Transcription mapping of mouse adenovirus type 1 early region 3

User-Friendly Replication-Competent MAdV-1 Vector System with a Cloning Capacity of 3.3 Kilobases

Mouse adenoviruses (MAdV) play important roles in studying host-adenovirus interaction. However, easy-to-use reverse genetics systems are still lacking for MAdV. An infectious plasmid pKRMAV1 was constructed by ligating genomic DNA of wild-type MAdV-1 with a PCR product containing a plasmid backbone through Gibson assembly. A fragment was excised from pKRMAV1 by restriction digestion and used to generate intermediate plasmid pKMAV1-ER, which contained E3, fiber, E4, and E1 regions of MAdV-1. CMV promoter-controlled GFP expression cassette was inserted downstream of the pIX gene in pKMAV1-ER and then transferred to pKRMAV1 to generate adenoviral plasmid pKMAV1-IXCG. Replacement of transgene could be conveniently carried out between dual BstZ17I sites in pKMAV1-IXCG by restriction-assembly, and a series of adenoviral plasmids were generated. Recombinant viruses were rescued after transfecting linearized adenoviral plasmids to mouse NIH/3T3 cells. MAdV-1 viruses carrying GFP or firefly luciferase genes were characterized in gene transduction, plaque-forming, and replication in vitro or in vivo by observing the expression of reporter genes. The results indicated that replication-competent vectors presented relevant properties of wild-type MAdV-1 very well. By constructing viruses bearing exogenous fragments with increasing size, it was found that MAdV-1 could tolerate an insertion up to 3.3 kb. Collectively, a replication-competent MAdV-1 vector system was established, which simplified procedures for the change of transgene or modification of E1, fiber, E3, or E4 genes.

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

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

Effects of tumor necrosis factor on viral replication and pulmonary inflammation during acute mouse adenovirus type 1 respiratory infection

CD8 T cells contribute to effective clearance of mouse adenovirus type 1 (MAV-1) and to virus-induced pulmonary inflammation. We characterized effects of a CD8 T cell effector, TNF, on MAV-1 pathogenesis. TNF inhibited MAV-1 replication in vitro. TNF deficiency or immunoneutralization had no effect on lung viral loads or viral gene expression in mice infected intranasally with MAV-1. Absence of TNF delayed virus-induced weight loss and reduced histological evidence of pulmonary inflammation, although concentrations of proinflammatory cytokines and chemokines in bronchoalveolar lavage fluid (BALF) were not significantly affected. BALF concentrations of IL-10 were greater in TNF-deficient mice compared to controls. Our data indicate that TNF is not essential for control of viral replication in vivo, but virus-induced TNF contributes to some aspects of immunopathology and disease. Redundant CD8 T cell effectors and other aspects of immune function are sufficient for antiviral and pro-inflammatory responses to acute MAV-1 respiratory infection.

Murine adenoviruses: tools for studying adenovirus pathogenesis in a natural host

Small laboratory animals are powerful models for investigating in vivo viral pathogenesis of a number of viruses. For adenoviruses (AdVs), however, species-specificity poses limitations to studying human adenoviruses (HAdVs) in mice and other small laboratory animals. Thus, this review covers work on naturally occurring mouse AdVs, primarily mouse adenovirus type 1 (MAdV-1), a member of the species Murine mastadenovirus A. Molecular genetics, virus life cycle, cell and tissue tropism, interactions with the host immune response, persistence, and host genetics of susceptibility are described. A brief discussion of MAdV-2 (member of species Murine mastadenovirus B) and MAdV-3 (member of species Murine mastadenovirus C) is included. We report the use of MAdVs in the development of vectors and vaccines.

Fas activity mediates airway inflammation during mouse adenovirus type 1 respiratory infection

CD8 T cells play a key role in clearance of mouse adenovirus type 1 (MAV-1) from the lung and contribute to virus-induced airway inflammation. We tested the hypothesis that interactions between Fas ligand (FasL) and Fas mediate the antiviral and proinflammatory effects of CD8 T cells. FasL and Fas expression were increased in the lungs of C57BL/6 (B6) mice during MAV-1 respiratory infection. Viral replication and weight loss were similar in B6 and Fas-deficient (lpr) mice. Histological evidence of pulmonary inflammation was similar in B6 and lpr mice, but lung mRNA levels and airway proinflammatory cytokine concentrations were lower in MAV-1-infected lpr mice compared to infected B6 mice. Virus-induced apoptosis in lungs was not affected by Fas deficiency. Our results suggest that the proinflammatory effects of CD8 T cells during MAV-1 infection are mediated in part by Fas activation and are distinct from CD8 T cell antiviral functions.

Pathogenicity and complete genome sequence of a fowl adenovirus serotype 8 isolate

In this study we determined and analyzed the complete nucleotide sequence of the genome of a fowl adenovirus serotype 8 (FAdV-8) isolate and examined its pathogenicity in chickens. The full genome of FAdV-8 was 44,055 nucleotides in length with a similar organization to that of FAdV-1 and FAdV-9 genomes. No regions homologous to early regions E1, E3 and E4 of mastadenoviruses were recognized. Along with FAdV-9, FAdV-8 has only one fiber gene and with regard to sequence composition and genome organization, FAdV-8 is closer to FAdV-9 than to FAdV-1. Moreover, our findings suggest that FAdV-1 of species Fowl adenovirus A as the current type species despite its historical priority is not representative of the genus Aviadenovirus, and that FAdV-8 or FAdV-9 in species Fowl adenovirus E and Fowl adenovirus D, respectively, would be more suitable for that designation. Additionally, pathogenicity of FAdV-8 was studied in specific pathogen free chickens following oral and intramuscular inoculations. Despite lack of clinical signs and pathological changes virus was found in tissues and cloacal swabs of all birds with the highest viral copy numbers present in the cecal tonsils. The highest virus titers in the feces for orally and intramuscularly inoculated chickens were recorded at days 10 and 3 post-infection, respectively.

A novel cardiotropic murine adenovirus representing a distinct species of mastadenoviruses

During cell culture isolation experiments to recover Dobrava hantavirus from a suspension of liver from a striped field mouse (Apodemus agrarius), an unknown virus was coisolated. Atypically for hantaviruses, it had extensive cytopathic effects. Using a random PCR approach, it was identified as a novel murine adenovirus, MAdV-3 (for MAdV type 3). A plaque-purified virus clone was prepared and further characterized. The complete genome sequence of MAdV-3 was determined to be 30,570 bp in length. Sequence comparisons to other adenovirus species revealed highest similarity to MAdV-1, the representative of the murine adenovirus A species. However, substantial differences were found in the E1, E3, and E4 genomic regions. The phylogenetic distance of MAdV-3 amino acid sequences for pVIII, protease, polymerase, and hexon from MAdV-1 is markedly higher than 0.1 exchange per position, and, based on our cross-neutralization experiments, MAdV-3 and MAdV-1 can be regarded as different serotypes. Therefore, we propose to classify MAdV-3 as the first isolate of a novel adenovirus species, designated murine adenovirus C (MAdV-C). The novel MAdV-3 virus is not only genetically and serologically distinct from MAdV-1 but also shows a unique organ tropism in infected mice. In contrast to MAdV-1, the virus was not detectable in brain but predominantly infected heart tissue. Thus, infection of mice with cardiotropic MAdV-3 might be an interesting animal model of adenovirus-induced myocarditis.

Acute respiratory infection with mouse adenovirus type 1

Studies of the pathogenesis of adenovirus respiratory disease are limited by the strict species-specificity of the adenoviruses. Following intranasal inoculation of adult C57BL/6 mice with mouse adenovirus type 1 (MAV-1), we detected MAV-1 early region 3 (E3) and hexon gene expression in the lungs at 7 days post-infection (dpi). We detected MAV-1 E3 protein in the respiratory epithelium at 7 dpi. We did not detect viral mRNA or protein at 14 dpi, but MAV-1 DNA was detected by PCR at 21 dpi. Chemokine transcript levels increased between 7 and 14 dpi in the lungs of infected mice. MAV-1 infection induced a patchy cellular infiltrate in lungs at 7 and 14 dpi. This is the first report demonstrating the presence of MAV-1 in the respiratory epithelium of infected mice and describing chemokine responses in the lung induced by MAV-1 respiratory infection. MAV-1 infection of mice has the potential to serve as a model for inflammatory changes seen in human adenovirus respiratory disease.

Requirement of Sur2 for efficient replication of mouse adenovirus type 1

Mouse adenovirus type 1 (MAV-1) early region 1A (E1A) encodes a virulence gene in viral infection of mice. To broaden our understanding of the functions of E1A in MAV-1 pathogenesis, an unbiased experimental approach, glutathione S-transferase (GST) pulldown, was used to screen for cellular proteins that interact with E1A protein. We identified mouse Sur2, a subunit of Mediator complex, as a protein that binds to MAV-1 E1A. The interaction between Sur2 and MAV-1 E1A was confirmed in virus-infected cells. Conserved region 3 (CR3) of MAV-1 E1A was mapped as the region required for Sur2-E1A interaction, as is the case for human adenovirus E1A. Although it has been proposed that human adenovirus E1A recruits the Mediator complex to transactivate transcription of viral early genes, Sur2 function in adenovirus replication has not been directly tested previously. Studies on the functions of Sur2 with mouse embryonic fibroblasts (MEFs) showed that there was a multiplicity-dependent growth defect of MAV-1 in Sur2(-/-) MEFs compared to Sur2(+/+) MEFs. Comparison of the viral DNA and viral mRNA levels in Sur2(+/+) and Sur2(-/-) MEFs confirmed that Sur2 was important for efficient viral replication. The viral replication defects in Sur2(-/-) MEFs appeared to be due at least in part to a defect in viral early gene transcription.

Genetic organization and sequence analysis of pVIII, fiber and early region 4 of bovine adenovirus type 7

The DNA sequence of 8,810 nucleotides at the right end of bovine adenovirus type 7 (BAV7) genome was determined and compared with similar regions of other adenoviruses. This genomic region of BAV7 consists of sequences encoding partial 33K, pVIII, fiber, putative early region 4 (E4) proteins and other unassigned proteins. However, BAV7 E3 region is not present in the expected location between pVIII and fiber as BAV7 intergenic region between pVIII and fiber genes is only 183 nucleotides. The predicted pVIII and fiber demonstrates highest homology to corresponding proteins of ovine adenovirus 287 (OAV287), bovine adenovirus-4 (BAV4) and egg drop syndrome virus (EDSV). The E4 region encodes three ORFs, which shows significant homology only to corresponding proteins encoded by E4 region of OAV287 and BAV4. Sequence comparisons, phylogenetic analysis and overall genome organization in this region of BAV7 provide further evidence for the inclusion of BAV7 together with OAV287, BAV4, and EDSV in the proposed genus 'Atadenovirus'.

In vitro and in vivo characterization of a mouse adenovirus type 1 early region 3 null mutant

Previous attempts to construct a mouse adenovirus type 1 early region 3 (E3) null mutant by initiator codon mutagenesis were unsuccessful because one of the E3 proteins, gp11K, is synthesized as a fusion protein from a late viral mRNA (A. N. Cauthen and K. R. Spindler, Virology 259:119-128, 1999). Therefore, a different mutagenesis strategy was employed that inserted termination codons into all three reading frames of the E3 proteins. This strategy produced a mutant, pmE314, that was null for the expression of E3 proteins as determined by immunoprecipitation with E3-specific antisera. This mutant grew as well as wild-type (wt) virus in both 3T6 mouse fibroblasts and mouse brain microvascular endothelial cells. However, the 50% lethal dose for pmE314 in adult NIH Swiss outbred mice was approximately 6 log units higher than that of wt virus, indicating that pmE314 was less virulent in mice. In situ hybridization experiments revealed that the absence of the E3 proteins did not alter the tropism of the mutant virus from that of wt virus. When the histopathology was evaluated, the characteristics of the pmE314 infection at both doses administered were strikingly different from those exhibited by wt virus. The central nervous system of wt-infected mice exhibited damage to the endothelium and recruitment of inflammatory cells, whereas the central nervous system of pmE314-infected mice showed no inflammatory response and only mild signs of endothelial damage.

Novel expression of mouse adenovirus type 1 early region 3 gp11K at late times after infection

Mutations were introduced into mouse adenovirus type 1 (MAV-1) early region 3 (E3) initiator codons by homologous recombination between viral DNA and a plasmid containing a mutagenized E3 region. The resulting mutant virus, pmE312, contained ATG --> TTA mutations at codon positions 1 and 4 and was expected to be null for the expression of the E3 proteins. However, gp11K, an MAV-1 E3 glycoprotein of 14K molecular weight, was detected in mutant-infected cell lysates at levels about 10-12% of that of wild-type (wt) virus at late times in infection. The gp11K polypeptide produced by pmE312 at late times was immunoprecipitated with two E3-specific antisera prepared against different regions of the protein. Like gp11K produced by wt virus infections, it was sensitive to endoglycosidase H (endo H) and thus resident in the endoplasmic reticulum (ER). In pmE312-infected cells treated with cytosine arabinoside (araC), an inhibitor of DNA replication, the gp11K protein was not detected by immunoprecipitation. This indicates that gp11K expression in pmE312-infected cells at late times was dependent on DNA replication and that it was thus translated from a late transcript. In vitro translation of poly(A)+ RNA from mock-, wild-type-, and pmE312-infected cells showed that gp11K was translated from late mRNA as an approximately 28K fusion between a late protein and gp11K. Our data are consistent with a model in which gp11K is expressed at late times as a late protein-gp11K chimera in both wt- and mutant-infected cells. This chimera is then processed: removal of a large N-terminal sequence results in the observed 14K ER-localized gp11K.

Transcription mapping and characterization of 284R and 121R proteins produced from early region 3 of bovine adenovirus type 3

We established the transcription map of early region (E) 3 of bovine adenovirus 3 (BAV-3) by Northern blot, S1 nuclease protection assays, cDNA sequencing, and RT-PCR analysis. Five major classes of mRNAs were identified, which shared the 3' ends. Four classes of mRNAs transcribed from the E3 promoter also shared the 5' end, while one major class of mRNA transcribed from the major late promoter contained a tripartite leader sequence at the 5' end. These five transcripts have the potential to encode four proteins, namely 284R, 121R, 86R, and 82R. To identify the proteins, rabbit antiserum was prepared using a bacterial fusion protein encoding 284R or 121R protein. Serum against 284R immunoprecipitated protein of 26-32 kDa in in vitro translated and transcribed mRNA and three proteins of 48, 67, and 125 kDa from BAV-3-infected cells. Western blots and enzymatic digestions confirmed that the 284R protein is a glycoprotein, which contains only N-linked oligosaccharides, both high mannose (48 kDa) and complex types (67 kDa). Serum against 121R immunoprecipitated a protein of 14.5 kDa from in vitro translated and transcribed mRNA and BAV-3-infected cells. Although 121R protein shows limited sequence similarity to a 14.7-kDa protein of human adenovirus 5, the 284R protein appears to be unique to BAV-3. Since proteins encoded by the E3 region appear to influence adenovirus pathogenesis, the 284R protein may contribute to the unique pathogenic properties of BAV-3.

The complete DNA sequence and genome organization of the avian adenovirus, hemorrhagic enteritis virus

Hemorrhagic enteritis virus (HEV) belongs to the Adenoviridae family, a subgroup of adenoviruses (Ads) that infect avian species. In this article, the complete DNA sequence and the genome organization of the virus are described. The full-length of the genome was found to be 26,263 bp, shorter than the DNA of any other Ad described so far. The G + C content of the genome is 34.93%. There are short terminal repeats (39 bp), as described for other Ads. Genes were identified by comparison of the DNA and predicted amino acid sequences with published sequences of other Ads. The organization of the genome in respect to late genes (52K, IIIa, penton base, core protein, hexon, endopeptidase, 100K, pVIII, and fiber), early region 2 genes (polymerase, terminal protein, and DNA binding protein), and intermediate gene IVa2 was found to be similar to that of other human and avian Ad genomes. No sequences similar to E1 and E4 regions were found. Very low similarity to ovine E3 region was found. Open reading frames were identified with no similarity to any published Ad sequence.

Mouse adenovirus type 1 early region 1A is dispensable for growth in cultured fibroblasts

Mouse adenovirus type 1 (MAV-1) mutants with deletions of conserved regions of early region 1A (E1A) or with point mutations that eliminate translation of E1A were used to determine the role of E1A in MAV-1 replication. MAV-1 E1A mutants expressing no E1A protein grew to titers comparable to wild-type MAV-1 titers on mouse fibroblasts (3T6 fibroblasts and fibroblasts derived from Rb+/+, Rb+/-, and Rb-/- transgenic embryos). To test the hypothesis that E1A could induce a quiescent cell to reenter the cell cycle, fibroblasts were serum starved to stop DNA replication and cellular replication and then infected with the E1A mutant and wild-type viruses. All grew to equivalent titers. Steady-state levels of MAV-1 early mRNAs (E1A, E1B, E2, E3, and E4) from 3T6 cells infected with wild-type or E1A mutant virus were examined by Northern analysis. Steady-state levels of mRNAs from the mutant-infected cells were comparable to or greater than the levels found in wild-type virus infections for most of the early regions and for two late genes. The E2 mRNA levels were slightly reduced in all mutant infections relative to wild-type infections. E1A mRNA was not detected from infections with the MAV-1 E1A null mutant, pmE109, or from infections with similar MAV-1 E1A null mutants, pmE112 and pmE113. The implications for the lack of a requirement of E1A in cell culture are discussed.

Distribution of mouse adenovirus type 1 in intraperitoneally and intranasally infected adult outbred mice

In situ nucleic acid hybridization and immunohistochemistry were used to determine the histological localization of mouse adenovirus type 1 (MAV-1) during acute infection of adult mice infected either intraperitoneally or intranasally with 1,000 PFU of wild-type virus. Organ samples were collected from days 1 to 17 postinfection for the intraperitoneally infected mice and from days 1 to 13 for the intranasally infected mice. Endothelial cells of the brain and spinal cord showed extensive evidence of MAV-1 infection. Endothelial cells in lungs, kidneys, and other organs were also positive for MAV-1, indicating a widespread involvement of the systemic circulation. The presence of viral nucleic acid and/or antigen was also demonstrated in lymphoid tissue. The spleens, Peyer's patches, and peripheral lymph nodes showed positive staining at various times postinfection in mice infected by either route. Virus-infected cells in the spleen exhibited a stellate shape and were localized to the red pulp and germinal centers, suggesting that they are cells of the mononuclear phagocytic system.

Completion of the DNA sequence of mouse adenovirus type 1: sequence of E2B, L1, and L2 (18-51 map units)

The DNA sequence of 9991 nt, corresponding to 18-51 map units of mouse adenovirus type 1 (MAV-1), was determined, completing the sequence of the Larsen strain of MAV-1. The length of the complete MAV-1 genome is 30,946 nucleotides, consistent with previous experimental estimates. The 18-51 map unit region encodes early region 2B proteins necessary for adenoviral replication as well as late region L1 and L2 structural and packaging proteins. Sequence comparison in this region with human adenoviruses indicates broad similarities, including colinear preservation of all recognized open reading frames (ORFs), with highest amino acid identity occurring in the DNA polymerase and polypeptide III (penton base subunit) ORFs. Virus-associated (VA) RNA is not encoded in the region where VA RNAs are found in the human adenoviruses, between E2B and L1, nor is it encoded anywhere in the entire MAV-1 genome. The MAV-1 polypeptide III lacks the arginine-glycine-aspartic acid (RGD) motif which is involved in an association with cell-surface integrins. Only one RGD sequence is found in an identified coding region in the entire MAV-1 genome. Similar to the porcine adenovirus, this RGD sequence is found in the C-terminus of the MAV-1 fiber protein.

Functional characterization of the major late promoter of mouse adenovirus type 1

During the late phase of adenovirus infection, the major late promoter (MLP) controls the regulated expression of the genes that encode most viral structural proteins. Recently, the region of the genome of mouse adenovirus type 1 (MAV-1), predicted to contain the MLP, was sequenced and compared to that of the human virus MLP. The general organization of the transcriptional elements of the putative MAV-1 MLP is similar to that of the human virus counterpart, with some interesting differences. We wished to investigate the function of the predicted MLP of MAV-1 and to determine the significance of the differences found in the MAV-1 MLP. To test the activity of the predicted MLP of MAV-1, both Northern blot and primer extension analyses were performed on intracellular RNA isolated from cells infected with MAV-1. The results show that late RNA can be detected 48 hr postinfection and increases up to 6 days p.i. Primer extension analysis revealed that the major start sites of transcription are 28 and 31 nt downstream of the first T residue of the predicted TATA box. To analyze the functional significance of the predicted transcriptional elements, a transient transfection system, using the firefly luciferase gene controlled by the MAV-1 MLP sequence, was established. The predicted MLP sequence was capable of directing luciferase gene expression, to a level some 60% of that of the human virus MLP. Mutations were created in the inverted CAAT box, the SP1 site, and the TATA box, either singly or in combination. Each single-element mutation causes a marked reduction in luciferase gene expression, with the SP1 mutation showing the greatest effect. Double mutations were even more deficient, suggesting a level of functional redundancy among the various transcriptional elements. Finally, the putative SP1-binding site was examined by gel mobility shift assay and shown to interact with purified SP1 protein specifically, supporting the functional significance of this transcriptional element. These findings contribute to a better understanding of gene expression in MAV-1 and to its development as an appropriate model for the study of the molecular basis of pathogenesis in a natural host animal.

Analysis of early region 3 mutants of mouse adenovirus type 1

Early region 3 (E3) of mouse adenovirus type 1 has the potential to produce three proteins which have identical amino termini but unique carboxy-terminal sequences. Three recombinant deletion viruses were constructed so that each could produce only one of the three E3 proteins. A fourth mutant that should produce no E3 proteins was also constructed. These recombinants were able to grow in mouse 3T6 cells and produced wild-type levels of viral mRNAs and proteins except for those specifically deleted by the mutations. Early mRNA production from the mutant viruses was analyzed by reverse transcriptase PCR and confirmed that each deletion mutant would be able to produce only one of the three E3 proteins. Late mRNA production was analyzed by Northern (RNA) blotting and found to be similar in wild-type and mutant viruses. Capsid morphology was unaltered in the mutant viruses as seen by electron microscopy. Immunoprecipitation of E3 proteins from infections of mouse 3T6 cells using an antiserum specific for all three E3 proteins was used to examine the effect of the introduced mutations on protein expression. Two mutants produced only one class of E3 protein as predicted from their specific mutations and mRNA expression profiles. One mutant virus failed to produce any detectable E3 proteins. The predicted E3-null mutant was found to be leaky and could produce low levels of E3 proteins. Outbred Swiss mice were infected with the E3 mutant viruses to determine if the E3 proteins have an effect on the pathogenicity of the virus in mice. All of the mutants showed decreased pathogenicity as determined by increased 50% lethal doses, indicating that the proteins of the E3 region are important determinants of the pathogenesis of mouse adenovirus in its natural host.

Lack of effect of mouse adenovirus type 1 infection on cell surface expression of major histocompatibility complex class I antigens

It has been proposed that adenoviruses establish and maintain persistent infections by reducing the class I major histocompatibility complex-associated presentation of viral antigens to cytotoxic T lymphocytes, leading to ineffective cell-mediated immunity and impaired clearance of infected cells (W.S.M. Wold and L. R. Gooding, Virology 184:1-8, 1991). Early region 3 of human adenovirus types 2 and 5 encodes a 19-kDa glycoprotein that associates with the class I major histocompatibility complex (MHC) antigens in the endoplasmic reticulum and prevents their maturation and transport to the cell surface. Early region 1A of human adenovirus type 12 encodes a protein that inhibits class I MHC mRNA production at the transcriptional or posttranscriptional processing level. Unlike human adenovirus infections, however, mouse adenovirus type 1 (MAV-1) infection of a variety of cell types did not affect the surface expression of 10 different mouse class I MHC allotypes. MAV-1-infected cells also regenerated cell surface class I MHC antigens following proteolytic removal as efficiently as mock-infected cells. The ability of cells to present antigen to class I MHC (Kb)-ovalbumin-specific T-cell hybridoma cells was likewise unaltered by MAV-1 infection. Thus, the ability of MAV-1 to persist cannot be explained by the model of reduced class I MHC-associated antigen presentation proposed for human adenoviruses.

Porcine adenoviruses types 1, 2 and 3 have short and simple early E-3 regions

The nucleotide sequence of the E-3 region genes, the hexon associated protein pVIII genes, and part of the fiber genes coding for the N-terminal tail regions, of porcine adenovirus (PAV) types 1 and 2 were determined. The sizes of the E-3 regions were found to be 1162 and 1222 bp, respectively. The five open reading frames (ORF) encoded within the sequenced regions of PAV types 1 and 2 shared a high degree of homology with the published sequences of the corresponding ORFs of PAV-3. The E-3 regions of PAV types 1, 2 and 3 were further characterized by Northern blot analysis and 5' and 3' end mapping of the transcripts by S1 nuclease analysis. The results of these experiments indicated that the E-3 regions in these three viruses are shorter and simpler in organization than the E-3 regions of human adenoviruses. A potential promoter for the E-3 regions of these PAVs was identified.

Susceptibility and signs associated with mouse adenovirus type 1 infection of adult outbred Swiss mice

Adult Swiss outbred mice from two sources had a nearly 6,000-fold difference in susceptibility to mouse adenovirus type 1-induced disease. This difference was not attributable to differential organ tropism. Signs associated with mouse adenovirus type 1 infection that have not been previously reported are described at the clinical, gross pathological, and histological levels.

Mouse adenovirus type 1 causes a fatal hemorrhagic encephalomyelitis in adult C57BL/6 but not BALB/c mice

Mouse adenovirus type 1 (MAV-1) produces a lethal disease in newborn or suckling mice characterized by infectious virus and viral lesions in multiple organs. Previous reports of MAV-1 infection of adult mice generally described serologic evidence of infection without morbidity or mortality. However, our current results demonstrate that MAV-1 causes a fatal illness in adult C57BL/6(B6) mice (50% lethal dose, [LD50], 10(3.0) PFU) but not in adult BALB/c mice at all of the doses tested (LD50, > or = 10(5.0) PFU). Adult (BALB/c x B6)F1 mice were intermediately susceptible (LD50, 10(4.5) PFU). Clinically, the sensitive B6 mice showed symptoms of acute central nervous system (CNS) disease, including tremors, seizures, ataxia, and paralysis. Light microscopic examination of CNS tissue from the B6 animals revealed petechial hemorrhages, edema, neovascularization, and mild inflammation in the brain and spinal cord. Analysis by electron microscopy showed evidence of inflammation, such as activated microglia, as well as swollen astrocytic endfeet and perivascular lipid deposition indicative of blood-brain barrier dysfunction. Outside of the CNS, the only significant pathological findings were foci of cytolysis in the splenic white pulp. Assessment of viral replication from multiple tissues was performed by using RNase protection assays with an antisense MAV-1 early region 1a probe. The greatest amounts of viral mRNA in MAV-1-infected B6 animals were located in the brain and spinal cord. Less viral message was detected in the spleen, lungs, and heart. No viral mRNA was detected in BALB/c mouse tissue, with the exception of low levels in the heart. Viral titers of organ tissues were also determined and were concordant with RNase protection findings on the brain and spinal cord but failed to demonstrate significant infectious virus in additional organs. Our experiments demonstrate that MAV-1 has a striking tropism for the CNS that is strain dependent, and this provides an informative in vivo model for the study of adenoviral pathogenesis.

Genetic relationship between mouse adenovirus-2 (strain K87) and human adenovirus-2

The DNA of mouse adenovirus strain K87 (MAd-2) was cloned and mapped with restriction endonucleases BglII, ClaI, EcoRI, HindIII and SphI. Large differences were found between the MAd-2 and MAd-1 (strain FL) DNA molecules in terms of number and location of restriction sites. The MAd-2 genome also appeared as larger in size than the MAd-1 genome (34.72 kb vs. 30.14 kb). Our results confirm the existence of two distinct adenovirus species in the mouse. Hybridization experiments, on the other hand, indicate that both MAd-1 and MAd-2 are genetically related to human adenovirus type 2 (HAd-2). Overlapping regions of DNA homology are located in genes coding for HAd-2 structural components which could explain serological relationships observed between the human and the murine adenoviruses.

Transcription mapping of mouse adenovirus type 1 early region 4

Early region 4 (E4) of mouse adenovirus type 1 was analyzed by Northern blotting, cDNA sequencing, and S1 nuclease protection and primer extension assays. The transcription map of this region was dissimilar to the consensus human adenovirus E4 transcription map in which all transcripts have identical 5' and 3'-terminal sequences. Seven classes of mouse adenovirus type 1 mRNAs were identified; all shared the same 3' end. Three classes of unspliced mRNAs differed at their 5' start sites, two classes of spliced transcripts differed in the locations of their splice acceptors, and two classes of spliced messages differed in their splice donors and acceptors. From the structure of the various transcripts, translational products were predicted. In addition to a predicted polypeptide with similarity to the human adenovirus 2 E4 34K protein previously identified (A. O. Ball, C. W. Beard, P. Villegas, and K. R. Spindler, 1991, Virology 180, 257-265), two open reading frames with similarity to human adenovirus 2 E4 open reading frames 2 and 3 were found.

Differences in the E3 regions of the canine adenovirus type 1 and type 2

Sequence analysis of a region extending between the pVIII and the fiber gene of Canine adenovirus type 1 (Cav-1, Utrecht) and type 2 (Cav-2, Manhattan) was performed. The results revealed a high level of identity between the two viruses when the pVIII gene and the N-terminal part of the fiber gene were compared. The open reading frames of region E3 in of Cav-1 and Cav-2 encoded a 22 kDa and 40.7 kDa polypeptide, respectively. The Cav-1 and Cav-2 E3 region polypeptides shared conserved amino and carboxyl domains. In Cav-2 an extra sequence of about 500 nucleotides was present, appearing like an in frame insertion of foreign DNA. It can be speculated that this insertion in the E3 region contributes to the observed biological differences between Cav-1 and Cav-2.

Primary structure of the murine adenovirus type 1 proteinase

The DNA sequence of an open reading frame (ORF) corresponding to the murine adenovirus type 1 (Mav1) proteinase gene was determined. 1162 base pairs were sequenced from the downstream end of the SmaI-D Mav1 genomic fragment. The sequence defines the 204 amino acid proteinase, which apparently does not possess the usual L3 polyadenylation signal, but instead the sequence AAATAA. This gene is followed by a 147 amino acid C-terminal portion of the DNA-binding protein, encoded by the complementary strand.

Early region 4 sequence and biological comparison of two isolates of mouse adenovirus type 1

The DNA sequence of 88-100 map units of mouse adenovirus type 1 (MAV-1) was determined. One translational open reading frame showed 48% sequence similarity to a human adenovirus type 2 early region 4 protein. Based on the protein similarity, genome location, and transcriptional polarity, we concluded that this region of MAV-1 corresponds to early region 4. A 241-bp sequence consisting of 10 imperfect direct repeats with sequence similarity to minisatellite DNA was found in this region. Two virus isolates with different passage histories were examined and were found to have a sequence polymorphism within this region. The two viruses were compared for growth in cell culture and mice and small quantitative differences were observed only in vivo.