic strategy to enhance immune control of chronic Salmonella infections.