A lentiviral expression system demonstrates that L* protein of Theiler's murine encephalomyelitis virus (TMEV) has an anti-apoptotic effect in a macrophage cell line.

DA subgroup strains of TMEV persist in the CNS of infected mice and induce demyelination. The mechanism(s) of virus persistence and demyelination remains unknown. DA subgroup strains synthesize a 17-kDa protein, called L*, from an initiation site out-of-frame with the polyprotein. The previous study using a mutant virus, DAL*-1 (in which the L* AUG is substituted by an ACG) showed that L* has an anti-apoptotic effect in a macrophage cell line, P388D1. Therefore, we established P388D1 cells that continuatively express L*, in order to confirm its role in TMEV-induced apoptosis. The anti-apoptotic activity of L* may be important in TMEV pathogenesis.