Figure 1.

Humoral immune responses in HCV-1 E1/E2-vaccinated chimpanzees. A, Vaccination with HCV-1 E1/E2 and challenge with HCV-1. B, Revaccination with HCV-1 E1/E2 and challenge with H77. The time of vaccinations is indicated by black arrows. The time of challenge is week 0. Qualitative detection of HCV RNA in reverse transcription–nested polymerase chain reaction is indicated (on top) by black (positive) and white (negative) rectangles. Black bars indicate NtAb detected in the HCVpp H77 assay (1:50 dilution tested). Percentage of neutralization was calculated by comparison with serum from a naive animal. Ch653 was not included for analysis of serial samples because it had low HCVpp NtAb titers at the day of challenge.