WT mice were vaccinated and boosted three weeks later. Two weeks after boosting, mice were challenged with MNV1.CW3 and organs titered for MNV three days later ( Figure 1A ). In these WT mice, maximal MNV replication in the intestinal tract occurs in the distal ileum [9] and viral titers could not be detected in duodenum/ jejunum (data not shown). After oral inoculation with MNV1.CW3, WT mice exhibit detectable viral titers in the distal ileum and the MLN three to five days post-infection [9, 31] . Prior infection with