A Theiler's virus alternatively initiated protein inhibits the generation of H-2K-restricted virus-specific cytotoxicity

In susceptible mouse strains, the wild-type Daniel's (wt-DA) strain of Thei ler's murine encephalomyelitis virus induces a persistent central nervous s ystem (CNS) infection with chronic demyelination, The virus is cleared from resistant mice with no resulting demyelination. We characterized the role of the DA L* protein in late demyelination and persistent infection. The DA genome has two alternative reading frames, encoding the virus polyprotein and L*, respectively. The mutant virus DAL*-1 fails to synthesize L* and do es not persist in the CNS of wt-DA-susceptible SJL/J or B10.S mice. Since c lass I-restricted cytotoxicity has been shown to determine resistance to vi rus persistence and demyelination in this model, virus-specific cytotoxicit y in the CNS of DA-resistant (B6 or B10) and -susceptible (SJL/J and B10.S) mice during the acute stage of DA and DAL*-1 infection was characterized. Following intracerebral inoculation with DAL*-1, virus-specific D-b- and K- b-restricted CTLs were demonstrated in the CNS of resistant B10 mice, where as only D-b-restricted CTL were found in wt-DA-inoculated mice. CTLs specif ic to wt-DA or DAL*-1 recognized class I-presented peptides from either of the viruses. Of particular interest, K-s-restricted virus-specific cytotoxi city-restricted CTLs were identified in the CNS of susceptible SJL/J (H-2(s )) and B10.S (H-2(s)) mice inoculated with DAL*-1. In contrast, no virus-sp ecific CTLs were identified in the CNS of SJL/J and B10.S mice inoculated w ith wt-DA, We propose that L* inhibits the generation of H-2K-restricted vi rus-specific cytotoxicity in the CNS, permitting a persistent infection in susceptible strains, with subsequent inflammatory demyelination in the CNS similar to that in human multiple sclerosis.