FIG 1.
Mouse survival rate and kinetics of viremia after inoculation with immune complexes (ICs) having different levels of neutralization. ICs were formed in vitro by mixing 2 × 104 PFU/100 μl of S221 with 0 to 100 μg/100 μl of 4G2 Ab. A total of 200 μl of IC was used for inoculation i.v. into mice and infection in BHK-21 cells or THP-1 cells. (A) Mouse survival rate was monitored until day 10 after inoculation with ICs containing 0 μg, 0.01 μg, 0.1 μg, 1 μg, 10 μg, 20 μg, and 100 μg of Ab. (B) A total of 1 × 105 BHK-21 cells were infected with ICs for 1 h followed by replacement with 500 μl of culture medium and incubation for an additional 24 h. A total of 1 × 105 THP-1 cells were infected with ICs for 2 h followed by replacement with 500 μl of culture medium and incubation for an additional 48 h. Virus titer in the supernatants was measured by standard plaque assay using BHK-21 cells. The percentages of virus titer were calculated based on virus control. Error bars indicate standard deviations from duplicate samples. (C) Blood samples were collected on days 1 to 5 (24, 48, 72, 90, and 114 h) postinfection, and mixed serum from each group was subjected to quantitative real-time RT-PCR to measure virus genome numbers. The results were obtained from two separate experiments, the graphs show the average results from two independent measurements, and error bars indicate standard deviations. The numbers of mice per group are 10 for virus control and 5 for other IC inoculations.