Seven days later, mice were challenged via intranasal inoculation of 4610 4 PFU of wild type, non-recombinant JHMV. Similar to results observed following rJ.S Q600Y infection (Figure 3) , CTL primed via DC-S598 Q600Y vaccination exhibited higher functional avidity when reacted against the native S598 determinant when compared to those arising after DC-S598 vaccination ( Figure 4A ). In other experiments, we examined the survival of mice vaccinated with each determinant, but we observed no significant differences between groups (data not shown), probably because mortality is largely CD4 T cell-mediated in adult mice with acute encephalitis [33, 34] . In terms of virus titers, vaccination with either the native or enhanced S598 determinants resulted in ,70-80% reduction in virus burden compared to mice that received un-pulsed BMDC ( Figure 4B ). When we examined the One-fourth of the pups in an individual litter were infected with each virus. At the indicated day p.i., brains were aseptically harvested, homogenized in sterile PBS and clarified by centrifugation. Supernatants were collected and infectious virus was titered on Hela-MHVR (Hela cells transfected with CEACAM1, the JHMV receptor [59] ) as previously described [27] . Symbols on graph represent individual mice assayed from multiple independent litters. The limit of detection (LOD) for the assay is 80 PFU/brain. frequency and numbers of virus-specific CTL in the CNS of these same mice, we detected markedly fewer S598-specific CTL in the CNS of mice that received BMDC pulsed with S598 Q600Y peptides ( Figure 4C) . Calculation of the product of virus titers and CTL numbers within individual mice, as an approximate measure of CTL potency, indicated that the S598-specific CTL in S598 Q600Ycoated BMDC vaccinees were ,6-7-fold more efficacious on a per cell basis ( Figure 4D ). Thus, S598-specific CTL induced by the S598 Q600Y determinant show similar enhancement in function compared to S598-primed cells, whether measured in vitro ( Figure 3C ,D) or in vivo ( Figure 4D ).