Vaccinia virus induces Ca2+-independent cell-matrix adhesion during the motile phase of infection

Vaccinia virus (VV) induces two forms of cell motility: cell migration, which is dependent on the expression of early genes, and the formation of cellular projections, which requires the expression of late genes. The need for viral gene expression prior to cell motility suggests that VV proteins may affect how infected cells interact with the extracellular matrix. To address this, we have analyzed changes in cell-matrix adhesion after infection of BS-C-1 cells with VV. Whereas uninfected cells round up and detach from the culture flask in the presence of EGTA, infected cells remain attached to the culture flask with a stellate morphology. Ca2+-independent cell-matrix adhesion was evident by 10 h postinfection, after the onset of cell motility but before the formation of virus-induced cellular projections. Progression to Ca2+-independent adhesion required the expression of late viral genes but not the formation of intracellular enveloped virus particles or intracellular actin tails. Analyses of specific matrix proteins identified vitronectin and fibronectin as optimal ligands for Ca2+-independent adhesion and the formation of cellular projections. Adhesion to fibronectin was mediated via RGD motifs alone and was not inhibited by 500 micrograms of heparin/ml. Kistrin, a disintegrin which binds preferentially to the alphav beta3 (vitronectin/fibronectin) receptor inhibited the formation of cellular projections without disrupting preformed matrix interactions. Finally, we show that Ca2+-independent cell-matrix adhesion is a dynamic process which mediates changes in the morphology of VV-infected cells and uninfected cells which exhibit a transformed phenotype.

Measurement of SR Ca2+ content in the presence of caffeine in permeabilised rat cardiac trabeculae

This study was designed to measure the Ca2+ content of rat cardiac sarcoplasmic reticulum (SR) after equilibration with normal diastolic levels of Ca2+ (100 nM), in the absence and presence of caffeine. Measurements of [Ca2+] based on Fura-2 fluorescence were made from a limited bath volume (230 nl) containing individual saponin-permeabilised rat cardiac trabeculae. Injection of caffeine (5-40 mM) into this volume caused an initial release of Ca2+ from the SR, but within 30 s the SR was able to re-accumulate a significant proportion of the Ca2+. Ca2+ re-accumulation into the SR could be prevented by removal of ATP to inhibit the SR Ca2+ pump. Incubation of the preparation in an ATP-containing solution containing caffeine (5-40 mM) and 100 nM Ca2+ indicated that the SR's ability to retain Ca2+ depends inversely on the dose of caffeine. The relative Ca2+ content of the SR after preincubation with caffeine was 86.7+/-3.5% at a caffeine concentration of 5 mM, 62.5+/-5.1% at 10 mM caffeine, 37.8+/-8.1% at 20 mM caffeine and 7. 1+/-1.9% at 40 mM caffeine. Measurement of the SR Ca2+ release in the presence of different BAPTA concentrations was used to calculate (1) the Ca2+-binding capacity of the preparation (equivalent to 245+/-10 microM BAPTA) and (2) the Ca2+ content of the SR accessed by caffeine after equilibration with 100 nM Ca2+ (186+/-11 micromol/l cell volume or 5.6 mmol/l SR volume).

Extracellular enveloped vaccinia virus. Entry, egress, and evasion

Vaccinia virus is a large and complex virus that produces two types of infectious virus particles, termed intracellular mature virus (IMV) and extracellular enveloped virus (EEV). EEV contains an extra lipid envelope and ten associated proteins that are absent from IMV. Although EEV represents less than 1% of infectious progeny it is very important biologically. First, it mediates virus dissemination and second, it is the virus against which protective immune responses are directed. This article reviews the genes known to encode EEV proteins and their functions, describes recent data showing that the cellular receptors for IMV and EEV are different, and demonstrates that EEV, in contrast to IMV, is resistant to neutralisation by antibody.

Further evidence for a deficit in switching attention in schizophrenia

In this study, sustained, selective, divided, and switching attention, and reloading of working memory were investigated in schizophrenia by using a newly developed Visual Attention Battery (VAB). Twenty-four outpatients with schizophrenia and 24 control participants were studied using the VAB. Performance on VAB components was correlated with performance of standard tests. Patients with schizophrenia were significantly impaired on VAB tasks that required switching of attention and reloading of working memory but had normal performance on tasks involving sustained attention or attention to multiple stimulus features. Switching attention and reloading of working memory were highly correlated with Trails (B-A) score for patients. The decline in performance on the switching-attention task in patients with schizophrenia met criteria for a differential deficit in switching attention. Future research should examine the neurophysiological basis of the switching deficit and its sensitivity and specificity to schizophrenia.

Vaccinia virus-encoded cytokine receptor binds and neutralizes chicken interferon-gamma

To counteract the host immune response, poxviruses have evolved secreted factors that bind cytokines and thereby neutralize their biological activities. The vaccinia virus B8R gene encodes a protein that neutralizes interferon-gamma (IFN-gamma) from several mammals including man, cow, rat, and rabbit but not mice. We now report that the activity of the B8R gene product is not restricted to cytokines of mammals: it also efficiently neutralized chicken IFN-gamma. B8R blocked chicken IFN-gamma-mediated induction of guanylate binding protein RNA in the chicken fibroblast cell line CEC-32 and secretion of nitric oxide in HD-11 cells. Radiolabeled baculovirus-expressed B8R efficiently bound to immobilized recombinant chicken IFN-gamma. Scatchard analysis revealed a binding constant of chicken IFN-gamma to B8R of approximately 0.5 nM. A mutant form of chicken IFN-gamma which lacks the 18 C-terminal amino acids and which has lost more than 99% of its biological activity was able to block the IFN-gamma-neutralizing effect of B8R. Binding studies showed that the mutant protein bound radiolabeled B8R only about threefold less well than wild-type chicken IFN-gamma but failed to compete with wild-type chicken IFN-gamma for binding to the cellular receptor. These results suggest that the extreme C terminus of chicken IFN-gamma is crucial for binding to its cellular receptor but less important for recognition by the viral cytokine receptor.

Further evidence for a deficit in switching attention in schizophrenia

In this study, sustained, selective, divided, and switching attention, and reloading of working memory were investigated in schizophrenia by using a newly developed Visual Attention Battery (VAB). Twenty-four outpatients with schizophrenia and 24 control participants were studied using the VAB. Performance on VAB components was correlated with performance of standard tests. Patients with schizophrenia were significantly impaired on VAB tasks that required switching of attention and reloading of working memory but had normal performance on tasks involving sustained attention or attention to multiple stimulus features. Switching attention and reloading of working memory were highly correlated with Trails (B-A) score for patients. The decline in performance on the switching-attention task in patients with schizophrenia met criteria for a differential deficit in switching attention. Future research should examine the neurophysiological basis of the switching deficit and its sensitivity and specificity to schizophrenia.

Vascular interventions during post-chemotherapy retroperitoneal lymph-node dissection for metastatic testis cancer

AIMS

Complete excision of nodal masses during post-chemotherapy retroperitoneal lymph-node dissection (RPLND) for metastatic non-seminomatous germ-cell tumours (NSGCT) of the testis often requires vascular surgical intervention. We report our experience of vascular interventions and complications in a large series of men undergoing postchemotherapy RPLND.

METHODS

A retrospective review of vascular interventions during post-chemotherapy RPLND in 98 patients was undertaken (103 procedures).

RESULTS

Macroscopic tumour clearance was complete in 95/98 men (97%). Vascular intervention was required in all cases. Major complications included acute tubular necrosis in one patient who had undergone left nephrectomy and extensive dissection around the right renal artery, progressive atrophy of the ipsilateral kidney in three men and a colonic stricture and associated colocutaneous fistula in one patient after division of the inferior mesenteric artery. Iliac and femoral venous thrombosis developed in both patients in whom the inferior vena cava (IVC) was excised and in one patient after partial IVC excision. Eight of the 98 patients have died. No late vascular complications have occurred to date.

CONCLUSION

Complete tumour clearance can be achieved in most post-chemotherapy RPLNDs but invariably involves vascular intervention. Metastatic NSGCT should be treated by surgeons with the ability to undertake the vascular procedures required.

Extracellular enveloped vaccinia virus is resistant to complement because of incorporation of host complement control proteins into its envelope

Vaccinia virus (VV) produces two antigenically and structurally distinct infectious virions, intracellular mature virus (IMV) and extracellular enveloped virus (EEV). Here we have investigated the resistance of EEV and IMV to neutralization by complement in the absence of immune antibodies. When EEV is challenged with complement from the same species as the cells used to grow the virus, EEV is resistant to neutralization by complement, whereas IMV is not. EEV resistance was not a result of EEV protein B5R, despite its similarity to proteins of the regulators of complement activation (RCA) family, or to any of the other EEV proteins tested (A34R, A36R, and A56R gene products). EEV was sensitive to complement when the virus was grown in one species and challenged with complement from a different species, suggesting that complement resistance might be mediated by host RCA incorporated into the EEV outer envelope. This hypothesis was confirmed by several observations: (i) immunoblot analysis revealed that cellular membrane proteins CD46, CD55, CD59, CD71, CD81, and major histocompatibility complex class I antigen were detected in purified EEV but not IMV; (ii) immunoelectron microscopy revealed cellular RCA on the surface of EEV retained on the cell surface; and (iii) EEV derived from rat cells expressing the human RCA CD55 or CD55 and CD59 were more resistant to human complement than EEV derived from control rat cells that expressed neither CD55 nor CD59. These data justify further analysis of the roles of these (and possible other) cellular proteins in EEV biology.

Roles of vaccinia virus EEV-specific proteins in intracellular actin tail formation and low pH-induced cell-cell fusion

During vaccinia virus (VV) morphogenesis intracellular mature virus (IMV) is wrapped by two additional membranes to form intracellular enveloped virus (IEV). IEV particles can nucleate the formation of actin tails which aid movement of IEVs to the cell surface where the outer IEV membrane fuses with the plasma membrane forming cell-associated enveloped virus (CEV) which remains attached to the cell, or extracellular enveloped virus (EEV) which is shed from the cell. In this report, we have used a collection of VV mutants lacking individual EEV-specific proteins to compare the roles of these proteins in the formation of IEV and IEV-associated actin tails and fusion of infected cells after a low pH shock. Data presented here show that p45-50 (A36R) is not required for IEV formation or for acid-induced cell-cell fusion, but is required for formation of IEV-associated actin tails. In contrast, gp86 (A56R), the virus haemagglutinin, is not required for formation of either IEV or IEV-associated actin tails. Data presented also confirm that p37 (gene F13L), gp42 (B5R) and gp22-24 (A34R) are needed for formation of IEV-associated actin tails and for cell-cell fusion after low pH shock. The phenotypes of these mutants were not affected by the host cell type as similar results were obtained in a range of different cells. Lastly, comparisons of the phenotypes of VV strains Western Reserve, deltaA34R and deltaA36R demonstrate that actin tails are not required for low pH-induced cell-cell fusion.

Modified vaccinia virus Ankara undergoes limited replication in human cells and lacks several immunomodulatory proteins: implications for use as a human vaccine

Modified virus Ankara (MVA) is a vaccinia virus (VV) strain that was attenuated by serial passage through chick embryo fibroblasts (CEFs) and contains six large genomic deletions compared with parental virus. MVA replicates well in CEFs, but poorly in most mammalian cells. Recombinant MVA is a promising human vaccine candidate due to its restricted host range, immunogenicity and avirulence in animal models, and excellent safety record as a smallpox vaccine. Here we present a further characterization of MVA and demonstrate that: (i) MVA can replicate, albeit poorly, in transformed human cell lines, but not in primary human fibroblasts although there is limited cell-to-cell spread; (ii) MVA is a potent inducer of type I interferon (IFN) from primary human cells, which may restrict virus spread in vivo; and (iii) unlike other VV strains, MVA does not express soluble receptors for IFN-gamma, IFN-alpha/beta, tumour necrosis factor and CC chemokines, but does express a soluble interleukin-1beta receptor. This provides a plausible and testable explanation for the good immunogenicity of MVA despite its poor replication in mammals. The implications of these findings for the use of MVA as a safe and immunogenic human vaccine candidate are discussed.

A review of the actions and control of intracellular pH in vascular smooth muscle

OBJECTIVE

This review is an account of the physiological issues involved in the effects of pH on vascular smooth muscle tone. The following criteria were considered when reviewing the literature: (i) the type of smooth muscle, i.e. either tonic or phasic, (ii) the source of the smooth muscle i.e. pulmonary, systemic, large artery, resistance artery, vein or cell line, (iii) the effects of changing intracellular or extracellular pH alone, (iv) the acute or chronic effects of altered pH (v) the influence of extracellular pH on intracellular pH and (vi) the influence of altered intracellular pH on basal or agonist induced tone. Studies of the effects of pH on the individual intracellular components of vascular tone, specifically sarcoplasmic reticulum and contractile proteins function are considered. Finally, the pH sensitivity of molecular components that contribute to smooth muscle cell tone are reviewed.

CONCLUSIONS

There appear to be distinct differences in the response of large arteries and resistance arteries to altered intracellular pH which may be based on the different properties of the smooth muscle within the wall of each blood vessel. Similarly, systemic and pulmonary vessels may respond differently, but no systematic study exists to allow a more definitive conclusion. Factors controlling intracellular pH such as intracellular buffering power and sarcolemmal pH regulating mechanisms may differ across the vascular bed and may contribute to some of the differences observed in response to altered extracellular pH. Finally, few studies have examined the pH sensitivity the intracellular processes involved in basal tone and pharmaco-mechanical coupling in vascular smooth muscle. More information concerning these latter aspects of smooth muscle function is required to progress the understanding of the modulator action on pH on vascular tone.

Expression of African swine fever virus envelope protein j13L inhibits vaccinia virus morphogenesis

The African swine fever virus (ASFV) strain Malawi LIL20/1 open reading frame (ORF) j13L was expressed in vaccinia virus (VV) from a strong synthetic late promoter as either a complete ORF (vSJ1) or lacking codons 1-31 (vSJ2). Each recombinant VV produced a small plaque which rapidly reverted to a normal size upon passage. The yield of infectious virus from a single cycle infection with vSJ1 or vSJ2 was reduced 50- to 100-fold compared to wild-type (wt) and a revertant virus (vSJ5) in which the j13L ORF was removed and the VV thymidine kinase gene restored. PCR analysis of nine spontaneous large plaque revertant viruses, recovered after passage of vSJ1 in BSC-40 cells, showed that six had lost the j13L ORF and the co-inserted beta-galactosidase gene. Three viruses retained the j13L and beta-galactosidase genes, but in each case the j13L protein was not expressed due to a different single base deletion near the 5' end of the j13L coding region which introduced a stop codon a short distance downstream. The formation of intracellular mature virus (IMV) and extracellular enveloped virus was reduced 50- to 75-fold in cells infected with vSJ1 compared to wt VV and revertant vSJ5. Electron microscopy showed aberrant IMV precursor structures in vSJ1-infected cells, and immunoelectron microscopy demonstrated that these structures contained j13L protein. These results indicate that expression of the j13L protein is toxic for VV replication due to interference with VV morphogenesis prior to IMV formation.

Intracellular and extracellular vaccinia virions enter cells by different mechanisms

Vaccinia virus (VV) produces two antigenically distinct infectious virions, intracellular mature virus (IMV) and extracellular enveloped virus (EEV). Structurally, EEV consists of an IMV with an additional outer membrane containing proteins that are absent from IMV. EEV is important for virus dissemination both in vitro and in vivo. Studies of EEV entry have been hampered by having two infectious virions and by the rupture of the EEV outer membrane in the majority of EEV virions during their purification. To overcome these problems, we have developed a novel approach to study VV entry that is based on confocal microscopy and does not require EEV purification. This assay relies on immunofluorescent staining and detection of individual, intracellular, uncoated virus cores. By this method, we show that EEV entry, in contrast to IMV, is dependent on a low-pH pathway and that the IMV enwrapped inside the EEV exhibits a low-pH fusogenic activity. Together with neutralization data demonstrating that exposure to low pH disrupts the EEV outer membrane, this study strongly supports a model for EEV entry which consists of binding, endocytosis, low-pH-induced disruption of the EEV outer membrane and fusion of the exposed IMV with the endosomal membrane releasing the core into the cytosol. The roles of the EEV outer membrane in virus dissemination and virus entry are discussed in relation to this model.

Enhanced immunogenicity for CD8+ T cell induction and complete protective efficacy of malaria DNA vaccination by boosting with modified vaccinia virus Ankara

Immunization with irradiated sporozoites can protect against malaria infection and intensive efforts are aimed at reproducing this effect with subunit vaccines. A particular sequence of subunit immunization with pre-erythrocytic antigens of Plasmodium berghei, consisting of single dose priming with plasmid DNA followed by a single boost with a recombinant modified vaccinia virus Ankara (MVA) expressing the same antigen, induced unprecedented complete protection against P. berghei sporozoite challenge in two strains of mice. Protection was associated with very high levels of splenic peptide-specific interferon-gamma-secreting CD8+ T cells and was abrogated when the order of immunization was reversed. DNA priming followed by MVA boosting may provide a general immunization regime for induction of high levels of CD8+ T cells.

The mechanism of Ca2+ release from the SR of permeabilised guinea-pig and rat ureteric smooth muscle

Recent work has indicated that there is a major difference in the Ca2+ store of smooth muscle from rat and guinea-pig ureter; with the rat store being agonist-sensitive but ryanodine insensitive and the guinea-pig store being ryanodine sensitive but agonist insensitive [Th. V. Burdyga, M.J. Taggart, S. Wray, J. Physiol. 489 (1995) 327-335]. We have therefore examined directly the mechanism of Ca2+ release from the internal Ca2+ store (SR). Following permeabilisation with alpha-toxin or beta-escin the SR was Ca(2+)-loaded before application of carbachol or caffeine. Only carbachol evoked a transient contraction in rat ureter. The carbachol-induced contraction was blocked by heparin and cyclopiazonic acid (CPA) but not ryanodine. Only caffeine produced contraction in guinea-pig ureter, and this was blocked by ryanodine. Direct application of IP3 caused a small transient contraction in rat but not guinea-pig ureter. We conclude that rat ureter possesses only an IP3 sensitive store while guinea-pig ureter only has a ryanodine sensitive store.

Enhancement of MHC class I-restricted peptide-specific T cell induction by a DNA prime/MVA boost vaccination regime

Human immunodeficiency virus (HIV) vaccine candidates were previously constructed as a string of cytotoxic T lymphocyte (CTL) epitopes delivered and expressed using DNA and modified virus Ankara (MVA; an attenuated vaccinia virus) vectors. These vaccines were shown to induce interferon (IFN)-gamma-producing and cytolytic CD8+ T cells after a single vaccine administration. In the course of this work, immunization protocols were sought which would improve the levels of induced HIV-specific T cells. It was found that previous immunological exposure to MVA reduced the efficiency of subsequent priming and boosting using the same vaccine vehicle. However, a combined regime whereby the animals were first primed with the DNA vaccine and then boosted with MVA was the most potent protocol for the induction of both interferon-gamma-producing and cytolytic T cells against two CTL epitopes simultaneously. The general applicability of this novel vaccination method for induction of major histocompatibility complex class I-restricted T cells is discussed.

The extracellular domain of vaccinia virus protein B5R affects plaque phenotype, extracellular enveloped virus release, and intracellular actin tail formation

Vaccinia virus produces two morphologically distinct forms of infectious virus, termed intracellular mature virus (IMV) and extracellular enveloped virus (EEV). EEV is important for virus dissemination within a host and has different surface proteins which bind to cell receptors different from those used by IMV. Six genes are known to encode EEV-specific proteins. One of these, B5R, encodes a 42-kDa glycoprotein with amino acid similarity to members of the complement control protein superfamily and contains four copies of a 50- to 70-amino-acid repeat called the short consensus repeat (SCR). Deletion of B5R causes a small-plaque phenotype, a 10-fold reduction in EEV formation, and virus attenuation in vivo. In this study, we inserted mutated versions of the B5R gene lacking different combinations of the SCRs into a virus deletion mutant lacking the B5R gene. The resultant viruses each formed small plaques only slightly larger than those of the deletion mutant; however, the virus containing only SCR 1 formed plaques slightly larger than those of viruses with SCRs 1 and 2 or SCRs 1, 2, and 3. All of these viruses produced approximately 50-fold more infectious EEV than wild-type virus and formed comet-shaped plaques under liquid overlay. Despite producing more EEV, the mutant viruses were unable to induce the polymerization of actin on intracellular virus particles. The implications of these results for our understanding of EEV formation, release, and infectivity are discussed.

Effects of cytosolic Ca2+ on the Ca2+ content of the sarcoplasmic reticulum in saponin-permeabilized rat ventricular trabeculae

Rat ventricular trabeculae were mounted for isometric tension recording, and then permeabilized with saponin. The Ca2+ concentration ([Ca2+]) within the permeabilized preparation (cytosolic [Ca2+]) was monitored continuously using Indo-1 and the integrals of Ca2+ transients resulting from brief caffeine application used as an index of the sarcoplasmic reticulum (SR) Ca2+ content. The relationship between SR Ca2+ content and cytosolic [Ca2+] was studied within the reported physiological range (i.e. 50-250 nmol . l-1 Ca2+). Increasing cytosolic [Ca2+] from 50 nmol . l-1 to 250 nmol . l-1 increased the steady-state SR Ca2+ content about threefold. However, increasing [Ca2+] above 250 nmol . l-1 typically resulted in spontaneous SR Ca2+ release, with no further increase in SR Ca2+ content. The SR Ca2+ content increased only slowly when cytosolic [Ca2+] was increased; it was unchanged 20 s after a rapid increase in cytosolic [Ca2+], but increased progressively to a new steady-state level during the following 1-2 min. In a parallel series of experiments using intact papillary muscles, increasing extracellular [Ca2+] (from 0.5 to 5 mmol . l-1) significantly increased twitch tension within 20 s of the solution change. These results support previous suggestions that the SR Ca2+ content may increase when diastolic cytosolic [Ca2+] rises during inotropic interventions such as increased stimulus rate or extracellular [Ca2+]. However, the rate at which SR Ca2+ responds to changes in cytoplasmic [Ca2+] within the diastolic range does not appear rapid enough to explain the early potentiation of twitch tension in intact preparations after an increase in extracellular [Ca2+].

The PA influenza virus polymerase subunit is a phosphorylated protein

The induction of proteolysis by expression of the influenza virus PA polymerase subunit is the only biochemical activity ascribed to this protein. In the course of studying viral protein synthesis by two-dimensional gel electrophoresis, we observed the existence of several PA isoforms with different isoelectric points. These isoforms were also present when the PA gene was singly expressed in three different expression systems, indicating that a cellular activity is responsible for its post-translational modification. In vivo labelling with [32P]orthophosphate, followed by two-dimensional gel electrophoresis, clearly demonstrated the incorporation of phosphate into the PA molecule. Phosphoserine and phosphothreonine epitopes were present in PA, while phosphotyrosine residues were absent, as tested by immunoblotting with specific antibodies. These facts, as well as the presence of multiple consensus sites for casein kinase II (CKII) phosphorylation, prompted us to test the involvement of this kinase in PA covalent modification. PA protein purified by immunoprecipitation could be specifically labelled by the catalytic alpha subunit of human CKII, which was expressed and purified from bacteria. Collectively, these data demonstrate that the PA subunit of the influenza virus RNA polymerase is a phosphoprotein.

Non-uniform prolongation of intracellular Ca2+ transients recorded from the epicardial surface of isolated hearts from rabbits with heart failure

OBJECTIVES

To study the time course of Ca2+ transients recorded from the left ventricular epicardial surface of isolated hearts from rabbits with heart failure and to correlate the results with mechanical function.

METHODS

Heart failure was induced in the rabbit 8 weeks after coronary ligation (n = 17) with 13 controls. Echocardiography was used to assess in vivo left ventricular dysfunction. The fluorescent indicator Indo-1 was loaded into isolated Langendorff-perfused hearts and Ca2+ transients were recorded from 15 sites over the left ventricular epicardial surface using a single core light guide. The time course of the Ca2+ transients was analysed and the duration measured and correlated with in vitro mechanical function.

RESULTS

Significant mechanical dysfunction was produced in this model of heart failure. The mean duration of the Ca2+ transients obtained from failing hearts was prolonged (156.2 +/- 3.2 ms) when compared to controls (124.9 +/- 2.6 ms, P < 0.001). Delayed relaxation as measured by the maximum rate of intraventricular pressure decay was significantly correlated with the prolonged Ca2+ transients (r = -0.63, P < 0.001). In addition, there was increased variation of the Ca2+ transient duration in the failing hearts.

CONCLUSIONS

Coronary artery ligation-induced heart failure is associated with changes in the surviving myocardium which result in a non-uniform prolongation of Ca2+ transient duration. This suggests that there is a regional heterogeneity to the abnormal intracellular Ca2+ handling in heart failure.

Virus-induced cell motility

Many viruses induce profound changes in cell metabolism and function. Here we show that vaccinia virus induces two distinct forms of cell movement. Virus-induced cell migration was demonstrated by an in vitro wound healing assay in which infected cells migrated independently into the wound area while uninfected cells remained relatively static. Time-lapse microscopy showed that the maximal rate of migration occurred between 9 and 12 h postinfection. Virus-induced cell migration was inhibited by preinactivation of viral particles with trioxsalen and UV light or by the addition of cycloheximide but not by addition of cytosine arabinoside or rifampin. The expression of early viral genes is therefore necessary and sufficient to induce cell migration. Following migration, infected cells developed projections up to 160 microm in length which had growth-cone-like structures and were frequently branched. Time-lapse video microscopy showed that these projections were formed by extension and condensation of lamellipodia from the cell body. Formation of extensions was dependent on late gene expression but not the production of intracellular enveloped (IEV) particles. The requirements for virus-induced cell migration and for the formation of extensions therefore differ from each other and are distinct from the polymerization of actin tails on IEV particles. These data show that poxviruses encode genes which control different aspects of cell motility and thus represent a useful model system to study and dissect cell movement.

Blockade of chemokine activity by a soluble chemokine binding protein from vaccinia virus

Chemokines direct migration of immune cells into sites of inflammation and infection. Chemokine receptors are seven-transmembrane domain proteins that, in contrast to other cytokine receptors, cannot be easily engineered as soluble chemokine inhibitors. Poxviruses encode several soluble cytokine receptors to evade immune surveillance, providing new strategies for immune modulation. Here we show that vaccinia virus and other orthopoxviruses (cowpox and camelpox) express a secreted 35-kDa chemokine binding protein (vCKBP) with no sequence similarity to known cellular chemokine receptors. The vCKBP binds CC, but not CXC or C, chemokines with high affinity (Kd = 0.1-15 nM for different CC chemokines), blocks the interaction of chemokines with cellular receptors, and inhibits chemokine-induced elevation of intracellular calcium levels and cell migration in vitro, thus representing a soluble inhibitor that binds and sequesters chemokines. The potential of vCKBP as a therapeutic agent in vivo was illustrated in a guinea pig skin model by the blockade of eotaxin-induced eosinophil infiltration. a feature of allergic inflammatory reactions. Furthermore, vCKBP may enable the rational design of antagonists to neutralize pathogens that use chemokine receptors to initiate infection, such as HIV or the malarial parasite.

Immunogenicities of intravenous and intramuscular administrations of modified vaccinia virus Ankara-based multi-CTL epitope vaccine for human immunodeficiency virus type 1 in mice

A vaccine against human immunodeficiency virus (HIV) is still awaited. Although the correlates of protection remain elusive, it is likely that CD8+ T cells play an important role in the control of this infection. To firmly establish the importance of these cells in protective immunity, a means of efficient elicitation of CD8+ T cell responses in the absence of antibody is needed and, when available, might represent a crucial step towards a protective vaccine. Here, a novel vaccine candidate was constructed as a multi-cytotoxic T lymphocyte (CTL) epitope gene delivered and expressed using modified vaccinia virus Ankara (MVA). The immunogen consists of 20 human, one murine and three rhesus macaque epitopes. The non-human epitopes were included so that the vaccine can be tested for immunogenicity and optimal vaccination doses, routes and regimes in experimental animals. Mice were immunized intravenously (i.v.) or intramuscularly (i.m.) using a single dose of 10(6) p.f.u. of the recombinant MVA and the induction of CTL was assessed. It was demonstrated that both administration routes induced specific CTL responses and that the i.v. route was moderately more immunogenic than the i.m. route. The frequencies of ex vivo splenocytes producing interferon-y upon MHC class I-restricted peptide stimulation were determined using an ELISPOT assay. Also, the correct processing and presentation of some HLA-restricted epitopes in human cells was confirmed.

Complication of ventricular demand pacing after orthotopic heart transplantation: unusual case of pacemaker syndrome in an infant

BACKGROUND

Sinus node dysfunction is the most common indication for antibradycardiac permanent pacing after heart transplantation. Lack of atrioventricular synchrony during pacing can result in symptoms ranging from mild chest discomfort to severe manifestations such as dyspnea, hypotension, and cardiovascular collapse, all of which are ascribed to pacemaker syndrome. In infants pacemaker syndrome is often only recognized in the face of marked hemodynamic compromise.

RESULTS

This report details an unusual account of pacemaker syndrome in an infant after orthotopic heart transplantation.

CONCLUSIONS

Careful assessment of atrioventricular synchrony is important after infant transplantation.

Cholesterol granuloma of the breast presenting as an intracystic papilloma

Cholesterol granuloma of the breast is a rare benign condition. It is often clinically and radiologically indistinguishable from breast carcinoma. A case of cholesterol granuloma which manifested as an intracystic papilloma on ultrasound is described. This unusual ultrasonographic appearance has not previously been reported.

Vaccinia virion protein VP8, the 25 kDa product of the L4R gene, binds single-stranded DNA and RNA with similar affinity

Vaccinia virus protein VP8 is a 25 kDa product of the L4R gene and is an abundant virion protein that binds single-stranded (ss) and double-stranded (ds) DNA. Binding of ssDNA is preferred at high salt concentrations. Using a recombinant 25 kDa L4R (rL4R) protein and a gel mobility shift assay with radiolabelled oligonucleotides, the Kd for a 45mer oligonucleotide was determined to be 2 nM. The Kd was unaltered by 50 mM KCl but was reduced 35-fold by 100 mM KCl. Multiple rL4R molecules bound to a single 45mer oligonucleotide, and using oligonucleotides of different lengths it was calculated that one rL4R molecule bound every 17 nt. Binding to ssDNA was competed by both deoxyribo- and ribo-polynucleotides. RNA binding was observed for both rL4R and native VP8, purified from virions, using a gel mobility shift with a radiolabelled ssRNA of 130 nt. The Kd of rL4R for this ssRNA substrate was 3 nM in the absence of salt and binding was positively cooperative. The potential roles of L4R protein in vaccinia virus early transcription are discussed.

Vaccinia virus immune evasion

Vaccinia virus and other poxviruses express a wide variety of proteins which are non-essential for virus replication in culture but help the virus to evade the host response to infection. Examples include proteins which oppose apoptosis, synthesise steroids, capture chemokines, counteract complement, interfere with interferon and intercept interleukins. This review provides an overview of such proteins, with an emphasis on work from our laboratory, and illustrates how the study of these proteins can increase our understanding of virus pathogenesis, the function of the immune system and how to make safer and more immunogenic poxvirus-based vaccines.

Antibodies against vaccinia virus do not neutralize extracellular enveloped virus but prevent virus release from infected cells and comet formation

Vaccinia virus (VV) produces two antigenically and structurally distinct infectious virions, intracellular mature virus (IMV) and extracellular enveloped virus (EEV). EEV is important for the efficient dissemination of virus both in vivo and in vitro where it causes formation of comet-shaped virus plaques. Here, we show that EEV, in contrast to IMV, is resistant to neutralization by antibodies bound to its surface. However, antibodies against EEV can prevent comet formation in cell culture. To explain this apparent paradox, we investigated the mechanism by which antibodies inhibit comet formation and demonstrated that antibodies prevent EEV release from infected cells, and consequently comet formation, by agglutination of the virus on the cell surface. Two complementary observations allow this conclusion: first, electron microscopy showed that infected cells incubated with medium containing anti-vaccinia virus antibodies have virus aggregates on their surface; second, culture medium from these cells contained a 4 log10 fold reduction in the physical particle/ml titre in comparison with control culture. A mechanism by which antibodies to EEV proteins provide immunological protection is thus restriction of EEV release rather than neutralization of free EEV particles.

Diagnosis and management of high-pressure peristaltic contractions in cystoplasties

OBJECTIVE

To define the aetiology of and therapeutic strategy for high-pressure peristaltic contractions within colo- and caecocystoplasties associated with symptoms of frequency, urgency and urge incontinence.

PATIENTS AND METHODS

In a series of over 150 subtotal supratrigonal colo- and caeco-cystoplasties, nine patients were identified with such symptoms. These patients underwent videocystometrography (VCMG) confirming the presence of phasic peristaltic contractions of > 35 cmH2O.

RESULTS

In three cases, there was urodynamic evidence of outlet obstruction and symptoms resolved when the obstruction was surgically relieved. In the other six cases, high-pressure peristaltic contractions were present without bladder outlet obstruction. The symptoms did not respond to anticholinergic medication. Three of the six patients had tolerable symptoms which did not warrant further intervention. The other three cases had disabling urge incontinence and underwent ileal patch cystoplasty. The symptoms resolved in all three cases, although later recurred in one patient, probably due to incomplete division of the taenia coli during ileal patch cystoplasty.

CONCLUSION

It appears that colonic smooth muscle can develop high-pressure contractions in response to neobladder outlet obstruction. Relieving the obstruction ameliorates symptoms associated with these contractions and reduces the magnitude of the peristaltic waves. Symptoms related to high-pressure peristaltic contractions without neobladder outlet obstruction do not respond to anticholinergic medication but can be successfully treated by ileal patch cystoplasty.

Analysis of an interaction between the soluble vaccinia virus-coded type I interferon (IFN)-receptor and human IFN-alpha1 and IFN-alpha2

The soluble B18R protein coded by vaccinia virus exerts properties of a type I interferon (IFN)-receptor with broad species specificity. We analyzed neutralizing and binding activity of the B18R protein against several recombinant human type I IFNs. The B18R protein inhibited the antiviral potency of IFN-alpha1, IFN-alpha2, IFN-alpha8/1/8, and IFN-omega on human cells. The N-terminal domain of human type I IFN is involved in the high affinity binding to its cellular receptor. To localize the binding domain(s) of IFN with the B18R protein, competition experiments between B18R, and mapped monoclonal antibodies to IFN-alpha1 and IFN-alpha2 were performed. Surprisingly, our data indicated that the contact area between the B18R protein and IFN comprised in addition to the N-terminal region of IFN-molecule also its C-terminal portion. We suggest that this different pattern of interaction with a ligand might determine the ability of B18R protein to bind type I IFNs of different species.

The effect of cromakalim on intracellular [Ca2+] in isolated rat skeletal muscle during fatigue and metabolic blockade

The effects of the ATP-sensitive K+ channel (KATP channel) opener cromakalim on excitation-contraction (E-C) coupling were studied in skeletal muscle during fatiguing and non-fatiguing activity. Intracellular calcium concentration ([Ca2+]i) was monitored using the fluorescent indicator fura-2 in isolated single skeletal muscle fibres enzymatically dissociated from rat flexor digitorum brevis. A protocol of tetanic stimulation (50 Hz for 300 ms) with progressively shorter durations between tetani was used to induce E-C coupling failure in these cells. Cromakalim (100-800 microM) had little effect on peak [Ca2+]i during twitch and non-fatiguing tetanic stimulation. However, with 0.4 s between tetani, 100 microM cromakalim decreased peak tetanic [Ca2+]i from 1.47 +/- 0.11 microM to 8.35 +/- 55 nM, but did not affect resting [Ca2+]i (control, 220 +/- 40 nM; with cromakalim, 171 +/- 33 nM). Cyanide (2 mM) decreased tetanic [Ca2+]i and increased resting [Ca2+]i during the stimulus protocol; with 0.4 s between tetani, peak [Ca2+]i was 820 +/- 50 nM and resting [Ca2+]i was 443 +/- 32 nM. The ability of cromakalim to inhibit E-C coupling was enhanced by the presence of cyanide. Complete blockade of metabolism by cyanide and iodoactetate (0.1 mM) caused a marked rise in resting [Ca2+]i and inhibition of the tetanic rise of [Ca2+]i. With cromakalim (100 microM) present, E-C coupling failed during metabolic blockade but without a significant increase in resting [Ca2+]i. These results are consistent with a role for the KATP channel in the failure of Ca2+ release during fatigue.

Temperature profiles during resuscitation predict survival following burns complicated by smoke inhalation injury

Temperature and resuscitation profiles of 15 non-survivors were compared with matched survivors of major burns. All patients were intubated and ventilated for smoke inhalation injury, survived more than 3 days postburn and had a cutaneous burn greater than 15 per cent of the body surface area (mean 32.3 +/- 11.0 per cent SD). Cases were matched for similar ages (within 10 years) and total body surface area burn (within 10 per cent). The rate of core temperature rise following admission to the burn unit was significantly greater in survivors (mean 0.46 +/0 0.18 degree C/h) compared with matched non-survivors (mean 0.30 +/- 0.15 degrees C/h; p < 0.01). Core temperature increased at a rate of 0.27 degrees C/h or greater in all survivors, whereas 7 non-survivors raised their core temperature at a rate less than this. The rate of skin temperature rise was also significantly greater in the survivors (mean 1.35 +/- 0.91 degrees C/h) compared with matched non-survivors (mean 0.63 +/- 0.43 degrees C/h, p < 0.01). In 13/15 survivors, the skin temperature increased at a rate of 0.6 degree C/h or greater, whereas in 8/15 non-survivors skin temperature increased at a rate less than this. There was a negative relationship between initial core temperature and delay from time of burn to admission to the burns unit in non-survivors (correlation coefficient = -0.92; p < 0.01), whereas there was no effect of delay in the survivors. These findings suggest that patients with a high mortality probability can be detected early in their clinical course by means of temperature profiles.

A novel virus binding assay using confocal microscopy: demonstration that the intracellular and extracellular vaccinia virions bind to different cellular receptors

Vaccinia virus (VV) produces two antigenically and structurally distinct infectious virions, intracellular mature virus (IMV) and extracellular enveloped virus (EEV), which bind to unidentified and possibly different cellular receptors. Studies of VV binding have been hampered by having two infectious virions and by the rupture of the EEV outer membrane in the majority of EEV virions during purification. To overcome these problems, we have developed a novel approach to study VV binding that is based on confocal microscopy and does not require EEV purification. In this assay, individual virus particles adsorbed to the cell are simultaneously distinguished and quantified by double immunofluorescence labelling with antibody markers for EEV and IMV. By this method, we show unequivocally that IMV and EEV bind to different cellular receptors. Three independent observations allow this conclusion. First, the efficiencies with which IMV and EEV bind to different cell lines are unrelated; second, cell surface digestion with some enzymes affects IMV and EEV binding differently; and third, the binding of a monoclonal antibody to cells prevents IMV binding but not EEV binding. This technique may be widely applicable for studying the binding of different viruses.

Methods for the isolation, culture and characterisation of equine pulmonary artery endothelial cells

Equine endothelial cells were isolated from the pulmonary artery by enzymatic digestion and grown to confluency. The cells were characterised by positive immunofluorescent staining for von Willebrand factor and NADPH-diaphorase staining for nitric oxide synthase. Measurements of endothelins indicated that there were significant release rates from the cells for up to six hours. Measurements of intracellular calcium concentration showed that the application of bradykinin caused a transient increase in calcium concentration with similar characteristics to those observed in other endothelial cell preparations. These tests verify the endothelial character of these cells and establish the method as a reliable means of producing a primary culture of equine endothelial cells.

Vaccinia virus serpin B13R (SPI-2) inhibits interleukin-1beta-converting enzyme and protects virus-infected cells from TNF- and Fas-mediated apoptosis, but does not prevent IL-1beta-induced fever

The vaccinia virus (VV) strain Western Reserve B13R gene encodes a 38.5 kDa intracellular polypeptide that is non-essential for virus replication in vitro and does not affect virus virulence in a murine intranasal model. The protein has 92% amino acid identity with the cowpox virus cytokine response modifier A (crmA) protein which inhibits the interleukin (IL)-1beta converting enzyme (ICE). Here, we show that extracts from THP-1 cells infected with VV strains expressing B13R prevent the cleavage of in vitro transcribed and translated pro-IL-1beta into mature IL-1beta. Similarly, THP-1 cells infected with VVs expressing B13R process pro-IL-1beta into mature IL-1beta inefficiently in situ. Despite its inhibition of ICE, B13R does not prevent fever in infected mice, a systemic effect mediated by IL-1beta. Instead, fever is controlled by the VV IL-1beta receptor, encoded by gene B15R, and deletion of both the B13R and B15R genes did not increase the febrile response compared to deletion of B15R alone. The B13R protein does, however, block apoptosis mediated by anti-Fas antibodies or by tumour necrosis factor (TNF) and cycloheximide. Using DNA fragmentation, chromium release and microscopic analyses it was shown that cells infected with wild-type VV strain WR, or a revertant virus in which the B13R gene had been re-inserted into the B13R deletion mutant, are more resistant than uninfected cells or deletion mutant-infected cells to apoptosis mediated by anti-Fas and TNF.

Myogenic contraction by modulation of voltage-dependent calcium currents in isolated rat cerebral arteries

1. Tissue blood flow and blood pressure are regulated by the spontaneous, myogenic, contraction developed by resistance arteries. However, the cellular mechanisms underlying myogenic contraction are not understood. In this study, the mechanisms of myogenic contraction in cerebral resistance arteries were investigated. 2. The vasoconstriction observed in response to increased pressure in cerebral resistance arteries (myogenic reactivity) was dependent on Ca2+ entry through voltage-dependent Ca2+ channels, since it was abolished by Ca2+ removal and by dihydropyridine antagonists of voltage-dependent Ca2+ channels. 3. Myogenic reactivity persisted in a high-K+ saline, with reduced Ca2+, where membrane potential is presumed to be clamped. Therefore, membrane depolarization alone does not fully account for the increased voltage-dependent Ca2+ channel opening. 4. Voltage-dependent Ca2+ currents in single smooth muscle cells isolated from the resistance artery were substantially increased by applying positive pressure to the patch electrode evoking membrane stretch. 5. Myogenic reactivity remained unaffected by ryanodine and therefore was independent of internal ryanodine-sensitive Ca2+ stores. 6. The myofilament Ca2+ sensitivity was not increased by elevated pressure in alpha-toxin-permeabilized arteries. However, pharmacological activation of protein kinase C or G proteins did increase the myofilament Ca2+ sensitivity. 7. Myogenic contraction over the pressure range 30-70 mmHg could be accounted for by an increase in [Ca2+]i from 100 to 200 nM. 8. It is concluded that modest increases in [Ca2+]i within the range 100-200 nM can account for that myogenic contraction, and that stretch-evoked modulation of Ca2+ currents may contribute to the myogenic response.

alpha-Toxin-permeabilised rabbit fetal ductus arteriosus is more sensitive to Ca2+ than aorta or main pulmonary artery

OBJECTIVES

The Ca2+ sensitivity of contractile protein-generated tension production was measured in the smooth muscle of the rabbit ductus arteriosus and compared with two neighbouring fetal blood vessels (main pulmonary artery and aorta). The effect of prostaglandin E2 (PGE2), 3-isobutyl-1-methylxanthine (IBMX, a phosphodiesterase inhibitor), cyclic adenosine 3'5'-monophosphate (CAMP) and forskolin (an activator of adenylate cyclase) on Ca(2+)-activated force generated by preparations from ductus arteriosus was also examined.

METHODS

Strips of smooth muscle from the three vessels were permeabilised using crude alpha-toxin from Staphylococcus aureus. The relationship between [Ca2+] and force production was then measured in the three tissues and the effect of PGE2, cAMP, IBMX and forskolin was examined on submaximal Ca(2+)-activated force (0.3 microM Ca2+) in preparations from rabbit ductus arteriosus.

RESULTS

Permeabilised smooth muscle from fetal rabbit ductus arteriosus was significantly more sensitive to Ca2+ (EC50, 0.20 microM) than its two neighbouring blood vessels aorta (EC50, 0.52 microM) and main pulmonary artery (EC50, 0.72 microM). Submaximal Ca(2+)-activated force (0.3 microM Ca2+) was depressed by PGE2 (1 nM) in the presence of IBMX (10 microM), by cAMP (10 and 100 microM) and by forskolin alone (0.1 microM and 1 microM).

CONCLUSION

PGE2-mediated depression of Ca(2+)-activated force in the smooth muscle of the ductus arteriosus may play a role in the maintenance of a patent ductus arteriosus in the fetus. The intrinsically high Ca2+ sensitivity of smooth muscle contractile proteins may aid the sustained vasoconstriction of the ductus when the PGE2 levels fall after birth.

Detrusor myopathy: an accurate predictor of bladder hypocompliance and contracture in interstitial cystitis

OBJECTIVE

To determine whether any histological characteristics within the detrusor in cases of early interstitial cystitis (IC) predict the subsequent development of severe symptoms due to bladder contracture.

PATIENTS AND METHODS

The detrusor muscle component of bladder biopsies from 21 patients with IC was examined in sections stained with haematoxylin and eosin. Videocystometrography was performed at least 2 months after the biopsy and the patients were then followed up clinically for at least 3 years.

RESULTS

The detrusor appeared normal in 13 patients; in eight there was evidence of detrusor myopathy. Patients with biopsies confirming detrusor myopathy were significantly more likely to have hypocompliant bladders than those with normal detrusor muscle histology (P < 0.02). Over the following 3 years, six of the eight patients with detrusor myopathy developed progressively severe symptoms and required subtotal cystectomy and enterocystoplasty. None of the 13 patients without detrusor myopathy required bladder substitution.

CONCLUSION

In IC, detrusor myopathy is associated with bladder hypocompliance. Patients with detrusor myopathy appear to have more severe disease and are more likely to progress to bladder contracture requiring substitution enterocystoplasty.

Stimulation of vaccinia virion DNA helicase I8R, but not A18R, by a vaccinia core protein L4R, an ssDNA binding protein

Four DNA-dependent ATPases were purified from vaccinia virions and tested for DNA helicase activity on two dsDNA substrates. ATPases D6R and D11L were inactive on both substrates, A18R unwound the substrate with a short 20 bp duplex region and 18R unwound both substrates. In addition, the 18R protein was stimulated to unwind longer DNA duplexes by a 25 kDa protein purified from vaccinia virions, representing the cleaved product of the L4R gene, an ssDNA binding protein. Purified recombinant 25 kDa L4R protein also stimulated 18R DNA helicase activity and maximum activity was observed only when there were < 13 nucleotides of DNA per molecule of L4R protein. The DNA helicase activity of the A18R protein was not stimulated by either recombinant 25 kDa L4R protein or by an E. coli ssDNA binding protein.

A mechanism for the inhibition of fever by a virus

Poxviruses encode proteins that block the activity of cytokines. Here we show that the study of such virulence factors can contribute to our understanding of not only virus pathogenesis but also the physiological role of cytokines. Fever is a nonspecific response to infection that contributes to host defense. Several cytokines induce an elevation of body temperature when injected into animals, but in naturally occurring fever it has been difficult to show that any cytokine has a critical role. We describe the first example of the suppression of fever by a virus and the molecular mechanism leading to it. Several vaccinia virus strains including smallpox vaccines express soluble interleukin 1 (IL-1) receptors, which bind IL-1 beta but not IL-1 alpha. These viruses prevent the febrile response in infected mice, whereas strains that naturally or through genetic engineering lack the receptor induce fever. Repair of the defective IL-1 beta inhibitor in the smallpox vaccine Copenhagen, a more virulent virus than the widely used vaccine strains Wyeth and Lister, suppresses fever and attenuates the disease. The vaccinia-induced fever was inhibited with antibodies to IL-1 beta. These findings provide strong evidence that IL-1 beta, and not other cytokines, is the major endogenous pyrogen in a poxvirus infection.

Soluble interferon-gamma receptors encoded by poxviruses

Poxviruses encode a broad range of proteins that counteract the formidable attack of the immune response initiated in the host after infection, among which are proteins that mimic the extracellular binding domain of host cytokine receptors and are secreted from virus-infected cells. A soluble interferon-gamma receptor (IFN-gamma R) is produced early after infection and efficiently blocks the binding of IFN-gamma to cellular receptors, thus inhibiting both the anti-viral and immune functions of IFN-gamma. An IFN-gamma R is highly conserved among members of the poxvirus family, suggesting a major role in viral pathogenesis. The highly species-specific nature of the IFN system enables questions concerning the evolutionary relationship between poxviruses and their hosts to be addressed. The IFN-gamma R encoded by myxoma virus, a natural pathogen of rabbits, is specific for rabbit IFN-gamma. However, the IFN-gamma R encoded by orthopoxviruses (vaccinia, cowpox, camelpox, ectromelia) shows a novel, broad species specificity suggesting that these viruses have evolved in several species. The implications for the unknown origin and natural host(s) of vaccinia virus are discussed.

Receptors for gamma-interferon encoded by poxviruses: implications for the unknown origin of vaccinia virus

Poxviruses encode soluble interferon-gamma receptors (IFN-gamma Rs) that inhibit IFN-gamma activity and play a major role in virus pathogenesis. In contrast to the highly species specific cellular homologues, the vaccinia IFN-gamma R has novel broad species specificity. This has implications for the unknown origin and natural host(s) of vaccinia virus, the vaccine used for smallpox eradication.

Virus proteins that bind cytokines, chemokines or interferons

Some viruses express proteins to evade non-specific host defences such as complement, interferons and the inflammatory response. Recent notable discoveries are the broad species specificity of orthopoxvirus interferon receptors, herpesvirus and poxvirus proteins related to chemokine receptors and proteins that bind more than one cytokine, interferon or chemokine.

Ligation of double-stranded and single-stranded [oligo(dT)] DNA by vaccinia virus DNA ligase

Vaccinia virus DNA ligase has been expressed in Escherichia coli, purified, and biochemically characterized. The enzyme ligates double-stranded (ds) DNA substrates with either cohesive or blunt-end termini and the latter reaction is stimulated by PEG. Vaccinia virus DNA ligase can also ligate oligo(dT) when annealed to either a poly(dA) or a poly(rA) backbone and, remarkably, free oligo(dT). This ligation of a single-stranded (ss) substrate is unique among eukaryotic DNA ligases. The enzyme requires high ATP concentrations with a Km for the overall ligation of a ssDNA substrate of 0.8 mM. The salt, divalent cation, temperature, and pH requirements of the enzyme for the optimal ligation of ss and ds substrate are described.