Intestinal HAdV Infection: Tissue Specificity, Persistence, and Implications for Antiviral Therapy

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.

Adenovirus infections: new insights for the clinical laboratory

Since their discovery in 1953, research on human adenoviruses (HAdVs) has had diverse foci, resulted in groundbreaking discoveries, such as gene splicing, and generated powerful oncolytic constructs and expression vectors for vaccine development and gene therapy. In contrast, virologists working in this field have made relatively little progress toward the prevention and treatment of the wide spectrum of HAdV-associated diseases. The understanding of species-specific features of viral pathogenesis, or of the mechanisms underlying the establishment of latency and reactivation, is still limited. This group of viruses currently comprises 7 species, 51 serotypes, and 116 unique genotypes. This complexity manifests with a challenging pathophenotypic diversity. Some types are highly virulent, and others do not seem to cause disease in immunocompetent hosts. The assessment of viral load in blood and respiratory specimens has well-acknowledged clinical utility, but the lack of virus typing capabilities easily implementable in clinical laboratories represents a lingering major limitation to the interpretation of positive tests. Some HAdV infections do have severe consequences for both immunocompetent and immunocompromised patients, and the understanding of why this is the case will require more research. Clinical isolates and collections of positive specimens can provide unique resources to investigate the molecular bases of viral virulence and fitness and also help gather information of spatial-temporal patterns of viral circulation in susceptible communities, but they are extremely scarce. Clinical laboratories are underutilized interfaces between patients and academic scientists and have, therefore, a high potential to become valuable collaborators in research moving forward.

Isolation of a recombinant simian adenovirus encoding the human adenovirus G52 hexon suggests a simian origin for human adenovirus G52

Human adenoviruses (HAdVs) are causative agents of morbidity and mortality throughout the world. These double-stranded DNA viruses are phylogenetically classified into seven different species (A-G). HAdV-G52, originally isolated in 2008 from a patient presenting with gastroenteritis, is the sole human-derived member of species G. Phylogenetic analysis previously suggested that HAdV-G52 may have a simian origin, indicating a potential zoonotic spillover into humans. However, evidence of HAdV-G52 in either human or simian populations has not been reported since. Here, we describe the isolation and in vitro characterization of rhesus (rh)AdV-69, a novel simian AdV with clear evidence of recombination with HAdV-G52, from the stool of a rhesus macaque. Specifically, the rhAdV-69 hexon capsid protein is 100% identical to that of HAdV-G52, whereas the remainder of the genome is most similar to rhAdV-55, sharing 95.36% nucleic acid identity. A second recombination event with an unknown adenovirus (AdV) is evident at the short fiber gene. From the same sample, we also isolated a second, highly related recombinant AdV (rhAdV-68) that harbors a distinct hexon gene but nearly identical backbone compared to rhAdV-69. In vitro, rhAdV-68 and rhAdV-69 demonstrate comparable growth kinetics and tropisms in human cell lines, nonhuman cell lines, and human enteroids. Furthermore, we show that coinfection of highly related AdVs is not unique to this sample since we also isolated coinfecting rhAdVs from two additional rhesus macaque stool samples. Our data collectively contribute to elucidating the origins of HAdV-G52 and provide insights into the frequency of coinfections and subsequent recombination in AdV evolution.IMPORTANCEUnderstanding the host origins of adenoviruses (AdVs) is critical for public health as transmission of viruses from animals to humans can lead to emergent viruses. Recombination between animal and human AdVs can also produce emergent viruses. HAdV-G52 is the only human-derived member of the HAdV G species. It has been suggested that HAdV-G52 has a simian origin. Here, we isolated from a rhesus macaque, a novel rhAdV, rhAdV-69, that encodes a hexon protein that is 100% identical to that of HAdV-G52. This observation suggests that HAdV-G52 may indeed have a simian origin. We also isolated a highly related rhAdV, differing only in the hexon gene, from the same rhesus macaque stool sample as rhAdV-69, illustrating the potential for co-infection of closely related AdVs and recombination at the hexon gene. Furthermore, our study highlights the critical role of whole-genome sequencing in understanding AdV evolution and monitoring the emergence of pathogenic AdVs.

Pathogenicity and virulence of human adenovirus F41: Possible links to severe hepatitis in children

Over 100 human adenoviruses (HAdVs) have been isolated and allocated to seven species, A-G. Species F comprises two members-HAdV-F40 and HAdV-F41. As their primary site of infection is the gastrointestinal tract they have been termed, with species A, enteric adenoviruses. HAdV-F40 and HAdV-F41 are a common cause of gastroenteritis and diarrhoea in children. Partly because of difficulties in propagating the viruses in the laboratory, due to their restrictions on growth in many cell lines, our knowledge of the properties of individual viral proteins is limited. However, the structure of HAdV-F41 has recently been determined by cryo-electron microscopy. The overall structure is similar to those of HAdV-C5 and HAdV-D26 although with some differences. The sequence and arrangement of the hexon hypervariable region 1 (HVR1) and the arrangement of the C-terminal region of protein IX differ. Variations in the penton base and hexon HVR1 may play a role in facilitating infection of intestinal cells by HAdV-F41. A unique feature of HAdV-F40 and F41, among human adenoviruses, is the presence and expression of two fibre genes, giving long and short fibre proteins. This may also contribute to the tropism of these viruses. HAdV-F41 has been linked to a recent outbreak of severe acute hepatitis "of unknown origin" in young children. Further investigation has shown a very high prevalence of adeno-associated virus-2 in the liver and/or plasma of some cohorts of patients. These observations have proved controversial as HAdV-F41 had not been reported to infect the liver and AAV-2 has generally been considered harmless.

Immunomodulation by Enteric Viruses

Enteric viruses display intricate adaptations to the host mucosal immune system to successfully reproduce in the gastrointestinal tract and cause maladies ranging from gastroenteritis to life-threatening disease upon extraintestinal dissemination. However, many viral infections are asymptomatic, and their presence in the gut is associated with an altered immune landscape that can be beneficial or adverse in certain contexts. Genetic variation in the host and environmental factors including the bacterial microbiota influence how the immune system responds to infections in a remarkably viral strain-specific manner. This immune response, in turn, determines whether a given virus establishes acute versus chronic infection, which may have long-lasting consequences such as susceptibility to inflammatory disease. In this review, we summarize our current understanding of the mechanisms involved in the interaction between enteric viruses and the immune system that underlie the impact of these ubiquitous infectious agents on our health.

Enteric and non-enteric adenoviruses in children with acute gastroenteritis in Western India

Human adenoviruses (HAdVs) are the viral agents responsible for a wide spectrum of acute and chronic diseases. HAdVs are the most important etiological agents of acute gastroenteritis (AGE) and are identified as the major contributor to the deaths of diarrheal children globally. The significant rise in HAdV infections in rotavirus-vaccinated children documented in multiple studies demands continuous monitoring of HAdV strains. After the inclusion of rotavirus vaccines in the immunization schedule of India, public health research regarding prevalence, etiology, and risk factors is highly necessary for evidence-based policies and their implementation to sustain diarrhea prevention programs. In the present study, children admitted for AGE between 2013 and 2016 in seven different hospitals in Maharashtra and Gujrat states of Western India were subjected for investigation. HAdVs were found in 5.2% of the fecal specimens with the dominance of species-F (52.4%) strains, followed by the occurrence of non-enteric adenoviruses of species A (17.4%), C (11.4%), B (8.2%), and D (3.2%). The species-F strains were predominant in Ahmadabad (78.5%), Mumbai (61.5%), and Surat (57.1%) cities, followed by species-A strains. In Pune city, species B strains were detected in all HAdV patients, with none of the species A strains. Clinically, patients infected with enteric and non-enteric HAdV strains were indistinguishable. However, a high viral load was observed in species-F specimens as compared to non-species-F. The present study on fecal specimens collected in the pre-rotavirus vaccination era from hospitalized AGE patients will be important for future comparative analysis to know the exact impact of vaccination in children of Western India.

Surface characterization of alkane viral anchoring films prepared by titanate-assisted organosilanization

Studies of virus adsorption on surfaces with optimized properties have attracted a lot of interest, mainly due to the influence of the surface in the retention, orientation and stability of the viral capsids. Besides, viruses in whole or in parts can be used as cages or vectors in different areas, such as biomedicine and materials science. A key requirement for virus nanocage application is their physical properties, i.e. their mechanical response and the distribution of surface charge, which determine virus-substrate interactions and stability. In the present work we show two examples of viruses exhibiting strong surface interactions on homogeneous hydrophobic surfaces. The surfaces were prepared by titanate assisted organosilanization, a sol-gel spin coating process, followed by a mild annealing step. We show by surface and interface spectroscopies that the process allows trapping triethoxy-octylsilane (OCTS) molecules, exhibiting a hydrophobic alkane rich surface finishing. Furthermore, the surfaces remain flat and behave as more efficient sorptive surfaces for virus particles than mica or graphite (HOPG). Also, we determine by atomic force microscopy (AFM) the mechanical properties of two types of viruses (human adenovirus and reovirus) and compare the results obtained on the OCTS functionalized surfaces with those obtained on mica and HOPG. Finally, the TIPT+OCTS surfaces were validated as platforms for the morphological and mechanical characterization of virus particles by using adenovirus as initial model and using HOPG and mica as standard control surfaces. Then, the same characteristics were determined on reovirus using TIPT+OCTS and HOPG, as an original contribution to the catalogue of physical properties of viral particles.

Intestinal Shedding of SARS-CoV-2 in Children: No Evidence for Infectious Potential

The clinical courses of COVID-19 in children are often mild and may remain undiagnosed, but prolonged intestinal virus shedding has been documented, thus potentially enabling fecal-oral transmission. However, the infectious potential of SARS-CoV-2 viruses excreted with feces has remained unclear. Here, we investigated 247 stool specimens from 213 pediatric patients to assess the prevalence of intestinal SARS-CoV-2 shedding in hospitalized children without or with COVID-19 and determined the infectious capacity of stool-borne viruses. Upon RT-qPCR screening, the infectivity of virus-positive samples was tested in cell culture using the Vero-E6 permissive cell line. SARS-CoV-2 RNA was detected by RT-qPCR in 32 (13%) stool specimens, but the analysis of virus-positive samples in cell culture revealed no cytopathic effects attributable to SARS-CoV-2-related cell damage. Our findings do not support the notion of potential fecal-oral SARS-CoV-2 spreading, thus questioning the role of hygienic measures designed to prevent this mode of viral transmission.

Multi-omic interactions in the gut of children at the onset of islet autoimmunity

BACKGROUND

The gastrointestinal ecosystem is a highly complex environment with a profound influence on human health. Inflammation in the gut, linked to an altered gut microbiome, has been associated with the development of multiple human conditions including type 1 diabetes (T1D). Viruses infecting the gastrointestinal tract, especially enteroviruses, are also thought to play an important role in T1D pathogenesis possibly via overlapping mechanisms. However, it is not known whether the microbiome and virome act together or which risk factor may be of greater importance at the time when islet autoimmunity is initiated.

RESULTS

Here, we apply an integrative approach to combine comprehensive fecal virome, microbiome, and metaproteome data sampled before and at the onset of islet autoimmunity in 40 children at increased risk of T1D. We show strong age-related effects, with microbial and metaproteome diversity increasing with age while host antibody number and abundance declined with age. Mastadenovirus, which has been associated with a reduced risk of T1D, was associated with profound changes in the metaproteome indicating a functional shift in the microbiota. Multi-omic factor analysis modeling revealed a cluster of proteins associated with carbohydrate transport from the genus Faecalibacterium were associated with islet autoimmunity.

CONCLUSIONS

These findings demonstrate the interrelatedness of the gut microbiota, metaproteome and virome in young children. We show a functional remodeling of the gut microbiota accompanies both islet autoimmunity and viral infection with a switch in function in Faecalibacterium occurring at the onset of islet autoimmunity. Video Abstract.

Acute hepatitis of unknown origin in children: A combination of factors

On 5 April 2022, the World Health Organization was notified of 10 cases of severe acute hepatitis of unknown etiology in children under 10 years of age in the United Kingdom. Although the exact cause of a proportion of pediatric acute hepatitis and acute liver failure cases was unclear, the above event has caused widespread concern worldwide. As of 14 September 2022, approximately 1,296 probable cases of acute hepatitis of unknown etiology have been reported from 37 countries/regions, of which approximately 55 required or received liver transplantation and 29 died. Although the etiology of acute hepatitis of unknown origin in children remains unclear, many hypotheses have been proposed about the disease. Instead of individual factors such as "adenovirus infection," "SARS-CoV-2 related," and "Adeno-associated virus 2 with helper virus coinfection," it is more likely due to a combination of factors. Accordingly, there is an urgent need for more data and research to clarify the disease etiology. This review aims to provide a historical perspective of acute hepatitis of unknown etiology in children in the past decades and summarize the current hypothesis and evidence on this emerging disease.

A link between severe hepatitis in children and adenovirus 41 and adeno-associated virus 2 infections

Over the past few months there have been reports of severe acute hepatitis in several hundred, otherwise healthy, immunocompetent young children. Several deaths have been recorded and a relatively large proportion of the patients have needed liver transplants. Most of the cases, so far, have been seen in the UK and in North America, but it has also been reported in many other European countries, the Middle East and Asia. Most common viruses have been ruled out as a causative agent; hepatitis A virus (HAV), hepatitis B virus (HBV) and hepatitis C virus (HCV) were not detected, nor were Epstein–Barr virus (EBV), cytomegalovirus (CMV) and human immunodeficiency virus (HIV) in many cases. A small proportion of the children had been infected with SARS-CoV-2 but these seem to be in a minority; similarly, almost none of the children had been vaccinated against COVID-19. Significantly, many of the patients were infected with adenovirus 41 (HAdV-F41). Previously, HAdV-41 had not been linked to hepatitis and is usually considered to cause gastroenteritis in both immunocompetent and immunocompromised patients. In two most recent studies, adeno-associated virus 2 (AAV2) was detected in almost all patients, together with species C and F HAdVs and human herpesvirus 6B (HHV6B). Here, I discuss the possibility that a change in tropism of HAdV-41 and changes in AAV2 may be responsible for their links to acute hepatitis.

Molecular epidemiology of human adenoviruses in children with and without respiratory symptoms: Preliminary findings from a case-control study

Background

Human adenovirus (HAdV) is an important viral agent in children which can lead to severe acute respiratory infection (SARI). Reports on molecular epidemiology of HAdVs in Iran are limited. This case-control study is conducted to compare the HAdV infection rate and molecular epidemiology among two groups of children with and without respiratory symptoms in Tehran, Iran during 2018–2019.

Methods

Nested PCR was performed on 120 oropharyngeal swabs taken from children aged five and younger with SARI who were hospitalized as the case group, and 120 oropharyngeal swabs were collected from children of the same age without respiratory symptoms as the control group. For positive samples Sanger sequencing was done and a phylogenetic tree was drawn afterward.

Results

Out of 120 cases, 8 (6.6%) tested positive for eachHAdV types including 6 (75%) HAdV-B7, 1 (12.5%) HAdV-C2, and 1 (12.5%) HAdV-C6. Among the control group, out of 120 samples, 8 (6.6%) were positive comprising 5 (62.5%) HAdV-C5, 2 (25%) HAdV-F41, and 1 (12.5%) HAdV-C6.

Conclusion

The present study indicated a different viewpoint of HAdV molecular epidemiology in which the genotypes were compared in children with and without respiratory symptoms. HAdV prevalence was equally common in cases and controls but different genotypes were detected in these two groups. HAdV-B7 was the main type among children with SARI, dissimilar to children with no respiratory symptoms where HAdV-C5 was the predominant type. Detecting HAdV-F in oropharyngeal swabs was a rare finding, which requires further investigation.

Global public health implications of human exposure to viral contaminated water

Enteric viruses are common waterborne pathogens found in environmental water bodies contaminated with either raw or partially treated sewage discharge. Examples of these viruses include adenovirus, rotavirus, noroviruses, and other caliciviruses and enteroviruses like coxsackievirus and polioviruses. They have been linked with gastroenteritis, while some enteric viruses have also been implicated in more severe infections such as encephalitis, meningitis, hepatitis (hepatitis A and E viruses), cancer (polyomavirus), and myocarditis (enteroviruses). Therefore, this review presents information on the occurrence of enteric viruses of public health importance, diseases associated with human exposure to enteric viruses, assessment of their presence in contaminated water, and their removal in water and wastewater sources. In order to prevent illnesses associated with human exposure to viral contaminated water, we suggest the regular viral monitoring of treated wastewater before discharging it into the environment. Furthermore, we highlight the need for more research to focus on the development of more holistic disinfection methods that will inactivate waterborne viruses in municipal wastewater discharges, as this is highly needed to curtail the public health effects of human exposure to contaminated water. Moreover, such a method must be devoid of disinfection by-products that have mutagenic and carcinogenic potential.

Quantitative analysis of respiratory viral distribution in forensic autopsy cases

Respiratory viruses can cause fatal systemic infections; therefore, post-mortem diagnosis is essential in forensic autopsy cases. However, little is known regarding the distribution of respiratory viruses in the body. In this study, we investigated the anatomical distribution of respiratory viruses in 48 forensic autopsy cases suspected of viral infections at our institute. Fast Track Diagnostics (FTD) Respiratory Pathogens 21 was used as a screening test for 20 respiratory viruses in nasopharyngeal swabs. In cases with positive results for virus detection by the screening test, the detected viruses were quantified in body fluid and organ specimens by virus-specific real-time reverse transcription polymerase chain reaction (RT-PCR) and digital PCR. Viruses were detected in 33 cases, with the viral distribution and load differing among the cases. Since various respiratory viruses were detected from the nasopharyngeal swab and its viral load was higher than those of other body fluid specimens, the nasopharyngeal swab was suggested as a useful specimen for the post-mortem detection of respiratory viruses. Viruses were detected in almost all specimens including the serum in six cases. Considering the viral distribution in the body, pathological findings, and ante-mortem symptoms, these cases were presumed to be systemically infected, having died in the acute infection phase. In conclusion, the anatomical distribution of respiratory viruses can help indicate ante-mortem systemic conditions and the cause of death.

High genetic stability of co-circulating human adenovirus type 31 lineages over 59 years

Type 31 of human adenovirus species A (HAdV-A31) is a significant pathogen primarily associated with diarrhoea in children but also with life-threatening disseminated disease in allogeneic haematopoietic stem cell transplant (HSCT) recipients. Nosocomial outbreaks of HAdV-A31 have been frequently described. However, the evolution of HAdV-A31 has not been studied in detail. The evolution of other HAdV types is driven either by intertypic recombination, where different types exchange genome regions, or by immune escape selection of neutralisation determinants. Complete genomic HAdV-A31 sequences from sixty diagnostic specimens of the past 18 years (2003-21) were generated, including fourteen specimens of a presumed outbreak on two HSCT wards. Additionally, twenty-three complete genomes from GenBank were added to our phylogenetic analysis as well as in silico generated and previously published restriction fragment polymorphism (RFLP) data. Phylogenetic analysis of eighty-three genomes indicated that HAdV-A31 evolved slowly with six lineages co-circulating. The two major lineages were lineage 1, which included the prototype from 1962 and nine recent isolates, and lineage 2, which split into four sublineages and included most isolates from 2003 to 2021. The average nucleotide identity within lineages was high (99.8 per cent) and identity between lineages was 98.7 and 99.2 per cent. RFLP data allowed the construction of a lower-resolution phylogeny with two additional putative lineages. Surprisingly, regions of higher diversity separating lineages were found in gene regions coding for non-structural and minor capsid proteins. Intertypic recombinations were not observed, but the phylogeny of lineage 3 was compatible with an interlineage recombination event in the fibre gene. Applying the phylogenetic analysis to the presumed nosocomial outbreak excluded two suspected transmission events and separated it into two different, simultaneous outbreaks caused by different sublineages of lineage 2. However, due to the high nucleotide identity within HAdV-A31 lineages, the proof of infection chains remains debatable. This in-depth study on the molecular phylogeny of HAdV-A31 highlights the high genetic stability of co-circulating HAdV-A31 lineages over almost six decades. It also supports the epidemiological hypothesis that HAdV-A31 circulates as an etiological agent of a childhood disease infecting immunologically naive patients without strong positive selection of immune escape variants and recombinants.

Adenovirus is prevalent in juvenile polyps and correlates with low vitamin D receptor expression

BACKGROUND

The objective of this study was to assess human adenovirus (HAdV) infection in juvenile polyps (JPs) and to preliminarily establish a correlation to vitamin D receptor (VDR) expression.

METHODS

The study includes 76 patients of 5.2 ± 2.8 years old. Seventy-eight JP specimens and 24 parapolyp tissues from polypectomy were used. PCR was used to detect HAdV DNA and quantitative reverse transcription-PCR for viral and host gene expression. The PCR products were sequenced for virus typing. The correlation between VDR expression and HAdV infection was established using nonparametric Spearman's analysis.

RESULTS

Seventy-four children (97.4%) had a single polyp and two had two polyps. The histopathological characteristics of the polyps were in line with JP. Thirty-three samples had HAdV DNA (43.4%), including 32 subgroup C and 1 subgroup B HAdV; no enteric HAdV was detected. HAdV messenger RNA was detected in 5 of the 33 samples (15.2%). The samples had increased interleukin-1β (IL-1β), IL-6, and calprotectin expression, and reduced E-cadherin and VDR expression. JP samples with low VDR expression were more prevalent of HAdV DNA (r = 1.261, 95% confidence interval, 1.017-1.563), while VDR expression positively correlated with E-cadherin and negatively with inflammation gene expression.

CONCLUSIONS

HAdV latent infection was prevalent among JP tissues. The presence of HAdV correlated positively to low VDR expression.

IMPACT

The HAdVs infect the upper airways and gastrointestinal system and is found to persist in lymphoid tissues. The prevalence of HAdV and the status of the infection is unknown. The study investigated the prevalence of HAdV from polypectomy specimens of JP patients and found that HAdV was prevalent and was in a persistent state. HAdV infection was more prevalent in samples with low VDR expression. Whether HAdV infection and reactivation is a contributing factor to JPs is unknown. Factors such as proinflammation and bacterial metabolites that are known to promote HAdV reactivation warrant further investigation.

The Effects of β-Pinene, a Pine Needle Oil Monoterpene, on Adenovirus Type 3

The mechanisms of the inhibitory action of β-pinene, a pine needle oil monoterpene, on human adenovirus type 3 were studied using cytopathic inhibition test, MTT test, atomic force and laser confocal microscopy. β-Pinene inhibited the viruses stronger that the reference antiviral medication ribavirin (p<0.05). Inhibition of viral cytopathic effect (CPE) increased with increasing the concentration of β-pinene, which attested to direct elimination of adenovirus type 3. During viral reproduction phase, β-pinene significantly inhibited proliferation of adenovirus type 3. Typical signs of adenoviral CPE as cell swelling and rounding were less pronounced in comparison with the control (ribavirin treatment). In addition, elevation of β-pinene concentration significantly increased the cell survival rate (p<0.05). Laser confocal microscopy showed that fluorescence intensity in the β-pinene group was significantly lower than in the control group (p<0.01), which was consistent with the results of MTT test, thereby providing additional arguments that β-pinene affects the virus during the absorption phase. Thus, β-pinene directly inactivates adenovirus type 3 and impedes its invasion into the cells, but produces no protective effects on cells. Understanding the mode of action of such monoterpenes as β-pinene is of great importance for the development of new antiviral drugs.

KIR3DS1 directs NK cell-mediated protection against human adenovirus infections

[Figure: see text].

Detection and molecular characterization of enteric adenovirus in treated wastewater in the Brazilian Federal District

Human enteric viruses, such as enteric adenoviruses (HAdV), are known to be involved with gastrointestinal disorders, especially acute gastroenteritis. Several studies have used HAdV as an indicator of water quality, since they are considered highly stable and widely distributed viruses in water matrices. The aim of this study was to detect and genotype HAdVs in water matrices impacted by discharges of treated effluents from wastewater treatment plants (WWTPs). Wastewater treatment plants from the sanitary system of the Brazilian Federal District were assessed in 2018 and 2019. Samples were collected upstream and downstream from discharge points for each WWTP. Viral concentration based on adsorption-elution and conventional PCR was used for molecular detection, and positive samples were sequenced for phylogenetic analysis. Pluviosity data for the period in which the samples were collected were obtained. Our results demonstrated the presence of HAdVs in 27.2% (61/224) of the samples. The positivity was significantly higher in downstream samples compared to upstream. Moreover, the HAdV positivity was higher in downstream samples collected from receiving water bodies impacted by secondary-level WWTPs in comparison with those impacted by tertiary-level WWTPs. Phylogenetic analysis demonstrated the presence of genotypes 40 and 41, with prevalence of HAdV genotype 41. Despite the predominance of HAdV-41, an increasing frequency of the HAdV-40 was associated with higher pluviosity. In conclusion, this study is the first documentation in the Brazilian Federal District dealing with the prevalence and diversity of HAdVs in several WWTP, along with their correlation with rainfall index.

Intracellular Sequestration of the NKG2D Ligand MIC B by Species F Adenovirus

The enteric human adenoviruses of species F (HAdVs-F), which comprise HAdV-F40 and HAdV-F41, are significant pathogens that cause acute gastroenteritis in children worldwide. The early transcription unit 3 (E3) of HAdVs-F is markedly different from that of all other HAdV species. To date, the E3 proteins unique to HAdVs-F have not been characterized and the mechanism by which HAdVs-F evade immune defenses in the gastrointestinal (GI) tract is poorly understood. Here, we show that HAdV-F41 infection of human intestinal HCT116 cells upregulated the expression of MHC class I-related chain A (MIC A) and MIC B relative to uninfected cells. Our results also showed that, for MIC B, this response did not however result in a significant increase of MIC B on the cell surface. Instead, MIC B was largely sequestered intracellularly. Thus, although HAdV-F41 infection of HCT116 cells upregulated MIC B expression, the ligand remained inside infected cells. A similar observation could not be made for MIC A in these cells. Our preliminary findings represent a novel function of HAdVs-F that may enable these viruses to evade immune surveillance by natural killer (NK) cells in the infected gut, thereby paving the way for the future investigation of their unique E3 proteins.

Exploring the potential of foodborne transmission of respiratory viruses

The ongoing pandemic involving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has raised the question whether this virus, which is known to be spread primarily though respiratory droplets, could be spread through the fecal-oral route or via contaminated food. In this article, we present a critical review of the literature exploring the potential foodborne transmission of several respiratory viruses including human coronaviruses, avian influenza virus (AVI), parainfluenza viruses, human respiratory syncytial virus, adenoviruses, rhinoviruses, and Nipah virus. Multiple lines of evidence, including documented expression of receptor proteins on gastrointestinal epithelial cells, in vivo viral replication in gastrointestinal epithelial cell lines, extended fecal shedding of respiratory viruses, and the ability to remain infectious in food environments for extended periods of time raises the theoretical ability of some human respiratory viruses, particularly human coronaviruses and AVI, to spread via food. However, to date, neither epidemiological data nor case reports of clear foodborne transmission of either viruses exist. Thus, foodborne transmission of human respiratory viruses remains only a theoretical possibility.

Deciphering an Adenovirus F41 Outbreak in Pediatric Hematopoietic Stem Cell Transplant Recipients by Whole-Genome Sequencing

Human adenovirus (HAdV) represents a major cause of mortality and morbidity in pediatric recipients of allogeneic hematopoietic stem cell transplants (HSCT). HAdV species F type 41 (HAdV-F41) infections in HSCT patients are scarce, whereas HAdV-F41 circulates commonly in healthy individuals. Between March and July 2018, HAdV-F41 infections were identified in four children (A, B, C, and E) who received allogeneic HSCT and one child before HSCT (D) at Robert Debré Hospital, Paris, France. We report here the clinical course of HAdV-F41 infection and the phylogenetic investigation to identify interpatient transmission. HAdV DNA was quantified in stool and plasma samples by real-time PCR. HAdV type was determined by sequencing of the fiber and hexon genes. Phylogenetic investigation was done with whole-genome sequences obtained by next-generation sequencing. HAdV loads in stool samples ranged from 6.60 to 10.10 log₁₀ copies/ml. HAdV-F41 detection in plasma was observed in four patients, but no disseminated disease was reported. Two patients died, but neither death was attributed to HAdV. While sequencing limited to the fiber gene suggested a cluster with four patients, phylogenetic analysis with whole-genome sequencing (WGS) and HVR7 revealed a cluster that included three patients (C, D, and E), suggesting an interpatient transmission in that cluster and two other independent infections. HAdV-F41 levels in stool specimens of pediatric HSCT patients are high and represent a risk of interpatient transmission. WGS helped to identify related cases. Prompt detection of HAdV in stool and control measures are warranted to limit any risk of nosocomial transmission.

Occurrence of Human Enteric Viruses in Water Sources and Shellfish: A Focus on Africa

Enteric viruses are a diverse group of human pathogens which are primarily transmitted by the faecal-oral route and are a major cause of non-bacterial diarrhoeal disease in both developed and developing countries. Because they are shed in high numbers by infected individuals and can persist for a long time in the environment, they pose a serious threat to human health globally. Enteric viruses end up in the environment mainly through discharge or leakage of raw or inadequately treated sewage into water sources such as springs, rivers, dams, or marine estuaries. Human exposure then follows when contaminated water is used for drinking, cooking, or recreation and, importantly, when filter-feeding bivalve shellfish are consumed. The human health hazard posed by enteric viruses is particularly serious in Africa where rapid urbanisation in a relatively short period of time has led to the expansion of informal settlements with poor sanitation and failing or non-existent wastewater treatment infrastructure, and where rural communities with limited or no access to municipal water are dependent on nearby open water sources for their subsistence. The role of sewage-contaminated water and bivalve shellfish as vehicles for transmission of enteric viruses is well documented but, to our knowledge, has not been comprehensively reviewed in the African context. Here we provide an overview of enteric viruses and then review the growing body of research where these viruses have been detected in association with sewage-contaminated water or food in several African countries. These studies highlight the need for more research into the prevalence, molecular epidemiology and circulation of these viruses in Africa, as well as for development and application of innovative wastewater treatment approaches to reduce environmental pollution and its impact on human health on the continent.

Heat Shock Protein 90 Chaperones E1A Early Protein of Adenovirus 5 and Is Essential for Replication of the Virus

Adenovirus infections tend to be mild, but they may pose a serious threat for young and immunocompromised individuals. The treatment is complicated because there are no approved safe and specific drugs for adenovirus infections. Here, we present evidence that 17-(Allylamino)-17-demethoxygeldanamycin (17-AAG), an inhibitor of Hsp90 chaperone, decreases the rate of human adenovirus 5 (HAdV-5) replication in cell cultures by 95%. 17-AAG inhibited the transcription of early and late genes of HAdV-5, replication of viral DNA, and expression of viral proteins. 6 h after infection, Hsp90 inhibition results in a 6.3-fold reduction of the newly synthesized E1A protein level without a decrease in the E1A mRNA level. However, the Hsp90 inhibition does not increase the decay rate of the E1A protein that was constitutively expressed in the cell before exposure to the inhibitor. The co-immunoprecipitation proved that E1A protein interacted with Hsp90. Altogether, the presented results show, for the first time. that Hsp90 chaperones newly synthesized, but not mature, E1A protein. Because E1A serves as a transcriptional co-activator of adenovirus early genes, the anti-adenoviral activity of the Hsp90 inhibitor might be explained by the decreased E1A level.

Unveiling Viruses Associated with Gastroenteritis Using a Metagenomics Approach

Acute infectious gastroenteritis is an important illness worldwide, especially on children, with viruses accounting for approximately 70% of the acute cases. A high number of these cases have an unknown etiological agent and the rise of next generation sequencing technologies has opened new opportunities for viral pathogen detection and discovery. Viral metagenomics in routine clinical settings has the potential to identify unexpected or novel variants of viral pathogens that cause gastroenteritis. In this study, 124 samples from acute gastroenteritis patients from 2012–2014 previously tested negative for common gastroenteritis pathogens were pooled by age and analyzed by next generation sequencing (NGS) to elucidate unidentified viral infections. The most abundant sequences detected potentially associated to acute gastroenteritis were from Astroviridae and Caliciviridae families, with the detection of norovirus GIV and sapoviruses. Lower number of contigs associated to rotaviruses were detected. As expected, other viruses that may be associated to gastroenteritis but also produce persistent infections in the gut were identified including several Picornaviridae members (EV, parechoviruses, cardioviruses) and adenoviruses. According to the sequencing data, astroviruses, sapoviruses and NoV GIV should be added to the list of viral pathogens screened in routine clinical analysis.

Enteric Viral Co-Infections: Pathogenesis and Perspective

Enteric viral co-infections, infections involving more than one virus, have been reported for a diverse group of etiological agents, including rotavirus, norovirus, astrovirus, adenovirus, and enteroviruses. These pathogens are causative agents for acute gastroenteritis and diarrheal disease in immunocompetent and immunocompromised individuals of all ages globally. Despite virus–virus co-infection events in the intestine being increasingly detected, little is known about their impact on disease outcomes or human health. Here, we review what is currently known about the clinical prevalence of virus–virus co-infections and how co-infections may influence vaccine responses. While experimental investigations into enteric virus co-infections have been limited, we highlight in vivo and in vitro models with exciting potential to investigate viral co-infections. Many features of virus–virus co-infection mechanisms in the intestine remain unclear, and further research will be critical.

Epidemiology of Human Adenoviruses: A 20-Year Retrospective Observational Study in Hospitalized Patients in Bern, Switzerland

BACKGROUND

Human adenovirus (HAdV) is an important pathogen seen in clinical practice. Long-term studies may help better understand epidemiological trends and changes in circulating genotypes over time.

PURPOSE

Using a large biobank of samples from hospitalized, adenovirus-positive patients over a 20-year period, we aimed to analyze long-term epidemiological trends and genotypic relatedness among circulating HAdV strains.

METHODS

Based on samples from hospitalized patients confirmed to be HAdV positive in Bern, Switzerland, from 1998 to 2017, and on their associated demographic and clinical data, we identified epidemiological trends and risk factors associated with HAdV infection. HAdV genotyping was performed by PCR amplification and sequencing of the hypervariable hexon gene. The obtained sequences were phylogenetically compared with sequences from international HAdV strains.

RESULTS

HAdV was identified in 1302 samples tested. Cases of HAdV infection were reported throughout the years with no clear seasonality. Upper respiratory tract samples, conjunctivitis swabs, and stool had the highest positivity rate (56.2%, 18.7%, and 14.2% of the cases, respectively). HAdV infection was highest among children ≤4 years old. Increased number of HAdV cases were observed in years 2009 (n = 110) and 2010 (n =112). HAdV8 was the predominant genotype among patients older than 20 years, and was mostly associated with ophthalmic infection. Predominant genotypes among children ≤4 years old were HAdV1, HAdV2, and HAdV3, which were mostly associated with respiratory tract infections. Recurring peaks of increased HAdV cases were evidenced every 4 years among children ≤4 years old.

CONCLUSION

Our study gives novel insights on long-term epidemiological trends and phylogenetic relatedness among circulating HAdV strains in Switzerland, country in which little data on HAdV prevalence and diversity was so far available.

Management of Adenoviral Keratoconjunctivitis: Challenges and Solutions

Human adenovirus (HAdV) is the most common cause of infectious conjunctivitis, accounting for up to 75% of all conjunctivitis cases and affecting people of all ages and demographics. In addition to ocular complications, it can cause systemic infections in the form of gastroenteritis, respiratory disease, and dissemination in immunocompromised individuals. HAdV causes lytic infection of the mucoepithelial cells of the conjunctiva and cornea, as well as latent infection of lymphoid and adenoid cells. Epidemic keratoconjunctivitis (EKC) is the most severe ocular manifestation of HAdV infection, in which the presence of subepithelial infiltrates (SEIs) in the cornea is a hallmark feature of corneal involvement. SEIs have the tendency to recur and may lead to long-term visual disability. HAdV persistence and dissemination are linked to sporadic outbreaks of adenoviral keratoconjunctivitis. There is no FDA-approved antiviral for treating adenoviral keratoconjunctivitis, and as such, solutions should be proffered to handle the challenges associated with viral persistence and dissemination. Several treatment modalities have been investigated, both systemically and locally, to not only mitigate symptoms but reduce the course of the infection and prevent the risk of long-term complications. These options include systemic and topical antivirals, in-office povidone-iodine irrigation (PVI), immunoglobulin-based therapy, anti-inflammatory therapy, and immunotherapy. More recently, combination PVI/dexamethasone ophthalmic formulations have shown favorable outcomes and were well tolerated in clinical trials for the treatment of EKC. Possible, future treatment considerations include sialic acid analogs, cold atmospheric plasma, N-chlorotaurine, and benzalkonium chloride. Continued investigation and evaluation of treatment are warranted to reduce the economic burden and potential long-term visual debilitation in affected patients. This review will focus on how persistence and dissemination of HAdV pose a significant challenge to the management of adenoviral keratoconjunctivitis. Furthermore, current and future trends in prophylactic and therapeutic modalities for adenoviral keratoconjunctivitis will be discussed.

Epigenetics and the dynamics of chromatin during adenovirus infections

The DNA genome of eukaryotic cells is compacted by histone proteins within the nucleus to form chromatin. Nuclear-replicating viruses such as adenovirus have evolved mechanisms of chromatin manipulation to promote infection and subvert host defenses. Epigenetic factors may also regulate persistent adenovirus infection and reactivation in lymphoid tissues. In this review, we discuss the viral proteins E1A and protein VII that interact with and alter host chromatin, as well as E4orf3, which separates host chromatin from sites of viral replication. We also highlight recent advances in chromatin technologies that offer new insights into virus-directed chromatin manipulation. Beyond the role of chromatin in the viral replication cycle, we discuss the nature of persistent viral genomes in lymphoid tissue and cell lines, and the potential contribution of epigenetic signals in maintaining adenovirus in a quiescent state. By understanding the mechanisms through which adenovirus manipulates host chromatin, we will understand new aspects of this ubiquitous virus and shed light on previously unknown aspects of chromatin biology.