HEV Cell Culture

Cell culture isolation of Hepatitis E Virus Genotype 3 Strain obtained from human feces

Hepatitis E virus (HEV) is considered one of the leading causes of acute viral hepatitis worldwide, and about 20 million infections and approximately 57 000 deaths occurred every year. However, little is known about the replicative virus cycle due to the absence of a consensus cell culture model. A549 cell line is considered susceptible to HEV genotype 3, however, both viral strain and cell culture conditions could affect the viral isolation in vitro. The objective of this work was to isolate in vitro an HEV-3 strain obtained from human feces. To this, a genotype 3 HEV strain previously identified by genetic characterization was inoculated in A549 monolayers, and incubated for two hours at 37 °C. Five days post-infection, cells were passaged (subcultured) for the first time, and serial passages were done on average every four days during 41 days. HEV replication was evaluated through RT-qPCR in each passage, and reinfection of the cell line with the viral progeny derived from A549 infected monolayers was assessed through immunofluorescence and RT-qPCR. Viral RNA was detected in each passage from infected monolayers, and the highest amount was found after 26 days (2 x 106 copies/μL). In reinfection assay, capsid antigen was detected perinuclearly and forming foci, and 1x104 copies/μL of viral RNA was detected after 96 hours post infection. This shows that HEV recovered from the cell lysate monolayers was infectious. This viral isolate offers a critical tool to study the unknown aspect of HEV infection.

Brain Infection by Hepatitis E Virus Probably via Damage of the Blood-Brain Barrier Due to Alterations of Tight Junction Proteins

Extrahepatic injury, particularly neurologic dysfunctions such as Guillain-Barré syndrome, neurologic amyotrophy, and encephalitis/meningoencephalitis/myositis were associated with HEV infection, which was supported by both clinical and laboratory studies. Thus, it is crucial to figure out how the virus invades into the central nervous system (CNS). In this study, CNS lesions were determined in rabbits and Mongolian gerbils inoculated with genotype 4 HEV. Junctional proteins were detected in HEV infected primary human brain microvascular cells (HBMVCs). Viral encephalitis associated perivascular cuffs of lymphocytes and microglial nodules were observed in HEV infected rabbits. Both positive- and negative-strand of HEV RNA was detected in brain and spinal cord in rabbits intraperitoneally infected with HEV at 28 dpi (days postinoculation), but not in rabbits gavaged with HEV. HEV ORF2 protein was further examined in both brain and spinal cord sections of infected rabbits, with positive signals located mainly in neural cells and perivascular areas. Ultrastructural study showed thickened and reduplicated basement membranes of capillary endothelium in HEV RNA positive brain tissues. In vitro study showed loss of tight junction proteins including Claudin5, Occludin, and ZO-1 (zonula occludens-1) in HBMVCs inoculated with HEV for 48 h. These findings indicated that disruption of the blood-brain barrier (BBB) might be potential mechanisms of HEV invasion into the CNS. It provides new insights to further study HEV associated neurologic disorders and will be helpful for seeking potential therapeutics for HEV infection in the future.

Evaluation of an antigen assay for diagnosing acute and chronic hepatitis E genotype 4 infection

BACKGROUND AND AIM

Results obtained from different hepatitis E virus (HEV) tests are usually inconsistent. The detection of serum HEV antigen (Ag) has been suggested to be more sensitive for the diagnosis of genotypes 1 and 3 HEV.

METHODS

We compared the diagnostic accuracies of serum HEV Ag and HEV RNA by using 202 serum samples from patients suspected acute viral hepatitis.

RESULTS

The HEV Ag assay was 100% specific. The lower detected levels of viremia ranged from 10² to 10³  copies/mL. The sensitivity of the HEV Ag test was 90.5%. One of the 42 cases was negative for anti-HEV IgM, but HEV Ag was still detectable. The detectable period of HEV Ag was in concordance with the detectable period of HEV RNA. Serum HEV Ag was persistently detected in two cases of chronic hepatitis E, confirmed by the persistent presence of HEV RNA despite being negative for anti-HEV IgM. HEV Ag demonstrated good consistency with positive HEV RNA (k = 0.938, P < 0.001). Receiver operating characteristic analysis of HEV Ag suggested a second cut-off value of >0.095 to predict HEV patients with 95.24% sensitivity and 98.75% specificity, and the area under the curve was 0.9887, which was higher than that of three commercial anti-HEV IgM ELISA tests.

CONCLUSIONS

The presence of HEV Ag has good consistency with HEV RNA in both acute and chronic genotype 4 hepatitis E. HEV Ag is a more promising serum marker to identify active genotype 4 HEV infection than anti-HEV IgM and HEV RNA.