Mechanisms of pathogenesis of emerging adenoviruses

Development and validation of a quantitative PCR assay for detection of Sulawesi tortoise adenovirus

In 2007, a mortality event involving over 100 Sulawesi tortoises (Indotestudo forsteni), two Impressed tortoises (Manouria impress) and a critically endangered Burmese star tortoise (Geochelone platynota) was attributed to Sulawesi tortoise adenovirus (STADV; genus Siadenovirus). We developed a TaqMan quantitative PCR assay targeting the DNA polymerase gene of STADV for use in clinical diagnosis and epidemiologic surveillance. This assay failed to amplify five closely-related chelonian adenoviruses, indicating high analytical specificity. The assay performed with high efficiency (slope = -3.337; R2 = 0.999) and high inter- and intra-assay repeatability (coefficient of variation <1.36 % at all standard curve dilutions). Dynamic range included 1.00 × 107 to 1.00 × 101 target copies per reaction and limit of detection was 101 target copies per reaction, though 100 target copies per reaction were intermittently detected. This qPCR assay provides a valuable diagnostic tool for characterization of STADV epidemiology, including potential identification of the North American reservoir host.

Breaking the Chain: Protease Inhibitors as Game Changers in Respiratory Viruses Management

Respiratory viral infections (VRTIs) rank among the leading causes of global morbidity and mortality, affecting millions of individuals each year across all age groups. These infections are caused by various pathogens, including rhinoviruses (RVs), adenoviruses (AdVs), and coronaviruses (CoVs), which are particularly prevalent during colder seasons. Although many VRTIs are self-limiting, their frequent recurrence and potential for severe health complications highlight the critical need for effective therapeutic strategies. Viral proteases are crucial for the maturation and replication of viruses, making them promising therapeutic targets. This review explores the pivotal role of viral proteases in the lifecycle of respiratory viruses and the development of protease inhibitors as a strategic response to these infections. Recent advances in antiviral therapy have highlighted the effectiveness of protease inhibitors in curtailing the spread and severity of viral diseases, especially during the ongoing COVID-19 pandemic. It also assesses the current efforts aimed at identifying and developing inhibitors targeting key proteases from major respiratory viruses, including human RVs, AdVs, and (severe acute respiratory syndrome coronavirus-2) SARS-CoV-2. Despite the recent identification of SARS-CoV-2, within the last five years, the scientific community has devoted considerable time and resources to investigate existing drugs and develop new inhibitors targeting the virus's main protease. However, research efforts in identifying inhibitors of the proteases of RVs and AdVs are limited. Therefore, herein, it is proposed to utilize this knowledge to develop new inhibitors for the proteases of other viruses affecting the respiratory tract or to develop dual inhibitors. Finally, by detailing the mechanisms of action and therapeutic potentials of these inhibitors, this review aims to demonstrate their significant role in transforming the management of respiratory viral diseases and to offer insights into future research directions.

Higher affinities of fibers with cell receptors increase the infection capacity and virulence of human adenovirus type 7 and type 55 compared to type 3

IMPORTANCE

HAdV-3, -7, and -55 are the predominant types causing acute respiratory disease outbreaks and can lead to severe and fatal pneumonia in children and adults. In recent years, emerging or re-emerging strains of HAdV-7 and HAdV-55 have caused multiple outbreaks globally in both civilian and military populations, drawing increased attention. Clinical studies have reported that HAdV-7 and HAdV-55 cause more severe pneumonia than HAdV-3. This study aimed to investigate the mechanisms explaining the higher severity of HAdV-7 and HAdV-55 infection compared to HAdV-3 infection. Our findings provided evidence linking the receptor-binding protein fiber to stronger infectivity of the strains mentioned above by comparing several fiber-chimeric or fiber-replaced adenoviruses. Our study improves our understanding of adenovirus infection and highlights potential implications, including in novel vector and vaccine development.

Pediatric adenovirus pneumonia: clinical practice and current treatment

Adenovirus pneumonia is common in pediatric upper respiratory tract infection, which is comparatively easy to develop into severe cases and has a high mortality rate with many influential sequelae. As for pathogenesis, adenoviruses can directly damage target cells and activate the immune response to varying degrees. Early clinical recognition depends on patients' symptoms and laboratory tests, including those under 2 years old, dyspnea with systemic toxic symptoms, atelectasis or emphysema in CT image, decreased leukocytes, and significantly increased C-reaction protein (CRP) and procalcitonin (PCT), indicating the possibility of severe cases. Until now, there is no specific drug for adenovirus pneumonia, so in clinical practice, current treatment comprises antiviral drugs, respiratory support and bronchoscopy, immunomodulatory therapy, and blood purification. Additionally, post-infectious bronchiolitis obliterans (PIBO), hemophagocytic syndrome, and death should be carefully noted. Independent risk factors associated with the development of PIBO are invasive mechanical ventilation, intravenous steroid use, duration of fever, and male gender. Meanwhile, hypoxemia, hypercapnia, invasive mechanical ventilation, and low serum albumin levels are related to death. Among these, viral load and serological identification are not only "gold standard" for adenovirus pneumonia, but are also related to the severity and prognosis. Here, we discuss the progress of pathogenesis, early recognition, therapy, and risk factors for poor outcomes regarding severe pediatric adenovirus pneumonia.

Human adenovirus DNA polymerase is evolutionarily and functionally associated with human telomerase reverse transcriptase based on in silico molecular characterization that implicate abacavir and zidovudine

Human adenoviruses (HAdVs) are non-enveloped, small double stranded DNA (dsDNA) viruses that cause asymptomatic infections, clinical syndromes and significant susceptibility to infections in immunocompromised people. The aim of the present study was to identify critical host proteins and HAdV hypothetical proteins that could be developed as potential host-viral targets for antiHAdV therapy. Here, the function of selected hypothetical proteins of HAdV based on phylogenetic relationship with the therapeutic targets of antiretroviral drugs of human immunodeficiency virus (HIV) was predicted computationally, and characterized the molecular dynamics and binding affinity of DNA polymerase of HAdV. Thirty-eight hypothetical proteins (HPs) of human adenovirus (HAdV) were used in this study. The results showed that HAdV DNA polymerase (P03261) is related to Human TERT (O14746) and HLA-B (P01889) genes. The protein-protein interaction of human five molecular targets (PNP, TERT, CCR5, HLA-B, and NR1I2) of ARVDs are well-coordinated/networked with CD4, AHR, FKBP4, NR3C1, HSP90AA1, and STUB1 proteins in the anti-HIV infection mechanism. The results showed that the free energy score of abacavir and zidovudine binding to HAdV DNA polymerase are -5.8 and -5.4 kcal mol^-1 respectively. Also, the control drug, cidofovir and ganciclovir have less binding affinity for DNA polymerase of HAdV when compare to that of abacavir and zidovudine. Similarity was observed in the binding of abacavir and zidovudine to HAdV DNA polymerase (ASP742, ALA743, LEU772, ARG773 and VAL776). In conclusion, combination of abacavir and zidovudine was predicted to be potential therapy for controlling HAdV infection targeting HAdV DNA polymerase.

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.

Outbreak of acute respiratory disease caused by human adenovirus type 7 and human coronavirus-229E in Zhejiang Province, China

In 2019, an outbreak of pharyngoconjunctival fever (PCF) occurred at a swimming center in Zhejiang Province, China. A total of 97 (13.55%) of the 716 amateur swimmers had illnesses, with 24 patients (24.74%) hospitalized in the pediatric ward. Human adenovirus serotype 7 (HAdV-7) was isolated from one concentrated water from the swimming pool, and 20 of 97 positive cases without liver damage. This outbreak led to a nosocomial outbreak in the pediatric ward, in which 1 nurse had a fever and was confirmed to be adenovirus positive. The hexon, fiber, and penton genes from 20 outbreak cases, 1 water sample, and 1 nurse had 100% homology. Furthermore, 2 cases admitted to the pediatric ward, 2 parents, and 1 doctor were confirmed to be human coronaviruses (HCoV-229E) positive. Finally, all outbreak cases had fully recovered, regardless of a single infection (adenovirus or HCoV-229E) or coinfection of these two viruses simultaneously. Thus, PCF and acute respiratory disease outbreaks in Zhejiang were caused by the completely homologous type 7 adenovirus and HCoV-229E, respectively. The swimming pool water contaminated with HAdV-7 was most likely the source of the PCF outbreak, whereas nosocomial transmission might be the source of HCoV-229E outbreak.

IN SITU HYBRIDIZATION AND VIRUS CHARACTERIZATION OF SKUNK ADENOVIRUS IN NORTH AMERICAN WILDLIFE REVEALS MULTISYSTEMIC INFECTIONS IN A BROAD RANGE OF HOSTS

Skunk adenovirus-1 (SkAdV-1) has been reported infecting several North American wildlife species; however, lesions associated with disease have not yet been completely characterized, particularly in porcupines. We describe and characterize the tissue distribution and lesions associated with SkAdV-1 infection in 24 wildlife diagnostic cases submitted between 2015 and 2020, including 16 North American porcupines (Erethizon dorsatum), three striped skunks (Mephitis mephitis), and five raccoons (Procyon lotor), which constitute a new host species. The most common lesion in all species was severe necrotizing bronchopneumonia with (n=12) or without (n=10) interstitial involvement. Intranuclear inclusion bodies were common in respiratory epithelium (n=21) and less often in renal tubular (n=6) and biliary epithelium (n=1). Several cases (n=4) had secondary bacterial infections, including Bordetella bronchiseptica, Pasteurella multocida, and Streptococcus zooepidemicus. In situ hybridization in porcupine (n=6), raccoon (n=1), and skunk (n=1) revealed SkAdV-1 DNA in multiple tissue types, including lung, trachea, turbinates, liver, kidney, lymph node, and brain, and multiple cell types including epithelial, endothelial, and mesothelial cells. These findings were consistent across species. Comparison of viral genomes from a porcupine and a raccoon with that originally isolated from a skunk demonstrated DNA point mutations affecting several viral genes, including the fiber protein gene. Our findings show the spectrum of disease associated with SkAdV-1 infection in a broad host range of wildlife species.

Clinical and imaging findings of patients diagnosed with adenovirus-positive pneumonia during 2015-2019 in Shanghai, China

BACKGROUND

This study was to describe the clinical characteristics, chest CT image findings, and potential role of T cells immunity in adenovirus positive pneumonia.

METHODS

In this retrospective study, medical records of 53 adult Adv+ patients who were admitted to the Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, from May 2015 to August 2019 were included. The presence of adenovirus and other respiratory viruses was detected using polymerase chain reaction of throat swabs samples. Clinical features and chest computed tomography (CT) findings were compared between patients with Adv+ pneumonia and Adv+ non-pneumonia.

RESULTS

The top 3 most commonly occurring symptoms in Adv+ pneumonia patients were fever (66.7%), cough (63.3%), and tachypnea (16.7%). Patients with Adv+ pneumonia showed significantly higher rates of cough and fever and longer duration of hospitalization than patients with Adv+ non-pneumonia. In the Adv+ pneumonia group, consolidation (73.3%) was the most common imaging finding on chest CT scan, and the likelihood of involvement of bilateral lobes (60%) was high. Classical conspicuous consolidation with surrounding ground-glass opacity was observed in 5 (16.6%) patients with Adv+ pneumonia. Patients with Adv+ pneumonia showed a higher inhibition of T-cell immunity than did patients with Adv+ non-pneumonia, and counts of CD3+, CD4+, and CD8+ T-cells may predict the presence of pneumonia in Adv+ patients.

DISCUSSION

With regard to Adv+ pneumonia, the most frequent symptoms were cough and fever, and the most common CT pattern was consolidation; classical CT findings such as consolidation with surrounding ground-glass opacity could also be observed. Furthermore, our data indicated the incidence of abrogated cellular immunity in patients with Adv+ pneumonia.

mRNA- and Adenovirus-Based Vaccines against SARS-CoV-2 in HIV-Positive People

About two years have passed since the identification of SARS-CoV-2 in China. The rapid spread of this virus all over the world and its high transmissibility and pathogenicity in humans have resulted in a global pandemic. The negative impact of COVID-19 on health, society and the economy at the global level has pushed researchers and pharmaceutical companies to develop effective vaccines to fight SARS-CoV-2. Thanks to this collaborative effort, the first COVID-19 vaccine was developed in less than a year. Since then, several COVID-19 vaccines have been validated for use by the World Health Organization. Among these, mRNA- (BNT162b2 and mRNA1273) and adenovirus-based (ChAdOx1) vaccines were developed through the use of novel technologies. While all three of these vaccines have shown effectiveness against the COVID-19 disease and their immunogenicity was characterized in clinical trials in the general population, data on their efficacy and immunogenicity in people living with HIV (PLWH) are limited. In this review, we provide a description of the characteristics of mRNA- and adenovirus-based vaccines and of the immune response elicited in the general population by vaccination. Then we describe the use of these vaccines and their efficacy and immunogenicity in people living with HIV and we conclude with a discussion regarding some open questions concerning the use of mRNA- and adenovirus-based COVID-19 vaccines in PLWH.

Isolation and molecular characterization of Adenovirus in suspected acute flaccid paralysis patients: A preliminary report from Pakistan

Human adenoviruses (HAdVs) usually cause asymptomatic or mild infection, but infrequently, they are responsible for various severe syndromes including neurological disorders. Various research studies have investigated the association of HAdVs with acute flaccid paralysis (AFP). The purpose of this study was to investigate the genetic diversity of HAdVs and their association with AFP. Stool samples from patients ≤ 12 years of age with suspected AFP were collected from all over Pakistan within the framework of poliovirus surveillance. Poliovirus- and enterovirus-negative samples were screened for HAdVs. For virus isolation, the human epithelial cell line HEp-2c was used, culture-positive samples were screened by nested PCR assay, and partial hexon gene sequences were used for genotype identification. Out of 172 samples, 94 were positive by virus isolation, 89 were positive by PCR, and 32 isolates were genotyped successfully. Phylogenetic analysis showed that the HAdVs belonged to species A (HAdV-A12 and A31), B (HAdV-B3 and B7), C (HAdV-C1 and C6), D (HAdV-D19 and D93), and F (HAdV-F41), showing 99-100% nucleotide sequence identity and 98.3-100% amino acid sequence identity). Most of these genotypes have been reported previously in AFP cases, but this is the first report of the detection of HAdV-D93 in stool samples from AFP cases. The detection of a significant fraction of the HAdVs genotypes indicates that these genetically distinct genotypes are circulating in Pakistan and suggests their possible role in the pathogenesis of AFP.

Comparative analyses of clinical features reveal the severity of human adenovirus type 55 and type 7 in acute respiratory tract infections

Introduction. Human adenovirus (HAdV) is an important pathogen in acute respiratory tract infections (ARTIs) and HAdV genotypes are associated with disease severity.Hypothesis. Comparative analyses of clinical features could reveal the severity of different HAdV genotypes in ARTIs.Aim. This study aimed to investigate the molecular epidemiology of HAdV infections and explore the correlations between clinical features and HAdV genotypes.Methodology. A retrospective study was conducted on ARTIs at Beijing Chao-Yang Hospital during the period 2011-2016. A standardized data form was used to record the clinical information. HAdV was detected by FQ-PCR from respiratory specimens, and genotypes were determined by entire hexon gene sequencing.Results. A total of 8044 samples were collected, of which 296 (3.7 %) were HAdV-positive. Patients ≤44 years old were more likely to be positive for HAdV. There were three peak periods of adenoviral infections, with detection rates of 13.03, 9.39 and 10.38 %, respectively. Six HAdV genotypes (HAdV-55, -7, -3, -14, -50, -2) were identified, with HAdV-55 and HAdV-7 being the most prevalent (50.6 and 21.5 %). Compared with HAdV-7 and other types, patients infected with HAdV-55 had a longer duration of fever (P=0.0428). Infections with HAdV-55 and HAdV-7 were more severe compared to those caused by other types, with higher rates of oxygen therapy and mechanical ventilation (P=0.0172 and P=0.0144). All five deaths were caused by HAdV-55.Conclusion. This study describes the epidemiological characteristics of HAdV infections in North China, revealing the higher severity of HAdV-55 and HAdV-7 in ARTIs. Thus, strengthened surveillance of HAdV genotypes is warranted.

Influence of the timing of bronchoscopic alveolar lavage on children with adenovirus pneumonia: a comparative study

Background

Adenovirus pneumonia is prone to severe clinical and imaging manifestations in children. Bronchoscopic alveolar lavage (BAL) is an important adjunctive therapy for patients with severe imaging findings. The study aimed to evaluate the effect of the timing on the efficacy of bronchoalveolar lavage in children with adenovirus pneumonia.

Methods

This study included 134 patients with adenovirus pneumonia treated with BAL at Guangzhou Women and Children's Medical Center from January 2019 to January 2020.They were classified into the severe and mild groups. Based on the timing of BAL, each group was divided into the early BAL layer (received BAL within 1–9 days of the illness course) and the late BAL layer (received BAL within 10–14 days of the illness course). The clinical data of patients with different BAL timings were analyzed in two groups.

Results

Among the 134 patients, 70 were categorized into the mild group and 64 were categorized into the severe group. Of the 134 patients, 42 patients received BAL early (mild group: n = 21 and severe group: n = 21) and 92 patients received BAL later (mild group: n = 49 and severe group: n = 43). In the mild group, the fever and hospital duration were shorter in patients who received BAL early than in those who received BAL later (p < 0.05). However, in the severe group, there were no statistically significant differences in the fever and hospital duration between patients who received BAL early and those who received BAL later. However, the need for mechanical ventilation and the incidence of BAL complications, such as new need for oxygen, were higher in patients who received BAL early than in those who received BAL later in the severe group (p < 0.05).

Conclusion

For mild adenovirus pneumonia, early BAL may shorten the fever and hospital duration. However, early BAL in severe cases might not shorten the course of the disease or improve prognosis and may even increase the risks of mechanical ventilation and BAL complications.

Viral Respiratory Pathogens and Lung Injury

Several viruses target the human respiratory tract, causing different clinical manifestations spanning from mild upper airway involvement to life-threatening acute respiratory distress syndrome (ARDS). As dramatically evident in the ongoing SARS-CoV-2 pandemic, the clinical picture is not always easily predictable due to the combined effect of direct viral and indirect patient-specific immune-mediated damage. In this review, we discuss the main RNA (orthomyxoviruses, paramyxoviruses, and coronaviruses) and DNA (adenoviruses, herpesviruses, and bocaviruses) viruses with respiratory tropism and their mechanisms of direct and indirect cell damage. We analyze the thin line existing between a protective immune response, capable of limiting viral replication, and an unbalanced, dysregulated immune activation often leading to the most severe complication. Our comprehension of the molecular mechanisms involved is increasing and this should pave the way for the development and clinical use of new tailored immune-based antiviral strategies.

Development and evaluation of a loop-mediated isothermal amplification assay for clinical diagnosis of respiratory human adenoviruses emergent in China

Three human adenovirus (HAdV) genotypes, HAdV-7, HAdV-14, and HAdV-55, emerged as the most prevalent variants in China over the past decade and caused both sporadic, fatal cases and frequent, large outbreaks. Early diagnosis is essential to control infections and endemics. Here, we established a loop-mediated isothermal amplification (LAMP) assay coupled with an instrument-free nucleic acid extraction device recently developed by our group; the assay could detect all the 3 prevalent HAdV genotypes. Specificity analysis showed no cross-reactivity with other common respiratory pathogens and the analytical sensitivity was as low as 10 copies/μL. All detection steps could be completed within 1 hour. The assay's performance was evaluated using clinical samples and compared with the gold standard RT-PCR method, showing highly consistent results. The LAMP assay developed here could be readily used in basic laboratory facilities and with minimal DNA extraction equipment, and as a reliable screening test in a resource-limited setting.

Airway tight junctions as targets of viral infections

The apical junctional complexes (AJCs) of airway epithelial cells are a key component of the innate immune system by creating barriers to pathogens, inhaled allergens, and environmental particles. AJCs form between adjacent cells and consist of tight junctions (TJs) and adherens junctions (AJs). Respiratory viruses have been shown to target various components of the AJCs, leading to airway epithelial barrier dysfunction by different mechanisms. Virus-induced epithelial permeability may allow for allergens and bacterial pathogens to subsequently invade. In this review, we discuss the pathophysiologic mechanisms leading to disruption of AJCs and the potential ensuing ramifications. We focus on the following viruses that affect the pulmonary system: respiratory syncytial virus, rhinovirus, influenza viruses, immunodeficiency virus, and other viruses such as coxsackievirus, adenovirus, coronaviruses, measles, parainfluenza virus, bocavirus, and vaccinia virus. Understanding the mechanisms by which viruses target the AJC and impair barrier function may help design therapeutic innovations to treat these infections.

Aptamer-based approaches for the detection of waterborne pathogens

Waterborne ailments pose a serious threat to public health and are a huge economic burden. Lack of hygiene in drinking and recreational water is the chief source of microbial pathogens in developing countries. Poor water quality and sanitation account for more than 3.4 million deaths a year worldwide. This has urged authorities and researchers to explore different avenues of pathogen detection. There is a growing demand for rapid and reliable sensor technologies, in particular those that can detect in situ and perform in harsh conditions. Some of the major waterborne pathogens include Vibrio cholerae, Leptospira interrogans, Campylobacter jejuni, Shigella spp., enterotoxigenic Escherichia coli, Clostridium difficile, Cryptosporidium parvum, Entamoeba histolytica, and Hepatitis A virus. While conventional methods of pathogen detection like serodiagnosis and microbiological methods have been superseded by nucleic acid amplification methods, there is still potential for improvement. This review provides an insight into aptamers and their utility in the form of aptasensors. It discusses how aptamer-based approaches have emerged as a novel strategy and its advantages over more resource-intensive and complex biochemical approaches.

The E3 Ubiquitin Ligase Mind Bomb 1 Controls Adenovirus Genome Release at the Nuclear Pore Complex

Adenoviruses (AdVs) cause respiratory, ocular, and gastrointestinal tract infection and inflammation in immunocompetent people and life-threatening disease upon immunosuppression. AdV vectors are widely used in gene therapy and vaccination. Incoming particles attach to nuclear pore complexes (NPCs) of post-mitotic cells, then rupture and deliver viral DNA (vDNA) to the nucleus or misdeliver to the cytosol. Our genome-wide RNAi screen in AdV-infected cells identified the RING-type E3 ubiquitin ligase Mind bomb 1 (Mib1) as a proviral host factor for AdV infection. Mib1 is implicated in Notch-Delta signaling, ciliary biogenesis, and RNA innate immunity. Mib1 depletion arrested incoming AdVs at NPCs. Induced expression of full-length but not ligase-defective Mib1 in knockout cells triggered vDNA uncoating from NPC-tethered virions, nuclear import, misdelivery of vDNA, and vDNA expression. Mib1 is an essential host factor for AdV uncoating in human cells, and it provides a new concept for licensing virion DNA delivery through the NPC.

Multiple divergent Human mastadenovirus C co-circulating in mainland of China

The human mastadenovirus C (HAdV-C) cause respiratory infections in children. Homologous recombination was clearly involved in the molecular evolution of HAdV-A, B, and D, but little is known about the molecular evolution of HAdV-C. From 2000 to 2016, 201 HAdV-C strains were collected from nine provinces covering six administrative regions of mainland of China via 3 existing surveillance programs, namely the febrile respiratory syndrome surveillance, the acute flaccid paralysis surveillance, and the hand, foot, and mouth disease surveillance system. The genes coding for the capsid protein (penton base, hexon, and fiber) of 201 HAdV-C strains were sequenced and compared with representative sequences publicly available. In addition, the whole genome sequence of 24 representative strains of HAdV-C was generated for further recombination analysis. Phylogenetic analysis of the penton base sequences of HAdV-C revealed six genetic groups (labelled as Px1-6), which showed that the penton base had more variation than previously thought. Based on the penton base, hexon, and fiber gene sequences, 16 new genetic patterns of HAdV-C circulating in mainland of China were identified in this study. Whole genome sequence analysis revealed frequent recombination events among HAdV-C genomes. This study is highly beneficial for case classification, tracking the transmission chain, and further epidemiological exploration of HAdV-C-related severe clinical diseases in the near future. Our data demonstrated that multiple newly divergent HAdV-C co-circulated across mainland China during the research period.

Adenovirus early region 3 RIDα protein limits NFκB signaling through stress-activated EGF receptors

The host limits adenovirus infections by mobilizing immune systems directed against infected cells that also represent major barriers to clinical use of adenoviral vectors. Adenovirus early transcription units encode a number of products capable of thwarting antiviral immune responses by co-opting host cell pathways. Although the EGF receptor (EGFR) was a known target for the early region 3 (E3) RIDα protein encoded by nonpathogenic group C adenoviruses, the functional role of this host-pathogen interaction was unknown. Here we report that incoming viral particles triggered a robust, stress-induced pathway of EGFR trafficking and signaling prior to viral gene expression in epithelial target cells. EGFRs activated by stress of adenoviral infection regulated signaling by the NFκB family of transcription factors, which is known to have a critical role in the host innate immune response to infectious adenoviruses and adenovirus vectors. We found that the NFκB p65 subunit was phosphorylated at Thr254, shown previously by other investigators to be associated with enhanced nuclear stability and gene transcription, by a mechanism that was attributable to ligand-independent EGFR tyrosine kinase activity. Our results indicated that the adenoviral RIDα protein terminated this pathway by co-opting the host adaptor protein Alix required for sorting stress-exposed EGFRs in multivesicular endosomes, and promoting endosome-lysosome fusion independent of the small GTPase Rab7, in infected cells. Furthermore RIDα expression was sufficient to down-regulate the same EGFR/NFκB signaling axis in a previously characterized stress-activated EGFR trafficking pathway induced by treatment with the pro-inflammatory cytokine TNF-α. We also found that cell stress activated additional EGFR signaling cascades through the Gab1 adaptor protein that may have unappreciated roles in the adenoviral life cycle. Similar to other E3 proteins, RIDα is not conserved in adenovirus serotypes associated with potentially severe disease, suggesting stress-activated EGFR signaling may contribute to adenovirus virulence.

New Insights to Adenovirus-Directed Innate Immunity in Respiratory Epithelial Cells

The nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) family of transcription factors is a key component of the host innate immune response to infectious adenoviruses and adenovirus vectors. In this review, we will discuss a regulatory adenoviral protein encoded by early region 3 (E3) called E3-RIDα, which targets NFκB through subversion of novel host cell pathways. E3-RIDα down-regulates an EGF receptor signaling pathway, which overrides NFκB negative feedback control in the nucleus, and is induced by cell stress associated with viral infection and exposure to the pro-inflammatory cytokine TNF-α. E3-RIDα also modulates NFκB signaling downstream of the lipopolysaccharide receptor, Toll-like receptor 4, through formation of membrane contact sites controlling cholesterol levels in endosomes. These innate immune evasion tactics have yielded unique perspectives regarding the potential physiological functions of host cell pathways with important roles in infectious disease.

Transcriptome Sequencing Identifies Novel Immune Response Genes Highly Related to the Severity of Human Adenovirus Type 55 Infection

Human adenovirus type 55 (HAdV-55) is considered a highly virulent pathogen causing severe and even deadly pneumonia in immunocompetent people. The mechanisms of HAdV-55-induced initiation and progression of severe pneumonia remain ambiguous. In the current study, we endeavored to identify novel immune response genes which are substantially involved in the pathogenesis of severe inflammation in HAdV-55-infected patients. HAdV-55-infected patients with upper respiratory tract symptoms (minor patients) and pneumonia (severe patients) were enrolled. Through transcriptome sequencing and quantitative real-time PCR, the peripheral blood mononuclear cells of the patients were analyzed. We found that the expression of eight genes, including Il18, Il36b, Il17rc, Tnfsf10, Tnfsf11, Tnfsf14, Tnfsf15, and Il1a, were closely correlated with the severity of HAdV-55 infection. Most of these genes belong to interleukin-1 family or tumor necrosis factor (TNF) superfamily, respectively. The changes in gene expression were confirmed by Western blot assay. Our data will be crucial for deepening the understanding of the pathogenic mechanisms of severe pneumonia in HAdV-55 infection.

Human adenovirus infections: update and consideration of mechanisms of viral persistence

PURPOSE OF REVIEW

To provide an update on recent studies of human adenoviral (HAdV) infections and to explore the mechanisms of viral persistence and the role of persistent infection in disseminated disease in immunocompromised patients.

RECENT FINDINGS

Human adenoviruses continue to be a problem in ophthalmology clinics and to cause periodic, limited, global outbreaks of respiratory disease. Ad14p1 remains in worldwide circulation and continues to result in miniepidemics of severe respiratory infections. New variants of Ad4 and Ad7 have emerged in both the United States and Asia. The severity of Ad4 infections in outbreaks appears to depend more on preexisting conditions in patients than on genetically determined, viral virulence factors, in contrast to limited evidence of Ad7 mutations that may convey increased viral pathogenesis. Reactivation of persistent adenovirus infection appears to be the primary source of disseminated infections in immunocompromised patients. New studies suggest that establishment of persistent infection and reactivation are related to variations in interferon-mediated control of viral replication.

SUMMARY

Innate immune responses can create a state of adenoviral persistence, and repression of these host defenses can result in reactivation and dissemination of infection. A better definition of the molecular mechanisms of immune-mediated control of viral replication might lead to new strategies for treatment of HAdV reactivation and dissemination.

Circulation of HAdV-41 with diverse genome types and recombination in acute gastroenteritis among children in Shanghai

Human adenovirus F (HAdV-F) is one of the major causative species detected in acute gastroenteritis in children worldwide. HAdV-F is composed of serotypes 40 and 41. Most studies have reported the prevalence of HAdV-41 and focused on its epidemiologic characteristics. In this study, seventeen samples were identified as HAdV-41 out of 273 fecal specimens from children with acute diarrhea in Shanghai. Five isolates were isolated and subjected to whole genome sequencing and analysis to characterize the genetic variation and evolution. Full genome analysis revealed low genetic variation (99.07-99.92% identity) among the isolates, and InDels are observed in the E2A gene and the hexon gene compared to the reference strain NIVD103. Phylogenetic analysis showed that all isolates mainly formed two genome-type clusters but with incongruence in the trees of whole genomes and individual genes. The recombination breakpoints of the five isolates were inferred by the Recombination Detection Program (RDP) and varied in the number and location of the recombination events, indicating different evolution origins. Overall, our study highlights the genetic diversity of HAdV-41 isolates circulating in Shanghai, which may have evolved from inter-strain recombination.

Respiratory DNA viruses are undetectable in nasopharyngeal secretions from adenotonsillectomized children

Respiratory viruses are frequently detected in association with chronic tonsillar hypertrophy in the absence of symptoms of acute respiratory infection (ARI). The present analysis was done in follow-up to a previous clinical study done by this same group. Nasopharyngeal washes (NPWs) were obtained from 83 of 120 individuals at variable times post adenotonsillectomy, in the absence of ARI symptoms. A look back at virus detection results in NPWs from the same 83 individuals at the time of tonsillectomy revealed that 73.5% (61/83) were positive for one or more viruses. The overall frequency of respiratory virus detection in post-tonsillectomy NPWs was 58.8%. Rhinovirus (RV) was the agent most frequently detected, in 38 of 83 subjects (45.8%), followed by enterovirus in 7 (8.4%), human metapneumovirus in 6 (7.2%), human respiratory syncytial virus in 3 (3.6%) and human coronavirus in 1 (1.2%). Remarkably, there was no detection of adenovirus (HAdV) or human bocavirus (HBoV) in asymptomatic individuals in follow-up of adenotonsillectomy. In keeping with persistence of respiratory DNA viruses in human tonsils, tonsillectomy significantly reduces asymptomatic shedding of HAdV and HBoV in NPWs.