Perforin and granzymes have distinct roles in defensive immunity and immunopathology

Area of Science:

• Immunology
• Virology
• Molecular Biology

Background:

• Controlling viral infections requires balancing pathogen elimination with preventing host immunopathology.
• Perforin (Prf1) and granzymes (Gzms) are key cytotoxic molecules involved in immune responses.
• Their specific roles in viral clearance versus immune-mediated damage are not fully understood.

Purpose of the Study:

• To elucidate the distinct roles of perforin (Prf1) and granzymes (Gzms) in host defense and immunopathology during viral infection.
• To investigate the mechanisms underlying fatal outcomes in Prf1-deficient mice infected with murine cytomegalovirus (MCMV).
• To explore the therapeutic potential of targeting specific immune mediators in viral-induced syndromes.

Main Methods:

• Utilized a murine cytomegalovirus (MCMV) infection model in wild-type, Prf1-deficient, and Gzma/Gzmb-deficient mice.
• Quantified viral titers and assessed host survival and pathological phenotypes.
• Conducted blocking experiments targeting key inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha).

Main Results:

• Both Prf1 and Gzms are critical for controlling MCMV infection, as evidenced by increased viral titers in deficient mice.
• Gzma/Gzmb-deficient mice survived MCMV infection, whereas Prf1-deficient mice developed a fatal hemophagocytic lymphohistiocytosis (HLH)-like syndrome.
• Lethality in Prf1-deficient mice was attributed to the accumulation of mononuclear and T cells and was primarily mediated by TNF-alpha.

Conclusions:

• Perforin (Prf1) and granzymes (Gzms) play distinct and crucial roles in managing viral infections and preventing immunopathology.
• Prf1 is essential for preventing fatal immunopathology, while Gzms are important for viral clearance and host recovery.
• Targeting TNF-alpha may offer a therapeutic strategy for viral-triggered HLH and related inflammatory syndromes.