Determination of the HAV neutralization potency of human IG preparations by ARTA. HAV-Bsd was treated with 1% of Lab 1, Lab 2, WHO standard IG preparations, or negative plasma control, or mock-treated and titrated on 96-well plates containing Huh7-A-I cells. Four-fold serial dilutions of the neutralization reactions were inoculated in 6 wells per dilution. Complete medium with 2 μg/mL blasticidin was added to the wells, and the plates were incubated at 35°C for 8 days. (A) Color photograph of the 96-well plates obtained few minutes after taking the plates form the CO2 incubator. The mock-treated control plate is not shown, and one well of the WHO Standard is shown empty due to microbial contamination. (B) HAV-Bsd titers were determined by the Reed and Muench method counting positive (yellow and orange) and negative (pink and purple) wells. The ID50 program was used to calculate the viral titers as the log10 of tissue culture infectious dose 50% (TCID50) and standard deviations, which are shown as bars.