IL-13 induced inflammation increases DPP4 abundance but does not enhance MERS-CoV replication in airway epithelia

BACKGROUND

Chronic pulmonary conditions such as asthma and COPD increase the risk of morbidity and mortality during infection with the Middle East respiratory syndrome coronavirus (MERS-CoV). We hypothesized that individuals with such comorbidities are more susceptible to MERS-CoV infection due to increased expression of its receptor, dipeptidyl peptidase 4 (DPP4).

METHODS

We modeled chronic airway disease by treating primary human airway epithelia with the Th2 cytokine IL-13, examining how this impacted DPP4 protein levels along with MERS-CoV entry and replication.

RESULTS

IL-13 exposure for 3 days led to increased DPP4 protein abundance, while a 21-day treatment increased DPP4 levels and caused goblet cell metaplasia. Surprisingly, despite this increase in receptor availability, MERS-CoV entry and replication were not significantly impacted by IL-13 treatment.

CONCLUSIONS

Our results suggest that increased DPP4 abundance is likely not the primary mechanism leading to increased MERS severity in the setting of Th2 inflammation. Transcriptional profiling analysis highlighted the complexity of IL-13 induced changes in airway epithelia, including altered expression of genes involved in innate immunity, antiviral responses, and maintenance of the extracellular mucus barrier. These data suggest that additional factors likely interact with DPP4 abundance to determine MERS-CoV infection outcomes.

Biological membranes in EV biogenesis, stability, uptake, and cargo transfer: an ISEV position paper arising from the ISEV membranes and EVs workshop

Paracrine and endocrine roles have increasingly been ascribed to extracellular vesicles (EVs) generated by multicellular organisms. Central to the biogenesis, content, and function of EVs are their delimiting lipid bilayer membranes. To evaluate research progress on membranes and EVs, the International Society for Extracellular Vesicles (ISEV) conducted a workshop in March 2018 in Baltimore, Maryland, USA, bringing together key opinion leaders and hands-on researchers who were selected on the basis of submitted applications. The workshop was accompanied by two scientific surveys and covered four broad topics: EV biogenesis and release; EV uptake and fusion; technologies and strategies used to study EV membranes; and EV transfer and functional assays. In this ISEV position paper, we synthesize the results of the workshop and the related surveys to outline important outstanding questions about EV membranes and describe areas of consensus. The workshop discussions and survey responses reveal that while much progress has been made in the field, there are still several concepts that divide opinion. Good consensus exists in some areas, including particular aspects of EV biogenesis, uptake and downstream signalling. Areas with little to no consensus include EV storage and stability, as well as whether and how EVs fuse with target cells. Further research is needed in these key areas, as a better understanding of membrane biology will contribute substantially towards advancing the field of extracellular vesicles.

The replication of a mouse adapted SARS-CoV in a mouse cell line stably expressing the murine SARS-CoV receptor mACE2 efficiently induces the expression of proinflammatory cytokines

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Delayed brain tumor (DBT) mouse cell lines stably expressing the murine angiotensin converting enzyme 2 (mACE2) have been generated.

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The cell lines are highly susceptible to mouse-adapted SARS-CoV infection.

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SARS-CoV-MA15 efficiently induced the expression of proinflammatory cytokines and IFN-β in DBT-mACE2 cells.

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DBT-mACE2 cells provide a good experimental system that is species-homologous to the in vivo systems for evaluating SARS-CoV-host interaction studies.

Infection of conventional mice with a mouse adapted (MA15) severe acute respiratory syndrome (SARS) coronavirus (CoV) reproduces many aspects of human SARS such as pathological changes in lung, viremia, neutrophilia, and lethality. However, established mouse cell lines highly susceptible to mouse-adapted SARS-CoV infection are not available. In this work, efficiently transfectable mouse cell lines stably expressing the murine SARS-CoV receptor angiotensin converting enzyme 2 (ACE2) have been generated. These cells yielded high SARS-CoV-MA15 titers and also served as excellent tools for plaque assays. In addition, in these cell lines, SARS-CoV-MA15 induced the expression of proinflammatory cytokines and IFN-β, mimicking what has been observed in experimental animal models infected with SARS-CoV and SARS patients. These cell lines are valuable tools to perform in vitro studies in a mouse cell system that reflects the species used for in vivo studies of SARS-CoV-MA15 pathogenesis.

Autonomous replication and expression of RNA 1 from black beetle virus

Black beetle virions contain two RNAs. The smaller one, RNA 2, has previously been shown to be a messenger for viral coat protein. It is shown here, by infecting sensitized Drosophila cells with the individually purified RNAs, that the larger one, RNA 1, carries the viral gene(s) required for RNA polymerase functions. RNA 2 was dispensible for synthesis of viral RNA 1 and subgenomic RNA 3 but was essential for synthesis of RNA 2 and virions. Cells infected with RNA 1 alone produced RNA 3 in proportions 10- to 20-fold greater than cells infected with virions. This overproduction of RNA 3 decreased with increasing proportions of RNA 2 in the infecting RNA 1. We conclude that RNA 1 is the previously unidentified progenitor of subgenomic RNA 3, whereas RNA 2 regulates the amount of RNA 3 produced in the infected cell.

Palmitoylations on murine coronavirus spike proteins are essential for virion assembly and infectivity

Coronavirus spike (S) proteins are palmitoylated at several cysteine residues clustered near their transmembrane-spanning domains. This is achieved by cellular palmitoyl acyltransferases (PATs), which can modify newly synthesized S proteins before they are assembled into virion envelopes at the intermediate compartment of the exocytic pathway. To address the importance of these fatty acylations to coronavirus infection, we exposed infected cells to 2-bromopalmitate (2-BP), a specific PAT inhibitor. 2-BP profoundly reduced the specific infectivities of murine coronaviruses at very low, nontoxic doses that were inert to alphavirus and rhabdovirus infections. 2-BP effected only two- to fivefold reductions in S palmitoylation, yet this correlated with reduced S complexing with virion membrane (M) proteins and consequent exclusion of S from virions. At defined 2-BP doses, underpalmitoylated S proteins instead trafficked to infected cell surfaces and elicited cell-cell membrane fusions, suggesting that the acyl chain adducts are more critical to virion assembly than to S-induced syncytial developments. These studies involving pharmacologic inhibition of S protein palmitoylation were complemented with molecular genetic analyses in which cysteine acylation substrates were mutated. Notably, some mutations (C1347F and C1348S) did not interfere with S incorporation into virions, indicating that only a subset of the cysteine-rich region provides the essential S-assembly functions. However, the C1347F/C1348S mutant viruses exhibited relatively low specific infectivities, similar to virions secreted from 2-BP-treated cultures. Our collective results indicate that the palmitate adducts on coronavirus S proteins are necessary in assembly and also in positioning the assembled envelope proteins for maximal infectivity.

Specific regulation of T helper cell 1-mediated murine colitis by CEACAM1

Carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1) is a cell surface molecule that has been proposed to negatively regulate T cell function. We have shown that CEACAM1 is associated with specific regulation of T helper cell (Th)1 pathways, T-bet–mediated Th1 cytokine signaling, and Th1-mediated immunopathology in vivo. Mice treated with anti–mouse CEACAM1-specific monoclonal antibody (mAb) CC1 during the effector phase exhibited a reduced severity of trinitrobenzene sulfonic acid colitis in association with decreased interferon (IFN)-γ production. Although oxazolone colitis has been reported as Th2 mediated, mice treated with the CC1 mAb or a CEACAM1-Fc chimeric protein exhibited a reduced severity of colitis in association with a significant reduction of IFN-γ and T-bet activation, whereas signal transducer and activator of antigen 4 activation was unaffected. Both interleukin-4 and IFN-γ gene–deficient mice exhibited less severe colitis induction by oxazolone. Direct ligation of T cells in vitro with the murine hepatitis virus spike protein, a natural ligand for the N-domain of CEACAM1, inhibited the differentiation of naive cells into Th1 but not Th2 cells and activation of Th1 but not Th2 cytokine production. These results indicate that CEACAM1 isoforms are a novel class of activation-induced cell surface molecules on T cells that function in the specific regulation of Th1-mediated inflammation such as that associated with inflammatory bowel disease.

Requirements for CEACAMs and cholesterol during murine coronavirus cell entry

Previous reports have documented that cholesterol supplementations increase cytopathic effects in tissue culture and also intensify in vivo pathogenicities during infection by the enveloped coronavirus murine hepatitis virus (MHV). To move toward a mechanistic understanding of these phenomena, we used growth media enriched with methyl-beta-cyclodextrin or cholesterol to reduce or elevate cellular membrane sterols, respectively. Cholesterol depletions reduced plaque development 2- to 20-fold, depending on the infecting MHV strain, while supplementations increased susceptibility 2- to 10-fold. These various cholesterol levels had no effect on the binding of viral spike (S) proteins to cellular carcinoembryonic antigen-related cell adhesion molecule (CEACAM) receptors, rather they correlated directly with S-protein-mediated membrane fusion activities. We considered whether cholesterol was indirectly involved in membrane fusion by condensing CEACAMs into "lipid raft" membrane microdomains, thereby creating opportunities for simultaneous binding of multiple S proteins that subsequently cooperate in the receptor-triggered membrane fusion process. However, the vast majority of CEACAMs were solubilized by cold Triton X-100 (TX-100), indicating their absence from lipid rafts. Furthermore, engineered CEACAMs appended to glycosylphosphatidylinositol anchors partitioned with TX-100-resistant lipid rafts, but cells bearing these raft-associated CEACAMs were not hypersensitive to MHV infection. These findings argued against the importance of cholesterol-dependent CEACAM localizations into membrane microdomains for MHV entry, instead suggesting that cholesterol had a more direct role. Indeed, we found that cholesterol was required even for those rare S-mediated fusions taking place in the absence of CEACAMs. We conclude that cholesterol is an essential membrane fusion cofactor that can act with or without CEACAMs to promote MHV entry.

Enhanced virulence mediated by the murine coronavirus, mouse hepatitis virus strain JHM, is associated with a glycine at residue 310 of the spike glycoprotein

The coronavirus, mouse hepatitis virus strain JHM, causes acute and chronic neurological diseases in rodents. Here we demonstrate that two closely related virus variants, both of which cause acute encephalitis in susceptible strains of mice, cause markedly different diseases if mice are protected with a suboptimal amount of an anti-JHM neutralizing antibody. One strain, JHM.SD, caused acute encephalitis, while infection with JHM.IA resulted in no acute disease. Using recombinant virus technology, we found that the differences between the two viruses mapped to the spike (S) glycoprotein and that the two S proteins differed at four amino acids. By engineering viruses that differed by only one amino acid, we identified a serine-to-glycine change at position 310 of the S protein (S310G) that recapitulated the more neurovirulent phenotype. The increased neurovirulence mediated by the virus encoding glycine at position S310 was not associated with a different tropism within the central nervous system (CNS) but was associated with increased lateral spread in the CNS, leading to significantly higher brain viral titers. In vitro studies revealed that S310G was associated with decreased S1-S2 stability and with enhanced ability to mediate infection of cells lacking the primary receptor for JHM ("receptor-independent spread"). These enhanced fusogenic properties of viruses encoding a glycine at position 310 of the S protein may contribute to spread within the CNS, a tissue in which expression of conventional JHM receptors is low.

Quaternary structure of coronavirus spikes in complex with carcinoembryonic antigen-related cell adhesion molecule cellular receptors

Oligomeric spike (S) glycoproteins extend from coronavirus membranes. These integral membrane proteins assemble within the endoplasmic reticulum of infected cells and are subsequently endoproteolyzed in the Golgi, generating noncovalently associated S1 and S2 fragments. Once on the surface of infected cells and virions, peripheral S1 fragments bind carcinoembryonic antigen-related cell adhesion molecule (CEACAM) receptors, and this triggers membrane fusion reactions mediated by integral membrane S2 fragments. We focused on the quaternary structure of S and its interaction with CEACAMs. We discovered that soluble S1 fragments were dimers and that CEACAM binding was entirely dependent on this quaternary structure. However, two differentially tagged CEACAMs could not co-precipitate with the S dimers, suggesting that binding sites were closely juxtaposed in the dimer (steric hindrance) or that a single CEACAM generated global conformational changes that precluded additional interactions (negative cooperativity). CEACAM binding did indeed alter S1 conformations, generating alternative disulfide linkages that were revealed on SDS gels. CEACAM binding also induced separation of S1 and S2. Differentially tagged S2 fragments that were free of S1 dimers were not co-precipitated, suggesting that S1 harbored the primary oligomerization determinants. We discuss the distinctions between the S.CEACAM interaction and other virus-receptor complexes involved in receptor-triggered entry.

Ultrasonic quantification of geniohyoid cross-sectional area and tissue composition: a preliminary study of age and radiation effects

BACKGROUND

This study developed and used a new, noninvasive approach to quantify cross-sectional area and tissue composition within the geniohyoid (GH) muscle in normal adults and head and neck cancer patients.

METHODS

B-mode ultrasound was used to measure GH cross-sectional area at rest and during four speech gestures and GH tissue composition at rest in normal young adults, patients with SCC head and neck cancer treated with primary radiotherapy, and normal older adults age matched with the patients.

RESULTS

Patients exhibited significantly greater GH cross-sectional area than young subjects at rest and in effortful conditions. Significantly greater muscle tissue variability across GH quadrants was observed in patients compared with normal subjects and in older compared with younger subjects.

CONCLUSIONS

B-mode ultrasound area analyses and tissue classification techniques can be used to quantify muscle changes, such as those resulting from age, radiotherapy, or rehabilitation for head and neck cancer.

Effects of lingual gestures on blood flow into the tongue: a pilot study

BACKGROUND

Reduced blood flow has been hypothesized to be a major factor in the formation of postradiation fibrosis. This study examined Doppler ultrasonography as a technique to detect changes in blood flow into the tongue during selected lingual gestures, /t/ and /k/.

METHODS

Six normal subjects, three young men (mean age, 26 years) and three older men (mean age, 66 years) were examined in an upright position using Doppler ultrasound imaging of the external carotid artery just below the lingual artery. Measurements were made with a standardized segmentation technique before and after three repetitions of four speech production gestures /t/ and /k/, each with natural and maximal force.

RESULTS

Blood flow peak systole increased significantly after the speech gestures (p < .001). Pooled before and after gesture values for older subjects were significantly lower than those for younger subjects (p < or = .05).

CONCLUSIONS

Ultrasonography is a clinically useful technique for measuring blood flow during a dynamic gesture and may be useful for measuring effects of tumor treatment and in a lingual exercise program.

Variations in disparate regions of the murine coronavirus spike protein impact the initiation of membrane fusion

The prototype JHM strain of murine hepatitis virus (MHV) is an enveloped, RNA-containing coronavirus that has been selected in vivo for extreme neurovirulence. This virus encodes spike (S) glycoproteins that are extraordinarily effective mediators of intercellular membrane fusion, unique in their ability to initiate fusion even without prior interaction with the primary MHV receptor, a murine carcinoembryonic antigen-related cell adhesion molecule (CEACAM). In considering the possible role of this hyperactive membrane fusion activity in neurovirulence, we discovered that the growth of JHM in tissue culture selected for variants that had lost murine CEACAM-independent fusion activity. Among the collection of variants, mutations were identified in regions encoding both the receptor-binding (S1) and fusion-inducing (S2) subunits of the spike protein. Each mutation was separately introduced into cDNA encoding the prototype JHM spike, and the set of cDNAs was expressed using vaccinia virus vectors. The variant spikes were similar to that of JHM in their assembly into oligomers, their proteolysis into S1 and S2 cleavage products, their transport to cell surfaces, and their affinity for a soluble form of murine CEACAM. However, these tissue culture-adapted spikes were significantly stabilized as S1-S2 heteromers, and their entirely CEACAM-dependent fusion activity was delayed or reduced relative to prototype JHM spikes. The mutations that we have identified therefore point to regions of the S protein that specifically regulate the membrane fusion reaction. We suggest that cultured cells, unlike certain in vivo environments, select for S proteins with delayed, CEACAM-dependent fusion activities that may increase the likelihood of virus internalization prior to the irreversible uncoating process.

Treatment research in speech, language and swallowing: lessons from child language disorders

Three major types of treatment research methodologies are described. Studies on child language intervention are reviewed as examples of trends and methodological issues characterizing treatment research in speech, language, and swallowing within the last 2-3 decades. Principles are drawn from that literature and suggestions for future directions are discussed with particular attention to recent efforts to support clinical trials and treatment outcomes research.

Mouse hepatitis virus receptor levels influence virus-induced cytopathology

We developed human (HeLa) cell lines in which mouse hepatitis virus receptor (MHVR) levels could be regulated by addition of tetracycline. We used these cell lines to determine whether MHVR levels impact the degree of cytopathology induced by infection with the lytic MHV A59 strain. Two cultures were studied; HeLa-MHVRlo (less than 3,000 molecules per cell) and HeLa-MHVRhi (300,000 molecules per cell). Both supported synthesis of infective A59 virus. However, the MHVRlo cells showed no virus-induced cytopathology while the MHVRhi cells uniformly died within 14 hours after infection. This cell death was not related to virus-induced syncytium formation as it occurred even in subconfluent cells overlaid with fusion-blocking antiviral antibodies. MHV A59 spike proteins produced by vaccinia vectors also killed the MHVRhi cells within 12 hours postinfection--MHVRlo cells infected in parallel were intact as judged by trypan blue exclusion. Our current hypothesis is that the accumulation of intracellular complexes composed of spike and MHVR proteins leads to acute single cell lysis.

Intracellular complexes of viral spike and cellular receptor accumulate during cytopathic murine coronavirus infections

Murine hepatitis virus (MHV) infections exhibit remarkable variability in cytopathology, ranging from acutely cytolytic to essentially asymptomatic levels. In this report, we assess the role of the MHV receptor (MHVR) in controlling this variable virus-induced cytopathology. We developed human (HeLa) cell lines in which the MHVR was produced in a regulated fashion by placing MHVR cDNA under the control of an inducible promoter. Depending on the extent of induction, MHVR levels ranged from less than approximately 1,500 molecules per cell (designated R(lo)) to approximately 300,000 molecules per cell (designated R(hi)). Throughout this range, the otherwise MHV-resistant HeLa cells were rendered susceptible to infection. However, infection in the R(lo) cells occurred without any overt evidence of cytopathology, while the corresponding R(hi) cells died within 14 h after infection. When the HeLa-MHVR cells were infected with vaccinia virus recombinants encoding MHV spike (S) proteins, the R(hi) cells succumbed within 12 h postinfection; R(lo) cells infected in parallel were intact, as judged by trypan blue exclusion. This acute cytopathology was not due solely to syncytium formation between the cells producing S and MHVR, because fusion-blocking antiviral antibodies did not prevent it. These findings raised the possibility of an intracellular interaction between S and MHVR in the acute cell death. Indeed, we identified intracellular complexes of S and MHVR via coimmunoprecipitation of endoglycosidase H-sensitive forms of the two proteins. We suggest that MHV infections can become acutely cytopathic once these intracellular complexes rise above a critical threshold level.

A role for naturally occurring variation of the murine coronavirus spike protein in stabilizing association with the cellular receptor

Murine hepatitis virus (MHV), a coronavirus, initiates infection by binding to its cellular receptor (MHVR) via spike (S) proteins projecting from the virion membrane. The structures of these S proteins vary considerably among MHV strains, and this variation is generally considered to be important in determining the strain-specific pathologies of MHV infection, perhaps by affecting the interaction between MHV and the MHVR. To address the relationships between S variation and receptor binding, assays capable of measuring interactions between MHV and MHVR were developed. The assays made use of a novel soluble form of the MHVR, sMHVR-Ig, which comprised the virus-binding immunoglobulin-like domain of MHVR fused to the Fc portion of human immunoglobulin G1. sMHVR-Ig was stably expressed as a disulfide-linked dimer in human 293 EBNA cells and was immobilized to Sepharose-protein G via the Fc domain. The resulting Sepharose beads were used to adsorb radiolabelled MHV particles. At 4 degrees C, the beads specifically adsorbed two prototype MHV strains, MHV JHM (strain 4) and a tissue culture-adapted mutant of MHV JHM, the JHMX strain. A shift to 37 degrees C resulted in elution of JHM but not JHMX. This in vitro observation of JHM (but not JHMX) elution from its receptor at 37 degrees C was paralleled by a corresponding 37 degrees C elution of receptor-associated JHM (but not JHMX) from tissue culture cells. The basis for this difference in maintenance of receptor association was correlated with a large deletion mutation present within the JHMX S protein, as sMHVR-Ig exhibited relatively thermostable binding to vaccinia virus-expressed S proteins containing the deletion. These results indicate that naturally occurring mutations in the coronavirus S protein affect the stability of the initial interaction with the host cell and thus contribute to the likelihood of successful infection by incoming virions. These changes in virus entry features may result in coronaviruses with novel pathogenic properties.

Identification of a contiguous 6-residue determinant in the MHV receptor that controls the level of virion binding to cells

Murine carcinoembryonic antigens serve as receptors for the binding and entry of the enveloped coronavirus mouse hepatitis virus (MHV) into cells. Numerous receptor isoforms are now known, and each has extensive differences in its amino terminal immunoglobulin-like domain (NTD) to which MHV binds via its protruding spike proteins. Some of these receptor alterations may affect the ability to bind viral spikes. To identify individual residues controlling virus binding differences, we have used plasmid and vaccinia virus vectors to express two forms of MHV receptor differing only in their NTD. The two receptors, designated biliary glycoproteins (Bgp) 1a and 1bNTD, varied by 29 residues in the 107 amino acid NTD. When expressed from cDNAs in receptor-negative HeLa cells, these two Bgp molecules were displayed on cell surfaces to equivalent levels, as both were equally modified by a membrane-impermeant biotinylation reagent. Infectious center assays revealed that the 1a isoform was 10 to 100 times more effective than 1bNTD in its ability to confer sensitivity to MHV (strain A59) infection. Bgp1a was also more effective than Bgp1bNTD in comparative virus absorption assays, binding 6 times-more MHV (strain A59) and 2.5 times more MHV (strain JHMX). Bgp1a was similarly more effective in promoting the capacity of viral spikes to mediate intercellular membrane fusion as judged by quantitation of syncytia following cocultivation of spike and receptor-bearing cells. To identify residues influencing these differences, we inserted varying numbers of 1b residues into the Bgp1a background via restriction fragment exchange and site-directed mutagenesis. Analysis of the resulting chimeric receptors showed that residues 38 to 43 of the NTD were key determinants of the binding and fusion differences between the two receptors. These residues map to an exposed loop (C-C' loop) in a structural model of the closely related human carcinoembryonic antigen.

Murine coronavirus membrane fusion is blocked by modification of thiols buried within the spike protein

The envelopes of murine hepatitis virus (MHV) particles are studded with glycoprotein spikes that function both to promote virion binding to its cellular receptor and to mediate virion-cell membrane fusion. In this study, the cysteine-rich spikes were subjected to chemical modification to determine whether such structural alterations impact the virus entry process. Ellman reagent, a membrane-impermeant oxidizing agent which reacts with exposed cysteine residues to effect covalent addition of large thionitrobenzoate moieties, was incubated at 37 degrees C with the JHM strain of MHV. Relative to untreated virus, 1 mM Ellman reagent reduced infectivity by 2 log(10) after 1 h. This level of inhibition was not observed at incubation temperatures below 21 degrees C, suggesting that virion surface proteins undergo thermal transitions that expose cysteine residues to modification by the reagent. Quantitative receptor binding and membrane fusion assays were developed and used to show that Ellman reagent specifically inhibited membrane fusion induced by the MHV JHM spike protein. However, this inhibition was strain specific, because the closely related MHV strain A59 was unaffected. To identify the basis for this strain specificity, spike cDNAs were prepared in which portions encoded either JHM or A59 residues. cDNAs were expressed with vaccinia virus vectors and tested for sensitivity to Ellman reagent in the fusion assays. The results revealed a correlation between the severity of inhibition mediated by Ellman reagent and the presence of a JHM-specific cysteine (Cys-1163). Thus, the presence of this cysteine increases the availability of spikes for a thiol modification that ultimately prevents fusion competence.

Postoperative emesis following otoplasty in children

Sixty unpremedicated children aged between 3 and 14 years, scheduled for otoplasty, were randomly divided into one of three groups to receive either ondansetron 0.1 mg.kg-1, droperidol 75 micrograms.kg-1, or placebo at induction of anaesthesia. All patients received a standard general anaesthetic using thiopentone, atracurium and halothane. Opioid analgesia was avoided intra-operatively and infiltration with local anaesthetic was used prior to the start of surgery. Children who received ondansetron were less likely to vomit (15%) than those who received either droperidol (40%) or placebo (60%) (p < 0.01). This group also tolerated oral ingestion of fluids and solids earlier than those who received either droperidol or placebo (p < 0.001). There was no difference between the placebo or droperidol group in the incidence of vomiting or time to ingestion of oral fluids and meals. Three patients in the ondansetron group had a self-terminating nodal rhythm which was not associated with any haemodynamic disturbances. Postoperatively there were no untoward incidents in any of the groups and all patients were discharged home the day after surgery.

Effect of general anaesthesia on prolonged intraoesophageal pH monitoring

Investigation of gastro-oesophageal reflux often includes endoscopy, usually under general anaesthesia, and pH monitoring. In most cases, the pH probe is passed when the child is awake and is poorly tolerated. The effect of general anaesthesia on pH monitoring is unknown. The aim of the study was to determine if placing the probe in the anaesthetised child gives a representative pH study. Twenty children aged 4 months to 13 years underwent oesophago-gastroduodenoscopy under general anaesthesia. A pH electrode was placed under direct vision in the distal oesophagus. pH monitoring was begun after completion of anaesthesia and continued for 18-24 hours. The study was repeated within 14 days without anaesthetic. The reproducibility of values of percent pH < 4, number of reflux episodes/hour, reflux episodes lasting > 5 min, and longest reflux episode was 85%, 90%, 75%, and 75% respectively. These results are comparable with those in adults and children in whom pH studies were performed on consecutive days (without anaesthetic) keeping all variables constant. Therefore pH data collected in a child within 24 hours of endoscopy under general anaesthesia are representative.

The effect of a combination of rectal diclofenac and caudal bupivacaine on postoperative analgesia in children

Both caudal anaesthesia and non-steroidal anti-inflammatory drugs have been used in the management of postoperative pain in children. The aim of the present study was to evaluate the combination of caudal analgesia and rectally administered diclofenac in the treatment of pain following minor surgery in children. Thirty-nine, ASA grade 1 or 2, children undergoing inguinal or penoscrotal surgery were randomly assigned to receive either a caudal block using 0.125% bupivacaine with adrenaline or a similar caudal block in combination with rectally administered diclofenac 1 mg.kg-1. Children given a caudal block alone were more likely to need analgesia in the first 24 h postoperatively. It would appear that the combination of a caudal block and rectal diclofenac in children undergoing minor lower abdominal surgery reduces the need for subsequent analgesia.

MHVR-independent cell-cell spread of mouse hepatitis virus infection requires neutral pH fusion

Receptor-specificity is a key determinant of viral tropism. In this report, however, we have demonstrated that cell-associated spread of MHV can bypass the requirement for binding to primary receptors and thereby spread to cells that are resistant to MHV infection. Anti-receptor antibody CC1, which blocks infection by MHV virions, failed to prevent cell-associated spread of MHV to receptor-negative BHK cells or receptor-positive DBT cells. Cell-associated MHV may be utilizing an alternative, low-affinity receptor that is inadequate for functional interaction with MHV virions. Theoretically, dissemination of MHV infection through a receptor-independent, cell-associated mechanism in vivo provides the potential for broader host and tissue range, and for spread of infection despite the presence neutralizing antibodies. Receptor-independent, cell-associated spread of MHV requires neutral pH fusion capability. The low pH-dependent MHV variant OBLV60, which utilizes an endocytic route of entry, does not spread through a receptor-independent mechanism. Additionally, antiviral antibodies that block MHV spike-mediated fusion inhibited cell-associated spread of infection.

Reconstitution of Flock House provirions: a model system for studying structure and assembly

Assembly of Flock House virus in infected Drosophila cells proceeds through an intermediate, the provirion, which lacks infectivity until the coat precursor protein, alpha, undergoes a spontaneous "maturation" cleavage (A. Schneemann, W. Zhong, T. M. Gallagher, and R. R. Rueckert, J. Virol 6:6728, 1992). We describe here methods for purifying provirions in a state which permitted dissociation and reassembly. Dissociation, to monomeric alpha protein and free RNA, was accomplished by freezing at pH 9.0 in the presence of 0.5 M salt and 0.1 M urea. When dialyzed at low ionic strength and pH 6.5, the dissociation products reassembled spontaneously to form homogeneous provirions with a normal complement of RNA as judged by cosedimentation with authentic virions and by ability to undergo maturation cleavage with acquisition of substantial, though subnormal, infectivity. Reconstitution experiments, i.e., remixing components after separating RNA from capsid protein, generated abnormal particles, suggesting the presence in the unfractionated dissociation products of an unidentified "nucleating" component.

Dissemination of MHV4 (strain JHM) infection does not require specific coronavirus receptors

In this report, we demonstrate the syncytial spread of MHV4 (strain JHM) infection through non-murine cell cultures which lack a specific MHV4 receptor and are therefore resistant to infection by free virions. This was achieved by allowing infected murine cells to settle onto confluent monolayers of non-murine cells in a straightforward infectious center assay. Receptor-independent syncytium formation induced by cells expressing the MHV4 spike (S) from recombinant vaccinia viruses (VV) indicated that spread was mediated by this coronavirus glycoprotein. We conclude that the S protein of MHV4 is so potently fusogenic that it does not require prior binding to a virus-specific surface receptor to induce fusion of closely-opposed plasma membranes.

Verb class distinctions and AAC language-encoding limitations

This study explored the status of an English grammatical distinction in the language of individuals who have never been able to encode that distinction previously. English past tense marking was used as a context to examine regular and irregular verb class distinctions in the language of two adults with severe congenital physical impairments who rely on augmentative and alternative communication (AAC) systems to communicate. In the subjects' lexically based AAC systems, past tense was marked on regular verbs and irregular verbs using the same strategy. The subjects accessed their AAC displays using four-digit eye gaze number codes. They were shown a novel affixation strategy through manipulation of the four-digit codes that allowed them to mark past tense on regular verbs via an affixation process. Their semantic strategy for marking past tense on irregular verbs was not changed. The subjects' patterns of use of the two strategies on exemplars of each verb class revealed limited evidence of distinctive use of the two strategies based on verb class membership. Theoretical and clinical implications are discussed.

Cell receptor-independent infection by a neurotropic murine coronavirus

The cellular receptors for a coronavirus, mouse hepatitis virus (MHV), have been recently identified as one or more members of the carcinoembryonic antigen (CEA) family. The neurotropic JHM strain of MHV (MHV-JHM) possesses a highly fusogenic surface (S) glycoprotein. This protein is now shown to promote the spread of MHV into cells lacking the specific CEA-related MHV receptor. Resistant cells are recruited into MHV-induced syncytium with consequent production of progeny virus. Cell-to-cell spread of virus via membrane fusion without the requirement for specific cell surface receptor offers a novel way for virus to spread within infected hosts.

Maturation cleavage required for infectivity of a nodavirus

Nodaviral morphogenesis involves formation of labile precursor particles, called provirions, which mature by autocatalytic cleavage of the 407-residue coat precursor protein between asparagine residue 363 and alanine residue 364. It has previously been demonstrated that maturation results in increased physicochemical stability of the virion. We show here that cleavage of coat protein in purified provirions of Flock House virus was accompanied by a five- to eightfold increase in specific infectivity. Cleavage-negative provirions, produced by site-directed mutagenesis of asparagine residue 363 to aspartate, threonine, or alanine, displayed no infectivity above revertant frequencies as measured by plaque assay. All viable revertants (nine of nine) restored asparagine to the mutated position, suggesting high specificity for asparagine at the cleavage site.

Alteration of the pH dependence of coronavirus-induced cell fusion: effect of mutations in the spike glycoprotein

Infection of susceptible murine cells with the coronavirus mouse hepatitis virus type 4 (MHV4) results in extensive cell-cell fusion at pHs from 5.5 to 8.5. The endosomotropic weak bases chloroquine and ammonium chloride do not prevent MHV4 infection. In marked contrast, we have selected variants from a neural cell line persistently infected with MHV4 which are entirely dependent on acid pH to fuse host cells and are strongly inhibited by endosomotropic weak bases. Wild-type and variant viruses were compared at the level of the fusion-active surface (S) glycoprotein gene. Cloning and sequencing of each 4,131-base open reading frame predicted a total of eight amino acid differences which fell into three distinct clusters. Each S glycoprotein, when expressed from cDNA, was synthesized in equivalent amounts, and similar proportions were transported to the cell surface. Wild-type S induced cell-cell fusion at neutral pH, whereas variant S required prolonged exposure to acidic pH to induce fusion. Expression of hybrid S genes prepared by exchange of restriction fragments between wild-type and variant cDNAs revealed that elimination of neutral pH fusion was solely dependent on amino acid alterations at positions 1067 (Q to H), 1094 (Q to H), and 1114 (L to R). These changes lie within a predicted heptad repeat region of the transmembrane cleavage fragment of S (S2). These findings demonstrate that the pH dependence of coronavirus fusion is highly variable and that this variability can be determined by as few as three amino acid residues.

The minimum alveolar concentration (MAC) and hemodynamic effects of halothane, isoflurane, and sevoflurane in newborn swine

To determine the minimum alveolar concentration (MAC) and hemodynamic responses to halothane, isoflurane, and sevoflurane in newborn swine, 36 fasting swine 4-10 days of age were anesthetized with one of the three volatile anesthetics in 100% oxygen. MAC was determined for each swine. Carotid artery and internal jugular catheters were inserted and each swine was allowed to recover for 48 h. After recovery, heart rate (HR), systemic systolic arterial pressure (SAP), and cardiac index (CI) were measured awake and then at 0.5, 1.0, and 1.5 MAC of the designated anesthetic in random sequence. The (mean +/- SD) MAC for halothane was 0.90 +/- 0.12%; the MAC for isoflurane was 1.48 +/- 0.21%; and the MAC for sevoflurane was 2.12 +/- 0.39%. Awake (mean +/- SD) measurements of HR, SAP, and CI did not differ significantly among the three groups. Compared to the awake HR, the mean HR decreased 35% at 1.5 MAC halothane (P less than 0.001), 19% at 1.5 MAC isoflurane (P less than 0.005), and 31% at 1.5 MAC sevoflurane (P less than 0.005). Compared to awake SAP, mean SAP measurements decreased 46% at 1.5 MAC halothane (P less than 0.001), 43% at 1.5 MAC isoflurane (P less than 0.001), and 36% at 1.5 MAC sevoflurane (P less than 0.005). Mean SAP at 1.0 and 1.5 MAC halothane and isoflurane were significantly less than those measured at equipotent concentrations of sevoflurane (P less than 0.005). Compared to awake CI, mean CI measurements decreased 53% at 1.5 MAC halothane (P less than 0.001) and 43% at 1.5 MAC isoflurane (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Neutralization-resistant variants of a neurotropic coronavirus are generated by deletions within the amino-terminal half of the spike glycoprotein

Neuroattenuated variants of mouse hepatitis virus type 4 (MHV-4) selected for resistance to neutralizing monoclonal antibodies (R.G. Dalziel, P.W. Lampert, P. J. Talbot, and M. J. Buchmeier, J. Virol. 59:463-471, 1986) were found to harbor large deletions in both mRNA 3 and its protein product, the 180-kilodalton viron spike (S) glycoprotein. By using antipeptide antibodies directed against selected portions of the chain, deletions were mapped to the middle of the amino-terminal S1 fragment, one of the two posttranslational cleavage products of S, and involved omission of 15 kilodaltons of protein. Deletion mutants could be selected only after multiple passage of virus through cultured cell lines; minimally passaged MHV-4 stocks contained putative point mutants selectable by neutralizing monoclonal antibodies but no deletions. Enhanced growth of deletion mutants relative to wild-type virus was observed in four cell lines used for virus propagation and was attributed to delayed and diminished cytopathic effects that allowed cultures to support virus production for prolonged periods. This hypothesis was reinforced by the finding that no selective advantage for the deletion mutants was observed in two cell lines resistant to virus-induced cytopathic effects. These results indicate that the passaging of MHV-4 in culture generates heterogeneity in S structure and eventually selects for rare neutralization-resistant deletion mutants with decreased virulence properties.

Monoclonal antibody-selected variants of MHV-4 contain substitutions and deletions in the E2 spike glycoprotein

Selection and analysis of MHV-4 (strain JHM) variants resistant to E2-specific neutralizing MAbs was performed. Two types of variation in the E2 spike glycoprotein were found. From minimally passaged stocks of MHV-4, putative point mutants were obtained. These mutants were resistant only to the MAb used to select them. In contrast, multiply passaged stocks were found to harbor variants uniformly resistant to two selecting MAbs. Northern and Western blot analysis of the viral RNAs and proteins synthesized by these doubly-resistant variants showed that they contained large deletions in both mRNA 3 and its E2 translation product, localized to a 15 kilodalton region within the amino terminal 90B post-translational fragment. The selective advantage of this second class of variants lacking sequences within E2 90B was a result of their reduced cytopathology, thereby allowing cultures to support virus production for prolonged periods.

Sequence analysis reveals extensive polymorphism and evidence of deletions within the E2 glycoprotein gene of several strains of murine hepatitis virus

Direct RNA sequence analysis of the E2 gene of wild-type MHV-4 and of neutralization resistant, neuroattenuated variants has identified a polymorphic region with respect to deletions. These variants had large deletions of 142 to 159 amino acids mapping to a localized region in the amino-terminal domain of the peplomer glycoprotein. The nucleotide sequence of the E2 gene for wild-type strain MHV-4 was found to be very similar to that of MHV-JHM but had an insertion of 423 nucleotides resulting in the addition of a stretch of 141 unique amino acids in the amino-terminal domain of E2. We propose that deletions reflect a major source of heterogeneity in the E2 protein of MHV.

Communication mode use of two hearing-impaired adolescents in conversation

Communication mode use in the dyadic conversational speech of adolescent simultaneous communication (SC)-trained hearing-impaired twin boys was investigated. Proportional frequencies of modes and the English structural characteristics of the spoken components of utterances produced in each mode were examined. The results indicated that these adolescents were using an integrated bimodal form of English with a grammatical base that did not vary as a function of the presence or absence of simultaneous signs either in their speech or their partner's speech. Implications of the results are discussed.

Spinal anaesthesia in infants born prematurely

Spinal anaesthesia was used for 25 infants who were born prematurely and who subsequently required inguinal herniotomy. Hyperbaric bupivacaine 0.5% was administered in a dose of 0.3 mg/kg. Satisfactory surgical anaesthesia was achieved in 22 patients and there were no episodes of haemodynamic instability. The technique was not associated with postoperative apnoea. Spinal anaesthesia is a safe and effective alternative to general anaesthesia in these high-risk infants. However, postoperative apnoea monitoring is still essential for all infants born prematurely.

Assembly-dependent maturation cleavage in provirions of a small icosahedral insect ribovirus

Extracts from nodavirus-infected Drosophila cells contained detergent-labile 140S "young" particles much richer than mature virions in their content of protein alpha, a precursor of coat proteins beta and gamma. Incorporation studies in infected cells showed that most newly synthesized alpha protein was assembled into young particles within a few minutes. Incubation of the particles, either in cytoplasmic extracts or after purification, resulted in spontaneous first-order cleavage of alpha protein to form beta-plus-gamma chains. Alpha protein that was not associated with particles failed to cleave. Cleavage was accompanied by a marked increase in detergent stability of the particles and was unaffected by a broad spectrum of protease inhibitors or by coating with precipitating antibody. We conclude (i) that alpha chains are cleaved only after assembly into provirions, (ii) that cleavage occurs internally and is likely therefore autocatalytic, and (iii) that cleavage stabilizes the mature virus particles.

Structure of an insect virus at 3.0 A resolution

We report the first atomic resolution structure of an insect virus determined by single crystal X-ray diffraction. Black beetle virus has a bipartite RNA genome encapsulated in a single particle. The capsid contains 180 protomers arranged on a T = 3 surface lattice. The quaternary organization of the protomers is similar to that observed in the T = 3 plant virus structures. The protomers consist of a basic, crystallographically disordered amino terminus (64 residues), a beta-barrel as seen in other animal and plant virus subunits, an outer protrusion composed predominantly of beta-sheet and formed by three large insertions between strands of the barrel, and a carboxy terminal domain composed of two distorted helices lying inside the shell. The outer surfaces of quasi-threefold related protomers form trigonal pyramidyl protrusions. A cleavage site, located 44 residues from the carboxy terminus, lies within the central cavity of the protein shell. The structural motif observed in BBV (a shell composed of 180 eight-stranded antiparallel beta-barrels) is common to all nonsatellite spherical viruses whose structures have so far been solved. This highly conserved shell architecture suggests a common origin for the coat protein of spherical viruses, while the primitive genome structure of BBV suggests that this insect virus represents an early stage in the evolution of spherical viruses from cellular genes.

Isoflurane does not reduce aortic peak flow velocity in children

Haemodynamic effects of 1 MAC halothane, enflurane and isoflurane were studied in 15 healthy children using pulsed Doppler echo cardiography. Heart rate was significantly increased with isoflurane, but not with the other two agents. All three caused comparable decreases in arterial pressure. Cardiac output was increased with isoflurane, but remained unchanged with halothane and enflurane. Aortic peak flow velocity, a sensitive index of myocardial contractility, was decreased with halothane and enflurane, but not with isoflurane. These findings indicate that isoflurane causes less myocardial depression than halothane or enflurane in children.

Interactive play: the frequency of related verbal responses

The potential relationship between interactive play and the frequency of related responding to comments was investigated within the dyadic interactions among a 4-year-old Specifically Language Impaired (SLI) boy and normal-language users. The normal-language users were of similar chronological age or language level to the SLI boy. The results indicated that the SLI boy's frequency of related responding was variable but consistently associated with the following: the ratio of other-directed partner turns in play; the frequency of a particular discourse pattern; and the frequency of shared reference across the discourse pattern. Unlike related responses of the SLI child, the frequencies of related responses of normal children were essentially stable. Implications of the differences are discussed.

Uptake of volatile anaesthetics in children

The uptake of halothane is known to be more rapid in children than in adults, but comparable clinical data regarding other inhalational anaesthetics are not available. In this study, the rates of uptake of halothane, enflurane, isoflurane and methoxyflurane were compared in children of different ages. Expired (FE') and inspired (FI) vapour concentrations were measured with an infrared analyser, and FE'/FI ratios were used to determine rates of uptake. Uptake rates of halothane, enflurane and methoxyflurane were more rapid in the younger than in the older children, but age had no effect on the uptake of isoflurane which was uniformly rapid in all the children studied.

Pragmatic assessment: analysis of a highly frequent repeated utterance

The present study examined the pragmatic role of a frequently repeated utterance, "it's gone," within the multiple context conversational interactions of a 4-year-old specifically language-impaired boy. The data indicate that the phrase was an interactive access strategy to engage his partners in a nonexistence/disappearance game, a frequent type of early mother-child interaction. The assessment and intervention implications of these data are discussed.