The Olfactory Bulb: An Immunosensory Effector Organ during Neurotropic Viral Infections

Area of Science:

• Neuroscience
• Immunology
• Virology

Background:

• The olfactory route was first hypothesized as a virus entry portal to the central nervous system (CNS) in 1935.
• Neurotropic viruses utilize retrograde transport along olfactory sensory neuron axons to access the CNS.
• This pathway is relevant even for viruses introduced subcutaneously, such as arboviruses causing encephalitis.

Purpose of the Study:

• To review evidence supporting the olfactory route as a primary pathway for neurotropic virus CNS entry.
• To emphasize the olfactory bulb's (OB) role in early viral detection and control.
• To explore the OB's function as an immunosensory effector organ.

Main Methods:

• Review of historical and recent scientific literature on viral neuroinvasion via the olfactory pathway.
• Analysis of studies investigating immune responses within the olfactory bulb.
• Examination of experimental data on virus transport along olfactory tracts.

Main Results:

• The olfactory neuroepithelium (ONE) and olfactory bulb (OB) are key sites for initial viral entry into the CNS.
• The OB demonstrates significant antiviral innate and adaptive immune responses.
• Evidence suggests the OB is crucial for clearing viruses and controlling early infection spread.

Conclusions:

• The olfactory route is a well-established pathway for neurotropic virus entry into the CNS.
• The olfactory bulb serves as a critical immunosensory organ, playing a vital role in early host defense against viral pathogens.
• Further research into the OB's immune functions may reveal new therapeutic strategies against viral CNS infections.