Modeling adenovirus latency in human lymphocyte cell lines

Epidemiological and clinical characteristics of adenovirus-associated respiratory tract infection in children in Hangzhou, China, 2019-2024

This study aimed to assess the impact of COVID-19 on the prevalence of adenovirus (AdV) infection in children. This study retrospectively analyzed the changes in the epidemiological and clinical features of AdV-associated respiratory infections in children in Hangzhou, China, between January 2019 and July 2024. A total of 771 316 samples were included in the study, and the positive rate was 6.10% (47 050/771 316). Among them, the positive rate of AdV infection was highest in 2019, reaching 11.29% (26 929/238 333), while the positive rates in the remaining years were between 2% and 9%. In terms of seasonal epidemic characteristics, the summer of 2019 was the peak of AdV incidence, with the positive rate peaking at around 16.95% (7275/45 268), followed by a gradual decline and a low-level epidemic in winter, with a positive rate of 8.79% (8094/92 060). However, during the period 2020-2024, the AdV epidemic season did not show any significant regularity. Gender analysis revealed that the positive rate of male patients was generally greater than that of female patients. In different age groups, the population susceptible to AdV changed before and after the epidemic. In the early and middle stages of the COVID-19 epidemic, the susceptible population was mainly 2-5 years old, whereas in the later stages of the epidemic, the susceptible population was 5-18 years old. In addition, the main clinical symptoms of AdV-positive children from 2019-2024 were respiratory tract symptoms and fever. In summary, the COVID-19 epidemic has had a certain impact on the prevalence of AdV. These findings provide an important basis and reference for the prevention and diagnosis of AdV, especially in the context of increasing age- and gender-specific public health strategies.

Treatment with oncolytic vaccinia virus infects tumor-infiltrating regulatory and exhausted T cells

BACKGROUND

Oncolytic viruses (OVs) are an attractive way to increase immune infiltration into an otherwise cold tumor. While OVs are engineered to selectively infect tumor cells, there is evidence that they can infect other non-malignant cells in the tumor. We sought to determine if oncolytic vaccinia virus (VV) can infect lymphocytes in the tumor and, if so, how this was linked to therapeutic efficacy.

METHODS

To investigate infection of lymphocytes by VV, we used a GFP reporting VV in a murine head and neck squamous cell carcinoma tumor model. We also performed in vitro infection studies to determine the mechanism and consequences of VV lymphocyte infection by VV.

RESULTS

Our findings show that VV carries the capacity to infect proportions of immune cells, most notably T cells, after intratumoral treatment. Notably, this infection is preferential to terminally differentiated T cells that tend to reside in hypoxia. Infection of T cells leads to both virus production by the T cells as well as the eventual death of these cells. Using a mouse model which overexpressed the antiapoptotic protein Bcl2 in all T cells, we found that reducing T cell death following VV infection in MEER tumors reduced the number of complete regressions and reduced survival time compared with littermate control mice.

CONCLUSIONS

These findings suggest that OVs are capable of infecting more than just malignant cells after treatment, and that this infection may be an important part of the OV mechanism. We found that exhausted CD8+ T cells and regulatory CD4+ T cells were preferentially infected at early timepoints after treatment and subsequently died. When cell death in T cells was mitigated, mice responded poorly to VV treatment, suggesting that the deletion of these populations is critical to the therapeutic response to VV.

Adenoviruses in medicine: innocuous pathogen, predator, or partner

The consequences of human adenovirus (HAdV) infections are generally mild. However, despite the perception that HAdVs are harmless, infections can cause severe disease in certain individuals, including newborns, the immunocompromised, and those with pre-existing conditions, including respiratory or cardiac disease. In addition, HAdV outbreaks remain relatively common events and the recent emergence of more pathogenic genomic variants of various genotypes has been well documented. Coupled with evidence of zoonotic transmission, interspecies recombination, and the lack of approved AdV antivirals or widely available vaccines, HAdVs remain a threat to public health. At the same time, the detailed understanding of AdV biology garnered over nearly 7 decades of study has made this group of viruses a molecular workhorse for vaccine and gene therapy applications.

Mouse Adenovirus Type 1 Persistence Exacerbates Inflammation Induced by Allogeneic Bone Marrow Transplantation

Bone marrow transplantation (BMT) recipients are at risk for substantial morbidity and mortality from human adenovirus infections, often in the setting of reactivation of persistent virus. Human adenovirus persistence in mucosal lymphocytes has been described, but specific cellular reservoirs of persistence and effects of persistence on host responses to unrelated stimuli are not completely understood. We used mouse adenovirus type 1 (MAV-1) to characterize persistence of an adenovirus in its natural host and test the hypothesis that persistence increases complications of bone marrow transplantation (BMT). Following intranasal infection of C57BL/6J mice, MAV-1 DNA was detected in lung, mediastinal lymph nodes, and liver during acute infection at 7 days post infection (dpi), and at lower levels at 28 dpi that remained stable through 150 dpi. Expression of early and late viral transcripts was detected in those organs at 7 dpi but not at later time points. MAV-1 persistence was not affected by deficiency of IFN-γ. We detected no evidence of MAV-1 reactivation in vivo following allogeneic BMT of persistently infected mice. Persistent infection did not substantially affect mortality, weight loss, or pulmonary inflammation following BMT. However, T cell infiltration and increased expression of pro-inflammatory cytokines consistent with graft-versus-host disease (GVHD) were more pronounced in livers of persistently infected BMT mice than in uninfected BMT mice. These results suggest that MAV-1 persists in multiple sites without detectable evidence of ongoing replication. Our results indicate that MAV-1 persistence alters host responses to an unrelated challenge, even in the absence of detectable reactivation. Importance Long-term persistence in an infected host is an essential step in the life cycle of DNA viruses. Adenoviruses persist in their host following acute infection, but the nature of adenovirus persistence remains incompletely understood. Following intranasal infection of mice, we found that MAV-1 persists for a prolonged period in multiple organs, although we did not detect evidence of ongoing replication. Because BMT recipients are at risk for substantial morbidity and mortality from human adenovirus infections, often in the setting of reactivation of persistent virus in the recipient, we extended our findings using MAV-1 infection in a mouse model of BMT. MAV-1 persistence exacerbated GVHD-like inflammation following allogeneic BMT, even in the absence of virus reactivation. This novel finding suggests that adenovirus persistence has consequences, and it highlights the potential for a persistent adenovirus to influence host responses to unrelated challenges.

Association between adenovirus infection and mortality outcome among pediatric patients after hematopoietic stem cell transplant

BACKGROUND

Adenovirus can cause severe diseases in post-hematopoietic stem cell transplant (HSCT) patients. Because these patients also have many other factors contributing to mortality, it remains controversial whether adenovirus infection itself contributes to increased mortality in these patients.

OBJECTIVE

To determine if adenovirus infection contributes to mortality in pediatric post-HSCT patients.

METHODS

This retrospective cohort study was performed in post HSCT patients, aged 0-18 years old, admitted at Ramathibodi Hospital from 2016 to 2020. Adenovirus infection was defined as the detection of adenovirus in blood or urine by polymerase chain reaction. Multivariate cox regression was used to identify factors associated with death.

RESULTS

The incidence of overall adenovirus infection (viremia or viruria) in this cohort was 20.8% (26 out of 125 enrolled patients). From the multivariate cox regression analysis, overall adenovirus infection was not significantly associated with death (hazard ratio [HR]: 2.41; 95% confidence interval [CI]: 0.96-6.06; p = .060). However, presence of viremia (HR: 3.90; 95% CI: 1.40-10.86; p = .009), having maximal serum viral load > 10 000 copies/ml (HR: 3.70; 95% CI: 1.20-11.38; p = .023), presence of end-organ diseases (HR: 3.44; 95% CI: 1.18-10.01; p = .023) were associated with mortality. Underlying diseases requiring long-term immunosuppressive drugs before HSCT, invasive fungal disease, invasive bacterial infection, cytomegalovirus infection, and longer engraftment time were also associated with mortality.

CONCLUSION

Overall adenovirus infection does not appear to play a significant role in mortality in pediatric post-HSCT patients. However, more invasive forms of adenovirus infection were associated with mortality in these patients.

A Novel Adenovirus Detected in Bering-Chukchi-Beaufort Seas Bowhead Whale (Balaena mysticetus): Epidemiologic Data and Phylogenetic Characterization

Adenoviruses are common pathogens infecting a wide range of vertebrates. Few cetacean adenoviruses have been described in the literature, and their pathogenicity is still unclear. Using PCR-based viral and bacterial pathogen surveillance in Bering-Chukchi-Beaufort seas bowhead whales (Balaena mysticetus) legally harvested 2012-15 during Alaskan aboriginal subsistence hunts, six of 59 bowhead whales (10%) tested positive for adenovirus DNA in the spleen. We found a high degree of sequence divergence from other mastadenoviruses, suggesting these may represent a novel species, tentatively named bowhead whale adenovirus. The sequences detected are distinct from adenoviruses previously identified in bottlenose dolphins (Tursiops truncatus) and harbor porpoises (Phocoena phocoena), forming two distinct clades in the cetacean hosts. The clinical impact is unclear, since no histopathologic evidence of adenovirus-associated disease was found. Furthermore, detection of adenovirus DNA in the spleen, contrary to other cetacean adenoviruses detected in the intestinal tract, may suggest a broader tissue tropism. Our study demonstrates adenovirus infection in bowhead whales and the usefulness of molecular diagnostics to discover and genetically characterize novel viruses in marine mammals.

Infection of Bronchial Epithelial Cells by the Human Adenoviruses A12, B3, and C2 Differently Regulates the Innate Antiviral Effector APOBEC3B

Human adenoviruses (HAdVs) are a large family of DNA viruses that include more than 100 genotypes divided into seven species (A to G) and induce respiratory tract infections, gastroenteritis, and conjunctivitis. Genetically modified adenoviruses are also used as vaccines, gene therapies, and anticancer treatments. The APOBEC3s are a family of cytidine deaminases that restrict viruses by introducing mutations in their genomes. Viruses developed different strategies to cope with the APOBEC3 selection pressure, but nothing is known on the interplay between the APOBEC3s and the HAdVs. In this study, we focused on three HAdV strains: the B3 and C2 strains, as they are very frequent, and the A12 strain, which is less common but is oncogenic in animal models. We demonstrated that the three HAdV strains induce a similar APOBEC3B upregulation at the transcriptional level. At the protein level, however, APOBEC3B is abundantly expressed during HAdV-A12 and -C2 infection and shows a nuclear distribution. On the contrary, APOBEC3B is barely detectable in HAdV-B3-infected cells. APOBEC3B deaminase activity is detected in total protein extracts upon HAdV-A12 and -C2 infection. Bioinformatic analysis demonstrates that the HAdV-A12 genome bears a stronger APOBEC3 evolutionary footprint than that of the HAdV-C2 and HAdV-B3 genomes. Our results show that HAdV infection triggers the transcriptional upregulation of the antiviral innate effector APOBEC3B. The discrepancies between the APOBEC3B mRNA and protein levels might reflect the ability of some HAdV strains to antagonize the APOBEC3B protein. These findings point toward an involvement of APOBEC3B in HAdV restriction and evolution. IMPORTANCE The APOBEC3 family of cytosine deaminases has important roles in antiviral innate immunity and cancer. Notably, APOBEC3A and APOBEC3B are actively upregulated by several DNA tumor viruses and contribute to transformation by introducing mutations in the cellular genome. Human adenoviruses (HAdVs) are a large family of DNA viruses that cause generally asymptomatic infections in immunocompetent adults. HAdVs encode several oncogenes, and some HAdV strains, like HAdV-A12, induce tumors in hamsters and mice. Here, we show that HAdV infection specifically promotes the expression of the APOBEC3B gene. We report that infection with the A12 strain induces a strong expression of an enzymatically active APOBEC3B protein in bronchial epithelial cells. We provide bioinformatic evidence that HAdVs' genomes and notably the A12 genome are under APOBEC3 selection pressure. Thus, APOBEC3B might contribute to adenoviral restriction, diversification, and oncogenic potential of particular strains.

Adenoviral Vector DNA- and SARS-CoV-2 mRNA-Based Covid-19 Vaccines: Possible Integration into the Human Genome - Are Adenoviral Genes Expressed in Vector-based Vaccines?

Vigorous vaccination programs against SARS-CoV-2-causing Covid-19 are the major chance to fight this dreadful pandemic. The currently administered vaccines depend on adenovirus DNA vectors or on SARS-CoV-2 mRNA that might become reverse transcribed into DNA, however infrequently. In some societies, people have become sensitized against the potential short- or long-term side effects of foreign DNA being injected into humans. In my laboratory, the fate of foreign DNA in mammalian (human) cells and organisms has been investigated for many years. In this review, a summary of the results obtained will be presented. This synopsis has been put in the evolutionary context of retrotransposon insertions into pre-human genomes millions of years ago. In addition, studies on adenovirus vector-based DNA, on the fate of food-ingested DNA as well as the long-term persistence of SARS-CoV-2 RNA/DNA will be described. Actual integration of viral DNA molecules and of adenovirus vector DNA will likely be chance events whose frequency and epigenetic consequences cannot with certainty be assessed. The review also addresses problems of remaining adenoviral gene expression in adenoviral-based vectors and their role in side effects of vaccines. Eventually, it will come down to weighing the possible risks of genomic insertions of vaccine-associated foreign DNA and unknown levels of vector-carried adenoviral gene expression versus protection against the dangers of Covid-19. A decision in favor of vaccination against life-threatening disease appears prudent. Informing the public about the complexities of biology will be a reliable guide when having to reach personal decisions about vaccinations.

Boosting CAR T-cell responses in lymphoma by simultaneous targeting of CD40/4-1BB using oncolytic viral gene therapy

Pretreatment of B-cell lymphoma patients with immunostimulatory gene therapy using armed oncolytic viruses may prime tumor lesions for subsequent chimeric antigen receptor (CAR) T-cell therapy, thereby enhancing CAR T-cell functionality and possibly increasing response rates in patients. LOAd703 (delolimogene mupadenorepvec) is an oncolytic adenovirus (serotype 5/35) that encodes for the transgenes CD40L and 4-1BBL, which activate both antigen-presenting cells and T cells. Many adenoviruses failed to demonstrate efficacy in B-cell malignancies, but LOAd703 infect cells via CD46, which enables B cell infection. Herein, we investigated the therapeutic potential of LOAd703 in human B-cell lymphoma models, alone or in combination with CAR T-cell therapy. LOAd703 could infect and replicate in B-cell lymphoma cell lines (BC-3, Karpas422, Daudi, DG-75, U-698) and induced an overall enhanced immunogenic profile with upregulation of co-stimulatory molecules CD80, CD86, CD70, MHC molecules, death receptor Fas and adhesion molecule ICAM-1. Further, CAR T-cell functionality was boosted by stimulation with lymphoma cells infected with LOAd703. This was demonstrated by an augmented release of IFN-γ and granzyme B, increased expression of the degranulation marker CD107a, fewer PD-1 + TIM-3+ CAR T cells in vitro and enhanced lymphoma cell killing both in in vitro and in vivo xenograft models. In addition, LOAd703-infected lymphoma cells upregulated the secretion of several chemokines (CXCL10, CCL17, CCL22, CCL3, CCL4) essential for immune cell homing, leading to enhanced CAR T-cell migration. In conclusion, immunostimulatory LOAd703 therapy is an intriguing approach to induce anti-lymphoma immune responses and to improve CAR T-cell therapy in B-cell lymphoma.

Role of CCCH-Type Zinc Finger Proteins in Human Adenovirus Infections

The zinc finger proteins make up a significant part of the proteome and perform a huge variety of functions in the cell. The CCCH-type zinc finger proteins have gained attention due to their unusual ability to interact with RNA and thereby control different steps of RNA metabolism. Since virus infections interfere with RNA metabolism, dynamic changes in the CCCH-type zinc finger proteins and virus replication are expected to happen. In the present review, we will discuss how three CCCH-type zinc finger proteins, ZC3H11A, MKRN1, and U2AF1, interfere with human adenovirus replication. We will summarize the functions of these three cellular proteins and focus on their potential pro- or anti-viral activities during a lytic human adenovirus infection.

Synthesis, Structure, and Function of Human Adenovirus Small Non-Coding RNAs

Human adenoviruses (HAdVs) are common pathogens causing a variety of respiratory, ocular and gastrointestinal diseases. To accomplish their efficient replication, HAdVs take an advantage of viral small non-coding RNAs (sncRNAs), which have multiple roles during the virus lifecycle. Three of the best-characterized HAdV sncRNAs; VA RNA, mivaRNA and MLP-TSS-sRNA will be discussed in the present review. Even though VA RNA has been extensively characterized during the last 60 years, this multifunctional molecule continues to surprise us as more of its structural secrets unfold. Likely, the recent developments on mivaRNA and MLP-TSS-sRNA synthesis and function highlight the importance of these sncRNA in virus replication. Collectively, we will summarize the old and new knowledge about these three viral sncRNAs with focus on their synthesis, structure and functions.

The Adenovirus Death Protein - a small membrane protein controls cell lysis and disease

Human adenoviruses (HAdVs) cause widespread acute and persistent infections. Infections are usually mild and controlled by humoral and cell-based immunity. Reactivation of persistently infected immune cells can lead to a life-threatening disease in immunocompromised individuals, especially children and transplant recipients. To date, no effective therapy or vaccine against HAdV disease is available to the public. HAdV-C2 and C5 are the best-studied of more than 100 HAdV types. They persist in infected cells and release their progeny by host cell lysis to neighbouring cells and fluids, a process facilitated by the adenovirus death protein (ADP). ADP consists of about 100 amino acids and harbours a single membrane-spanning domain. It undergoes post-translational processing in endoplasmic reticulum and Golgi compartments, before localizing to the inner nuclear membrane. Here, we discuss the current knowledge on how ADP induces membrane rupture. Membrane rupture is essential for both progression of disease and efficacy of therapeutic viruses in clinical applications, in particular oncolytic therapy.

NAD-linked mechanisms of gene de-repression and a novel role for CtBP in persistent adenovirus infection of lymphocytes

BACKGROUND

Adenovirus (AdV) infection is ubiquitous in the human population and causes acute infection in the respiratory and gastrointestinal tracts. In addition to lytic infections in epithelial cells, AdV can persist in a latent form in mucosal lymphocytes, and nearly 80% of children contain viral DNA in the lymphocytes of their tonsils and adenoids. Reactivation of latent AdV is thought to be the source of deadly viremia in pediatric transplant patients. Adenovirus latency and reactivation in lymphocytes is not well studied, though immune cell activation has been reported to promote productive infection from latency. Lymphocyte activation induces global changes in cellular gene expression along with robust changes in metabolic state. The ratio of free cytosolic NAD+/NADH can impact gene expression via modulation of transcriptional repressor complexes. The NAD-dependent transcriptional co-repressor C-terminal Binding Protein (CtBP) was discovered 25 years ago due to its high affinity binding to AdV E1A proteins, however, the role of this interaction in the viral life cycle remains unclear.

METHODS

The dynamics of persistently- and lytically-infected cells are evaluated. RT-qPCR is used to evaluate AdV gene expression following lymphocyte activation, treatment with nicotinamide, or disruption of CtBP-E1A binding.

RESULTS

PMA and ionomycin stimulation shifts the NAD+/NADH ratio in lymphocytic cell lines and upregulates viral gene expression. Direct modulation of NAD+/NADH by nicotinamide treatment also upregulates early and late viral transcripts in persistently-infected cells. We found differential expression of the NAD-dependent CtBP protein homologs between lymphocytes and epithelial cells, and inhibition of CtBP complexes upregulates AdV E1A expression in T lymphocyte cell lines but not in lytically-infected epithelial cells.

CONCLUSIONS

Our data provide novel insight into factors that can regulate AdV infections in activated human lymphocytes and reveal that modulation of cellular NAD+/NADH can de-repress adenovirus gene expression in persistently-infected lymphocytes. In contrast, disrupting the NAD-dependent CtBP repressor complex interaction with PxDLS-containing binding partners paradoxically alters AdV gene expression. Our findings also indicate that CtBP activities on viral gene expression may be distinct from those occurring upon metabolic alterations in cellular NAD+/NADH ratios or those occurring after lymphocyte activation.

Epigenetics and the dynamics of chromatin during adenovirus infections

The DNA genome of eukaryotic cells is compacted by histone proteins within the nucleus to form chromatin. Nuclear-replicating viruses such as adenovirus have evolved mechanisms of chromatin manipulation to promote infection and subvert host defenses. Epigenetic factors may also regulate persistent adenovirus infection and reactivation in lymphoid tissues. In this review, we discuss the viral proteins E1A and protein VII that interact with and alter host chromatin, as well as E4orf3, which separates host chromatin from sites of viral replication. We also highlight recent advances in chromatin technologies that offer new insights into virus-directed chromatin manipulation. Beyond the role of chromatin in the viral replication cycle, we discuss the nature of persistent viral genomes in lymphoid tissue and cell lines, and the potential contribution of epigenetic signals in maintaining adenovirus in a quiescent state. By understanding the mechanisms through which adenovirus manipulates host chromatin, we will understand new aspects of this ubiquitous virus and shed light on previously unknown aspects of chromatin biology.

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.

Adenoviromics: Mining the Human Adenovirus Species D Genome

Human adenovirus (HAdV) infections cause disease world-wide. Whole genome sequencing has now distinguished 90 distinct genotypes in 7 species (A-G). Over half of these 90 HAdVs fall within species D, with essentially all of the HAdV-D whole genome sequences generated in the last decade. Herein, we describe recent new findings made possible by mining of this expanded genome database, and propose future directions to elucidate new functional elements and new functions for previously known viral components.

In Situ Detection of Adenovirus DNA and mRNA in Individual Cells

Infection by DNA viruses such as human adenoviruses (HAdVs) causes a high-level accumulation of viral DNA and mRNA in the cell population. However, the average viral DNA and mRNA content in a heterogeneous cell population does not inevitably reflect the abundance in individual cells. As the vast majority of virus infection studies is carried out using standard experimental procedures with heterogeneous cell populations, there is a need for a method allowing simultaneous detection and quantitative analysis of viral genome accumulation and gene expression in individual infected cells within a population. This article describes a padlock probe-based rolling-circle amplification protocol that allows simultaneous detection of HAdV type 5 (HAdV-5) DNA and various virus-encoded mRNAs, as well as quantitative analysis of HAdV-5 DNA copies and mRNA species, in individual cells within a heterogeneous population. This versatile method can be used to detect the extent of pathogenic DNA virus infection in different cell types over prolonged infection times. Furthermore, simultaneous viral DNA and mRNA quantification in individual cells allows identification of cells in which persistent infections may be established. © 2018 by John Wiley & Sons, Inc.

Simultaneous Single-Cell In Situ Analysis of Human Adenovirus Type 5 DNA and mRNA Expression Patterns in Lytic and Persistent Infection

An efficient adenovirus infection results in high-level accumulation of viral DNA and mRNAs in the infected cell population. However, the average viral DNA and mRNA content in a heterogeneous cell population does not necessarily reflect the same abundance in individual cells. Here, we describe a novel padlock probe-based rolling-circle amplification technique that enables simultaneous detection and analysis of human adenovirus type 5 (HAdV-5) genomic DNA and virus-encoded mRNAs in individual infected cells. We demonstrate that the method is applicable for detection and quantification of HAdV-5 DNA and mRNAs in short-term infections in human epithelial cells and in long-term infections in human B lymphocytes. Single-cell evaluation of these infections revealed high heterogeneity and unique cell subpopulations defined by differential viral DNA content and mRNA expression. Further, our single-cell analysis shows that the specific expression pattern of viral E1A 13S and 12S mRNA splice variants is linked to HAdV-5 DNA content in the individual cells. Furthermore, we show that expression of a mature form of the HAdV-5 histone-like protein VII affects virus genome detection in HAdV-5-infected cells. Collectively, padlock probes combined with rolling-circle amplification should be a welcome addition to the method repertoire for the characterization of the molecular details of the HAdV life cycle in individual infected cells.IMPORTANCE Human adenoviruses (HAdVs) have been extensively used as model systems to study various aspects of eukaryotic gene expression and genome organization. The vast majority of the HAdV studies are based on standard experimental procedures carried out using heterogeneous cell populations, where data averaging often masks biological differences. As every cell is unique, characteristics and efficiency of an HAdV infection can vary from cell to cell. Therefore, the analysis of HAdV gene expression and genome organization would benefit from a method that permits analysis of individual infected cells in the heterogeneous cell population. Here, we show that the padlock probe-based rolling-circle amplification method can be used to study concurrent viral DNA accumulation and mRNA expression patterns in individual HAdV-5-infected cells. Hence, this versatile method can be applied to detect the extent of infection and virus gene expression changes in different HAdV-5 infections.

Contributions of CD8 T cells to the pathogenesis of mouse adenovirus type 1 respiratory infection

CD8 T cells are key components of the immune response to viruses, but their roles in the pathogenesis of adenovirus respiratory infection have not been characterized. We used mouse adenovirus type 1 (MAV-1) to define CD8 T cell contributions to the pathogenesis of adenovirus respiratory infection. CD8 T cell deficiency in β2m^-/- mice had no effect on peak viral replication in lungs, but clearance of virus was delayed in β2m^-/- mice. Virus-induced weight loss and increases in bronchoalveolar lavage fluid total protein, IFN-γ, TNF-α, IL-10, CCL2, and CCL5 concentrations were less in β2m^-/- mice than in controls. CD8 T cell depletion had similar effects on virus clearance, weight loss, and inflammation. Deficiency of IFN-γ or perforin had no effect on viral replication or inflammation, but perforin-deficient mice were partially protected from weight loss. CD8 T cells promote MAV-1-induced pulmonary inflammation via a mechanism that is independent of direct antiviral effects.

Humanized Mice Reproduce Acute and Persistent Human Adenovirus Infection

Severe human adenovirus (HAdV) infections are an increasing threat for immunosuppressed individuals, particularly those who have received stem cell transplants. It has been previously hypothesized that severe infections might be due to reactivation of a persistent infection, but this hypothesis has been difficult to test owing to the lack of a permissive in vivo model of HAdV infection. Here we established a humanized mouse model that reproduces features of acute and persistent HAdV infection. In this model, acute infection correlated with high mortality, weight loss, liver pathology, and expression of viral proteins in several organs. In contrast, persistent infection was asymptomatic and led to establishment of HAdV-specific adaptive immunity and expression of early viral genes exclusively in the bone marrow. These findings validate the use of humanized mice to study acute and persistent HAdV infection and strongly suggest the presence of cellular reservoirs in the bone marrow.

Distribution and Molecular Characterization of Human Adenovirus and Epstein-Barr Virus Infections in Tonsillar Lymphocytes Isolated from Patients Diagnosed with Tonsillar Diseases

Surgically removed palatine tonsils provide a conveniently accessible source of T and B lymphocytes to study the interplay between foreign pathogens and the host immune system. In this study we have characterised the distribution of human adenovirus (HAdV), Epstein-Barr virus (EBV) and human cytomegalovirus (HCMV) in purified tonsillar T and B cell-enriched fractions isolated from three patient age groups diagnosed with tonsillar hypertrophy and chronic/recurrent tonsillitis. HAdV DNA was detected in 93 out of 111 patients (84%), while EBV DNA was detected in 58 patients (52%). The most abundant adenovirus type was HAdV-5 (68%). None of the patients were positive for HCMV. Furthermore, 43 patients (39%) showed a co-infection of HAdV and EBV. The majority of young patients diagnosed with tonsillar hypertrophy were positive for HAdV, whereas all adult patients diagnosed with chronic/recurrent tonsillitis were positive for either HAdV or EBV. Most of the tonsils from patients diagnosed with either tonsillar hypertrophy or chronic/recurrent tonsillitis showed a higher HAdV DNA copy number in T compared to B cell-enriched fraction. Interestingly, in the majority of the tonsils from patients with chronic/recurrent tonsillitis HAdV DNA was detected in T cells only, whereas hypertrophic tonsils demonstrated HAdV DNA in both T and B cell-enriched fractions. In contrast, the majority of EBV positive tonsils revealed a preference for EBV DNA accumulation in the B cell-enriched fraction compared to T cell fraction irrespective of the patients' age.

Limited but durable changes to cellular gene expression in a model of latent adenovirus infection are reflected in childhood leukemic cell lines

Mucosal lymphocytes support latent infections of species C adenoviruses. Because infected lymphocytes resist re-infection with adenovirus, we sought to identify changes in cellular gene expression that could inhibit the infectious process. The expression of over 30,000 genes was evaluated by microarray in persistently infected B-and T-lymphocytic cells. BBS9, BNIP3, BTG3, CXADR, SLFN11 and SPARCL1 were the only genes differentially expressed between mock and infected B cells. Most of these genes are associated with oncogenesis or cancer progression. Histone deacetylase and DNA methyltransferase inhibitors released the repression of some of these genes. Cellular and viral gene expression was compared among leukemic cell lines following adenovirus infection. Childhood leukemic B-cell lines resist adenovirus infection and also show reduced expression of CXADR and SPARCL. Thus adenovirus induces limited changes to infected B-cell lines that are similar to changes observed in childhood leukemic cell lines.

E2F/Rb Family Proteins Mediate Interferon Induced Repression of Adenovirus Immediate Early Transcription to Promote Persistent Viral Infection

Interferons (IFNs) are cytokines that have pleiotropic effects and play important roles in innate and adaptive immunity. IFNs have broad antiviral properties and function by different mechanisms. IFNs fail to inhibit wild-type Adenovirus (Ad) replication in established cancer cell lines. In this study, we analyzed the effects of IFNs on Ad replication in normal human cells. Our data demonstrate that both IFNα and IFNγ blocked wild-type Ad5 replication in primary human bronchial epithelial cells (NHBEC) and TERT-immortalized normal human diploid fibroblasts (HDF-TERT). IFNs inhibited the replication of divergent adenoviruses. The inhibition of Ad5 replication by IFNα and IFNγ is the consequence of repression of transcription of the E1A immediate early gene product. Both IFNα and IFNγ impede the association of the transactivator GABP with the E1A enhancer region during the early phase of infection. The repression of E1A expression by IFNs requires a conserved E2F binding site in the E1A enhancer, and IFNs increased the enrichment of the E2F-associated pocket proteins, Rb and p107, at the E1A enhancer in vivo. PD0332991 (Pabociclib), a specific CDK4/6 inhibitor, dephosphoryles pocket proteins to promote their interaction with E2Fs and inhibited wild-type Ad5 replication dependent on the conserved E2F binding site. Consistent with this result, expression of the small E1A oncoprotein, which abrogates E2F/pocket protein interactions, rescued Ad replication in the presence of IFNα or IFNγ. Finally, we established a persistent Ad infection model in vitro and demonstrated that IFNγ suppresses productive Ad replication in a manner dependent on the E2F binding site in the E1A enhancer. This is the first study that probes the molecular basis of persistent adenovirus infection and reveals a novel mechanism by which adenoviruses utilize IFN signaling to suppress lytic virus replication and to promote persistent infection.

Interferons play important roles in both innate and adaptive immunity, and have broad antiviral properties. We demonstrate that type I (IFNα) and type II (IFNγ) IFNs inhibit the replication of divergent adenoviruses via an evolutionally conserved E2F binding site. IFNs augment the association of the tumor suppressors Rb and p107 with the E1A enhancer region in vivo to repress viral immediate early transcription. By comparing the properties of wild type and E2F site mutant viruses, we show that the IFN–E2F/Rb axis is critical for restriction of adenovirus replication to promote persistent viral infection. Relief of E2F/Rb repression counteracts IFN signaling whereas enforcement of E2F/Rb interaction mimics IFN signaling. These results reveal a novel mechanism by which adenoviruses utilize IFN signaling to suppress lytic virus replication and promote persistent infection.

HAdV-2-suppressed growth of SV40 T antigen-transformed mouse mammary epithelial cell-induced tumours in SCID mice

Human adenovirus (HAdV) vectors are promising tools for cancer therapy, but the shortage of efficient animal models for productive HAdV infections has restricted the evaluation of systemic effects to mainly immunodeficient mice. Previously, we reported a highly efficient replication of HAdV-2 in a non-tumorigenic mouse mammary epithelial cell line, NMuMG. Here we show that HAdV-2 gene expression and progeny formation in NMuMG cells transformed with the SV40 T antigen (NMuMG-T cells) were as efficient as in the parental NMuMG cells. Injection of HAdV-2 into tumours established by NMuMG-T in SCID mice caused reduced tumour growth and signs of intratumoural lesions. HAdV-2 replicated within the NMuMG-T-established tumours, but not in interspersed host-derived tissues within the tumours. The specific infection of NMuMG-T-derived tumours was verified by the lack of viral DNA in kidney, lung or spleen although low levels of viral DNA was occasionally found in liver.

Efficient Isolation Protocol for B and T Lymphocytes from Human Palatine Tonsils

Tonsils form a part of the immune system providing the first line of defense against inhaled pathogens. Usually the term "tonsils" refers to the palatine tonsils situated at the lateral walls of the oral part of the pharynx. Surgically removed palatine tonsils provide a convenient accessible source of B and T lymphocytes to study the interplay between foreign pathogens and the host immune system. This video protocol describes the dissection and processing of surgically removed human palatine tonsils, followed by the isolation of the individual B and T cell populations from the same tissue sample. We present a method, which efficiently separates tonsillar B and T lymphocytes using an antibody-dependent affinity protocol. Further, we use the method to demonstrate that human adenovirus infects specifically the tonsillar T cell fraction. The established protocol is generally applicable to efficiently and rapidly isolate tonsillar B and T cell populations to study the role of different types of pathogens in tonsillar immune responses.

Neonatal infection with species C adenoviruses confirmed in viable cord blood lymphocytes

Credible but conflicting reports address the frequency of prenatal infection by species C adenovirus. This question is important because these viruses persist in lymphoid cells and suppress double-stranded DNA-break repair. Consequently, prenatal adenovirus infections may generate the aberrant clones of lymphocytes that precede development of childhood acute lymphoblastic leukemia (ALL). The present study was designed to overcome technical limitations of prior work by processing cord blood lymphocytes within a day of collection, and by analyzing sufficient numbers of lymphocytes to detect adenovirus-containing cells at the lower limits determined by our previous studies of tonsil lymphocytes. By this approach, adenoviral DNA was identified in 19 of 517 (3.7%) samples, providing definitive evidence for the occurrence of prenatal infection with species C adenoviruses in a significant fraction of neonates predominantly of African American and Hispanic ancestry. Cord blood samples were also tested for the presence of the ETV6-RUNX1 translocation, the most common genetic abnormality in childhood ALL. Using a nested PCR assay, the ETV6-RUNX1 transcript was detected in four of 196 adenovirus-negative samples and one of 14 adenovirus-positive cord blood samples. These findings indicate that this method will be suitable for determining concordance between adenovirus infection and the leukemia-associated translocations in newborns.

Detection of common respiratory viruses in tonsillar tissue of children with obstructive sleep apnea

BACKGROUND

Early life viral infection is associated with neurogenic inflammation that is present in lymphoid tissues of the upper airway in children with obstructive sleep apnea (OSA). We hypothesized that viral genomic material is present in tonsils of children with OSA. Therefore, we examined tonsils for the presence of respiratory viruses' nucleic acids in children with OSA, and in children without OSA (undergoing surgery for recurrent throat infections (RI)).

METHODS

Tonsillar tissue from patients with OSA and RI was subjected to multiplex quantitative real time reverse transcription PCR (mqRTPCR), analyzed for the presence of common respiratory viruses' genetic material.

RESULTS

Fifty-six patients were included, of whom 34 had OSA (age (years ± S.D), 4.22 ± 1.14) and 22 with RI (4.35 ± 1.36). Respiratory viruses nucleic acids (24 detections) were observed in 17 (50%) OSA samples. In contrast, no virus was detected in RI samples (relative frequency P<0.0001). Viruses detected, based on frequency were Rhinovirus, Adenovirus, human metapneumovirus (hMPV), respiratory syncytial virus (RSV), and corona virus.

CONCLUSIONS

Respiratory viruses are detected in OSA hypertrophic tonsils, suggestive of their role in the evolution of tonsillar inflammation and hypertrophy. Early life viral infections may contribute to the pathogenesis of pediatric OSA.

Respiratory viruses are continuously detected in children with chronic tonsillitis throughout the year

OBJECTIVE

To evaluate the oscillations on the viral detection in adenotonsillar tissues from patients with chronic adenotonsillar diseases as an indicia of the presence of persistent viral infections or acute subclinical infections.

STUDY DESIGN

Cross-sectional prospective study.

SETTING

Tertiary hospital.

METHODS

The fluctuations of respiratory virus detection were compared to the major climatic variables during a two-year period using adenoids and palatine tonsils from 172 children with adenotonsillar hypertrophy and clinical evidence of obstructive sleep apnoea syndrome or recurrent adenotonsillitis, without symptoms of acute respiratory infection (ARI), by TaqMan real-time PCR.

RESULTS

The rate of detection of at least one respiratory virus in adenotonsillar tissue was 87%. The most frequently detected viruses were human adenovirus in 52.8%, human enterovirus in 47.2%, human rhinovirus in 33.8%, human bocavirus in 31.1%, human metapneumovirus in 18.3% and human respiratory syncytial virus in 17.2%. Although increased detection of human enterovirus occurred in summer/autumn months, and there were summer nadirs of human respiratory syncytial virus in both years of the study, there was no obvious viral seasonality in contrast to reports with ARI patients in many regions of the world.

CONCLUSION

Respiratory viruses are continuously highly detected during whole year, and without any clinical symptomatology, indicating that viral genome of some virus can persist in lymphoepithelial tissues of the upper respiratory tract.

Adenovirus death protein (ADP) is required for lytic infection of human lymphocytes

The adenovirus death protein (ADP) is expressed at late times during a lytic infection of species C adenoviruses. ADP promotes the release of progeny virus by accelerating the lysis and death of the host cell. Since some human lymphocytes survive while maintaining a persistent infection with species C adenovirus, we compared ADP expression in these cells with ADP expression in lymphocytes that proceed with a lytic infection. Levels of ADP were low in KE37 and BJAB cells, which support a persistent infection. In contrast, levels of ADP mRNA and protein were higher in Jurkat cells, which proceed with a lytic infection. Epithelial cells infected with an ADP-overexpressing virus died more quickly than epithelial cells infected with an ADP-deleted virus. However, KE37, and BJAB cells remained viable after infection with the ADP-overexpressing virus. Although the levels of ADP mRNA increased in KE37 and BJAB cells infected with the ADP-overexpressing virus, the fraction of cells with detectable ADP was unchanged, suggesting that the control of ADP expression differs between epithelial and lymphocytic cells. When infected with an ADP-deleted adenovirus, Jurkat cells survived and maintained viral DNA for greater than 1 month. These findings are consistent with the notion that the level of ADP expression determines whether lymphocytic cells proceed with a lytic or a persistent adenovirus infection.

Persistently adenovirus-infected lymphoid cells express microRNAs derived from the viral VAI and especially VAII RNA

Human adenovirus can establish latent infections in lymphoid tissues in vivo and persistent, infections in cultured lymphoid cell lines. During lytic infection, adenovirus expresses microRNAs (miRNAs) derived from the viral non-coding RNAs VAI and, especially, VAII. Here, we demonstrate that persistently adenovirus-infected human BJAB cells also produce adenovirus-derived miRNAs primarily derived from the viral VAII RNA, which contributes ~2.7% of all RNA-induced silencing complex (RISC)-associated RNAs. However, our data indicate that the 5' end of the predominant VAII-derived viral RNA, and hence its seed sequence, differs from what has been previously reported. Our data demonstrate that adenovirus expresses viral miRNAs in chronically infected lymphoid cells and raise the possibility that these may contribute to the maintenance of the latently adenovirus-infected lymphoid cells previously observed in mucosal-associated lymphoid tissues in vivo.

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

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

Prevalence and quantitation of adenovirus DNA from human tonsil and adenoid tissues

In this study, real-time PCR was used to quantify adenovirus DNA in cell suspensions prepared from 106 right and left tonsils and 10 adenoids obtained from 57 patients who underwent routine tonsillectomies and/or adenoidectomies. Eighty-four (72.4%) tonsils and adenoids samples were positive for HAdV by real-time PCR. The viral load ranged from 2.8 × 10(2) to 2.6 × 10(6) copies/10(7) cells and varied up to sixfold between the right and left tonsils. In some cases, only one tonsil was positive and the viral load was lower in older children. Seventy-eight of 84 positive samples could be typed by sequencing of the hexon L1 region. Species C (types 1, 2, and 5) were detected in 84.1% of the patients followed by types 3 and 7 of species B (6.8%), HAdV-E4 (6.8%), and HAdV-F41 (2.3%). In one patient adenovirus C2 was found in the left tonsil and adenovirus C5 in the right tonsil. No DNA methylation was detected in either the E1A promoter or the major late promoter region of adenovirus DNA from six tonsils and adenoids samples and two clinical isolates.

Old and new functions for the adenovirus virus-associated RNAs

Adenovirus type 5 encodes two short, highly structured noncoding RNAs, the virus-associated (VA) RNAI and VA RNAII. These RNAs are expressed in large amounts late during a lytic infection. Early studies established an important role for VA RNAI in maintaining efficient translation in late virus-infected cells by blocking activation of the key interferon-induced PKR protein kinase. More recent studies have demonstrated that the VA RNAs also target the RNAi/miRNA pathway. Collectively, available data suggest that the VA RNAs are multifunctional RNAs suppressing the activity of three dsRNA-sensing enzyme systems in human cells. Here, the known functions of the VA RNAs are summarized and the interplay between VA RNA expression and the activity of the interferon and RNAi pathways are discussed in more detail.

No evidence of a death-like function for species B1 human adenovirus type 3 E3-9K during A549 cell line infection

Background

Subspecies B1 human adenoviruses (HAdV-B1) are prevalent respiratory pathogens. Compared to their species C (HAdV-C) counterparts, relatively little work has been devoted to the characterization of their unique molecular biology. The early region 3 (E3) transcription unit is an interesting target for future efforts because of its species-specific diversity in genetic content among adenoviruses. This diversity is particularly significant for the subset of E3-encoded products that are membrane glycoproteins and may account for the distinct pathobiology of the different human adenovirus species. In order to understand the role of HAdV-B-specific genes in viral pathogenesis, we initiated the characterization of unique E3 genes. As a continuation of our efforts to define the function encoded in the highly polymorphic ORF E3-10.9K and testing the hypothesis that the E3-10.9K protein orthologs with a hydrophobic domain contribute to the efficient release of viral progeny, we generated HAdV-3 mutant viruses unable to express E3-10.9K ortholog E3-9K and examined their ability to grow, disseminate, and egress in cell culture.

Results

No differences were observed in the kinetics of infected cell death, and virus progeny release or in the plaque size and dissemination phenotypes between cells infected with HAdV-3 E3-9K mutants or the parental virus. The ectopic expression of E3-10.9K orthologs with a hydrophobic domain did not compromise cell viability.

Conclusions

Our data show that despite the remarkable similarities with HAdV-C E3-11.6K, HAdV-B1 ORF E3-10.9K does not encode a product with a “death-like” biological activity.

High rates of detection of respiratory viruses in tonsillar tissues from children with chronic adenotonsillar disease

Chronic tonsillar diseases are an important health problem, leading to large numbers of surgical procedures worldwide. Little is known about pathogenesis of these diseases. In order to investigate the role of respiratory viruses in chronic adenotonsillar diseases, we developed a cross-sectional study to determine the rates of viral detections of common respiratory viruses detected by TaqMan real time PCR (qPCR) in nasopharyngeal secretions, tonsillar tissues and peripheral blood from 121 children with chronic tonsillar diseases, without symptoms of acute respiratory infections. At least one respiratory virus was detected in 97.5% of patients. The viral co-infection rate was 69.5%. The most frequently detected viruses were human adenovirus in 47.1%, human enterovirus in 40.5%, human rhinovirus in 38%, human bocavirus in 29.8%, human metapneumovirus in 17.4% and human respiratory syncytial virus in 15.7%. Results of qPCR varied widely between sample sites: human adenovirus, human bocavirus and human enterovirus were predominantly detected in tissues, while human rhinovirus was more frequently detected in secretions. Rates of virus detection were remarkably high in tonsil tissues: over 85% in adenoids and close to 70% in palatine tonsils. In addition, overall virus detection rates were higher in more hypertrophic than in smaller adenoids (p = 0.05), and in the particular case of human enteroviruses, they were detected more frequently (p = 0.05) in larger palatine tonsils than in smaller ones. While persistence/latency of DNA viruses in tonsillar tissues has been documented, such is not the case of RNA viruses. Respiratory viruses are highly prevalent in adenoids and palatine tonsils of patients with chronic tonsillar diseases, and persistence of these viruses in tonsils may stimulate chronic inflammation and play a role in the pathogenesis of these diseases.

Replicating adenovirus-simian immunodeficiency virus (SIV) vectors efficiently prime SIV-specific systemic and mucosal immune responses by targeting myeloid dendritic cells and persisting in rectal macrophages, regardless of immunization route

Although priming with replicating adenovirus type 5 host range mutant (Ad5hr)-human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) recombinants, followed by HIV/SIV envelope boosting, has proven highly immunogenic, resulting in protection from SIV/simian-human immunodeficiency virus (SHIV) challenges, Ad5hr recombinant distribution, replication, and persistence have not been examined comprehensively in nonhuman primates. We utilized Ad5hr-green fluorescent protein and Ad5hr-SIV recombinants to track biodistribution and immunogenicity following mucosal priming of rhesus macaques by the intranasal/intratracheal, sublingual, vaginal, or rectal route. Ad recombinants administered by all routes initially targeted macrophages in bronchoalveolar lavage (BAL) fluid and rectal tissue, later extending to myeloid dendritic cells in BAL fluid with persistent expression in rectal mucosa 25 weeks after the last Ad immunization. Comparable SIV-specific immunity, including cellular responses, serum binding antibody, and mucosal secretory IgA, was elicited among all groups. The ability of the vector to replicate in multiple mucosal sites irrespective of delivery route, together with the targeting of macrophages and professional antigen-presenting cells, which provide potent immunogenicity at localized sites of virus entry, warrants continued use of replicating Ad vectors.

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

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

Adenoviruses in lymphocytes of the human gastro-intestinal tract

Objective

Persistent adenoviral shedding in stools is known to occur past convalescence following acute adenoviral infections. We wished to establish the frequency with which adenoviruses may colonize the gut in normal human subjects.

Methods

The presence of adenoviral DNA in intestinal specimens obtained at surgery or autopsy was tested using a nested PCR method. The amplified adenoviral DNA sequences were compared to each other and to known adenoviral species. Lamina propria lymphocytes (LPLs) were isolated from the specimens and the adenoviral copy numbers in the CD4+ and CD8+ fractions were determined by quantitative PCR. Adenoviral gene expression was tested by amplification of adenoviral mRNA.

Results

Intestinal tissue from 21 of 58 donors and LPLs from 21 of 24 donors were positive for the presence of adenoviral DNA. The majority of the sequences could be assigned to adenoviral species E, although species B and C sequences were also common. Multiple sequences were often present in the same sample. Forty-one non-identical sequences were identified from 39 different tissue donors. Quantitative PCR for adenoviral DNA in CD4+ and CD8+ fractions of LPLs showed adenoviral DNA to be present in both cell types and ranged from a few hundred to several million copies per million cells on average. Active adenoviral gene expression as evidenced by the presence of adenoviral messenger RNA in intestinal lymphocytes was demonstrated in 9 of the 11 donors tested.

Conclusion

Adenoviral DNA is highly prevalent in lymphocytes from the gastro-intestinal tract indicating that adenoviruses may be part of the normal gut flora.

Enhanced transduction and replication of RGD-fiber modified adenovirus in primary T cells

Background

Adenoviruses are often used as vehicles to mediate gene delivery for therapeutic purposes, but their research scope in hematological cells remains limited due to a narrow choice of host cells that express the adenoviral receptor (CAR). T cells, which are attractive targets for gene therapy of numerous diseases, remain resistant to adenoviral infection because of the absence of CAR expression. Here, we demonstrate that this resistance can be overcome when murine or human T cells are transduced with an adenovirus incorporating the RGD-fiber modification (Ad-RGD).

Methodology/Principal Finding

A luciferase-expressing replication-deficient Ad-RGD infected 3-fold higher number of activated primary T cells than an adenovirus lacking the RGD-fiber modification in vitro. Infection with replication-competent Ad-RGD virus also caused increased cell cycling, higher E1A copy number and enriched hexon antigen expression in both human and murine T cells. Transduction with oncolytic Ad-RGD also resulted in higher titers of progeny virus and enhanced the killing of T cells. In vivo, 35–45% of splenic T cells were transduced by Ad-RGD.

Conclusions

Collectively, our results prove that a fiber modified Ad-RGD successfully transduces and replicates in primary T cells of both murine and human origin.