An Optimized Cell Culture System Needed for Hepatitis E Virus Subtypes

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After expanding, freezing, thawing and re-culturing novel wild-type isolates of hepatitis E, investigators in Europe observed what they categorized as an unlimited production of hepatitis E virus during a period of 2 years, which they believe will allow in vitro testing for the effectiveness of sofosbuvir in combination with ribavirin or silvestrol.

Hepatitis E virus (HEV) subtypes 3c, 3e, and 3f strains are predominant in Europe and therefore an optimized cell culture system is needed for research on the HEV life cycle, inactivation, specific drug, and vaccine development, according to study results published in Viruses.1

HEV is a leading cause of hepatitis throughout the world, and in Europe subtypes 3c, 3e, and 3f are predominant.2  HEV is transmitted via the fecal-oral route in developing countries (genotypes 1 and 2) or via contaminated food and blood products worldwide  (genotypes 3 and 4); immunocompromised individuals are particularly at risk of contracting HEV.3

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However, there is a lack of a reproducible cell culture system susceptible to wild-type HEV, which hinders the ability to create a classic inactive or attenuated vaccine,4 develop and test specific drugs, or identify strategies for efficient HEV inactivation.5 Therefore, researchers isolated 3 wild-type strains derived from clinical specimens representing the predominant spectrum of HEV in Europe.1 They found that novel isolates, 14-16753 (3c), 14-22707 (3e), and 15-22016 (3f like) replicate to high viral loads of 108, 109, and 106.5 HEV RNA copies/mL at 14 days post-inoculation, respectively. In addition, they could be kept as persistently infected cell cultures with constant high viral loads (approximately 109 copies/mL) for more than a year and the new isolates do not carry genome insertions in the hypervariable region. Optimization of HEV cell culture identified amphotericin B, distinct salts, and fetal calf serum as important medium supplements and overconfluent cell layers increased infectivity and virus production.  

“In summary, we isolated three novel HEV strains of the predominant subtypes in Europe stably replicating to high viral loads while optimizing and simplifying the cell culture system,” concluded the investigators.1

1. Schemmerer M, Johne R, Erl M, Jilg W, Wenzel JJ. Isolation of subtype 3c, 3e and 3f-like hepatitis E virus strains stably replicating to high viral loads in an optimized cell culture system. Viruses. 2019;11:483.

2. Adlhoch C, Avellon A, Baylis SA, et al. Hepatitis E virus: Assessment of the epidemiological situation in humans in Europe, 2014/15. J Clin Virol. 2016;82:9-16.

3. Donnelly MC, Scobie L, Crossan CL, Dalton H, Hayes PC, Simpson KJ. Review article: hepatitis E-a concise review of virology, epidemiology, clinical presentation and therapy. Aliment Pharmacol Ther. 2017;46(2):126-141.

4. Zhang J, Zhao Q, Xia N. Prophylactic hepatitis E vaccine. Adv Exp Med Biol. 2016;948:223-246.

5. Cook N, D’Agostino M, Johne R. Potential approaches to assess the infectivity of hepatitis E virus in pork products: A review. Food Environ Virol. 2017;9(3):243-255.