Mice deficient in the inflammasome adaptor ASC (ASC−/−) are partially protected from acute weight loss after intramuscular immunization with rVSV.
Groups of adult female C57BL/6 wild type or ASC−/− mice were immunized with two injections (5×108 PFU per injection) of rVSV in each rear quadriceps, or were sham inoculated with sterile PBS. At 12 and 24 hours after infection mice (n = at least 4 per timepoint), were sacrificed and IL-1β in the blood (Panel A left), draining popliteal LN (Panel A middle), and quadriceps muscle (Panel A right) was quantitated via ELISA. The amount of IL-1β produced by wild type and ASC−/− mice was not significantly different at any time or in any organ. The comparison of IL-1β production by wild type and ASC−/− mice has been performed twice with consistent results. Panel B shows average percent initial weight for wild type (n = 6) and ASC−/− (n = 5) mice after intramuscular challenge with 5×108 PFU of rVSV. The comparison of WT and ASC−/− mice has been performed four times with consistent results. Panel C shows average percent initial weight for wild type (n = 5), ASC−/− (n = 5), and IL-1R−/− (n = 4) mice infected with rVSV. IL-1R−/− mice lost significantly less weight than wild type (days 2–4) or ASC−/− mice (days 1–2) (P<0.05 via one way ANOVA with Bonferroni test). The comparison of WT, IL-1R−/−, and ASC−/− mice has been performed twice with consistent results. Panel D shows average serum neutralizing titers for WT (n = ) and ASC−/− (n = ) mice after primary immunization with VSV. There were no significant differences in neutralizing titer between the two groups. Panel E shows average percent CD8 T cells specific for the VSV N1 epitope as measured by MHC Class I tetramer. At 14 days after immunization, WT mice (n = 9) had significantly more (P = 0.001, Two-tailed T test) VSV N specific CD8 T cells than ASC−/− mice (n = 9), but by day 28 the difference was no longer significant (P = 0.07). At eight weeks after the primary infection pre-immune WT (n = 10) and ASC−/− (n = 6) mice were challenged intranasally with a semi-lethal dose of rVSV (1×108 PFU). A cohort of naïve wild type mice (n = 5) was challenged at the same time. All pre-immune mice had robust immunity to rechallenge (Panel F) and did not lose weight or exhibit other signs of pathology. One of the naïve mice succumbed to infection.