Figure 1

Theiler's murine encephalomyelitis virus infection can be established in resistant C57BL/6 mice following lipopolysaccharide intraperitoneal injections. Photomicrographs of X-ray films from in situ hybridization (ISH) signals for viral protein 1 (VP1) RNA expression in the brain and spinal cord of SJL/J and C57BL/6 mice one month following Theiler's murine encephalomyelitis virus (TMEV) infection (intracerebral, 2 × 10⁵ p.f.u.). In order to render the C57BL/6 susceptible to TMEV, LPS injections (20 μg, i.p., Sigma Aldrich) were given immediately following the TMEV injection and +5 days post-infection. A majority of the C57BL/6 mice receiving the (lipopolysaccharide) LPS (6/10) developed a TMEV infection (as shown by the expression of VP1, above) while one mouse (1/10) not receiving the LPS developed a lasting infection (not shown). Inset (top): dark field photomicrography of proteolipid protein (PLP) mRNA expression following ISH. Hybridized slides were dipped into NTB emulsion milk (Kodak). All SJL/J and C57BL/6 mice that developed an infection showed demyelination, as exemplified by the absence of PLP expression in white mater areas of the spinal cord (dashed line area). Bottom panel shows quantitative analysis of VP1 optical density (O.D.) in representative spinal cord sections. Although comparisons revealed that VP1 expression was significantly lower in infected C57BL/6 versus SJL/J mice, VP1 expression in C57BL/6 was still significantly higher in the TMEV infected versus vehicle saline group. Data presented as mean ± SEM. †: significant SJL/J vs C57/BL6 pair wise comparison within TMEV treatment, Bonferonni corrected t-test p < 0.05; *: significant TMEV vs Vehicle within strain pair wise comparison Bonferonni corrected t-test p < 0.05.