In vitro characterization and preferential infection by canine distemper virus of glial precursors with Schwann cell characteristics from adult canine brain

Aims: Canine distemper virus (CDV)‐induced demyelinating leukoencephalomyelitis is a naturally occurring model for multiple sclerosis. The aim of this study was to establish primary glial cell cultures from adult canine brain for the analysis of CDV spread and cell tropism. Methods: Cultures were inoculated with the CDV‐R252 and a CDV‐Onderstepoort strain expressing the green fluorescent protein (CDV‐OndeGFP). CDV antigen expression was studied using cell type‐specific antibodies at different days post infection. Glial cells expressing p75^NTR were purified using antibody‐based techniques and characterized with regard to antigen expression and proliferation. Results: Three weeks after seeding, cultures contained spindle‐shaped cells expressing p75^NTR, oligodendrocytic cells, astrocytes, microglia and fibroblasts. Both CDV strains induced a mild to moderate cytopathic effect that consisted of single necrotic and few syncytial giant cells, but displayed in part a differential cell tropism. Whereas CDV‐OndeGFP expression in microglia and astrocytes did not exceed 1% and 50%, respectively, CDV‐R252 infected 100% and 80% of both cell types, respectively. The cells most early infected by both CDV strains expressed p75^NTR and may correlate to cells previously identified as aldynoglia. Treatment of p75^NTR+ cells with Schwann cell mitogens and serum deprivation increased proliferation and A2B5 expression, respectively, indicating common properties compared with Schwann cells and oligodendrocyte precursors. Conclusions: Infection of adult canine astrocytes and microglia revealed CDV strain‐specific cell tropism. Moreover, this is the first identification of a glial cell type with Schwann cell‐like properties in adult canine brain and, more importantly, these cells displayed a high susceptibility to CDV infection.