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Mouse Moloney leukemia virus infects microglia but not neurons even though it induces motor neuron disease
J F Zachary1, T V Baszler, R A French
1College of Veterinary Medicine, University of Illinois, Urbana, USA. zacharyj@ux1.cso.uiuc.edu
Abstract:
Motor neuron degeneration caused by ts1 MoMuLV occurs by an indirect mechanism and hypothetically appears associated with a two-cell or three-cell pathogenesis hypothesis. The first step in this hypothesis is associated with a small subset of resident microglial cells that serve as the principal target cells for ts1 MoMuLV infection. The second step is likely linked to trophic events, probably mediated by cytokines, that lead to hypertrophy and activation of a substantial number of additional microglial cells (autocrine effect) and adjacent astrocytes (paracrine effect). The third step in this hypothesis appears related to indirect neuronal degeneration mediated by cytotoxins produced by activated microglial cells and astrocytes. In this last step, motor neurons located within these foci of activated microglial cells and astrocytes are 'innocent bystander cells' and degenerate and die due to paracrine effects. The mechanism of motor neuron degeneration is poorly understood but is likely linked to a sequential cascade of trophic factors and cytokines resulting in a final common pathway for motor neuron death involving production of oxidative radicals, excitatory aminoacid neurotransmitter-like substances, prostaglandins, or nitric oxide.
Insights
The ts1 Moloney murine leukemia virus (MoMuLV) causes motor neuron degeneration indirectly. This process involves microglial cells and astrocytes, leading to neuronal death through a cascade of inflammatory factors.
Area of Science:
- Neuroscience
- Immunology
- Virology
Background:
- Motor neuron degeneration is a key feature of several debilitating neurological diseases.
- The precise mechanisms underlying motor neuron loss in viral infections are not fully understood.
- Murine leukemia viruses are known to cause neurological disorders in animal models.
Purpose of the Study:
- To elucidate the indirect mechanism of motor neuron degeneration induced by ts1 Moloney murine leukemia virus (MoMuLV).
- To investigate the roles of microglial cells and astrocytes in the pathogenesis of ts1 MoMuLV-induced neurodegeneration.
- To propose a hypothetical pathogenesis model involving a sequential cascade of cellular and molecular events.
Main Methods:
- The study proposes a hypothetical pathogenesis model based on existing knowledge and observations.
- It describes the proposed sequential steps involving viral infection of microglial cells, activation of glial cells, and subsequent neuronal damage.
- The model integrates concepts of autocrine and paracrine signaling, cytokine mediation, and bystander effects.
Main Results:
- Ts1 MoMuLV infection primarily targets a subset of resident microglial cells.
- Activated microglial cells and astrocytes release trophic factors and cytotoxins, affecting nearby motor neurons.
- Motor neurons are identified as 'innocent bystanders' undergoing degeneration due to paracrine effects from activated glial cells.
Conclusions:
- Motor neuron degeneration by ts1 MoMuLV is an indirect, multi-step process.
- The pathogenesis involves a complex interplay between the virus, microglial cells, astrocytes, and inflammatory mediators.
- Understanding this cascade, including oxidative radicals and nitric oxide, is crucial for developing therapeutic strategies against viral-induced neurodegeneration.