Molecular detection and sequence analysis of hepatitis E virus in patients with viral hepatitis from North India

Burden of hepatitis E virus infection in pregnancy and maternofoetal outcomes: a systematic review and meta-analysis

BACKGROUND

There is still a dearth of knowledge on the burden of HEV infection in the global population of pregnant women. Therefore, we conducted a systematic review and meta-analysis to estimate the global burden of HEV infection in pregnancy.

METHODS

We searched PubMed, Embase, Web of Knowledge, and Global Index Medicus to identify articles published until January 26, 2020. We considered cross-sectional, case-control, and cohort studies reporting the immunoglobulins M HEV seroprevalence in asymptomatic and symptomatic (jaundice or elevated transaminases) pregnant women or investigating the association between HEV infection and maternofoetal outcomes. We used a random-effects model to pool studies. This review was registered with PROSPERO, CRD42018093820.

RESULTS

For HEV prevalence estimates, we included 52 studies (11,663 pregnant women). The seroprevalence was 3.5% (95% confidence interval: 1.4-6.4) in asymptomatic women (most of whom from high endemic areas). The prevalence in symptomatic women was 49.6% (42.6-56.7) with data only from HEV high endemic countries. In the multivariable meta-regression model, the prevalence was higher in symptomatic women compared to asymptomatic (adjusted prevalence odds ratio [aPOR]: 1.76; 95%CI: 1.61-1.91) and decreased with increasing year of publication (by 10-year) (aPOR: 0.90; 95%CI: 0.84-0.96). The proportion of HEV vertical transmission was 36.9% (13.3-64.2). Risk of bias was low, moderate and high respectively in 12 (23%), 37 (70%), and 4 studies (7%) addressing HEV prevalence estimation. HEV infection was associated with maternal deaths (pooled OR 7.17; 3.32-15.47), low birth weight (OR: 3.23; 1.71-6.10), small for gestational age (OR: 3.63; 1.25-10.49), preterm < 32 weeks (OR: 4.18; 1.23-14.20), and preterm < 37 weeks (OR: 3.45; 2.32-5.13), stillbirth (OR: 2.61; 1.64-4.14), intrauterine deaths (OR: 3.07; 2.13-4.43), and not with miscarriage (OR: 1.74; 0.77-3.90). All studies which assessed the association between HEV infection and maternofoetal outcomes had a moderate risk of bias.

CONCLUSIONS

Findings from this study are suggestive of a high burden of HEV infection in pregnancy in high endemic countries, its association with poor maternofoetal outcomes, and a high rate of vertical transmission. This study supports the need for specific strategies to prevent exposure of pregnant women to HEV infection, especially in high endemic areas.

Implications of Hepatitis E Virus in Blood Transfusions, Hemodialysis, and Solid Organ Transplants

Hepatitis E Virus (HEV) is emerging as the primary cause of acute viral hepatitis in humans. The virus is commonly transmitted by the fecal-oral route via contaminated water in endemic regions or through the consumption of inadequately cooked swine products or game meats in industrialized regions. HEV genotypes 1 and 2 are predominantly associated with waterborne transmission in developing countries, whereas HEV3 and HEV4 are mainly zoonotically transmitted in industrialized countries. Seroprevalence in populations determined by detecting anti-HEV antibodies and serum HEV RNA is commonly used to analyze the presence of HEV. Although HEV RNA-based detection is now standardized, there is a lack of agreement between the assaying methods used for gathering seroprevalence data. Since 2004, HEV has been considered as a transmissible infectious agent through blood transfusion. Recent seroprevalence studies in European countries indicate an underestimated risk for blood transfusion and hence warrant testing the blood supply. HEV infection is usually self-limiting and spontaneously cleared. However, in about 60% of recipients of solid organ transplants, HEV progresses to chronic hepatitis. Immunosuppressive drugs such as tacrolimus are a major cause of chronic hepatitis and reducing its dosage results in viral clearance in about 30% of patients. In hemodialysis patients, the parenteral route is implicated as an important mechanism of transmission. In this review, we explore the clinical and epidemiological characteristics of various HEV genotypes in blood donors, hemodialysis patients, and transplant recipients.

Hepatitis E in High-Income Countries: What Do We Know? And What Are the Knowledge Gaps?

Hepatitis E virus (HEV) is a positive-strand RNA virus transmitted by the fecal–oral route. HEV genotypes 1 and 2 infect only humans and cause mainly waterborne outbreaks. HEV genotypes 3 and 4 are widely represented in the animal kingdom, and are mainly transmitted as a zoonosis. For the past 20 years, HEV infection has been considered an imported disease in developed countries, but now there is evidence that HEV is an underrecognized pathogen in high-income countries, and that the incidence of confirmed cases has been steadily increasing over the last decade. In this review, we describe current knowledge about the molecular biology of HEV, its clinical features, its main routes of transmission, and possible therapeutic strategies in developed countries.

Acute hepatitis E in India appears to be caused exclusively by genotype 1 hepatitis E virus

BACKGROUND

Hepatitis E is caused by infection with hepatitis E virus (HEV), which has four well-known genotypes. Genotypes 1 and 2 HEV have been reported from human cases in areas where the disease is highly endemic. By contrast, genotypes 3 and 4 HEV, which primarily infect several animal species worldwide, have been reported mainly from sporadic human cases in non-endemic areas such as Japan and high-income countries of Europe and North America. To determine whether genotype 3/4 HEV cause sporadic disease in India, a disease-endemic area, we determined HEV genotype in a group of patients with such disease.

METHODS

A part of the HEV open reading frame (ORF) 1 was amplified and sequenced from sera of 74 patients with sporadic acute viral hepatitis E from four cities in India. The sequences were compared with prototype sequences for various HEV genotypes and subgenotypes and analyzed using phylogenetic tools to determine the genotype of the isolates. For 12 specimens, a part of HEV ORF2 was also similarly analyzed.

RESULTS

Partial ORF1 sequences of all the 74 isolates belonged to genotype 1 HEV, with 88.2% to 100% nucleotide identity with the prototype genotype 1 isolates. Partial ORF2 sequences for all the 12 isolates also belonged to genotype 1 HEV. On phylogenetic analysis, 71 isolates clustered with prototype genotype 1a HEV; the remaining three isolates were located between subgenotypes 1a and 1c but were closer to the former.

CONCLUSION

Human sporadic acute hepatitis E in India is caused almost exclusively by genotype 1 HEV.

Risk factors for vertical transmission of hepatitis E virus infection

Hepatitis E virus (HEV) infection can be vertically transmitted, but the factors that transmit the disease to foetuses are still unclear. We studied a total of 144 pregnant women with HEV infection. Cord blood and newborn samples were taken for analysis. Nutritional factors were evaluated on the basis of anthropometric parameters and biochemical factors, and HEV viral load was quantified by real-time PCR. Sequencing of HEV-positive samples was performed. Approximately 14.63% (6/41) of pregnant patients with acute liver failure (ALF) died before delivery. Vertical transmission was observed in 46.09% (59/128) of HEV-IgM-positive mothers. Approximately 23.80% (10/42) of newborns in the acute viral hepatitis group and 29.41% (5/17) in the ALF group were positive for HEV-RNA. No significant difference was observed in the occurrence of vertical transmission in HEV groups. Viral load was found to be a significant predictor for vertical transmission of HEV infection adjusted with haemoglobin and folate in derivation cohort group. Incorporating these variables, a new score predicting vertical transmission of HEV was derived. Using these significant predictors, the probability for vertical transmission of HEV was well stratified in the validation group (P>.05). In conclusion, viral load was associated with vertical transmission of HEV infection. A valid prediction score model was generated that was verified in a validation cohort group.

Impaired monocyte-macrophage functions and defective Toll-like receptor signaling in hepatitis E virus-infected pregnant women with acute liver failure

Acute viral hepatitis resulting due to hepatitis E viral infection (AVH-E) is often serious in pregnancy and could result in acute liver failure (ALF). The role of monocytes and macrophages (mono-macs) in the pathogenesis of AVH-E and development of ALF-E in pregnancy is unclear. We investigated the functions of mono-macs in pregnant (P), AVH-E (n = 44), ALF-E (n = 12), healthy controls (HC; n = 20) and compared with nonpregnant (NP) AVH-E (n = 10), ALF-E (n = 5), and HC (n = 10). We also recruited non-hepatitis E virus-related pregnant (P), ALF-NE (n = 5) and non-pregnant (NP), ALF-NE (n = 12) patients with ALF. Mono-macs, dendritic cell (DC) phenotypes, and Toll-like receptor (TLR) expressions were studied by flow cytometry and reverse-transcriptase polymerase chain reaction. Mono-macs functionality was determined by analyzing their phagocytic activity and reactive oxygen species (ROS) generation by using flow cytometry. Frequency of mono-macs and DCs was increased during HEV infection compared to HC (P < 0.001). Macrophages were increased (P < 0.002) in ALF-E(P) compared to ALF-NE(P). The macrophage phagocytic activity and Escherichia coli-induced ROS production was significantly impaired in ALF-E(P) compared to AVH-E(P) (P < 0.001), ALF-E(NP), and ALF-NE(P) patients (P < 0.02). TLR3 and TLR9 expression and downstream MYD88 signalling molecules IRF3 and IRF7 were significantly down-regulated in ALF-E(P) (P < 0.00) compared to AVH-E(P) and ALF-NE(P).

CONCLUSION

Functionality of mono-macs is impaired in pregnant ALF-E patients compared to AVH-E(P). Reduced TLR3 and TLR7 expression and TLR downstream-signaling molecules in pregnant ALF-E patients suggests inadequate triggers for the innate immune responses contributing to development and severity of ALF-E. Studies using TLR agonists to activate mono-macs may be of use and in vitro studies should be undertaken using patient samples.

Hepeviridae: an expanding family of vertebrate viruses

The hepatitis E virus (HEV) was first identified in 1990, although hepatitis E-like diseases in humans have been recorded for a long time dating back to the 18th century. The HEV genotypes 1-4 have been subsequently detected in human hepatitis E cases with different geographical distribution and different modes of transmission. Genotypes 3 and 4 have been identified in parallel in pigs, wild boars and other animal species and their zoonotic potential has been confirmed. Until 2010, these genotypes along with avian HEV strains infecting chicken were the only known representatives of the family Hepeviridae. Thereafter, additional HEV-related viruses have been detected in wild boars, distinct HEV-like viruses were identified in rats, rabbit, ferret, mink, fox, bats and moose, and a distantly related agent was described from closely related salmonid fish. This review summarizes the characteristics of the so far known HEV-like viruses, their phylogenetic relationship, host association and proposed involvement in diseases. Based on the reviewed knowledge, a suggestion for a new taxonomic grouping scheme of the viruses within the family Hepeviridae is presented.

Comparison of acute hepatitis E infection outcome in patients with and without chronic hepatitis B infection: a 10 year retrospective study in three regional hospitals in Hong Kong

BACKGROUND

Acute hepatitis E virus (HEV) infection has recently become the commonest cause of acute viral hepatitis in Hong Kong (HK) with majority of HEV belonging to genotype 4. Studies from China have shown that acute hepatitis E patients with underlying chronic hepatitis B virus (HBV) infection may have a worse outcome than those without. In India where genotype 1 is more prevalent, superinfection with hepatitis E on patients with chronic liver disease including chronic hepatitis B infection can cause liver decompensation.

OBJECTIVES

The study aims to determine the clinical outcome of acute hepatitis E infection in patients with and without chronic hepatitis B infection in HK.

STUDY DESIGN

The rates of liver failure, liver-related mortality and all-cause mortality will be compared between acute hepatitis E patients with and without chronic hepatitis B. Analysis was performed using the Statistical Package for the Social Science (SPSS version 12.0). All statistical tests were two-sided, and statistical significance was taken as p<0.05.

RESULTS

Chronic HBV carriers with acute HEV infection were found to have higher liver failure rate, liver-related mortality and all-cause mortality, but the results did not reach statistical significance. Chronic HBV carriers were found to have statistically significantly lower admission ALT level, lower day 28 serum albumin level and higher day 28 serum ALT level.

CONCLUSIONS

A prospective study with sufficient sample size is needed to confirm whether the clinical outcome of patients with chronic HBV infection is worse compared with patients who were not chronic HBV carriers.

Epidemiological and molecular analyses of a non-seasonal outbreak of acute icteric hepatitis E in Bangladesh

Acute hepatitis due to hepatitis E virus (HEV) is endemic in Bangladesh, but its epidemiological characteristics and virological features remain obscure. An outbreak of acute icteric hepatitis E occurred in Rajshahi, Bangladesh during 2010 when 200 patients with visible jaundice visited physicians within a period of 1 month (January-February). Clinical and epidemiological data were collected from these patients using questionnaires. Nucleic acids were isolated from 15 patients who were selected at random to ascertain their HEV genotypes. Near-complete nucleotide sequences of the HEV genome were detected in two patients and partial ORF2 regions in the other 13 patients. All patients tested positive for IgM antibodies to HEV but negative for other hepatitis viruses. Most patients were icteric and complained of vomiting, fever, itching, and abdominal pain. All 15 HEV sequences formed a single cluster within genotype 1a. Two of the 7,186-nt HEV sequences were 99.8% identical. This is the first study to report the clinical, epidemiological, and molecular characterization of an outbreak of acute hepatitis E in Bangladesh.

New route for fast detection of antibodies against zoonotic pathogens in sera of slaughtered pigs by means of flow-through chemiluminescence immunochips

The research on fast screening methods for antibodies against zoonotic pathogens in slaughter animals is important for food safety in farming and meat-processing industries. As a proof-of-concept study, antibodies against the emerging zoonotic pathogen hepatitis E virus (HEV) and enteropathogenic Yersinia spp. were analyzed in parallel using immobilized recombinant antigens (rAgs) of HEV genotypes 1 and 3 and Yersinia outer protein D (YopD) on a flow-through chemiluminescence immunochip. These rAgs are usually part of commercially available line immunoassays (LIAs) used for human diagnostics. In this study, sera from slaughtered pigs were tested on the microarray analysis platform MCR 3 to detect anti-HEV and anti-Yersinia IgG. The new method was characterized regarding signal reproducibility and specificity. The analytical performance was compared with in-house enzyme-linked immunosorbent assay (ELISA) and a LIA based on recomLine HEV (Mikrogen) or the ELISA test kit pigtype Yersinia Ab (Qiagen), respectively. The immunochip revealed the highest analytical sensitivity and was processed in 9 min automatically on the MCR 3. A comparative screening of swine serum samples from Bavarian slaughterhouses regarding anti-HEV and anti-Yersinia IgG seroprevalence was conducted. By using the LIA, 78% of the sera were tested positive for HEV antibodies. The immunochip and the ELISA identified anti-HEV IgG in 96% and 93% of the tested samples using the O2C-gt1 and O2C-gt3 rAg, respectively. The screening for anti-Yersinia IgG resulted in 86% positive findings using the immunochip and 57% and 48% for the ELISA methods, respectively, indicating a higher detection capability of the new method. Serum samples of slaughtered pigs could be analyzed faster and in an automated way on the microarray analysis platform MCR 3 which shows the great potential of the new immunochip assay format for multiplexed serum screening purposes.

Hepatitis E virus: the current scenario

Hepatitis E infection, caused by the hepatitis E virus (HEV), is a common cause of acute hepatitis in developing countries with poor sanitation and hygiene. The virus is classified into four genotypes (1-4) with one serotype. Genotypes 1 and 2 exclusively infect humans, whereas genotypes 3 and 4 also infect other animals, particularly pigs. In endemic areas, large outbreaks of acute hepatitis caused by viruses of genotype 1 or 2 frequently occur due to fecal-oral transmission, usually through contamination of drinking water. With a high attack rate in young adults (aged 15-45 years), the disease is particularly severe among pregnant women (20-30% mortality). HEV appears to be a zoonotic disease, with transmission from pigs, wild boars, and deer, or foodborne. Chronic infections are rare, except in immunosuppressed persons, such as organ transplant recipients. A subunit vaccine has been shown to be effective in preventing the clinical disease, but is not yet commercially available. Our understanding of HEV has undergone major changes in recent years and in this article we review the currently available information with regard to the molecular biology, pathobiology, and epidemiology of HEV infection. We also review the current therapeutic interventions and strategies being used to control HEV infection, with emphasis on possible approaches that could be used to develop an effective vaccine against HEV.