Astrocyte response to St. Louis encephalitis virus.

Area of Science:

• Neurovirology
• Immunology
• Cell Biology

Background:

• St. Louis encephalitis virus (SLEV), a flavivirus, causes neurological illness in humans via mosquito transmission.
• SLEV must cross the blood-brain barrier, involving endothelial cells and astrocytes, to reach the central nervous system (CNS).
• Astrocytes are crucial for CNS homeostasis and were investigated for their response to SLEV infection.

Purpose of the Study:

• To investigate the effects of SLEV infection on astrocytes, focusing on astrogliosis, immune response, and apoptosis.
• To compare the cytotoxicity of SLEV in astrocytes versus Vero cells.
• To understand astrocyte-specific mechanisms involved in SLEV neuroinvasion.

Main Methods:

• Infection of primary astrocyte cultures and Vero cells with SLEV.
• Assessment of cytopathic effects and cytotoxicity.
• Analysis of major histocompatibility complex (MHC)-I expression, glial fibrillary acidic protein (GFAP) for astrogliosis, and caspase-3 activation for apoptosis.
• SLEV immunostaining to determine viral location.

Main Results:

• Both astrocyte and Vero cell cultures showed cytopathic effects, but astrocytes exhibited over 50% reduced mortality compared to Vero cells at a 1E-01 dilution.
• SLEV-infected astrocytes displayed increased MHC-I expression and astrogliosis (elevated GFAP, increased cellular processes).
• Higher SLEV concentrations led to increased caspase-3 activation and nuclear membrane destruction in astrocytes, with virus observed in the perinuclear region.

Conclusions:

• Astrocytes mount an immune response (MHC-I) and undergo reactive changes (astrogliosis) upon SLEV infection.
• While SLEV infection induces apoptosis in astrocytes, it is less cytotoxic than in Vero cells.
• Mechanisms beyond direct astrocyte infection are likely involved in the neuroinvasive progression of St. Louis encephalitis.