CD8A and infection: By gradually increasing the interval between peripheral immunization and subsequent i.c. challenge, we could demonstrate that protective immunity was induced between 4 and 7 days after virus inoculation, coinciding with the appearance of both neutralizing Abs and virus-specific CD8 T cells, and in both mouse strain tested clinical protection was very stable over time; thus, even 8 months after priming, mice challenged i.c. effectively controlled the infection and did not develop evidence of disease.