Stable growth of wild-type hepatitis A virus in cell culture

Human wild-type (wt) hepatitis A virus (HAV), the causative agent of acute hepatitis, barely grows in cell culture and in the process accumulates attenuating and cell culture-adapting mutations. This genetic instability of wt HAV in cell culture is a major roadblock to studying HAV pathogenesis and producing live vaccines that are not overly attenuated for humans. To develop a robust cell culture system capable of supporting the efficient growth of wt HAV, we transfected different cell lines with in vitro RNA transcripts of wt HAV containing the blasticidin resistance gene. Blasticidin-resistant colonies grew only in transfected Huh7 cells and produced infectious virus. HAV was genetically stable in Huh7 cells for at least nine serial passages and did not accumulate attenuating or cell culture-adapting mutations. Treatment with alpha interferon A/D cured the blasticidin-resistant Huh7 cells of the HAV infection. The cured cells, termed Huh7-A-1 cells, did not contain virus or HAV antigens and were sensitive to blasticidin. Huh7-A-1 cells were more permissive than parental cells for wt HAV infection, including a natural isolate from a human stool sample, and produced 10-fold-more infectious particles. This is the first report of a cell line that allows the genetically stable growth of human wt HAV. The viral vectors and cells described here should allow better insight into the pathogenesis of HAV and the development of attenuated vaccines. The cell lines susceptible to wt HAV growth may also be used to detect and isolate infectious virus from patient and environmental samples.