Chronic Toxoplasma gondii Infection Exacerbates Secondary Polymicrobial Sepsis

Area of Science:

• Immunology
• Infectious Diseases
• Pathophysiology

Background:

• Sepsis is a life-threatening organ dysfunction caused by dysregulated host response to infection.
• The impact of chronic infections, particularly those inducing T helper 1 (Th1) responses, on sepsis outcomes remains unclear.

Purpose of the Study:

• To investigate how chronic Toxoplasma gondii infection influences susceptibility and mortality during sepsis.
• To elucidate the underlying immunological mechanisms contributing to altered sepsis course in infected hosts.

Main Methods:

• Utilized a murine model of sepsis induced by cecal ligation and puncture (CLP).
• Assessed bacterial burden, mortality rates, lymphocyte populations (Th1, Th2), cytokine profiles (IFN-γ), and hemodynamic parameters.
• Investigated the role of IFN-γ by employing blockade strategies.
• Correlated findings with human septic patient data.

Main Results:

• Mice with chronic T. gondii infection exhibited increased mortality following CLP despite controlled bacterial load.
• Chronic infection led to suppressed Th2 responses and expanded long-lived IFN-γ-producing CD4+ T cells, exacerbating systemic inflammation.
• Increased Th1 cytokines and nitric oxide production resulted in hypotension and septic shock.
• IFN-γ blockade mitigated hypotension and improved survival.
• Human septic patients with T. gondii seropositivity showed a correlation between sepsis severity and elevated IFN-γ levels.

Conclusions:

• Chronic T. gondii infection significantly increases sepsis severity and mortality through mechanisms involving Th1-driven inflammation and hypotension.
• IFN-γ is a critical mediator of detrimental inflammation in this context.
• Toxoplasma gondii infection status is an important consideration for managing sepsis patients.