Mouse Adenovirus Type 1 E4orf6 Induces PKR Degradation

Protein kinase R (PKR) is a cellular kinase involved in the antiviral response. The inactivation or inhibition of this protein is a conserved activity in DNA and RNA virus infections. In contrast to human adenovirus type 5, mouse adenovirus type 1 (MAV-1) inhibits PKR activity through proteasome-dependent degradation. However, the molecular mechanism by which this process takes place is not fully understood. We investigated whether ubiquitination, MAV-1 early region 1B 55k (E1B 55k), and early region 4 orf6 (E4orf6) play a role in PKR degradation in MAV-1 infection, because the enzyme 3 (E3) ubiquitin ligase activity with these viral proteins is conserved among the Adenoviridae family. We provide evidence that E4orf6 is sufficient to induce mouse PKR degradation and that proteasome pathway inhibition blocks PKR degradation. Inhibition of neddylation of cullin, a component of E3 ubiquitin ligase complex, blocked efficient PKR degradation in MAV-1-infected cells. Finally, we demonstrated that MAV-1 degradation of PKR is specific for mouse PKR. These results indicate that counteracting PKR is mechanistically different in two species of adenoviruses. IMPORTANCE Viruses have evolved to counteract the immune system to successfully replicate in the host. Downregulation of several antiviral proteins is important for productive viral infection. Protein kinase R (PKR) is an antiviral protein that belongs to the first line of defense of the host. Because PKR senses dsRNA and blocks the cellular translation process during viral infections, it is not surprising that many viruses counteract this antiviral activity. We previously reported PKR degradation during mouse adenovirus type 1 (MAV-1) infection; however, the molecular mechanism of this activity was not fully known. This work provides evidence about the MAV-1 protein that induces PKR degradation and expands knowledge about involvement of the proteasome pathway.

The human adenovirus type 5 E1B 55-kilodalton protein is phosphorylated by protein kinase CK2

The human adenovirus type 5 (HAdV5) early region 1B 55-kDa protein (E1B-55K) is a multifunctional phosphoprotein playing several critical roles during adenoviral productive infection, e.g., degradation of host cell proteins, viral late mRNA export, and inhibition of p53-mediated transcription. Many of these functions are apparently regulated at least in part by the phosphorylation of E1B-55K occurring at a stretch of amino acids resembling a potential CK2 consensus phosphorylation motif. We therefore investigated the potential role of CK2 phosphorylation upon E1B-55K during adenoviral infection. A phosphonegative E1B-55K mutant showed severely reduced virus progeny production, although viral early, late, and structural protein levels and viral DNA replication were not obviously affected. Binding studies revealed an interaction between the CK2α catalytic subunit and wild-type E1B-55K, which is severely impaired in the phosphonegative E1B mutant. In addition, in situ the α-catalytic subunit is redistributed into ring-like structures surrounding E1B-55K nuclear areas and distinct cytoplasmic accumulations, where a significant amount of CK2α colocalizes with E1B-55K. Furthermore, in in vitro phosphorylation assays, wild-type E1B-55K glutathione S-transferase fusion proteins were readily phosphorylated by the CK2α subunit but inefficiently phosphorylated by the CK2 holoenzyme. Addition of the CK2-specific inhibitors TBB (4,5,6,7-tetrabromobenzotriazole) and DMAT (2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole) to infected cells confirmed that CK2α binding to E1B-55K is necessary for efficient phosphorylation of E1B-55K. In summary, our data show that CK2α interacts with and phosphorylates HAdV5 E1B-55K at residues S490/491 and T495 and that these posttranslational modifications are essential for E1B-55K lytic functions.

The E1B19K oncoprotein complexes with Beclin 1 to regulate autophagy in adenovirus-infected cells

The mechanisms underlying adenovirus-mediated autophagy are currently unknown. Recently, members of the Bcl-2 protein family have been associated with autophagy. It was also reported that the Bcl-2 homology-3 (BH3) domain encompassed by both Beclin 1 and Bcl-2-like proteins is essential for their pro-autophagy or anti-autophagy functions. Here, we report for the first time that E1B19K, the adenovirus BH3 domain protein, interacts with Beclin 1 to initiate autophagy. Using immunoprecipitation assays we showed that expression of E1B19K in the host cell disrupted the physical interactions between Beclin 1 and Bcl-2 proteins. The displacement of Bcl-2 was coincident with the recruitment of PI3KC3 to the Beclin 1/E1B19K complexes. As a result of the changes in the components of the Beclin 1 interactome, there was activation of PI3KC3, as showed by the identification of PI3K-mediated lipid phosphorylation, and subsequent formation of autophagosomes. Importantly, the BH3 functional domain of E1B19K protein was required for the heterodimerization with Beclin 1. We also showed that transfer of E1B19K was sufficient to trigger autophagy in cancer cells. Consistent with these data, mutant adenoviruses encompassing a deletion of the E1B19K gene produced a marked deficiency in the capability of the virus to induce autophagy as showed by examining the lipidation and cleavage of LC3-I as well as the subcellular localization of LC3-II, the decrease in the levels of p62, and the formation of autophagosomes. Our work offers new information on the mechanisms of action of the adenoviral E1B19K protein as partner of Beclin 1 and positive regulator of autophagy.

Incidence and clinical manifestations of adenoviral infection among children undergoing allogeneic stem cell transplantation

BACKGROUND

Adenoviral infection in children undergoing stem cell transplantation is associated with significant morbidity and mortality. Identification of adenoviral infection by polymerase chain reaction from blood facilitates accurate and rapid diagnosis and surveillance. The incidence of adenoviral infection among children undergoing SCT in Israel is not known.

OBJECTIVE

To estimate the incidence of adenoviral infection in pediatric SCT patients and to characterize the morbidity associated with proven infection.

METHODS

Blood samples obtained weekly from children who underwent allogeneic SCT were retrospectively tested for adenovirus using standard PCR. A total of 657 samples collected from 32 patients were examined. Correlation was made between the presence of adenovirus in samples and clinical records.

RESULTS

Of the 32 patients 4 had adenoviral infection by PCR (12.5%). Clinical disease was present in all four patients concurrent with positive PCR. Gastrointestinal complaints and abnormal hepatocellular enzymes were uniformly present. One patient died due to disseminated disease. T cell depletion was a significant risk factor for adenoviral infection (P = 0.03).

CONCLUSIONS

In the patient population studied, the incidence of adenoviral infection in children undergoing SCT was 12.5%. The combination of gastrointestinal symptoms and abnormal hepatocellular enzymes should raise the suspicion of adenoviral infection, especially when occurring during the first few months after SCT.

Control of mRNA export by adenovirus E4orf6 and E1B55K proteins during productive infection requires E4orf6 ubiquitin ligase activity

During the adenovirus infectious cycle, the early proteins E4orf6 and E1B55K are known to perform several functions. These include nuclear export of late viral mRNAs, a block of nuclear export of the bulk of cellular mRNAs, and the ubiquitin-mediated degradation of selected proteins, including p53 and Mre11. Degradation of these proteins occurs via a cellular E3 ubiquitin ligase complex that is assembled through interactions between elongins B and C and BC boxes present in E4orf6 to form a cullin 5-based ligase complex. E1B55K, which has been known for some time to associate with the E4orf6 protein, is thought to bind to specific substrate proteins to bring them to the complex for ubiquitination. Earlier studies with E4orf6 mutants indicated that the interaction between the E4orf6 and E1B55K proteins is optimal only when E4orf6 is able to form the ligase complex. These and other observations suggested that most if not all of the functions ascribed to E4orf6 and E1B55K during infection, including the control of mRNA export, are achieved through the degradation of specific substrates by the E4orf6 ubiquitin ligase activity. We have tested this hypothesis through the generation of a virus mutant in which the E4orf6 product is unable to form a ligase complex and indeed have found that this mutant behaves identically to an E4orf6(-) virus in production of late viral proteins, growth, and export of the late viral L5 mRNA.

H is for helper: granzyme H helps granzyme B kill adenovirus-infected cells

It is commonly held that the various granzymes (lethal proteases produced by cytotoxic lymphocytes) utilize their different substrate preferences to bring about various forms of target cell death. Although a considerable body of evidence supports this view, it has now become clear that human granzyme H could have evolved a proteolytic specificity that both interferes directly with adenovirus replication and prevents the virus from blocking the potent pro-apoptotic activity of granzyme B.

Inhibition of Jak1-dependent signal transduction in airway epithelial cells infected with adenovirus

Adenoviral evolution has generated mechanisms to resist host cell defense systems, but the biochemical basis for evasion of multiple antiviral pathways in the airway by adenoviruses is incompletely understood. We hypothesized that adenoviruses modulate airway epithelial responses to type I interferons by altering the levels and activation of specific Janus family kinase-signal transducer and activator of transcription (JAK-STAT) signaling components. In this study, specific effects of adenovirus type 5 (AdV) on selected JAK-STAT signal transduction pathways were identified in human tracheobronchial epithelial cells, with focus on type I interferon-dependent signaling and gene expression. We found that wild-type AdV infection inhibited IFN-alpha-induced expression of antiviral proteins in epithelial cells by blocking phosphorylation of the Stat1 and Stat2 transcription factors that are required for activation of type I interferon-dependent genes. These effects correlated with AdV-induced down-regulation of expression of the receptor-associated tyrosine kinase Jak1 through a decrease in Jak1 mRNA levels. Phosphorylation of Stat3 in response to IL-6 and oncostatin M was also lost in AdV-infected cells, indicating loss of epithelial cell responses to other cytokines that depend on Jak1. In contrast, IL-4- and IL-13-dependent phosphorylation of Stat6 was not affected during AdV infection, indicating that the virus modulates specific signaling pathways, as these Stat6-activating pathways can function independent of Jak1. Taken together, the results indicate that AdV down-regulates host epithelial cell Jak1 to assure inhibition of the antiviral effects of multiple mediators to subvert airway defense responses and establish a productive infection.

Adenovirus-Induced Extracellular Signal-Regulated Kinase Phosphorylation during the Late Phase of Infection Enhances Viral Protein Levels and Virus Progeny

The Raf/mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase (MEK)/ERK signaling cascade enhances tumor cell proliferation in many cases. Here, we show that adenovirus type 5, a small DNA tumor virus used in experimental cancer therapy, strongly induces ERK phosphorylation during the late phase of infection. Pharmacologic inhibition of ERK phosphorylation reduced virus recovery by >100-fold. Blocking MEK/ERK signaling affected virus DNA replication and mRNA levels only weakly but strongly reduced the amount of viral proteins, independently of the kinases MNK1 and PKR. Hence, adenovirus induces the oncogenic Raf/MEK/ERK signaling pathway to enhance viral progeny by sustaining the levels of viral proteins. Concerning therapy, our results suggest that the use of Raf/MEK/ERK inhibitors will interfere with the propagation of oncolytic adenoviruses.

Adenovirus mediated intra-articular expression of collagenase-3 (MMP-13) induces inflammatory arthritis in mice

OBJECTIVES

To better understand the role of collagenase-3 (MMP-13) in joint inflammation by investigating the consequences of transient overexpression of human collagenase-3 (matrix metalloproteinase-13 (MMP-13)), introduced by adenoviral gene delivery, in the mouse knee joint.

METHODS

A single dose (5x10(7) pfu) of recombinant adenovirus coding either for beta-galactosidase (RAdLacZ) or human MMP-13 (RAdMMP-13) was injected intra-articularly into the knee joint of adult mice. The joints were analysed at frequent intervals up to 4 weeks by histology, immunohistochemistry, and RNA analysis.

RESULTS

When RAdLacZ reporter virus was used, adenoviruses efficiently infected synovial cells, chondrocytes of articular cartilage, and hypertrophic chondrocytes of the growth plate. The infection was transient as no reporter gene activity was detected 3 weeks after the injection. After RAdMMP-13 injection into the knee joints, expression of human MMP-13 in joint tissues resulted in an arthritis characterised by recruitment of inflammatory cells and increased production of cytokines and chemokines, synovial hyperplasia, and pannus formation. After the loss of MMP-13 transgene expression at 3 weeks, these inflammatory changes began to diminish.

CONCLUSIONS

MMP-13 has a role in the onset of inflammatory reaction in synovium. However, damage to articular cartilage was only rarely detected after the short term overexpression of MMP-13.

Antiviral Cytokines Induce Hepatic Expression of the Granzyme B Inhibitors, Proteinase Inhibitor 9 and Serine Proteinase Inhibitor 6

Expression of the granzyme B inhibitors, human proteinase inhibitor 9 (PI-9), or the murine orthologue, serine proteinase inhibitor 6 (SPI-6), confers resistance to CTL or NK killing by perforin- and granzyme-dependent effector mechanisms. In light of prior studies indicating that virally infected hepatocytes are selectively resistant to this CTL effector mechanism, the present studies investigated PI-9 and SPI-6 expression in hepatocytes and hepatoma cells in response to adenoviral infection and to cytokines produced during antiviral immune responses. Neither PI-9 nor SPI-6 expression was detected by immunoblotting in uninfected murine or human hepatocytes. Similarly, human Huh-7 hepatoma cells were found to express only very low levels of PI-9 relative to levels detected in perforin- and granzyme-resistant CTL or lymphokine-activated killer cells. Following in vivo adenoviral infection or in vitro culture with IFN-alphabeta or IFN-gamma, SPI-6 expression was induced in murine hepatocytes. Similarly, after culture with IFN-alpha, induction of PI-9 mRNA and protein expression was observed in human hepatocytes and Huh-7 cells. IFN-gamma and TNF-alpha also induced 4- to 10-fold higher levels of PI-9 mRNA expression in Huh-7 cells, whereas levels of mRNA encoding a related serine proteinase inhibitor, proteinase inhibitor 8, were unaffected by culture of Huh-7 cells with IFN-alpha, IFN-gamma, or TNF-alpha. These findings indicate that cytokines that promote antiviral cytopathic responses also regulate expression of the cytoprotective molecules, PI-9 and SPI-6, in hepatocytes that are potential targets of CTL and NK effector mechanisms.

[A study of serum mitochondrial enzymes(mCK, mAST, mMDH) in rotavirus and adenovirus gastroenteritis in pediatric patients]

Rotavirus and adenovirus antigens in feces from 77 cases of gastroenteritis in pediatric patients were examined. Mitochondrial enzymes, mitochondrial creatine kinase(mCK), mitochondrial aspartate amino-transferase(mAST) and mitochondrial malate dehydrogenase(mMDH) activities in their sera were also measured and compared with the results of rotavirus and adenovirus antigens in the feces. Thirty-one cases were rotavirus antigen-negative(rota-negative)/adenovirus antigen-negative(adeno-negative), 5 were rota-negative/adenovirus antigen-positive(adeno-positive), 40 were rotavirus antigen-positive(rota-positive)/adeno-negative, and only one case showed positive for both antigens. The mean activities of these three enzymes were compared among 3 groups except one both positive case mentioned above and control group(n = 105) by Mann-Whitney U-test. The serum mCK activity was significantly higher in rota-positive/adeno-negative patients than in other groups(p < 0.01). On the other hand, no significant differences were observed for mAST and mMDH activities among any groups. It is suggested that these phenomena are caused by the differences of localization of these enzymes in mitochondria, that mCK is located the outer surface of inner membrane of mitochondria, and mAST and mMDH are located on the inner surface. The difference of serum mCK activity between rotavirus infection and adenovirus infection suggests that intestinal epithelial cell injury by rotavirus is stronger than that by adenovirus.

Protein kinase B/Akt activates c-Jun NH(2)-terminal kinase by increasing NO production in response to shear stress

Laminar shear stress activates c-Jun NH(2)-terminal kinase (JNK) by the mechanisms involving both nitric oxide (NO) and phosphatidylinositide 3-kinase (PI3K). Because protein kinase B (Akt), a downstream effector of PI3K, has been shown to phosphorylate and activate endothelial NO synthase, we hypothesized that Akt regulates shear-dependent activation of JNK by stimulating NO production. Here, we examined the role of Akt in shear-dependent NO production and JNK activation by expressing a dominant negative Akt mutant (Akt(AA)) and a constitutively active mutant (Akt(Myr)) in bovine aortic endothelial cells (BAEC). As expected, pretreatment of BAEC with the PI3K inhibitor (wortmannin) prevented shear-dependent stimulation of Akt and NO production. Transient expression of Akt(AA) in BAEC by using a recombinant adenoviral construct inhibited the shear-dependent stimulation of NO production and JNK activation. However, transient expression of Akt(Myr) by using a recombinant adenoviral construct did not induce JNK activation. This is consistent with our previous finding that NO is required, but not sufficient on its own, to activate JNK in response to shear stress. These results and our previous findings strongly suggest that shear stress triggers activation of PI3K, Akt, and endothelial NO synthase, leading to production of NO, which (along with O(2-), which is also produced by shear) activates Ras-JNK pathway. The regulation of Akt, NO, and JNK by shear stress is likely to play a critical role in its antiatherogenic effects.

Effects of adenovirus-mediated liver-selective overexpression of protein tyrosine phosphatase-1b on insulin sensitivity in vivo

AIM

Protein tyrosine phosphatase-1B (PTP-1B) is an intracellular PTP known to dephosphorylate and inactivate upstream tyrosine phosphoproteins in the insulin signalling cascade. We and others reported increased abundance of catalytically impaired PTP-1B in tissue lysates from obese human subjects with and without type 2 diabetes, while genetic knockout of PTP-1B improves insulin sensitivity and prevents nutritionally mediated insulin resistance and obesity. The aim of the present work was to further elucidate the role of PTP-1B in glucose metabolism in vivo.

METHODS

We used adenoviral constructs incorporating cDNAs for either wild-type (W/T) or a catalytically inactive C(215)S (C/S) mutant PTP-1B to achieve liver-selective PTP-1B overexpression in young Sprague-Dawley rats using tail vein injection, based on the high degree of hepatotropism of adenovirus 5 (Ad5). An Ad5-lacZ construct encoding beta-galactosidase was used as a control for viral effects alone. A hyperinsulinaemic euglycaemic clamp was used to study whole body glucose disposal and endogenous glucose production rates.

RESULTS

Control studies in HIRcB cells confirmed catalytic activity and inactivity of W/T and C/S respectively. Mean PTP-1B abundance was 2.24 +/- 0.02- and 2.33 +/- 0.04-fold of saline-treated control in liver lysates of W/T and C/S rats respectively. Liver selective overexpression was confirmed by analysis of tissue lysates from liver, fat and muscle tissues. Ad5 treatment did not result in a statistically or clinically significant liver injury, as determined by serum alanine aminotransferase and histological examination. Seven days post injection, no significant difference in rate of weight gain, fasting blood glucose or insulin levels were seen in any group. Similarly, under steady-state glucose clamp conditions, glucose disposal rate (R(d)), endogenous glucose production rate (EGP) and serum insulin levels were similar in all groups.

CONCLUSION

We conclude that moderate medium-term overabundance, to a degree resembling that seen in insulin-resistant states, of PTP-1B in liver tissue does not alter insulin action on glucose metabolism and that the major site of action of PTP-1B is presumably at insulin-responsive target tissue or tissues other than the liver.

Restoration of calcium handling properties of adult cardiac myocytes from hypertrophied hearts

Reductions in cardiac sarcoplasmic reticulum calcium-ATPase (Serca2a) levels are thought to underlie the prolonged calcium (Ca(2+)) transients and consequent reduced contractile performance seen in human cardiac hypertrophy and heart failure. In freshly isolated cardiac myocytes from rats with monocrotaline-induced right ventricular hypertrophy we found reduced sarcoplasmic reticulum Serca2a expression and prolonged Ca(2+)transients, characteristic of hypertrophic cardiac disease. Modulation of intracellular Ca(2+)levels, Ca(2+) kinetics or Ca(2+)sensitivity is the focus of many current therapeutic approaches to improve contractile performance in the hypertrophic or failing heart. However, the functional effects of increasing Serca2a expression on Ca(2+) handling properties in myocytes from an animal model of cardiac hypertrophy are largely unknown. Here, we describe enhancement of the deficient Ca(2+) handling properties evident in myocytes from hypertrophied hearts following adenoviral-mediated transfer of the human Serca2a gene to these myocytes. These results highlight the importance of Serca2a deficiencies in the hypertrophic phenotype of cardiac muscle and suggest a simple, effective approach for manipulation of normal cardiac function.

Adenovirus-specific translation by displacement of kinase Mnk1 from cap-initiation complex eIF4F

Translation of cellular mRNAs involves formation of a cap-binding translation initiation complex known as eIF4F, containing phosphorylated cap-binding protein eIF4E, eIF4E kinase Mnk1, eIF4A, poly(A)-binding protein and eIF4G. Adenovirus is shown to prevent cellular translation by displacing Mnk1 from eIF4F, thereby blocking phosphorylation of eIF4E. Over expression of an eIF4E mutant that cannot be phosphorylated by Mnk1 impairs translation of cellular but not viral late mRNAs. Adenovirus 100k protein is shown to bind the C-terminus of eIF4G in vivo and in vitro, the same region bound by Mnk1. In vivo, 100k protein displaces Mnk1 from eIF4G during adenovirus infection, or in transfected cells. Purified 100k protein also evicts Mnk1 from isolated eIF4F complexes in vitro. A mutant adenovirus with a temperature-sensitive 100k protein that cannot inhibit cellular protein synthesis at restrictive temperature no longer blocks Mnk1 binding to eIF4G, or phosphorylation of eIF4E. We describe a mechanism whereby adenovirus selectively inhibits the translation of cellular but not viral mRNAs by displacement of Mnk1 from eIF4G and inhibition of eIF4E phosphorylation.

Cardiac troponin I in fulminant adenovirus myocarditis treated with a 24-hour infusion of high-dose intravenous immunoglobulin

We report a successful outcome on an acute adenovirus myocarditis treated with a 24-hour high-dose intravenous immunoglobulin (24-HDIVIG) in a 4.5-year-old girl. A postviral etiology of acute myocarditis was assessed on the basis of the polymerase chain reaction technique. Among other early markers of cardiac injury, cardiac isoform of troponin-I (cTnI) was significantly correlated to the left ventricular ejection fraction (r = -0.86, p < 0.0001). Follow-up of cTnI, which might also be correlated to the short-term outcome, allows fast, easy, and noninvasive estimation of response to the aggressive treatment with 24-HDIVIG in acute adenovirus myocarditis in children.

Neuron-targeted gene transfer by adenovirus carrying neural-restrictive silencer element

Adenovirus transfers genes to a wide range of cell types, but its application to neurons has been hampered by its reduced efficiency of infection as compared with that for glia. To achieve neuron-targeted gene transfer, we have produced an adenovirus carrying the reporter lacZ gene driven by the SCG10 minimum promoter containing the neural-restrictive silencer element (NRSE), which element selectively represses the transcription of genes in non-neuronal cells. When rat hippocampal slice cultures were infected with NRSE-bearing adenovirus, beta-galactosidase-positive cells were mostly pyramidal and granular neurons, whereas infection with virus carrying a mutated NRSE resulted in beta-galactosidase expression in both neurons and glia. The results suggest that the adenovirus carrying NRSE to be a useful tool for neurontargeted gene transfer.

Enhancement of phospholipase D activity following baculovirus and adenovirus infection in Sf9 and COS-7 cells

In order to purify the human phospholipase D1 (hPLD1) for analysis of its functional properties, we applied a baculovirus-based high-expression system. As expected, Sf9 cells infected with a baculovirus encoding for the hPLD1 displayed a 7.5-fold increase in PLD activity compared to uninfected cells. Sf9 cells infected with the wild-type (WT) and other recombinant baculoviruses were used as an expression control. Surprisingly, all baculoviruses tested led to a 3-5 fold increase in basal PLD activity when compared to uninfected cells. To further characterize the nature of the increased PLD activity, the influence of ADP-ribosylation factor (ARF) and phorbol 12-myristate 13-acetate (PMA) was studied. In contrast to membranes containing the hPLD1, the PLD activity in membranes from uninfected and WT-infected Sf9 cells was not stimulated by ARF. PMA did not affect the increase in PLD activity in any case. To further study whether the virus-mediated increase in PLD activity is a more general phenomenon, we infected COS-7 cells with recombinant and WT adenoviruses. Only the infection with the WT adenovirus resulted in an approx. 2-fold increase in PLD activity. Our results demonstrate for the first time that a viral infection elevates the PLD activity in insect and mammalian cells.

Sustained phosphorylation of cytosolic phospholipase A2 accompanies cycloheximide- and adenovirus-induced susceptibility to TNF

In this report we examine the phosphorylation state of cytosolic phospholipase A2 (cPLA2) in C3HA fibroblasts that have been treated with TNF, cycloheximide (CHI), or a combination of both compounds. Our experiments show that TNF and CHI, when used independently, caused the rapid phosphorylation of cPLA2 (within 10 min). In both cases, cPLA2 was subsequently dephosphorylated to pretreatment levels by 40 min. In addition, under these conditions [3H]arachidonic acid was not released, and we could not detect a change in the activity of cPLA2 in vitro. In contrast, in cells treated with a combination of TNF and CHI, we found that the dephosphorylation of cPLA2 was inhibited, and cPLA2 remained phosphorylated for up to 2 h. In vitro we found that sustained phosphorylation of cPLA2 was accompanied by a 60 to 80% increase in the activity of cPLA2. The sustained phosphorylation of cPLA2 also occurred in cells infected with the adenovirus mutant dl309, suggesting that sustained phosphorylation may be a general requirement for the activation of cPLA2 in apoptotic cells. We also found that sustained phosphorylation of phosphoproteins is not a general consequence of apoptotic death, since the phosphorylation of p42 mitogen-activated protein kinase was not sustained. Finally, we show that the phosphatase inhibitor orthovanadate acts as does CHI to render cells susceptible to TNF, suggesting that resistance to TNF may depend on TNF's ability to induce the expression of tyrosine or dual specificity phosphatase(s).

Monitoring foreign gene expression by a human adenovirus-based vector using the firefly luciferase gene as a reporter

We have constructed a helper-independent adenovirus type 5-luciferase recombinant (Ad5-Luc 3) containing the firefly luciferase gene flanked by simian virus 40 (SV40) regulatory sequences inserted in the early region 3 (E3) of the Ad5 genome. Expression of luciferase in cells infected with Ad5-Luc3 was relatively efficient. In HeLa cells approximately 20 micrograms luciferase per 10(6) cells was made by 36 h post-infection and a 62 kilo-Dalton (kDa) luciferase band was clearly visible in a [35S]methionine-labeled Ad5-Luc 3-infected cell extract analyzed directly by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The results of experiments in which cultured cells were infected with Ad5-Luc 3 in the presence or absence of 1-beta-D-arabinofuranosyl cytosine (AraC) showed that the majority of luciferase expression was dependent on viral DNA replication. This suggested that the enzyme was probably translated primarily from mRNA derived from transcripts expressed from the major late promoter of Ad5. An anti-luciferase antibody was raised in a rabbit and used to further characterize the luciferase expressed in HeLa cells infected with Ad5-Luc 3 by immunoprecipitations and Western blot analyses. The half-life of luciferase expressed in HeLa cells infected with Ad5-Luc 3 was calculated to be approximately 6-8 h by pulse chase analysis. Luciferase is likely to be a useful marker for monitoring virus dissemination and gene expression in experimental animals because assays for enzymatic activity are extremely sensitive and backgrounds are low in all tissues. In mice inoculated intraperitoneally (i.p.) with Ad5-Luc 3, luciferase activity was detected in the liver, spleen, kidney, and lung. A single i.p. inoculation of mice with Ad5-Luc 3 was sufficient to raise anti-luciferase antibody and Ad5 neutralizing antibody which persisted for at least 8 weeks. Even in the presence of circulating anti-luciferase and Ad5 neutralizing antibodies, luciferase activity could be detected in the livers, spleens, and kidneys of mice inoculated i.p. a second time with Ad5-Luc 3.

Dynamic aspects in transient hyperphosphatasaemia of infancy

A 20-month-old boy with absence epilepsy was found to have a strikingly elevated serum alkaline phosphatase (AP) at start of treatment with valproic acid. The monitoring of this therapy made it possible to follow the elimination of AP which was shown to be a first order kinetic with a half-life of 6.1 days. A concurrent adenovirus infection was diagnosed.

Immunoassay of tear lysozyme in acute adenovirus conjunctivitis

The tear lysozyme levels were measured by immunoassay in 92 healthy subjects and 98 patients with acute adenovirus conjunctivitis. They were found to be significantly decreased during the acute phase of the disease. The extent of this decline in the tear lysozyme level was correlated with increased severity of disease. There was no significant difference in the tear lysozyme level in viral isolation-positive and isolation-negative patients. The tear lysozyme level showed return to normal levels with clinical improvement.

Cyclic nucleotide-independent protein kinases bound to cytoplasmic and nuclear polyribosomes in non-infected and adenovirus-infected HeLa cells

Cyclic nucleotide-independent protein kinase activity bound to cytoplasmic and nuclear polyribsomes from non-infected and adenovirus-infected HeLa cells was compared. The enzymes catalysed the incorporation of phosphate from gamma-(32)P-labelled ATP or GTP into acid-precipitable material in the absence of exogenous substrates. Their activity was not affected by cyclic AMP or cyclic GMP and was not inhibited by a cyclic nucleotide-dependent protein kinase-inhibitor protein. The kinases are tightly bound to polyribosomes of either origin from infected and non-infected cells, since treatment with 0.5m-NaCl did not dissociate the activity. The enzymes and the enzyme-associated endogenous substrates of cytoplasmic polyribosomes are significantly different from those of the nucleus, and adenovirus infection of the cells did not alter the nature of the enzymes or the substrates at 18-20h after infection. Nuclear kinases catalysed 3-4-fold more phosphate incorporation than did the cytoplasmic kinases. They did not phosphorylate endogenous substrates in the cytoplasmic preparations, and vice versa, which suggests that such substrates for cytoplasmic and nuclear kinases are specific. Polyacrylamide-gel electrophoresis of the phosphorylated proteins revealed the presence of a higher number of endogenous substrates in the nuclear preparation. The nuclear kinases phosphorylated all histones from HeLa cells, but the cytoplasmic ones phosphorylated predominantly the histone of mol.wt. 12000. Bovine heart kinase phosphorylated several low-molecular-weight cytoplasmic proteins and no nuclear proteins. With a DEAE-cellulose column either enzyme activity could be resolved into a number of peaks. The substrate specificities of these peaks indicate that there are at least two different forms of the enzyme in each preparation of polyribosomes.

[Activity of lactate dehydrogenase and its isofractions in experimental asymptomatic adenovirus infections]

Experimentally in 147 dog puppies an asymptomatic infection caused by adenovirus of human origin was produced and the process was caused to become manifest by administration of the same virus against the background of the effect of antilymphocyte serum. The activity of LDG in asymptomatic adenovirus infection was found to decrease in the cytoplasmic fraction of hepatocytes and to increase in the blood serum. An increase in the content of the "hepatic" complex of LDG in the blood serum and its decrease in the cytoplasmic fraction of hepatocytes was established indicating disorders in the liver function. It is concluded that asymptomatic adenovirus infection leads to the formation of the state of pre-pathology. Manifestation of the infection enhances the quantitative aspect of the changes.

Bases methylated in vitro by cell-free extracts of adenovirus-18-induced tumours

The tRNA methylase activity in vitro of adenovirus-18-induced tumour was studied. The activity expressed per mg of protein was the same for extracts of tumours induced by either adenovirus-12 or adenovirus-18. The methylated bases isolated after incubation with extract from adenovirus-18-induced tumour were N(1)-methylguanine, 1-methyladenine, 3-methyladenine and N(6)-methyladenine.

Role of adenovirus structural proteins in the cessation of host-cell biosynthetic functions

Two of the adenovirus capsid proteins, the fiber and the hexon, complexed with either KB cell or type 5 adenovirus deoxyribonucleic acid (DNA). Maximal binding occurred at 0.01 m NaCl; increasing the ionic strength of the reaction mixture to 0.2 m NaCl resulted in a decrease in the association of either antigen to DNA. Variations of pH between 6.3 and 8.4 did not affect the binding of fiber antigen to DNA. Below pH 7.5, however, there was a small decrease in the ability of the hexon to bind nucleic acid. The association between the adenovirus structural proteins and DNA was reversible and was independent of whether the DNA was native or denatured. The fiber or hexon protein inhibited the DNA-dependent ribonucleic acid (RNA) polymerase and the DNA polymerase from KB cells. On a weight basis, the fiber protein inhibited enzymatic activity to a greater extent than the hexon. Increasing the template DNA concentration decreased this inhibition. The inhibition of the DNA-dependent RNA polymerase activity by either antigen could be reversed by increasing the ionic strength of the reaction mixture. After infection of KB cells with type 5 adenovirus, the levels of DNA and RNA polymerases remained unchanged for 15 to 20 hr. Thereafter, the specific activity of both enzymes decreased. By 30 hr postinfection, the polymerase activities were only about 30% of the enzyme activities in uninfected cells.