Adenoidal-pharyngeal-conjunctival agents: a newly recognized group of common viruses of the respiratory system

Longitudinal Analysis of Binding Antibody Levels Against 39 Human Adenovirus Types in Sera from 60 Regular Blood Donors from Greifswald, Germany, over 5 Years from 2018 to 2022

Adenoviruses are important human pathogens that are widespread and mainly associated with respiratory and gastrointestinal infections. In a previous study on human adenovirus (HAdV) seroprevalence, we observed reduced binding antibody levels against a range of HAdV types in sera collected from students in 2021 compared to sera collected before the SARS-CoV-2 pandemic. In this follow-up study, we wanted to verify this observation in a cohort of regular blood donors for whom serial samples were available. Therefore, HAdV-specific binding antibody levels were analyzed in sera collected over a 5-year period from 2018 to 2022 in a cohort of 60 regular donors to the blood bank of the University Hospital in Greifswald, Germany. Using ELISA-based assays, we quantified the binding antibody responses against 39 HAdV types. On the cohort level, we found largely stable antibody levels over the analyzed time period, with the highest antibody responses against HAdV-C1, -D25, -D26, -E4, -D10, -D27, -C5, -D75, -C2, and -C6. Only minor but significant reductions in comparison to the first serum samples from 2018 were detected for antibody levels in 2021 and 2022 against the low-prevalent types HAdV-A31, -D8, -D20, -D37, -D65, and -D69. On the other hand, we detected fluctuations in antibody levels on the individual level, with strong increases in antibody levels indicative of novel antigen contact. Interestingly, we frequently found simultaneous changes in antibody responses against multiple HAdV types, resulting in strong correlations of antibody responses against distinct clusters of HAdVs suggesting extensive cross-reactivity of HAdV-specific antibodies. To our knowledge, this is the first study of antibodies against a broad range of HAdV types in serum samples collected from a cohort of individuals over a prolonged period, and our data provide important insight into the long-term stability of HAdV-specific antibody levels. In this cohort of regular blood donors, we did not observe any major impact of the SARS-CoV-2 pandemic on HAdV immunity. Correlations of changes in antibody levels against different types indicate cross-reactivity of HAdV-specific antibodies that are important to consider for HAdV vector development. Our data also reveal possible candidates for future development of HAdV-based vectors.

Advances of Recombinant Adenoviral Vectors in Preclinical and Clinical Applications

Adenoviruses (Ad) have the potential to induce severe infections in vulnerable patient groups. Therefore, understanding Ad biology and antiviral processes is important to comprehend the signaling cascades during an infection and to initiate appropriate diagnostic and therapeutic interventions. In addition, Ad vector-based vaccines have revealed significant potential in generating robust immune protection and recombinant Ad vectors facilitate efficient gene transfer to treat genetic diseases and are used as oncolytic viruses to treat cancer. Continuous improvements in gene delivery capacity, coupled with advancements in production methods, have enabled widespread application in cancer therapy, vaccine development, and gene therapy on a large scale. This review provides a comprehensive overview of the virus biology, and several aspects of recombinant Ad vectors, as well as the development of Ad vector, are discussed. Moreover, we focus on those Ads that were used in preclinical and clinical applications including regenerative medicine, vaccine development, genome engineering, treatment of genetic diseases, and virotherapy in tumor treatment.

Seroprevalence of Binding and Neutralizing Antibodies against 39 Human Adenovirus Types in Patients with Neuromuscular Disorders

High pre-existing antibodies against viral vectors reduce their functionality and may lead to adverse complications. To circumvent this problem in future gene therapy approaches, we tested the seroprevalence of a large range of human adenovirus types in patients with neuromuscular disorders (NMDs) to find appropriate viral vector candidates for gene replacement therapy for NMDs. Binding and neutralizing antibodies against 39 human adenovirus types were tested in the sera of 133 patients with NMDs and 76 healthy controls aged 17-92 years. The influence of age, sex, and NMDs on antibody levels was analyzed. The seroprevalence of different adenoviruses in the cohort varied widely. The highest levels of binding antibodies were detected against HAdV-D27, -C1, -D24, -D70, -B14, -C6, -D13, -B34, and -E4, whereas the lowest reactivity was detected against HAdV-F41, -A31, -B11, -D75, -D8, -D65, -D26, -D80, and -D17. The highest neutralizing reactivity was observed against HAdV-B3, -C2, -E4, -C1, -G52, -C5, and -F41, whereas the lowest neutralizing reactivity was observed against HAdV-D74, -B34, -D73, -B37, -D48, -D13, -D75, -D8, -B35, and -B16. We detected no influence of sex and only minor differences between different age groups. Importantly, there were no significant differences between healthy controls and patients with NMDs. Our data show that patients with NMDs have very similar levels of binding and neutralizing antibodies against HAdV compared to healthy individuals, and we identified HAdV-A31, -B16, -B34, -B35, -D8, -D37, -D48, -D73, -D74, -D75, and -D80 as promising candidates for future vector development due to their low binding and neutralizing antibody prevalence.

Analysis of the Prevalence of Binding and Neutralizing Antibodies against 39 Human Adenovirus Types in Student Cohorts Reveals Low-Prevalence Types and a Decline in Binding Antibody Levels during the SARS-CoV-2 Pandemic

Vectors based on human adenoviruses (HAdVs) are important for the development of novel immunizations, oncolytic therapies, and gene therapies. The use of HAdV-based vaccines against Ebola virus, the rapid adaptation of the vector technology for vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and their very good efficacy have shown the great potential of HAdV-based vaccines.

The use of adenoviral vectors in gene therapy and vaccine approaches

Adenovirus was first identified in the 1950s and since then this pathogenic group of viruses has been explored and transformed into a genetic transfer vehicle. Modification or deletion of few genes are necessary to transform it into a conditionally or non-replicative vector, creating a versatile tool capable of transducing different tissues and inducing high levels of transgene expression. In the early years of vector development, the application in monogenic diseases faced several hurdles, including short-term gene expression and even a fatality. On the other hand, an adenoviral delivery strategy for treatment of cancer was the first approved gene therapy product. There is an increasing interest in expressing transgenes with therapeutic potential targeting the cancer hallmarks, inhibiting metastasis, inducing cancer cell death or modulating the immune system to attack the tumor cells. Replicative adenovirus as vaccines may be even older and date to a few years of its discovery, application of non-replicative adenovirus for vaccination against different microorganisms has been investigated, but only recently, it demonstrated its full potential being one of the leading vaccination tools for COVID-19. This is not a new vector nor a new technology, but the result of decades of careful and intense work in this field.

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.

Codon Usage and Adenovirus Fitness: Implications for Vaccine Development

Vaccination is the most effective method to date to prevent viral diseases. It intends to mimic a naturally occurring infection while avoiding the disease, exposing our bodies to viral antigens to trigger an immune response that will protect us from future infections. Among different strategies for vaccine development, recombinant vaccines are one of the most efficient ones. Recombinant vaccines use safe viral vectors as vehicles and incorporate a transgenic antigen of the pathogen against which we intend to generate an immune response. These vaccines can be based on replication-deficient viruses or replication-competent viruses. While the most effective strategy involves replication-competent viruses, they must be attenuated to prevent any health hazard while guaranteeing a strong humoral and cellular immune response. Several attenuation strategies for adenoviral-based vaccine development have been contemplated over time. In this paper, we will review them and discuss novel approaches based on the principle that protein synthesis from individual genes can be modulated by codon usage bias manipulation. We will summarize vaccine approaches that consider recoding of viral proteins to produce adenoviral attenuation and recoding of the transgene antigens for both viral attenuation and efficient viral epitope expression.

Prevalence of Common Respiratory Viral Infections and Identification of Adenovirus in Hospitalized Adults in Harbin, China 2014 to 2017

Background: Respiratory infections pose a great challenge in global health, and the prevalence of viral infection in adult patients has been poorly understood in northeast China. Harbin is one of the major cities in northeast China, and more than half of any given year in Harbin is occupied by winter. To reveal the viral etiology and seasonality in adult patients from Harbin, a 4-year consecutive survey was conducted in Harbin, China.

Methods: From January 2014 to December 2017, specimens were obtained from adult patients admitted to the Second Affiliated Hospital of Harbin Medical University with lower respiratory tract infections. Sputum samples were examined by direct immunofluorescence assays to detect seven common respiratory viruses, including influenza virus (type A and B), parainfluenza virus (type 1 to 3), respiratory syncytial virus and adenovirus. Adenovirus positive samples were seeded onto A549 cells to isolate viral strains. Phylogenetic analysis was conducted on the highly variable region of adenoviral hexon gene.

Results: A total of 1,300 hospitalized adult patients with lower respiratory tract infections were enrolled, in which 189 patients (14.5%) were detected as having at least one viral infection. The co-infection rate in this study was 25.9% (49/189). The dominant viral pathogen from 2014 to 2017 was parainfluenza virus, with a detection rate of 7.2%, followed by influenza virus, respiratory syncytial virus and adenovirus. Based on the climate seasons determined by daily average temperature, the highest overall viral detection rate was detected in spring (22.0%, 52/236), followed by winter (13.4%, 109/813), autumn (11.4%, 13/114) and summer (10.9%, 15/137). Adenovirus type 3 strains with slight variations were isolated from positive cases, which were closely related to the GB strain from the United States, as well as the Harbin04B strain isolated locally.

Conclusion: This study demonstrated that common respiratory viruses were partially responsible for hospitalized lower respiratory tract infections in adult patients from Harbin, China, with parainfluenza virus as the dominant viral pathogen. Climate seasons could be rational indicators for the seasonality analysis of airborne viral infections. Future surveillance on viral mutations would be necessary to reveal the evolutionary history of respiratory viruses.

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.

Worldwide increased prevalence of human adenovirus type 3 (HAdV-3) respiratory infections is well correlated with heterogeneous hypervariable regions (HVRs) of hexon

Human adenovirus type 3 (HAdV-3) respiratory infections occurs worldwide in both children and adults, leading to severe morbidity and mortality, particularly in the paediatric age group and especially in neonates. During HAdV infection, neutralizing antibodies are formed against the epitopes located in the hyper variable regions (HVRs) of the hexon protein. These neutralizing antibodies provide protection against reinfection by viruses of the same type. Therefore it is reasonable to speculate that variations of HAdV-3 in the HVRs could impair the immunity acquired by previous infection with a different strain with variation in its HVRs. HAdV-3 has recently become the major agent of acute respiratory infection worldwide, being responsible for 15% to 87% of all adenoviral respiratory infections. However, despite the increased prevalence of HAdV-3 as respiratory pathogen, the diversity of hexon proteins in circulating strains remains unexplored. This study was designed to explore the variation in HVRs of hexon among globally distributed strains of HAdV-3 as well as to discover possible relationship among them, thus possibly shedding light on the cause for the increased prevalence of HAdV-3. In this study, for the first time we analysed the hexon proteins of all 248 available strains of HAdV-3 from the NCBI database and compared them with those of the HAdV-3 prototype (GB stain). We found that the HVRs of HAdV-3 strains circulating worldwide were highly heterogeneous and have been mutating continuously since -their original isolation. Based on their immense heterogeneity, the strains can be categorized into 25 hexon variants (3Hv-1 to 3Hv-25), 4 of which (3Hv-1 to 3Hv-4) comprises 80% of the strains. This heterogeneity may explain why HAdV-3 has become the most prevalent HAdVs type worldwide. The heterogeneity of hexon proteins also shows that the development of a vaccine against HAdV-3 might be challenging. The data on hexon variants provided here may be useful for the future epidemiological study of HAdV-3 infection.

Minimum Infective Dose of the Major Human Respiratory and Enteric Viruses Transmitted Through Food and the Environment

Viruses are a significant cause of morbidity and mortality around the world. Determining the minimum dose of virus particles that can initiate infection, termed the minimum infective dose (MID), is important for the development of risk assessment models in the fields of food and water treatment and the implementation of appropriate infection control strategies in healthcare settings. Both respiratory and enteric viruses can be shed at high titers from infected individuals even when the infection is asymptomatic. Presence of pre-existing antibodies has been shown to affect the infectious dose and to be protective against reinfection for many, but not all viruses. Most respiratory viruses appear to be as infective in humans as in tissue culture. Doses of <1 TCID50 of influenza virus, rhinovirus, and adenovirus were reported to infect 50% of the tested population. Similarly, low doses of the enteric viruses, norovirus, rotavirus, echovirus, poliovirus, and hepatitis A virus, caused infection in at least some of the volunteers tested. A number of factors may influence viruses' infectivity in experimentally infected human volunteers. These include host and pathogen factors as well as the experimental methodology. As a result, the reported infective doses of human viruses have to be interpreted with caution.

STRUCTURE AND DEVELOPMENT OF VIRUSES OBSERVED IN THE ELECTRON MICROSCOPE : IV. VIRUSES OF THE RI-APC GROUP

Representative viruses of the RI-APC group were observed with the electron microscope in thin sections of infected HeLa cells. The viral particles varied in density, were approximately 60 mµ in diameter and had a center to center spacing when close packed of about 65 mµ. Many of the less dense particles exhibited an internal body averaging 24 mµ in diameter. It was suggested that within the nucleus the virus differentiated from dense granular and reticular material and formed crystals. Disintegration of the crystals and disruption of the nuclear membrane with release of virus into the cytoplasm appeared to occur at any stage. No evidence to suggest development of the virus in the cytoplasm was obtained. It was possible to deduce the structure of the viral crystal from the electron micrographs. The viral particles are packed in a cubic body—centered lattice. Correlative histochemical observations in the light microscope which are now in progress revealed that the crystals and non-crystalline aggregates of virus were strongly Feulgen-positive.

The role of viruses in the etiology and pathogenesis of common cold

Numerous viruses are able to cause respiratory tract infections. With the availability of new molecular techniques, the number of pathogens detected in specimens from the human respiratory tract has increased. Some of these viral infections have the potential to lead to severe systemic disease. Other viruses are limited to playing a role in the pathogenesis of the common cold syndrome. This chapter focuses on the viral pathogens that are linked to common cold. It is not the intention to comprehensively review all the viruses that are able to cause respiratory tract infections—this would go beyond the scope of this book. The list of viruses that are briefly reviewed here includes rhinoviruses, respiratory syncytial virus, parainfluenza virus, adenovirus, metapneumovirus and coronavirus. Bocavirus is discussed as one example of a newly identified pathogen with a less established role in the etiology and pathogenesis of common cold. Influenza virus does not cause what is defined as common cold. However, influenza viruses are associated with respiratory disease and the clinical picture of mild influenza and common cold frequently overlaps. Therefore, influenza virus has been included in this chapter. It is important to note that a number of viruses are frequently co-detected with other viruses in humans with respiratory diseases. Therefore, the viral etiology and the role of viruses in the pathogenesis of common cold is complex, and numberous questions remain to be answered.

Latent species C adenoviruses in human tonsil tissues

Although species C human adenoviruses establish persistent infections, the molecular details of this lifestyle remain poorly understood. We previously reported that adenovirus DNA is found in human mucosal T lymphocytes in a noninfectious form (C. T. Garnett, D. Erdman, W. Xu, and L. R. Gooding, J. Virol. 76:10608-10616, 2002). In this study, human tonsil and adenoid tissues were analyzed to determine the dynamics of infection, the rate of clearance of viral DNA, and the possibility of reactivation of virus from these tissues. The presence of viral DNA peaked at 4 years of age and declined thereafter. The average number of viral genomes declined with the age of the donor. The frequency of virus-bearing cells ranged from 3 x 10(-7) to 3.4 x 10(-4), while the amount of viral DNA per cell varied less, with an average of 280 copies per cell. All species C serotypes were represented in these tissues, although adenovirus type 6 was notably rare. Infectious virus was detected infrequently (13 of 94 of donors tested), even among donors with the highest levels of adenoviral DNA. Adenovirus transcripts were rarely detected in uncultured lymphocytes (2 of 12 donors) but appeared following stimulation and culture (11 of 13 donors). Viral DNA replication could be stimulated in most donor samples by lymphocyte stimulation in culture. New infectious virus was detected in 13 of 15 donors following in vitro stimulation. These data suggest that species C adenoviruses can establish latent infections in mucosal lymphocytes and that stimulation of these cells can cause viral reactivation resulting in RNA transcription, DNA replication, and infectious virus production.

Avian adenoviruses--a review

The literature on avian adenoviruses is reviewed with particular reference to the virion, number of serotypes, epidemiology, diagnosis and association with disease. Using the serum neutralisation test there are probably at least 12 serotypes which share a common avian group antigen distinct from the mammalian group antigen. The three disease complexes most often associated with avian adenovirus infections are respiratory disease, falls in egg production and hepatitis.

Outbreak of human adenovirus type 3 infection in a pediatric long-term care facility--Illinois, 2005

BACKGROUND

Human adenovirus type 3 (HAdV-3) causes severe respiratory illness in children, but outbreaks in long-term care facilities have not been frequently reported. We describe an outbreak of HAdV-3 infection in a long-term care facility for children with severe neurologic impairment, where only 3 of 63 residents were ambulatory.

METHODS

A clinical case of HAdV-3 was defined as fever (temperature, > or = 38.0 degrees C) and either a worsening of respiratory symptoms or conjunctivitis in a resident, with illness onset from June through August 2005. We reviewed medical records; conducted surveillance for fever, conjunctivitis, and respiratory symptoms; and collected nasopharyngeal and conjunctival specimens from symptomatic residents. Specimens were cultured in HAdV-permissive cell lines or were analyzed by HAdV-specific polymerase chain reaction assay.

RESULTS

Thirty-five (56%) of 63 residents had illnesses that met the case definition; 17 patients (49%) were admitted to intensive care units, and 2 (6%) died. Patients were hospitalized in the intensive care unit for a total of 233 patient-days. Illness onset dates ranged from 1 June through 24 August 2005. Thirty-two patients (91%) had respiratory infection, and 3 (9%) had conjunctivitis. HAdV was identified by culture or PCR in 20 patients. Nine isolates were characterized as HAdV-3 genome type a2.

CONCLUSIONS

Considering the limited mobility of residents and their reliance on respiratory care, transmission of HAdV-3 infection during this outbreak likely occurred through respiratory care provided by staff. In environments where patients with susceptible underlying conditions reside, HAdV infection should be considered when patients are identified with worsening respiratory disease, and rapid diagnostic tests for HAdV infection should be readily available to help identify and curtail the spread of this pathogen.

Adenovirus infections and lung disease

Adenovirus, particularly its E1A protein, has been investigated in the pathogenesis of chronic obstructive pulmonary disease (COPD). High levels of E1A DNA were found in the lungs of COPD patients, where its expression increased with disease severity. In lung epithelial cells, E1A increased intercellular adhesion molecule-1 and interleukin-8 expression, as well as nuclear factor-kappaB activation, in response to inflammatory stimuli. In addition to regulating the mediators that promote emphysema, E1A upregulates transforming growth factor-beta1 expression in bronchiolar epithelial cells and transforms lung epithelial cells to express mesenchymal markers. These results support its additional role in the airway remodeling process reported in COPD.

Enhancement of gene transfer to human myeloid cells by adenovirus-fiber complexes

Adenoviral (Ad) vectors are currently being developed for immunotherapy and vaccine delivery, particularly for cancer and antiviral treatment (e.g., human immunodeficiency virus vaccine). However, the inefficient transduction of antigen-presenting cells of myeloid lineage such as dendritic cells (DCs) by conventional Ad5-based vectors limits these applications. DCs lack the coxsackie and adenovirus receptor but express CD46, a member of the family of complement regulatory proteins, as well as sialic acid glycoconjugates, a situation that allows infection by Ad type 37 as well as most subgroup B Ads. In this study, we generated recombinant Ad fiber knobs (FKs) to probe Ad37 receptor usage on immune cells. Remarkably, treatment of human myeloid cells with Ad37 FK (37FK) enhanced, rather than inhibited transduction by Ad5 or Ad37 pseudotyped virions. The enhanced gene transfer was dose dependent, involved association with alpha(2,6)-linked sialic acid residues, and was limited to blood cells of myeloid lineage, including immature and mature DCs. We also provide evidence that 37FK binds directly to Ad5 virus particles, likely acting as a bridge to facilitate greater virus-cell interaction.

Experimental infections of humans with wild-type adenoviruses and with replication-competent adenovirus vectors: replication, safety, and transmission

Replication-competent (RC) adenoviruses (Ads) are increasingly being developed as oncolytic vectors and as vehicles for delivering vaccine antigens. Although the safety of such vectors in humans is of paramount importance, these vectors pose additional special concerns. Specifically, the prospect of causing Ad-mediated disease in the patient, the amount and sites of Ad replication, the possibility of virus shedding leading to unintended transmission to patient contacts, and the potential for persistence in the inoculated individual must be evaluated. Previous experience with administration of wild-type and RC recombinant Ads to humans may shed light on some of these issues. Experimental infections of humans with natural Ad isolates and RC recombinant vectors show that in adults Ads cause mild or no disease, particularly with Ad serotypes 2 and 5, the serotypes most often used to make recombinant constructs. Other studies show that Ad can replicate in experimentally infected persons, that in some situations Ads can be shed and transmitted to close contacts, and that there is evidence for persistent/latent Ad infection in naturally infected individuals. Overall, these studies indicate that Ads can be safely administered to humans for the treatment of cancer and as antigen delivery vehicles suggesting that the continued development of RC oncolytic and vaccine vectors should be pursued.

Restoration of p53 tumor-suppressor activity in human tumor cells in vitro and in their xenografts in vivo by recombinant avian adenovirus CELO-p53

Human adenovirus (Ad) vectors are extensively used as gene transfer vehicles. However, a serious obstacle for the use of these vectors in clinical applications is due to pre-existing immunity to human Ads affecting the efficacy of gene transfer. One of the approaches to circumvent host immune response could be the development of vectors based on non-human Ads that are able to transduce genes into human cells. In this study, we explored the possibility of using avian Ad CELO vectors as gene-transfer vehicles. For this purpose, we constructed a set of recombinant CELO viruses and demonstrated that they are able to deliver transgenes into various organs on the background of pre-existing immunity to human Ad5. The created CELO-p53 vector restored the function of the p53 tumor suppressor both in cultured human tumor cells in vitro and in their xenografts in nude mice in vivo. The latter effect was accompanied by inhibition of tumor growth. Noteworthily, the delivery of CELO-p53 led to activation of p53 target genes in cells showing inactivation of endogenous p53 by three different mechanisms, that is, in the human epidermoid carcinoma A431, lung adenocarcinoma H1299, and cervical carcinoma HeLa.

The impact of adenovirus infection on the immunocompromised host

Adenovirus (Ad) infections in immunocompromised hosts have increased in frequency as the number of patients with transplants of bone marrow, liver, kidney, heart and other organs increase in number and survive longer. The numbers of such patients have also increased because of the emergence of the HIV epidemic. Ad infections with the 51 different serotypes recognised to date have few pathognomonic signs and symptoms, and thus require a variety of laboratory-based procedures to confirm infection. These viruses have the ability to target various organs with relative serotype specificity and can cause diverse manifestations including serious life-threatening diseases characteristic of the organs involved. Ads have cytolytic and immunoregulatory properties. The clinical dilemma remains the prompt recognition of Ad-related disease, the differentiation of Ad infection from Ad disease and the differentiation from other causative agents. Since the armamentarium of effective antiviral agents available to treat Ads is unproven by controlled trials and the virus is often not acquired de novo, it is difficult to prevent reactivation in immunodeficient hosts or new acquisition from donor organs. Timely discontinuation of immunosuppressive agents is necessary to prevent morbid outcomes. The clinical diseases, diagnostic tests, antiviral agents and biological aspects of the Ads as pathogens in immunocompromised patients are discussed in the context of this review. Some of the newer diagnostic tests are based on the well-studied molecular biology of Ads, which also have been attenuated by selective viral DNA deletions for use as vectors in numerous gene therapy trials in humans.

Identification of contaminating adenovirus type 1 in the ATCC reference strain of respiratory syncytial virus A2 (VR-1302)

ATCC reference strain of respiratory syncytial virus A-2 (VR-1302), which was originally isolated from the lower respiratory tract of an infant (Lewis et al., 'Med. J. Aust. 2 (1961) 932'), is contaminated with adenovirus type 1. The presence of adenovirus was deduced from microscopic observation of CPE in HEp-2 cells and confirmed by electron microscopy, PCR, serological typing and immunofluoresence. Since RSV A2 is used worldwide as a representative virus of RSV type A viruses, and because the ATCC is often cited as the source of the parent stock, we considered it important to bring these findings to the attention of the wider community.

Adenovirus Fiber Disrupts CAR-Mediated Intercellular Adhesion Allowing Virus Escape

Adenovirus binds its receptor (CAR), enters cells, and replicates. It must then escape to the environment to infect a new host. We found that following infection, human airway epithelia first released adenovirus to the basolateral surface. Virus then traveled between epithelial cells to emerge on the apical surface. Adenovirus fiber protein, which is produced during viral replication, facilitated apical escape. Fiber binds CAR, which sits on the basolateral membrane where it maintains tight junction integrity. When fiber bound CAR, it disrupted junctional integrity, allowing virus to filter between the cells and emerge apically. Thus, adenovirus exploits its receptor for two important but distinct steps in its life cycle: entry into host cells and escape across epithelial barriers to the environment.

Sporadic acute respiratory infections in adults with special reference to adenovirus infections

Four out of fifty acute respiratory infections occurring in forty-five adult volunteers in a teaching hospital, from October 1956 to July 1957, were associated with infection by a member of the adenovirus group. In three of these adenovirus infections the clinical picture was quite distinct from that of the common cold, but not from other syndromes of unknown aetiology; in the fourth case the clinical picture was not easily distinguishable from the common cold.

It is suggested on the basis of this study that adenovirus vaccines would do little towards reducing sporadic acute respiratory infections in this type of community.

Complement-fixing and neutralizing antibody patterns to adenovirus Types 1–7, 9 and 10 were determined in paired sera from forty-four of the forty-five volunteers.

I wish to thank all the volunteers who took part in this investigation, Mrs Audrey Rae, A.I.M.L.T., for expert technical assistance, Dr Nuala Crowley and Prof. K. R. Hill, Pathology Department, Royal Free Hospital, Dr H. G. Pereira, National Institute for Medical Research, Mill Hill, and Dr F. K. Sanders, M.R.C. Virus Research Unit, London School of Hygiene, for advice and help.

Intracellular localization of type 4 adenovirus. I. Cellular fractionation studies

HeLa cells infected with types 1 or 4 adenovirus were separated into cytoplasmic and nuclear fractions by mechanical disruption and differential centrifugation and the quantity of infectious virus in each was determined. The results showed that the majority of infectious virus of both types could be isolated in the cytoplasmic fraction. It was not possible to explain the large amount of type 4 virus in the cytoplasmic fraction by the number of nuclei disrupted in the fractionation procedure, but the amount of type 1 virus in the cytoplasmic fraction could have been contributed by disrupted nuclei. This suggested that there might be a basic difference in the intracellular formation of the two types of virus. The intracellular distribution of complement-fixing antigen was similar to that of infectious virus in type 4-infected cells. Technical difficulties, inherent in cellular fractionation studies, were encountered but did not appear to explain the results obtained.

Ovine adenovirus vectors overcome preexisting humoral immunity against human adenoviruses in vivo

Recombinant human adenoviruses (hAd) have become widely used as tools to achieve efficient gene transfer. However, successful application of hAd-derived vectors in clinical trials is limited due to immunological and potential safety problems inherent in their human origin. In this study, we describe a recombinant ovine adenovirus (OAV) as an alternative vector for gene transfer in vivo. In contrast to an hAd vector, the OAV vector was not neutralized by human sera. An OAV vector which contained the cDNA of the human alpha1-antitrypsin (hAAT) gene linked to the Rous sarcoma virus promoter was generated and administered systemically to mice. The level and duration of hAAT gene expression was similar to that achieved with an hAd counterpart in both immunocompetent and immunodeficient mice. However, the tissue distribution of the OAV vector differed from that observed for hAd vectors in that the liver was not the dominant target. Significantly, we demonstrated efficient gene transfer with the OAV vector into mice immunized with hAd vectors and vice versa. We also confirm that the immune response to a transgene product can prevent its functional expression following sequential application of a vector. Our results suggest a possible solution to endemic humoral immunity against currently used hAd vectors and should therefore have an impact on the design of improved gene therapy protocols utilizing adenovirus vectors.

Variability of human systemic humoral immune responses to adenovirus gene transfer vectors administered to different organs

Administration of adenovirus (Ad) vectors to immunologically naive experimental animals almost invariably results in the induction of systemic anti-Ad neutralizing antibodies. To determine if the human systemic humoral host responses to Ad vectors follow a similar pattern, we evaluated the systemic (serum) anti-Ad serotype 5 (Ad5) neutralizing antibodies in humans after administration of first generation (E1(-) E3(-)) Ad5-based gene transfer vectors to different hosts. AdGVCFTR.10 (carrying the normal human cystic fibrosis [CF] transmembrane regulator cDNA) was sprayed (8 x 10(7) to 2 x 10(10) particle units [PU]) repetitively (every 3 months or every 2 weeks) to the airway epithelium of 15 individuals with CF. AdGVCD.10 (carrying the Escherichia coli cytosine deaminase gene) was administered (8 x 10(8) to 8 x 10(9) PU; once a week, twice) directly to liver metastasis of five individuals with colon cancer and by the intradermal route (8 x 10(7) to 8 x 10(9) PU, single administration) to six healthy individuals. AdGVVEGF121.10 (carrying the human vascular endothelial growth factor 121 cDNA) was administered (4 x 10(8) to 4 x 10(9.5) PU, single administration) directly to the myocardium of 11 individuals with ischemic heart disease. Ad vector administration to the airways of individuals with CF evoked no or minimal serum neutralizing antibodies, even with repetitive administration. In contrast, intratumor administration of an Ad vector to individuals with metastatic colon cancer resulted in a robust antibody response, with anti-Ad neutralizing antibody titers of 10(2) to >10(4). Healthy individuals responded to single intradermal Ad vector variably, from induction of no neutralizing anti-Ad antibodies to titers of 5 x 10(3). Likewise, individuals with ischemic heart disease had a variable response to single intramyocardial vector administration, ranging from minimal neutralizing antibody levels to titers of 10(4). Evaluation of the data from all trials showed no correlation between the peak serum neutralizing anti-Ad response and the dose of Ad vector administered (P > 0.1, all comparisons). In contrast, there was a striking correlation between the peak anti-Ad5 neutralizing antibody levels evoked by vector administration and the level of preexisting anti-Ad5 antibodies (P = 0.0001). Thus, unlike the case for experimental animals, administration of Ad vectors to humans does not invariably evoke a systemic anti-Ad neutralizing antibody response. In humans, the extent of the response is dictated by preexisting antibody titers and modified by route of administration but is not dose dependent. Since the extent of anti-Ad neutralizing antibodies will likely modify the efficacy of administration of Ad vectors, these observations are of fundamental importance in designing human gene therapy trials and in interpreting the efficacy of Ad vector-mediated gene transfer.

The distribution of adenovirus antibodies in normal children

The levels of neutralizing antibody against several adenovirus serotypes were determined on 42 paired specimens of maternal and cord serum and on 197 single serum specimens from children up to the age of 8 years.

The antibody distribution indicates that adenovirus infection is endemic in Sheffield just as it has been shown to be endemic in Cleveland and Washington.

We should like to thank Prof. C. P. Beattie for his advice and criticism, Dr C. C. Bowley of the Sheffield Regional Blood Transfusion Centre for paired maternal and cord sera, Dr M. H. Hambling for the provision of adenovirus stock strains and Mr Foster, medical artist, for preparation of the figures.

Cytological aspects of antimicrobial antibiosis. I. Cytological changes associated with the exposure of Escherichia coli to colistin sulfate

Chapman, George B. (Cornell University Medical College, New York, N.Y.). Cytological aspects of antimicrobial antibiosis. I. Cytological changes associated with the exposure of Escherichia coli to colistin sulfate. J. Bacteriol. 84:169-179. 1962-Broth cultures of Escherichia coli were exposed to different concentrations of the antibiotic colistin sulfate for various lengths of time. Control (untreated) and treated cells were fixed, dehydrated, and embedded in methacrylate or Epon. Ultrathin sections were examined in an RCA EMU2-D electron microscope. Two conspicuous cytological changes were noted. First, the nuclear material disappeared from its normal sites and was no longer demonstrable. Second, the cytoplasm lost its granularity and became homogeneous. Cells which showed these changes were nonviable.

Respiratory viruses in a residential nursery

A longitudinal survey of respiratory illness in a Sheffield residential nursery is described. Over 8 months, outbreaks of respiratory illness occurred, two of which were associated with infection by Influenza A and Parainfluenza 3 viruses. The symptomatology is described of the illnesses resulting from these infections. The incidence of adenovirus recoveries over the same period was also investigated and suggests that adenoviruses of Types 1, 2 and 5 may be components of the normal viral flora of the nasopharynx in infants.

Seroepidemiology of new AIDS-associated adenoviruses among the San Francisco Men's Health Study

A seroprevalence survey to recently proposed adenovirus (AV) serotypes AV 48 and AV 49, isolated primarily from AIDS patients, was conducted among the San Francisco Men's Health Study cohort. This cohort of homosexual, heterosexual, or bisexual HIV-seronegative and -seropositive men from selected San Francisco census tracts has been studied since 1984. The presence or absence of type-specific antibody in 628 serum specimens from 1989 was determined by microneutralization. Thirty of these subjects (26 positive and four negative) were studied longitudinally. Serum specimens taken at 6-month intervals from 1984 to 1993 were tested to characterize antibody response and to document the advent of these new serotypes. Eight subjects were tested against five other AV serotypes for comparison. AV 48 and AV 49 seroprevalence rates were significantly higher in HIV-seropositives, but infection was not limited to the immunocompromised. Sexual preference was not a significant determinant for AV seroprevalence in HIV-seronegatives. However, the extent and duration of the neutralizing antibody response was strikingly different between homosexuals and heterosexuals: an endemic pattern of continuous reexposure over the 9-year period was seen in 90% of 19 homosexuals, while five of six heterosexuals (83%) had an episodic pattern of exposure with antibody decline to undetectable levels. These data suggest that these viruses may be endemic in some part of the homosexual population and that sexual transmission may be the primary source of continuous reexposure.

Molecular epidemiology of adenovirus types 3 and 7 isolated from children with pneumonia in Beijing

One hundred fifty strains of adenovirus sero-types 3 (Ad3) and 7 (Ad7) were analyzed. The viruses were isolated from patients, the majority of whom had pneumonia, from central and sub-urban Beijing over a 33-year period (1958-1990). Genomic analysis of DNA extracted from 74 strains of Ad3 and 76 strains of Ad7, with four to five restriction endonucleases (REs), revealed the presence of four and eight genome types, respectively: Ad3a2, Ad3a4, Ad3a5, Ad3a6 and Ad7p1, Ad7a1, Ad7a4, Ad7b, Ad7b1, Ad7d, Ad7d1, and Ad7g. Ad7b1 was the most recently identified genome type. The restriction patterns obtained from 19 representatives of Ad7 genome types after cleavage of the DNA with 12 REs are shown. Ad3a2 first appeared in 1962, and predominated from 1983 to 1988. Ad3a4 was the main causative agent of pneumonia in 1982. Ad3a2 and Ad3a4 are closely related and have 97% pairwise comigrating restriction fragments (PCRF). Ad7d predominated over a period of 11 years (1980-1990). It has 98% PCRF with Ad7b. Ten pairs of strains isolated from different specimens of the same patients were all concordant.

Adenovirus infection of the kidney: mass formation in a patient with Hodgkin's disease

Adenovirus (AV) infection usually has a benign course in normal hosts; however, in immunocompromised patients, AV may cause pneumonia, cystitis, or disseminated disease with substantial morbidity and even mortality. Although pulmonic AV involvement is common, infection of the kidney is unusual. The histologic findings previously described include tubular necrosis with interstitial inflammation and glomerulonephritis. We report a case of an AV-induced unilateral mass lesion in the kidney of a patient with Hodgkin's disease (HD) following bone marrow transplantation.

Comparison of 17 genome types of adenovirus type 3 identified among strains recovered from six continents

Restriction endonucleases BamHI, BclI, BglI, BglII, BstEII, EcoRI, HindIII, HpaI, SalI, SmalI, XbalI, and XholI were used to analyze 61 selected strains of adenovirus type 3 (Ad3) isolated from Africa, Asia, Australia, Europe, North America, and South America. It was noted that the use of BamHI, BclI, BglII, HpaI, SalI, and SmaI was sufficient to distinguish 17 genome types; 13 of them were newly identified. All 17 Ad3 genome types could be divided into three genomic clusters. Genome types of Ad3 cluster 1 occurred in Africa, Europe, South America, and North America. Genomic cluster 2 was identified in Africa; genomic cluster 3 was identified in Africa, Asia, Australia, Europe (a few), and North America. This was of interest because 15 identified genome types of Ad7 could also be divided into three genomic clusters. The degree of genetic relatedness between the 17 Ad3 and the 15 Ad7 genome types was analyzed and was expressed in a three-dimensional model.

Corneal subepithelial infiltrates associated with systemic Epstein-Barr viral infection

Corneal subepithelial infiltration resembling adenoviral keratitis developed in two patients with serologic evidence of systemic Epstein-Barr viral (EBV) infection and nondetectable antibody levels for adenovirus (ADV). These cases suggest that EBV is capable of mimicking more commonly recognized corneal infectious disease entities.