HAV titration by ARTA. (A) Huh7-A-I cells in 96-well plates were infected with ten-fold serial dilutions of HAV-Bsd and selected with 2 μg/ml blasticidin. Four wells were infected with each virus dilution. Plates were incubated for 8 days at 35°C and analyzed by the naked eye and under the microscope. A color photograph of the plate was taken a few minutes after removing the plate from the CO2 incubator. The color of the cell culture medium of all wells at dilution -2 to -4 and a single well at dilution -5 was orange-to-yellow, and these wells contained live cells as confirmed by microscope examination (not shown). The cell culture media color of three wells at dilution -5 and all the wells at dilutions -6 to -8 was pink to purple, and these wells contained dead cells as assessed under the microscope. The yellow and orange wells were considered positive for HAV-Bsd. (B) Four control wells containing Huh7-A-I cells were mock-infected and treated with 2 μg/ml blasticidin (+) or cell culture medium (-). The cells treated with blasticidin died and the cell culture media color turned pink-to-purple. The cells that did not receive the antibiotic were healthy and the color of the cell culture media was orange-to-yellow.