Comparative analysis of the genome organization of human adenovirus 11, a member of the human adenovirus species B, and the commonly used human adenovirus 5 vector, a member of species C

Identified risk factors for co-infection in hospitalized children infected with adenovirus in Hangzhou

This study aimed to describe the clinical manifestations of adenovirus infections and identify potential risk factors for co-infection with chlamydia, viruses and bacteria in hospitalised children from Hangzhou, China. From January to December 2019, the characteristics of hospitalised children infected with adenovirus at Hangzhou Children's Hospital and Zhejiang Xiaoshan Hospital were collected. The clinical factors related to co-infection with chlamydia, viruses and bacteria were assessed using multivariate logistic regression analyses. A total of 5989 children were infected with adenovirus, of which 573 were hospitalised for adenovirus infection. The severity of adenovirus respiratory infection was categorised as follows: mild (bronchiolitis, 73.6%), moderate (bronchopneumonia, 17.6%) or severe (pneumonia, 8.8%). Of the 573 children who were hospitalised, 280 presented with co-infection of chlamydia, viruses or bacteria, while the remaining 293 had only adenovirus infection. Multivariate stepwise logistic regression analyses indicated that elevated ferritin was associated with an increased risk of chlamydia co-infection (odds ratio (OR) 6.50; 95% confidence interval (CI) 1.56–27.11; P = 0.010). However, increased white blood cell (WBC) count was associated with a reduced risk of viral co-infection (OR 0.84; 95% CI 0.75–0.95; P = 0.006). The study indicated that co-infection with chlamydia could be affected by elevated ferritin levels. WBC levels could affect viral co-infection in hospitalised children infected with adenovirus.

Human adenoviruses in paediatric patients with respiratory tract infections in Beijing, China

Background

Human adenoviruse (HAdV) is a major pathogen of paediatric respiratory tract infections (RTIs). Mutation or recombination of HAdV genes may cause changes in its pathogenicity and transmission. We described the epidemiology and genotypic diversity of HAdV in hospitalized children with RTIs in Beijing, China.

Methods

Nasopharyngeal aspirates were collected from hospitalized children with RTIs from April 2018 to March 2019. HAdVs were detected by a quantitative real-time PCR, and the hexon gene was used for phylogenetic analysis.

Results

Among 1572 samples, 90 (5.72%) were HAdV-positive. The HAdV detection rate was highest in November and July. Among HAdV-positive children, 61.11% (55/90) were co-infected with other respiratory viruses, the most common of which were human respiratory syncytial virus and human rhinovirus. The main diagnosis was bronchopneumonia, most patient have cough and fever. Children with a high viral load were more likely to have a high fever (P = 0.041) and elevated WBC count (P = 0.000). Of 55 HAdV-positive specimens, HAdV-B (63.64%), HAdV-C (27.27%), and HAdV-E (9.09%) were main epidemic species. Phylogenetic analysis indicated that hexon sequences of three samples were on the same branch with the recombinant HAdV strain (CBJ113), which was circulating in Beijing since 2016.

Conclusion

The HAdV-B3 and HAdV-B7 are the main epidemic strains in Beijing, and the recombinant HAdV-C strain CBJ113 has formed an epidemic trend.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-021-01661-6.

Human Adenovirus Type 7 Infections in Hubei, China During 2018-2019: Epidemic Features and Genetic Characterization of the Detected Viruses

Human adenoviruses (HAdVs) type 7 can cause severe respiratory disease. During the period between December 2018 and August 2019, HAdV-7 infection was identified in 129 patients in Wuhan Children's Hospital, Hubei Province, China. Samples were collected from hospitalized children and metagenomic sequencing was applied to detect the HAdV infections. Hemophagocytic lymphohistiocystosis (HLH) related to HAdV infections was observed in some patients clinically and patients were divided into two groups based on this to test the differences among clinical indicators. Genome variation, in silico restriction endonuclease analysis (REA), and phylogenetic analyses were carried out to show the genome characterization of HAdV-7 in this study. It was found that many indicators, such as all blood routine indicators, in patients of the HLH group showed significant levels. In this study, REA revealed that HAdV-7 might belong to genome 7d and genome variation analysis displayed the stable genome of HAdV. HAdV-7 is an ongoing threat to the public, and global surveillance should be established.

Calcium Influx Caused by ER Stress Inducers Enhances Oncolytic Adenovirus Enadenotucirev Replication and Killing through PKCα Activation

Oncolytic viruses represent an emerging approach to cancer therapy. However, better understanding of their interaction with the host cancer cell and approaches to enhance their efficacy are needed. Here, we investigate the effect of chemically induced endoplasmic reticulum (ER) stress on the activity of the chimeric group B adenovirus Enadenotucirev, its closely related parental virus Ad11p, and the archetypal group C oncolytic adenovirus Ad5. We show that treatment of colorectal and ovarian cancer cell lines with thapsigargin or ionomycin caused an influx of Ca2+, leading to an upregulation in E1A transcript and protein levels. Increased E1A protein levels, in turn, increased levels of expression of the E2B viral DNA polymerase, genome replication, late viral protein expression, infectious virus particle production, and cell killing during Enadenotucirev and Ad11p, but not Ad5, infection. This effect was not due to the induction of ER stress, but rather the influx of extracellular Ca2+ and consequent increase in protein kinase C activity. These results underscore the importance of Ca2+ homeostasis during adenoviral infection, indicate a signaling pathway between protein kinase C and E1A, and raise the possibility of using Ca2+ flux-modulating agents in the manufacture and potentiation of oncolytic virotherapies.

Human adenovirus among hospitalized children with respiratory tract infections in Beijing, China, 2017-2018

BACKGROUND

Human adenoviruses (HAdVs) cause a wide range of diseases. However, the genotype diversity and epidemiological information relating to HAdVs among hospitalized children with respiratory tract infections (RTIs) is limited. Here, we describe the epidemiology and genotype distribution of HAdVs associated with RTIs in Beijing, China.

METHODS

Nasopharyngeal aspirates (NPA) were collected from hospitalized children with RTIs from April 2017 to March 2018. HAdVs were detected by a TaqMan-based quantitative real-time polymerase chain reaction (qPCR) assay, and the hexon gene was used for phylogenetic analysis. Epidemiological data were analyzed using statistical product and service solutions (SPSS) 21.0 software.

RESULTS

HAdV was detected in 72 (5.64%) of the 1276 NPA specimens, with most (86.11%, 62/72) HAdV-positives cases detected among children < 6 years of age. HAdV-B3 (56.06%, 37/66) and HAdV-C2 (19.70%, 13/66) were the most frequent. Of the 72 HAdV-infected cases, 27 (37.50%) were co-infected with other respiratory viruses, most commonly parainfluenza virus (12.50%, 9/72) and rhinovirus (9.72%, 7/72). The log number of viral load ranged from 3.30 to 9.14 copies per mL of NPA, with no significant difference between the HAdV mono- and co-infection groups. The main clinical symptoms in the HAdV-infected patients were fever and cough, and 62 (86.11%, 62/72) were diagnosed with pneumonia. Additionally, HAdVs were detected throughout the year with a higher prevalence in summer.

CONCLUSIONS

HAdV prevalence is related to age and season. HAdV-B and HAdV-C circulated simultaneously among the hospitalized children with RTIs in Beijing, and HAdV-B type 3 and HAdV-C type 2 were the most frequent.

An oncolytic adenovirus 11p vector expressing adenovirus death protein in the E1 region showed significant apoptosis and tumour-killing ability in metastatic prostate cells

The usefulness for cancer therapy of replication-competent adenoviral vectors expressing therapeutic genes from the E3 region has been evaluated, but few reports have described replication-competent adenoviruses with insertions at the E1 region in the full viral genome. We investigated in different prostate cancer cells the oncolytic efficacy of the replication-competent adenovirus 11p vectors expressing adenovirus death (RCAd11pADP) and red fluorescence (RCAd11pRFP) proteins from the upstream E1 region. ADP/RFP gene expression was 2-3 logs higher in PC3 and DU145 cells than in LNCaP and RWPE-1 cells. E1A protein expression in PC3 and DU145 cells was notably increased after infection with the RCAd11pADP or RCAd11pRFP vector compared with the Ad11pwt virus. Toxicity assays revealed 2-5-fold greater oncolytic effects of RCAd11pADP compared to Ad11pwt. Although all three viruses suppressed subcutaneous PC3 tumour growth in nude mice, RCAd11pRFP had greater oncolytic effects than did the Ad11pwt virus, and RCAd11pADP exhibited significant anti-tumour effects via apoptosis in a xenograft model. Interestingly, the apoptosis triggered by RCAd11pADP was markedly enhanced in comparison to that by the vector expressing ADP from E3 region. Taken together, our findings suggest that RCAd11pADP can potentially be used for the treatment of prostate metastases in clinical settings.

The possible origin of human adenovirus type 3: Evidence of natural genetic recombination between human and simian adenovirus

We determined a complete genome sequence of the Korean field strain, KUMC-62, of human adenovirus type 3 (HAdV-3) and performed comparative genome analyses. Interestingly HAdV-3 has a distinct genomic sequence for the fiber CDS region on average 62.46% of nucleotide sequence identity to other types of HAdV-B1, while remaining genomic region of HAdV-3 is very similar (on average 95.71% of nucleotide sequence identity) to other types of HAdV-B1. The blast results showed that the fiber CDS region of HAdV-3 exhibited the highest nucleotide sequence identity with that of simian adenovirus type 32 (SAdV-32), except other strains of HAdV-3. In the Simplot analysis, a potential recombination event was detected between HAdV-7 and SAdV-32, which might have created HAdV-3 in the past. These findings suggest that HAdV-3 highly likely was created by a natural inter-species recombination event between human and non-human primate AdVs.

Landscape of emerging and re-emerging infectious diseases in China: impact of ecology, climate, and behavior

For the past several decades, the infectious disease profile in China has been shifting with rapid developments in social and economic aspects, environment, quality of food, water, housing, and public health infrastructure. Notably, 5 notifiable infectious diseases have been almost eradicated, and the incidence of 18 additional notifiable infectious diseases has been significantly reduced. Unexpectedly, the incidence of over 10 notifiable infectious diseases, including HIV, brucellosis, syphilis, and dengue fever, has been increasing. Nevertheless, frequent infectious disease outbreaks/events have been reported almost every year, and imported infectious diseases have increased since 2015. New pathogens and over 100 new genotypes or serotypes of known pathogens have been identified. Some infectious diseases seem to be exacerbated by various factors, including rapid urbanization, large numbers of migrant workers, changes in climate, ecology, and policies, such as returning farmland to forests. This review summarizes the current experiences and lessons from China in managing emerging and re-emerging infectious diseases, especially the effects of ecology, climate, and behavior, which should have merits in helping other countries to control and prevent infectious diseases.

Yeast Surface-Displayed H5N1 Avian Influenza Vaccines

Highly pathogenic H5N1 avian influenza viruses pose a pandemic threat to human health. A rapid vaccine production against fast outbreak is desired. We report, herein, a paradigm-shift influenza vaccine technology by presenting H5N1 hemagglutinin (HA) to the surface of yeast. We demonstrated, for the first time, that the HA surface-presented yeast can be used as influenza vaccines to elicit both humoral and cell-mediated immunity in mice. The HI titer of antisera reached up to 128 in vaccinated mice. A high level of H5N1 HA-specific IgG1 and IgG2a antibody production was detected after boost immunization. Furthermore, we demonstrated that the yeast surface-displayed HA preserves its antigenic sites. It preferentially binds to both avian- and human-type receptors. In addition, the vaccine exhibited high cross-reactivity to both homologous and heterologous H5N1 viruses. A high level production of anti-HA antibodies was detected in the mice five months after vaccination. Finally, our animal experimental results indicated that the yeast vaccine offered complete protection of mice from lethal H5N1 virus challenge. No severe side effect of yeast vaccines was noted in animal studies. This new technology allows for rapid and large-scale production of influenza vaccines for prepandemic preparation.

Complete replication-competent adenovirus 11p vectors with E1 or E3 insertions show improved heat stability

Conventional adenovirus vectors harboring E1 or E3 deletions followed by the insertion of an exogenous gene show considerably reduced virion stability. Here, we report strategies to generate complete replication-competent Ad11p(RCAd11p) vectors that overcome the above disadvantage. A GFP cassette was successfully introduced either upstream of E1A or in the E3A region. The resulting vectors showed high expression levels of the hexon and E1genes and also strongly induced the cytopathic effect in targeted cells. When harboring oversized genomes, the RCAd11pE1 and RCAd11pE3 vectors showed significantly improved heat stability in comparison to Ad11pwt;of the three, RCAd11pE3 was the most tolerant to heat treatment. Electron microscopy showed that RCAd11pE3, RCAd11pE1, Ad11pwt, and Ad11pE1 Delmanifested dominant, moderate, minimum, or no full virus particles after heat treatment at 47°C for 5h. Our results demonstrated that both genome size and the insertion site in the viral genome affect virion stability.

Replication-competent human adenovirus 11p vectors can propagate in Vero cells

The use of continuous cell lines derived from the African green monkey kidney (AGMK) has led to major advances in virus vaccine development. However, to date, these cells have not been used to facilitate the creation of human adenoviruses because most human adenoviruses undergo abortive infections in them. Here, we report the susceptibility of AGMK-derived cells to adenovirus 11p (Ad11p) infection. First, we showed that CD46 molecules, which act as receptors for Ad11p, are expressed in AGMK cells. We then monitored Ad11p replication by measuring GFP expression as an indicator of viral transcription. We found that AGMK-derived cells were as capable as carcinoma cells at propagating full-length replication-competent Ad11p (RCAd11p) DNA. Of the AGMK cell lines tested, Vero cells had the greatest capacity for adenovirus production. Thus, AGMK cells can be used to evaluate RCAd11p-mediated gene delivery, and Vero cells can be used for the production of RCAd11pGFP vectors at relatively high yields.

Outbreak of acute respiratory disease caused by human adenovirus type 7 in a military training camp in Shaanxi, China

Outbreaks of ARD associated with HAdV have been reported in military populations in many countries. Here, we report an ARD outbreak caused by HAdV‐7 in a military training camp in Shaanxi Province, China, from February to March of 2012. Epidemic data and samples from the patients were collected, and viral nucleotides from samples and viral isolations were detected and sequenced. IgG and IgA antibodies against HAdV, and the neutralization antibodies against the viral strain isolated in this outbreak, were detected. Epidemiological study showed that all personnel affected were males with an average age of 19.1 years. Two peaks appeared on the epicurve and there was an 8‐day interval between peaks. Laboratory results of viral nucleotide detection carried out with clinical specimens were positive for HAdV (83.33%, 15/18). Further study through serum antibody assay, virus isolation and phylogenetic analysis showed that HAdV‐7 was the etiological agent responsible for the outbreak. IgA antibody began to appear on the 4th day after the onset and showed 100% positivity on the 8th day. The virus strain in the present outbreak was highly similar to the virus isolated in Hanzhong Shaanxi in 2009. We conclude that HAdV‐7 was the pathogen corresponding to the outbreak, and this is the first report of an ARD outbreak caused by HAdV‐7 in military persons in China. Vaccine development, as well as enhanced epidemiological and virological surveillance of HAdV infections in China should be emphasized.

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.

Case report: severe disseminated adenovirus infection in a neonate following water birth delivery

Adenovirus infections are a common cause of respiratory and enteric illnesses of late infancy and childhood. In neonates, adenovirus infections are rare, carrying a high morbidity and mortality rate. We present a case of infant who developed severe pneumonia and disseminated adenoviral infection following water birth delivery to a mother with gastroenteritis. The infant's infection was due to an adenovirus strain that has not been previously reported in neonates.

Modification of the early gene enhancer-promoter improves the oncolytic potency of adenovirus 11

Oncolytic adenoviruses based on serotype 5 (Ad5) have several shortcomings, including the downregulation of its receptor in cancer cells, high prevalence of neutralizing antibodies and hepatotoxicity. Another adenoviral serotype, Ad11, could overcome these obstacles. Here, we show that human cancer cell lines express higher levels of the Ad11 receptor CD46, resulting in much better infectivity than Ad5. Surprisingly, only 36% (9/25) of the cell lines were more sensitive to Ad11- than to Ad5-mediated cytotoxicity. Investigations revealed that it was the transcription of Ad11 E1A, not CD46 expression or virus infectivity, which determined the cell's sensitivity to Ad11 killing. Ad11 E1A mRNA levels have an effect on viral DNA replication, structural protein synthesis and infectious particle production. To test the hypothesis that increased E1A transcription would lead to improved Ad11 replication in Ad5-sensitive (but Ad11-less sensitive) cells, two Ad11 mutants (Ad11-Ad5-P and Ad11-Ad5-EP) were constructed where either the E1A promoter or enhancer-promoter, respectively, was replaced by that of Ad5. Ad11-Ad5-EP demonstrated increased E1A mRNA levels and replication, together with enhanced oncolytic potency in vitro and in vivo. This effect was found in both the Ad5-sensitive and Ad11-sensitive cancer cells, broadening the range of tumors that could be effectively killed by Ad11-Ad5-EP.

Unity and diversity in the human adenoviruses: exploiting alternative entry pathways for gene therapy

Human Ads (adenoviruses) have been extensively utilized for the development of vectors for gene transfer, as they infect many cell types and do not integrate their genome into host-cell chromosomes. In addition, they have been widely studied as cytolytic viruses, termed oncolytic adenoviruses in cancer therapy. Ads are non-enveloped viruses with a linear double-stranded DNA genome of 30–38 kb which encodes 30–40 genes. At least 52 human Ad serotypes have been identified and classified into seven species, A–G. The Ad capsid has icosahedral symmetry and is composed of 252 capsomers, of which 240 are located on the facets of the capsid and consist of a trimeric hexon protein and the remaining 12 capsomers, the pentons, are at the vertices and comprise the penton base and projecting fibre protein. The entry of Ads into human cells is a two-step process. In the first step, the fibre protein mediates a primary interaction with the cell, effectively tethering the virus particle to the cell surface via a cellular attachment protein. The penton base then interacts with cell-surface integrins, leading to virus internalization. This interaction of the fibre protein with a number of cell-surface molecules appears to be important in determining the tropism of adenoviruses. Ads from all species, except species B and certain serotypes of species D, utilize CAR (coxsackie and adenovirus receptor) as their primary cellular-attachment protein, whereas most species B Ads use CD46, a complement regulatory protein. Such species-specific differences, as well as adaptations or modifications of Ads required for applications in gene therapy, form the major focus of the present review.

The revolution in viral genomics as exemplified by the bioinformatic analysis of human adenoviruses

Over the past 30 years, genomic and bioinformatic analysis of human adenoviruses has been achieved using a variety of DNA sequencing methods; initially with the use of restriction enzymes and more currently with the use of the GS FLX pyrosequencing technology. Following the conception of DNA sequencing in the 1970s, analysis of adenoviruses has evolved from 100 base pair mRNA fragments to entire genomes. Comparative genomics of adenoviruses made its debut in 1984 when nucleotides and amino acids of coding sequences within the hexon genes of two human adenoviruses (HAdV), HAdV-C2 and HAdV-C5, were compared and analyzed. It was determined that there were three different zones (1-393, 394-1410, 1411-2910) within the hexon gene, of which HAdV-C2 and HAdV-C5 shared zones 1 and 3 with 95% and 89.5% nucleotide identity, respectively. In 1992, HAdV-C5 became the first adenovirus genome to be fully sequenced using the Sanger method. Over the next seven years, whole genome analysis and characterization was completed using bioinformatic tools such as blastn, tblastx, ClustalV and FASTA, in order to determine key proteins in species HAdV-A through HAdV-F. The bioinformatic revolution was initiated with the introduction of a novel species, HAdV-G, that was typed and named by the use of whole genome sequencing and phylogenetics as opposed to traditional serology. HAdV bioinformatics will continue to advance as the latest sequencing technology enables scientists to add to and expand the resource databases. As a result of these advancements, how novel HAdVs are typed has changed. Bioinformatic analysis has become the revolutionary tool that has significantly accelerated the in-depth study of HAdV microevolution through comparative genomics.

Applying genomic and bioinformatic resources to human adenovirus genomes for use in vaccine development and for applications in vector development for gene delivery

Technological advances and increasingly cost-effect methodologies in DNA sequencing and computational analysis are providing genome and proteome data for human adenovirus research. Applying these tools, data and derived knowledge to the development of vaccines against these pathogens will provide effective prophylactics. The same data and approaches can be applied to vector development for gene delivery in gene therapy and vaccine delivery protocols. Examination of several field strain genomes and their analyses provide examples of data that are available using these approaches. An example of the development of HAdV-B3 both as a vaccine and also as a vector is presented.

Genomic and bioinformatics analyses of HAdV-14p, reference strain of a re-emerging respiratory pathogen and analysis of B1/B2

Unlike other human adenovirus (HAdV) species, B is divided into subspecies B1 and B2. Originally this was partly based on restriction enzyme (RE) analysis. B1 members, except HAdV-50, are commonly associated with respiratory diseases while B2 members are rarely associated with reported respiratory diseases. Recently two members of B2 have been identified in outbreaks of acute respiratory disease (ARD). One, HAdV-14, has re-emerged after an apparent 52-year absence. Genomic analysis and bioinformatics data are reported for HAdV-14 prototype for use as a reference and to understand and counter its re-emergence. The data complement and extend the original criteria for subspecies designation, unique amongst the adenoviruses, and highlight differences between B1 and B2, representing the first comprehensive analysis of this division. These data also provide finer granularity into the pathoepidemiology of the HAdVs. Whole genome analysis uncovers heterogeneous identity structures of the hexon and fiber genes amongst the HAdV-14 and the B1/B2 subspecies, which may be important in prescient vaccine development. Analysis of cell surface proteins provides insight into HAdV-14 tropism, accounting for its role as a respiratory pathogen. This HAdV-14 prototype genome is also a reference for applications of B2 adenoviruses as vectors for vaccine development and gene therapy.

Outbreak of acute respiratory disease in China caused by B2 species of adenovirus type 11

An outbreak of acute respiratory tract infection occurred in Shanxi Province, China, from March to April 2006. Of the 254 patients affected by this outbreak, 247 patients were students of a senior high school; 1 of these patients died during the outbreak. Serological tests and blood culture revealed no evidence of bacterial infection. The results of direct reverse transcription-PCR or PCR performed with clinical specimens collected from the patients, including the sole patient who died, were positive for human adenoviruses (HAdVs) but negative for influenza virus, measles virus, rubella virus, mumps virus, parainfluenza virus, respiratory syncytial virus, and human enteroviruses. These findings were confirmed by enzyme-linked immunosorbent assay for HAdV immunoglobulin A, the conventional neutralization test, and viral isolation and identification. Sequencing of the entire hexon gene revealed that HdAV type 11a (HAdV-11a) belonging to the B2 species of HAdV was the etiological agent responsible for the outbreak. However, both the analysis of the phylogenetic relationship and the similarity plot indicated that the sequence of the 3' end of the hexon gene outside the hypervariable regions the HAdV-11a strain isolated in this outbreak may be a recombinant with the sequence of the HAdV-14 strain of species B2. Although isolates of HAdV species B2 seldom cause respiratory infections, they may pose a new global challenge with regard to acute respiratory diseases; this possibility cannot be overlooked and should be carefully considered. Hence, the need to establish and improve both epidemiological and virological surveillance of HAdV infections in China should be emphasized.

Directed evolution generates a novel oncolytic virus for the treatment of colon cancer

Background

Viral-mediated oncolysis is a novel cancer therapeutic approach with the potential to be more effective and less toxic than current therapies due to the agents selective growth and amplification in tumor cells. To date, these agents have been highly safe in patients but have generally fallen short of their expected therapeutic value as monotherapies. Consequently, new approaches to generating highly potent oncolytic viruses are needed. To address this need, we developed a new method that we term “Directed Evolution” for creating highly potent oncolytic viruses.

Methodology/Principal Findings

Taking the “Directed Evolution” approach, viral diversity was increased by pooling an array of serotypes, then passaging the pools under conditions that invite recombination between serotypes. These highly diverse viral pools were then placed under stringent directed selection to generate and identify highly potent agents. ColoAd1, a complex Ad3/Ad11p chimeric virus, was the initial oncolytic virus derived by this novel methodology. ColoAd1, the first described non-Ad5-based oncolytic Ad, is 2–3 logs more potent and selective than the parent serotypes or the most clinically advanced oncolytic Ad, ONYX-015, in vitro. ColoAd1's efficacy was further tested in vivo in a colon cancer liver metastasis xenograft model following intravenous injection and its ex vivo selectivity was demonstrated on surgically-derived human colorectal tumor tissues. Lastly, we demonstrated the ability to arm ColoAd1 with an exogenous gene establishing the potential to impact the treatment of cancer on multiple levels from a single agent.

Conclusions/Significance

Using the “Directed Evolution” methodology, we have generated ColoAd1, a novel chimeric oncolytic virus. In vitro, this virus demonstrated a >2 log increase in both potency and selectivity when compared to ONYX-015 on colon cancer cells. These results were further supported by in vivo and ex vivo studies. Furthermore, these results have validated this methodology as a new general approach for deriving clinically-relevant, highly potent anti-cancer virotherapies.

Silencing E1A mRNA by RNA interference inhibits adenovirus replication

The adenovirus family contains 51 human serotypes, and most human adenoviruses cause widespread respiratory tract infections. Adenovirus infections can result in severe complications in some cases, such as in adenovirus type 11 infection in immunocompromised patients. However, effective treatment methods for adenovirus infections are currently unavailable. This prompted the search for antiviral agents effective against adenovirus infections. In the present study, adenovirus E1A was targeted by RNA interference (RNAi) using synthetic small interfering RNAs (siRNAs) in an attempt to inhibit viral replication, since adenovirus E1A proteins are known to be involved in the transcriptional activation of the viral and cellular genes necessary for controlling the cell cycle and viral replication. The results indicated that the siRNAs effectively reduced the amount of adenovirus E1A mRNA and the levels of replicative intermediates. Additionally, siRNA-mediated gene silencing inhibited adenovirus replication by suppressing the E1A mRNA. These results suggest that the RNAi-mediated targeting of adenovirus E1A may have a potentially therapeutic effect in controlling adenovirus infections.

Comparative genomic analysis of two strains of human adenovirus type 3 isolated from children with acute respiratory infection in southern China

Human adenovirus type 3 (HAdV-3) is a causative agent of acute respiratory disease, which is prevalent throughout the world, especially in Asia. Here, the complete genome sequences of two field strains of HAdV-3 (strains GZ1 and GZ2) isolated from children with acute respiratory infection in southern China are reported (GenBank accession nos DQ099432 and DQ105654, respectively). The genomes were 35,273 bp (GZ1) and 35,269 bp (GZ2) and both had a G+C content of 51 mol%. They shared 99% nucleotide identity and the four early and five late regions that are characteristic of human adenoviruses. Thirty-nine protein- and two RNA-coding sequences were identified in the genome sequences of both strains. Protein pX had a predicted molecular mass of 8.3 kDa in strain GZ1; this was lower (7.6 kDa) in strain GZ2. Both strains contained 10 short inverted repeats, in addition to their inverted terminal repeats (111 bp). Comparative whole-genome analysis revealed 93 mismatches and four insertions/deletions between the two strains. Strain GZ1 infection produced a typical cytopathic effect, whereas strain GZ2 did not; non-synonymous substitutions in proteins of GZ2 may be responsible for this difference.

Protection of mice and poultry from lethal H5N1 avian influenza virus through adenovirus-based immunization

The recent emergence of highly pathogenic avian influenza virus (HPAI) strains in poultry and their subsequent transmission to humans in Southeast Asia have raised concerns about the potential pandemic spread of lethal disease. In this paper we describe the development and testing of an adenovirus-based influenza A virus vaccine directed against the hemagglutinin (HA) protein of the A/Vietnam/1203/2004 (H5N1) (VN/1203/04) strain isolated during the lethal human outbreak in Vietnam from 2003 to 2005. We expressed different portions of HA from a recombinant replication-incompetent adenoviral vector, achieving vaccine production within 36 days of acquiring the virus sequence. BALB/c mice were immunized with a prime-boost vaccine and exposed to a lethal intranasal dose of VN/1203/04 H5N1 virus 70 days later. Vaccination induced both HA-specific antibodies and cellular immunity likely to provide heterotypic immunity. Mice vaccinated with full-length HA were fully protected from challenge with VN/1203/04. We next evaluated the efficacy of adenovirus-based vaccination in domestic chickens, given the critical role of fowl species in the spread of HPAI worldwide. A single subcutaneous immunization completely protected chickens from an intranasal challenge 21 days later with VN/1203/04, which proved lethal to all control-vaccinated chickens within 2 days. These data indicate that the rapid production and subsequent administration of recombinant adenovirus-based vaccines to both birds and high-risk individuals in the face of an outbreak may serve to control the pandemic spread of lethal avian influenza.

Broad cellular immunity with robust memory responses to simian immunodeficiency virus following serial vaccination with adenovirus 5- and 35-based vectors

Adenovirus serotype 35 (Ad35) is a promising vaccine platform for human immunodeficiency virus (HIV) infection and emerging infectious diseases as it is uncommon in humans worldwide and is distinct from Ad5, the major vaccine serotype for which many individuals have pre-existing immunity. The immunogenicity of a first-generation, replication-competent Ad35-based vaccine was tested in the simian immunodeficiency virus (SIV) rhesus macaque model by evaluating its capacity to boost immunity generated by Ad5-based vectors. A series of four immunizations with replication-defective Ad5 vectors expressing SIVmac239 gag induced high-frequency responses mediated by both CD8+ and CD4+ T cells directed against several epitopes. Ad5-specific neutralizing antibody responses that did not neutralize Ad35 were rapidly induced but waned over time. Subsequent immunization with Ad5-based vectors was minimally effective, whereas immunization with Ad35-based vectors generated a strong increase in the frequency of Gag-specific T cells with specificities that were unchanged. While this boosting response was relatively transient, challenge with the distinct pathogenic isolate SIV/DeltaB670 generated robust and selective recall responses to Gag with similar specificities as induced by vaccination that were elevated for 25 weeks relative to controls. Vaccination had measurable albeit minor effects on virus load. Unexpectedly, regional hypervariability within the Gag sequence of SIV/DeltaB670 was associated with mutation of the conserved CD8+ T-cell epitope CM9 without concurrent flanking mutations and in the absence of immune pressure. These findings support the further development of Ad35 as a vaccine vector, and promote vaccine regimens that utilize serial administration of heterologous adenoviruses.

Fluorescently tagged canine adenovirus via modification with protein IX-enhanced green fluorescent protein

Canine adenovirus type 2 (CAV2) has become an attractive vector for gene therapy because of its non-pathogenicity and the lack of pre-existing neutralizing antibodies against this virus in the human population. Additionally, this vector has been proposed as a conditionally replicative adenovirus agent under the control of an osteocalcin promoter for evaluation in a syngeneic, immunocompetent canine model with spontaneous osteosarcoma. In this study, a CAV2 vector labelled with the fluorescent capsid fusion protein IX-enhanced green fluorescent protein (pIX-EGFP) was developed. Expression of the fluorescent fusion-protein label in infected cells with proper nuclear localization, and incorporation into virions, could be detected. The labelled virions could be visualized by fluorescence microscopy; this was applicable to the tracking of CAV2 infection, as well as localizing the distribution of the vector in tissues. Expression of pIX-EGFP could be exploited to detect the replication and spread of CAV2. These results indicate that pIX can serve as a platform for incorporation of heterologous proteins in the context of a canine adenovirus xenotype. It is believed that capsid-labelled CAV2 has utility for vector-development studies and for monitoring CAV2-based oncolytic adenovirus replication.

Respiratory disease caused by a species B2 adenovirus in a military camp in Turkey

In April 2004, two patients were admitted to hospital in Berlin, Germany, with clinical signs of acute respiratory infection after returning from a military exercise in their home country of Turkey. They were admitted to a high security infectious disease unit as epidemiological data pointed to an outbreak of unknown etiology. Samples taken at the time of admission proved to be strongly positive for Adenovirus by PCR, but negative for Influenza A/H1N1 virus, Influenza A/H3N2 virus, Influenza B virus, Respiratory syncytial virus, and SARS coronavirus. No evidence for bacterial infection was obtained by serological tests and blood cultures. The adenovirus detected was characterized further by genotyping and was identified as a species B2 virus with the highest similarity to adenovirus type 11a.

The nucleotide sequence and a first generation gene transfer vector of species B human adenovirus serotype 3

Human adenovirus (Ad) serotype 3 causes respiratory infections. It is considered highly virulent, accounting for about 13% of all Ad isolates. We report here the complete Ad3 DNA sequence of 35,343 base pairs (GenBank accession DQ086466). Ad3 shares 96.43% nucleotide identity with Ad7, another virulent subspecies B1 serotype, and 82.56 and 62.75% identity with the less virulent species B2 Ad11 and species C Ad5, respectively. The genomic organization of Ad3 is similar to the other human Ads comprising five early transcription units, E1A, E1B, E2, E3, and E4, two delayed early units IX and IVa2, and the major late unit, in total 39 putative and 7 hypothetical open reading frames. A recombinant E1-deleted Ad3 was generated on a bacterial artificial chromosome. This prototypic virus efficiently transduced CD46-positive rodent and human cells. Our results will help in clarifying the biology and pathology of adenoviruses and enhance therapeutic applications of viral vectors in clinical settings.

Characterization of a new species of adenovirus in falcons

In 1996, a disease outbreak occurred at a captive breeding facility in Idaho, causing anorexia, dehydration, and diarrhea or sudden death in 72 of 110 Northern aplomado falcons (Falco femoralis septentrionalis) from 9 to 35 days of age and in 6 of 102 peregrine falcons (Falco peregrinus) from 14 to 25 days of age. Sixty-two Northern aplomado and six peregrine falcons died. Epidemiologic analyses indicated a point source epizootic, horizontal transmission, and increased relative risk associated with cross-species brooding of eggs. Primary lesions in affected birds were inclusion body hepatitis, splenomegaly, and enteritis. The etiology in all mortalities was determined by molecular analyses to be a new species of adenovirus distantly related to the group I avian viruses, serotypes 1 and 4, Aviadenovirus. In situ hybridization and PCR demonstrated that the virus was epitheliotropic and lymphotropic and that infection was systemic in the majority of animals. Adeno-associated virus was also detected by PCR in most affected falcons, but no other infectious agents or predisposing factors were found in any birds. Subsequent to the 1996 epizootic, a similar disease caused by the same adenovirus was found over a 5-year period in orange-breasted falcons (Falco deiroleucus), teita falcons (Falco fasciinucha), a merlin (Falco columbarius), a Vanuatu peregrine falcon (Falco peregrinus nesiotes), and gyrfalcon x peregrine falcon hybrids (Falco rusticolus/peregrinus) that died in Wyoming, Oklahoma, Minnesota, and California. These findings indicate that this newly recognized adenovirus is widespread in western and midwestern North America and can be a primary pathogen in different falcon species.

Human cytomegalovirus pp71: a new viral tool to probe the mechanisms of cell cycle progression and oncogenesis controlled by the retinoblastoma family of tumor suppressors

The DNA tumor virus oncogenes (adenovirus E1A, simian virus 40 (SV40) large T antigen, and papillomavirus E7) have been instrumental in illuminating the molecules and mechanisms of cell cycle progression and carcinogenesis. However, since these multifunctional proteins target so many important cellular regulators, it is sometimes difficult to establish the functional importance of any individual interaction. Perhaps a herpesvirus protein, newly defined as a cell cycle regulator, can help address these issues. Like the DNA tumor virus proteins, the human cytomegalovirus (HCMV) pp71 protein contains a retinoblastoma protein (Rb) binding motif (LxCxD), and stimulates DNA synthesis in quiescent cells. Unlike E1A, T antigen, and E7, pp71 expression does not induce apoptosis, nor does it cooperate to transform primary cells. Determining how pp71 induces cell cycle progression without invoking apoptosis or leading to cellular transformation may help in defining the signals that ultimately lead to these processes.

Novel replication-incompetent vector derived from adenovirus type 11 (Ad11) for vaccination and gene therapy: low seroprevalence and non-cross-reactivity with Ad5

A novel plasmid-based adenovirus vector system that enables manufacturing of replication-incompetent (DeltaE1) adenovirus type 11 (Ad11)-based vectors is described. Ad11 vectors are produced on PER.C6/55K cells yielding high-titer vector batches after purification. Ad11 seroprevalence proves to be significantly lower than that of Ad5, and neutralizing antibody titers against Ad11 are low. Ad11 seroprevalence among human immunodeficiency virus-positive (HIV(+)) individuals is as low as that among HIV(-) individuals, independent of the level of immune suppression. The low level of coinciding seroprevalence between Ad11 and Ad35 in addition to a lack of correlation between high neutralizing antibody titers towards either adenovirus strongly suggest that the limited humoral cross-reactive immunity between these two highly related B viruses appears not to preclude the use of both vectors in the same individual. Ad11 transduces primary cells including smooth muscle cells, synoviocytes, and dendritic cells and cardiovascular tissues with higher efficiency than Ad5. Ad11 and Ad35 appear to have a similar tropism as judged by green fluorescent protein expression levels determined by using a panel of cancer cell lines. In addition, Ad5 preimmunization did not significantly affect Ad11-mediated transduction in C57BL/6 mice. We therefore conclude that the Ad11-based vector represents a novel and useful candidate gene transfer vehicle for vaccination and gene therapy.

Analysis of the first complete genome sequence of an Old World monkey adenovirus reveals a lineage distinct from the six human adenovirus species

Simian adenovirus 3 (SAdV-3) is one of several adenoviruses that were isolated decades ago from Old World monkeys. Determination of the complete DNA sequence of SAdV-3 permitted the first full genomic comparison of a monkey adenovirus with adenoviruses of humans (HAdVs) and chimpanzees, which are recognized formally as constituting six of the species (HAdV-A to HAdV-F) within the genus Mastadenovirus. The SAdV-3 genome is 34 246 bp in size and has a G+C content of 55.3 mol%. It contains all the genes that are characteristic of the genus Mastadenovirus and has a single VA-RNA gene and six genes in each of the E3 and E4 regions. The genetic organization is the same as that of HAdV-12, a member of the HAdV-A species. Phylogenetic analyses showed that although SAdV-3 is related marginally more closely to HAdV-A and HAdV-F than to other species, it represents a unique lineage that branched at an early stage of primate adenovirus divergence. The results imply that the genetic layout in SAdV-3 and HAdV-12 may also have characterized the common ancestor of all sequenced primate adenoviruses.

Natural variation among human adenoviruses: genome sequence and annotation of human adenovirus serotype 1

The 36,001 base pair DNA sequence of human adenovirus serotype 1 (HAdV-1) has been determined, using a 'leveraged primer sequencing strategy' to generate high quality sequences economically. This annotated genome (GenBank AF534906) confirms anticipated similarity to closely related species C (formerly subgroup), human adenoviruses HAdV-2 and -5, and near identity with earlier reports of sequences representing parts of the HAdV-1 genome. A first round of HAdV-1 sequence data acquisition used PCR amplification and sequencing primers from sequences common to the genomes of HAdV-2 and -5. The subsequent rounds of sequencing used primers derived from the newly generated data. Corroborative re-sequencing with primers selected from this HAdV-1 dataset generated sparsely tiled arrays of high quality sequencing ladders spanning both complementary strands of the HAdV-1 genome. These strategies allow for rapid and accurate low-pass sequencing of genomes. Such rapid genome determinations facilitate the development of specific probes for differentiation of family, serotype, subtype and strain (e.g. pathogen genome signatures). These will be used to monitor epidemic outbreaks of acute respiratory disease in a defined test bed by the Epidemic Outbreak Surveillance (EOS) project.

Bovine adenovirus type 3 containing heterologous protein in the C-terminus of minor capsid protein IX

Earlier, we detected pIX of BAdV-3 as a 14-kDa protein in purified virions. Analysis of BAdV-3 pIX using different region antibodies revealed that the N-terminus and central domain of the pIX contain immunogenic sites and are not exposed on the surface of BAdV-3 virion. This suggested that the C-terminus of BAdV-3 pIX (125 amino acid) may be exposed on the virion and may be used as a site for incorporation of heterologous peptides or proteins. We constructed recombinant BAV950 containing a small peptide (21 amino acid), including the RGD motif or recombinant BAV951 containing enhanced yellow-green fluorescent protein (EYFP) fused to the C-terminus of pIX. Western blot analysis demonstrated that the chimeric pIX-RGD was incorporated into virion capsids. Incorporation of the RGD motif into the pIX resulted in significant augmentation of BAdV-3 fiber knob-independent infection of the integrin-positive cells, suggesting that RGD motifs are displayed on the surface of virion capsids and are accessible for binding to integrins. Analysis of BAV951 revealed that the chimeric pIX is incorporated into virion capsids and EYFP containing the C-terminus of pIX is exposed on the surface of the virion. Moreover, insertion of chimeric pIXs was maintained without change through successive rounds of viral replication. These results suggested that in contrast to major capsid proteins (hexon, penton, fiber), the minor capsid protein IX can be use for the incorporation of targeting ligands based on either small peptides or longer polypeptides.

Genetic content and evolution of adenoviruses

This review provides an update of the genetic content, phylogeny and evolution of the family Adenoviridae. An appraisal of the condition of adenovirus genomics highlights the need to ensure that public sequence information is interpreted accurately. To this end, all complete genome sequences available have been reannotated. Adenoviruses fall into four recognized genera, plus possibly a fifth, which have apparently evolved with their vertebrate hosts, but have also engaged in a number of interspecies transmission events. Genes inherited by all modern adenoviruses from their common ancestor are located centrally in the genome and are involved in replication and packaging of viral DNA and formation and structure of the virion. Additional niche-specific genes have accumulated in each lineage, mostly near the genome termini. Capture and duplication of genes in the setting of a 'leader-exon structure', which results from widespread use of splicing, appear to have been central to adenovirus evolution. The antiquity of the pre-vertebrate lineages that ultimately gave rise to the Adenoviridae is illustrated by morphological similarities between adenoviruses and bacteriophages, and by use of a protein-primed DNA replication strategy by adenoviruses, certain bacteria and bacteriophages, and linear plasmids of fungi and plants.