Thirty-one human adenovirus serotypes (Ad1-Ad31) form five groups (A-E) based upon DNA genome homologies

Immune evasion by adenoviruses: a window into host-virus adaptation

Human adenoviruses (HAdVs) are widespread pathogens that cause a number of partially overlapping, species-specific infections associated with respiratory, urinary, gastrointestinal, and ocular diseases. The early 3 (E3) region of adenoviruses is highly divergent between different species, and it encodes a multitude of proteins with immunomodulatory functions. The study of genetic diversity in the E3 region offers a unique opportunity to gain insight into how the various HAdVs have evolutionarily adapted in response to the selection pressures exerted by host immune defenses. The objective of this review was to discuss subversion of host antiviral immune responses by HAdVs, with a focus on suppression of MHC class I antigen presentation, as a window into host-HAdV adaptation.

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.

Outbreak of febrile respiratory illness associated with human adenovirus type 14p1 in Gansu Province, China

Objectives

Human adenovirus (HAdV) type 14 had been infrequently associated with outbreaks of febrile respiratory illness (FRI) until the HAdV‐14p1 emerged in 2006 and rapidly spread in the United States. Here, we report an outbreak of FRI caused by HadV‐14p1 that occurred in 2011 at a primary and middle school in China.

Design

The basic information of the outbreak was recored; throat swabs were collected from 17 patients, polymerase chain reaction, A549 cell culture, and sequencing were used to identify the pathogen of the outbreak..

Results

Total of 43 students were infected in this outbreak. Boys were more than girls. We identified 11 HAdV‐positive specimens and 6 HAdV isolates. Genetic analysis showed that the complete hexon, fiber, and E1A sequences of isolates were nearly 100% identical with other HAdV‐14p1 sequences deposited in GenBank.

Conclusions

HadV‐14p1 has caused outbreaks of pneumonia and mortality among adults in the United States and Europe. It may cause similar conditions among Chinese adults due to poor hygiene and sanitation. It seems prudent for China to develop a national surveillance system to determine the etiology of severe respiratory diseases and deaths among adults and school‐aged children.

Human adenovirus infection in children with acute respiratory tract disease in Guangzhou, China

Acute respiratory infections (ARI) are the major worldwide health problem due to associated high morbidity and mortality rates. Adenovirus (Adv) is one of the most common causes of viral ARI, and thus calls for specific diagnosis and better understanding of the epidemiology and clinical characteristics. Our aims were to find out the status of Adv infection in children <14 years with ARI, analyze the epidemiology and clinical characteristics among the Adv‐infected children in Guangzhou, China, and to provide some basis for the research of Adv. The throat and pharyngeal swabs were collected among the children with acute respiratory tract infections in outpatient department from September 2006 to August 2008. The samples were analyzed by PCR and the sequences were blasted with the sequences of Adv in GenBank. Clinical data were analyzed along with virological data by using appropriate statistical methods. Adv was detected in 25 out of 512 (4.9%) children. The genome types of 23 samples were determined after analysis of the gene sequence. The most prevalent Adv type was species B type 3. Among the patients, 10 were of Ad3 (43.5%), three were of Ad1 (1.3%), five were of species C Ad2 (21.7%), and five were of species E Ad4 (21.7%). A higher incidence of positive results was found during the summer season, thus showing a pattern of seasonality. There exists Adv infection in children with acute respiratory system diseases in Guangzhou area. No significant differences were found among different age groups and gender groups. Co‐infections with other respiratory virus were detected in 64% of the Adv positive samples.

Construction and characterization of human adenovirus serotype 3 packaged by serotype 7 hexon

Human adenovirus serotype 3 (Ad3) and serotype 7 (Ad7) are important pathogens causing respiratory tract diseases such as acute respiratory disease in pediatric and adult patients, but the immunodominant targets of Ad3- and Ad7-specific neutralizing antibodies (NAbs) remain unclear. A chimeric Ad vector, Ad3/H7, was constructed by replacing the Ad3 hexon gene (H3) with the hexon gene (H7) of Ad7. The chimeric viruses were successfully rescued in HEp-2 cells, and the Ad7 hexon was able to encapsidate the Ad3 genome, and functioned as efficiently as the Ad3 hexon. Furthermore, we tested the host neutralization responses against the viruses using BALB/C mice. Up to 97% of the NAbs produced by mice that were infected with these viruses were specific for the hexon protein in vitro. Preimmunization of mice with one of Ad7 and Ad3/H7 significantly prevented subsequent intranasal infection of the other type in vivo. In contrast, preimmunization of mice with one of Ad3 and Ad3/H7 did not remarkably prevent subsequent infection of the other type. We next evaluated the functional significance of hexon and other structural proteins specific NAbs to suppress the immunogenicity of Ad3/H3 and Ad3/H7 vectors expressing EGFP in mice preimmunized with wild type Ad. Preimmunization of mice with Ad7 evidently suppressed EGFP-specific humoral immune responses elicited by Ad3/H7, and did not exert suppressive effects on Ad3/H3. But contrary to the in vitro neutralization results, EGFP-specific humoral immune responses elicited by Ad3/H7 was remarkably inhibited in Ad3-preimmunization mice. The whole genome of the Ad7 strain was sequenced and aligned with Ad3. The major differences between Ad3 and Ad7 were only observed in the fiber and hexon among all structural proteins, and the variation between the hexons only located in four hypervariable regions (HVRs), HVR-1, -2, -5, and -7. These results thus suggest that Ad3- and Ad7-specific NAbs are directed primarily against the hexon proteins both in vitro and in vivo. But high titer Ad3 fiber-specific NAbs may also play an important role in blunting Ad3 immunogenicity in vivo. These studies contribute to a more profound understanding of Ad immunogenicity and have relevance for the design of novel Ad vaccine.

Adenovirus E3-19K proteins of different serotypes and subgroups have similar, yet distinct, immunomodulatory functions toward major histocompatibility class I molecules

Our understanding of the mechanism by which the E3-19K protein from adenovirus (Ad) targets major histocompatibility complex (MHC) class I molecules for retention in the endoplasmic reticulum is derived largely from studies of Ad serotype 2 (subgroup C). It is not well understood to what extent observations on the Ad2 E3-19K/MHC I association can be generalized to E3-19K proteins of other serotypes and subgroups. The low levels of amino acid sequence homology between E3-19K proteins suggest that these proteins are likely to manifest distinct MHC I binding properties. This information is important as the E3-19K/MHC I interaction is thought to play a critical role in enabling Ads to cause persistent infections. Here, we characterized interaction between E3-19K proteins of serotypes 7 and 35 (subgroup B), 5 (subgroup C), 37 (subgroup D), and 4 (subgroup E) and a panel of HLA-A, -B, and -C molecules using native gel, surface plasmon resonance (SPR), and flow cytometry. Results show that all E3-19K proteins exhibited allele specificity toward HLA-A and -B molecules; this was less evident for Ad37 E3-19K. The allele specificity for HLA-A molecules was remarkably similar for different serotypes of subgroup B as well as subgroup C. Interestingly, all E3-19K proteins characterized also exhibited MHC I locus specificity. Importantly, we show that Lys(91) in the conserved region of Ad2 E3-19K targets the C terminus of the α2-helix (MHC residue 177) on MHC class I molecules. From our data, we propose a model of interaction between E3-19K and MHC class I molecules.

Determinants of the endoplasmic reticulum (ER) lumenal-domain of the adenovirus serotype 2 E3-19K protein for association with and ER-retention of major histocompatibility complex class I molecules

The E3-19K immunomodulatory protein from adenoviruses (Ads) inhibits antigen presentation by major histocompatibility complex (MHC) class I molecules. As a result, the ability of Ad-specific cytotoxic T lymphocytes (CTLs) to lyse infected cells is suppressed. The ER-lumenal domain of E3-19K is subdivided into a variable (residues 1 to ∼78/81) and conserved (residues ∼79/82 to 98) region followed by a linker (residues 99-107). Using molecular and cellular approaches, we characterized in detail the properties of the ER-lumenal domain of E3-19K that enable it to target MHC class I molecules. Proteolysis of recombinant serotype 2 E3-19K (residues 1-100) (with six His residues) generated a large N-terminal (residues 1-88) and a small C-terminal fragment (residues 94-100) in solution. Neither of these fragments associates with HLA-A*1101 as shown by a native gel band-shift assay. In contrast, the N-terminal 1-93 residues of Ad2 E3-19K exhibited the same binding affinity to HLA-A*1101 as E3-19K. Using a site-directed mutational analysis and flow cytometry, we show that Tyr(93), but not Tyr(88), critically modulates the cell-surface expression of MHC class I molecules. Taken together, these results indicate that the sequence comprising residues 89-93 (M(89)SKQY(93)), and in particular Tyr(93), in the conserved region of E3-19K is critical for its immunomodulatory function. Residues 89-93 likely form a linker or loop in E3-19K. Overall, our data provide novel insights into the structure of E3-19K and identify key determinants for association with and ER-retention of its cellular target protein. This knowledge is important for our understanding of the molecular basis of Ad pathogenesis.

Tropism-modification strategies for targeted gene delivery using adenoviral vectors

Achieving high efficiency, targeted gene delivery with adenoviral vectors is a long-standing goal in the field of clinical gene therapy. To achieve this, platform vectors must combine efficient retargeting strategies with detargeting modifications to ablate native receptor binding (i.e. CAR/integrins/heparan sulfate proteoglycans) and “bridging” interactions. “Bridging” interactions refer to coagulation factor binding, namely coagulation factor X (FX), which bridges hepatocyte transduction in vivo through engagement with surface expressed heparan sulfate proteoglycans (HSPGs). These interactions can contribute to the off-target sequestration of Ad5 in the liver and its characteristic dose-limiting hepatotoxicity, thereby significantly limiting the in vivo targeting efficiency and clinical potential of Ad5-based therapeutics. To date, various approaches to retargeting adenoviruses (Ad) have been described. These include genetic modification strategies to incorporate peptide ligands (within fiber knob domain, fiber shaft, penton base, pIX or hexon), pseudotyping of capsid proteins to include whole fiber substitutions or fiber knob chimeras, pseudotyping with non-human Ad species or with capsid proteins derived from other viral families, hexon hypervariable region (HVR) substitutions and adapter-based conjugation/crosslinking of scFv, growth factors or monoclonal antibodies directed against surface-expressed target antigens. In order to maximize retargeting, strategies which permit detargeting from undesirable interactions between the Ad capsid and components of the circulatory system (e.g. coagulation factors, erythrocytes, pre-existing neutralizing antibodies), can be employed simultaneously. Detargeting can be achieved by genetic ablation of native receptor-binding determinants, ablation of “bridging interactions” such as those which occur between the hexon of Ad5 and coagulation factor X (FX), or alternatively, through the use of polymer-coated “stealth” vectors which avoid these interactions. Simultaneous retargeting and detargeting can be achieved by combining multiple genetic and/or chemical modifications.

Genome sequences of human adenovirus 14 isolates from mild respiratory cases and a fatal pneumonia, isolated during 2006-2007 epidemics in North America

Background

Human adenovirus 14 (HAdV-14) is a recognized causative agent of epidemic febrile respiratory illness (FRI). Last reported in Eurasia in 1963, this virus has since been conspicuously absent in broad surveys, and was never isolated in North America despite inclusion of specific tests for this serotype in surveillance methods. In 2006 and 2007, this virus suddenly emerged in North America, causing high attack rate epidemics of FRI and, in some cases, severe pneumonias and occasional fatalities. Some outbreaks have been relatively mild, with low rates of progression beyond uncomplicated FRI, while other outbreaks have involved high rates of more serious outcomes.

Methodology and Findings

In this paper we present the complete genomic sequence of this emerging pathogen, and compare genomic sequences of isolates from both mild and severe outbreaks. We also compare the genome sequences of the recent isolates with those of the prototype HAdV-14 that circulated in Eurasia 30 years ago and the closely related sequence of HAdV-11a, which has been circulating in southeast Asia.

Conclusions

The data suggest that the currently circulating strain of HAdV-14 is closely related to the historically recognized prototype throughout its genome, though it does display a couple of potentially functional mutations in the fiber knob and E1A genes. There are no polymorphisms that suggest an obvious explanation for the divergence in severity between outbreak events, suggesting that differences in outcome are more likely environmental or host determined rather than viral genetics.

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

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

Cell polarity proteins: common targets for tumorigenic human viruses

Loss of polarity and disruption of cell junctions are common features of epithelial-derived cancer cells, and mounting evidence indicates that such defects have a direct function in the pathology of cancer. Supporting this idea, results with several different human tumor viruses indicate that their oncogenic potential depends in part on a common ability to inactivate key cell polarity proteins. For example, adenovirus (Ad) type 9 is unique among human Ads by causing exclusively estrogen-dependent mammary tumors in experimental animals and in having E4 region-encoded open reading frame 1 (E4-ORF1) as its primary oncogenic determinant. The 125-residue E4-ORF1 protein consists of two separate protein-interaction elements, one of which defines a PDZ domain-binding motif (PBM) required for E4-ORF1 to induce both cellular transformation in vitro and tumorigenesis in vivo. Most notably, the E4-ORF1 PBM mediates interactions with a selected group of cellular PDZ proteins, three of which include the cell polarity proteins Dlg1, PATJ and ZO-2. Data further indicate that these interactions promote disruption of cell junctions and a loss of cell polarity. In addition, one or more of the E4-ORF1-interacting cell polarity proteins, as well as the cell polarity protein Scribble, are common targets for the high-risk human papillomavirus (HPV) E6 or human T-cell leukemia virus type 1 (HTLV-1) Tax oncoproteins. Underscoring the significance of these observations, in humans, high-risk HPV and HTLV-1 are causative agents for cervical cancer and adult T-cell leukemia, respectively. Consequently, human tumor viruses should serve as powerful tools for deciphering mechanisms whereby disruption of cell junctions and loss of cell polarity contribute to the development of many human cancers. This review article discusses evidence supporting this hypothesis, with an emphasis on the human Ad E4-ORF1 oncoprotein.

Human adenoviruses: propagation, purification, quantification, and storage

Detailed protocols are described for the propagation of adenoviruses (Ads) and adenovirus (Ad) vectors and their purification by CsCl equilibrium density gradient centrifugation. A discussion of monolayer and spinner cell culture techniques suitable, respectively, for small- and large-scale growth of adenoviruses is provided. Protocols for cloning into and growth of Ad replication-deficient vectors using a convenient commercially available system are described. Lastly, time-tested plaque titration protocols for the accurate and convenient measurement of the infectivity of adenoviruses and adenovirus vectors are provided in detail.

Classification of the papillomaviruses--mapping the genome

Papillomaviruses form one genus of the Papovaviridae family. They share common antigenic determinants and their DNAs cross-hybridize under conditions of low stringency. The classification of papillomaviruses is at present based on the host range and the relatedness of the nucleic acids. Isolates are considered independent types if there is less than 50% cross-hybridization in the liquid phase according to a standard protocol. At least 31 human and six bovine papillomavirus types can be differentiated on this basis. The host range does not reflect the natural relationship between the viruses. Subgenera, which differ in biological properties, can be distinguished in outline. Data on overall sequence homology are insufficient for a meaningful classification because two types of virus may be closely related within one genome region and rather heterogeneous in other areas. Some new isolates appear as intermediates between previously well-separated types and complicate the system. A reasonable classification of such types of papillomavirus should be based on homologies between genes that are relevant for differences in the biology of the viruses. A functional mapping of the rather uniformly organized, colinear genomes of papillomaviruses has been started. Genetic studies with bovine papillomavirus type 1 have assigned functions in replication, transformation, gene expression and capsid synthesis to individual open reading frames.

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

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

PCR analysis of egyptian respiratory adenovirus isolates, including identification of species, serotypes, and coinfections

Eighty-eight adenovirus (Ad) isolates and associated clinical data were collected from walk-in patients with influenza-like illness in Egypt during routine influenza surveillance from 1999 through 2002. Respiratory Ad distributions are geographically variable, and serotype prevalence has not been previously characterized in this region. Serotype identity is clinically relevant because it predicts vaccine efficacy and correlates strongly with both clinical presentation and epidemiological pattern. Species and serotype identities were determined using several well-validated multiplex PCR protocols culled from the literature and supplemented with a few novel primer sets designed to identify rare types. The isolates included common species B1 serotypes (Ad3 and Ad7), common species C serotypes (Ad1, Ad2, and Ad5), the less common species B2 serotype Ad11, and three isolates of the rare species B1 serotype Ad16. Two isolates that appear to be variant Ad16 were also identified. Fifteen coinfections of multiple adenoviral types, primarily AdB/AdC and Ad3/Ad7 dual infections, were detected. The majority of these were verified using redundant PCR tests targeted at multiple genes. PCR is able to resolve coinfections, in contrast to traditional serum neutralization tests. PCR is also comparatively rapid and requires very little equipment. Application of the method allowed an inclusive determination of the serotypes found in the Egyptian respiratory sample set and demonstrated that coinfections are common and may play a previously unrecognized role in adenovirus pathogenesis, evolution, and epidemiology. In particular, coinfections may influence adenoviral evolution, as interserotypic recombination has been identified as a source of emerging strains.

Cross-reactivity between human adenoviruses in delayed-type hypersensitivity

The aim of this study was to determine the antigen responsible for the induction of delayed-type hypersensitivity (DTH) by human adenoviruses (Ads). The estimation of DTH was based on measurement of the extent of swelling of the hind footpads of mice. CsCl density gradient-purified human Ad serotype 6 (Ad6) induced DTH in a dose-dependent manner. In Ad6-sensitized mice, DTH could be elicited by serotypes belonging to the same species of human Ads (types 1 and 5) and by a serotype (type 3) belonging to another species. Latex particles coated with purified hexon antigen prepared from Ad5 had the capacity to sensitize mice and elicit a DTH reaction. We suggest that, for serotypes belonging to species C, the cross-reactive highly conserved T cell epitope of the hexon protein might be responsible for the DTH induction, and furthermore the same epitope might result in the cross-reactivity between serotypes 3 and 6. The possible importance of these data is discussed in relation to human gene therapy through the application of Ad vectors.

Human adenovirus type 35: nucleotide sequence and vector development

In this report, we describe the complete 34,794 base pair genomic sequence of the human adenovirus serotype 35 (Ad35) Holden strain. The viral genome exhibits a compact organization similar to other adenoviral serotypes, with overlapping genes on both strands. In all, 47 open reading frames (ORFs) were identified, including early (E1, 2, 3, 4) and late (L1, 2, 3, 4, 5) regions conserved among the adenoviridae family. In addition, 14 ORFs were identified that do not encode known adenoviral genes. Comparison of the predicted translational products of the conserved genes with those of other adenoviruses revealed that Ad35 has high homology to Ad7, Ad3, Ad21, Ad17, and simian Ads25. Based on the complete Ad35 DNA sequence, E3-, E1-, and E1/E3-deleted Ad35-based vector systems were developed. An HEK293-derived cell line was established for the propagation of the E1-deleted Ad35 vector, avoiding the emergence of replication-competent adenovirus. Moreover, production of the E1-deleted recombinant Ad35 vector was achieved by transient transduction of a plasmid encoding the Ad35 E1B gene in HEK293 cells. Testing showed that the Ad35-based vector efficiently infects both human and rhesus macaque dendritic cells. Our novel Ad35-based vectors and their corresponding packaging cell lines will provide a versatile and powerful system for DNA-based vaccine development and gene therapy applications.

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

Adenovirus type 11 (Ad11), a member of the human adenovirus species B (HAdV-B), has a tropism for the urinary tract. The genome of Ad11 was found to comprise 34 794 bp and is 1141 bp shorter than the Ad5 genome of species HAdV-C. The G+C content of the Ad11 genome is 48.9 %, whereas that of Ad5 is 55.2 %. Ad11 and Ad5 share 57 % nucleotide identity and possess the same four early regions, but the E3 region of Ad11 could not be divided into E3A and E3B. The late genes of Ad11 and Ad5 are organized into six and five regions, respectively. Thirty-eight putative ORFs were identified in the Ad11 genome. The ORFs in the late regions, the E2B region and IVa2 show high amino acid identity between Ad11 and Ad5, whereas the ORFs in E1, E2A, E3 and E4, protein IX and the fibre protein show low amino acid identity. The highest and lowest identities were noted in the pre-terminal protein and fibre proteins: 85 % and 24.6 %, respectively. The E3 20.3K and 20.6K ORFs and the L6 agnoprotein were present in the Ad11 genome only, whereas the E3 11.6K cell death protein was identified only in Ad5. All ORFs but the E3 10.3K and L4 pVIII protein vary not only in composition but also in size. Ad11 may have a higher vector capacity than Ad5, since it has a shorter genome and a shorter fibre. Furthermore, in the E3 region, two additional ORFs can be deleted to give extra capacity for foreign DNA.

Evaluation of accuracy and precision of adenovirus absorptivity at 260 nm under conditions of complete DNA disruption

A simple, accurate, and precise method to determine adenovirus particle concentration using 260-nm absorbance was developed as an enhancement to the method of Maizel et al. (1968, Virology 36, 115-125). This modified method ensures complete disruption of virus particles and viral DNA prior to absorbance measurements, therefore eliminating absorbance measurement errors due to hyperchromic shift and thus providing an extinction coefficient at 260 nm that is directly related to protein concentration as measured by the method of Lowry et al. (1951, J. Biol. Chem. 193, 265-275). Application of this modified method will reduce interlaboratory variability in determining adenovirus particle concentrations, as current practices reflected in the literature utilize varying sample preparation procedures and calculation methods which cause underestimation of adenovirus concentration by almost twofold. The sample pretreatment conditions used in this modified method entail incubation in 1% sodium dodecyl sulfate at 100 degrees C for 4 min and result in an adenovirus 260-nm absorptivity of 1.8 x 10(12) viral particles per milliliter per absorbance unit in a 1-cm-pathlength cell.

Construction of an adenovirus type 7a E1A- vector

A strategy for constructing replication-defective adenovirus vectors from non-subgroup C viruses has been successfully demonstrated with adenovirus type 7 strain a (Ad7a) as the prototype. An E1A-deleted Ad7a reporter virus expressing the chloramphenicol acetyltransferase (CAT) gene from the cytomegalovirus promoter enhancer was constructed with DNA fragments isolated from Ad7a, an Ad7a recombination reporter plasmid, and the 293 cell line. The Ad7a-CAT virus particle transduces A549 cells as efficiently as Ad5-based vectors. Intravenous infections in a murine model indicate that the Ad7a-CAT virus infects a variety of tissues, with maximal levels of CAT gene expression found in the liver. The duration of Ad7a-CAT transgene expression in the liver was maximally maintained 2 weeks postinfection, with a decline to baseline activity by the week 4 postinfection. Ad7a-CAT represents the first example of a non-subgroup C E1A- adenovirus gene transfer vector.

Detection of adenovirus DNA in peripheral blood mononuclear cells by polymerase chain reaction assay

Adenovirus can establish persistent infections which may reactivate and cause disease in immunocompromised hosts. Lymphocytes have been postulated to serve as a site of adenoviral persistence based upon the ability to isolate adenovirus from tonsils and to detect adenovirus DNA by Southern blot hybridization in peripheral blood mononuclear cells (PBMC). To test this hypothesis, a more sensitive and specific polymerase chain reaction (PCR) assay was developed to detect adenovirus DNA. Two sets of nested primers were designed to conserved sequences in the adenovirus E1A and hexon genes. The E1A and hexon primers amplified DNA from representative adenoviral serotypes in all six adenoviral groups (A-F). Both primers detected a single copy of the adenovirus type 2 genome but were less sensitive for the group B type 35. None of 33 PBMC specimens from healthy adults and only one of 40 pediatric samples was positive (at a low level) for adenovirus DNA by nested PCR assay. In comparison, PBMC from two children with fatal adenoviral infection were both strongly positive for adenovirus DNA. It is concluded that, in contrast to a previous study, PBMC are not a common site of persistent group C adenoviral infection. In addition, assay of PBMC by the adenovirus-specific PCR may help detect early invasive disease and warrants further evaluation.

Molecular basis of immune evasion strategies by adenoviruses

Human adenoviruses have provided valuable insights into virus-host interactions at the clinical and experimental levels. In addition to the medical importance of adenoviruses in acute infections and the ability of the virus to persist in the host, adenovirus-based recombinants are being developed as potential vaccine vectors. It is now clear that adenoviruses employ various strategies to modulate the innate and the adaptive host immune defences. Adenovirus genome-coded products that interact with the immune response of the host have been identified, and to a large extent the molecular mechanisms of their functions have been revealed. Such knowledge will no doubt influence our approach to the areas of viral pathogenesis, vaccine development and immune modulation for disease management.

Comparative analysis of adenovirus fiber-cell interaction: adenovirus type 2 (Ad2) and Ad9 utilize the same cellular fiber receptor but use different binding strategies for attachment

We have analyzed the binding of adenovirus (Ad) serotypes from subgroups B, C, and D through fiber-virus and fiber-fiber cross-competition experiments. Since viruses in these distinct subgroups display markedly different tropisms, it was unexpected that the subgroup C viruses Ad2 and 5 and the subgroup D virus Ad9 cross-competed for the same cellular fiber receptor. The subgroup B serotype Ad3 recognized a receptor distinct from the Ad2, 5, and 9 fiber receptor. However, despite sharing the same fiber receptor, Ad2 and Ad9 displayed markedly different binding characteristics that appeared to result from direct Ad9 binding to cells via alpha(v)-integrins. Unlike Ad2, Ad9 binding to many cell lines was not abrogated by competition with the fiber 9 knob (F9K). Ad9 binding to fiber receptor-deficient cells was blocked by a monoclonal antibody to alpha(v)-integrins. In contrast, Ad9 binding to alpha(v)-deficient cells that express fiber receptor was blocked by F9K. Transfection of an alpha(v)-integrin-deficient cell line with a plasmid that expresses alpha(v)beta5 resulted in Ad9 binding that was not significantly blocked by F9K but was blocked with a combination of F9K and penton base. These results imply that the shorter length of fiber 9 (11 nm) relative to fiber 2 (37 nm) permits fiber-independent binding of Ad9 penton base to alpha(v)-integrins. The difference in fiber length may explain the different binding characteristics and tissue tropisms of each virus despite both utilizing the same fiber and penton base receptors.

Genome polymorphism of human adenoviruses of subgenus C

The genome of adenovirus (AV) types 1, 2, and 5 is known to be very variable as evidenced by the great number of genome types described (36, 61, and 35 for AV1, 2, and 5 respectively). Physical maps were constructed for nearly all of the restriction or R-variants by biochemical methods and by adapting restriction fragments of defined molecular weight. The alterations found with seven DNA restriction endonucleases were mapped on the genome. Altered restriction sites, found for the genome types of each of the three serotypes, appeared to be randomly distributed over the genome, although mutations seemed to occur preferentially on distinct sites of the genome. Many strains, especially those of AV5, were genomically much more related with one another than with the prototype. This finding is compatible with the interpretation that the related strains were derived from an unknown common ancestor.

Mammary tumors induced by human adenovirus type 9: a role for the viral early region 4 gene

Human adenovirus type 9 (Ad9) elicits exclusively estrogen-dependent mammary tumors when injected into female rats. Three different histological types of mammary tumor (benign fibroadenomas, phyllodes tumors, and malignant solid sarcomas) have been described in Ad9-infected animals, with benign fibroadenomas being seen most frequently. Interestingly, in contrast to other adenoviruses, in which oncogenic viral functions are entirely encoded within the E1 region, Ad9 requires an E4 region transforming protein (ORF1) for its unique mammary oncogenicity. Studies of Ad9-induced rat mammary tumors may lead to a detailed molecular understanding for the development of fibroadenoma, a common human breast tumor.

Immunological and molecular comparison of fowl adenovirus serotypes 4 and 10

Some discussion has centered on whether fowl adenovirus (FAV) serotypes 4 and 10 are distinct serotypes or in fact should be reclassified as a single serotype. We have undertaken a detailed characterisation of representatives of both serotypes in order to determine if types 4 and 10 should be grouped together or retained as distinct serotypes. Examination at the genomic level has revealed considerable similarities and few differences between these 2 serotypes. DNA cross-hybridization failed to distinguish between them and restriction enzyme analysis demonstrated limited sequence differences. In vivo studies demonstrated the cross-protection afforded by a natural route vaccination with serotype 4 FAV when chickens were challenged with serotype 10 FAV. On the basis of these studies it is suggested that these FAV serotypes be combined in future FAV classification. Physical maps for both serotype 4 and 10 have been constructed using the restriction enzymes Hpa I, Dra I, Nde I, Xba I and Not I for both serotypes and in addition Eco RI, Sfi I, Sma I and BglII for serotype 10.

Adenovirus infection enhances in vitro adherence of Streptococcus pneumoniae

Viruses are thought to facilitate bacterial infections of the respiratory tract, but the mechanisms are poorly understood. The present study analyzed the effect of adenovirus on bacterial adherence to human respiratory tract epithelial cells. The human lung carcinoma cell line A549 was infected with adenovirus of types 1, 2, 3, 4, 5, and 9. At a multiplicity of infection of 75 particles per cell, cytopathic effects occurred in 75 to 100% of the cells within 48 h. The virus-infected cells were harvested at various times after infection and analyzed for the ability to bind strains of Haemophilus influenzae and Streptococcus pneumoniae. Adenovirus (types 1, 2, 3, and 5) commonly causing respiratory tract infections increased the binding of adherent S. pneumoniae strains to the cells. This effect was not seen for other adenovirus types. Adenovirus infection did not change the adherence of cells of poorly adhering strains of S. pneumoniae or H. influenzae. The increase in adherence of S. pneumoniae could be inhibited by the DNA synthesis inhibitor cytosine arabinofuranoside, which is known to block the late phase of the adenovirus infection. When electron microscopy was used, there was no evidence that virus particles bound directly to bacteria. Adherence was not affected by pretreatment of the cells with virus particles or viral proteins. This suggested that adenovirus infection upregulated receptors for S. pneumoniae. The increased attachment may be one mechanism by which viruses precondition the respiratory mucosa for bacterial infection.

The hexon genes of adenoviruses of subgenus C: comparison of the variable regions

We report on a 1402-base pair long DNA sequence, encoding for the variable region and parts of the flanking conserved regions of the human adenovirus type 1 (AV1) hexon, and a DNA sequence comprising 1396 base pairs, encoding for the corresponding regions of the human adenovirus type 6 (AV6) hexon. AV1 and AV6, together with AV2 and AV5, belong to subgenus C. Comparison of the predicted amino acid sequences of AV1 and AV6 with those of AV2 and AV5 revealed that the variable hexon region could be subdivided into highly variable, variable and conserved regions. Regions differing between AV2, AV5, AV1 and AV6 were the same as those which were registered as different when comparing AV40 and AV41 (subgenus F), suggesting that these areas of the hexon protein represent type-specific antigenic determinants. Alignment of the amino acid sequences to the known 3-dimensional structure of the AV2 hexon demonstrated that the major amino acid changes were located in the L1 and L2 loops that form the surface of the hexon. Comparison of sequencing data between the serotypes might elucidate questions concerning evolution within subgenus C.

Genome analysis of adenovirus 4 isolated over a six year period

Genome analysis was carried out on 74 adenovirus 4 (Ad4) isolates from patients in Manchester between 1984 and 1989. Most of the isolates were associated with conjunctivitis. Of the 74 isolates studied, 51 were Ad4a and 10 were Ad4p (the prototype strain). The remaining isolates consisted of two new genome types we have designated Ad4a2 (10 isolates) and Ad4a3 (3 isolates). Most of the genome types co-circulated during the period of study. The Bst E II and Xho I restriction maps of the new variants are presented and compared with those of Ad4p. We are unable to associate genome types with particular clinical presentations.

Phylogenetic analysis of 48 papillomavirus types and 28 subtypes and variants: a showcase for the molecular evolution of DNA viruses

Papillomaviruses are attractive models for studying the molecular evolution of DNA viruses because of the large number of isolates that exhibit genomic diversity and host species and tissue specificity. To examine their relationship, we selected two amino acid sequences, one of 52 residues within the early gene E1 and the other of 44 residues within the late gene L1, which allowed insertion- and deletion-free alignment of all accessible papillomavirus sequences. We constructed phylogenetic trees from the amino acid and corresponding nucleotide sequences from 28 published and 20 newly determined animal and human papillomavirus (HPV) genomic sequences by using distance matrix, maximum-likelihood, and parsimony methods. The trees agreed in all important topological aspects. One major branch with two clearly separated clusters contained 11 HPV types associated with epidermodysplasia verruciformis. A second major branch had all the papillomaviruses involved in genital neoplasia and, in distant relationship, the cutaneous papillomaviruses HPV type 2a (HPV-2a), HPV-3, and HPV-10 as well as the "butcher's" papillomavirus HPV-7 and two simian papillomaviruses. Four artiodactyl (even-toed hoofed mammal) papillomaviruses, the cottontail rabbit papillomavirus, and avian (chaffinch) papillomavirus type 1 formed a third major branch. Last, four papillomaviruses exhibited little affinity to any of these three branches; these were the cutaneous types HPV-1a, HPV-4, and HPV-41 and B-group bovine papillomavirus type 4. The phylogeny suggests that some branches of papillomavirus evolution are restricted to particular target tissues and that a general process of long-term papillomavirus-host coevolution has occurred. This latter hypothesis is still conjectural because of bias in the current data base for human types and the paucity of animal papillomavirus sequences. The comparison of evolutionary distances for the most closely related types with those of 28 subtypes and variants of HPV-2, HPV-5, HPV-6, HPV-16, and HPV-18 supports the type as a natural taxonomic unit, with subtypes and variants being expressions of minor intratype genomic diversity similar to that found in the natural populations of all biological species. An exception to this seems to be HPV-2c, which has an evolutionary distance from HPV-2a of the intertype magnitude and may eventually have to be regarded as a distinct type. We describe an experimental approach that estimates the taxonomic and phylogenetic positions of newly identified papillomaviruses without viral isolation and complete genomic sequencing.(ABSTRACT TRUNCATED AT 400 WORDS)

Restriction endonuclease patterns of adenovirus type 12 and 18

Restriction endonuclease analysis using 10 restriction enzymes was performed on six and three wild isolates of adenovirus (Ad) type 12 and 18, respectively. Among the Ad12 strains, five DNA variants could be identified. The degree of pairwise comigration of restriction fragments suggests a high degree of genomic diversity within Ad12. The wild isolates of Ad18, on the other hand, displayed a low degree of genetic variability and comprised one DNA variant closely related to the prototype strain. The BglII, BstEII, and HindIII restriction endonuclease patterns of Ad18 were inconsistent with those originally presented. Identical RE-patterns among Ad18 prototype strains (DC) obtained from four different sources, including directly from the American Type Culture Collection, verify that the genuine Ad18 prototype was used in the present study. Using the revised restriction patterns of BglII, BstEII, and HindIII, a proper identification of Ad18 will be facilitated.

Requirement for the adenovirus type 9 E4 region in production of mammary tumors

Oncogenic viruses demonstrating a strict tropism for the mammary gland provide special opportunities to study the susceptibility of this tissue to neoplasia. In rats, human adenovirus type 9 (Ad9) elicits mammary fibroadenomas that are similar to common breast tumors in women, as well as phyllodes-like tumors and mammary sarcomas. By constructing recombinant adenoviruses between Ad9 and Ad26 (a related nontumorigenic virus), it was shown that the Ad9 E4 region was absolutely required to produce these mammary tumors. This indicates that an adenovirus gene located outside the classic transforming region (E1) can significantly influence the in vivo oncogenicity of an adenovirus. Consistent with a direct role in mammary gland oncogenesis, the Ad9 E4 region also exhibited transforming properties in vitro. Therefore, the Ad9 E4 region is a viral oncogene specifically involved in mammary gland tumorigenesis.

Conserved sequences of the adenovirus genome for detection of all human adenovirus types by hybridization

The application of DNA hybridization directly to clinical specimens has the potential of improving the diagnosis of fastidious types of adenovirus. In this study, the genome of one adenovirus type from each human subgenus (A to F) was systematically evaluated by hybridization for homologous sequences to find the optimal common probe for detection of all human adenovirus types. The area of cross-hybridization, most closely defined with adenovirus type 2 (Ad2), mapped from map units 11.4 to 16.1 and 26.9 to 29.7 and, principally, to a central area of the genome between map units 47.5 and 65.2. The last area, enclosing the hexon gene, was highly conserved. Cloned probes generated from this area demonstrated the greatest homology to heterologous types by hybridization analysis. A HindIII-BglII clone containing the hexon gene of Ad2 within narrow confines reacted most evenly with all adenoviral types and detected the DNA of all other subgenera with a sensitivity 2 logs greater than that of a complete genomic Ad2 probe. The most homologous adenoviral gene sequences were observed in genes involved with DNA replication or intimately connected to the hexon in the early capsid formation. These results show that the hexon gene constitutes the best single region of the adenovirus genome for use as a genus-specific probe for the diagnosis of all human adenoviral subgenera by DNA hybridization.

Sequence variation of functional HTLV-II tax alleles among isolates from an endemic population: lack of evidence for oncogenic determinant in tax

Human T-cell leukemia-lymphoma virus type II (HTLV-II) has been isolated from patients with hairy cell leukemia (HCL). We previously described a population with longstanding endemic HTLV-II infection, and showed that there is no increased risk for HCL in the affected groups. We thus have direct evidence that the endemic form(s) of HTLV-II cause HCL infrequently, if at all. By comparison, there is reason to suspect that the viruses isolated from patients with HCL had an etiologic role in the disease in those patients. One way to reconcile these conflicting observations is to consider that isolates of HTLV-II might differ in oncogenic potential. To determine whether the structure of the putative oncogenic determinant of HTLV-II, tax2, might differ in the new isolates compared to the tax of the prototype HCL isolate, MO, four new functional tax cDNAs were cloned from new isolates. Sequence analysis showed only minor (0.9-2.0%) amino acid variation compared to the published sequence of MO tax2. Some codons were consistently different from published sequences of the MO virus, but in most cases, such variations were also found in each of two tax2 clones we isolated from the MO T-cell line. These variations rendered the new clones more similar to the tax1 of the pathogenic virus HTLV-I. Thus we find no evidence that pathologic determinants of HTLV-II can be assigned to the tax gene.

The sequence of the genome of adenovirus type 5 and its comparison with the genome of adenovirus type 2

We report the sequence of 7558 nucleotides of the adenovirus type 5 genome. With this sequence and previously published data, the complete sequence of this genome is now available and can be compared with the already known sequence of the adenovirus type 2 genome. These two serotypes belong to the same subgroup and sequence comparison shows 94.7% homology between the two genomes. The differences are not at all randomly distributed. Transitions between C and T and between A and G account in total for 58.3% of the differences and even for 68.6% for the genome devoid of the fiber and the hexon genes (instead of 33% expected for an equal probability of changes). In the fiber gene the transitions account for 47% of the differences. The detailed analysis of the nucleotide substitution between the two genomes suggests that the Ad2 genome could derive from that of Ad5 one, with the exception of the fiber gene which is likely to be present in Ad2 genome as a result of genetic recombination. The homology between the amino acids sequences of the structural proteins varies from 100% (proteins pVII and IX) to only 69.2% for the fiber.

Comparative study of adenoviruses with monoclonal antibodies

The obtainment of monoclonal antibodies for adenovirus species 4(Ad4) is described. The specificities of selected monoclonal antibodies were determined by means of viral neutralization test in cell culture, immunofluorescence and Enzyme-Linked Immunosorbent Assay (ELISA), in the presence of the following species of human adenovirus: 1, 2, 5 (subgenus C), 4 (subgenus E), 7 and 16 (subgenus B) and 9 (subgenus D). Two monoclonal antibodies species specific to adenovirus 4 (1CIII and 3DIII) and one monoclonal antibody that cross reacted with adenovirus species 4 and 7 (2HIII) were obtained.

Restriction site mapping of subgenus D adenoviruses, prototypes 42-47, intermediate and atypical strains

Restriction site maps with the endonucleases BamHI, BgIII, and HindIII were elaborated for 19 adenovirus strains of subgenus D, namely candidates AV42 to 47, 6 intermediate and 7 atypical strains. On the basis of several types mapped by biochemical methods, the physical maps for the 19 strains were constructed by adapting restriction fragments of defined molecular weight to the known maps, as the homology among strains within this subgenus is considerable. Other prototypes mapped by adaptation were also used for reference. The localization of the restriction sites on the genome was analyzed for all mapped types or strains of subgenus D (except AV8). The sites appeared to be randomly distributed; only one site was common to all strains.

Anti-adenovirus type 5 cytotoxic T lymphocytes: immunodominant epitopes are encoded by the E1A gene

Virus specific, major histocompatibility complex-restricted, cytotoxic T lymphocytes (CTL) generated in Fischer strain rats infected with human adenovirus type 5 (Ad5) were found to recognize antigenic determinants encoded within the Ad5 early region 1A (E1A) gene. Preliminary mapping studies suggest that the E1A CTL epitopes are encoded within the regions between bp 625 to 810 and 916 to 974 in the first exon of this gene. These epitope-coding regions occur within subregions of E1A that are conserved functionally, and to some extent structurally (approximately 50% sequence homology), among adenoviruses of different groups. Nevertheless, Ad5-specific CTL lysed only targets infected with adenoviruses of the same group (group C; e.g., Ad2) and not targets infected with adenoviruses of different groups (groups A, B, and E). These results suggest that virus-specific CTL may limit adenoviral dissemination by destroying virus-infected cells at an early stage in the viral replicative cycle, during E1A gene expression. Expression of other adenovirus genes does not appear to be required to target infected cells for elimination by CTL.

Restriction site mapping of four genome types of adenovirus types 3 and 7 isolated in South America

New genome types of Ad3 and Ad7 were found among adenovirus (Ad) strains isolated from stools of children during epidemiological surveys made in São Paulo, Brazil, and Buenos Aires, Argentina. These were characterized by DNA analysis with 11 restriction endonucleases and showed a number of new restriction patterns, notably for BamHI, BcII, BgIII, HindIII, KpnI, and SmaI. Restriction maps of the genome types, named Ad3e1, Ad3e2, Ad3h, and Ad7h, were constructed and compared with those of Ad3p and Ad7p.

Fiber sequence heterogeneity in subgroup F adenoviruses

The fiber gene of adenovirus type 41 was sequenced and compared to the fiber gene sequence of adenovirus type 40 (A. H. Kidd and M. J. Erasmus, 1989, Virology 172, 134-144), the other known member of subgroup F. The open reading frame, from map units 87 through 92 with transcription from the r-strand, comprised 1686 bases and was 45 bases longer than its counterpart on the Ad40 genome. The 45-base difference appears to have resulted from a block deletion on the Ad40 sequence. Apart from this one region, the Ad40 and Ad41 fiber genes showed remarkably high homology (95.6%), indicating a relatively recent evolutionary divergence. The deduced amino acid sequence of the Ad41 fiber polypeptide was analyzed according to the model of N. M. Green et al. (1983, EMBO J. 2, 1357-1365) for the structure of the adenovirus fiber. Ad41 had one more 15-residue repeat in the shaft region than Ad40, there being 22 repeat motifs. A detailed study of various Ad40 and Ad41 strains with proven genome differences indicated that the 15-amino acid difference in polypeptide length at the 14th repeat motif is a type-specific difference among the subgroup F adenoviruses. However, two uncommon Ad41 strains belonging to 2 of the 16 Ad41 genome types tested had a 15-amino acid block deletion which was different to that of the Ad40 polypeptide. The implication from this work is that the Ad40 fiber gene probably arose from its Ad41 counterpart, but the fiber gene sequences of both types of subgroup F adenovirus are so similar that genetic recombination between strains could occur with some frequency.

Enteric adenoviruses

Human adenoviruses are classified into 47 serotypes and six subgenera (A-F) with different tropisms. In recent years adenovirus type 40 (Ad40) and 41 (Ad41) of subgenus F have been shown to be causative agents in enteric infections, which is second in importance only to rotaviruses as a cause of infantile gastroenteritis. Infection with EAds occurs worldwide and has been associated with 4-17% of cases of diarrhoea in children. AD40 and Ad41 primarily affect young children less than 2 years of age and occur throughout the year. The clinical characteristics include watery diarrhoea accompanied by vomiting, low grade fever and mild dehydration. A distinct feature of EAds infection is the protracted diarrhoea (mean 8.6 and 12.2 days for Ad40 and Ad41, respectively). Respiratory symptoms are infrequent. Serotypes Ad40 and Ad41 differ from all other (established) adenoviruses by being unable to replicate in conventional cell cultures. These fastidious viruses only grow in selected cell lines, 293 cells being the most commonly used. In spite of the difficulty of isolating Ad40 and Ad41, they can be directly identified and typed by ELISA and solid-phase immune electron microscopy. The amount of viral DNA in stool specimens is sufficient for identification by DNA restriction and dot-blot assays. The recent development of highly sensitive and specific monoclonal antibody-based ELISAs enable accurate diagnosis of adenovirus gastroenteritis in routine work and make possible the evaluation of the role of the enteric adenoviruses in diarrhoeal disease in the developing countries.

A protein serologically and functionally related to the group C E3 14,700-kilodalton protein is found in multiple adenovirus serotypes

A 14.7-kilodalton protein (14.7K protein) encoded by the E3 region of group C adenoviruses has been shown to protect virus-infected fibroblasts from lysis by tumor necrosis factor (TNF) (L.R. Gooding, L.W. Elmore, A.E. Tollefson, H.A. Brady, and W.S.M. Wold, Cell 53:341-346, 1988). In this study we show that adenoviruses of other groups are also protected from TNF-induced cytolysis. Representative serotypes of groups A, B, D, and E produce a protein analogous to the 14.7K protein found in human group C adenoviruses. Deletion of this protein in group C viruses permits virus infection to induce cellular susceptibility to TNF killing. As with group C adenoviruses, cells infected with wild-type adenoviruses of other serotypes are not killed by TNF and are protected from lysis induced by TNF plus cycloheximide. However, cells are susceptible to TNF-induced lysis when infected with adenovirus type 4 mutants from which the 14.7K gene has been deleted. Although all known adenovirus serotypes infect epithelial cells, adenoviruses cause several diseases with various degrees of pathogenesis. Our findings suggest that the 14.7K protein provides a function required for the in vivo cytotoxicity of many adenoviruses independent of the site of infection or degree of pathogenesis.

Serological and genetical relationships of three herpesvirus strains from salmonid fish

Serological and genetical relationships of three salmonid herpesviruses [strain H-83, OO-7812 strain of Oncorhynchus masou virus (OMV) and Herpesvirus salmonis] were investigated. Although the serological relationships of these viruses were not distinctly demonstrated by cross-neutralization test, cross enzyme-linked immunosorbent assay revealed that strain H-83 and OMV appeared to be serologically more closely related to each other than to H. salmonis. Strain H-83 was genetically similar to OMV but distinct from H. salmonis by restriction endonuclease cleavage analysis and DNA-DNA hybridization test. These results indicated that strain H-83 should be classified under the same group as OMV, and H. salmonis belong to another group of salmonid herpesviruses.

Genome type analysis of adenoviruses: isolates from one year from the Hannover area

Adenoviruses (AV), isolated from 138 children during the year 1981 in the Hannover area, were studied by DNA restriction analysis with the enzymes BamHI, BglII, BstEII, EcoRI, HindIII, KpnI, and SmaI and compared with the respective prototypes. Varying fragment patterns were depicted and genome types analyzed. Prototype-like strains of AV1 and 5 were not found. Types 2, 5, 1, 3, and 7 showed decreasing genetic variation in that order. Altered restriction sites were physically mapped on the genome; they appeared to be randomly distributed. The high genetic variability of AV2 and 5 is remarkable for this study population, limited in time and space. Clinical and epidemiological data were also presented in relation to serotypes.

Adenovirus proteins and MHC expression

Adenoviruses are able to specifically down-regulate the cell surface expression of MHC class I antigens. Most viral serotypes achieve these ends by synthesizing a protein that binds to class I antigens in the endoplasmic reticulum (ER) and impedes the transport of these molecules to the cell surface. However, viruses belonging to the highly oncogenic subgenus A do not affect the class I antigen expression during acute infection. Instead, they are distinct from other adenoviruses in that they specifically down-regulate the level of mRNAs, encoding MHC class I antigens, in virally transformed cells. The virus-induced reduction of class I antigen expression drastically diminishes the ability of CTLs to recognize cells infected or transformed by adenovirus. A number of issues concerning these viral mechanisms for class I antigen modulation need to be addressed. The molecular mechanism by which the E1A gene product of subgenus A viruses diminishes class I mRNA levels has not been elucidated. Also, the details of the interaction between the E19 protein and class I molecules should be studied, preferably by X-ray crystallography of the complexes. This would clarify the role of the antigen-binding site as well as other portions of the class I molecule in the binding to the E19 protein. Of general importance for our understanding of the sorting and intracellular transport of proteins is the exact delimitation of the signal for ER localization, which is present in the COOH-terminus of the E19 protein. The putative interaction of this peptide sequence with components of the ER membrane should also be studied. Finally, the study of the pathophysiological role of the MHC class I down-regulation will undoubtedly yield new insights into how the immune system combats virally infected and transformed cells.

Human viral gastroenteritis

During the last 15 years, several different groups of fastidious viruses that are responsible for a large proportion of acute viral gastroenteritis cases have been discovered by the electron microscopic examination of stool specimens. This disease is one of the most prevalent and serious clinical syndromes seen around the world, especially in children. Rotaviruses, in the family Reoviridae, and fastidious fecal adenoviruses account for much of the viral gastroenteritis in infants and young children, whereas the small caliciviruses and unclassified astroviruses, and possibly enteric coronaviruses, are responsible for significantly fewer cases overall. In addition to electron microscopy, enzyme immunoassays and other rapid antigen detection systems have been developed to detect rotaviruses and fastidious fecal adenoviruses in the stool specimens of both nonhospitalized patients and those hospitalized for dehydration and electrolyte imbalance. Experimental rotavirus vaccines have also been developed, due to the prevalence and seriousness of rotavirus infection. The small, unclassified Norwalk virus and morphologically similar viruses are responsible for large and small outbreaks of acute gastroenteritis in older children, adolescents, and adults. Hospitalization of older patients infected with these viruses is usually not required, and their laboratory diagnoses have been limited primarily to research laboratories.

Nucleic acid analysis by sandwich hybridization

One of the most significant achievements of the biochemist during the past two decades is the use to which immunologically based assays have been put in clinical diagnosis (Hood et al.: Immunology, 1984). The problem faced and surmounted by immunologists in effecting the transition from research tool to routine clinical assay bears a remarkable similarity to that confronting the molecular biologist today; i.e., how can nucleic acid hybridization, a technique of obvious potential (Meinkoth and Wahl: Anal Biochem 138:267-284, 1984; Syvanen: Med Biol 64:313-324, 1986; Matthews and Kricka: Anal Biochem 169:1-25, 1988), be modified in order to fulfill all necessary parameters of a routine diagnostic assay? There are several such requirements, and the importance placed on each depends on the objectives of the assay: the technique must be sensitive, specific, and reproducible. Other advantages would be cost-effectiveness, ease of manipulation, and amenability to automation. Ideally, the signal detection should be based on a non-radioactive system, because of the instability of probes labelled with isotopes like 32p, and the potential hazards involved in their handling and disposal. The sandwich hybridization for the analysis of nucleic acid sequences was first used in 1977 (Dunn and Hassell: Cell 12:23-36, 1977), but its potential as a diagnostic assay was not realized until 1983, when it was applied to the detection of adenovirus DNA in nasopharyngeal aspirates from children with acute respiratory infection (Ranki et al: Gene 21:77-85, 1983). It has since been modified and used not only for the detection of microbial infection (Virtanen et al.: Lancet i:381-383, 1983; Ranki et al.: Cur Top Microbiol Immunol 104:307-318, 1983; Lehtomaki et al.: J Clin Microbiol 24:108-111, 1986; Virtanen et al.: J Clin Microbiol 20:1083-1088, 1984; Palva and Ranki: Clin Lab Med 5:475-490, 1985; Polsky-Cynkin et al.: Clin Chem 31:1438-1443, 1985; Parkkinen et al.: J Med Virol 20:279-288, 1986; Palva: FEMS Microbiol Lett 28:85-91, 1985; Palva et al: FEMS Microbiol Lett 23:83-89, 1984; Zolg et al.: Mol Biochem Parasitol 22:145-151, 1987; Palva: J Clin Microbiol 18:92-100, 1983), but also for the analysis of nucleotide sequence variations (Langdale and Malcolm: Gene 36:201-210, 1985). We will discuss the development of the sandwich technique and the advantages it conveys over the more conventional nucleic acid hybridization formats, together with new developments which will ensure that it earns a place alongside immunoassay in the diagnostic laboratory.