Adeno-associated virus 2 infection in children with non-A-E hepatitis

Current and Emerging Issues in Adeno-Associated Virus Vector-Mediated Liver-Directed Gene Therapy

Adeno-associated virus (AAV) vectors have demonstrated safety and efficacy for gene transfer to hepatocytes in preclinical models, in various clinical trials and from a clinical experience with a growing number of approved gene therapy products. Although the exact duration is unknown, the expression of therapeutic genes in hepatocytes remains stable for several years after a single administration of the vector at clinically relevant doses in adult patients with hemophilia and other inherited metabolic disorders. However, clinical applications, especially for diseases requiring high AAV vector doses by intravenous administrations, have raised several concerns. These include the high prevalence of pre-existing immunity against the vector capsid, activation of the complement and the innate immunity with serious life-threatening complications, elevation of liver transaminases, liver growth associated with loss of transgene expression, underlying conditions negatively affecting AAV vector safety and efficacy. Despite these issues, the field is rapidly advancing with a better understanding of vector-host interactions and the development of new strategies to improve liver-directed gene therapy. This review provides an overview of the current and emerging challenges for AAV-mediated liver-directed gene therapy.

Genetic Variants of GBP4: Reduced Risks for Drug-Induced Acute Liver Failure in Non-Finnish European Population

BACKGROUND AND AIMS

Acute liver failure (ALF) is a serious condition, typically in individuals without prior liver disease. Drug-induced ALF (DIALF) constitutes a major portion of ALF cases. Our research aimed to identify potential genetic predispositions to DIALF.

METHODS

We analysed the potential genetic variants associated with DIALF using the whole exome sequencing data from 75 cases, including 40 non-Finnish European cases in the pilot study. Chi-square tests were performed for case-control analysis against the 1000 genomes project as the control. A replication study of 44 DIALF cases that included 24 non-Finnish Europeans was conducted to validate candidate variants. The association between clinical phenotype and genotypes was analysed using one-way analysis of variance.

RESULTS

Eight variants (rs561037, rs561042, rs608339, rs655260, rs1142886, rs1142888, rs1142889 and rs1142890) in the guanylate binding protein 4 (GBP4) were significantly associated with DIALF in non-Finnish Europeans in the pilot study and confirmed in the replication study. Rs561037 and rs561042 were highly significant with the lowest allele frequencies in both pilot and replication studies. An association was also found between these variants and milder clinical outcomes, indicated by lower peak levels of ALT, AST and higher Karnofsky performance scores.

CONCLUSION

Our study identified eight GBP4 missense variants linked to a lower risk of DIALF in the non-Finnish European population. The GBP4 protein, activated by interferon-gamma, plays a critical role in innate immunity. These findings suggest that GBP4 variants might influence immune and inflammatory responses in DIALF, though further studies are needed to elucidate the underlying mechanisms.

A Metagenomic Survey of Virological Hazards in Market-Ready Oysters

Viral contamination of bivalve molluscs, such as oysters, is a well-recognized food safety risk. The aim of this study was to assess virological hazards in market-ready oysters on the Dutch market. Non-targeted metagenome analysis was first performed on norovirus spiked-in samples showing linear and sensitive detection of norovirus GI.2 and GII.4 down to 14 and 5 genome copies per reaction, respectively. Subsequently, metagenomic measurements were performed to detect vertebrate viral genomes present in 24 undepurated B-area samples and 144 market-ready oyster samples taken in November up to and including February of the years 2015-2021. Genome sequences from fifteen viral species were identified in market-ready oysters which are associated with infections in humans and were detected above the genomic coverage threshold (5%) applied. Among these, the two genera from the Caliciviridae family, norovirus and sapovirus were detected at high prevalence (44 and 30%). Additionally, adeno-associated dependoparvovirus A and B as well as Aichi virus A and B (ribo)nucleic acids were detected (42, 33, 6, and 11%). Nucleic acids from virus species in oysters included potentially hazardous Picobirnavirus, Anellovirus, and multiple Circoviridae and Genomoviridae species. By integrating metagenome analysis into the monitoring process, researchers, food producers and regulatory bodies can gain valuable insights into the viral communities present in the food chain. This allows for the detection of potential pathogenic hazards at an early stage, providing an opportunity for tailored monitoring programs and targeted interventions to maintain the sanitary quality of the production area and safeguard public health.

Association between adeno-associated virus 2 and severe acute hepatitis of unknown etiology in Japanese children

INTRODUCTION

Outbreaks of acute hepatitis of unknown etiology (AHUE) in children were reported in Western countries in 2022. Previous studies found that adeno-associated virus 2 (AAV2) and its helper viruses, such as human adenovirus (HAdV) and human herpesvirus-6 (HHV-6), are frequently detected in patients with AHUE. However, the existence of hepatitis associated with AAV2 prior to AHUE outbreaks in 2022 had not yet been investigated. We aimed to investigate the association between AAV2 and pediatric acute hepatitis in Japanese children, as well as the incidence of AAV2-related hepatitis prior to 2022.

METHODS

Preserved blood samples obtained from 49 pediatric patients with acute hepatitis between 2017 and 2023 were retrospectively analyzed. Blood samples from 50 children with acute illnesses and 50 children with chronic conditions were used as controls. Viral DNA loads were quantitated using real-time PCR.

RESULTS

AAV2 DNA was detected in 12 % (6/49) of acute hepatitis cases but in only one acute illness and none of the chronic-condition control cases. The concentration of AAV2 DNA in the six acute hepatitis cases was higher than that in the acute-illness control case. Co-infection with one or more helper viruses, including HAdV, HHV-6, cytomegalovirus, and Epstein-Barr virus, was observed in five AAV2-positive cases.

CONCLUSIONS

Our results indicated the sporadic occurrence of pediatric severe hepatitis associated with AAV2 infection in Japan prior to the AHUE outbreaks in 2022. Our findings suggest that co-infection with AAV2 and helper viruses plays a role in developing severe hepatitis.

Using Laboratory Test Results for Surveillance During a New Outbreak of Acute Hepatitis in 3-Week- to 5-Year-Old Children in the United Kingdom, the Netherlands, Ireland, and Curaçao: Observational Cohort Study

Background

In March 2022, a concerning rise in cases of unexplained pediatric hepatitis was reported in multiple countries. Cases were defined as acute hepatitis with serum transaminases >500 U/L (aspartate transaminase [AST] or alanine transaminase [ALT]) in children aged 16 years or younger. We explored a simple federated data analytics method to search for evidence of unreported cases using routinely held data. We conducted a pragmatic survey to analyze changes in the proportion of hospitalized children with elevated AST or ALT over time. In addition, we studied the feasibility of using routinely collected clinical laboratory results to detect or follow-up the outbreak of an infectious disease.

Objective

We explored a simple federated data analytics method to search for evidence of unreported cases using routinely held data.

Methods

We provided hospitals with a simple computational tool to enable laboratories to share nondisclosive summary-level data. Summary statistics for AST and ALT measurements were collected from the last 10 years across all age groups. Measurements were considered elevated if ALT or AST was >200 U/L. The rate of elevated AST or ALT test for 3-week- to 5-year-olds was compared between a period of interest in which cases of hepatitis were reported (December 1, 2021, to August 31, 2022) and a prepandemic baseline period (January 1, 2012, to December 31, 2019). We calculated a z score, which measures the extent to which the rate for elevated ALT or AST was higher or lower in the period of interest compared to a baseline period, for the 3-week- to 5-year-olds.

Results

Our approach of sharing a simple software tool for local use enabled rapid, federated data analysis. A total of 34 hospitals in the United Kingdom, the Netherlands, Ireland, and Curaçao were asked to contribute summary data, and 30 (88%) submitted their data. For all locations combined, the rate of elevated AST or ALT measurements in the period of interest was not elevated (z score=-0.46; P=.64). Results from individual regions were discordant, with a higher rate of elevated AST or ALT values in the Netherlands (z score=4.48; P<.001), driven by results from a single center in Utrecht. We did not observe any clear indication of changes in primary care activity or test results in the same period.

Conclusions

Hospital laboratories collect large amounts of data on a daily basis that can potentially be of use for disease surveillance, but these are currently not optimally used. Federated analytics using nondisclosive, summary-level laboratory data sharing was successful, safe, and efficient. The approach holds potential as a tool for pandemic surveillance in future outbreaks. Our findings do not indicate the presence of a broader outbreak of mild hepatitis cases among young children, although there was an increase in elevated AST or ALT values locally in the Netherlands.

Co-occurrence of adeno-associated virus 2 and human enteric adenovirus (group F) in wastewater after worldwide outbreaks of acute hepatitis of unknown etiology (AHUE)

In 2022, several cases of acute hepatitis of unknown etiology (AHUE) have been associated with Adeno-associated virus 2 (AAV-2) and the common childhood virus Adenovirus 41 (AdV-41). This outbreak has resulted in serious complications in patients which included 5 % of individuals requiring a liver transplant and 22 deaths. Before these AHUE cases, no previous information had been reported regarding the co-infections and co-occurrence of these two viruses in the human population. The present study utilized WBE tools to investigate the prevalence of AAV-2 and AdV-F (AdV-41 and AdV-40) in wastewater from two different waste-water treatment plants (WWTP) serving the city of Bloomington in Southern Indiana, USA. The concentrations of AAV-2 and AdV-F were quantified using digital PCR in weekly wastewater samples taken over the duration of 18 months. High levels of both viruses were observed in most of the samples where co-detection and correlation in the concentrations for AAV-2 and AdV-F were found to be significant (p < 0.01) throughout duration of the study. In addition, significant seasonal changes were observed in the viral concentrations of both viruses (P < 0.01), but these seasonal variations were different between WWTPs (p < 0.01). However, these seasonal variations in viral concentrations were similar for both viruses. The sequences of AdV-F and AAV were obtained from the wastewater samples and confirmed the detection of AAV-2, AdV-41, and AdV-40 in the samples analyzed. Even though our study was done after the 2022 outbreak of AHUE, our results demonstrated the persistence of infections with both viruses in the population. It also highlights the ongoing spread of both viruses in the population and the importance of WBE in surveillance of these viruses.

Acute hepatitis of unknown aetiology in children: evidence for and against causal relationships with SARS-CoV-2, HAdv and AAV2

BACKGROUND

The cause of acute paediatric hepatitis of unknown aetiology (2022) has not been established despite extensive investigation.

OBJECTIVE

To summarise the evidence for and against a causal role for human adenovirus (HAdv), adeno-associated virus 2 (AAV-2) and SARS-CoV-2 in outbreaks of paediatric hepatitis in 2022.

METHODS

We appraised and summarised relevant evidence for each of the Bradford Hill criteria for causality using quantitative (statistical modelling) and qualitative (narrative coherence) approaches. Each team member scored the evidence base for each criterion separately for HAdv, AAV-2 and SARS-CoV-2; differences were resolved by discussion. We additionally examined criteria of strength and temporality by examining the lagged association between SARS-CoV-2 positivity, respiratory HAdv positivity, positive faecal HAdv specimens and excess A&E attendances in 1-4 years for liver conditions in England.

RESULTS

Assessing criteria using the published literature and our modelling: for HAdv three Bradford Hill criteria (strength, consistency and temporality) were partially met; and five criteria (consistency, coherence, experimental manipulation, analogy and temporality) were minimally met. For AAV-2, the strength of association criterion was fully met, five criteria (consistency, temporality, specificity, biological gradient and plausibility) were partially met and three (coherence, analogy and experimental manipulation) were minimally met. For SARS-CoV-2, five criteria (strength of association, plausibility, temporality, coherence and analogy) were fully met; one (consistency) was partially met and three (specificity, biological gradient and experimental manipulation) were minimally met.

CONCLUSION

Based on the Bradford Hill criteria and modelling, HAdv alone is unlikely to be the cause of the recent increase in hepatitis in children. The causal link between SARS-CoV-2, and to a lesser degree AAV-2, appears substantially stronger but remains unproven. Hepatitis is a known complication of multisystem inflammatory syndrome in children following COVID-19, and SARS-CoV-2 has been linked to increased susceptibility to infection post-COVID-19, which may suggest complex causal pathways including a possible interaction with AAV-2 infection/reactivation in hosts that are genetically susceptible or sensitised to infection.

The clinical characteristics and SARS-CoV-2 infection in children of acute hepatitis with unknown aetiology: A meta-analysis and systematic review

The World Health Organization has issued a global alert on Acute Severe Hepatitis of Unknown Aetiology (AS-HEP-UA) since 23 April 2022,and there was still uncertainty regarding the association of AS-HEP-UA with SARS-CoV-2 as well as adenovirus. This study aimed to summarize the infection of SARS-CoV-2 and co-infections with adenovirus, as well as clinical features and outcomes in patients with AS-HEP-UA. PubMed, Embase, Web of Science, and the Cochrane Library were searched from 1 October 2021 to 8 December 2022 for studies about patients with AS-HEP-UA. This study was registered in the PROSPERO database (CRD42023385056). We has included 14 eligible articles. The main clinical features of AS-HEP-UA were jaundice (65%) and vomiting (59%), while other clinical features included diarrhea (45%), abdominal pain (37%), and fever (31%), roughly 10% of the children required liver transplantation. The overall positivity rate for SARS-CoV-2 was 21.6% (95% CI: 0.126-0.319), with 25.5% (95% CI: 0.161-0.358) for previous infections. The positivity rate for adenovirus infection was 58.6% (95% CI:0.429-0.736) while co-infection with SARS-CoV-2 was 17.5% (95% CI: 0.049-0.342). Moreover, we found that the positive rate of SARS-CoV-2 for this hepatitis outbreak was correlated with region by subgroup analysis. In conclusion, the positive rate of adenovirus was higher than SARS-CoV-2, and the relationship between AS-Hep-UA and COVID-19 is not significant. However, it cannot be excluded that the COVID-19 epidemic is an indirect causative agent of AS-Hep-UA, which requires a larger cohort of AS-Hep-UA patients to uncover additional findings.

Recombinant adeno-associated virus as a delivery platform for ocular gene therapy: A comprehensive review

Adeno-associated virus (AAV) has emerged as a leading platform for in vivo gene therapy, particularly in ocular diseases. AAV-based therapies are characterized by low pathogenicity and broad tissue tropism and have demonstrated clinical success, as exemplified by voretigene neparvovec-rzyl (Luxturna) being the first gene therapy to be approved by the U.S. Food and Drug Administration to treat RPE65-associated Leber congenital amaurosis (LCA). However, several challenges remain in the development of AAV-based gene therapies, including immune responses, limited cargo capacity, and the need for enhanced transduction efficiency, especially for intravitreal delivery to photoreceptors and retinal pigment epithelium cells. This review explores the biology of AAVs in the context of gene therapy, innovations in capsid engineering, and clinical advancements in AAV-based ocular gene therapy. We highlight ongoing clinical trials targeting inherited retinal diseases and acquired conditions, discuss immune-related limitations, and examine novel strategies for enhancing AAV vector performance to address current barriers.

Causal inference can lead us to modifiable mechanisms and informative archetypes in sepsis

Medical progress is reflected in the advance from broad clinical syndromes to mechanistically coherent diagnoses. By this metric, research in sepsis is far behind other areas of medicine-the word itself conflates multiple different disease mechanisms, whilst excluding noninfectious syndromes (e.g., trauma, pancreatitis) with similar pathogenesis. New technologies, both for deep phenotyping and data analysis, offer the capability to define biological states with extreme depth. Progress is limited by a fundamental problem: observed groupings of patients lacking shared causal mechanisms are very poor predictors of response to treatment. Here, we discuss concrete steps to identify groups of patients reflecting archetypes of disease with shared underlying mechanisms of pathogenesis. Recent evidence demonstrates the role of causal inference from host genetics and randomised clinical trials to inform stratification analyses. Genetic studies can directly illuminate drug targets, but in addition they create a reservoir of statistical power that can be divided many times among potential patient subgroups to test for mechanistic coherence, accelerating discovery of modifiable mechanisms for testing in trials. Novel approaches, such as subgroup identification in-flight in clinical trials, will improve efficiency. Within the next decade, we expect ongoing large-scale collaborative projects to discover and test therapeutically relevant sepsis archetypes.

Non-hepatotropic viral hepatitis: a narrative review

Non-hepatotropic viral hepatitis (NHVH) refers to acute hepatitis or acute liver failure caused by viruses that do not primarily target the liver. These viruses include the Epstein-Barr virus (EBV), cytomegalovirus (CMV), herpes simplex virus (HSV)-1 and -2, varicella zoster, parvovirus, adenovirus, adeno-associated virus type 2, measles, and severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2). The epidemiology, pathogenesis, and clinical manifestations of hepatitis due to hepatotropic viruses (hepatitis A-E) have been well studied. However, there is a paucity of data on NHVH due to its rarity, self-limiting clinical course, and vague presentation. NHVH can occur as an isolated illness or as part of a disseminated disease, and its clinical features range from self-limiting transaminitis to acute liver failure. This activity reviews the most common non-hepatotropic viruses (NHV), with a focus on their biology, etiopathogenesis, clinical manifestations, and management.

Human Circovirus in Patients with Hepatitis, Hong Kong

Circovirus human is a new viral species that includes the human circovirus (HCirV), which has been linked to hepatitis in immunocompromised persons. We investigated prevalence of HCirV infection in 278 patients with hepatitis and 184 asymptomatic persons using real-time PCR and sequencing assays. HCirV viremia and sequences were found in 8 (2.9%) hepatitis patients and no asymptomatic patients. Alternate causes of hepatitis (hepatitis E and cholangitis) were clearly identifiable in 2 HCirV-infected patients. HCirV could not be ruled out as a contributor to hepatitis in the remaining 6 patients, 4 of whom were immunocompromised. Persistent infections were documented in 3 patients, but only 1 had relapsing hepatitis. One HCirV patient displayed symptoms of an infectious mononucleosis-like syndrome. Isolates clustered with known HCirV strains from France and China. HCirV-derived virus-like particles bound to PLC/PRF/5 and Hep-G2 human hepatoma cells but not to lung epithelial cells, indicating hepatic tropism.

The pattern of childhood infections during and after the COVID-19 pandemic

The rates of most paediatric infectious diseases declined during the initial phase of the COVID-19 pandemic due to the implementation of non-pharmaceutical interventions. However, after the gradual release of these interventions, resurgences of infections occurred with notable variations in incidence, clinical manifestations, pathogen strains, and age distribution. This Review seeks to explore these changes and the rare clinical manifestations that were made evident during the resurgence of known childhood infections. The magnitude of resurgences was possibly caused by a profound population immunity debt to specific pathogens in combination with the coinciding reappearance of viral and bacterial infections, rather than novel pathogen variants, increased antimicrobial resistance, or altered childhood immune function. As the usual patterns of paediatric infectious diseases were disrupted during the COVID-19 pandemic, the consequences of a population immunity debt were unravelled, and new insights into pathogen transmissibility, disease pathogenesis, and rare clinical manifestations were revealed.

Adenovirus 41 diversity in Arizona (USA) using wastewater-based epidemiology, long-range PCR, and pathogen sequencing between October 2019 and March 2020

By coupling long-range polymerase chain reaction, wastewater-based epidemiology, and pathogen sequencing, we show that adenovirus type 41 hexon-sequence lineages, described in children with hepatitis of unknown origin in the United States in 2021, were already circulating within the country in 2019. We also observed other lineages in the wastewater, whose complete genomes have yet to be documented from clinical samples.

Adeno-associated viral vector integration: implications for long-term efficacy and safety

Adeno-associated virus (AAV) vector gene therapy provides a promising platform for treatment of monogenic inherited disorders. Clinical studies have demonstrated long-term expression with reduction in bleeding using this approach for the treatment of hemophilia. Despite these advances, there are unknowns surrounding the natural history of recombinant AAV (rAAV) vectors and the cellular mechanisms mediating vector persistence. These unknowns underpin questions regarding long-term efficacy and safety. The predominant mechanism via which AAV is proposed to persist is in circular double-stranded extrachromosomal DNA structures (episomes) within the nucleus. Studies of wild-type AAV (WT-AAV) and rAAV have demonstrated that AAV also persists via integration into a host cell's DNA. It is important to determine whether these integration events can mediate expression or could result in any long-term safety concerns. WT-AAV infection affects a large proportion of the general population, which is thought to have no long-term sequelae. Recent studies have highlighted that this WT-AAV has been detected in cases of acute hepatitis in children and in a minority of cases of hepatocellular carcinoma. Integration following treatment using rAAV has also been reported in preclinical and clinical studies. There have been variable reports on the potential implications of integration for rAAV vectors, with data in some murine studies demonstrating recurrent integration with development of hepatocellular carcinoma. These findings have not been seen in other preclinical or clinical studies. In this review, we will summarize current understanding of the natural history of AAV (wild-type and recombinant) with a focus on genomic integration and cellular implications.

Prevalence of Antibodies against Adeno-Associated Viruses (AAVs) in Göttingen Minipigs and Its Implications for Gene Therapy and Xenotransplantation

Adeno-associated viruses (AAV) are widely used as delivery vectors in clinical trials for in vivo gene therapy due to their unique features. Göttingen minipigs are a well-established animal model for several diseases and can be used for the efficacy and safety testing of AAV-based gene therapy. Pre-existing antibodies against AAV may influence the results of testing and, therefore, the animals should be tested for the presence of antibodies against relevant AAV serotypes. The detection of AAVs in pigs may be also important for the virus safety of xenotransplantation. In this study, we screened Göttingen minipigs from Ellegaard Göttingen Minipigs A/S, Denmark, and Marshall BioResources, USA, for antibodies against AAV1, AAV2, AAV6, AAV9 serotypes. Of the 20 animals tested, 18 had no neutralizing antibodies for all AAVs tested, none had antibodies against AAV9, only one had antibodies against AAV6, and the titers of antibodies against AAV1 and AAV2 were less than 1:100, with two exceptions. For total binding IgG, more individuals showed positivity for all the tested serotypes but, in general, the levels were low or zero. Three animals had no antibodies at all against the AAVs tested. Therefore, Göttingen minipigs could be considered an attractive animal model for gene therapy studies. Since some animals were negative for all AAVs tested, these may be selected and used as donor animals for xenotransplantation.

Optimizing liver health before and after gene therapy for hemophilia A

ABSTRACT

Gene therapy for severe hemophilia A uses an adeno-associated virus (AAV) vector and liver-specific promoters that depend on healthy hepatocyte function to achieve safe and long-lasting increases in factor VIII (FVIII) activity. Thus, hepatocyte health is an essential aspect of safe and successful gene therapy. Many people living with hemophilia A have current or past chronic hepatitis C virus infection, metabolic dysfunction-associated steatosis or steatohepatitis, or other conditions that may compromise the efficacy and safety of AAV-mediated gene therapy. In addition, gene therapy may induce an immune response to transduced hepatocytes, leading to liver inflammation and reduced FVIII activity. The immune response can be treated with immunosuppression, but close monitoring of liver function tests and factor levels is necessary. The long-term risk of hepatocellular carcinoma associated with gene therapy is unknown. Routine screening by imaging for hepatocellular carcinoma, preferable every 6 months, is essential in patients at high risk and recommended in all recipients of hemophilia A gene therapy. This paper describes our current understanding of the biologic underpinnings of how liver health affects hemophilia A gene therapy, and provides practical clinical guidance for assessing, monitoring, and managing liver health both before and after gene therapy.

A systematic review of immunosuppressive protocols used in AAV gene therapy for monogenic disorders

The emergence of adeno-associated virus (AAV)-based gene therapy has brought hope to patients with severe monogenic disorders. However, immune responses to AAV vectors and transgene products present challenges that require effective immunosuppressive strategies. This systematic review focuses on the immunosuppressive protocols used in 38 clinical trials and 35 real-world studies, considering a range of monogenic diseases, AAV serotypes, and administration routes. The review underscores the need for a deeper understanding of immunosuppressive regimens to enhance the safety and effectiveness of AAV-based gene therapy. Characterizing the immunological responses associated with various gene therapy treatments is crucial for optimizing treatment protocols and ensuring the safety and efficacy of forthcoming gene therapy interventions. Further research and understanding of the impact of immunosuppression on disease, therapy, and route of administration will contribute to the development of more effective and safer gene therapy approaches in the future.

Acute Hepatitis in Children Due to Rat Hepatitis E Virus

Two of 11 children with acute hepatitis of unknown origin were found to have rat hepatitis E virus infection. This infection should be considered in the differential diagnosis of children with acute hepatitis of unknown origin.

Increased incidence of seronegative autoimmune hepatitis in children during SARS-CoV-2 pandemia period

Background

Seronegative autoimmune hepatitis in children is a rare but potentially severe disease, sometimes requiring liver transplantation. This type of hepatitis may be associated with various immunological and hematological disorders, ranging from isolated lymphopenia to aplastic anemia. Precise pathophysiological mechanisms are still unknown, but the role of viruses cannot be excluded, either as directly pathogenic or as triggers, responsible for an inappropriate immune stimulation. Having the impression of an increasing number of seronegative autoimmune hepatitis since the beginning of SARS-CoV-2 pandemia period, we hypothesized that SARS-CoV-2 virus could be an infectious trigger.

Methods

We conducted a retrospective, observational, descriptive study about children with seronegative autoimmune hepatitis, in a tertiary care center, between 2010 and 2022.

Results

Thirty-two patients were included. The overall incidence of seronegative autoimmune hepatitis increased 3.3-fold in 2020-2022, during the SARS-CoV-2 pandemia period (16 patients in 2.8 years) compared with 2010-2019 the pre pandemia period (16 patients in 9 years). Patients' clinical and biochemical liver characteristics did not differ between the two periods. Hematological damages were less severe during the pandemia period. Immunological studies revealed a dysregulated immune response. The initiation of immunosuppressive therapy (corticosteroids ± cyclosporine) was earlier during the pandemia period than before.

Conclusion

In cases of undetermined acute hepatitis, an immune-mediated origin should be considered, prompting a liver biopsy. If the histological aspect points to an immune origin, immunosuppressive treatment should be instituted even though autoimmune hepatitis antibodies are negative. Close hematological monitoring must be performed in all cases. The 3.3-fold increase of cases during the SARS-CoV-2 pandemia will need to be further analyzed to better understand the underlying immunological mechanisms, and to prove its potential involvement.

Adeno-associated viral vector gene therapy: Challenges for the paediatric hepatologist

Hepatoxicity associated with recombinant adeno-associated virus gene therapy is being increasingly encountered by hepatologists in tertiary and quaternary referral units due to the recent increase of these therapies for neuromuscular and haematological disorders. The challenges in managing the condition stem from a lack of good-quality evidence on the appropriate protocols for immunosuppressants due to lack of representative animal models. There is a need for protocols for diagnosing and treating hepatotoxicity and this possible with further research to understand the problem and its management. The review also highlights the importance of a multidisciplinary team in managing hepatotoxicity and recommends further research to better identify at-risk individuals, define the extent of the problem and assess the long-term effects of liver injury and immunosuppressants.

Clinical and Histopathologic Characteristics of Acute Severe Hepatitis Associated With Human Herpesvirus 6 Infection

Acute severe hepatitis associated with active human herpesvirus 6 (HHV-6) infection is a rare life-threatening condition with unclear clinical course and histopathology. In this study, we retrospectively analyzed 5 patients with indeterminate acute severe hepatitis found to have active hepatic HHV-6 infection during care. All patients were previously healthy children presenting with a nonspecific prodrome. Four developed acute liver failure (ALF) and 3 received liver transplantation. The explanted livers and biopsies demonstrated a centrilobular pattern of necroinflammation characterized by moderate to marked central perivenulitis and confluent centrilobular to panlobular necrosis in 4 cases, accompanied by marked hepatocellular swelling and milder portal inflammation in 3. Central perivenulitis was more prominent in comparison to a control of group of ALF without HHV-6 ( P =0.01). When compared with the children with acute severe hepatitis associated with adenovirus encountered in the recent outbreak, both central perivenulitis and centrilobular necrosis were significant predictors for association with HHV-6 ( P <0.01). Liver immunohistochemistry detected HHV-6 structural protein in biliary epithelium in all cases and a predominance of CD8 + T cells in the perivenular inflammatory infiltrate. Among the 4 patients with ALF, one received early anti-HHV-6 therapy and had transplant-free survival, while the other 3 received either general prophylactic antiviral treatment only (n=2) or late anti-HHV-6 therapy (n=1) and needed liver transplantation. Our findings were similar to those in previously reported cases. In summary, acute severe hepatitis associated with HHV-6 tends to affect children, progress to ALF, and exhibit characteristic centrilobular necroinflammation which likely represents an immune-mediated process.

Optimising Clinical Epidemiology in Disease Outbreaks: Analysis of ISARIC-WHO COVID-19 Case Report Form Utilisation

Standardised forms for capturing clinical data promote consistency in data collection and analysis across research sites, enabling faster, higher-quality evidence generation. ISARIC and the World Health Organization have developed case report forms (CRFs) for the clinical characterisation of several infectious disease outbreaks. To improve the design and quality of future forms, we analysed the inclusion and completion rates of the 243 fields on the ISARIC-WHO COVID-19 CRF. Data from 42 diverse collaborations, covering 1886 hospitals and 950,064 patients, were analysed. A mean of 129.6 fields (53%) were included in the adapted CRFs implemented across the sites. Consistent patterns of field inclusion and completion aligned with globally recognised research priorities in outbreaks of novel infectious diseases. Outcome status was the most highly included (95.2%) and completed (89.8%) field, followed by admission demographics (79.1% and 91.6%), comorbidities (77.9% and 79.0%), signs and symptoms (68.9% and 78.4%), and vitals (70.3% and 69.1%). Mean field completion was higher in severe patients (70.2%) than in all patients (61.6%). The results reveal how clinical characterisation CRFs can be streamlined to reduce data collection time, including the modularisation of CRFs, to offer a choice of data volume collection and the separation of critical care interventions. This data-driven approach to designing CRFs enhances the efficiency of data collection to inform patient care and public health response.

Therapeutic Application and Structural Features of Adeno-Associated Virus Vector

Adeno-associated virus (AAV) is characterized by non-pathogenicity, long-term infection, and broad tropism and is actively developed as a vector virus for gene therapy products. AAV is classified into more than 100 serotypes based on differences in the amino acid sequence of the capsid protein. Endocytosis involves the uptake of viral particles by AAV and accessory receptors during AAV infection. After entry into the cell, they are transported to the nucleus through the nuclear pore complex. AAVs mainly use proteoglycans as receptors to enter cells, but the types of sugar chains in proteoglycans that have binding ability are different. Therefore, it is necessary to properly evaluate the primary structure of receptor proteins, such as amino acid sequences and post-translational modifications, including glycosylation, and the higher-order structure of proteins, such as the folding of the entire capsid structure and the three-dimensional (3D) structure of functional domains, to ensure the efficacy and safety of biopharmaceuticals. To further enhance safety, it is necessary to further improve the efficiency of gene transfer into target cells, reduce the amount of vector administered, and prevent infection of non-target cells.

Retrospective analysis of hospital electronic health records reveals unseen cases of acute hepatitis with unknown aetiology in adults in Oxfordshire

BACKGROUND

An outbreak of acute severe hepatitis of unknown aetiology (AS-Hep-UA) in children during 2022 was subsequently linked to infections with adenovirus-associated virus 2 and other 'helper viruses', including human adenovirus. It is possible that evidence of such an outbreak could be identified at a population level based on routine data captured by electronic health records (EHR).

METHODS

We used anonymised EHR to collate retrospective data for all emergency presentations to Oxford University Hospitals NHS Foundation Trust in the UK, between 2016-2022, for all ages from 18 months and older. We investigated clinical characteristics and temporal distribution of presentations of acute hepatitis and of adenovirus infections based on laboratory data and clinical coding. We relaxed the stringent case definition adopted during the AS-Hep-UA to identify all cases of acute hepatitis with unknown aetiology (termed AHUA). We compared events within the outbreak period (defined as 1st Oct 2021-31 Aug 2022) to the rest of our study period.

RESULTS

Over the study period, there were 903,433 acute presentations overall, of which 391 (0.04%) were classified as AHUA. AHUA episodes had significantly higher critical care admission rates (p < 0.0001, OR = 41.7, 95% CI:26.3-65.0) and longer inpatient admissions (p < 0.0001) compared with the rest of the patient population. During the outbreak period, significantly more adults (≥ 16 years) were diagnosed with AHUA (p < 0.0001, OR = 3.01, 95% CI: 2.20-4.12), and there were significantly more human adenovirus (HadV) infections in children (p < 0.001, OR = 1.78, 95% CI:1.27-2.47). There were also more HAdV tests performed during the outbreak (p < 0.0001, OR = 1.27, 95% CI:1.17-1.37). Among 3,707 individuals who were tested for HAdV, 179 (4.8%) were positive. However, there was no evidence of more acute hepatitis or increased severity of illness in HadV-positive compared to negative cases.

CONCLUSIONS

Our results highlight an increase in AHUA in adults coinciding with the period of the outbreak in children, but not linked to documented HAdV infection. Tracking changes in routinely collected clinical data through EHR could be used to support outbreak surveillance.

Human HPSE2 gene transfer ameliorates bladder pathophysiology in a mutant mouse model of urofacial syndrome

Rare early-onset lower urinary tract disorders include defects of functional maturation of the bladder. Current treatments do not target the primary pathobiology of these diseases. Some have a monogenic basis, such as urofacial, or Ochoa, syndrome (UFS). Here, the bladder does not empty fully because of incomplete relaxation of its outflow tract, and subsequent urosepsis can cause kidney failure. UFS is associated with biallelic variants of HPSE2, encoding heparanase-2. This protein is detected in pelvic ganglia, autonomic relay stations that innervate the bladder and control voiding. Bladder outflow tracts of Hpse2 mutant mice display impaired neurogenic relaxation. We hypothesized that HPSE2 gene transfer soon after birth would ameliorate this defect and explored an adeno-associated viral (AAV) vector-based approach. AAV9/HPSE2, carrying human HPSE2 driven by CAG, was administered intravenously into neonatal mice. In the third postnatal week, transgene transduction and expression were sought, and ex vivo myography was undertaken to measure bladder function. In mice administered AAV9/HPSE2, the viral genome was detected in pelvic ganglia. Human HPSE2 was expressed and heparanase-2 became detectable in pelvic ganglia of treated mutant mice. On autopsy, wild-type mice had empty bladders, whereas bladders were uniformly distended in mutant mice, a defect ameliorated by AAV9/HPSE2 treatment. Therapeutically, AAV9/HPSE2 significantly ameliorated impaired neurogenic relaxation of Hpse2 mutant bladder outflow tracts. Impaired neurogenic contractility of mutant detrusor smooth muscle was also significantly improved. These results constitute first steps towards curing UFS, a clinically devastating genetic disease featuring a bladder autonomic neuropathy.

Genetic aetiologies of acute liver failure

Acute liver failure (ALF) is a rare, rapidly evolving, clinical syndrome with devastating consequences where definitive treatment is by emergency liver transplantation. Establishing a diagnosis can be challenging and, historically, the cause of ALF was unidentified in up to half of children. However, recent technological and clinical advances in genomic medicine have led to an increasing proportion being diagnosed with monogenic aetiologies of ALF. The conditions encountered include a diverse group of inherited metabolic disorders each with prognostic and treatment implications. Often these disorders are clinically indistinguishable and may even mimic disorders of immune regulation or red cell disorders. Rapid genomic sequencing for children with ALF is, therefore, a key component in the diagnostic work up today. This review focuses on the monogenic aetiologies of ALF.

Schlafen 11 triggers innate immune responses through its ribonuclease activity upon detection of single-stranded DNA

Nucleic acids are major structures detected by the innate immune system. Although intracellular single-stranded DNA (ssDNA) accumulates during pathogen infection or disease, it remains unclear whether and how intracellular ssDNA stimulates the innate immune system. Here, we report that intracellular ssDNA triggers cytokine expression and cell death in a CGT motif-dependent manner. We identified Schlafen 11 (SLFN11) as an ssDNA-activated RNase, which is essential for the innate immune responses induced by intracellular ssDNA and adeno-associated virus infection. We found that SLFN11 directly binds ssDNA containing CGT motifs through its carboxyl-terminal domain, translocates to the cytoplasm upon ssDNA recognition, and triggers innate immune responses through its amino-terminal ribonuclease activity that cleaves transfer RNA (tRNA). Mice deficient in Slfn9, a mouse homolog of SLFN11, exhibited resistance to CGT ssDNA-induced inflammation, acute hepatitis, and septic shock. This study identifies CGT ssDNA and SLFN11/9 as a class of immunostimulatory nucleic acids and pattern recognition receptors, respectively, and conceptually couples DNA immune sensing to controlled RNase activation and tRNA cleavage.

The Blood Virome: A new frontier in biomedical science

Recent advances in metagenomic testing opened a new window into the mammalian blood virome. Comprised of well-known viruses like human immunodeficiency virus, hepatitis C virus, and hepatitis B virus, the virome also includes many other eukaryotic viruses and phages whose medical significance, lifecycle, epidemiology, and impact on human health are less well known and thus regarded as commensals. This review synthesizes available information for the so-called commensal virome members that circulate in the blood of humans considering their restriction to and interaction with the human host, their natural history, and their impact on human health and physiology.

The Outbreak of Unexplained Acute Hepatitis in Children: The Role of Viral Infections in View of the COVID-19 Pandemic

BACKGROUND AND AIMS

An increase in the number of cases of acute hepatitis of unknown origin (HUO) in children was observed in 2021. Adenovirus and adeno-associated virus 2 (AAV2) infections have been suggested as possible triggers. However, the potential etiology is still unclear. We aimed to characterize a cohort of children with HUO in Israel in view of the COVID-19 pandemic.

METHOD

Demographics, clinical data, and laboratory results on the children compatible with the CDC criteria for HUO were collected by the established registry of the Ministry of Health. Available specimens were sent to the Central Virology Laboratory.

RESULTS

A total of 39 children were included in the registry. A total of 20 were enrolled prospectively, in which human herpes virus 6 (HHV6) infection or reactivation was identified in 11/19, adenovirus was found in 4/19 of the cases, and AAV2 was detected in 2/16. Past COVID-19 exposure was recorded for 24/39 of the children. A total of 10 children underwent liver biopsy, and 8 were successfully treated with steroids and 2 underwent liver transplantation.

CONCLUSIONS

The COVID-19 pandemic and the related containment measures combined with reactivation or active infection with other viruses could have been a trigger for the HUO outbreak. In our cohort, HHV6 was the most abundant finding.

Deciphering conundrums of adeno-associated virus liver-directed gene therapy: focus on hemophilia

Adeno-associated virus gene therapy has been the subject of intensive investigation for monogenic disease gene addition therapy for more than 25 years, yet few therapies have been approved by regulatory agencies. Most have not progressed beyond phase 1/2 due to toxicity, lack of efficacy, or both. The liver is a natural target for adeno-associated virus since most serotypes have a high degree of tropism for hepatocytes due to cell surface receptors for the virus and the unique liver sinusoidal geometry facilitating high volumes of blood contact with hepatocyte cell surfaces. Recessive monogenic diseases such as hemophilia represent promising targets since the defective proteins are often synthesized in the liver and secreted into the circulation, making them easy to measure, and many do not require precise regulation. Yet, despite initiation of many disease-specific clinical trials, therapeutic windows are often nonexistent, resulting in excess toxicity and insufficient efficacy. Iterative progress built on these attempts is best illustrated by hemophilia, with the first regulatory approvals for factor IX and factor VIII gene therapies eventually achieved 25 years after the first gene therapy studies in humans. Although successful gene transfer may result in the production of sufficient transgenic protein to modify the disease, many emerging questions on durability, predictability, reliability, and variability of response have not been answered. The underlying biology accounting for these heterogeneous responses and the interplay between host and virus is the subject of intense investigation and the subject of this review.

Acute Hepatitis of Unknown Origin in Children: Analysis of 17 Cases Admitted to the Bambino Gesù Children's Hospital in Rome

This study described 17 cases of children admitted to the Bambino Gesù Children's Hospital with acute hepatitis of unknown origin between mid-April and November 2022. Following the World Health Organization's working case definition of probable cases, 17 children, with a median age of 2.1 years (interquartile range: 1.0-7.1), presenting with acute hepatitis non-AE, with serum transaminase >500 IU/L, were included in the study. A pre-specified set of microbiological tests was performed on different biological specimens for all pediatric patients. All patients resulted negative for the common hepatotropic viruses. The most common pathogen detected in blood specimens was human-herpes-virus-7 (52.9%). Adenovirus was detected more frequently in stool specimens (62.5%) than in respiratory (20.0%) or blood samples (17.6%). Regarding Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, one child tested positive two days after admission, while antibodies against spike and nucleoprotein were present in 82.3% of patients. A co-pathogen detection was observed in 94.1% of children. Overall, 16 children recovered without clinical complications, while one patient required liver transplantation. In these cases of acute hepatitis of unknown origin, adenovirus was mainly detected in stool samples. A co-pathogen detection was also frequently observed, suggesting that the etiology of this acute hepatitis is most probably multifactorial.

Adeno-associated virus as a delivery vector for gene therapy of human diseases

Adeno-associated virus (AAV) has emerged as a pivotal delivery tool in clinical gene therapy owing to its minimal pathogenicity and ability to establish long-term gene expression in different tissues. Recombinant AAV (rAAV) has been engineered for enhanced specificity and developed as a tool for treating various diseases. However, as rAAV is being more widely used as a therapy, the increased demand has created challenges for the existing manufacturing methods. Seven rAAV-based gene therapy products have received regulatory approval, but there continue to be concerns about safely using high-dose viral therapies in humans, including immune responses and adverse effects such as genotoxicity, hepatotoxicity, thrombotic microangiopathy, and neurotoxicity. In this review, we explore AAV biology with an emphasis on current vector engineering strategies and manufacturing technologies. We discuss how rAAVs are being employed in ongoing clinical trials for ocular, neurological, metabolic, hematological, neuromuscular, and cardiovascular diseases as well as cancers. We outline immune responses triggered by rAAV, address associated side effects, and discuss strategies to mitigate these reactions. We hope that discussing recent advancements and current challenges in the field will be a helpful guide for researchers and clinicians navigating the ever-evolving landscape of rAAV-based gene therapy.

Development of monoclonal antibodies targeting the conserved fragment of hexon protein to detect different serotypes of human adenovirus

Human adenovirus (HAdV) infects the respiratory system, thus posing a threat to health. However, immunodiagnostic reagents for human adenovirus are limited. This study aimed to develop efficient diagnostic reagents based on monoclonal antibodies for diagnosing various human adenovirus infections. Evolutionary and homology analyses of various human adenoviral antigen genes revealed highly conserved antigenic fragments. The prokaryotic expression system was applied to recombinant penton, hexon, and IVa2 conserved fragments of adenovirus, which were injected into BALB/c mice to prepare human adenovirus-specific monoclonal antibodies. Enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence assay (IFA), and Western blotting were used to determine the immune specificity of the monoclonal antibodies. Indirect ELISA showed that monoclonal antibodies 1F10, 8D3, 4A1, and 9B2 were specifically bound to HAdV-3 and HAdV-55 and revealed high sensitivity and low detection limits for various human adenoviruses. Western blotting showed that 1F10 and 8D3 specifically recognized various human adenovirus types, including HAdV-1, HAdV-2, HAdV-3, HAdV-4, HAdV-5, HAdV-7, HAdV-21, and HAdV-55, and 4A1 specifically recognized HAdV-1, HAdV-2, HAdV-3, HAdV-5, HAdV-7, HAdV-21, and HAdV-55. IFAs showed that 1F10, 8D3, and 4A1 exhibited highly selective localization to A549 cells infected with HAdV-3 and HAdV-55. Finally, two antibody pairs that could detect hexon antigens HAdV-3 and HAdV-55 at low concentrations were developed. The monoclonal antibodies developed in this study show potential for detecting human adenoviruses.

IMPORTANCE

In this study, we selected the three most conserved antigenic fragments of human adenovirus to prepare a murine monoclonal antibody for the first time, and human adenovirus antigenic fragments with heretofore unheard of degrees of conservatism were isolated. The three monoclonal antibodies with the ability to recognize human respiratory adenovirus over a broad spectrum were screened by hybridoma and monoclonal antibody preparation. Human adenovirus infections are serious; however, therapeutic drugs and diagnostic reagents are scarce. Thus, to reduce the serious consequences of human viral infections and adenovirus pneumonitis, early diagnosis of infection is required. The present study provides three monoclonal antibodies capable of recognizing a wide range of human adenoviruses, thereby offering guidance for subsequent research and development.

[Liver transplantation in viral and autoimmune liver diseases]

BACKGROUND

Despite substantial progress in the management of viral and autoimmune liver diseases, these entities remain relevant indications for liver transplantation.

AIMS

To provide an overview of the current knowledge regarding the management of viral and autoimmune liver diseases before and after liver transplantation.

MATERIALS AND METHODS

Selective literature search, including current guidelines and abstracts of key scientific meetings.

RESULTS AND DISCUSSION

Viral and autoimmune liver disease can be effectively treated in most cases, which has resulted in an overall decline in liver transplantations for this indication group. However, hepatitis D infection and primary sclerosing cholangitis remain difficult-to-treat liver diseases in some patients and may progress to end-stage liver disease despite best possible management. Viral or autoimmune hepatitis can lead to fulminant liver failure requiring emergency liver transplantation. In patients who are transplanted due to viral or autoimmune liver disease, specific measures to prevent recurrence of these diseases after transplantation are mandatory. In view of effective treatment modalities for chronic hepatitis B and C, even liver grafts from donors infected with these viruses can be considered for liver transplantation under certain circumstances.

Pediatric acute liver failure: Current perspective in etiology and management

Pediatric acute liver failure (PALF) is a catastrophic clinical condition with very high morbidity and mortality without early detection and intervention. It is characterized by the acute onset of massive hepatocellular injury that releases circulating inflammatory mediators, resulting in metabolic disturbances, coagulopathy, hepatic encephalopathy and multi-organ failure. The etiological spectrum is dominated by hepatotropic viruses, drug-induced liver injury, metabolic and genetic disorders and immune-mediated diseases. Unlike adults, indeterminate causes for acute liver failure constitute a considerable proportion of cases of acute liver failure in children in the west. The heterogeneity of age and etiology in PALF has led to difficulties in developing prognostic scoring. The recent guidelines emphasize prompt identification of PALF, age-appropriate evaluation for hepatic encephalopathy and laboratory evaluation with careful monitoring. Current therapy focuses on supporting the failing liver and other organs, pending either spontaneous recovery or liver transplantation. Targeted therapy is available for a select group of etiologies. Liver transplantation can be lifesaving and a plan for the same should be organized, whenever indicated. The aim of this review is to define PALF, understand its etiopathogenesis, address the challenges encountered during the management and update the latest advances in liver transplantation and non-transplant treatment options in PALF.

Distinct Patterns of Liver Chemistry Changes in Pediatric Acute Hepatitis of Unknown Origin and COVID-19 Patients: A Systematic Review

In 2021 and 2022, there were noted to be clusters of pediatric acute hepatitis of unknown origin (AHUO) occurring across the globe. While there was not necessarily a global increase in cases, understanding the pattern of liver injury in AHUO is crucial to properly identify cases of this unexplained phenomenon, especially since it occurred simultaneously with a global resurgence of COVID-19. The objective of this study was to contrast the patterns in liver-relevant biochemical data from COVID-19 patients and AHUO. Studies reporting liver chemistries for cases of AHUO and COVID-19 were identified by a systematic review and search of the literature. For each case, alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin, direct bilirubin, and international normalized ratio (INR) levels were extracted as available. These were normalized to multiples of the upper limit of normal by patient age. There were statistically significant greater elevations of ALT and AST in patients with AHUO than in those with COVID-19. Only a subset of patients with COVID-19 had an AST or ALT greater than the normal range. INR elevation could be substantial for both conditions but was also statistically higher in the AHUO group. Liver chemistry changes were not statistically correlated with age. The pattern of liver chemistry changes between AHUO and COVID-19 have some distinctions, which suggests that AHUO is not a phenomenon driven primarily by SARS-CoV-2 infection alone. Differentiating AHUO and COVID-19 would be challenging based on patterns of liver chemistry changes alone.

Integration and the risk of liver cancer-Is there a real risk?

Adeno-associated virus (AAV)-based gene therapies are in clinical development for haemophilia and other genetic diseases. Since the recombinant AAV genome primarily remains episomal, it provides the opportunity for long-term expression in tissues that are not proliferating and reduces the safety concerns compared with integrating viral vectors. However, AAV integration events are detected at a low frequency. Preclinical studies in mouse models have reported hepatocellular carcinoma (HCC) after systemic AAV administration in some settings, though this has not been reported in large animal models. The risk of HCC or other cancers after AAV gene therapy in clinical studies thus remains theoretical. Potential risk factors for HCC after gene therapy are beginning to be elucidated through animal studies, but their relevance to human studies remains unknown. Studies to investigate the factors that may influence the risk of oncogenesis as well as detailed investigation of cases of cancer in AAV gene therapy patients will be important to define the potential risk of AAV genotoxicity.

Implication of viruses in the etiology of preeclampsia

Preeclampsia is one of the most common disorders that poses threat to both mothers and neonates and a major contributor to perinatal morbidity and mortality worldwide. Viral infection during pregnancy is not typically considered to cause preeclampsia; however, syndromic nature of preeclampsia etiology and the immunomodulatory effects of viral infections suggest that microbes could trigger a subset of preeclampsia. Notably, SARS-CoV-2 infection is associated with an increased risk of preeclampsia. Herein, we review the potential role of viral infections in this great obstetrical syndrome. According to in vitro and in vivo experimental studies, viral infections can cause preeclampsia by introducing poor placentation, syncytiotrophoblast stress, and/or maternal systemic inflammation, which are all known to play a critical role in the development of preeclampsia. Moreover, clinical and experimental investigations have suggested a link between several viruses and the onset of preeclampsia via multiple pathways. However, the results of experimental and clinical research are not always consistent. Therefore, future studies should investigate the causal link between viral infections and preeclampsia to elucidate the mechanism behind this relationship and the etiology of preeclampsia itself.

Severe Acute Hepatitis of Unknown Etiology in Pediatric Patients: Multidisciplinary Clinical Approach

Introduction: In mid-2022, the World Health Organization (WHO) declared a moderate-risk outbreak due to an increase in severe acute hepatitis cases of unknown etiology in children. Several reports suggested a viral infection link, with the outbreak spanning over 35 countries. By June 2022, Mexico reported 69 probable cases across 5 entities to the WHO. Case Presentation: A 4-year-old boy presented with vomiting, jaundice, choluria, and hepatomegaly. A multidisciplinary approach was employed, using an algorithm developed exclusively for clinical, epidemiological, and biochemical follow-up. Despite the negative identification of any associated microorganism and the absence of antibodies, liver function tests remained elevated. A fine needle liver biopsy was performed for diagnostic support, followed by histopathological study and sequencing and analysis of the complete high-depth transcriptome. Transcriptome analysis identified dysbiosis-related intestinal microbiota, including increased enterogenic and opportunistic pathogenic bacteria of the genus Clostridium, as well as HERV-K113, implicated in autoimmune disease development. Conclusions: The study's findings suggest possible immune-mediated mechanisms involving dysbiosis of the gut microbiota and the potential role of HERV-K113. Management and control of acute liver disease depend on specific causes, with the main challenge being early determination and implementation of optimal management strategies. The exact pathological mechanisms underlying pediatric acute hepatitis of unknown etiology remain elusive, warranting further studies to confirm or refute these hypotheses and elucidate the underlying pathological mechanisms

Histopathological findings from the investigation of paediatric acute hepatitis of unknown aetiology, United Kingdom 2022

In 2022, there were global reports of increased numbers of acute hepatitis not explained by hepatitis A-E virus infection in children. This manuscript summarises histopathology results from 20 patients in the United Kingdom who underwent liver transplant or had a liver biopsy as part of aetiological investigations. All available histopathological samples were reviewed centrally as part of the outbreak investigation. A working group comprised of infection specialists, hepatologists and histopathologists met virtually to review the cases, presentation, investigations and histopathology. All 20 liver samples had evidence of inflammation without significant interface activity, and submassive confluent pan-lobular or multilobular hepatocellular necrosis. Overall, the predominant histopathological findings were of acute nonspecific hepatitis with submassive hepatic necrosis and central vein perivenulitis and endothelitis. Histopathological findings were a poor indicator of aetiology.

Adeno-associated viruses for gene therapy - clinical implications and liver-related complications, a guide for hepatologists

Gene therapy has garnered increasing interest over recent decades. Several therapies employing gene transfer mechanisms have been developed, and, of these, adeno-associated virus (AAV) vectors have demonstrated viability for use with in vivo gene therapy. Several AAV-based therapeutics have received regulatory approval in the last few years including those for retinal disease, spinal muscular atrophy or aromatic L-amino acid decarboxylase deficiency. Lately, with the introduction of novel liver-directed AAV vector-based therapeutics for the treatment of haemophilia A and B, gene therapy has attracted significant attention in the hepatology community, with the liver increasingly recognised as a target for gene therapy. However, the introduction of foreign DNA into hepatocytes is associated with a risk of hepatic reactions, with raised ALT (alanine aminotransferase) and AST (aspartate aminotransferase) being - so far - the most commonly reported side effects. The complete mechanisms underlying the ALT flairs remain to be determined and the long-term risks associated with these new treatments is not yet known. The liver community is increasingly being asked to support liver-directed gene therapy to mitigate potential liver associated harm. In this review, we focus on AAV vector-based gene therapy, shedding light on this promising technique and its remarkable success in haemophilia, with a special focus on hepatic complications and their management in daily clinical practice.

Liver abnormalities following SARS-CoV-2 infection in children 1 to 10 years of age

OBJECTIVE

Beginning in October 2021 in the USA and elsewhere, cases of severe paediatric hepatitis of unknown aetiology were identified in young children. While the adenovirus and adenovirus-associated virus have emerged as leading aetiological suspects, we attempted to investigate a potential role for SARS-CoV-2 in the development of subsequent liver abnormalities.

DESIGN

We conducted a study using retrospective cohorts of deidentified, aggregated data from the electronic health records of over 100 million patients contributed by US healthcare organisations.

RESULTS

Compared with propensity score matched children with other respiratory infections, children aged 1-10 years with COVID-19 had a higher risk of elevated transaminases (HR (95% CI) 2.16 (1.74 to 2.69)) or total bilirubin (HR (95% CI) 3.02 (1.91 to 4.78)), or new diagnoses of liver diseases (HR (95% CI) 1.67 (1.21 to 2.30)) from 1 to 6 months after infection. Patients with pre-existing liver abnormalities, liver abnormalities surrounding acute infection, younger age (1-4 years) or illness requiring hospitalisation all had similarly elevated risk. Children who developed liver abnormalities following COVID-19 had more pre-existing conditions than those who developed abnormalities following other infections.

CONCLUSION

These results indicate that SARS-CoV-2 may prime the patient for subsequent development of liver infections or non-infectious liver diseases. While rare (~1 in 1000), SARS-CoV-2 is a risk for subsequent abnormalities in liver function or the diagnosis of diseases of the liver.

Viral Hepatitis Necessitating Liver Transplantation in Children

Viral hepatitis accounts for a significant global disease burden and mortality, both in children and adults. There are significant differences in the viral etiology, epidemiology, and complications in children worldwide. Children of all ages may have devastating complications with a significant risk of mortality and long-term morbidity because of viral hepatitis. Liver transplantation is the only curative option for pediatric patients with end-stage liver disease, hepatocellular carcinoma, or acute liver failure because of viral hepatitis. The introduction of universal vaccination for hepatitis B across the world and hepatitis A in some countries had led to significant changes in the incidence of disease and the need for liver transplantation for the complications of viral hepatitis in children. The development of effective treatment with directly acting antiviral agents for hepatitis C has already transformed outcomes in adults and children and reduced the need for liver transplantation. Although newer therapy for hepatitis B is being evaluated in adults, current therapy for children is not curative, indicating the need for lifelong therapy and potential necessity for liver transplantation. The recent epidemic of acute hepatitis in children across the world has highlighted the importance of understanding the etiology of unusual causes for acute liver failure and the urgent need for liver transplantation.

Demystifying the global outbreak of severe acute hepatitis of unknown aetiology in children: A systematic review and meta-analysis

BACKGROUND

The sudden outbreak of severe acute hepatitis of unknown aetiology (SAHUA) in the first half of 2022 affected more than 1010 children in 35 countries worldwide. Dire clinical outcomes, such as acute liver failure necessitating transplantation, neurological symptoms, long-term sequelae, and death, highlight the need to determine the pathogenesis of this condition. Hypotheses on the aetiology include adenovirus and SARS-CoV-2 infections and an aberrant immune response to multiple pathogen exposure following lifting of lockdown measures but further investigation is required to reach an informed consensus.

METHODS

A literature search was performed on MEDLINE and EMBASE in accordance with PRISMA guidelines for systematic reviews. Primary studies reporting data on severe acute hepatitis of unknown aetiology in children from the COVID-19 era were selected for inclusion in our review. Data on patient demographics, clinical presentation and outcomes, and diagnostic testing for coinfection were extracted. Meta-analysis used a random-effects model.

RESULTS

The 33 included studies (30 case series and 3 case-control studies) described a total of 3636 cases of SAHUA (reported 1 January, 2019-31 December, 2022), with a median age of 3.5 years. Of these, 214 children (5.9%) received a liver transplant and 66 (1.8%) died. Whilst data on diagnostic testing was incomplete, the most frequently detected coinfections were with adenovirus and/or adeno-associated virus 2 (AAV2). Other common childhood respiratory and enteric pathogens, such as enterovirus, rhinovirus, and herpesviruses (EBV and HHV-6), were also identified.

CONCLUSION

Coinfection with AAV2 and other common childhood pathogens may predispose children to develop this novel severe hepatitis. Altered susceptibility and response to such pathogens may be a consequence of immunological naivety following pandemic restrictions. Further investigations are needed to generate high-quality evidence on aetiology for different patient demographics and geographical areas.