Combined Glycoprotein Mutations in Rabies Virus Promote Astrocyte Tropism and Protective CNS Immunity in Mice

Area of Science:

• Virology
• Neuroscience
• Immunology

Background:

• Rabies virus (RABV) infection of the central nervous system (CNS) leads to fatal encephalitis with limited treatment options.
• Understanding RABV tropism and host immune responses is crucial for developing effective interventions.

Purpose of the Study:

• To investigate the cellular tropism and immune activation of recombinant RABV variants with specific glycoprotein mutations.
• To evaluate the impact of altered tropism on disease progression and host immune response in a mouse model.

Main Methods:

• Recombinant RABV variants with defined glycoprotein substitutions were generated.
• Intracerebral mouse infection model was used to assess cellular tropism via immunohistochemistry and confocal immunofluorescence.
• Immune activation markers including microglial and astrocytic activation, T-cell infiltration, and endothelial activation were evaluated.

Main Results:

• The SPBNGAK variant (R333E/N194K) exhibited mixed neuronal and astrocytic infection, leading to lethal disease.
• GAS variants (R333E/N194S) showed reduced neuronal infection and restricted astrocyte tropism.
• This tropism shift correlated with sustained microglial and astrocytic activation, T-cell infiltration, and endothelial activation.
• Astrocytes infected with GAS variants were nestin-negative and rapidly cleared, unlike SPBNGAK-infected astrocytes.
• Co-inoculation with astrocytotropic TriGAS enhanced survival and reduced neuronal infection by the lethal DOG4 strain.

Conclusions:

• Glycoprotein-mediated astrocyte tropism in RABV infection is associated with distinct immune activation patterns within the CNS.
• Altered tropism may influence the host's immune response and disease outcome following rabies CNS invasion.
• These findings provide insights for designing future studies on astrocyte-restricted RABV infection in therapeutic contexts.