Molecular identification of adenovirus sequences: a rapid scheme for early typing of human adenoviruses in diagnostic samples of immunocompetent and immunodeficient patients

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.

Characterization of Human Adenoviruses of Medical Importance: Isolation of Infectious Virus from Clinical Specimens and Molecular Typing

Human adenoviruses (HAdVs) constitute a group of ubiquitous viruses that currently comprises 51 well-defined serotypes and more than 113 genotypes classified into seven species, HAdV-A through HAdV-G. The members of these species differ considerably in their genomic characteristics and also in their tropism and pathogenicity. Virus isolation in cell culture remains critical for the preservation and comprehensive characterization of viruses of biomedical interest but has been almost completely abandoned by diagnostic laboratories. Currently, the most frequently used approach for the detection of HAdV in clinical specimens is real-time qPCR targeting a region of the hexon gene, conserved among all genotypes described to the present. In the absence of typing, the detection of an HAdV in association with disease provides limited information. Molecular typing is therefore highly desirable and required in the epidemiological investigation of HAdV-associated disease. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Virus isolation from plasma and whole blood Alternate Protocol 1: Virus isolation from stool Alternate Protocol 2: Virus isolation from respiratory specimens and urine Alternate Protocol 3: Virus isolation from tissue specimens Support Protocol: Inoculation of shell vials Basic Protocol 2: Extraction of highly pure viral genomic DNA from infected cells Basic Protocol 3: Molecular detection of human adenovirus by real-time PCR Basic Protocol 4: Molecular typing for basic identification of species and hexon type Basic Protocol 5: Typing human adenoviruses by next-generation whole-genome sequencing and analysis.

Dissemination and genome characterization of a human adenovirus F41 in a patient with B-Cell lymphoma

Adenovirus (HAdV) F41 is a common cause of gastroenteritis and has rarely been reported associated with disseminated disease. In this report, an adult patient with a history of ulcerative colitis, cryptogenic cirrhosis, stage III adenocarcinoma, high-grade diffuse large B-cell lymphoma on chemotherapy was diagnosed with disseminated adenovirus infection. HAdV DNA was quantified in stool, plasma, and urine with viral loads of 7, 4, and 3 log10 copies/mL, respectively. The patient's course was rapidly progressive and he passed away 2 days after initiation of antiviral therapy. The patient's infecting virus was characterized as HAdV-F41 by whole genome sequencing.

Molecular Typing and Rapid Identification of Human Adenoviruses Associated With Respiratory Diseases Using Universal PCR and Sequencing Primers for the Three Major Capsid Genes: Penton Base, Hexon, and Fiber

Human adenoviruses (HAdVs) within species B, C, and E are responsible for highly contagious and potentially severe respiratory disease infections. The traditional method to type these pathogens was based on virus neutralization and hemagglutination assays, which are both time-consuming and difficult, particularly due to the nonavailability of reagents. Subsequent molecular typing based on the partial characterization of the hexon gene and/or the restriction enzyme analysis (REA) of the genomes is inadequate, particularly in identifying recombinants. Here, a rapid, simple, and cost-effective method for molecular typing HAdV respiratory pathogens is presented. This incorporates three pairs of universal PCR primers that target the variable regions of the three major capsid genes, i.e., hexon, penton base, and fiber genes, that span the genome. The protocol enables typing and characterization of genotypes within species B, C, and E, as well as of some genotypes within species D and F. To validate this method, we surveyed 100 children with HAdV-associated acute respiratory infections identified by direct immunofluorescence (Hong Kong; July through October, 2014). Throat swab specimens were collected and analyzed by PCR amplification and sequencing; these sequences were characterized by BLAST. HAdVs were detected in 98 out of 100 (98%) samples, distributing as follows: 74 HAdV-B3 (74%); 10 HAdV-E4 (10%); 7 HAdV-C2 (7%); 2 HAdV-C6 (2%); 1 HAdV-B7 (1%); 1 HAdV-C1 (1%); 2 co-infection (2%); and 1 novel recombinant (1%). This study is the first detailed molecular epidemiological survey of HAdVs in Hong Kong. The developed method allows for the rapid identification of HAdV respiratory pathogens, including recombinants, and bypasses the need for whole genome sequencing for real-time surveillance of circulating adenovirus strains in outbreaks and populations by clinical virologists, public health officials, and epidemiologists.

Adenovirus Infection in Hospitalized Children with Acute Respiratory Infection in Jordan

BACKGROUND

The most common clinical manifestation of adenovirus (AdV) infection is acute respiratory illness (ARI). Specific AdV species associated with ARI hospitalizations are not well defined in the Middle East.

METHODS

A viral surveillance study was conducted among children <2 years hospitalized in Amman, Jordan, from March 2010 to March 2013. Nasal and throat respiratory specimens were obtained from enrolled children and tested for viruses using a real-time reverse-transcription quantitative polymerase chain reaction. AdV-positive specimens were typed by partial hexon gene sequencing. Demographic and clinical features were compared between AdV detected as single pathogen versus co-detected with other respiratory viruses, and between AdV-B and AdV-C species.

RESULTS

AdV was detected in 475/3168 (15%) children hospitalized with ARI; of these, 216 (45%) specimens were successfully typed with AdV-C as the most common species detected (140/216; 65%). Children with AdV-single detection (88/475; 19%) had a higher frequency of fever (71% vs. 56%; P=0.015), diarrhea (18% vs. 11%; p=0.048), and/or seizures/abnormal movements (14% vs. 5%; p=0.003). Children with AdV co-detected with other viruses more likely required oxygen support [adjusted odds ratio (aOR) 1.91 (95% CI: 1.08, 3.39), P = 0.027] than those with AdV-single detection. Children with AdV-C had higher odds of co-detections with other viruses compared with those with AdV-B [aOR 4.00 (95% CI: 1.91, 8.44), P < 0.001].

CONCLUSION

Clinical differences were identified between AdV-single and AdV co-detected with other viruses, and between AdV-B and AdV-C. Larger studies with AdV typing are needed to determine additional epidemiological and clinical differences between specific AdV species and types.

A Human In Vitro Model to Study Adenoviral Receptors and Virus Cell Interactions

To develop adenoviral cell- or tissue-specific gene delivery, understanding of the infection mechanisms of adenoviruses is crucial. Several adenoviral attachment proteins such as CD46, CAR and sialic acid have been identified and studied. However, most receptor studies were performed on non-human cells. Combining our reporter gene-tagged adenovirus library with an in vitro human gene knockout model, we performed a systematic analysis of receptor usage comparing different adenoviruses side-by-side. The CRISPR/Cas9 system was used to knockout CD46 and CAR in the human lung epithelial carcinoma cell line A549. Knockout cells were infected with 22 luciferase-expressing adenoviruses derived from adenovirus species B, C, D and E. HAdV-B16, -B21 and -B50 from species B1 as well as HAdV-B34 and -B35 were found to be CD46-dependent. HAdV-C5 and HAdV-E4 from species E were found to be CAR-dependent. Regarding cell entry of HAdV-B3 and -B14 and all species D viruses, both CAR and CD46 play a role, and here, other receptors or attachment structures may also be important since transductions were reduced but not completely inhibited. The established human knockout cell model enables the identification of the most applicable adenovirus types for gene therapy and to further understand adenovirus infection biology.

Molecular and Clinical Characterization of Human Adenovirus E4-Associated Conjunctivitis

PURPOSE

To determine the characteristics of conjunctivitis associated with human adenovirus E4 (AdV E4).

METHODS

Samples and outcomes from 500 patients with conjunctivitis were obtained from the NVC-422 randomized controlled clinical trial comparing auriclosene to placebo. Molecular typing identified 36 cases associated with AdV E4. Signs and symptoms at presentation and at the day 18 endpoint were compared with the larger cohort of 262 subjects with conjunctivitis caused by due to AdV D8. Full viral genomes of 22 AdV E4 isolates were reconstructed.

RESULTS

AdV E4 was the most frequently identified adenoviral type in conjunctivitis cases from the United States. Signs and symptoms at presentation were comparable to those associated with AdV D8. Viral load at presentation was comparable between groups but resolution was more rapid in the AdV E4 group. Clinical signs were fully resolved by day 18 in 26 of 36 (72%) patients with AdV E4. Subepithelial infiltrates developed in 12 of 36 (33%) patients with AdV E4 compared with 98 of 215 (45%) patients with AdV D8 (P = .0001). One hundred twenty-four polymorphisms were observed among 22 whole viral genome sequences, which clustered into 3 clades. Patients in each clade developed subepithelial infiltrates. Neither single nucleotide polymorphism analysis nor machine learning approaches identified specific sequence features predictive of presenting signs or outcome.

CONCLUSIONS

AdV E4 conjunctivitis may be indistinguishable at presentation from AdV D8-associated disease. Resolution of viral load for AdV E4 appears more rapid than for AdV D8, and the risk for subepithelial infiltrates appears lower. Multiple substrains of AdV E4 are in circulation but all appeared equivalently pathogenic for conjunctivitis. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Adenovirus: Epidemiology, Global Spread of Novel Types, and Approach to Treatment

Adenoviruses (AdVs) are DNA viruses that typically cause mild infections involving the upper or lower respiratory tract, gastrointestinal tract, or conjunctiva. Rare manifestations of AdV infections include hemorrhagic cystitis, hepatitis, hemorrhagic colitis, pancreatitis, nephritis, or meningoencephalitis. AdV infections are more common in young children, due to lack of humoral immunity. Epidemics of AdV infection may occur in healthy children or adults in closed or crowded settings (particularly military recruits). The vast majority of cases are self-limited. However, the clinical spectrum is broad and fatalities may occur. Dissemination is more likely in patients with impaired immunity (e.g., organ transplant recipients, human immunodeficiency virus infection). Fatality rates for untreated severe AdV pneumonia or disseminated disease may exceed 50%. More than 100 genotypes and 52 serotypes of AdV have been identified and classified into seven species designated HAdV-A through -G. Different types display different tissue tropisms that correlate with clinical manifestations of infection. The predominant types circulating at a given time differ among countries or regions, and change over time. Transmission of novel strains between countries or across continents and replacement of dominant viruses by new strains may occur. Treatment of AdV infections is controversial, as prospective, randomized therapeutic trials have not been done. Cidofovir has been the drug of choice for severe AdV infections, but not all patients require treatment. Live oral vaccines are highly efficacious in reducing the risk of respiratory AdV infection and are in routine use in the military in the United States but currently are not available to civilians.

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.

Detection of adenovirus hepatitis and acute liver failure in allogeneic hematopoietic stem cell transplant patients

Human adenovirus (HAdV) is an important cause of the common cold and epidemic keratoconjunctivitis in immunocompetent individuals. In immunocompromised patients, HAdV can sometimes cause severe infection such as cystitis, gastroenteritis, pneumonia, encephalitis, hepatitis, or disseminated disease, resulting in significant morbidity and also mortality. In particular, severe cases have been reported in patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Indeed HAdV has been recognized as a pathogen that requires careful monitoring in allo-HSCT patients. While HAdV hepatitis leading to severe acute liver failure is rare, such liver failure progresses rapidly and is often fatal. Unfortunately, HAdV hepatitis has few characteristic symptoms and physical findings, which makes it difficult to promptly confirm and start treatment. We report here four cases of HAdV hepatitis after allo-HSCT and their autopsy findings.

Recent advances in the detection of respiratory virus infection in humans

Respiratory tract viral infection caused by viruses or bacteria is one of the most common diseases in human worldwide, while those caused by emerging viruses, such as the novel coronavirus, 2019‐nCoV that caused the pneumonia outbreak in Wuhan, China most recently, have posed great threats to global public health. Identification of the causative viral pathogens of respiratory tract viral infections is important to select an appropriate treatment, save people's lives, stop the epidemics, and avoid unnecessary use of antibiotics. Conventional diagnostic tests, such as the assays for rapid detection of antiviral antibodies or viral antigens, are widely used in many clinical laboratories. With the development of modern technologies, new diagnostic strategies, including multiplex nucleic acid amplification and microarray‐based assays, are emerging. This review summarizes currently available and novel emerging diagnostic methods for the detection of common respiratory viruses, such as influenza virus, human respiratory syncytial virus, coronavirus, human adenovirus, and human rhinovirus. Multiplex assays for simultaneous detection of multiple respiratory viruses are also described. It is anticipated that such data will assist researchers and clinicians to develop appropriate diagnostic strategies for timely and effective detection of respiratory virus infections.

Respiratory tract viral infection including 2019‐nCoV poses great threats worldwide. Currently available and novel emerging diagnostic methods are summarized for several common respiratory viruses, including influenza virus, human respiratory syncytial virus, coronavirus, human adenovirus and human rhinovirus. Multiplex assays for simultaneous detection of multiple respiratory viruses are also described. This review is aimed to assist researchers and clinicians to develop timely and effective diagnostic strategies to detect respiratory virus infections.

Severe acute respiratory distress syndrome (ARDS) induced by human adenovirus B21: Report on 2 cases and literature review

Severe pneumonia and ARDS caused by human adenovirus B21 infections (HAdV-B21) is a rare, but a devastating disease with rapid progression to multiorgan failure and death. However, only a few cases were reported so far.

Infections appear associated with increased disease severity and higher mortality in infected critically ill patients. Possible factors contributing to infection are underlying psychiatric disease resulting in institutionalization of respective patients, and polytoxicomania. Controlled data on the therapy of severe adenovirus infections are lacking and remains experimental.

In conclusion, data on HAdV-B21 infections causing severe pneumonia or ARDS are scarce. Controlled clinical trials on the therapy of adenovirus pneumonia are non existent and thus there is no established therapy so far. ICU physicians should be aware of this potentially devastating disease and further studies are needed.

Human adenovirus in nasopharyngeal and blood samples from children with and without respiratory tract infections

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Positive HAdV culture and high levels of HAdV DNA >10⁶ copies/mL in NPAs were strongly associated with RTI in hospitalized children.

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Co-detection of other viruses was a very common phenomenon in children with HAdV DNA positive NPAs.

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Qualitative PCR detection of HAdV DNA in NPAs was not useful for diagnostic purposes.

Background

Human adenovirus (HAdV) is a double-stranded DNA virus associated with respiratory tract infections (RTI) in children. Using polymerase chain reaction (PCR) tests, HAdV often is detected together with other virus species, even in healthy controls.

Objectives

The aim of this study was to compare molecular detection of HAdV with culture, and to examine the associations of various methods to RTI.

Study design

Nasopharyngeal aspirates (NPA) were collected from 4319 children admitted with RTI and from 361 controls. The NPAs were examined for 23 viral and bacterial pathogens, using inhouse real-time PCR-assays based on TaqMan probes, in addition to bacterial and viral culture. HAdV concentration was evaluated semi-quantitatively from the Ct-value and quantitatively by use of ADENOVIRUS R-gene®.

Results

HAdV-DNA was detected in 6.1% patient samples and in 10.5% controls (p< 0.001). Compared to controls, patients had an OR of 3.8 (95% CI 1.4–10.3) for mono-detection of HAdV DNA, and an OR of 5.1 (95% CI 2.0–13.4) for HAdV-positive samples grew adenovirus by culture. HAdV DNA loads from children with RTI consisted of two clusters: one cluster with high viral loads (Ct < 30 and >106 copies/ml) and one cluster with low viral loads, whereas among the controls, nearly all had low viral loads (OR 7.8, 95% CI 2.2–27.1). In 61 available plasma samples, 16.4% were positive for HAdV DNA, all were from patients.

Conclusion

The detection of HAdV DNA per se by qualitative PCR is not useful as a diagnostic test. Detection of HAdV by use of viral culture and a high viral HAdV DNA load are the two methods most strongly associated with RTI in children.

A multigene typing system for human adenoviruses reveals a new genotype in a collection of Swedish clinical isolates

Human adenoviruses (HAdVs) are common pathogens that can cause respiratory, gastrointestinal, urogenital, and ocular infections. They are divided into seven species containing 85 genotypes. Straightforward typing systems might help epidemiological investigations. As homologous recombination frequently shapes the evolution of HAdVs, information on a single gene is seldom sufficient to allow accurate and precise typing, and complete genome-based methods are recommended. Even so, complete genome analyses are not always easy to perform for practical reasons, and in such cases a multigene system can provide considerably more information about the strain under investigation than single-gene-based methods. Here we present a rapid, generic, multigene typing system for HAdVs based on three main deterministic regions of these viruses. Three PCR systems were used to amplify the genes encoding the DNA polymerase, the penton base hypervariable Arg-Gly-Asp-containing loop, and the hexon loop 1 (hypervariable region 1-6). Using this system, we typed 281 clinical isolates, detected members of six out of seven HAdV species (Human mastadenovirus A-F), and could also detect not only divergent strains of established types but also a new recombinant strain with a previously unpublished combination of adenovirus genomes. This strain was accepted by the Human Adenovirus Working Group as a novel genotype: HAdV-86. Seven strains that could not be typed with sufficient accuracy were also investigated using a PCR based on part of the fiber gene. By analysis of corresponding sequences of the 86 known HAdV genotypes, we determined that the proposed typing system should be able to distinguish all non-recombinant types, and with additional fiber information, all known HAdV genotypes.

Evaluation of a human adenovirus viral load assay using the Altona RealStar® PCR test

This study evaluated the performance of the Altona Diagnostics RealStar® Adenovirus Research Use Only (RUO) real-time PCR reagents for HAdV quantitation in plasma samples from immunodeficient patients. The assay was linear from 2.30-9.17 log₁₀ copies/mL (coefficient of determination; R²=0.998) with limits of detection and quantification of 2.19 log₁₀ and 2.30 log₁₀ copies/mL (>95% positivity rate), respectively. Assay precision was highly reproducible with coefficients of variance ranging from 0% to 4.7%. A comparison of 66 matched samples showed good agreement (R²=0.845) between the Altona and the reference laboratory assay, with an average negative bias (-0.24 log₁₀ copies/mL). Genotyping analysis demonstrated that HAdV species B and C accounted for 77% of the positive samples. A significant (≥0.9 log₁₀) difference in quantitation between both tests was found for three HAdV types (HAdV types A12, B14 and F41). In conclusion, the Altona RealStar® test is a reliable and sensitive assay for HAdV DNA quantitation.

Three novel, multiple recombinant types of species of human mastadenovirus D (HAdV-D 73, 74 & 75) isolated from diarrhoeal faeces of immunocompromised patients

Species D is the largest of the seven species of human mastadenoviruses (HAdV), but few of its multiple types are associated with asevere disease, e.g. epidemic keratoconjunctivitis. Many other types are hardly ever associated with significant diseases in immunocompetent patients, but have been isolated from the diarrhoeal faeces of terminal AIDS patients suggesting their role as opportunistic pathogens. Three novel HAdV-D strains were isolated from the faeces of three immunocompromised adult patients (clinical diagnoses: lymphoma, myelodysplastic syndrome and AIDS CDC3B, respectively). These strains were not typeable by imputed serology of the hexon and fibre gene and therefore complete genomic sequences were generated by next-generation sequencing (NGS). All three strains were multiple recombinants and fulfilled the criteria for designation as types 73, 74 and 75 with the penton/hexon/fibre genotype codes P67H45F27, P70H74F51 and P75H26F29, respectively. A novel genomic backbone and also a novel hexon neutralization epitope sequence were discovered in type 74, and a novel penton sequence in type 75. At the complete genome level, types 73, 74 and 75 were closely related neither to each other nor to type 70, which was previously isolated in the same region. However, these four HAdV-D types were closely related to each other in single genes and gene regions, e.g. penton, E1 and E4 due to recombination events in their phylogeny. In conclusion, regional co-circulation of opportunistic HAdV-D types facilitated co- and super-infections, which are essential for homologous recombination, and thus resulted in the evolution of novel genotypes by lateral gene transfer.

The complete genome sequence of human adenovirus 84, a highly recombinant new Human mastadenovirus D type with a unique fiber gene

A novel human adenovirus was isolated from a pediatric case of acute respiratory disease in Panama City, Panama in 2011. The clinical isolate was initially identified as an intertypic recombinant based on hexon and fiber gene sequencing. Based on the analysis of its complete genome sequence, the novel complex recombinant Human mastadenovirus D (HAdV-D) strain was classified into a new HAdV type: HAdV-84, and it was designated Adenovirus D human/PAN/P309886/2011/84[P43H17F84]. HAdV-D types possess usually an ocular or gastrointestinal tropism, and respiratory association is scarcely reported. The virus has a novel fiber type, most closely related to, but still clearly distant from that of HAdV-36. The predicted fiber is hypothesised to bind sialic acid with lower affinity compared to HAdV-37. Bioinformatic analysis of the complete genomic sequence of HAdV-84 revealed multiple homologous recombination events and provided deeper insight into HAdV evolution.

Rapid Adenovirus typing method for species identification

Adenoviruses are characterized by a large variability, reflected by their classification in species A to G. Certain species, eg A and C, could be associated with increased clinical severity, both in immunocompetent and immunocompromised hosts suggesting that in some instances species identification provides clinically relevant information. Here we designed a novel "pVI rapid typing method" to obtain quick, simple and cost effective species assignment for Adenoviruses, thanks to combined fusion temperature (Tm) and amplicon size analysis. Rapid typing results were compared to Sanger sequencing in the hexon gene for 140 Adenovirus-positive clinical samples included in the Typadeno study. Species A and C could be identified with a 100% positive predictive value, thus confirming the value of this simple typing method.

Molecular phylogeny of a novel human adenovirus type 8 strain causing a prolonged, multi-state keratoconjunctivitis epidemic in Germany

The German infectious disease surveillance system revealed an increase of epidemic keratoconjunctivitis (EKC) from an average of 320 cases/year (2001 to 2010) up to 2146 and 1986 cases in 2012 and 2013, respectively. From November 2011 until December 2013 (epidemic period) 85% of typed isolates were human adenovirus type 8 (HAdV-D8), whereas only low level circulation (19%) of HAdV-D8 was observed outside the epidemic period. In order to investigate whether a novel monophyletic HAdV-D8 strain prevailed during the epidemic period, complete genomic sequences of 23 HAdV-D8 isolates were generated by deep sequencing and analyzed phylogenetically. For comparison, eight HAdV-D8 isolates from outside the epidemic period were sequenced. HAdV-D8 isolates of the epidemic period had a very high sequence identity of at least 99.9% and formed a monophyletic cluster with two subclusters. A single outlier was closely related to HAdV-D8 strains isolated prior to the epidemic period. Circulation of the epidemic strain was detected as early as 2010 but not after the epidemic period in 2014. In conclusion, molecular phylogeny of complete genomic sequences proved a monophyletic HAdV-D8 epidemic. However, co-circulation of other HAdV types as well as better reporting may have contributed to the huge increase of reported cases.

Adenovirus: Epidemiology, Global Spread of Novel Serotypes, and Advances in Treatment and Prevention

Adenoviruses (AdVs) are DNA viruses that typically cause mild infections involving the upper or lower respiratory tract, gastrointestinal tract, or conjunctiva. Rare manifestations of AdV infections include hemorrhagic cystitis, hepatitis, hemorrhagic colitis, pancreatitis, nephritis, or meningoencephalitis. AdV infections are more common in young children, due to lack of humoral immunity. Epidemics of AdV infection may occur in healthy children or adults in closed or crowded settings (particularly military recruits). The disease is more severe and dissemination is more likely in patients with impaired immunity (e.g., organ transplant recipients, human immunodeficiency virus infection). Fatality rates for untreated severe AdV pneumonia or disseminated disease may exceed 50%. More than 50 serotypes of AdV have been identified. Different serotypes display different tissue tropisms that correlate with clinical manifestations of infection. The predominant serotypes circulating at a given time differ among countries or regions, and change over time. Transmission of novel strains between countries or across continents and replacement of dominant viruses by new strains may occur. Treatment of AdV infections is controversial, as prospective, randomized therapeutic trials have not been conducted. Cidofovir is the drug of choice for severe AdV infections, but not all patients require treatment. Live oral vaccines are highly efficacious in reducing the risk of respiratory AdV infection and are in routine use in the military in the United States, but currently are not available to civilians.

Quantitative real-time PCR assays for detection and type-specific identification of the endemic species C human adenoviruses

Human adenoviruses (HAdVs) are medically important respiratory pathogens. Among the 7 recognized species (A-G), species C HAdVs (serotypes 1, 2, 5 and 6) are globally endemic and infect most people early in life. Species C HAdV infections are most often subclinical or mild and can lead to persistent shedding from the gastrointestinal and upper respiratory tracts. They can also cause severe disseminated disease in newborn and immunocompromised persons, where rapid and quantitative detection and identification of the virus would help guide therapeutic intervention. To this end, we developed quantitative type-specific real-time PCR (qPCR) assays for HAdV-1, -2, -5 and -6 targeting the HAdV hexon gene. All type-specific qPCR assays reproducibly detected as few as 5 copies/reaction of quantified hexon recombinant plasmids with a linear dynamic range of 8 log units (5-5×10⁷ copies). No non-specific amplifications were observed with concentrated nucleic acid from other HAdV types or other common respiratory pathogens. Of 199 previously typed HAdV field isolates and positive clinical specimens, all were detected and correctly identified to type by the qPCR assays; 10 samples had 2 HAdV types and 1 sample had 3 types identified which were confirmed by amplicon sequencing. The species C HAdV qPCR assays permit rapid, sensitive, specific and quantitative detection and identification of four recognized endemic HAdVs. Together with our previously developed qPCR assays for the epidemic respiratory HAdVs, these assays provide a convenient alternative to classical typing methods.

Adenovirus infections in immunocompetent and immunocompromised patients

Human adenoviruses (HAdVs) are an important cause of infections in both immunocompetent and immunocompromised individuals, and they continue to provide clinical challenges pertaining to diagnostics and treatment. The growing number of HAdV types identified by genomic analysis, as well as the improved understanding of the sites of viral persistence and reactivation, requires continuous adaptions of diagnostic approaches to facilitate timely detection and monitoring of HAdV infections. In view of the clinical relevance of life-threatening HAdV diseases in the immunocompromised setting, there is an urgent need for highly effective treatment modalities lacking major side effects. The present review summarizes the recent progress in the understanding and management of HAdV infections.

Prevalence and molecular characterisation of human adenovirus in diarrhoeic children in Tanzania; a case control study

BACKGROUND

Human adenovirus (HAdV) causes acute diarrhoea sporadically, as well as in outbreaks. Understanding the prevalence and types of HAdV in diarrhoea is important for control and preventive measures, especially in the African region where there is a high burden of diarrhoeal disease. The present study assessed the prevalence, molecular characteristics, seasonality and associated clinical features of HAdV infection Tanzanian children below two years of age with and without diarrhoea between 2010-2011.

METHODS

Stool specimens, demographic and clinical information were collected in 690 cases and 545 controls. All stool samples were screened for HAdV-antigen using ELISA. Positive samples subsequently underwent real-time PCR and sequencing for molecular typing.

RESULTS

HAdV was detected in 37 children, corresponding to a prevalence of 3.5% (24/690) in diarrhoeic and 2.4% (13/545) in non-diarrhoeic children (P > 0.05). Among HAdV-infected children, the median age was significantly lower in diarrhoeic than in non-diarrhoeic children (10 vs. 14 months, P˂0.001). More than half of HAdV infected (54.2%) were dehydrated as compared to diarrhoeic children without HAdV (45.8%, P = 0.01). The proportion of the enteric HAdV type 40/41 in diarrhoeic and non-diarrhoeic children was (50.0%, 12/24) and (46.2%, 6/13) respectively. Other HAdV types detected were; 1, 2, 7, 18, 19 and 31. The prevalence of adenovirus was not significantly different between rainy and dry seasons. HAdV was not detected in the 33 known HIV positive children. There was no significant association between HAdV infection and gender, nutritional status of the child and parent educational level.

CONCLUSION

The present study provides further evidence of the contribution of adenovirus in causing gastroenteritis in young children, with symptomatic infection being significantly more prevalent in children below one year. We found similar prevalence of adenovirus in non-diarrhoeic children and in diarrhoeic children. This first report on molecular epidemiology of human adenovirus in Tanzania observed diversity of HAdV types that circulate the study setting. The study findings suggest that HAdV is not an important cause of diarrhoea in young HIV-positive children.

Identification of a novel intertypic recombinant species D human adenovirus in a pediatric stem cell transplant recipient

BACKGROUND

Human adenoviruses (HAdV) are known opportunistic pathogens in hematopoietic stem cell transplant (SCT) recipients. The detection of HAdV infection in children after SCT has been implicated as a determinant of poor outcome but specific associations between HAdV species or individual HAdV types and disease are poorly understood.

OBJECTIVES

Characterization of a HAdV-D strain isolated from multiple clinical specimens of an 11-year-old female recipient of a matched unrelated donor peripheral SCT for T-cell lymphoma and case report.

STUDY DESIGN

Archived HAdV PCR-positive plasma, urine, and stool specimens were processed for virus isolation and detailed molecular typing. Complete genomic sequencing was carried out on 2 isolates.

RESULTS

The patient tested positive for HAdV DNA by real-time PCR of a stool specimen at 44 days after initiation of a SCT conditioning regimen. In the subsequent 3 months, HAdV was detected in plasma, urine and stool specimens in association with symptoms of gastroenteritis and hemorrhagic cystitis. A novel HAdV-D with a HAdV20-like hexon gene was isolated from both urine and stool specimens. All isolates yielded identical restriction profiles with endonucleases BamHI, BglII, BstEII, HindIII, PstI and SmaI. Analysis of 2 complete genomic sequences further identified the virus as a novel intertypic recombinant HAdV-D (P20/H20/F42) closely related to HAdV42.

CONCLUSIONS

This case highlights the identification of a previously unknown HAdV-D from an immunocompromised host. In this patient, the course of adenovirus infection is compatible with reactivation of a latent virus or a primary opportunistic infection. Adenoviremia in this patient resolved without definitive adenovirus-directed antiviral therapy.

Tracking novel adenovirus in environmental and human clinical samples: no evidence of endemic human adenovirus type 58 circulation in Córdoba city, Argentina

In recent years, several types of human adenovirus (HAdV) have arisen from the recombination between two or more previously known HAdV types, but their epidemiology is poorly understood. In this study, we investigated the circulation of HAdV-58, a recently described HAdV isolated from an HIV-positive patient in Córdoba city, Argentina. For this purpose, a 30-month survey was conducted to study the presence of this type of adenovirus in sewage samples collected at the inlet from a wastewater treatment plant in Córdoba city, Argentina. Complementarily, the virus was sought in stools of HIV-positive patients. Although HAdVs were detected in human stool samples and in a high percentage of sewage samples, no evidence of HAdV-58 circulation was detected. We suggest that there is no endemic circulation of HAdV-58 in the geographical local area. The trend is that the number of identified HAdVs increases over time. In this context, understanding the current circulating HAdVs may be biologically relevant.

Genome stability of adenovirus types 3 and 7 during a simultaneous outbreak in Greater Manchester, UK

A total of 96 isolates of species B adenovirus collected in Greater Manchester, UK and typed previously by serum neutralization were analyzed in five genome regions. Of these, 62 isolates were HAdV-B3 and HAdV-B7 collected during a simultaneous 15 months outbreak. The rest of the isolates were HAdV-B types 3 and 7 and other species B adenovirus types collected in different years following the outbreak. The phylogenetic analysis results of all the isolates in the structural regions hexon L2, penton, and fiber knob were found to be consistent and no mismatches were observed. Most of the isolates in the DNA polymerase and E1A regions had the same clustering patterns as the structural regions. However, one HAdV-B7 and one HAdV-B11 isolate changed their clustering patterns in the DNA polymerase region. In addition, HAdV-B16 isolates changed their clustering patterns in both DNA polymerase and E1A regions. The changes of the clustering patterns of some isolates is more likely related to natural variations rather than recombination which indicate that species B adenovirus genome is stable even when different types are circulating in a limited geographical area simultaneously.

Waterborne human pathogenic viruses of public health concern

In recent years, the impending impact of waterborne pathogens on human health has become a growing concern. Drinking water and recreational exposure to polluted water have shown to be linked to viral infections, since viruses are shed in extremely high numbers in the faeces and vomit of infected individuals and are routinely introduced into the water environment. All of the identified pathogenic viruses that pose a significant public health threat in the water environment are transmitted via the faecal-oral route. This group, are collectively known as enteric viruses, and their possible health effects include gastroenteritis, paralysis, meningitis, hepatitis, respiratory illness and diarrhoea. This review addresses both past and recent investigations into viral contamination of surface waters, with emphasis on six types of potential waterborne human pathogenic viruses. In addition, the viral associated illnesses are outlined with reference to their pathogenesis and routes of transmission.

Patient, virus, and treatment-related risk factors in pediatric adenovirus infection after stem cell transplantation: results of a routine monitoring program

Human adenovirus (HAdV) infection after hematopoietic stem cell transplantation (HSCT) is associated with significant morbidity and mortality in children. The optimal surveillance and treatment strategies are under discussion. Here, we present data from 238 consecutive pediatric allogeneic HSCT recipients who underwent transplantation in a single center who were included in a prospective, weekly HAdV DNAemia monitoring program by quantitative PCR. HAdV loads >1000 copies/mL were detected in 15.5% of all patients. Despite a low mortality directly attributed to HAdV infection (2 patients, 0.84%), blood HAdV loads >10,000 copies/mL (6.7% of all patients) were significant and independent risk factors for poor survival. We searched for patient, virus, and treatment-related risk factors of HAdV DNAemia and disease. Detection of HAdV in blood before day 50 post transplantation was a major independent risk factor for the development of blood HAdV loads >10,000 copies/mL. HAdV typing revealed A31, C1, and C2 as the predominant pathogens among several other HAdV strains with type C species detected in most patients with severe HAdV disease. Stool HAdV loads were prospectively monitored in 111 patients and correlated with but did not significantly precede detection in blood. Treatment with cidofovir led to stable or reduced viral load in 70% of patients with blood HAdV loads >1000 copies/mL. Thus, early occurrence of HAdV-DNA in blood of pediatric HSCT recipients predisposes for development of high viral loads. Control of HAdV infections was attempted by preemptive cidofovir treatment of patients with high blood HAdV loads or with symptomatic organ infections and correlated with low HAdV-attributed mortality.

Type dependent patterns of human adenovirus persistence in human T-lymphocyte cell lines

Disseminated adenovirus infections cause significant mortality in stem cell transplanted patients and are suspected to originate from asymptomatic adenovirus persistence ("latency") in lymphocytes. The infection of three human T-lymphocyte lines (Jurkat, PM1, and CEM) with human adenovirus types of species A (HAdV-A31), B (HAdV-B3, -B11), and C (HAdV-C2, -C5) was investigated for 150 days in order to establish in vitro models for adenovirus persistence. HAdV-C5 persisted with continuous production of infectious virus progeny (about 10(7) TCID50 /ml) in PM1 cells. More than 100 copies of HAdV-C5-DNA per cell were detected by real-time PCR but hexon immunostaining showed that only 7.5% of the cells were infected ("carrier state infection"). Coxsackie and adenovirus receptor (CAR) expression was decreased in comparison to mock infected cultures suggesting selection of a semi-permissive subpopulation of PM-1 cells. By contrast, latency of HAdV-DNA (10(-3) -10(-4)  copies/cell) without production of infectious virus progeny was observed in HAdV-C2 infection of PM1 and Jurkat, HAdV-A31 infection of PM1, and HAdV-B3 infection of Jurkat cells. In addition, transcription of E1A, DNA polymerase and hexon mRNA was not detected by RT-PCR suggesting an equivalent of clinical "HAdV latency." Persistence of HAdV-DNA was not observed in abortive infections of PM1 cells with HAdV-B3 and -B11 and in productive, lytical infections of Jurkat cells with HAdV-C5, HAdV-B11, and HAdV-A31. In conclusion, lytic and persistent infections with and without production of infectious virus were observed depending on the type of adenovirus. Genetic determinants for viral persistence may be investigated using these newly established infection models.

Molecular and serological characterization of species B2 adenovirus strains isolated from children hospitalized with acute respiratory disease in Buenos Aires, Argentina

BACKGROUND

Between September 2000 and November 2005, approximately 10% of the retrospectively examined human adenovirus (HAdV)-positive pediatric cases of acute respiratory disease (ARD) requiring hospitalization at the Hospital Nacional de Pediatria Juan P. Garrahan in Buenos Aires, Argentina, were found to have a HAdV-B2 infection.

OBJECTIVE

To characterize genetically and antigenically the HAdV-B2 virus isolates.

STUDY DESIGN

Restriction enzyme analysis (REA), hexon and fiber gene sequencing and virus neutralization assays (VN) were carried out on 8 HAdV-B2 respiratory virus isolates.

RESULTS

REA showed that the 8 examined HAdV-B2 virus isolates were HAdV11, belonging to two genomic variants: HAdV11a and a BclI variant of HAdV11c which we designated 11c4. Molecular analysis of the hexon genes showed that both REA variants had a HAdV11-like hexon gene. Confirming previous reports, the 7 HAdV11a virus isolates were found to have HAdV14-like fiber genes and therefore are HAdV H11/F14. The fiber gene of the HAdV11c4 virus isolates most closely resembled that of various strains of HAdV7. In VN assays, the 4 tested HAdV11a strains were serotyped as HAdV11-14. The HAdV11c4 strain was serotyped as HAdV11 but also showed a weak but significant reactivity with antiserum to HAdV7. Compared with the other HAdV-positive cases in our study, infection with HAdV11 caused a similarly severe disease.

CONCLUSIONS

Our results provide evidence to the long term world-wide circulation of HAdV H11/F14 as a causative agent of ARD. Combined, our molecular and serology data support the rationale to base the molecular typing and designation of recombinant viruses on the sequences of the hexon and fiber genes.

Genotyping of clinically relevant human adenoviruses by array-in-well hybridization assay

A robust oligonucleotide array-in-well hybridization assay using novel up-converting phosphor reporter technology was applied for genotyping clinically relevant human adenovirus types. A total of 231 adenovirus-positive respiratory, ocular swab, stool and other specimens from 219 patients collected between April 2010 and April 2011 were included in the study. After a real-time PCR amplification targeting the adenovirus hexon gene, the array-in-well assay identified the presence of B03 (n = 122; 57.5% of patients), E04 (29; 13.7%), C02 (21; 9.9%), D37 (14; 6.6%), C01 (12; 5.7%), C05 (5; 2.4%), D19 (4; 1.9%), C06 (2; 0.9%), D08 (1; 0.5%), A31 (1; 0.5%) and F41 (1; 0.5%) genotypes among the clinical sample panel. The typing result was obtained for all specimens that could be amplified (n = 223; 97%), and specificity of the typing was confirmed by sequencing specimens representing each of the different genotypes. No hybridization signal was obtained in adenovirus-negative specimens or specimens with other viruses (n = 30). The array-in-well hybridization assay has great potential as a rapid and multiplex platform for the typing of clinically relevant human adenovirus genotypes in different specimen types.

Presence of adenovirus species C in infiltrating lymphocytes of human sarcoma

Human adenoviruses are known to persist in T-lymphocytes of tonsils, adenoids and intestinal tract. The oncogenic potential of different adenovirus types has been widely studied in rodents, in which adenovirus inoculation can induce multiple tumors such as undifferentiated sarcomas, adenocarcinomas and neuroectodermal tumors. However, the oncogenic potential of this virus has never been proven in human subjects. Using a highly sensitive broad-spectrum qRT-PCR, we have screened a set of different human sarcomas including leiomyosarcoma, liposarcoma and gastro intestinal stroma tumors. Primers binding the viral oncogene E1A and the capsid-coding gene Hexon were used to detect the presence of adenovirus DNA in tumor samples. We found that 18% of the tested leiomyosarcomas and 35% of the liposarcomas were positive for the presence of adenovirus DNA, being species C types the most frequently detected adenoviruses. However, only in one sample of the gastro intestinal stroma tumors the virus DNA could be detected. The occurrence of adenovirus in the tumor sections was confirmed by subsequent fluorescence in-situ-hybridization analysis and co-staining with the transcription factor Bcl11b gives evidence for the presence of the virus in infiltrating T-lymphocytes within the tumors. Together these data underline, for the first time, the persistence of adenovirus in T-lymphocytes infiltrated in muscular and fatty tissue tumor samples. If an impaired immune system leads to the viral persistence and reactivation of the virus is involved in additional diseases needs further investigation.

Genome sequence of a novel virus of the species human adenovirus d associated with acute gastroenteritis

A novel virus of the species human adenovirus D, HAdV-67 (P-New/H9/F25), was first isolated from diarrheal feces of six children in Dhaka City, Bangladesh. The genome of this novel virus may be composed of multiple recombinations among HAdV-9, HAdV-25, HAdV-26, HAdV-33, HAdV-46, and an unknown human adenovirus D which was an origin of HAdV-67.

Detection and molecular characterization of adenoviruses in Korean children hospitalized with acute gastroenteritis

Human adenoviruses (HAdVs) are an important cause of acute gastroenteritis in children. However, few studies on the epidemiology or types of HAdVs associated with acute gastroenteritis have been conducted in Korea. Therefore, in the present study, the incidence of HAdV in 2064 stool samples from Korean children hospitalized with acute gastroenteritis (2004-2006) was assessed and the types of viruses present determined. Polymerase chain reaction, sequencing, and phylogenic analyses revealed that 113 samples (5.5%) were HAdV-positive. While HAdVs were mainly detected during July to October, no seasonal difference between the enteric and non-enteric viruses in the incidence of HAdV was observed. HAdV-41 and HAdV-40 were found in 54 (47.8%) and 3 (2.6%) HAdV-positive samples, respectively. HAdV-3, HAdV-7, HAdV-2, HAdV-31, HAdV-4, and HAdV-37 were detected in 11 (9.7%), 5 (4.4%), 2 (1.7%), 2 (1.7%), 1 (0.8%), and 1 (0.8%) of sample(s), respectively. Thus, not only enteric, but also non-enteric, HAdVs may play an important role in acute gastroenteritis in Korean children.

Adenovirus infections in Bordeaux University Hospital 2008-2010: clinical and virological features

BACKGROUND

Transversal epidemiological data on adenovirus infections in a hospital setting, including both immuno-competent and transplanted patients, are limited and rarely contain the application of molecular virology.

OBJECTIVES

To describe the clinical characteristics and molecular epidemiology of adenovirus infections in Bordeaux University Hospital from 2008 to 2010 (clinical data, viral load and adenovirus species distribution).

STUDY DESIGN

Adenovirus DNA quantification (qPCR) and typing (sequencing of hexon and protein VI genes and protein VI polymerase chain reaction (PCR) product analysis) were applied retrospectively to 215 clinical samples from 105 adenovirus-infected patients (2008-2010, Bordeaux University Hospital). Clinical data were recovered and analysed for 73 children and 25 adults.

RESULTS

Viral loads were measured in stools, upper and lower respiratory fluids, blood, urine and digestive tract biopsies; the highest values were observed in stools and respiratory samples. Stool viral loads were comparable whatever the immune status. Adenovirus was typed in 57 patients: species Human adenovirus (HAdV) C dominated (n=36), followed by B (n=15), F (n=5) and D (n=1). We could demonstrate no association between HAdV species and load or clinical severity (observed in most patients). In the immuno-compromised, in contrast to immuno-competent patients, adenovirus infections presented no seasonal variation. Co-infections were frequent: mostly bacterial in immuno-competent children (33%) and viral in immuno-compromised people (34%).

CONCLUSIONS

The species HAdV C dominates the local ecology, in both respiratory and digestive tract infections, independently of the patient's immune status. Adenovirus infections, often associated with co-infection of bacterial or viral agents, frequently lead to severe clinical consequences in hospital patients.

Adenoviral load diagnostics by quantitative polymerase chain reaction: techniques and application

Human adenoviruses (HAdV) can cause fatal complications such as disseminated disease especially in a post-transplant setting. With conventional methods, disseminated HAdV disease could only be diagnosed with delay. Quantification of the HAdV load by real-time PCR in peripheral blood promised to solve this diagnostic dilemma. Here we review the development, applications and significance of quantitative HAdV PCR. The high genetic divergence of the 56 HAdV types was a major obstacle for developing a quantitative HAdV PCR covering all types. Several protocols focused either on a few, probably predominating types or tried to detect all known HAdV types by using a bundle of assays or a few multiplexed PCRs. Alternatively, generic quantitative real-time HAdV PCR protocols using primer and probe consensus sequences have been designed, providing considerable reduction of costs and hands-on time. Application of HAdV load testing by several studies on stem cell transplant (SCT) recipients indicated that rapidly increasing HAdV blood loads as well as high HAdV DNAemia (e.g. >10(4) copies/ml) are predictive for disseminated HAdV disease although a universal threshold value has not yet been established. HAdV load testing has been implemented for systematic screening of SCT patients permitting early diagnosis, pre-emptive treatment initiation and monitoring of antiviral therapy. However, further investigations are required to validate proposed virus load thresholds. Moreover, other applications of quantitative HAdV PCR, such as the diagnosis of localized HAdV disease, the analysis of environmental samples and monitoring of gene therapy with adenoviral vectors will be addressed in this review.

Computational analysis of two species C human adenoviruses provides evidence of a novel virus

Human adenovirus C (HAdV-C) species are a common cause of respiratory infections and can occasionally produce severe clinical manifestations. A deeper understanding of the variation and evolution in species HAdV-C is especially important since these viruses, including HAdV-C6, are used as gene delivery vectors for human gene therapy and in other biotechnological applications. Here, the full-genome analysis of the prototype HAdV-C6 and a recently identified virus provisionally termed HAdV-C57 are reported. Although the genomes of all species HAdV-C members are very similar to each other, the E3 region, hexon and fiber (ten proteins total) present a wide range of identity values at the amino acid level. Studies of these viruses in comparison to the other three HAdV-C prototypes (1, 2, and 5) comprise a comprehensive analysis of the diversity and conservation within HAdV-C species. HAdV-C6 contains a recombination event within the constant region of the hexon gene. HAdV-C57 is a recombinant virus with a fiber gene nearly identical to HAdV-C6 and a unique hexon distinguished by its loop 2 motif.

Respiratory viral infections in hematopoietic stem cell and solid organ transplant recipients

Respiratory viral infections (RVIs) are common causes of mild illness in immunocompetent children and adults with rare occurrences of significant morbidity or mortality. Complications are more common in the very young, very old, and those with underlying lung diseases. However, RVIs are increasingly recognized as a cause of morbidity and mortality in recipients of hematopoietic stem cell transplants (HSCT) and solid organ transplants (SOTs). Diagnostic techniques for respiratory syncytial virus (RSV), parainfluenza, influenza, and adenovirus have been clinically available for decades, and these infections are known to cause serious disease in transplant recipients. Modern molecular technology has now made it possible to detect other RVIs including human metapneumovirus, coronavirus, and bocavirus, and the role of these viruses in causing serious disease in transplant recipients is still being worked out. This article reviews the current information regarding epidemiology, pathogenesis, clinical presentation, diagnosis, and treatment of these infections, as well as the aspects of clinical significance of RVIs unique to HSCT or SOT.

High lethality of human adenovirus disease in adult allogeneic stem cell transplant recipients with high adenoviral blood load

BACKGROUND

Human adenoviruses (HAdV) can cause disseminated disease as a severe complication after haematopoietic stem cell transplantation (SCT) and may originate from the reactivation of latent infections. However, data about the clinical relevance of HAdV DNAaemia and disease in adults are scarce.

OBJECTIVES

To retrospectively analyse the outcome of adult allogeneic SCT recipients with high HAdV loads in peripheral blood.

STUDY DESIGN

Our diagnostic database was screened for allogeneic SCT recipients with peak HAdV DNAaemia above 1.0×10(4)copies/ml (tested by quantitative real-time PCR) and medical records were reviewed retrospectively.

RESULTS

From 1674 adult allogeneic SCT recipients 539 (32.2%) received HAdV DNAaemia testing. In twenty-seven of these HAdV blood loads above 1.0×10(4) (range: 1.6×10(4)-1.8×10(9))copies/ml were observed. Seven of these 27 succumbed to HAdV disease and their median peak HAdV DNAaemia was significantly higher than in patients without HAdV-associated death (1.0×10(8) vs. 3×10(5)copies/ml, p<0.001). T-cell depletion was a risk factor for fatal HAdV disease. HAdV of species C predominated (66.7%) and were of high virulence (6 of 7 fatal cases). HAdV of species B were observed more frequently (n=6) in our study than reported for paediatrics, indicating a different pattern of HAdV reactivation in adults.

CONCLUSIONS

The presence of several HAdV-associated deaths in adult SCT recipients with high-level HAdV DNAaemia confirmed the clinical relevance of HAdV DNAaemia testing in adults. Quantitative HAdV DNAaemia testing is a promising tool to predict the outcome of HAdV disease.

Requirements for receptor engagement during infection by adenovirus complexed with blood coagulation factor X

Human adenoviruses from multiple species bind to coagulation factor X (FX), yet the importance of this interaction in adenovirus dissemination is unknown. Upon contact with blood, vectors based on adenovirus serotype 5 (Ad5) binds to FX via the hexon protein with nanomolar affinity, leading to selective uptake of the complex into the liver and spleen. The Ad5:FX complex putatively targets heparan sulfate proteoglycans (HSPGs). The aim of this study was to elucidate the specific requirements for Ad5:FX-mediated cellular uptake in this high-affinity pathway, specifically the HSPG receptor requirements as well as the role of penton base-mediated integrin engagement in subsequent internalisation. Removal of HS sidechains by enzymatic digestion or competition with highly-sulfated heparins/heparan sulfates significantly decreased FX-mediated Ad5 cell binding in vitro and ex vivo. Removal of N-linked and, in particular, O-linked sulfate groups significantly attenuated the inhibitory capabilities of heparin, while the chemical inhibition of endogenous HSPG sulfation dose-dependently reduced FX-mediated Ad5 cellular uptake. Unlike native heparin, modified heparins lacking O- or N-linked sulfate groups were unable to inhibit Ad5 accumulation in the liver 1h after intravascular administration of adenovirus. Similar results were observed in vitro using Ad5 vectors possessing mutations ablating CAR- and/or α(v) integrin binding, demonstrating that attachment of the Ad5:FX complex to the cell surface involves HSPG sulfation. Interestingly, Ad5 vectors ablated for α(v) integrin binding showed markedly delayed cell entry, highlighting the need for an efficient post-attachment internalisation signal for optimal Ad5 uptake and transport following surface binding mediated through FX. This study therefore integrates the established model of α(v) integrin-dependent adenoviral infection with the high-affinity FX-mediated pathway. This has important implications for mechanisms that define organ targeting following contact of human adenoviruses with blood.

High prevalence of species D human adenoviruses in fecal specimens from Urban Kenyan children with diarrhea

Human adenoviruses (HAdVs) cause a wide range of clinical syndromes and are classified in seven species, A-G, comprising 52 serotypes. HAdV-A31, -F40, and -F41 have been associated with diarrhea in infants and young children. In developing countries gastroenteritis is a major cause of morbidity and mortality in children and, in comparison to rotaviruses, there are no data on the HAdVs associated with diarrhea in pediatric patients in Kenya. This study investigates the prevalence and genotypes of HAdVs in 278 stool specimens (211 diarrheal; 67 non-diarrheal) from children < or =14 years of age in urban and rural areas in Kenya. Stool specimens were screened for HAdVs using a nested polymerase chain reaction and the HAdVs genotyped by sequence analysis of a conserved hexon gene fragment. HAdVs were detected in 104/278 (37.4%) of the stool specimens: 35/43 (81.4%) of diarrheal and 10/61 (16.4%) of non-diarrheal stool specimens from children in an urban hospice; 25/94 (26.6%) of diarrheal specimens from urban children and 34/80 (42.5%) of diarrheal specimens from children in a rural area. Species D HAdVs were identified as the most prevalent HAdV species in diarrheal stool specimens from urban children comprising 18/37 (48.6%) of the strains identified. In contrast HAdV species F predominated in pediatric diarrheal specimens from the rural area, being identified in 7/16 (43.8%) of the characterized strains. This study provides valuable new data on the prevalence and distribution of HAdV genotypes in diarrheal stool specimens in Kenya and Africa, and highlights the necessity for further investigations.

Human adenoviruses in respiratory infections: sequencing of the hexon hypervariable region reveals high sequence variability

BACKGROUND

In respiratory infections, human adenoviruses (hAdV) of species B1 and C are frequently detected, but severe or even fatal disease outbreaks are predominantly caused by only few serotypes. The molecular typing of hAdV hexon sequences can help to speed up the discrimination of serotypes, thus improving on-time epidemiological examinations and patient care.

OBJECTIVES

We aimed to develop a molecular method for the rapid species B1 and C serotype identification in respiratory samples based on sequence generation of the hexon hypervariable region (HVR).

STUDY DESIGN

We developed two PCR-based genotyping systems for a generic HVR amplification and sequence determination of species B1 and C viruses. The assays were applied to hAdV prototypes and 106 samples.

RESULTS

The primer sets proved to be capable of amplifying all B1 and C serotypes. The viruses detected in clinical samples belong to serotypes 1, 2, 3, 5 and 6. The obtained sequences of serotypes 2, 3 and 5 form 2-3 phylogenetic clusters that are based on the characteristic amino acid changes within the variable HVR sites.

CONCLUSIONS

Our assay can significantly speed up the time-span needed for serotype identification and will improve epidemiological surveillance and patient care. The obtained hexon sequences of field viruses vary significantly and form multiple genetic lineages. The variability is focussed on the HVR sites and can be interpreted as the ongoing evolutionary process. Further research is needed on the hexon sequence variability of other (respiratory) hAdV serotypes.

Adenovirus infections in solid organ transplant recipients

PURPOSE OF REVIEW

Adenoviruses are emerging as important viral pathogens in solid organ transplant recipients, impacting morbidity, graft survival and even mortality. This review will discuss the current understanding of the epidemiology, diagnosis and therapy of adenovirus infection in transplant recipients.

RECENT FINDINGS

Advances in the field include the use of polymerase chain reaction in the diagnosis of adenoviral infection, a better understanding of the epidemiology, immune response and potential new therapies, including preemptive and adoptive immunotherapy strategies. Adenoviral infections appear to be common, especially in pediatric solid organ transplant. Generally well tolerated, some high-risk patients may develop disseminated disease causing graft failure, which may lead to retransplant and/or death. Antiviral therapy and immunotherapy may play a role in these patients, although prospective controlled data are not available at this time.

SUMMARY

Although new tools and a better understanding of the epidemiology, risk factors and therapies for adenovirus are beginning to materialize, prospective, controlled trials, using careful definitions, and standardized methodologies need to be performed to more fully clarify these issues in solid organ transplant recipients.

Unique sequence features of the Human adenovirus 31 complete genomic sequence are conserved in clinical isolates

Background

Human adenoviruses (HAdV) are causing a broad spectrum of diseases. One of the most severe forms of adenovirus infection is a disseminated disease resulting in significant morbidity and mortality. Several reports in recent years have identified HAdV-31 from species A (HAdV-A31) as a cause of disseminated disease in children following haematopoetic stem cell transplantation (hSCT) and liver transplantation. We sequenced and analyzed the complete genome of the HAdV-A31 prototype strain to uncover unique sequence motifs associated with its high virulence. Moreover, we sequenced coding regions known to be essential for tropism and virulence (early transcription units E1A, E3, E4, the fiber knob and the penton base) of HAdV-A31 clinical isolates from patients with disseminated disease.

Results

The genome size of HAdV-A31 is 33763 base pairs (bp) in length with a GC content of 46.36%. Nucleotide alignment to the closely related HAdV-A12 revealed an overall homology of 84.2%. The genome organization into early, intermediate and late regions is similar to HAdV-A12. Sequence analysis of the prototype strain showed unique sequence features such as an immunoglobulin-like domain in the species A specific gene product E3 CR1 beta and a potentially integrin binding RGD motif in the C-terminal region of the protein IX. These features were conserved in all analyzed clinical isolates. Overall, amino acid sequences of clinical isolates were highly conserved compared to the prototype (99.2 to 100%), but a synonymous/non synonymous ratio (S/N) of 2.36 in E3 CR1 beta suggested positive selection.

Conclusion

Unique sequence features of HAdV-A31 may enhance its ability to escape the host's immune surveillance and may facilitate a promiscuous tropism for various tissues. Moderate evolution of clinical isolates did not indicate the emergence of new HAdV-A31 subtypes in the recent years.