The role of primary infection of Schwann cells in the aetiology of infective inflammatory neuropathies

- Peripheral nerve inflammation due to infection usually result of indirect effects of pathogen.
- Schwann cells express a wide range of pattern recognition receptors.
- M. leprae demonstrates tropism for SC through interaction with different structural proteins in SC basal laminae.
- In vitro infection of SC with M. leprae has demonstrated a novel pathogen-host cell (SC) interaction with M. leprae initiated nuclear reprogramming and de differentiation of SC in to stem-like cells.
- Two novel strategies are demonstrated by Trypanosomes and M. leprae to infect SC and bypass the effective inflammatory anti pathogen response.

SummaryNumerous different pathogens are responsible for infective peripheral neuropathies and this is generally the result of the indirect effects of pathogen infection, namely anti pathogen antibodies cross reacting with epitopes on peripheral nerve, auto reactive T cells attacking myelin, circulating immune complexes and complement fixation. Primary infection of Schwann cells (SC) associated with peripheral nerve inflammation is rare requiring pathogens to cross the Blood Peripheral Nerve Barrier (BPNB) evade anti-pathogen innate immune pathways and invade the SC. Spirochetes Borrelia bourgdorferi and Trepomema pallidum are highly invasive, express surface lipo proteins, but despite this SC are rarely infected. However, Trypanosoma cruzi (Chaga's disease) and Mycobacterium leprae. Leprosy are two important causes of peripheral nerve infection and both demonstrate primary infection of SC. This is due to two novel strategies; T. cruzi express a trans-silalidase that mimics host neurotrophic factors and infects SC via tyrosine kinase receptors. M. leprae demonstrates multi receptor SC tropism and subsequent infection promotes nuclear reprogramming and dedifferentiation of host SC into progenitor stem like cells (pSLC) that are vulnerable to M. leprae infection. These two novel pathogen evasion strategies, involving stem cells and receptor mimicry, provide potential therapeutic targets relevant to the prevention of peripheral nerve inflammation by inhibiting primary SC infection.