p16INK4a Expression and Immunologic Aging in Chronic HIV Infection

Area of Science:

• Immunology
• Cellular Biology
• Virology

Background:

• Chronic HIV infection leads to immune activation and premature aging (immunosenescence).
• p16 INK4a (p16) is a marker of cellular aging, typically increasing with chronological age.
• Infectious diseases can elevate p16, potentially accelerating immune aging and dysfunction.

Purpose of the Study:

• To investigate immunological aging in HIV patients by examining p16 protein expression in T cell subsets.
• To compare p16 levels in HIV-infected individuals (on and off antiretroviral therapy - ART) with age-matched healthy controls.

Main Methods:

• Flow cytometry was used to quantify p16 protein expression in CD4+ and CD8+ T cell subsets.
• Analysis included chronically HIV-infected patients on ART, off ART, and healthy controls.

Main Results:

• Untreated HIV infection showed increased p16 expression in T cells, independent of chronological age.
• ART normalized p16 levels in CD4+ T cells but not CD8+ T cells, suggesting irreversible CD8+ T cell activation/exhaustion.
• Elevated p16 in effector memory T cells (TEM) of untreated subjects correlated with T cell activation and may impair antiviral responses.

Conclusions:

• Chronic HIV infection is associated with elevated p16, a marker of cellular aging, in T cells.
• ART partially restores normal p16 levels in CD4+ T cells, crucial for immune homeostasis.
• Persistent elevation of p16 in CD8+ T cells indicates potential long-term immune dysfunction despite therapy.