The generation of high titer cell culture-adapted JFH1 virus by serial passages.

<p>To produce high titer cell culture adapted infectious JFH1 HCV, <i>in vitro</i> transcribed, JFH1-wt RNA was electroporated into Huh-7.5 cells. Transfected Huh-7.5 cells were maintained and passaged every three days. Five passages were defined as one cycle. Culture supernatant at the end of each cycle was used to infect fresh Huh-7.5 cells. A total of 8 cycles (40 passages or 120 days) were done. During the adaptation process, the titer of infectious HCV was determined by immunofluorescence assays. The viral titer is expressed as focus-forming units per milliliter (f.f.u./ml) measured in triplicate. The data are presented as mean ± standard deviations (n = 6).