Mutational events during the primary propagation and consecutive passages of hepatitis E virus strain JE03-1760F in cell culture

We recently developed a cell culture system for hepatitis E virus (HEV) in PLC/PRF/5 cells, using a genotype 3 HEV (JE03-1760F strain). Thirteen generations of consecutive passages of culture supernatant were successfully carried out in PLC/PRF/5 cells, with the highest HEV load reaching 108 copies/ml in the culture medium. Based on continuous release of progenies into culture medium, 50% tissue culture infectivity doses were estimated to be 2.0 × 103 copies for wild-type JE03-1760F and 1.4 × 102 copies for p13 (progeny in the thirteenth passage). Earlier appearance and greater increase in the yield of progenies in the culture supernatant were evident in p13 compared with wild-type. The cell culture-produced variants in primary propagation (p0) and consecutive passages (p5 [fifth passage], p10 [tenth], and p13) differed from the wild-type virus by 1, 9, 18, and 19 nucleotides (nt), respectively, over the entire genome of 7226 nt, excluding the poly(A) tail. Three of five non-synonymous mutations in p13 were shared by a variant (fifth passage) in another series of passages of JE03-1760F. These results suggest that adaptation of HEV variants to growth in vitro is associated with a limited number of mutations similar to hepatitis A virus.