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The zoonotic transmission of hepatitis E virus (HEV) genotypes 3 (HEV-3) and 4 (HEV-4), and rabbit HEV (HEV-3ra) has been documented. Vaccination against HEV infection depends on the capsid (open reading frame 2, ORF2) protein, which is highly immunogenic and elicits effective virus-neutralizing antibodies. Escherichia coli (E. coli) is utilized as an effective system for producing HEV-like particles (VLPs). However, research on the production of ORF2 proteins from these HEV genotypes in E. coli to form VLPs has been modest. In this study, we constructed 21 recombinant plasmids expressing various N-terminally and C-terminally truncated HEV ORF2 proteins for HEV-3, HEV-3ra, and HEV-4 in E. coli. We successfully obtained nine HEV-3, two HEV-3ra, and ten HEV-4 ORF2 proteins, which were primarily localized in inclusion bodies. These proteins were solubilized in 4 M urea, filtered, and subjected to gel filtration. Results revealed that six HEV-3, one HEV-3ra, and two HEV-4 truncated proteins could assemble into VLPs. The purified VLPs displayed molecular weights ranging from 27.1 to 63.4 kDa and demonstrated high purity (74.7–95.3%), as assessed by bioanalyzer, with yields of 13.9–89.6 mg per 100 mL of TB medium. Immunoelectron microscopy confirmed the origin of these VLPs from HEV ORF2. Antigenicity testing indicated that these VLPs possess characteristic HEV antigenicity. Evaluation of immunogenicity in Balb/cAJcl mice revealed robust anti-HEV IgG responses, highlighting the potential of these VLPs as immunogens. These findings suggest that the generated HEV VLPs of different genotypes could serve as valuable tools for HEV research and vaccine development. [ABSTRACT FROM AUTHOR]

Acute hepatitis E was considered rare until reports emerged affirming the existence of hepatitis E virus (HEV) genotypes 3 and 4 infections in Japan in the early 2000s. Extensive studies by Japanese researchers have highlighted the pivotal role of pigs and wild animals, such as wild boars and deer, as reservoirs for HEV, linking them to zoonotic infections in Japan. Currently, when hepatitis occurs subsequent to the consumption of undercooked or grilled pork, wild boar meat, or offal (including pig liver and intestines), HEV infection should be considered. Following the approval of anti‐HEV immunoglobulin A antibody as a diagnostic tool for hepatitis E by Japan's Health Insurance System in 2011, the annual number of diagnosed cases of HEV infection has surged. Notably, the occurrence of post‐transfusion hepatitis E promoted nationwide screening of blood products for HEV using nucleic acid amplification tests since 2020. Furthermore, chronic hepatitis E has been observed in immunosuppressed individuals. Considering the significance of hepatitis E, heightened preventive measures are essential. The Japan Agency for Medical Research and Development Hepatitis A and E viruses (HAV and HEV) Study Group, which includes special virologists and hepatologists, held a virtual meeting on February 17, 2024. Discussions encompassed pathogenesis, transmission routes, diagnosis, complications, severity factors, and ongoing and prospective vaccination or treatments for hepatitis E. Rigorous assessment of referenced studies culminated in the formulation of recommendations, which are detailed within this review. This comprehensive review presents recent advancements in HEV research and Japanese clinical practice guidelines for HEV infection. [ABSTRACT FROM AUTHOR]

Aim: Hepatitis E virus (HEV) causes subclinical or acute self‐limiting hepatitis. We surveyed the current seroprevalence and incidence of HEV infection among the general population in Iwate Prefecture, Japan, where the endemic infection is presumed to be low. Methods: Between 2014 and 2016, we recruited individuals from Iwate Prefecture, Japan, who visited a general medical work‐up program. Serum anti‐HEV antibody and HEV RNA were measured twice, with an interval of 2 years. Anti‐HEV antibody was measured with enzyme‐linked immunosorbent assay and HEV RNA with reverse transcription‐polymerase chain reaction. Results: Study participants comprised 1284 Japanese (650 men and 634 women) with age ranging 20–89 years. A total of 90 participants were found to be positive for anti‐HEV immunoglobulin G on the first visit, with a prevalence of 7.0% (95% confidence interval [CI] 5.6%–8.4%). Seroprevalence was higher in men than in women (10.1% vs. 3.7%, p < 0.001), and in those aged in their 50s–80s than in those aged in their 20s–40s (p = 0.006). Positive seroconversion indicating new HEV infection was found in seven of 1194 seronegative participants (0.59%; 95% CI 0.15%–1.0%), indicating the incidence of HEV infection to be 272 per 100 000 person‐years (95% CI 109–561). Conclusions: Our observations suggest that the incidence of HEV infection is high and that it is a leading cause of hepatitis virus infection in Iwate Prefecture, Japan. [ABSTRACT FROM AUTHOR]

Hepatitis E virus (HEV) genotypes 3 and 4 are zoonotic strains that are primarily transmitted through the consumption of undercooked pork or game meat. They also cause asymptomatic infections, acute hepatitis, acute-on-chronic liver failure, chronic hepatitis, and extrahepatic manifestations. Here, we report a man in his 80s who had chronic hepatitis B, took entecavir for it, and presented with higher levels of alanine aminotransferase (ALT) and jaundice. An abdominal computed tomography scan revealed choledocholithiasis with cholecystolithiasis. Although endoscopic papillary balloon dilatation was performed for the removal of a common bile duct stone, the abnormal liver function tests, including jaundice, were prolonged. After other viral hepatitis and other causes of the liver injury were ruled out, as his serum was positive for immunoglobulin A anti-HEV and HEV genotype 3b RNA, we diagnosed him as having acute hepatitis E. In this case, with chronic hepatitis B and a common bile duct stone, the prolonged abnormal results for the liver function tests seemed to be caused by HEV infection. In conclusion, in cases with high ALT levels after removing choledocholithiasis, other factors, including HEV infection, should be considered to determine the cause of abnormal liver function test results. The further examination of hepatitis D virus infection and high ALT levels may be needed in HBV-infected individuals. [ABSTRACT FROM AUTHOR]