IL-16 expression in lymphocytes and microglia in HIV-1 encephalitis

Area of Science:

• Neuroimmunology
• Virology
• Cellular Biology

Background:

• Interleukin-16 (IL-16) is a cytokine known to interact with the CD4 molecule.
• IL-16 exhibits chemotactic properties and has demonstrated anti-HIV-1 activity.
• The role of IL-16 in the context of HIV-1 infection within the human brain remains to be fully elucidated.

Purpose of the Study:

• To investigate the expression and cellular localization of IL-16 in human brain tissue affected by HIV-1 encephalitis.
• To determine the cellular sources of IL-16 production in the brain under HIV-1 infection.
• To explore the regulation of microglial IL-16 release by HIV-1.

Main Methods:

• Specific immunocytochemistry was employed to detect IL-16 expression in post-mortem human brain tissue.
• In vitro studies utilized human fetal microglia and astrocytes.
• HIV-1 infection and manipulation of viral Nef expression were used to assess regulation of IL-16 release.

Main Results:

• IL-16 expression was identified in infiltrating lymphocytes and activated microglia within HIV-1 encephalitis brain tissue.
• IL-16 immunoreactivity was notably concentrated in microglial nodules.
• Human fetal microglia, but not astrocytes, were found to produce IL-16, with HIV-1 infection up-regulating its release in a Nef-dependent manner.

Conclusions:

• IL-16 functions as a macrophage-lineage specific modulator of the inflammatory response and HIV-1 expression within the brain.
• The recruitment of IL-16-expressing T cells and microglia/macrophages may represent an innate immune response to HIV-1 in the CNS.
• This innate response potentially counterbalances pro-viral factors in the central nervous system.