Genome sequences of human adenovirus 14 isolates from mild respiratory cases and a fatal pneumonia, isolated during 2006-2007 epidemics in North America

Human adenovirus lung disease: outbreaks, models of immune-response-driven acute lung injury and pandemic potential

PURPOSE OF REVIEW

An overview of epidemic, human adenovirus (HAdV) lung infections with proposed studies of the viral/host immune response interface to better understand mechanisms of immunopathogenesis, for development of improved responses to a potential HAdV pandemic.

RECENT FINDINGS

Emergent HAdV strains 7, 3, 4, 14 are the most common types associated with infection outbreaks. Recent outbreaks have revealed increased community spread, beyond epidemic group settings. The ongoing circulation of these virulent HAdV strains might allow for further HAdV adaptation, with increased HAdV spread and disease severity in the population that could theoretically result in expansion to a pandemic level.

SUMMARY

Public health screening has revealed spread of HAdV outbreak strains to the general community. Despite expanded awareness of viral respiratory diseases during the SARS-CoV-2 pandemic, there has been limited, systematic monitoring of HAdV infection in the population. The shift in clinical laboratories to a focus on molecular diagnostics and away from classical methods of viral characterization has reduced the distribution of outbreak HAdV strains to the research community to study mechanisms of pathogenesis. This change risks reduced development of new preventive and therapeutic strategies that could be needed in the event of more widespread HAdV epidemics.

Characterization of Viral miRNAs during Adenovirus 14 Infection and Their Differential Expression in the Emergent Strain Adenovirus 14p1

Human adenoviruses (HAdV) express either one or two virus-associated RNAs (VA RNAI or VA RNAII). The structure of VA RNA resembles human precursor microRNAs (pre-miRNA), and, like human pre-miRNA, VA RNA can be processed by DICER into small RNAs that resemble human miRNA. VA RNA-derived miRNA (mivaRNA) can mimic human miRNA post-transcriptional gene repression by binding to complementary sequences in the 3′ UTR of host mRNA. HAdV14 is a member of the B2 subspecies of species B adenovirus, and the emergent strain HAdV14p1 is associated with severe respiratory illness that can lead to acute respiratory distress syndrome. Utilizing small RNA sequencing, we identified four main mivaRNAs generated from the HAdV14/p1 VA RNA gene, two from each of the 5′ and 3′ regions of the terminal stem. There were temporal expression changes in the abundance of 5′ and 3′ mivaRNAs, with 3′ mivaRNAs more highly expressed early in infection and 5′ mivaRNAs more highly expressed later in infection. In addition, there are differences in expression between the emergent and reference strains, with HAdV14 expressing more mivaRNAs early during infection and HAdV14p1 having higher expression later during infection. HAdV14/p1 mivaRNAs were also shown to repress gene expression in a luciferase gene reporter system. Our results raise the question as to whether differential expression of mivaRNAs during HAdV14p1 infection could play a role in the increased pathogenesis associated with the emergent strain.

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.

Live Oral Adenovirus Type 4 and Type 7 Vaccine Induces Durable Antibody Response

Human adenoviruses (AdV) are mostly associated with minimal pathology. However, more severe respiratory tract infections and acute respiratory diseases, most often caused by AdV-4 and AdV-7, have been reported. The only licensed vaccine in the United States, live oral AdV-4 and AdV-7 vaccine, is indicated for use in the military, nearly exclusively in recruit populations. The excellent safety profile and prominent antibody response of the vaccine is well established by placebo-controlled clinical trials, while, long-term immunity of vaccination has not been studied. Serum samples collected over 6 years from subjects co-administered live oral AdV-4 and AdV-7 vaccine in 2011 were evaluated to determine the duration of the antibody response. Group geometric mean titers (GMT) at 6 years post vaccination compared to previous years evaluated were not significantly different for either AdV-4 or AdV-7 vaccine components. There were no subjects that demonstrated waning neutralization antibody (NAb) titers against AdV-4 and less than 5% of subjects against AdV-7. Interestingly, there were subjects that had a four-fold increase in NAb titers against either AdV-4 or AdV-7, at various time points post vaccination, suggesting either homotypic or heterotypic re-exposure. This investigation provided strong evidence that the live oral AdV-4 and AdV-7 vaccine induced long-term immunity to protect from AdV-4 and AdV-7 infections.

Adenovirus 14p1 Immunopathogenesis during Lung Infection in the Syrian Hamster

Adenovirus (Ad) infections are usually mild and self-limited, with minimal inflammatory responses. During worldwide outbreaks, Ad14p1, an emerging Ad14 variant, has caused severe pulmonary disease, including acute respiratory distress syndrome (ARDS). This increased pathogenicity of Ad14p1 is not completely understood. In initial studies, we observed that infection of Syrian hamsters with Ad14p1 can cause a patchy bronchopneumonia, with an increased intensity of inflammation, compared to wild type Ad14 infection. The current study compared the dynamics of the immunopathogenesis of Ad14 and Ad14p1 infection of hamster lungs through the first two weeks after infection. Little difference was seen in infection-induced inflammation at day 1. Beginning at day 3, Ad14p1-infected hamsters showed marked inflammation that continued through to day 7. The inflammation began to resolve by day 10 but was still detectable at day 14. In contrast, Ad14-infected hamsters showed little inflammation during the 14-day period of observation. Inflammatory cell type analysis revealed that, at day 1, hamsters infected with either virus had predominantly neutrophil infiltration that began to resolve by day 3. However, at day 5, Ad14p1-infected hamsters had a second wave of neutrophil infiltration that was accompanied by edema which persisted to a variable extent through to day 10. These differences were not explained by an increased Ad14p1 replication rate, compared with Ad14 in vitro, but there was prolonged persistence of Ad14p1 in hamster lungs. There were differences in lung tissue cytokine and chemokine responses to Ad14p1 vs. Ad14 infection that might account for the increased leukocyte infiltrates in Ad14p1-infected hamsters. This animal model characterization provides the basis for future translational studies of the viral genetic mechanisms that control the increased immunopathogenesis of the emergent, Ad14p1 strain.

Rapid Construction of a Replication-Competent Infectious Clone of Human Adenovirus Type 14 by Gibson Assembly

In 1955, Human adenovirus type 14 (HAdV-B14p) was firstly identified in a military trainee diagnosed as acute respiratory disease (ARD) in the Netherlands. Fifty years later, a genomic variant, HAdV-B14p1, re-emerged in the U.S. and caused large and fatal ARD outbreaks. Subsequently, more and more ARD outbreaks occurred in Canada, the UK, Ireland, and China, in both military and civil settings. To generate a tool for the efficient characterization of this new genomic variant, a full-length infectious genomic clone of HAdV-B14 was successfully constructed using one-step Gibson Assembly method in this study. Firstly, the full genome of HAdV-B14p1 strain GZ01, the first HAdV-B14 isolate in China, was assembled into pBR322 plasmid by Gibson Assembly. The pBRAdV14 plasmid, generated by Gibson Assembly, was analyzed and verified by PCR, restriction enzymes digestion and the sequencing. Secondly, viruses were rescued from pBRAdV14-transfected A549 cells. The integrity of the rescued viruses was identified by restriction enzyme analysis. The complete sequence of the infectious clone was further sequenced. No mutation was found in the infectious clone during the construction when compared with the parental virus and pBR322 sequences. The direct immunofluorescence assay indicated the expression of the hexon protein. Finally, typical virions were observed; the one-step growth curves further showed that the DNA replication and viral reproduction efficiency of pBRAd14 derived viruses was similar with that of wild-type HAdV-B14 strain. The successful construction of the replication-competent infectious clone of pBRAdV14 facilitates the development of vaccine and antiviral drugs against HAdV-B14, as well as provides a novel strategy for rapid construction of infectious viral clones for other large-genome DNA viruses.

Comparative genomic analysis of two emergent human adenovirus type 14 respiratory pathogen isolates in China reveals similar yet divergent genomes

Human adenovirus type 14 (HAdV-B14p) was originally identified as an acute respiratory disease (ARD) pathogen in The Netherlands in 1955. For approximately fifty years, few sporadic infections were observed. In 2005, HAdV-B14p1, a genomic variant, re-emerged and was associated with several large ARD outbreaks across the U.S. and, subsequently, in Canada, the U.K., Ireland, and China. This strain was associated with an unusually higher fatality rate than previously reported for both this prototype and other HAdV types in general. In China, HAdV-B14 was first observed in 2010, when two unrelated HAdV-B14-associated ARD cases were reported in Southern China (GZ01) and Northern China (BJ430), followed by three subsequent outbreaks. While comparative genomic analysis, including indel analysis, shows that the three China isolates, with whole genome data available, are similar to the de Wit prototype, all are divergent from the U.S. strain (303600; 2007). Although the genomes of strains GZ01 and BJ430 are nearly identical, as per their genome type characterization and percent identities, they are subtly divergent in their genome mutation patterns. These genomes indicate possibly two lineages of HAdV-B14 and independent introductions into China from abroad, or subsequent divergence from one; CHN2012 likely represents a separate sub-lineage. Observations of these simultaneously reported emergent strains in China add to the understanding of the circulation, epidemiology, and evolution of these HAdV pathogens, as well as provide a foundation for developing effective vaccines and public health strategies, including nationwide surveillance in anticipation of larger outbreaks with potentially higher fatality rates associated with HAdV-B14p1.

Adenovirus

Adenoviruses are a highly prevalent infection that can cause a range of clinical syndromes in immunocompromised patients, ranging from localized disease of the respiratory tract, gastrointestinal tract, or urinary tract to disseminated disease. Adenovirus infections may develop in this unique population as the result of primary infection or reactivation of latent virus. Disease can be potentially progressive with high rates of mortality in patients with pneumonia and disseminated disease. Fortunately, cidofovir and its lipid ester, brincidofovir, appear to be effective for the treatment of adenovirus, although neither is specifically approved for this indication. Adenovirus should always be considered when immunocompromised patients present with any clinical syndrome that could be compatible with adenoviral infection. Once disease is suspected, cultures or molecular testing of appropriate specimens should be obtained and blood should be sent for adenovirus polymerase chain reaction (PCR) whenever adenovirus is suspected. Monitoring of quantitative viral loads in blood is helpful in predicting response to therapy with a significant drop (>1 log) associated with a higher probability of clinical response.

[Risk factors for poor prognosis in children with severe adenovirus pneumonia]

OBJECTIVE

To investigate the risk factors for poor prognosis of severe adenovirus pneumonia (SAP) in children.

METHODS

The clinical data of 189 children with SAP were retrospectively analyzed. Univariate logistic regression analysis was performed to assess the risk factors for poor prognosis.

RESULTS

The univariate logistic regression analysis showed that the patients with hemoglobin <90 g/L, plasma albumin <30 g/L, C-reactive protein >30 mg/L, procalcitonin >10 ng/mL, alanine aminotransferase >100 U/L, or aspartate aminotransferase >100 U/L had poor prognosis (P<0.05), and that those with congenital dysplasia of the airway, acute respiratory distress syndrome, circulatory complications, electrolyte and acid-base disturbance, or more than three complications also had poor prognosis (P<0.05).

CONCLUSIONS

Poor prognosis of severe adenovirus pneumonia in children is associated with anemia, low serum albumin, inflammatory response, concurrent multiple complications and underlying lung diseases.

[Risk factors for poor prognosis in children with severe adenovirus pneumonia]

OBJECTIVE

To investigate the risk factors for poor prognosis of severe adenovirus pneumonia (SAP) in children.

METHODS

The clinical data of 189 children with SAP were retrospectively analyzed. Univariate logistic regression analysis was performed to assess the risk factors for poor prognosis.

RESULTS

The univariate logistic regression analysis showed that the patients with hemoglobin <90 g/L, plasma albumin <30 g/L, C-reactive protein >30 mg/L, procalcitonin >10 ng/mL, alanine aminotransferase >100 U/L, or aspartate aminotransferase >100 U/L had poor prognosis (P<0.05), and that those with congenital dysplasia of the airway, acute respiratory distress syndrome, circulatory complications, electrolyte and acid-base disturbance, or more than three complications also had poor prognosis (P<0.05).

CONCLUSIONS

Poor prognosis of severe adenovirus pneumonia in children is associated with anemia, low serum albumin, inflammatory response, concurrent multiple complications and underlying lung diseases.

Mechanisms of pathogenesis of emerging adenoviruses

Periodic outbreaks of human adenovirus infections can cause severe illness in people with no known predisposing conditions. The reasons for this increased viral pathogenicity are uncertain. Adenoviruses are constantly undergoing mutation during circulation in the human population, but related phenotypic changes of the viruses are rarely detected because of the infrequency of such outbreaks and the limited biological studies of the emergent strains. Mutations and genetic recombinations have been identified in these new strains. However, the linkage between these genetic changes and increased pathogenicity is poorly understood. It has been observed recently that differences in virus-induced immunopathogenesis can be associated with altered expression of non-mutant viral genes associated with changes in viral modulation of the host innate immune response. Initial small animal studies indicate that these changes in viral gene expression can be associated with enhanced immunopathogenesis in vivo. Available evidence suggests the hypothesis that there is a critical threshold of expression of certain viral genes that determines both the sustainability of viral transmission in the human population and the enhancement of immunopathogenesis. Studies of this possibility will require extension of the analysis of outbreak viral strains from a sequencing-based focus to biological studies of relationships between viral gene expression and pathogenic responses. Advances in this area will require increased coordination among public health organizations, diagnostic microbiology laboratories, and research laboratories to identify, catalog, and systematically study differences between prototype and emergent viral strains that explain the increased pathogenicity that can occur during clinical outbreaks.

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.

Neutralizing epitopes mapping of human adenovirus type 14 hexon

Human adenoviruses 14 (HAdV-14) caused several clusters of acute respiratory disease (ARD) outbreaks in both civilian and military settings. The identification of the neutralizing epitopes of HAdV-14 is important for the surveillance and control of infection. Since the previous studies had indicated that the adenoviruses neutralizing epitopes were likely to be exposed on the surface of the hexon, four epitope peptides, A14R1 (residues 141-157), A14R2 (residues 181-189), A14R4 (residues 252-260) and A14R7 (residues 430-442) were predicted and mapped onto the 3D structures of hexon by homology modeling approach. Then the four peptides were synthesized, and all the four putative epitopes were identified as neutralizing epitopes by enzyme-linked immunosorbent assay (ELISA) and neutralization tests (NT). Finally we incorporated the four epitopes into human adenoviruses 3 (HAdV-3) vectors using the "antigen capsid-incorporation" strategy, and two chimeric adenoviruses, A14R2A3 and A14R4A3, were successfully obtained which displayed A14R2 and A14R4 respectively on the hexon surface of HAdV-3 virions. Further analysis showed that the two chimeric viruses antiserum could neutralize both HAdV-14 and HAdV-3 infection. The neutralization titers of anti-A14R4A3 group were significantly higher than the anti-KLH-A14R4 group (P=0.0442). These findings have important implications for the development of peptide-based broadly protective HAdV-14 and HAdV-3 bivalent vaccine.

Low-Level Expression of the E1B 20-Kilodalton Protein by Adenovirus 14p1 Enhances Viral Immunopathogenesis

Adenovirus 14p1 (Ad14p1) is an emergent variant of Ad serotype 14 (Ad14) that has caused increased severity of respiratory illnesses during globally distributed outbreaks, including cases of acute respiratory distress syndrome and death. We found that human cell infection with Ad14p1 results in markedly decreased expression of the E1B 20-kilodalton (20K) protein compared to that with infection with wild-type (wt) Ad14. This reduced Ad14p1 E1B 20K expression caused a loss-of-function phenotype of Ad-infected cell corpses that, in contrast to cells infected with wt Ad14, either failed to repress or increased NF-κB-dependent, proinflammatory cytokine responses of responder human alveolar macrophages. A small-animal model of Ad14-induced lung infection was used to test the translational relevance of these in vitro observations. Intratracheal infection of Syrian hamsters with Ad14p1 caused a marked, patchy bronchopneumonia, whereas hamster infection with wt Ad14 caused minimal peribronchial inflammation. These results suggest that this difference in E1B 20K gene expression during Ad14p1 infection and its modulating effect on the interactions between Ad14-infected cells and the host innate immune response could explain the increased immunopathogenic potential and associated increase in clinical illness in some people infected with the Ad14p1 outbreak strain.IMPORTANCE We previously reported that Ad-infected human cells exhibit E1B 19K-dependent repression of virally induced, NF-κB-dependent macrophage cytokine responses (J. R. Radke, F. Grigera, D. S. Ucker, and J. L. Cook, J Virol 88:2658-2669, 2014, http://dx.doi.org/10.1128/JVI.02372-13). The more virulent, emergent strain of Ad14, Ad14p1, causes increased cytopathology in vitro, which suggested a possible E1B 20K defect. Whether there is a linkage between these observations was unknown. We show that there is markedly reduced expression of E1B 20K in Ad14p1-infected human cells and that this causes an increased proinflammatory cytokine response of human alveolar macrophages and more severe inflammatory lung disease in infected hamsters. This is the first evidence of a clinical relevance of differential expression of the small Ad E1B gene product. The results suggest that there is a low, critical threshold of E1B 19/20K expression that is needed for viral replication and infection transmission but that a higher level of E1B 19/20K expression is required for the usual repression and control of the Ad-triggered host innate immune response.

Intracellular Signaling and Desmoglein 2 Shedding Triggered by Human Adenoviruses Ad3, Ad14, and Ad14P1

We recently discovered that desmoglein 2 (DSG2) is a receptor for human adenovirus species B serotypes Ad3, Ad7, Ad11, and Ad14. Ad3 is considered to be a widely distributed human pathogen. Ad3 binding to DSG2 triggers the transient opening of epithelial junctions. Here, we further delineate the mechanism that leads to DSG2-mediated epithelial junction opening in cells exposed to Ad3 and recombinant Ad3 fiber proteins. We identified an Ad3 fiber knob-dependent pathway that involves the phosphorylation of mitogen-activated protein (MAP) kinases triggering the activation of the matrix-metalloproteinase ADAM17. ADAM17, in turn, cleaves the extracellular domain of DSG2 that links epithelial cells together. The shed DSG2 domain can be detected in cell culture supernatant and also in serum of mice with established human xenograft tumors. We then extended our studies to Ad14 and Ad14P1. Ad14 is an important research and clinical object because of the recent appearance of a new, more pathogenic strain (Ad14P1). In a human epithelial cancer xenograft model, Ad14P1 showed more efficient viral spread and oncolysis than Ad14. Here, we tested the hypothesis that a mutation in the Ad14P1 fiber knob could account for the differences between the two strains. While our X-ray crystallography studies suggested an altered three-dimensional (3D) structure of the Ad14P1 fiber knob in the F-G loop region, this did not significantly change the fiber knob affinity to DSG2 or the intracellular signaling and DSG2 shedding in epithelial cancer cells.

IMPORTANCE

A number of widely distributed adenoviruses use the epithelial junction protein DSG2 as a receptor for infection and lateral spread. Interaction with DSG2 allows the virus not only to enter cells but also to open epithelial junctions which form a physical barrier to virus spread. Our study elucidates the mechanism beyond virus-triggered junction opening with a focus on adenovirus serotype 3. Ad3 binds to DSG2 with its fiber knob domain and triggers intracellular signaling that culminates in the cleavage of the extracellular domain of DSG2, thereby disrupting DSG2 homodimers between epithelial cells. We confirmed this pathway with a second DSG2-interacting serotype, Ad14, and its recently emerged strain Ad14P1. These new insights in basic adenovirus biology can be employed to develop novel drugs to treat adenovirus infection as well as be used as tools for gene delivery into epithelial tissues or epithelial tumors.

Molecular Epidemiology and Phylogenetic Analysis of Human Adenovirus Caused an Outbreak in Taiwan during 2011

An outbreak of adenovirus has been surveyed in Taiwan in 2011. To better understand the evolution and epidemiology of adenovirus in Taiwan, full-length sequence of hexon and fiber coapsid protein was analyzed using series of phylogenetic and dynamic evolution tools. Six different serotypes were identified in this outbreak and the species B was predominant (HAdV-3, 71.50%; HAdV-7, 15.46%). The most frequent diagnosis was acute tonsillitis (54.59%) and bronchitis (47.83%). Phylogenetic analysis revealed that hexon protein gene sequences were highly conserved for HAdV-3 and HAdV-7 circulation in Taiwan. However, comparison of restriction fragment length polymorphism (RFLP) analysis and phylogenetic trees of fiber gene in HAdV-7 clearly indicated that the predominant genotype in Taiwan has shifted from 7b to 7d. Several positive selection sites were observed in hexon protein. The estimated nucleotide substitution rates of hexon protein of HAdV-3 and HAdV-7 were 0.234×10^-3 substitutions/site/year (95% HPD: 0.387~0.095×10^-3) and 1.107×10^-3 (95% HPD: 0. 541~1.604) respectively; those of the fiber protein of HAdV-3 and HAdV-7 were 1.085×10^-3 (95% HPD: 1.767~0.486) and 0.132×10^-3 (95% HPD: 0.283~0.014) respectively. Phylodynamic analysis by Bayesian skyline plot (BSP) suggested that using individual gene to evaluate the effective population size might possibly cause miscalculation. In summary, the virus evolution is ongoing, and continuous surveillance of this virus evolution will contribute to the control of the epidemic.

A human adenovirus species B subtype 21a associated with severe pneumonia

Between 2005 and 2013 six severe pneumonia cases (all requiring mechanical ventilation, two fatal outcomes) caused by human adenovirus type 21 (HAdV-B21) were observed in Germany. So far, HAdV-B21 was mainly associated with non-severe upper and lower respiratory tract infections. However, a few highly virulent HAdV types, e.g. HAdV-B14p1, were previously associated with severe, fatal pneumonia. Complete genomic sequences of the German HAdV-B21 pneumonia isolates formed a single phylogenetic cluster with very high sequence identity (≥ 99.897%). Compared to the HAdV-B21 prototype (only 99.319% identity), all isolates had a unique 15 amino acid deletion and a 2 amino acid insertion in the RGD loop of the penton base which may affect binding to the secondary receptor on the host cells. Moreover, a recombinant E4 gene region derived of HAdV-B3 was identified by bootscan analysis. Thus, the highly virulent, pneumotropic HAdV-B21 was denominated as subtype 21a. Surprisingly, there was 99.963% identity with agent Y/SIBU97 (only 13.4 kb available in GenBank of the 35.4 kb genome) which was associated with 10 fatalities due to cardiopulmonary failure in Sarawak, Malaysia, in 1997. In conclusion, a HAdV-B21 subtype (21a) associated with severe pneumonia in Germany was phylogenetically linked to an adenovirus isolated in Malaysia.

Genomic analysis of HAdV-B14 isolate from the outbreak of febrile respiratory infection in China

Human adenovirus type 14 (HAdV-B14) was first reported in 1955 from the Netherlands and since then had been associated with outbreaks of febrile respiratory illness (FRI). In China, sporadic HAdV-B14 infections were first identified in 2010, in Guangzhou and Beijing. In 2012, an outbreak of FRI occurred in Beijing and the etiological agent was determined to be HAdV-B14. We present a complete HAdV-B14 genome sequence isolated from this recent FRI outbreak. Virus in 30 throat swab samples was detected using polymerase chain reaction assays, and confirmed by sequencing of the fiber, hexon and penton genes. Comparative genomics and phylogenetic analysis showed that the newly isolated HAdV-B14 (HAdV-B14 CHN) shared highest sequence homology with a 2006 isolate from the United States and clustered closely with other HAdV-B14 strains. It is expected that data from the present study will help in devising better protocols for virus surveillance, and in developing preventative measures.

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Isolation of HAdV-B14 was performed from the outbreak of febrile respiratory illness.

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Full genome sequence of HAdV-B14 CHN strain has been reported.

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Several nucleotide substitutions were reported in the HAdV-B14 CHN genome.

A cost effective real-time PCR for the detection of adenovirus from viral swabs

Compared to traditional testing strategies, nucleic acid amplification tests such as real-time PCR offer many advantages for the detection of human adenoviruses. However, commercial assays are expensive and cost prohibitive for many clinical laboratories. To overcome fiscal challenges, a cost effective strategy was developed using a combination of homogenization and heat treatment with an “in-house” real-time PCR. In 196 swabs submitted for adenovirus detection, this crude extraction method showed performance characteristics equivalent to viral DNA obtained from a commercial nucleic acid extraction. In addition, the in-house real-time PCR outperformed traditional testing strategies using virus culture, with sensitivities of 100% and 69.2%, respectively. Overall, the combination of homogenization and heat treatment with a sensitive in-house real-time PCR provides accurate results at a cost comparable to viral culture.

Outbreak of febrile respiratory illness associated with human adenovirus type 14p1 in Gansu Province, China

Objectives

Human adenovirus (HAdV) type 14 had been infrequently associated with outbreaks of febrile respiratory illness (FRI) until the HAdV‐14p1 emerged in 2006 and rapidly spread in the United States. Here, we report an outbreak of FRI caused by HadV‐14p1 that occurred in 2011 at a primary and middle school in China.

Design

The basic information of the outbreak was recored; throat swabs were collected from 17 patients, polymerase chain reaction, A549 cell culture, and sequencing were used to identify the pathogen of the outbreak..

Results

Total of 43 students were infected in this outbreak. Boys were more than girls. We identified 11 HAdV‐positive specimens and 6 HAdV isolates. Genetic analysis showed that the complete hexon, fiber, and E1A sequences of isolates were nearly 100% identical with other HAdV‐14p1 sequences deposited in GenBank.

Conclusions

HadV‐14p1 has caused outbreaks of pneumonia and mortality among adults in the United States and Europe. It may cause similar conditions among Chinese adults due to poor hygiene and sanitation. It seems prudent for China to develop a national surveillance system to determine the etiology of severe respiratory diseases and deaths among adults and school‐aged children.

Genome and bioinformatic analysis of a HAdV-B14p1 virus isolated from a baby with pneumonia in Beijing, China

The genome of HAdV-B14p1 strain BJ430, isolated from a six-month-old baby diagnosed with bronchial pneumonia at the Beijing Children’s Hospital in December 2010, was sequenced, analyzed, and compared with reference adenovirus genome sequences archived in GenBank. This genome is 34,762 bp in length, remarkably presenting 99.9% identity with the genome from HAdV14p1 strain 303600, which was isolated in the USA (2006). Even more remarkable, it is 99.7% identical with the HAdV-B14p (prototype “de Wit” strain) genome, isolated from The Netherlands in 1955. The patient and its parents presumably had no or limited contact with persons from the USA and Ireland, both of which reported outbreaks of the re-emergent virus HAdV-14p1 recently. These genome data, its analysis, and this report provide a reference for any additional HAdV-B14 outbreak in China and provide the basis for the development of adenovirus vaccines and molecular pathogen surveillance protocols in high-risk areas.

Temporal changes in respiratory adenovirus serotypes circulating in the greater Toronto area, Ontario, during December 2008 to April 2010

Background

Certain adenovirus serotypes cause severe infections, especially in children. It is important to monitor temporal changes in serotypes causing clinical disease. The objective of this study was to document circulating respiratory adenovirus serotypes by sequencing adenovirus culture isolates from the Greater Toronto Area, Ontario, during December 2008 to April 2010.

Methods

Nucleic acid extraction was performed on 90 respiratory tract adenovirus culture isolates. PCR amplification was conducted with primers targeting the adenovirus hexon gene hypervariable region 7. Sanger sequencing and phylogenetic analyses were performed to determine serotype identities.

Results

Among 90 clinical respiratory isolates sequenced, eight different serotypes were identified. Serotype 3 (34, 38%), serotype 2 (30, 30%), and serotype 1 (14, 16%) isolates were most common; serotypes 5, 6, 11, 17 and 21 were also observed. Seventeen (50%) of the 34 HAdV-3 isolates were identified between December 2008 and February 2009, while none were identified from December 2009 to February 2010. Between December 2008 and April 2009, the two most common serotypes were HAdV-3 and HAdV-2, detected in 18 (53%) and 8 (24%) of the 34 cultures isolates, respectively. However, from December 2009 to April 2010, there was an increase in HAdV-2, which became the most prevalent serotype, detected in 10 (50%) of the 20 isolates identified (p = 0.05).

Conclusions

There was a gradual shift in prevailing adenovirus serotypes during the 17 month study period, from predominantly HAdV-3 to HAdV-2. If an adenovirus vaccine were to be broadly implemented, multiple serotypes should be included.

A comparison of viral fitness and virulence between emergent adenovirus 14p1 and prototype adenovirus 14p strains

BACKGROUND

Epidemiological studies from the last decade have suggested that the morbidity and mortality associated with a newly emergent strain of human adenovirus (HAdV-14p1) is greater than other, more prevalent, adenovirus strains. Recent molecular analysis identified very minor genetic differences in HAdV-14p1 compared to prototype HAdV-14p. No studies have evaluated how these differences may affect virulence.

OBJECTIVE

To compare HAdV-14p1 and HAdV-14p strains for competitive fitness and virulence.

STUDY DESIGN

We performed in vitro and molecular assays to evaluate growth kinetics, cellular infectivity, cytotoxicity, and plaque morphology of the two strains.

RESULTS

Growth kinetic data showed no viral replication at 30°C and minimal differences at 37°C for both strains. Cellular infectivity data showed propagation capabilities for both strains in a diverse array of cell lines, with human lung and kidney cells having the highest propagation potential. Cytotoxicity data indicated cellular distress differences induced by both strains of virus in the first 12h, but similar distress levels between 12 and 48 h. Plaque morphology assays showed some differences in average plaque diameter.

CONCLUSIONS

These data suggest that the increase in morbidity and mortality observed in recent HAdV-14p1 infections is not due to viral growth or cellular infectivity differences from the prototypic HAdV-14 strain. While there were some statistically important differences detected between strains in cytotoxicity and plaque morphology assays, it seems more likely that other factors, such as environmental stressors, co-infections, or individual host response are likely contributing to the increase in morbidity.

Structure-based high-throughput epitope analysis of hexon proteins in B and C species human adenoviruses (HAdVs)

Human adenoviruses (HAdVs) are the etiologic agent of many human infectious diseases. The existence of at least 54 different serotypes of HAdVs has resulted in difficulties in clinical diagnosis. Acute respiratory tract disease (ARD) caused by some serotypes from B and C species is particularly serious. Hexon, the main coat protein of HAdV, contains the major serotype-specific B cell epitopes; however, few studies have addressed epitope mapping in most HAdV serotypes. In this study, we utilized a novel and rapid method for the modeling of homologous proteins based on the phylogenetic tree of protein families and built three-dimensional (3D) models of hexon proteins in B and C species HAdVs. Based on refined hexon structures, we used reverse evolutionary trace (RET) bioinformatics analysis combined with a specially designed hexon epitope screening algorithm to achieve high-throughput epitope mapping of all 13 hexon proteins in B and C species HAdVs. This study has demonstrated that all of the epitopes from the 13 hexon proteins are located in the proteins' tower regions; however, the exact number, location, and size of the epitopes differ among the HAdV serotypes.

Deaths associated with human adenovirus-14p1 infections, Europe, 2009-2010

Human adenovirus (HAdV) serotype 14 is rarely identified. However, an emerging variant, termed HAdV-14p1, recently has been described in the United States in association with outbreaks of acute respiratory disease with high rates of illness and death. We retrospectively analyzed specimens confirmed positive for HAdV by immunofluorescence, virus culture, or real-time PCR during July 1, 2009-July 31, 2010, and describe 9 cases of HAdV-14p1 infection with characteristic mutations in the fiber and E1A genes that are phylogenetically indistinguishable from the viruses previously detected in the United States. Three patients died; 2 were immunocompromised, and 1 was an immunocompetent adult. We propose that surveillance should be increased for HAdV-14p1 and recommend that this virus be considered in the differential diagnosis of sudden-onset acute respiratory disease, particularly fatal infections, for which an etiology is not clear.

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.