Abstract

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Background and Aims: Hepatitis E virus (HEV) is the causative agent of hepatitis E in humans and a leading cause of acute viral hepatitis. It is also responsible for chronic hepatitis in immunosuppressed patients worldwide. The virus is mainly transmitted fecal-orally, through the consumption of contaminated drinking water or infected undercooked meat of pigs. Additionally, HEV can also be transmitted via blood transfusions. Previously, we reported that athymic nude rats support the productive replication of rat HEV when injected intravenously with diluted liver homogenate from HEV-infected rats, causing a chronic infection, which resembles the situation in immunocompromised individuals with chronic HEV (PMID: 27483350). Here, we aim to characterize HEV kinetics from infection to steady state in the rat model.

 

Method: Rat HEV LA-B350 (containing approximately 2 x107 viral RNA copies) was injected in the tail vein of athymic nude rats in both the 12-day and 26-day experiments (n=25). In the 12-day experiment, rats were treated once daily by oral gavage with either vehicle (n=5) or ribavirin at a dose of 30 mg/kg (n=5) or 60 mg/kg (n=5) for 12 days. In the 26-day experiment, rats were left untreated (n=10) for 26 days. Feces were collected at various time points after infection and analyzed for the presence of viral RNA by quantitative PCR.

 

Results: In the 12-day experiment, there is no difference in HEV replication kinetics between the control group and the group treated with ribavirin (30 mg/kg, once daily oral administration) (Fig. 1a and b). Three main viral phases were identified in these rats: a LLOQ phase that lasts ~4 days (4.8 ± 1.7 days) (phase 1: P1), a plateau phase that lasts ~4 days (phase 2: P2), and the beginning of a rapid ascension phase (phase 3: P3). In the rats treated with ribavirin 60 mg/kg, the viral load remained in the LLOQ (P1) phase (Fig. 1c). In the 26-day experiment, similar P1 and P2 phases were seen (Fig. 1d) as in the 12-day experiment (Fig. 1a and b). The 26-day experiment helped to fully characterize phase 3 (P3) that lasted until ~day 18 post infection (with viral doubling time of ~5 days) that was followed by a high viral plateau (7.9±0.5 log10 copies g-1 feces) (phase 4: P4) (Fig. 1d).

 

Conclusion: The rat HEV infection kinetics presented here is an important step in characterizing this experimental model system so that it can be effectively used to elucidate the dynamics of the HEV life cycle and possibly to predict the efficacy of (novel) antiviral therapeutics or vaccine candidates. Future studies need to reveal whether the viral kinetics in the feces reflect that in the liver and/or blood.