Form follows function: astrocyte morphology and immune dysfunction in SIV neuroAIDS

Area of Science:

• Neuroscience
• Immunology
• Pathology

Background:

• Cortical function is impaired in neuroinflammatory conditions like HIV-associated neurocognitive disorders (HAND).
• Astrocyte dysfunction, including blood-brain barrier issues and neurotransmitter imbalances, is implicated in HAND.
• The mechanisms of astrocyte activation and their specific neuroanatomy in HAND remain under-investigated.

Purpose of the Study:

• To investigate innate immune activation in astrocytes.
• To examine the neuroanatomy of astrocytes in a model of AIDS neuropathogenesis.
• To determine the correlation between astrocyte morphology and SIV infection.

Main Methods:

• Quantified glial fibrillary acidic protein (GFAP)-labeled astrocytes and Toll-like receptor 2 (TLR2) positivity to assess innate immune activation.
• Performed detailed morphometric analyses of gray and white matter astrocytes in SIV-infected rhesus macaques using Neurolucida.
• Compared astrocyte morphology in SIV-infected macaques (with and without encephalitis) to control groups.

Main Results:

• Astrocyte cell body size remained unchanged in SIV-infected macaques.
• SIV infection led to shorter, less ramified astrocyte processes, decreasing overall cell arbor in both gray and white matter.
• Encephalitis in SIV-infected macaques was associated with reduced white matter astrocyte arbor length and decreased gray matter astrocyte complexity.

Conclusions:

• This study provides the first evidence linking innate immune activation of astrocytes to altered cortical astrocyte morphology in SIV/HIV infection.
• Astrocyte remodeling is a significant finding correlated with SIV infection.
• Disrupted neuron-glia signaling due to these morphological changes may drive HAND development.