Research ArticleViral clade is associated with severity of symptomatic genotype 3 hepatitis E virus infections in Belgium, 2010–2018
Graphical abstract
Introduction
HEV is the leading cause of acute viral hepatitis worldwide and is more common in high-income countries than initially thought.1 Eight genotypes (gt) have been identified so far, of which gt3 is dominant in Europe and America.2 HEV gt3 infections present as a zoonosis after the consumption of undercooked pig, wild boar, or deer meat, the main viral reservoirs.1 Based on phylogenetic analyses, HEV gt3 subtypes can be assigned to 1 of 3 clades: abchijklm (HEV-3.1), efg (HEV-3.2), and ra (HEV-3.3).2,3
The clinical spectrum of HEV gt3 infections is highly variable: clinically silent in the vast majority, symptoms of acute hepatitis in <5% and acute liver failure in very rare cases.4 The most frequent clinical picture in symptomatic cases is an acute self-limiting hepatitis.1 Individuals with pre-existing cirrhosis can develop an acute-on-chronic liver failure, whereas up to two-thirds of immunocompromised individuals may fail to clear HEV, resulting in a chronic HEV infection.4,5 Similar to other hepatitis viruses, extrahepatic manifestations have been reported, with a predominant neurological disease spectrum.1,4
Both host and viral factors may contribute to this wide spectrum of clinical disease presentations. Host factors identified until now include male sex, age above 50 years, pre-existing liver disease and an immunocompromised status.4,[6], [7], [8] Diabetes mellitus and alcohol consumption are other identified risk factors, most probably linked to an associated chronic liver disease.4,[6], [7], [8] It is currently unclear whether HEV gt3 virological factors, such as viral load or clades, can influence the course of the liver disease. A retrospective phylogenetic analysis of HEV gt3 infections in English blood donors found an association between virus variants and self-reported illness, whereas a larger European study could not corroborate this association in individuals with clinical hepatitis.9,10 In contrast, we recently reported that Belgian adults infected with HEV gt3c are at lower risk of hospitalisation than individuals infected with gt3f in a retrospective survey of the hospitalisation status that has to be provided on Belgian National Reference Centre (NRC) HEV diagnostic test request forms.11 A French study recently confirmed this observation in an analysis of patient-reported symptoms and medical history from individuals infected with HEV gt3f and gt3c.12 However, these studies do not account for possible confounding factors, as some clinical and laboratory data were lacking, or not retrieved through medical chart review.
Here we aim to examine the role of viral and host factors on disease presentation by analysing clinical, biochemical, virological, and histological parameters of Belgian adults infected with HEV with disease signs over an 8-year timeframe. For the present study, we retrieved data from medical charts and re-analysed liver histology of available samples. Based on the most recent recommendations, viraemic cases were phylogenetically clustered in 1 of 3 clades instead of HEV subtypes.2 In addition, we studied serum C-X-C motif chemokine ligand 10 (CXCL10) levels in an expanded cohort with acute HEV gt3 that was well balanced for age, sex, and viral clade. Our data show that HEV gt3 clade efg infections are associated with a more severe disease presentation, irrespective of all previously identified host factors, and lead to higher serum CXCL10 levels and liver necro-inflammatory activity.
Section snippets
Study design and participants
This is a follow-up study of an identified and expanded cohort of individuals with confirmed HEV infection (i.e. a positive serum HEV-RNA and/or a combination of positive HEV-IgM and -IgG serology, as defined by EASL Clinical Practice Guidelines [CPG]4) that were spontaneously reported to the Belgian NRC for viral hepatitis, Sciensano, between January 2010 and June 2018. Based on parameters reported by previous studies,[5], [6], [7], [8],[10], [11], [12] the following variables were
Demographic and clinical characteristics of the patient cohort
The flowchart of cases of HEV included in the study is presented in Fig. 1. Between January 2010 and June 2018, HEV infection was confirmed in 365 individuals by a positive serum HEV-RNA and/or both positive HEV-IgM and -IgG serology. No clinical data could be obtained from 91 cases because of the lack of response to the sent-out CRF (Table S1), leaving 274 cases (75.1%) with clinical data and 253 cases (69.3%) with laboratory values for further analyses (Table 1). Of these, 218 cases (79.6%)
Discussion
HEV gt3 infections are the leading cause of acute viral hepatitis in high-income countries and are increasingly being diagnosed in Europe and Belgium.1,2,15,24 The pathophysiology of the remarkably diverse disease presentation remains poorly understood. In our retrospective study of HEV infections, we demonstrate that viral clade is strongly associated with HEV gt3 disease severity, irrespective of known host risk factors. Indeed, clade efg infections were associated with higher hospitalisation
Abbreviations
ALP, alkaline phosphatase; ALT, alanine aminotransferase; CPG, clinical practice guidelines; CRF, case report form; Ct, cycle threshold; CXCL10, C-X-C motif chemokine ligand 10; gt, genotype; HEV, hepatitis E virus; ICU, intensive care unit; INR, international normalised ratio; NRC, national reference centre; ORF, Open Reading Frame; PCR, polymerase chain reaction; RBV, ribavirin; SOT, solid-organ transplant; ULN, upper limit of normal.
Financial support
This study is a retrospective analysis of routinely collected data, within the Belgian National Reference Centre (NRC) programme funded by the National Institute for Health and Disability Insurance (RIZIV-INAMI, Belgium). TV is supported by a senior clinical investigator grant of the Research Foundation Flanders (FWO) (number 18B2821N, Belgium). JS and NH acknowledge funding from the European Research Council (ERC) Horizon 2020 research and innovation program (grant agreement 682540 — TransMID,
Conflicts of interest
The authors declare no conflicts of interest that pertain to this work.
Please refer to the accompanying ICMJE disclosure forms for further details.
Authors’ contributions
Conceptualisation: MP, TDS, SVG, TV. Data curation: MP, TDS Formal analysis: MP, JS, TR, SK, NH, TV. Funding acquisition: SVG, TV Investigation: MP, JS, TDS, TR, TL, SK, JD, PS, SDM, PW, IC, MVH, JVA, CVS, CM, FJ, MR, MS, WV, LL, CDG, AG, JM, MG, SVO, AM, HR, JD, EB, JS, JPM, SDG, MS, DD, SND, JB, JN, JB, NH, FN, SVG, TV. Methodology: MP, JS, TDS, TR, TL, SK, NH, SVG, TV. Project administration: MP, TDS, SVG, TV. Resources: JD, PS, SDM, PW, JVA, CVS, LL, AG, AM, JD, FN, TV. Supervision: NH,
Data availability statement
Data are available based on a motivated request sent to [email protected] and after a MTA.
vAcknowledgements
We thank Harry Dalton for helpful discussions on the national data collection and clinical outcome analysis and Christophe Conrad for his help in collecting patients data. The authors also especially thank all physicians from the following centres who participated in the study: Algemeen Ziekenhuis Alma, Eeklo; Algemeen Medisch Laboratorium, Antwerpen; Algemeen Stedelijk Ziekenhuis, Aalst; Algemeen Ziekenhuis Delta, Roeselare; Algemeen Ziekenhuis Delta, Torhout; Algemeen Ziekenhuis Nikolaas,
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Author names in bold designate shared co-first authorship
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These authors contributed equally.
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These authors are joint senior authors on this work.