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BACKGROUND Different forms of pregenomic and other hepatitis B virus (HBV) RNA have been detected in patients’ sera. These circulating HBV-RNAs may be useful for monitoring covalently closed circular DNA activity, and predicting hepatitis B e-antigen seroconversion or viral rebound after nucleos(t)ide analog cessation. Data on serum HBV-RNA quasispecies, however, is scarce. It is therefore important to develop methodologies to thoroughly analyze this quasispecies, ensuring the elimination of any residual HBV-DNA. Studying circulating HBV-RNA quasispecies may facilitate achieving functional cure of HBV infection. AIM To establish a next-generation sequencing (NGS) methodology for analyzing serum HBV-RNA and comparing it with DNA quasispecies. METHODS Thirteen untreated chronic hepatitis B patients, showing different HBV-genotypes and degrees of severity of liver disease were enrolled in the study and a serum sample with HBV-DNA > 5 Log10 IU/mL and HBV-RNA > 4 Log10 copies/mL was taken from each patient. HBV-RNA was treated with DNAse I to remove any residual DNA, and the region between nucleotides (nt) 1255-1611 was amplified using a 3-nested polymerase chain reaction protocol, and analyzed with NGS. Variability/conservation and complexity was compared between HBV-DNA and RNA quasispecies. RESULTS No HBV-DNA contamination was detected in cDNA samples from HBV-RNA quasispecies. HBV quasispecies complexity showed heterogeneous behavior among patients. The Rare Haplotype Load at 1% was greater in DNA than in RNA quasispecies, with no statistically significant differences (P = 0.1641). Regarding conservation, information content was equal in RNA and DNA quasispecies in most nt positions [218/357 (61.06%)]. In 102 of the remaining 139 (73.38%), HBV-RNA showed slightly higher variability. Sliding window analysis identified 4 hyper-conserved sequence fragments in each quasispecies, 3 of them coincided between the 2 quasispecies: nts 1258-1286, 1545-1573 and 1575-1604. The 2 hyper-variable sequence fragments also coincided: nts 1311-1344 and 1461-1485. Sequences between nts 1519-1543 and 1559-1587 were only hyper-conserved in HBV-DNA and RNA, respectively. CONCLUSION Our methodology allowed analyzing HBV-RNA quasispecies complexity and conservation without interference from HBV-DNA. Thanks to this, we have been able to compare both quasispecies in the present study.

The changes occurring in viral quasispecies populations during infection have been monitored using diversity indices, nucleotide diversity, and several other indices to summarize the quasispecies structure in a single value. In this study, we present a method to partition quasispecies haplotypes into four fractions according to their fitness: the master haplotype, rare haplotypes at two levels (those present at 1%, but less than that of the master haplotype. We propose that by determining the changes occurring in the volume of the four quasispecies fitness fractions together with those of the Hill number profile we will be able to visualize and analyze the molecular changes in the composition of a quasispecies with time. To develop this concept, we used three data sets: a technical clone of the complete SARS-CoV-2 spike gene, a subset of data previously used in a study of rare haplotypes, and data from a clinical follow-up study of a patient chronically infected with HEV and treated with ribavirin. The viral response to ribavirin mutagenic treatment was selection of a rich set of synonymous haplotypes. The mutation spectrum was very complex at the nucleotide level, but at the protein (phenotypic/functional) level the pattern differed, showing a highly prevalent master phenotype. We discuss the putative implications of this observation in relation to mutagenic antiviral treatment., This study was partially supported by Plan Estratègic de Recerca i Innovació en Salut (PERIS)—Direcció General de Recerca i Innovació en Salut (DGRIS), Catalan Health Ministry, Generalitat de Catalunya; Centro para el Desarrollo Tecnológico Industrial (CDTI) from the Spanish Ministry of Economy and Business, grant number IDI-20200297; grant PI19/00301 from Instituto de Salud Carlos III cofinanced by the European Regional Development Fund (ERDF), and Gilead’s biomedical research project GLD21/00006. Work at CBMSO in Madrid was supported by grant PID2020-113888RB-100 from Ministerio de Ciencia e Innovación and S2018/BAA-4370 (PLATESA2 from Comunidad de Madrid/FEDER).

SARS-CoV-2; Mutacions; Quasiespècie SARS-CoV-2; Mutaciones; Cuasiespecie SARS-CoV-2; Mutations; Quasispecies A common trait among RNA viruses is their high capability to acquire genetic variability due to viral and host mechanisms. Next-generation sequencing (NGS) analysis enables the deep study of the viral quasispecies in samples from infected individuals. In this study, the viral quasispecies complexity and single nucleotide polymorphisms of the SARS-CoV-2 spike gene of coronavirus disease 2019 (COVID-19) patients with mild or severe disease were investigated using next-generation sequencing (Illumina platform). SARS-CoV-2 spike variability was higher in patients with long-lasting infection. Most substitutions found were present at frequencies lower than 1%, and had an A → G or T → C pattern, consistent with variants caused by adenosine deaminase acting on RNA-1 (ADAR1). ADAR1 affected a small fraction of replicating genomes, but produced multiple, mainly non-synonymous mutations. ADAR1 editing during replication rather than the RNA-dependent RNA polymerase (nsp12) was the predominant mechanism generating SARS-CoV-2 genetic variability. However, the mutations produced are not fixed in the infected human population, suggesting that ADAR1 may have an antiviral role, whereas nsp12-induced mutations occurring in patients with high viremia and persistent infection are the main source of new SARS-CoV-2 variants. This study was supported by the Direcció General de Recerca i Innovació en Salut (DGRIS) of the Catalan Health Ministry, Generalitat de Catalunya, through the Vall d’Hebron Institut de Recerca (VHIR); the European Regional Development Fund (ERDF) “A way to achieve Europe” by the Spanish Network for Research in Infectious Diseases [grant number REIPI RD16/0016/0003]; Instituto de Salud Carlos III [grant number FIS PI19/00301]; and Centro para el Desarrollo Tecnologico Industrial (CDTI) from the Ministry of Economic Affairs and Digital Transformation [grant number IDI-20200297].

Haplotipos; Enfermedades infecciosas; Mutación Haplotips; Enfermetats infeccioses; Mutació Haplotypes; Infectious diseases; Mutation Patients with HBeAg-negative chronic infection (CI) have not been extensively studied because of low viremia. The HBx protein, encoded by HBX, has a key role in viral replication. Here, we analyzed the viral quasispecies at the 5′ end of HBX in CI patients and compared it with that of patients in other clinical stages. Fifty-eight HBeAg-negative patients were included: 16 CI, 19 chronic hepatitis B, 16 hepatocellular carcinoma and 6 liver cirrhosis. Quasispecies complexity and conservation were determined in the region between nucleotides 1255 and 1611. Amino acid changes detected were tested in vitro. CI patients showed higher complexity in terms of mutation frequency and nucleotide diversity and higher quasispecies conservation (p

Introduction Hepatitis B virus (HBV) causes a complex and persistent infection with a major impact on patients health. Viral-genome sequencing can provide valuable information for characterizing virus genotype, infection dynamics and drug and vaccine resistance. Areas covered This article reviews the current literature to describe the next-generation sequencing progress that facilitated a more comprehensive study of HBV quasispecies in diagnosis and clinical monitoring. Expert opinion HBV variability plays a key role in liver disease progression and treatment efficacy. Second-generation sequencing improved the sensitivity for detecting and quantifying mutations, mixed genotypes and viral recombination. Third-generation sequencing enables the analysis of the entire HBV genome, although the high error rate limits its use in clinical practice.

We read with interest the article by Mak et al. (1) that assessed HBV-RNA profiles using real-time PCR (m2000 system, Abbott Diagnostics, Abbott Park, USA), and their correlation with other viral biomarkers, in a large cohort of chronic hepatitis-B (CHB) patients, either treatment-naive or receiving nucleos(t)ide analogues. The authors reported median serum levels of HBV-DNA higher than HBV-RNA by 1-2 log10 in both HBeAg-positive and HBeAg-negative treatment-naive patients.

[Abstract] A percentage of hepatitis C virus (HCV)-infected patients fail direct acting antiviral (DAA)-based treatment regimens, often because of drug resistance-associated substitutions (RAS). The aim of this study was to characterize the resistance profile of a large cohort of patients failing DAA-based treatments, and investigate the relationship between HCV subtype and failure, as an aid to optimizing management of these patients. A new, standardized HCV-RAS testing protocol based on deep sequencing was designed and applied to 220 previously subtyped samples from patients failing DAA treatment, collected in 39 Spanish hospitals. The majority had received DAA-based interferon (IFN) α-free regimens; 79% had failed sofosbuvir-containing therapy. Genomic regions encoding the nonstructural protein (NS) 3, NS5A, and NS5B (DAA target regions) were analyzed using subtype-specific primers. Viral subtype distribution was as follows: genotype (G) 1, 62.7%; G3a, 21.4%; G4d, 12.3%; G2, 1.8%; and mixed infections 1.8%. Overall, 88.6% of patients carried at least 1 RAS, and 19% carried RAS at frequencies below 20% in the mutant spectrum. There were no differences in RAS selection between treatments with and without ribavirin. Regardless of the treatment received, each HCV subtype showed specific types of RAS. Of note, no RAS were detected in the target proteins of 18.6% of patients failing treatment, and 30.4% of patients had RAS in proteins that were not targets of the inhibitors they received. HCV patients failing DAA therapy showed a high diversity of RAS. Ribavirin use did not influence the type or number of RAS at failure. The subtype-specific pattern of RAS emergence underscores the importance of accurate HCV subtyping. The frequency of “extra-target” RAS suggests the need for RAS screening in all three DAA target regions. Ministerio de Economía y Empresa; IDI-20151125 Ministerio de Ciencia, Innovación y Universidades; SAF SAF 2017-87846-R

We aimed to investigate HBx genetic elements correlated with hepatitis B virus (HBV) -related hepatocellular carcinoma (HCC) and their impact on (a) HBV replicative efficiency, (b) HBx binding to circular covalently closed DNA (cccDNA), (c) apoptosis and cell-cycle progression, and (d) HBx structural stability.This study included 123 individuals chronically infected with HBV: 27 with HCC (77.9% (21/27) genotype D; 22.1% (6/27) genotype A) and 96 without HCC (75% (72/96) genotype D; 25.0% (24/96) genotype A). HepG2 cells were transfected by wild-type or mutated linear HBV genome to assess pre-genomic RNA (pgRNA) and core-associated HBV-DNA levels, HBx-binding onto cccDNA by chromatin immunoprecipitation-based quantitative assay, and rate of apoptosis and cell-cycle progression by cytofluorimetry.F30V was the only HBx mutation correlated with HCC (18.5% (5/27) in HCC patients versus 1.0% (1/96) in non-HCC patients, p 0.002); a result confirmed by multivariate analysis. In vitro, F30V determined a 40% and 60% reduction in pgRNA and core-associated HBV-DNA compared with wild-type (p0.05), in parallel with a significant decrease of HBx binding to cccDNA and decreased HBx stability. F30V also decreased the percentage of apoptotic cells compared with wild-type (14.8 ± 6.8% versus 19.1 ± 10.1%, p0.01, without affecting cell-cycle progression) and increased the probability of HBx-Ser-31 being phosphorylated by PI3K-Akt kinase (known to promote anti-apoptotic activity).F30V was closely correlated with HBV-induced HCC in vivo, reduced HBV replicative efficiency by affecting HBx-binding to cccDNA and increased anti-apoptotic HBx activity in vitro. This suggests that F30V (although hampering HBV's replicative capacity) may promote hepatocyte survival, so potentially allowing persistent production of viral progeny and initiating HBV-driven hepatocarcinogenesis. Investigation of viral genetic markers associated with HCC is crucial to identify those patients at higher risk of HCC, who hence deserve intensive liver monitoring and/or early anti-HBV therapy.

Hepatitis D virus (HDV) is a hepatotropic subviral infectious agent, obligate satellite of the Hepatitis B virus (HBV) and is highly related to viroids. HDV affects around 5% of the 257 million chronic HBV-carriers worldwide, leading to the most severe form of chronic viral hepatitis. Interferon alpha is the only approved treatment for chronic hepatitis D, albeit with low response rates (around 20%-30%). New antiviral strategies are currently under study. Due to the high viral evolution rates (10-3 to 10-4 substitutions/site/year) HDV forms an extremely complex viral population (quasispecies) that can be studied by Next-Generation Sequencing. Therefore, although specific viral resistance in HDV infection has not been reported, it cannot be completely discarded.

AIM To detect hyper-conserved regions in the hepatitis B virus (HBV) X gene (HBX) 5’ region that could be candidates for gene therapy. METHODS The study included 27 chronic hepatitis B treatment-naive patients in various clinical stages (from chronic infection to cirrhosis and hepatocellular carcinoma, both HBeAg-negative and HBeAg-positive), and infected with HBV genotypes A-F and H. In a serum sample from each patient with viremia > 3.5 log IU/mL, the HBX 5’ end region [nucleotide (nt) 1255-1611] was PCR-amplified and submitted to next-generation sequencing (NGS). We assessed genotype variants by phylogenetic analysis, and evaluated conservation of this region by calculating the information content of each nucleotide position in a multiple alignment of all unique sequences (haplotypes) obtained by NGS. Conservation at the HBx protein amino acid (aa) level was also analyzed. RESULTS NGS yielded 1333069 sequences from the 27 samples, with a median of 4578 sequences/sample (2487-9279, IQR 2817). In 14/27 patients (51.8%), phylogenetic analysis of viral nucleotide haplotypes showed a complex mixture of genotypic variants. Analysis of the information content in the haplotype multiple alignments detected 2 hyper-conserved nucleotide regions, one in the HBX upstream non-coding region (nt 1255-1286) and the other in the 5’ end coding region (nt 1519-1603). This last region coded for a conserved amino acid region (aa 63-76) that partially overlaps a Kunitz-like domain. CONCLUSION Two hyper-conserved regions detected in the HBX 5’ end may be of value for targeted gene therapy, regardless of the patients’ clinical stage or HBV genotype.

To compare the kinetics of integration, p24 production and equilibrium of the different HIV-DNA forms in human primary cells in the presence/absence of integrase-inhibitors (INIs) in vitro. Monocyte-derived-macrophages (MDMs), CD4+ T-cells and peripheral blood mononuclear cells (PBMCs) were infected with HIV-1 in the presence/absence of raltegravir and dolutegravir. HIV-DNA levels and p24 production were measured by qPCR and ELISA assays, respectively. In the absence of INIs, levels of HIV-DNA forms were initially very low, with an increase in the integration process starting at 3 dpi. HIV-DNA increased more slowly in MDMs than it did in CD4+ T-cells and PMBCs peaking at 21 dpi with a mean of 1580 (±890) and 615 (±37) copies/103 cells for proviral and unintegrated HIV-DNA, and 455,972 (±213,255) pg/mL of p24 at the same time point. In CD4+ T-cells the proviral HIV-DNA increased together with unintegrated HIV-DNA peaking at 7 dpi (583 ± 261 and 338 ± 254 copies/103 cells) when the p24 was 218,000 (±75,600) pg/mL. A similar trend was observed in PBMCs (494 ± 361 and 350 ± 123 copies/103 cells for proviral and unintegrated HIV-DNA, and p24 production of 149,400 ± 131,800 pg/mL). Both INIs inhibited viral replication and integration in all the cell types that were tested, especially starting at 3 dpi. However, a small but measurable amount of HIV-DNA ( In conclusion, our study showed differences in HIV-DNA kinetic integration between CD4+ T-cells and MDMs, which could explain the divergent kinetics of viral-replication. Both INIs inhibited HIV-1 integration and replication with no difference found between CD4+ T-cells and MDMs. However, residual HIV-DNA remained detectable up to 30 dpi in INI-treated MDMs although complete inhibition of HIV replication was achieved. The clinical significance of this minor DNA persistence deserves further investigation considering the role of macrophages as reservoirs.

// Romina Salpini 1, * , Matteo Surdo 1, * , Nadia Warner 2 , Maria Francesca Cortese 1 , Danny Colledge 2 , Sally Soppe 2 , Maria Concetta Bellocchi 1 , Daniele Armenia 1 , Luca Carioti 1 , Fabio Continenza 3 , Domenico Di Carlo 1 , Patrizia Saccomandi 1 , Carmen Mirabelli 1, 4 , Michela Pollicita 1 , Roberta Longo 5 , Sara Romano 5 , Giuseppina Cappiello 5 , Alberto Spano 5 , Pascale Trimoulet 6 , Herve Fleury 6 , Jacopo Vecchiet 7 , Nerio Iapadre 8 , Angelo Barlattani 9 , Ada Bertoli 1 , Terenzio Mari 10 , Caterina Pasquazzi 11 , Gabriele Missale 12 , Cesare Sarrecchia 13 , Elisa Orecchini 14 , Alessandro Michienzi 14 , Massimo Andreoni 13 , Simona Francioso 15 , Mario Angelico 15 , Jens Verheyen 16 , Francesca Ceccherini-Silberstein 1 , Stephen Locarnini 2 , Carlo Federico Perno 1 , Valentina Svicher 1 1 Department of Experimental Medicine and Surgery, University of Rome “Tor Vergata” Rome, Italy 2 Research and Molecular Development, Victorian Infectious Diseases Reference Laboratory, North Melbourne, Victoria, Australia 3 Laboratory of Monitoring Antiviral Drugs, National Institute for Infectious Diseases (INMI) “Lazzaro Spallanzani” Rome, Italy 4 Institut Pasteur, Unite de Biologie des Virus Enteriques, Paris, France 5 Unit of Microbiology, “S. Pertini Hospital”, Rome, Italy 6 Laboratoire de Microbiologie Fondamentale et Pathogenicite, Hopital Pellegrin Tripode, Bordeaux, France 7 Department of Medicine and Aging Sciences, “SS Annunziata” Hospital, Chieti, Italy 8 Infectious Diseases Unit, “S Salvatore” Hospital, L'Aquila, Italy 9 Hepatology Unit, “S Giacomo” Hospital, Rome, Italy 10 Hepatology Unit, “Regina Margherita” Hospital, Rome, Italy 11 Hepato-Infectivology Unit, “S Andrea” Hospital, Rome, Italy 12 Hospital of Parma, Parma, Italy 13 Tor Vergata University Hospital, Infectious Diseases Unit, Rome, Italy 14 Department of Biomedicine and Prevention, University of Rome “Tor Vergata” Rome, Italy 15 Tor Vergata University Hospital, Hepatology Unit, Rome, Italy 16 Institute of Virology, University Hospital, University of Duisburg-Essen, Essen, Germany * These authors have contributed equally to this work Correspondence to: Carlo Federico Perno, email: cf.perno@uniroma2.it Valentina Svicher, email: valentina.svicher@uniroma2.it Keywords: hepatitis B, hepatocellular carcinoma, hepatitis B surface antigen, HBsAg mutations, cell proliferation Received: November 25, 2016 Accepted: December 27, 2016 Published: February 01, 2017 ABSTRACT Background: An impaired HBsAg-secretion can increase HBV oncogenic-properties. Here, we investigate genetic-determinants in HBsAg correlated with HBV-induced hepatocellular carcinoma (HCC), and their impact on HBsAg-secretion and cell-proliferation. Methods: This study included 128 chronically HBV-infected patients: 23 with HCC (73.9% D; 26.1% A HBV-genotype), and 105 without cirrhosis/HCC (72.4% D, 27.6% A) as reference-group. The impact of mutations on HBsAg-secretion was assessed by measuring the ratio [secreted/intracellular HBsAg] until day 5 post-transfection. The impact of mutations on cell-cycle advancement was assessed by flow-cytometry. Results: Two HBsAg mutations significantly correlated with HCC: P203Q (17.4% [4/23] in HCC vs 1.0% [1/105] in non-HCC, P=0.004); S210R (34.8% [8/23] in HCC vs 3.8% [4/105] in non-HCC, P

Objectives To evaluate the replication capacity and phenotypic susceptibility to dolutegravir and raltegravir of wild-type and raltegravir-resistant HIV-1 strains in several cellular systems. Methods The antiviral activities of dolutegravir and raltegravir were evaluated in human primary monocyte-derived macrophages (MDMs), peripheral blood mononuclear cells (PBMCs) and C8166 T lymphocytic cells. The following raltegravir resistance mutations were analysed: N155H, Y143C, N155H + Y143C and G140S+Q148H. Results In the absence of drug, the replication capacity of raltegravir-resistant viruses was strongly reduced compared with wild-type in all cellular models analysed. In MDMs and PBMCs, a dramatic decrease in viral replication was observed for the double mutants N155H + Y143C and G140S + Q148H (ranging from 0.1% to 2.5% compared with wild-type). In MDMs, dolutegravir exhibited high potency, with EC50 and EC90 values of 1.1 ± 0.9 and 5.5 ± 3.4 nM, respectively (comparable to raltegravir). These values (particularly for EC90) were significantly lower than those observed in PBMCs (EC50: 2.7 ± 1.5 nM; EC90: 14.8 ± 0.9 nM) and C8166 cells (EC50: 5.5 ± 0.8 nM; EC90: 64.8 ± 5.8 nM). In all cellular models analysed, dolutegravir showed full efficacy against N155H and Y143C mutants (dolutegravir fold-change resistance ranging from 0.1 to 1.4; raltegravir fold-change resistance ranging from 0.1 to 10.3). In C8166 (the only cell model in which replication capacity was sufficient to perform the test) dolutegravir showed full efficacy against mutations N155H + Y143C (dolutegravir fold-change resistance: 0.6) and a slightly lower activity against G140S+Q148H (dolutegravir fold-change resistance: 2.1). Conclusions Dolutegravir is effective in different HIV cellular targets and against raltegravir-resistant mutants. The high efficacy of dolutegravir in MDMs (cells with limited metabolism) has relevant clinical implications in light of the role of MDMs in the transmission of HIV infection and dissemination in different body compartments.

R. Salpini1, M. Surdo1, N. Warner2, M.F. Cortese1, C. Mirabelli 1,3, D. Colledge2, S. Soppe2, P. Saccomandi1, M. Pollicita1, R. Longo4, S. Romano4, G. Cappiello4, A. Spano4, P. Trimoulet5, H. Fleury5, J. Vecchiet6, N. Iapadre7, A. Barlattani8, A. Bertoli 1, T. Mari9, C. Pasquazzi10, G. Missale11, C. Sarrecchia12, E. Orecchini13, A. Michienzi13, M. Andreoni12, S. Francioso14, M. Angelico14, F. Ceccherini-Silberstein1, S. Locarnini2, C.F. Perno1, V. Svicher1 1 Department of Experimental Medicine, University of Rome “Tor Vergata” Rome, Italy 2 Research and Molecular Development, Victorian Infectious Diseases Reference Laboratory, North Melbourne, Victoria, Australia 3 Institut Pasteur, Unite de Biologie des virus enteriques, 25 rue du Dr Roux, 75015 Paris, France 4 S. Pertini Hospital”, Rome, Italy 5 Hopital Pellegrin Tripode, Bordeaux, France 6 SS Annunziata” Hospital, Chieti, Italy 7 S Salvatore” Hospital, L’Aquila, Italy 8 “S Giacomo” Hospital, Rome, Italy 9 “Regina Margherita” Hospital, Rome, Italy 10 “S Andrea” Hospital, Rome, Italy 11 Hospital of Parma, Parma, Italy 12 Tor Vergata University Hospital, Infectious Diseases Unit, Rome, Italy 13 Department of Biomedicine and Prevention, University of Rome “Tor Vergata” Rome, Italy 14 Tor Vergata University Hospital, Hepatology Unit, Rome, Italy

Background and Aims: Every year globally WHO reports nearly 20 million Hepatitis E virus (HEV) infections. The disease has potential to cause massive epidemics. The reservoir of HEV during interepidemic period in India is not well characterized, with evidences of deficient zoonotic links. Further, the sporadic cases usually lack history of contact with clinically overt HEV patients. In the present context the occurrence of subclinical HEV as a possible reservoir of infection in endemic region was evaluated. Methods: Blood samples were collected from 67 apparently-healthy individuals and 10 acute viral hepatitis (AVH) patients during two HEV outbreaks in North India. The serum samples were tested for anti-HEV IgM, IgG, HEV-IgG avidity-index, HEV viral-load and conventional-PCR followed by sequencing and phylogenetic analysis. Results: A total of 14 (20.89%) apparently-healthy individuals showed presence of both anti-HEV IgM and IgG. Based on HEVIgG avidity-index, 9 apparently-healthy individuals (64.28%) had secondary-exposure, 4 (28.57%) had primary-exposure, while one patient had intermediate-avidity. Subclinical subjects with primaryexposure had significantly higher anti-HEV IgM index as compared to secondary-exposure. Viral-load in clinically jaundiced patients was significantly higher as compared to subclinical subjects (p < 0.0001). Phylogenetic analysis showed HEV sequences retrieved from subclinical individuals (Genotype 1a) clustered along with AVH patients reported in the same outbreak suggesting matched origin. The significantly low viral-load in subclinical subjects hints towards the dose dependency for progression of clinical manifestation. Conclusions: We document subclinical passage of HEV occurs without producing clinically overt hepatitis goes un-noticed which, in turn helps maintaining the virus in nature possibly leading to its endemicity.