MMP9 and viral infectious disease: We also found that HPgV infection is associated with genes linked to PD and Parkinsonism, such as increased MMP9 signaling in the brain and enhanced EIF2AK2 signaling in the peripheral blood, suggesting potential mechanisms by which viral infection may exacerbate neuroinvasion and neuroinflammation through extracellular matrix remodeling and cellular stress responses (40–42).