Computational and serologic analysis of novel and known viruses in species human adenovirus D in which serology and genomics do not correlate

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

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

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.

Molecular typing of conjunctivitis-causing adenoviruses in Hanoi, Vietnam from 2017 to 2019 and complete genome analysis of the most prevalent type (HAdV-8)

Adenoviral conjunctivitis is a common epidemic worldwide. In Vietnam, up to 80,000 patients are infected with adenoviral conjunctivitis annually. However, there are few investigations on the pathogenic adenoviruses that cause conjunctivitis. In total, 120 eye-swab samples were collected from patients with viral conjunctivitis symptoms in Hanoi, Vietnam from 2017 to 2019. Human adenoviruse (HAdV) was detected in 67 samples (55.83%) using polymerase chain reaction amplification of at least one of three HAdV-specific marker genes (hexon, penton, and fiber). Of the 67 HAdV samples, 46 samples could be analyzed by all three marker genes. DNA sequence analysis and phylogenetic tree building based on the three marker genes from the 46 HAdV samples revealed five different HAdV types associated with conjunctivitis in Hanoi, including HAdV-3 (4.3%), HAdV-4 (2.2%), HAdV-8 (89.1%), HAdV-37 (2.2%), and a potential recombinant type between types HAdV-8 and HAdV-3 (2.2%). This showed that HAdV-8 was the most common type identified in Hanoi. Complete genome analysis of HAdV-8 isolated from a Vietnamese patient (VN2017) using Sanger sequencing revealed 34 unique nucleotide changes, indicating that the adenovirus continuously accumulates new mutations. Hence, continuous surveillance of HAdV-8 changes in Vietnam is necessary in the future.

Mystery eye: Human adenovirus and the enigma of epidemic keratoconjunctivitis

Known to occur in widespread outbreaks, epidemic keratoconjunctivitis (EKC) is a severe ocular surface infection with a strong historical association with human adenovirus (HAdV). While the conjunctival manifestations can vary from mild follicular conjunctivitis to hyper-acute, exudative conjunctivitis with formation of conjunctival membranes, EKC is distinct as the only form of adenovirus conjunctivitis in which the cornea is also involved, likely due to the specific corneal epithelial tropism of its causative viral agents. The initial development of a punctate or geographic epithelial keratitis may herald the later formation of stromal keratitis, and manifest as subepithelial infiltrates which often persist or recur for months to years after the acute infection has resolved. The chronic keratitis in EKC is associated with foreign body sensation, photophobia, glare, and reduced vision. However, over a century since the first clinical descriptions of EKC, and over 60 years since the first causative agent, human adenovirus type 8, was identified, our understanding of this disorder remains limited. This is underscored by a current lack of effective diagnostic tools and treatments. In part, stasis in our knowledge base has been encouraged by the continued acceptance, and indeed propagation of, inaccurate paradigms pertaining to disease etiology and pathogenesis, particularly with regard to mechanisms of innate and adaptive immunity within the cornea. Owing to its often persistent and medically refractory visual sequelae, reconsideration of key aspects of EKC disease biology is warranted to identify new treatment targets to curb its worldwide socioeconomic burden.

Genomic foundations of evolution and ocular pathogenesis in human adenovirus species D

Human adenovirus commonly causes infections of respiratory, gastrointestinal, genitourinary, and ocular surface mucosae. Although most adenovirus eye infections are mild and self-limited, specific viruses within human adenovirus species D are associated with epidemic keratoconjunctivitis (EKC), a severe and highly contagious ocular surface infection, which can lead to chronic and/or recurrent, visually disabling keratitis. In this review, we discuss the links between adenovirus ontogeny, genomics, immune responses, and corneal pathogenesis, for those viruses that cause EKC.

Comparative Genomic Analysis of Re-emergent Human Adenovirus Type 55 Pathogens Associated With Adult Severe Community-Acquired Pneumonia Reveals Conserved Genomes and Capsid Proteins

Human adenovirus type 55 (HAdV-B55) is a recently identified acute respiratory disease (ARD) pathogen in HAdV species B with a recombinant genome between renal HAdV-B11 and respiratory HAdV-B14. Since HAdV-B55 first appeared in China school in 2006, no more ARD cases associated with it had been reported until 2011, when there was an outbreak of adult severe community-acquired pneumonia (CAP) in Beijing, China. Reported here is the bioinformatics analysis of the re-emergent HAdV-B55 responsible for this outbreak. Recombination and protein sequence analysis re-confirmed that this isolate (BJ01) was a recombinant virus with the capsid hexon gene from HAdV-B11. The selection pressures for the three capsid proteins, i.e., hexon, penton base, and fiber genes, were all negative, along with very low non-synonymous (dN) and synonymous (dS) substitutions/site (<0.0007). Phylogenetic analyses of the whole genome and the three major capsid genes of HAdV-B55 revealed the close phylogenetic relationship among all HAdV-B55 strains. Comparative genomic analysis of this re-emergent HAdV-B55 strain (BJ01; 2011) with the first HAdV-B55 strain (QS-DLL; 2006) showed the high genome identity (99.87%), including 10 single-nucleotide non-synonymous substitutions, 11 synonymous substitutions, 3 insertions, and one deletion in non-coding regions. The major non-synonymous substitutions (6 of 10) occurred in the protein pVI in its L3 region, which protein has different functions at various stages of an adenovirus infection, and may be associated with the population distribution of HAdV-B55 infection. No non-synonymous substitutions were found in the three major capsid proteins, which proteins are responsible for type-specific neutralizing antibodies. Comparative genomic analysis of the re-emergent HAdV-B55 strains associated with adult severe CAP revealed conserved genome and capsid proteins, providing the foundation for the development of effective vaccines against this pathogen. This study also facilitates the further investigation of HAdV-B55 epidemiology, molecular evolution, patterns of pathogen emergence and re-emergence, and the predication of genome recombination between adenoviruses.

Adenovirus-associated acute conjunctivitis in Beijing, China, 2011-2013

BACKGROUND

Human adenovirus (HAdV)-associated acute conjunctivitis is a common infectious disease and causes significant morbidity among residents in Beijing, China. However, little is known about the epidemiology and type distribution of acute adenoviral conjunctivitis in Beijing.

METHODS

Acute conjunctivitis surveillance was conducted in 18 hospitals in Beijing from July through October during 2011-2013. HAdVs were detected by PCR from eye swab and types were determined by partial hexon and fiber gene sequencing. Risk factors associated with adenoviral conjunctivitis were analyzed.

RESULTS

Of 876 conjunctivitis cases, 349 (39.8%) were HAdV positive. HAdV detection was most common in conjunctivitis patients aged 18-40 years; patients with contact history with a conjunctivitis case; patients with specimen collected on days 4-6 post symptom onset and patients who worked in food service as catering attendants. Fifteen types were identified among adenoviral conjunctivitis cases. Five HAdV types (HAdV-4, - 37, - 53, - 64 and - 8) accounted for 81.1% of all adenoviral conjunctivitis cases. HAdV-37, - 4 and - 53 were the most common types associated with adenoviral conjunctivitis in 2011, 2012 and 2013, respectively.

CONCLUSION

Multiple HAdV types were associated with acute conjunctivitis in Beijing. Predominant types associated with adenoviral conjunctivitis circulating in Beijing varied from year to year.

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 infection in children with acute lower respiratory tract infections in Beijing, China, 2007 to 2012

Background

Human adenoviruses (HAdV) play a significant role in pediatric respiratory tract infections. To date, over 60 types of HAdV have been identified. Here, HAdV types are characterized in children in the Beijing area with acute lower respiratory tract infections (ALRTIs) and the clinical features and laboratory findings of hospitalized HAdV-infected cases are described.

Methods

Respiratory specimens were collected from pediatric patients with ALRTIs in the emergency department or from those admitted to Beijing Children’s Hospital between March 2007 and December 2012. Infections with common respiratory viruses were determined by PCR or RT-PCR. HAdV positive samples were further typed by PCR and sequencing.

Results

Among 3356 patients with ALRTIs, 194 (5.8 %) were found to have HAdV infection. HAdV infection was primarily confined to children (88.35 %) less than 5 years of age. A total of 11 different types of HAdV were detected throughout the study period, with HAdV-B7 (49.0 %) and HAdV-B3 (26.3 %) as the most prevalent types, followed by HAdV-C2 (7.7 %) and HAdVC1 (4.6 %). Newly emerging and re-emergent types or variants, HAdV-B55 (n = 5), HAdV-C57 (n = 3), and HAdV-B14p1 (n = 1), were identified. Results also included the reported first case of co-infection with HAdV-C2 and HAdV-C57. Clinical entities of patients with single HAdV infection (n = 49) were similar to those with mixed HAdV/respiratory syncytial virus (RSV) infections (n = 41). Patients with HAdV-B7 infection had longer duration of fever and higher serum levels of muscle enzymes than HAdV-B3-infected patients.

Conclusions

During the study period, HAdV-B7 and HAdV-B3 were the predominant types identified in pediatric ALRTIs. HAdV-B7 infection tends to have more severe clinical consequences. The presence of newly emerging types or variants and co-infection with different types of HAdV highlights the need for constant and close surveillance of HAdV infection.

Recombination of the epsilon determinant and corneal tropism: Human adenovirus species D types 15, 29, 56, and 69

Viruses within human adenovirus species D (HAdV-D) infect epithelia at essentially every mucosal site. Hypervariable loops 1 and 2 of the hexon capsid protein contain epitopes that together form the epsilon determinant for serum neutralization. We report our analyses comparing HAdV-D15, 29, 56, and the recently identified type 69, each with highly similar hexons and the same serum neutralization profile, but otherwise disparate genomes. Of these, only HAdV-D type 56 is associated with epidemic keratoconjunctivitis (EKC), a severe infection of ocular surface epithelium and underlying corneal stroma. In the mouse adenovirus keratitis model, all four viruses induced inflammation. However, HAdV-D56 entry into human corneal epithelial cells and fibroblasts in vitro dramatically exceeded that of the other three viruses. We conclude that the hexon epsilon determinant is not a prime contributor to corneal tropism.

Construction of new primer sets for corresponding to genetic evolution of human adenoviruses in major capsid genes through frequent recombination

A number of novel recombinant human adenoviruses (HAdVs) have recently been identified through sequencing of the complete genomes. The recombinant HAdV sequences share similarity with other types in the major capsid genes, namely the hexon, penton base, and fiber genes, implying recombination events, which may result in escape from the immune response and the acquisition of different organotropisms. Therefore, a surveillance system of HAdVs that considers the effect of frequent recombination on genetic evolution in these genes must be constructed. In this study, we designed new primer sets that can amplify the partial penton base and fiber genes from species HAdV-A to HAdV-F and proteotype HAdVs on the basis of sequence analyses, including previously reported primers that amplify loop 1 of the hexon. Phylogenetic analysis through sequencing with these primers correctly classified clinical HAdV isolates in loop 1 of the hexon gene, the Arg-Gly-Asp (RGD) loop of the penton base gene, and the knob of the fiber gene, which contain neutralizing, hemagglutination, and receptor binding epitopes associated with immunogenicity and tissue tropisms of HAdVs. This study contributes to the accumulation of correct information regarding genetic diversity and evolution in the worldwide HAdV surveillance.

A novel complex recombinant form of type 48-related human adenovirus species D isolated in Japan

Recently, new genotypes of human adenoviruses (HAdVs) have been reported and many of them have been found to be recombinant forms of different known types of HAdV species D (HAdV-D). The objective of this study was to document the evolutionary features of a novel isolate (HAdV_Chiba_E086/2012) obtained from the eye swab of a patient with conjunctivitis in Japan. Viral DNA was extracted from the isolate to sequence the whole genome by the Sanger method and aligned with available genome sequences of HAdV-Ds. The phylogenetic trees of the nucleotide sequences of the penton base, hexon, and fiber genes and the E3 region showed that HAdV_Chiba_E086/2012 is closest to HAdV genotype 65 (HAdV-GT65), HAdV-48, HAdV-GT60 and HAdV-22 at 98%, 99%, 95% and 98% identity, respectively, suggesting that this isolate is a novel recombinant form to be designated as P65H48F60. Further phylogenetic and recombination analyses of the genome alignment of the new isolate implied that nested recombination events involving HAdV-GT59, GT65, 48, GT60, 22, and some ancestral lineages or their close relatives have shaped its genome. These results showed that HAdV_Chiba_E086/2012 is the first HAdV-48-related HAdV found in Japan, which has the most complicated evolutionary history among the known HAdVs so far.

Adenovirus membrane penetration: Tickling the tail of a sleeping dragon

As is the case for nearly every viral pathogen, non-enveloped viruses (NEV) must maintain their integrity under potentially harsh environmental conditions while retaining the ability to undergo rapid disassembly at the right time and right place inside host cells. NEVs generally exist in this metastable state until they encounter key cellular stimuli such as membrane receptors, decreased intracellular pH, digestion by cellular proteases, or a combination of these factors. These stimuli trigger conformational changes in the viral capsid that exposes a sequestered membrane-perturbing protein. This protein subsequently modifies the cell membrane in such a way as to allow passage of the virion and accompanying nucleic acid payload into the cell cytoplasm. Different NEVs employ variations of this general pathway for cell entry (Moyer and Nemerow, 2011, Curr. Opin. Virol., 1, 44-49), however this review will focus on significant new knowledge obtained on cell entry by human adenovirus (HAdV).

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.

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.

Species D human adenovirus type 9 exhibits better virus-spread ability for antitumor efficacy among alternative serotypes

Species C human adenovirus serotype 5 (HAdV-C5) is widely used as a vector for cancer gene therapy, because it efficiently transduces target cells. A variety of HAdV-C5 vectors have been developed and tested in vitro and in vivo for cancer gene therapy. While clinical trials with HAdV-C5 vectors resulted in effective responses in many cancer patients, administration of HAdV-C5 vectors to solid tumors showed responses in a limited area. A biological barrier in tumor mass is considered to hinder viral spread of HAdV-C5 vectors from infected cells. Therefore, efficient virus-spread from an infected tumor cell to surrounding tumor cells is required for successful cancer gene therapy. In this study, we compared HAdV-C5 to sixteen other HAdV serotypes selected from species A to G for virus-spread ability in vitro. HAdV-D9 showed better virus-spread ability than other serotypes, and its viral progeny were efficiently released from infected cells during viral replication. Although the HAdV-D9 fiber protein contains a binding site for coxsackie B virus and adenovirus receptor (CAR), HAdV-D9 showed expanded tropism for infection due to human CAR (hCAR)-independent attachment to target cells. HAdV-D9 infection effectively killed hCAR-negative cancer cells as well as hCAR-positive cancer cells. These results suggest that HADV-D9, with its better virus-spread ability, could have improved therapeutic efficacy in solid tumors compared to HAdV-C5.

Prediction of B-Cell Epitopes in Listeriolysin O, a Cholesterol Dependent Cytolysin Secreted by Listeria monocytogenes

Listeria monocytogenes is a gram-positive, foodborne bacterium responsible for disease in humans and animals. Listeriolysin O (LLO) is a required virulence factor for the pathogenic effects of L. monocytogenes. Bioinformatics revealed conserved putative epitopes of LLO that could be used to develop monoclonal antibodies against LLO. Continuous and discontinuous epitopes were located by using four different B-cell prediction algorithms. Three-dimensional molecular models were generated to more precisely characterize the predicted antigenicity of LLO. Domain 4 was predicted to contain five of eleven continuous epitopes. A large portion of domain 4 was also predicted to comprise discontinuous immunogenic epitopes. Domain 4 of LLO may serve as an immunogen for eliciting monoclonal antibodies that can be used to study the pathogenesis of L. monocytogenes as well as develop an inexpensive assay.

Simian adenovirus type 35 has a recombinant genome comprising human and simian adenovirus sequences, which predicts its potential emergence as a human respiratory pathogen

Emergent human and simian adenoviruses (HAdVs) may arise from genome recombination. Computational analysis of SAdV type 35 reveals a genome comprising a chassis with elements mostly from two simian adenoviruses, SAdV-B21 and -B27, and regions of high sequence similarity shared with HAdV-B21 and HAdV-B16. Although recombination direction cannot be determined, the presence of these regions suggests prior infections of humans by an ancestor of SAdV-B35, and/or vice versa. Absence of this virus in humans may reflect non-optimal conditions for zoonosis or incomplete typing, e.g., limited epitope-based. The presence of both a critical viral replication element found in HAdV genomes and genes that are highly similar to ones in HAdVs suggest the potential to establish in a human host. This allows a prediction that this virus may be a nascent human respiratory pathogen. The recombination potential of human and simian adenovirus genomes should be considered in the use of SAdVs as vectors for gene delivery in humans.

Homologous recombination in E3 genes of human adenovirus species D

Genes within the E3 transcription unit of human adenoviruses modulate host immune responses to infection. A comprehensive genomics and bioinformatics analysis of the E3 transcription unit for 38 viruses within human adenovirus species D (HAdV-D) revealed distinct and surprising patterns of homologous recombination. Homologous recombination was identified in open reading frames for E3 CR1α, CR1β, and CR1γ, similar to that previously observed with genes encoding the three major structural capsid proteins, the penton base, hexon, and fiber.

Computational analysis of four human adenovirus type 4 genomes reveals molecular evolution through two interspecies recombination events

Computational analysis of human adenovirus type 4 (HAdV-E4), a pathogen that is the only HAdV member of species E, provides insights into its zoonotic origin and molecular adaptation. Its genome encodes a domain of the major capsid protein, hexon, from HAdV-B16 recombined into the genome chassis of a simian adenovirus. Genomes of two recent field strains provide a clue to its adaptation to the new host: recombination of a NF-I binding site motif, which is required for efficient viral replication, from another HAdV genome. This motif is absent in the chimpanzee adenoviruses and the HAdV-E4 prototype, but is conserved amongst other HAdVs. This is the first report of an interspecies recombination event for HAdVs, and the first documentation of a lateral partial gene transfer from a chimpanzee AdV. The potential for such recombination events are important when considering chimpanzee adenoviruses as candidate gene delivery vectors for human patients.

Genome sequence of human adenovirus type 55, a re-emergent acute respiratory disease pathogen in China

Human adenovirus type 55 (HAdV-B55) is an acute respiratory disease (ARD) pathogen first completely characterized in China (2006). This is a unique Trojan horse microbe with the virus neutralization attribute of a renal pathogen and the cell tropism and clinical attributes of a respiratory pathogen, bypassing herd immunity. It appeared to be an uncommon pathogen, with earlier putative, sporadic occurrences in Spain (1969) and Turkey (2004); these isolates were incompletely characterized using only two epitopes. Reported here is the genome of a second recent isolate (China, 2011), indicating that it may occur more frequently. The availability of this HAdV-B55 genome provides a foundation for studying adenovirus molecular evolution, the dynamics of epidemics, and patterns of pathogen emergence and re-emergence. These data facilitate studies to predict genome recombination between adenoviruses, as well as sequence divergence rates and hotspots, all of which are important for vaccine development and because HAdVs are used for epitope and/or gene delivery vectors.

Genome sequence of the first human adenovirus type 14 isolated in China

Emergent pathogens may be examined rapidly at high resolution on a molecular level using genomics, allowing an understanding of their evolution. China is a unique environment for studying pathogens, having a large, dense, and generally closed population. Human adenovirus type 14 (HAdV-14) was originally identified as an acute respiratory disease (ARD) pathogen in The Netherlands (1955), with a second isolation in England (1957). Since then, few reports of this virus appeared until an ARD pathogen with a similar genome caused multiple outbreaks in the United States (2006 to 2009). This report presents the first genome of HAdV-B14 isolated in China (2010). As China experienced two recent outbreaks of an emergent ARD pathogen, HAdV-B55, containing much of the HAdV-B14 genome, the availability of this HAdV-B14 sequence will facilitate studies of the epidemiology of these pathogens, as well as provide a foundation for studying adenovirus evolution and the genesis of emergent pathogens. These observations may be invaluable in predicting possible recombination between wild-type viruses and adenoviral gene delivery vectors, including adenovirus vaccines.