Two mutations in the ORF1 of genotype 1 hepatitis E virus enhance virus replication and may associate with fulminant hepatic failure.

Hepatitis E virus (HEV) infection in pregnant women has a high incidence of developing fulminant hepatic failure (FHF) with significant mortality. Multiple amino acid changes in genotype 1 HEV (HEV-1) are reportedly linked to FHF clinical cases, but experimental confirmation of the roles of these changes in FHF is lacking. By utilizing the HEV-1 indicator replicon and infectious clone, we generated 11 HEV-1 single mutants, each with an individual mutation, and investigated the effect of these mutations on HEV replication and infection in human liver cells. We demonstrated that most of the mutations actually impaired HEV-1 replication efficiency compared with the wild type (WT), likely due to altered physicochemical properties and structural conformations. However, two mutations, A317T and V1120I, significantly increased HEV-1 replication. Notably, these two mutations simultaneously occurred in 100% of 21 HEV-1 variants from patients with FHF in Bangladesh. We further created an HEV-1 A317T/V1120I double mutant and found that it greatly enhanced HEV replication, which may explain the rapid viral replication and severe disease. Furthermore, we tested the effect of these FHF-associated mutations on genotype 3 HEV (HEV-3) replication and found that all the mutants had a reduced level of replication ability and infectivity, which is not unexpected due to distinct infection patterns between HEV-1 and HEV-3. Additionally, we demonstrated that these FHF-associated mutations do not appear to alter their sensitivity to ribavirin (RBV), suggesting that ribavirin remains a viable option for antiviral therapy for patients with FHF. The results have important implications for understanding the mechanism of HEV-1-associated FHF.

An Arginine-Rich Motif in the ORF2 capsid protein regulates the hepatitis E virus lifecycle and interactions with the host cell.

Hepatitis E virus (HEV) infection is the most common cause of acute viral hepatitis worldwide. Hepatitis E is usually asymptomatic and self-limiting but it can become chronic in immunocompromised patients and is associated with increased fulminant hepatic failure and mortality rates in pregnant women. HEV genome encodes three proteins including the ORF2 protein that is the viral capsid protein. Interestingly, HEV produces 3 isoforms of the ORF2 capsid protein which are partitioned in different subcellular compartments and perform distinct functions in the HEV lifecycle. Notably, the infectious ORF2 (ORF2i) protein is the structural component of virions, whereas the genome-free secreted and glycosylated ORF2 proteins likely act as a humoral immune decoy. Here, by using a series of ORF2 capsid protein mutants expressed in the infectious genotype 3 p6 HEV strain as well as chimeras between ORF2 and the CD4 glycoprotein, we demonstrated how an Arginine-Rich Motif (ARM) located in the ORF2 N-terminal region controls the fate and functions of ORF2 isoforms. We showed that the ARM controls ORF2 nuclear translocation likely to promote regulation of host antiviral responses. This motif also regulates the dual topology and functionality of ORF2 signal peptide, leading to the production of either cytosolic infectious ORF2i or reticular non-infectious glycosylated ORF2 forms. It serves as maturation site of glycosylated ORF2 by furin, and promotes ORF2-host cell membrane interactions. The identification of ORF2 ARM as a unique central regulator of the HEV lifecycle uncovers how viruses settle strategies to condense their genetic information and hijack cellular processes.

Characterization of highly expressed novel hub genes in hepatitis E virus chronicity in rabbits: a bioinformatics and experimental analysis.

BACKGROUND: Hepatitis E virus (HEV), which is the leading cause of acute viral hepatitis worldwide, usually causes self-limited infections in common individuals. However, it can lead to chronic infection in immunocompromised individuals and its mechanisms remain unclear. Rabbits are the natural host of HEV, and chronic HEV infections have been observed in rabbits. Therefore, we aimed to investigate potential key genes in HEV chronicity process in rabbits. In this study, both bioinformatics and experimental analysis were performed to deepen the understanding of hub genes in HEV chronic infection in rabbits. RESULTS: Ninety-four candidate differentially expressed genes (DEGs) and the pathways they enriched were identified to be related with HEV chronicity. A total of 10 hub genes were found by protein-protein interaction (PPI) network construction. Rabbits of group P (n = 4) which showed symptoms of chronic HEV infection were selected to be compared with HEV negative rabbits (group N, n = 6). By detecting the identified hub genes in groups P and N by real-time PCR, we found that the expressions of MX1, OAS2 and IFI44 were significantly higher in group P (P < 0.05). CONCLUSIONS: In this work, we presented that MX1, OAS2 and IFI44 were significantly upregulated in HEV chronic infected rabbits, indicating that they may be involved in the pathogenesis of HEV chronicity.

Origin, antigenicity, and function of a secreted form of ORF2 in hepatitis E virus infection.

The enterically transmitted hepatitis E virus (HEV) adopts a unique strategy to exit cells by cloaking its capsid (encoded by the viral ORF2 gene) and circulating in the blood as "quasi-enveloped" particles. However, recent evidence suggests that the majority of the ORF2 protein present in the patient serum and supernatants of HEV-infected cell culture exists in a free form and is not associated with virus particles. The origin and biological functions of this secreted form of ORF2 (ORF2S) are unknown. Here we show that production of ORF2S results from translation initiated at the previously presumed AUG start codon for the capsid protein, whereas translation of the actual capsid protein (ORF2C) is initiated at a previously unrecognized internal AUG codon (15 codons downstream of the first AUG). The addition of 15 amino acids to the N terminus of the capsid protein creates a signal sequence that drives ORF2S secretion via the secretory pathway. Unlike ORF2C, ORF2S is glycosylated and exists as a dimer. Nonetheless, ORF2S exhibits substantial antigenic overlap with the capsid, but the epitopes predicted to bind the putative cell receptor are lost. Consistent with this, ORF2S does not block HEV cell entry but inhibits antibody-mediated neutralization. These results reveal a previously unrecognized aspect in HEV biology and shed new light on the immune evasion mechanisms and pathogenesis of this virus.

Interplay between Hepatitis E Virus and Host Cell Pattern Recognition Receptors.

Hepatitis E virus (HEV) usually causes self-limiting acute hepatitis, but the disease can become chronic in immunocompromised individuals. HEV infection in pregnant women is reported to cause up to 30% mortality, especially in the third trimester. Additionally, extrahepatic manifestations like neuronal and renal diseases and pancreatitis are also reported during the course of HEV infection. The mechanism of HEV pathogenesis remains poorly understood. Innate immunity is the first line of defense triggered within minutes to hours after the first pathogenic insult. Growing evidence based on reverse genetics systems, in vitro cell culture models, and representative studies in animal models including non-human primates, has implicated the role of the host's innate immune response during HEV infection. HEV persists in presence of interferons (IFNs) plausibly by evading cellular antiviral defense. This review summarizes our current understanding of recognizing HEV-associated molecular patterns by host cell Pattern Recognition Receptors (PRRs) in eliciting innate immune response during HEV infection as well as mechanisms of virus-mediated immune evasion.

IFN-λ3 as a host immune response in acute hepatitis E virus infection.

BACKGROUND AND AIM: Hepatitis E virus (HEV) is mainly transmitted orally, either waterborne or zoonotic foodborne. Intestinal viruses such as rotavirus are known to induce type III interferon (IFN) in the gastrointestinal (GI) tract where type III IFN dominantly functions in comparison with type I IFN. Therefore, the aim of this study is to investigate the significance of type III IFN (IFN-λ3) in acute hepatitis E. METHODS: IFN-λ3 and HEV RNA levels in the sera of patients with acute HEV infection and in the supernatant of HEV-inoculated cells were measured, using an in-house high-sensitivity method and reverse transcription-polymerase chain reaction, respectively. RESULTS: High serum IFN-λ3 levels were found in the early phase of acute HEV infection, which normalized after resolution. Interestingly, serum IFN-λ3 levels correlated well with serum HEV RNA titers in the same sera, both of which showed the peak before the robust increase of transaminases. In vitro experiments demonstrated that HEV replicated well in the cells with little IFN-λ3 induction (Caco-2, A549) and recombinant IFN-λ3 inhibited HEV replication in a dose-dependent manner. In contrast, in HT-29 cells, a colon cancer cell line, HEV poorly replicated and induced IFN-λ3 in a titer-dependent manner. CONCLUSIONS: These clinical and experimental observations suggest that HEV induced IFN-λ3 as a host innate immune response, which may play a protective role against HEV.

Hepatitis E virus polymerase binds to IFIT1 to protect the viral RNA from IFIT1-mediated translation inhibition.

Hepatitis E virus (HEV) induces interferons and regulates the induction of interferon-stimulated genes (ISGs) in the host cell. HEV infection has been shown to promote the expression of different ISGs, such as ISG15, IFIT1, MX1, RSAD2/Viperin and CxCL10, in cell culture and animal models. Interferon-induced protein with tetratricopeptide repeat 1 (IFIT1) is an ISG-encoded protein that inhibits the translation of viral RNA, having 5'-triphosphate or the mRNA lacking 2'-O-methylation on the 5'cap. In this study, we found that IFIT1 binds to HEV RNA to inhibit its translation. HEV replication is also restricted in hepatoma cells with overexpressed IFIT1. However, despite this binding of IFIT1 to HEV RNA, HEV successfully replicates in hepatoma cells in the infection scenario. In an effort to identify the underlying mechanism, we found that HEV RNA-dependent RNA polymerase (RdRp) binds to IFIT1, thereby protecting the viral RNA from IFIT1-mediated translation inhibition. RdRp sequesters IFIT1, resulting in the successful progression of viral replication in the infected cells. Thus, we discovered a distinct pro-viral role of HEV RdRp that is crucial for successful infection in the host, and propose a unique mechanism developed by HEV to overcome IFIT1-mediated host immune response.

Hepatitis E virus infection after haploidentical haematopoietic stem cell transplantation: incidence and clinical course.

Hepatitis E virus (HEV) is increasingly found to cause hepatitis in allogeneic haematopoietic stem cell transplantation (HSCT) patients. However, little is known about HEV infection in patients receiving haploidentical HSCT (haplo-HSCT). Here, we retrospectively evaluate the incidence and clinical course of HEV infection in haplo-HSCT patients. From January 2014 to July 2017, 177 patients with unexplained elevated transaminases after receiving haplo-HSCT at Peking University Institute of Haematology were screened for HEV using HEV serology. HEV RNA was assessed in blood samples when HEV-IgG and/or IgM antibodies were positive. Acute HEV infection was identified in 7 patients (3·9%), 1 of whom had developed a chronic HEV infection. The median time from haplo-HSCT to HEV infection was 17·5 (range, 6-55) months. HEV infection was confirmed by the presentation of anti-HEV IgM + anti-HEV IgG (rising) (n = 5) or HEV-RNA + anti-HEV IgM + anti-HEV IgG (n = 2). None of the patients died of HEV infection directly: 2 patients with HEV infection died showing signs of ongoing hepatitis, and 5 patients cleared HEV with a median duration of HEV infection of 1·5 (range, 1·0-5·7) months. In conclusion, HEV infection is a rare but serious complication after haplo-HSCT. We recommend screening of HEV in haplo-HSCT.

Activities of Thrombin and Factor Xa Are Essential for Replication of Hepatitis E Virus and Are Possibly Implicated in ORF1 Polyprotein Processing.

Hepatitis E virus (HEV) is a clinically important positive-sense RNA virus. The ORF1 of HEV encodes a nonstructural polyprotein of 1,693 amino acids. It is not clear whether the ORF1 polyprotein (pORF1) is processed into distinct enzymatic domains. Many researchers have attempted to understand the mechanisms of pORF1 processing. However, these studies gave various results and could never convincingly establish the mechanism of pORF1 processing. In this study, we demonstrated the possible role of thrombin and factor Xa in pORF1 processing. We observed that the HEV pORF1 polyprotein bears conserved cleavage sites of thrombin and factor Xa. Using a reverse genetics approach, we demonstrated that an HEV replicon having mutations in the cleavage sites of either thrombin or factor Xa could not replicate efficiently in cell culture. Further, we demonstrated in vitro processing when we incubated recombinant pORF1 fragments with thrombin, and we observed the processing of pORF1 polyprotein. The treatment of a liver cell line with a serine protease inhibitor as well as small interfering RNA (siRNA) knockdown of thrombin and factor Xa resulted in significant reduction in the replication of HEV. Thrombin and factor Xa have been well studied for their roles in blood clotting. Both of these proteins are believed to be present in the active form in the blood plasma. Interestingly, in this report, we demonstrated the presence of biologically active thrombin and factor Xa in a liver cell line. The results suggest that factor Xa and thrombin are essential for the replication of HEV and may be involved in pORF1 polyprotein processing of HEV.IMPORTANCE Hepatitis E virus (HEV) causes a liver disorder called hepatitis in humans, which is mostly an acute and self-limiting infection in adults. A high mortality rate of about 30% is observed in HEV-infected pregnant women in developing countries. There is no convincing opinion about HEV ORF1 polyprotein processing owing to the variability of study results obtained so far. HEV pORF1 has cleavage sites for two host cellular serine proteases, thrombin and factor Xa, that are conserved among HEV genotypes. For the first time, this study demonstrated that thrombin and factor Xa cleavage sites on HEV pORF1 are obligatory for HEV replication. Intracellular biochemical activities of the said serine proteases are also essential for efficient HEV replication in cell culture and must be involved in pORF1 processing. This study sheds light on the presence and roles of clotting factors with respect to virus replication in the cells.

Characterization of Three Novel Linear Neutralizing B-Cell Epitopes in the Capsid Protein of Swine Hepatitis E Virus.

Hepatitis E virus (HEV) causes liver disease in humans and is thought to be a zoonotic infection, with domestic animals, including swine and rabbits, being a reservoir. One of the proteins encoded by the virus is the capsid protein. This is likely the major immune-dominant protein and a target for vaccination. Four monoclonal antibodies (MAbs), three novel, 1E4, 2C7, and 2G9, and one previously characterized, 1B5, were evaluated for binding to the capsid protein from genotype 4 swine HEV. The results indicated that 625DFCP628, 458PSRPF462, and 407EPTV410 peptides on the capsid protein comprised minimal amino acid sequence motifs recognized by 1E4, 2C7, and 2G9, respectively. The data suggested that 2C7 and 2G9 epitopes were partially exposed on the surface of the capsid protein. Truncated genotype 4 swine HEV capsid protein (sp239, amino acids 368 to 606) can exist in multimeric forms. Preincubation of swine HEV with 2C7, 2G9, or 1B5 before addition to HepG2 cells partially blocked sp239 cell binding and inhibited swine HEV infection. The study indicated that 2C7, 2G9, and 1B5 partially blocked swine HEV infection of rabbits better than 1E4 or normal mouse IgG. The cross-reactivity of antibodies suggested that capsid epitopes recognized by 2C7 and 2G9 are common to HEV strains infecting most host species. Collectively, MAbs 2C7, 2G9, and 1B5 were shown to recognize three novel linear neutralizing B-cell epitopes of genotype 4 HEV capsid protein. These results enhance understanding of HEV capsid protein structure to guide vaccine and antiviral design.IMPORTANCE Genotype 3 and 4 HEVs are zoonotic viruses. Here, genotype 4 HEV was studied due to its prevalence in human populations and pig herds in China. To improve HEV disease diagnosis and prevention, a better understanding of the antigenic structure and neutralizing epitopes of HEV capsid protein are needed. In this study, the locations of three novel linear B-cell recognition epitopes within genotype 4 swine HEV capsid protein were characterized. Moreover, the neutralizing abilities of three MAbs specific for this protein, 2C7, 2G9, and 1B5, were studied in vitro and in vivo Collectively, these findings reveal structural details of genotype 4 HEV capsid protein and should facilitate development of applications for the design of vaccines and antiviral drugs for broader prevention, detection, and treatment of HEV infection of diverse human and animal hosts.

Hepatitis E virus persists in the presence of a type III interferon response.

The RIG-I-like RNA helicase (RLR)-mediated interferon (IFN) response plays a pivotal role in the hepatic antiviral immunity. The hepatitis A virus (HAV) and the hepatitis C virus (HCV) counter this response by encoding a viral protease that cleaves the mitochondria antiviral signaling protein (MAVS), a common signaling adaptor for RLRs. However, a third hepatotropic RNA virus, the hepatitis E virus (HEV), does not appear to encode a functional protease yet persists in infected cells. We investigated HEV-induced IFN responses in human hepatoma cells and primary human hepatocytes. HEV infection resulted in persistent virus replication despite poor spread. This was companied by a type III IFN response that upregulated multiple IFN-stimulated genes (ISGs), but type I IFNs were barely detected. Blocking type III IFN production or signaling resulted in reduced ISG expression and enhanced HEV replication. Unlike HAV and HCV, HEV did not cleave MAVS; MAVS protein size, mitochondrial localization, and function remained unaltered in HEV-replicating cells. Depletion of MAVS or MDA5, and to a less extent RIG-I, also diminished IFN production and increased HEV replication. Furthermore, persistent activation of the JAK/STAT signaling rendered infected cells refractory to exogenous IFN treatment, and depletion of MAVS or the receptor for type III IFNs restored the IFN responsiveness. Collectively, these results indicate that unlike other hepatotropic RNA viruses, HEV does not target MAVS and its persistence is associated with continuous production of type III IFNs.

Hepatitis E virus blood donor NAT screening: as much as possible or as much as needed?

BACKGROUND: The cost-benefit question of general screening of blood products for the hepatitis E virus (HEV) is currently being discussed. One central question is the need for individual nucleic acid amplification techniques (NAT) screening (ID-NAT) versus minipool NAT screening (MP-NAT) approaches to identify all relevant viremias in blood donors. Here, the findings of ID-NAT versus MP-NAT in pools of 96 samples were compared. STUDY DESIGN AND METHODS: From November 2017 to January 2018, a total of 10,141 allogenic blood donations from 7650 individual German blood donors were screened for the presence of HEV RNA using MP-NAT (96 samples) (RealStar HEV RT-PCR Kit) compared to ID-NAT (cobas HEV assay) on the fully automated cobas 6800 platform. RESULTS: Parallel screening of MP (n = 122, 96 samples/MP) using both methods detected seven reactive pools. After pool resolution, 8 HEV RNA-positive donations were identified by the in-house detection method, whereas 17 HEV RNA-positive donations were identified by ID-NAT with the cobas HEV assay. This resulted in an incidence of 1:1268 donations (0.079%) for MP-NAT screening and 1:597 donations (0.168%) for ID-NAT screening. CONCLUSIONS: The detection frequency of HEV RNA was approximately 50% higher if ID-NAT was used compared to MP-NAT. However, viral loads of ID-NAT-only samples were below 25 IU/mL and will often not result in transfusion-transmitted HEV (TT-HEV) infection, taking into account the currently known infectious dose of 5.0E + 04 IU inevitably resulting in TT-HEV infection. The clinical relevance and need for identification of these low-level HEV-positive donors still require further investigation.

Subtype-specific differences in the risk of hospitalisation among patients infected with hepatitis E virus genotype 3 in Belgium, 2010-2018.

Some European countries recently reported an increase in hepatitis E virus genotype 3 (HEV-3) of the subtype 3c. No link between HEV-3 subtypes and severity is established to date. Here, we report that patients infected with HEV-3c were at lower risk of hospitalisation, compared to those infected with HEV-3f, the other main subtype circulating in Belgium.

Association of Toll-like receptor 4 polymorphism with hepatitis E virus-infected Indian patients.

Hepatitis E infection caused by hepatitis E virus (HEV), a major public health concern in developing countries, is responsible for sporadic and epidemic acute viral hepatitis in adults. Pathogenesis of hepatitis E infection is poorly understood. Toll-like receptors (TLRs) are the key players of innate immunity recognize pathogen-associated molecular patterns (PAMPs). Previously, we found higher TLR4 expression (at protein and gene level) with impaired cytokine response upon stimulus of PBMCs with LPS in HEV-infected patients. In view of the earlier observations of the association of polymorphisms in TLR4 genes (A299G, C399T) with liver diseases, we investigated TLR4 polymorphisms in HEV-infected patients. We observed the significant association of TLR4-399CC and CT alleles with hepatitis E (both subclinical and acute patients). Carrier frequency of TLR4-399 CT was lower in patients' categories in comparison with the controls. Higher frequency of allele TLR4-399C significantly correlated with disease progression. Acute hepatitis E patients showed the higher frequency of CG and TA haplotypes, while the rare haplotype (TG) was more frequent in controls. The other single nucleotide polymorphism (SNP) at TLR4-299 (A>G) did not show any difference. We report here for the first time the association of TLR4 polymorphism with hepatitis E and suggest that TLR 4 hyporesponsiveness during HEV infection might be related to its polymorphism.

RIG-I is a key antiviral interferon-stimulated gene against hepatitis E virus regardless of interferon production.

Interferons (IFNs) are broad antiviral cytokines that exert their function by inducing the transcription of hundreds of IFN-stimulated genes (ISGs). However, little is known about the antiviral potential of these cellular effectors on hepatitis E virus (HEV) infection, the leading cause of acute hepatitis globally. In this study, we profiled the antiviral potential of a panel of important human ISGs on HEV replication in cell culture models by overexpression of an individual ISG. The mechanism of action of the key anti-HEV ISG was further studied. We identified retinoic acid-inducible gene I (RIG-I), melanoma differentiation-associated protein 5, and IFN regulatory factor 1 (IRF1) as the key anti-HEV ISGs. We found that basal expression of RIG-I restricts HEV infection. Pharmacological activation of the RIG-I pathway by its natural ligand 5'-triphosphate RNA potently inhibits HEV replication. Overexpression of RIG-I activates the transcription of a wide range of ISGs. RIG-I also mediates but does not overlap with IFN-α-initiated ISG transcription. Although it is classically recognized that RIG-I exerts antiviral activity through the induction of IFN production by IRF3 and IRF7, we reveal an IFN-independent antiviral mechanism of RIG-I in combating HEV infection. We found that activation of RIG-I stimulates an antiviral response independent of IRF3 and IRF7 and regardless of IFN production. However, it is partially through activation of the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) cascade of IFN signaling. RIG-I activated two distinct categories of ISGs, one JAK-STAT-dependent and the other JAK-STAT-independent, which coordinately contribute to the anti-HEV activity. CONCLUSION: We identified RIG-I as an important anti-HEV ISG that can be pharmacologically activated; activation of RIG-I stimulates the cellular innate immunity against HEV regardless of IFN production but partially through the JAK-STAT cascade of IFN signaling. (Hepatology 2017;65:1823-1839).

Evaluation of candidate genes associated with hepatitis A and E virus infection in Chinese Han population.

BACKGROUND: Recent GWAS-associated studies reported that single nucleotide polymorphisms (SNPs) in ABCB1, TGFß1, XRCC1 genes were associated with hepatitis A virus (HAV) infection, and variants of APOA4 and APOE genes were associated with and hepatitis E virus (HEV) infection in US population. However, the associations of these loci with HAV or HEV infection in Chinese Han population remain unclear. METHODS: A total of 3082 Chinese Han persons were included in this study. Anti-HAV IgG and anti-HEV IgG were detected by enzyme-linked immunosorbent assay (ELISA). Genotypes in ABCB1, TGFß1, XRCC1, APOA4 and APOE SNPs were determined by TaqMan MGB technology. RESULTS: In Chinese Han population, rs1045642 C to T variation in ABCB1 was significantly associated with the decreased risk of HAV infection (P < 0.05). However, the effect direction was different with the previous US study. Rs1001581 A to G variation in XRCC1, which was not identified in US population, was significantly associated with the protection against HAV infection in our samples (P < 0.05). In addition, our results suggested that rs7412 C to T variation in APOE was significantly associated with lower risk of HEV infection in males (adjusted OR < 1.0, P < 0.05) but not in females. CONCLUSIONS: ABCB1 and XRCC1 genes variants are significantly associated with the protection against HAV infection. Additionally, Chinese Han males with rs7412 C to T variation in APOE gene are less prone to be infected by HEV.

A mutation in the progesterone receptor predisposes to HEV infection in HIV-positive patients.

BACKGROUND AND AIMS: Infection with Hepatitis E virus (HEV) can cause chronic liver disease in immunocompromised hosts. In transplant recipients, the use of certain immunosuppressants and food habits has been proposed as risk factors for HEV. In individuals infected with the human immunodeficiency virus (HIV), risk factors for HEV infection are less clear. We aimed to study the association between a mutation in the progesterone receptor (PR) named PROGINS and HEV-infected in HIV-positive individuals. METHODS: We evaluated the presence of the SNP PROGINS via KASP in serum samples of 64 HIV-positive individuals and 187 healthy controls. We performed ELISA tests to address the serum levels of IL-10 and IL-12, as well as T-cell stimulation assays in peripheral blood to address immune response in individuals with PROGINS. RESULTS: We found a significant association between the presence of PROGINS mutation and HEV seroprevalence in individuals infected with HIV (30% in HIV+/HEV+ versus 2% in HIV+/HEV, respectively, P = .009). Moreover, we found that HIV+/HEV+ individuals expressing the PROGINS mutation had lower serum levels of IL-10 and higher levels of IL-12. The presence of the mutation led to a reduced response upon stimulation of CD4+ and CD8+ T cells compared to those without the mutation, suggesting an immune modulation associated with PROGINS. CONCLUSIONS: Our study identified a mutation in the PR that provides significant insights into mechanisms of HEV infection in immunosuppressed individuals.

The incubation period of hepatitis E genotype 1: insights from pooled analyses of travellers.

Hepatitis E virus genotype 1 (HEV G1) is an important cause of morbidity and mortality in Africa and Asia. HEV G1's natural history, including the incubation period, remains poorly understood, hindering surveillance efforts and effective control. Using individual-level data from 85 travel-related HEV G1 cases in England and Wales, we estimate the incubation period distribution using survival analysis methods, which allow for appropriate inference when only time ranges, rather than exact times are known for the exposure to HEV and symptom onset. We estimated a 29.8-day (95% confidence interval (CI) 24.1-36.0) median incubation period with 5% of people expected to develop symptoms within 14.3 days (95% CI 10.1-21.7) and 95% within 61.9 days (95% CI 47.4-74.4) of exposure. These estimates can help refine clinical case definitions and inform the design of disease burden and intervention studies.