Figure 3.

West Nile virus (WNV) challenge of squirrel monkeys immunized with MVSchw-sE_WNV. Twelve monkeys immunized with MVSchw-sE_WNV and four monkeys mock immunized (with empty MV vaccine) or phosphate-buffered saline (PBS)) were challenged with WNV IS-98-ST1, either 15 or 30 days after immunization. (A) and (B): WNV-specific antibody levels were determined by enzyme-linked immunosorbent assay on the day of immunization, 15 days after immunization, the day of challenge, seven days after challenge and on the day of euthanasia. (C) The presence of WNV genomic RNA was determined by quantitative real-time polymerase chain reaction on day 2 after challenge in the serum of challenged animals. Animals 3, 4, 5 and 6 received one vaccination on day 30 before challenge; animals 9, 10, 11 and 12 received one vaccination on day 15 before challenge; and animals 1 and 2 (PBS) and 7 and 8 (MV) were mock infected. (D) The mean WNV titer in the serum of vaccinated animals, determined by the plaque formation assay at day 2 after challenge. Abbreviations: OD, optical density; pfu, plaque-forming units.