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

Optimization of immunosuppression strategies for the establishment of chronic hepatitis E virus infection in rabbits

Chronic hepatitis E mostly occurs in organ transplant recipients and can lead to rapid liver fibrosis and cirrhosis. Previous studies found that the development of chronic hepatitis E virus (HEV) infection is linked to the type of immunosuppressant used. Animal models are crucial for the study of pathogenesis of chronic hepatitis E. We previously established a stable chronic HEV infection rabbit model using cyclosporine A (CsA), a calcineurin inhibitor (CNI)-based immunosuppressant. However, the immunosuppression strategy and timing may be optimized, and how different types of immunosuppressants affect the establishment of chronic HEV infection in this model is still unknown. Here, we showed that chronic HEV infection can be established in 100% of rabbits when CsA treatment was started at HEV challenge or even 4 weeks after. Tacrolimus or prednisolone treatment alone also contributed to chronic HEV infection, resulting in 100% and 77.8% chronicity rates, respectively, while mycophenolate mofetil (MMF) only led to a 28.6% chronicity rate. Chronic HEV infection was accompanied with a persistent activation of innate immune response evidenced by transcriptome analysis. The suppressed adaptive immune response evidenced by low expression of genes related to cytotoxicity (like perforin and FasL) and low anti-HEV seroconversion rates may play important roles in causing chronic HEV infection. By analyzing HEV antigen concentrations with different infection outcomes, we also found that HEV antigen levels could indicate chronic HEV infection development. This study optimized the immunosuppression strategies for establishing chronic HEV infection in rabbits and highlighted the potential association between the development of chronic HEV infection and immunosuppressants.IMPORTANCEOrgan transplant recipients are at high risk of chronic hepatitis E and generally receive a CNI-based immunosuppression regimen containing CNI (tacrolimus or CsA), MMF, and/or corticosteroids. Previously, we established stable chronic HEV infection in a rabbit model by using CsA before HEV challenge. In this study, we further optimized the immunosuppression strategies for establishing chronic HEV infection in rabbits. Chronic HEV infection can also be established when CsA treatment was started at the same time or even 4 weeks after HEV challenge, clearly indicating the risk of progression to chronic infection under these circumstances and the necessity of HEV screening for both the recipient and the donor preoperatively. CsA, tacrolimus, or prednisolone instead of MMF significantly contributed to chronic HEV infection. HEV antigen in acute infection phase indicates the development of chronic infection. Our results have important implications for understanding the potential association between chronic HEV infection and immunosuppressants.

Laboratory Diagnosis of HEV Infection

Serological and nucleic acid tests for detecting hepatitis E virus (HEV) have been developed for both epidemiologic and diagnostic purposes. The laboratory diagnosis of HEV infection depends on the detection of HEV antigen or HEV RNA in the blood, stool, and other body fluids, and serum antibodies against HEV (immunoglobulin [Ig]A, IgM, and IgG). Anti-HEV IgM antibodies and low avidity IgG can be detected during the acute phase of the illness and can last approximately 12 months, representing primary infection, whereas anti-HEV IgG antibodies can last more than several years, representing remote exposure. Thus, the diagnosis of acute infection is based on the presence of anti-HEV IgM, low avidity IgG, HEV antigen, and HEV RNA, while epidemiological investigations are mainly based on anti-HEV IgG. Although significant progress has been made in developing and optimizing different formats of HEV assays, improving their sensitivity and specificity, there are many shortcomings and challenges in inter-assay concordance, validation, and standardization. This article reviews the current knowledge on the diagnosis of HEV infection, including the most common available laboratory diagnostic techniques.

Immunocompromised rabbit model of chronic HEV reveals liver fibrosis and distinct efficacy of different vaccination strategies

BACKGROUND AND AIMS

HEV infection can lead to chronicity and rapid progression to liver fibrosis and cirrhosis in immunocompromised organ transplant recipients. Robust animal models are urgently needed to study the pathogenesis and test the efficacy of vaccines and antiviral drugs in immunosuppressed settings.

APPROACH AND RESULTS

Cyclosporin A was used to induce immunosuppression. Rabbits were challenged with genotype 3 or 4 HEV (i.e., the rabbit-derived HEV3 and human-derived HEV3 or HEV4). We assessed HEV markers within 13 weeks post inoculation (wpi) and pathological changes by hematoxylin and eosin and Masson staining at 4, 8, or 13 wpi. Chronic HEV infection was successfully established in immunocompromised rabbits. HEV RNA and/or antigens were detected in the liver, kidney, intestine, urine, and cerebrospinal fluid samples. Chronically infected animals exhibited typical characteristics of liver fibrosis development. Intrahepatic transcriptomic analysis indicated activation of both innate and adaptive immunity. Establishment of HEV chronicity likely contributed to the inhibited T-cell immune response. Ribavirin is effective in clearing HEV infection in immunocompromised rabbits. Most interestingly, vaccination completed before immunosuppression conferred full protection against both HEV3 and HEV4 infections, but vaccination during immunosuppression was only partially protective, and the efficacy did not improve with increased or additional vaccine doses.

CONCLUSIONS

The immunocompromised rabbit model of both chronic HEV3 and HEV4 infection that was established captured the key features of chronic HEV infection in transplant patients, including liver fibrogenesis, and revealed the distinct effectiveness of vaccination administered before or under immunosuppression. This rabbit model is valuable for understanding the pathogenesis of chronic hepatitis E, as well as for evaluating antiviral agents and vaccines.

Hepatitis E: An update on One Health and clinical medicine

The hepatitis E virus (HEV) is one of the main causes of acute hepatitis and the de facto global burden is underestimated. HEV-related clinical complications are often undetected and are not considered in the differential diagnosis. Convincing findings from studies suggest that HEV is clinically relevant not only in developing countries but also in industrialized countries. Eight HEV genotypes (HEV-1 to HEV-8) with different human and animal hosts and other HEV-related viruses are in circulation. Transmission routes vary by genotype and location, with large waterborne outbreaks in developing countries and zoonotic food-borne infections in developed countries. An acute infection can be aggravated in pregnant women, organ transplant recipients, patients with pre-existing liver disease and immunosuppressed patients. HEV during pregnancy affects the fetus and newborn with an increased risk of vertical transmission, preterm and stillbirth, neonatal jaundice and miscarriage. Hepatitis E is associated with extrahepatic manifestations that include neurological disorders such as neuralgic amyotrophy, Guillain-Barré syndrome and encephalitis, renal injury and haematological disorders. The risk of transfusion-transmitted HEV is increasingly recognized in Western countries where the risk may be because of a zoonosis. RNA testing of blood components is essential to determine the risk of transfusion-transmitted HEV. There are currently no approved drugs or vaccines for HEV infections. This review focuses on updating the latest developments in zoonoses, screening and diagnostics, drugs in use and under development, and vaccines.

Dynamics of Hepatitis E Virus (HEV) Antibodies and Development of a Multifactorial Model To Improve the Diagnosis of HEV Infection in Resource-Limited Settings

Serological markers are important for the diagnosis of hepatitis E virus (HEV) infection. This study aims to compare the diagnostic performance of the anti-HEV IgM and the HEV antigen (Ag) assays and establish a multifactorial model to improve the diagnosis of current HEV infection when HEV RNA detection is not available. A total of 809 serum samples, including 325 anti-HEV IgM-positive and 484 anti-HEV IgM-negative samples, were tested for HEV RNA. The anti-HEV IgM assay had very high sensitivity (99.4%) but moderate accuracy (79.2%) and specificity (74.3%). By retrospective follow-up of 58 patients with sequential samples (n = 143) tested for anti-HEV antibodies, we found anti-HEV IgM remained positive for more than 10 months in some HEV-infected patients, when HEV RNA was already undetectable; thus, decision solely based on anti-HEV IgM may lead to misdiagnosis. In contrast, the HEV Ag assay had very high specificity (100%). However, the detection efficiency of HEV Ag greatly diminished when the HEV RNA level was low or the anti-HEV IgG level was high. By logistic regression, a model integrating anti-HEV IgM, alanine aminotransferase, and HEV Ag was proposed, and the cutoff value was determined based on the testing results of the 143 sequential samples. The model was further evaluated with 67 randomly selected IgM-positive samples from single-visit patients. Overall, the model outperformed the anti-HEV IgM or the HEV Ag assay in the diagnosis of current HEV infection (sensitivity/specificity/accuracy, 89.5%/95.2%/91.9%). The area under the receiver operating characteristics curve of the model was greater than 0.97.

Performance Evaluation of Different Commercial Serological Kits for Diagnosis of Acute Hepatitis E Viral Infection

Clinical diagnosis of hepatitis E viral (HEV) infection mainly relies on serological assays, and the current status of misdiagnoses regarding HEV infection is uncertain. In this study, patients with acute HEV infection were tested for anti-HEV IgM and IgG, a HEV antigen (Ag), and viral loads (HEV RNA). Serology was performed using four commercial HEV ELISA kits: Wantai, Kehua, Lizhu, and Genelabs IgM and IgG. The HEV RNA was detected using RT-PCR assays. The sensitivities of different kits for anti-HEV IgM ranged from 82.6% to 86%. Each kit for anti-HEV IgM was highly specific (97.8–100%). The sensitivities of all kits to detect anti-HEV IgG with (87.2–91.9%) had a substantial agreement, but the Kehua and Genelabs tests were more specific than the Wantai and Lizhu tests. The Wantai tests for the HEV Ag and HEV RNA were also important for acute HEV infections (Kappa = 0.787). Furthermore, a total of 6.98% of HEV infections were positive for HEV RNA but negative for both the HEV Ag and anti-HEV antibodies of IgM and IgG classes. Our findings demonstrate that the diagnosis of hepatitis E may be missed if only serological assays are used. Thus, a combination of serological and nucleic acid testing provides the optimal sensitivity and specificity to the diagnostic process.

Advanced Immunotechnological Methods for Detection and Diagnosis of Viral Infections: Current Applications and Future Challenges

Diagnosis and identification of viruses is an important component of diagnostic virology laboratory. Although various modes of diagnostic methods are now available at disposal, a vast majority of the diseases across the globe remain undiagnosed. This is largely due to the overlapping undifferentiated set of symptoms across myriad set of RNA and DNA viral diseases. As such, it becomes critical to take into consideration several factors for viral diagnosis ranging from the type and quality of specimen collected, time of specimen collection, mode of transport, accuracy, specificity, sensitivity, and the type of diagnostic method used. This chapter broadly emphasizes various methods on diagnostic virology ranging from the classical methods of diagnosis to the most recently developed molecular methods of detection of virus.

Hepatitis E virus infection in acute non-traumatic neuropathy: A large prospective case-control study in China

Neurological manifestations are potentially associated with hepatitis E virus (HEV) infection in Europe, mainly attributed to genotype (GT) 3 HEV infection. In this study, we determined the frequency and causal relationship of HEV in patients with non-traumatic neurological disorders in China, where GT4 HEV is prevalent. 1117 consecutive patients diagnosed with neurological illnesses in a hospital of eastern China and 1475 healthy controls who took routine examination in the same hospital were tested for HEV by serology and molecular methods. Anti-HEV IgM antibodies were detectable in 6 (0.54%) of the patients and 10 (0.68%) of the healthy controls (P = 0.651). Serum HEV RNA was detected in all of the 16 individuals with positive anti-HEV IgM. The six patients with HEV infection included two viral encephalitis, two posterior circulation ischemia, one peripheral neuropathy and one Guillian-Barré syndrome. They had no symptoms of acute viral hepatitis except two patients of viral encephalitis that showed mildly transaminitis. Additional, 39.51% patients and 35.63% controls without acute HEV infection were positive for anti-HEV IgG (P = 0.144). Anti-HEV IgG positivity was more frequent in male and elderly in both the patients and control groups, but unrelated to the incidence of any non-traumatic neurological illness, hospital stay or treatment outcome, except linking to better outcome of hemorrhagic stroke disease. These data demonstrated that HEV appears not to contribute to acute neurological disorders in China. Nevertheless, we cannot exclude a possible causative role, suggesting that testing HEV in this population, especially in situations of unexplained deregulated liver function would be warranted.

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HEV infection is identified in 0.54% patients with acute neurological injury in this study, where GT4 HEV is prevalent.

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The incidence of HEV infection is not significantly different between neurological patients and healthy controls.

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A potential causal relationship between GT4 HEV infection and viral encephalitis has been indicated.

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Patients with viral encephalitis are prone to have deranged liver function following HEV infection.

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The prevalence of GT4 HEV is higher in male and elderly in both neurological patients and healthy controls.

Neurological injury is the most common extra-hepatic manifestation in patients with hepatitis E virus (HEV) infection. HEV associated neurological syndromes have been widely reported in Europe, mainly attributed to genotype 3 HEV infection. We determined the frequency and causal relationship of HEV in patients with non-traumatic neurological disorders in China, where genotype 4 HEV is prevalent.

We have demonstrated that 0.54% patients with acute non-traumatic neurological injury have evidence of HEV infection. The overall incidence of HEV infection is not significantly different between patients and healthy controls. Nevertheless, we cannot exclude a possible causative role, suggesting that testing HEV in this population, especially in situations of unexplained deregulated liver function would be warranted.