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PubMed2006

Infection with replication-deficient adenovirus induces changes in the dynamic instability of host cell microtubules.

Adenovirus translocation to the nucleus occurs through a well characterized minus end-directed transport along microtubules. Here, we show that the adenovirus infection process has a significant impact on the stability and dynamic behavior of host cell microtubules. Adenovirus-infected cells had elevated levels of acetylated and detyrosinated microtubules compared with uninfected cells. The accumulation of modified microtubules within adenovirus-infected cells required active RhoA. Adenovirus-induced changes in microtubule dynamics were characterized at the centrosome and at the cell periphery in living cells. Adenovirus infection resulted in a transient enhancement of centrosomal microtubule nucleation frequency. At the periphery of adenovirus-infected cells, the dynamic instability of microtubules plus ends shifted toward net growth, compared with the nearly balanced growth and shortening observed in uninfected cells. In infected cells, microtubules spent more time in growth, less time in shortening, and underwent catastrophes less frequently compared with those in uninfected cells. Drug-induced inhibition of Rac1 prevented most of these virus-induced shifts in microtubule dynamic instability. These results demonstrate that adenovirus infection induces a significant stabilizing effect on host cell microtubule dynamics, which involve, but are not limited to, the activation of the RhoGTPases RhoA and Rac1.

ADP Ribose Transferases↗
PubMed1976

Low molecular weight viral RNAs transcribed by RNA polymerase III during adenovirus 2 infection.

Nuclei isolated from human cells productively infected with adenovirus 2 have been shown to synthesize four low molecular weight RNA species which hybridize efficiently to viral DNA. One species corresponds to the 5.5S or VA RNA (Ohe, Weissman, and Cooke, 1969), and is designated V156. The other three species are novel and have been designated V200, V140, V130, since they are approximately 200, 140, and 130 nucleotides in length, respectively. These viral RNAs retain their distinct electrophoretic properties after denaturation with formamide. RNA species with electrophoretic mobilities similar to those of the V200, V156, and V140 RNAs have been found in the cytoplasmic fraction of cells at late times after adenovirus infection. In isolated nuclei, the V200, V156, V140, and V130 RNAs are all synthesized by DNA-dependent RNA polymerase III, since synthesis is sensitive to high but not to low concentrations of alpha-amanitin. The synthesis of these low molecular weight RNAs continues for a prolonged period of time in isolated nuclei, suggesting that reinitiation occurs. Adenovirus 2 DNA fragments obtained by digestion with restriction endonucleases Eco RI and Sma I were used to map the location of the DNA sequences which encode the RNAs. All the low molecular weight RNAs hybridized to a region of the genome between o.18 and 0.38 fractional lengths from the left end of the adenovirus genome, suggesting that the respective DNA sequences are clustered. Other nonviral low molecular weight RNAs are synthesized in nuclei isolated from infected cells. These include the cellular 5S rRNA species which was minitored by its hybridization to purified 5S DNA from Xenopus laevis.

Adenoviridae↗
PubMed2005

Mouse adenovirus type 1 infection in SCID mice: an experimental model for antiviral therapy of systemic adenovirus infections.

The importance of human adenovirus infections in immunocompromised patients urges for new and adequate antiadenovirus compounds. Since human adenoviruses are species specific, animal models for systemic adenovirus infections rely on a nonhuman adenovirus. We established mouse adenovirus type 1 (MAV-1) infection of BALB/c SCID mice as a model for the evaluation of antiadenovirus therapy. In vitro studies with mouse embryonic fibroblasts pointed to the acyclic nucleoside phosphonate cidofovir and the N-7-substituted acyclic derivative 2-amino-7-(1,3-dihydroxy-2-propoxymethyl)purine (S-2242) as markedly active compounds against MAV-1. SCID mice, infected intranasally with MAV-1, developed a fatal disseminated infection after approximately 19 days, characterized by hemorrhagic enteritis. Several techniques were optimized to monitor viral, immunological, and pathological aspects of MAV-1 infection. Real-time PCR quantification of viral DNA revealed that after replication in the lungs, virus disseminated to several organs, including the brain, liver, spleen, intestine, heart, and kidneys (resulting in viruria). Immunohistochemical staining showed that MAV-1 was localized in the endothelial cells of the affected organs. Using reverse transcription-PCR, tissue levels of proinflammatory cytokines (i.e., interleukin-1beta and tumor necrosis factor alpha) were found to be markedly increased. The MAV-1/SCID model appears to be an appropriate model for in vivo evaluation of antiadenovirus agents. Treatment with cidofovir or S-2242 at a dose of 100 mg per kg of body weight resulted in a significant delay in MAV-1-related death, although these antivirals were unable to completely suppress virus replication despite continued drug treatment. These findings suggest that complete virus clearance during antiviral therapy for disseminated adenovirus infection may require an efficient adaptive immune response from the host.

3T3 Cells↗
PubMed1999

Type-specific induction of interleukin-8 by adenovirus.

Infection with adenovirus (Ad) causes acute pneumonia in a type-specific fashion because type 7 but not type 5 Ad has been isolated as a causative agent. We postulated that the type specificity of induction of pneumonia may be related to type-specific cytokine induction in lung cells. To test this hypothesis, we infected human fetal lung fibroblasts and the lung epithelial cell line A549 with live type 5 and type 7 Ad. Virus inactivated by irradiation was used as a control. Type 7 but not type 5 Ad induced interleukin (IL)-8 protein production in both cell types in a dose- and time-dependent manner. Inactivated virus had no effect on the production of IL-8 protein. Type 7 but not type 5 virus also stimulated IL-8-specific messenger RNA (mRNA) production in these cells. Because half-life of IL-8 mRNA was prolonged in both type 5- and type 7-infected A549 cells, induction likely involves enhancement of message stability as well as other effects. Virus early gene expression did not consistently correlate with IL-8 message induction and followed induction in fibroblasts. These results suggest that there is type-specific induction of IL-8 production during infection of lung cells with Ad. Induction involves message stabilization and may not require viral gene expression. Because IL-8 is one of the important mediators of lung inflammation, type-specific induction of this and other cytokines may account for the different consequences of lung infection with different types of Ad.

Adenoviruses, Human↗
PubMed2000

The effect of mutant peptide cofactors on adenovirus protease activity and virus infection.

Adenoviruses encode a cysteine protease, adenain, required for uncoating and virion maturation. Adenain activity is regulated by an 11-amino-acid peptide cofactor thiol-bonded distal to the active site. Structural and experimental data suggest that the peptide might stabilize adenain in an optimal conformation for enzyme activity by bridging two noncontiguous regions of the molecule. The sequence requirements for this mechanism were examined both in vitro and ex vivo by means of mutant peptides and databank analysis. The results of in vitro experiments suggested that activation is not an all or nothing mechanism. With the exception of the smallest peptide, the mutant peptides bound to adenain, activated it, and competed with the wild-type peptide, but all of this occurred with reduced efficiency. When added to the medium of infected cells, most of the peptides inhibited infectious virus production to varying degrees in a dose-dependent manner and in accordance with their in vitro activity on adenain. We interpret this inhibition to be due to unscheduled adenain activation. Examination of the activation peptide sequences from 19 adenovirus serotypes revealed a limited number of conserved sequence features. These features were in agreement with the experimental data. We conclude that binding and activation of adenain by pVIc may be reversible and this reversibility may be an integral aspect of the in vivo regulation of enzyme activity in the course of virus assembly. The peptide cofactor binding domain is therefore a potential target for the development of anti-adenoviral agents.

Adenoviruses, Human↗
PubMed1992

Persistent infection of human adenovirus type 5 in human monocyte cell lines.

Adenovirus infection of human monocyte hybridoma cell lines and the fusion partner U937 was investigated. Adenovirus adsorbed poorly to these cells as well as primary human alveolar macrophages. The virus-binding experiments showed a 100-fold reduction in apparent viral binding to these cells compared to the permissive HeLa cells. Adsorption of adenovirus to these cells could be enhanced by preincubation of adenovirus with its antiserum. Following entry into the cells amplification of adenovirus DNA was detected starting at 2 days postinfection but few mature virus particles were produced. The infected cultures survived the infection and continued to grow for more than a year. In these chronically infected cultures, linear adenovirus DNA persisted up to 200 copies per cell and a small amount of mature virus was produced. Infectious center assay and cell cloning experiments showed that the majority of the cells in the chronically infected cultures harbor adenovirus genome. These results indicate that restriction of replication of human adenovirus type 5 at the late phase results in persistent infection of U937 and the human monocyte hybridoma cell lines.

Adenoviruses, Human↗
PubMed1985

Posttranscriptional control of DHFR gene expression during adenovirus 2 infection.

The effects of productive adenovirus infection on host gene expression were studied by using a line of methotrexate-resistant HeLa cells with amplified dihydrofolate reductase (DHFR) genes. We have previously reported that synthesis of DHFR is induced threefold early in infection and is shut off late in infection (Yoder et al., Mol. Cell. Biol. 3:819-828, 1983). These changes in DHFR protein synthesis are accompanied by changes in both the steady-state cytoplasmic levels of DHFR mRNA and in the rate of appearance of DHFR mRNA in the cytoplasm. In this report, we examined the mechanism of nuclear control of DHFR mRNA levels. Transcription of DHFR-specific sequences continued at a constant rate throughout infection, representing 0.015% of the total transcriptional activity. In contrast, nuclear steady-state levels of DHFR sequences changed in correspondence to the changing rate of appearance of DHFR mRNA in the cytoplasm. That is, nuclear levels of DHFR-specific sequences rose 2.5-fold early in infection and declined to a level below that found in uninfected cells late in infection. Thus, the relative nuclear stability of DHFR sequences changed throughout the course of infection such that during the time of induction, DHFR sequences were preferentially stabilized. This stabilization was transient, however, and was no longer observed by the time of shutoff. These data indicate that posttranscriptional nuclear events are important in the regulation of DHFR gene expression by adenovirus.

Adenoviridae Infections↗
PubMedDate not supplied

Gastrointestinal adenovirus: an important cause of morbidity in patients with necrotizing enterocolitis and gastrointestinal surgery.

Adenoviruses have recently been recognized as etiologic agents of enteric disease in hospitalized infants and young children. Patients who have undergone surgical procedures related to the complications of neonatal necrotizing enterocolitis constitute a population of infants who are often hospitalized for extended periods of time. We studied the incidence of enteric adenovirus infections in infants with necrotizing enterocolitis who had undergone intestinal surgery resulting in colostomies or ileostomies. These studies revealed that 31.7% of the hospital admissions in such patients were complicated by symptomatic infection with enteric adenoviruses. The rate of adenovirus infection in this population was significantly higher than the rate of such infections encountered in infants undergoing ostomy procedures for other conditions and in age-matched hospitalized infants without prior gastrointestinal surgery. The infections with enteric adenovirus were generally accompanied by an increase in intestinal output which was temporally associated with the excretion of adenovirus in the intestinal fluid. In addition infections with enteric adenoviruses in the infants with necrotizing enterocolitis and ostomies were associated with a marked increase in length of hospitalization as compared to uninfected infants with similar underlying gastrointestinal pathology. Epidemiologic analysis revealed that many of the cases of enteric adenovirus infection in the study population occurred during seasons in which enteric adenovirus infections were prevalent in the hospital population. These studies demonstrate that enteric adenovirus infections are major causes of morbidity in hospitalized patients who have of morbidity in hospitalized patients who have undergone ileostomy or colostomy procedures for necrotizing enterocolitis and that the prevention of enteric adenovirus infections might result in a significant improvement in the hospital care of infants with these conditions.

Adenoviridae Infections↗
PubMed2000

Internalization of adenovirus by alveolar macrophages initiates early proinflammatory signaling during acute respiratory tract infection.

Adenovirus is a common respiratory pathogen which causes a broad range of distinct clinical syndromes and has recently received attention for its potential for in vivo gene delivery. Although adenovirus respiratory tract infection (ARTI) results in dose-dependent, local inflammation, the pathogenesis of this remains unclear. We hypothesized that alveolar macrophages (AMphi) rapidly internalize adenovirus following in vivo pulmonary administration and then initiate inflammatory signaling within the lung. To evaluate the role of AMphi in the induction of lung inflammation during ARTI in vivo, we directly assessed adenovirus uptake by murine AMphi and correlated uptake with the initiation of proinflammatory gene expression. Stimulation of cytokine (tumor necrosis factor alpha [TNF-alpha], interleukin-6 [IL-6], macrophage inflammatory protein-2 [MIP-2], and MIP-1alpha) expression in the lung was evaluated at the level of mRNA (by reverse transcription-PCR [RT-PCR]) and protein (by enzyme-linked immunosorbent assay) and by identification of cells expressing TNF-alpha and IL-6 mRNA in lung tissues (by in situ hybridization) and isolated lung lavage cells (by RT-PCR). Adenovirus, labeled with the fluorescent dye (Cy3), was rapidly and widely distributed on epithelial surfaces of airways and alveoli and was very rapidly ( approximately 1 min) localized within AMphi. At 30 min after infection AMphi but not airway epithelial or vascular endothelial cells expressed mRNA for TNF-alpha and IL-6, thus identifying AMphi as the cell source of initial cytokine signaling. IL-6, TNF-alpha, MIP-2, and MIP-1alpha levels progressively increased in bronchoalveolar lavage fluid after pulmonary adenovirus infection, and all were significantly elevated at 6 h (P < 0.05). To begin to define the molecular mechanism(s) by which adenovirus initiates the inflammatory signaling in macrophages, TNF-alpha expression from adenovirus-infected RAW264.7 macrophages was evaluated in vitro. TNF-alpha expression was readily detected in adenovirus-infected RAW cell supernatant with kinetics similar to AMphi during in vivo infection. Blockage of virus uptake at specific cellular sites, including internalization (by wortmannin), endosome acidification and/or lysis (by chloroquine) or by Ca(2+) chelation (by BAPTA) completely blocked TNF-alpha expression. In conclusion, results showed that during ARTI, (i) AMphi rapidly internalized adenovirus, (ii) expression of inflammatory mediators was initiated within AMphi and not airway epithelial or other cells, and (iii) the initiation of inflammatory signaling was linked to virion uptake by macrophages occurring at a point after vesicle acidification. These results have implications for our understanding of the role of the AMphi in the initiation of inflammation following adenovirus infection and adenovirus-mediated gene transfer to the lung.

Acute Disease↗
PubMed1980

Failure of accumulation of cellular RNA in hamster cells stimulated to synthesize DNA by infection with adenovirus 2.

AF8 cells are temperature-sensitive mutants of the cell cycle derived from baby hamster kidney (BHK) cells which arrest in the G1 phase when incubated at the nonpermissive temperature. RNA accumulation was studied in these cells by flow cytofluorimetry following serum stimulation or adenovirus 2 infection. Serum stimulation caused an increase in the amount of RNA per cell, which reached a maximum in S and G2 cells, as repeatedly reported in the literature. However, adenovirus 2 infection caused a fraction of cells to enter S phase without any concomitant increase in the amount of RNA per cell.

Adenoviruses, Human↗
PubMed1975

Glomerular deposition of immune complexes in dogs following natural infection with canine adenovirus.

The renal lesions were studied in eight dogs which had either died as a result of acute canine adenovirus infection (Rubarth's disease) or were in various stages of recovery from the clinical disease. Using immunofluorescence techniques granular deposits of IgG were detected in the glomeruli of six dogs; four of these animals had similar glomerular deposits of canine adenovirus antigen. Eluates obtained from kidney tissue of four dogs were found to contain antiviral antibody. Histologically those animals in which glomerular deposits of IgG and viral antigen were detected showed segmental glomerular hypercellularity. These findings were attributed to the deposition of circulating virus antigen-antibody complexes in the glomeruli.

Adenoviruses, Canine↗
PubMed1977

Species identification and genome mapping of cytoplasmic adenovirus type 2 RNAs synthesized late in infection.

Adenovirus type 2 cytoplasmic RNAs synthesized late in productive infection were resolved by electrophoresis on formamide gels. Regions of the adenovirus 2 genome specifying RNAs of distinct size were determined by hybridization to specific DNA fragments generated by cleavage with endo R.EcoRI and endo R.SmaI. From these studies 13 distinct viral RNA species were identified. A 26S to 28S size class and a 21S to 23S size class were each found to consist of four distinct RNA species. Three RNA species were identified in a 16S to 18S size class, and a fourth size class, 11S to 13S, was resolved into two components. The SmaI-D region (0.38 to 0.51 on the unit genome) and the EcoRI-F, D region (0.70 to 0.83) of the genome were found to code for multiple transcripts. Three RNAs (28S, 22S, and 18S) are specified by SmaI-D, and four components, 28S, 22S, 18S, and 16S, are encoded by EcoRI-F,D. The RNA represented by each set of multiple transcripts exceeds the coding capacity of the respective region, and the species within each set of RNAs appear to contain common sequences. The relationship between the cytoplasmic RNA species synthesized at late times and early cytoplasmic RNAs was determined by hybridization-inhibition experiments. The multiple transcripts encoded by the EcoRI-D fragment were found to contain sequences that are present in early cytoplasmic RNA. These studies enabled preparation of a map which accounts for transcription of approximately 67% of the r strand of the adenovirus 2 genome.

Adenoviruses, Human↗
PubMedDate not supplied

Plasma interferon-gamma, interleukin-10 and soluble markers of immune activation in infants with primary adenovirus (ADV) and respiratory syncytial virus (RSV) infection.

Adenovirus (ADV) and respiratory syncytial virus (RSV) are etiological agents of acute respiratory tract infection in infants. Long-term prognosis of ADV infection includes severe lung damage, bronchiectasis and hyperlucent lung, while RSV infection is associated with development of recurrent wheezing and subsequent asthma. These differences may be related to differences in the primary immune responses elicited by these viruses. In this paper, we investigated the type of cytokine responses and the magnitude of immune activation in ADV and RSV infections in infants. We examined plasma concentrations of interferon-gamma (IFN-gamma), interleukin-10 (IL-10), soluble interleukin-2 receptor (sCD25) and soluble tumor necrosis factor receptor II (sTNFR-II) in previously healthy infants during the acute phase of primary ADV infection (n = 21) and RSV infection (n = 68), and in uninfected controls (n = 44). In ADV-infected infants, IFN-gamma plasma levels were significantly higher than those observed in RSV cases and the control group (p < 0.05). RSV cases did not show any differences in IFN-gamma plasma levels compared to the other groups. sCD25 levels were significantly higher in ADV- and RSV-infected infants than in controls (p < 0.0001), and higher in ADV than in RSV cases (p < 0.05). sTNFR-II levels were significantly higher in RSV- and ADV-infected infants than in controls (p < 0.0001, p < 0.05, respectively), and higher in RSV than in ADV infection (p < 0.05). No significant differences were observed in IL-10 plasma concentrations between the three groups. These results indicate that ADV and RSV infections in infants differ significantly with regard to the magnitude of production of interferon-gamma and soluble immune activation markers sCD25 and sTNFR-II. These immunological differences may be involved in the different clinical outcomes associated with these viral infections.

Acute Disease↗