Reovirus mu2 protein determines strain-specific differences in the rate of viral inclusion formation in L929 cells

Reovirus infection induces the formation of large cytoplasmic inclusions that serve as the major site of viral assembly. Reovirus strains type 3 Dearing (T3D) and type 1 Lang (T1L) differ in the rate of inclusion formation in L929 cells. The median time of inclusion formation is 18 h in cells infected with T3D and 39 h in cells infected with T1L. Using reassortant viruses that contain combinations of gene segments derived from T1L and T3D, we found that the M1 gene, which encodes the mu2 protein, is the primary determinant of the rate of inclusion formation. The S3 gene, which encodes the nonstructural protein sigmaNS, plays a secondary role in this process. The subcellular location of the mu2 protein was determined by confocal laser scanning microscopy using dual-fluorescence labeling of mu2 and the outer-capsid protein mu1/mu1C. In virus-infected cells, mu2 protein colocalized with other viral proteins in inclusions and was also distributed diffusely in the cytoplasm and nucleus. Expression of recombinant T1L and T3D mu2 proteins resulted in the formation of protein complexes resembling inclusions in both the cytoplasm and the nucleus with kinetics that reflected the strain of origin. The median time of mu2 protein complex formation was 22 h in cells transfected with the T3D M1 gene and 43 h in cells transfected with the T1L M1 gene. These findings suggest that the mu2 protein influences the rate of inclusion formation and contributes to inclusion morphogenesis. The requirement of mu2 protein in inclusion formation was tested by determining the subcellular localization of mu2 in cells infected with temperature-sensitive (ts) mutants that are defective in viral assembly. In contrast to infection with wild-type virus, mu2 did not colocalize with mu1/mu1C protein in subcellular structures that formed in cells infected at nonpermissive temperature with ts mutants tsH11.2, tsC447, and tsG453 with mutations in the M1, S2, and S4 genes, respectively. These results suggest that despite the role of the mu2 protein in controlling the rate of inclusion formation, this process is a concerted function of several reovirus proteins.

Evaluation of a neonatal rat model for prediction of mumps virus neurovirulence in humans

Neurovirulence of several mumps virus strains was assessed in a prototype rat neurovirulence test and compared to results obtained in the monkey neurovirulence test. The relative human neurovirulence of these strains was proportional to the severity of hydrocephalus in rats but not to lesion scores in the monkeys.

Influenza virus genetics

Significant progress has been made in understanding the process of influenza A virus replication in cell culture; however, much less is known about the genetic control of virus-host interactions in disease. This review provides an overview of the genetic analysis of influenza virus biology. The functional map of the individual genes of influenza A virus is presented as well as the status of our current understanding of pathogenesis. Influenza has a segmented genome so it is possible to obtain reassortants that contain novel combinations of genome segments derived from different viruses. This is a very useful genetic tool and is also an important aspect of influenza evolution and biology. Human influenza viruses originate from avian strains of influenza virus so that influenza infection is at its basis a zoonosis. Influenza virus strains are host-restricted, however, and avian strains must be adapted to the human host. So questions of host-range and interaction with host factors are important determinants of the ability of influenza virus to cause disease in humans. Host-range is restricted primarily due to host-specific interactions of the ribonucleocapsid and the viral receptor. There are two classes of drugs for inhibiting influenza infection, amantadine HCl and neuraminidase inhibitors. The mode of action and basis for resistance to these drugs are presented. Prospective targets for antiviral therapy are also discussed.

Heteroduplex mobility assay-guided sequence discovery: elucidation of the small subunit (18S) rDNA sequences of Pfiesteria piscicida and related dinoflagellates from complex algal culture and environmental sample DNA pools

The newly described heterotrophic estuarine dinoflagellate Pfiesteria piscicida has been linked with fish kills in field and laboratory settings, and with a novel clinical syndrome of impaired cognition and memory disturbance among humans after presumptive toxin exposure. As a result, there is a pressing need to better characterize the organism and these associations. Advances in Pfiesteria research have been hampered, however, by the absence of genomic sequence data. We employed a sequencing strategy directed by heteroduplex mobility assay to detect Pfiesteria piscicida 18S rDNA "signature" sequences in complex pools of DNA and used those data as the basis for determination of the complete P. piscicida 18S rDNA sequence. Specific PCR assays for P. piscicida and other estuarine heterotrophic dinoflagellates were developed, permitting their detection in algal cultures and in estuarine water samples collected during fish kill and fish lesion events. These tools should enhance efforts to characterize these organisms and their ecological relationships. Heteroduplex mobility assay-directed sequence discovery is broadly applicable, and may be adapted for the detection of genomic sequence data of other novel or nonculturable organisms in complex assemblages.

Biological characteristics of genetic variants of Urabe AM9 mumps vaccine virus

The Urabe AM9 mumps vaccine is composed of a mixture of variants distinguishable by a difference at nucleotide (nt) 1081 of the hemagglutinin-neuraminidase (HN) gene (Brown, E.G., Dimock, K., Wright, K.E., 1996. The Urabe AM9 mumps vaccine is a mixture of viruses differing at amino acid (aa) 335 of the hemagglutinin-neuraminidase gene with one form associated with disease. J. Infect. Dis. 174, 619-622.). Further genetic and biological variation was detected in plaque purified viruses from the Urabe AM9 vaccine by examining the HN gene sequence, plaque morphology, cytopathic effects and growth in Vero cells, and temperature sensitivity (ts). Infection of Vero cells with plaque purified viruses with a G at nt 1081 of the HN gene produced large, clear plaques, caused significant CPE early after infection but yielded lower titres of virus than other purified viruses. None of these viruses were ts. In contrast, half of the plaque purified viruses with an A at nt 1081 were sensitive to a temperature of 39.5 degrees C. These viruses produced small plaques, caused significant CPE and grew to low titres. Two ts viruses possessed a unique aa substitution at aa 468 of HN. The remaining A(1081) viruses were not ts, produced large plaques but little CPE, and grew to titres 10-fold higher than the G(1081) viruses. Isolates of Urabe AM9 associated with post-vaccination illness were similar to these non-ts A(1081) viruses, but could be further sub-divided into two groups on the basis of a difference at aa 464 of HN. The post-vaccination isolates may represent insufficiently attenuated components of the vaccine, while the G(1081) and ts subset of A(1081) viruses may be more fully attenuated.

The mumps virus neurovirulence safety test in Rhesus monkeys: a comparison of mumps virus strains

Wild type mumps viruses are highly neurotropic and a frequent cause of aseptic meningitis in unvaccinated humans. To test whether attenuated mumps viruses used in the manufacture of mumps vaccines have neurovirulent properties, a monkey neurovirulence safety test (MNVT) is performed. However, results with several mumps virus MNVTs have raised questions as to whether the test can reliably discriminate neurovirulent from nonneurovirulent mumps virus strains. Here, various mumps virus strains representing a wide range of neuropathogenicity were tested in a standardized MNVT. A trend of higher neurovirulence scores was observed in monkeys inoculated with wild type mumps virus versus vaccine strains, although differences were not statistically significant. Results indicated the need for further examination and refinement of the MNVT or for development of alternative MNVTs.

Genetic analysis of mouse-adapted influenza A virus identifies roles for the NA, PB1, and PB2 genes in virulence

Adaptation of the prototype A/FM/1/47 H1N1 strain to mice resulted in selection of the A/FM/1/47-MA variant with increased virulence. Earlier analysis identified mutations in the HA and M1 genes that increase virulence in the mouse. Complete sequence analysis identified mutations in the PB1, PB2, HA, NA, and M1 genes. Reassortants were produced between the parental FM and FM-MA strains to obtain viruses that differ due to combinations of mutant genes. To assess the relationship between virulence and replication, the median lethal dose was determined for mice and growth properties were assessed in mouse lung, MDCK cells and chicken embryo. Not only were all five mutations shown to control virulence but also the replicative capacity in the mouse. The HA, NA and M1 mutations increased yield in all three hosts whereas in combination the PB1 and PB2 mutations were host restrictive changing the virus to a mouse specific strain. For the NA and M1 mutations the increase in growth in mouse lung was proportional to a 2-fold (log10) increase in virulence however the HA mutation increased virulence largely independent of increased growth indicating a change in pathological properties that damage the host. Thus mutations that affect virulence can be classified according to host-dependent and independent ability to increase growth as well as changes in pathological properties. Each of the PB1, PB2, NA, HA, and M1 genes acquired gain-of-function mutations for mouse infection that involve structural motifs that may serve as markers for virulence or targets for antiviral therapy.

Immunochemical localization of platelet-derived growth factor in placenta and its possible role in pre-eclampsia

BACKGROUND

Platelet-derived growth factor (PDGF) has an important role in cellular function, proliferation, and angiogenesis. It is also associated with tissue injury and repair, and its involvement in atherosclerosis has been studied extensively. Tissue injury is also found in pre-eclampsia (PRE). The morphological and physiological changes that are taking place in the PRE placenta may be associated with this growth factor. The objective of this study was to determine if PDGF-AA and its alpha receptor are present in the cells and vessels of normotensive (NORM) and PRE placentas at term.

METHODS

Placental tissue was obtained from 6 preeclamptic and 8 normotensive women. Gestational age ranged from 38-42 weeks. Deliveries were either vaginal (vag, n = 10) or c-section (c-sec, n = 4). Tissue samples were analyzed for PDGF-AA by immunocytochemistry.

RESULTS

PDGF-AA and the alpha receptor were present in both NORM and PRE placentas. Immunoreactive staining revealed PDGF-AA and its receptor in the intimal/endothelial layer of fetal vessels and the trophoblastic layer. Staining intensity was greater in preeclamptic tissue when obliterative endarteritis was present.

CONCLUSIONS

In pre-eclampsia, PDGF-AA may play a role in the restructuring of the fetoplacental vasculature, in particular when there is inflammation of the vascular intimal layer, as found in obliterative endarteritis. Increased staining in the trophoblast layer in patients with obliterative endarteritis also may be indicative of more widespread damage throughout the placenta itself, and PDGF-AA may play a significant role in the repair of this damage.

Characterization of transgenic mice with targeted disruption of the catalytic domain of the double-stranded RNA-dependent protein kinase, PKR

The interferon-inducible, double-stranded RNA-dependent protein kinase PKR has been implicated in anti-viral, anti-tumor, and apoptotic responses. Others have attempted to examine the requirement of PKR in these roles by targeted disruption at the amino terminal-encoding region of the Pkr gene. By using a strategy that aims at disruption of the catalytic domain of PKR, we have generated mice that are genetically ablated for functional PKR. Similar to the other mouse model of Pkr disruption, we have observed no consequences of loss of PKR on tumor suppression. Anti-viral response to influenza and vaccinia also appeared to be normal in mice and in cells lacking PKR. Cytokine signaling in the type I interferon pathway is normal but may be compromised in the erythropoietin pathway in erythroid bone marrow precursors. Contrary to the amino-terminal targeted Pkr mouse, tumor necrosis factor alpha-induced apoptosis and the anti-viral apoptosis response to influenza is not impaired in catalytic domain-targeted Pkr-null cells. The observation of intact eukaryotic initiation factor-2alpha phosphorylation in these Pkr-null cells provides proof of rescue by another eukaryotic initiation factor-2alpha kinase(s).

The medical dictionary for regulatory activities (MedDRA)

The International Conference on Harmonisation has agreed upon the structure and content of the Medical Dictionary for Regulatory Activities (MedDRA) version 2.0 which should become available in the early part of 1999. This medical terminology is intended for use in the pre- and postmarketing phases of the medicines regulatory process, covering diagnoses, symptoms and signs, adverse drug reactions and therapeutic indications, the names and qualitative results of investigations, surgical and medical procedures, and medical/social history. It can be used for recording adverse events and medical history in clinical trials, in the analysis and tabulations of data from these trials and in the expedited submission of safety data to government regulatory authorities, as well as in constructing standard product information and documentation for applications for marketing authorisation. After licensing of a medicine, it may be used in pharmacovigilance and is expected to be the preferred terminology for international electronic regulatory communication. MedDRA is a hierarchical terminology with 5 levels and is multiaxial: terms may exist in more than 1 vertical axis, providing specificity of terms for data entry and flexibility in data retrieval. Terms in MedDRA were derived from several sources including the WHO's adverse reaction terminology (WHO-ART), Coding Symbols for a Thesaurus of Adverse Reaction Terms (COSTART), International Classification of Diseases (ICD) 9 and ICD9-CM. It will be maintained, further developed and distributed by a Maintenance Support Services Organisation (MSSO). It is anticipated that using MedDRA will improve the quality of data captured on databases, support effective analysis by providing clinically relevant groupings of terms and facilitate electronic communication of data, although as a new tool, users will need to invest time in gaining expertise in its use.

The reovirus protein mu2, encoded by the M1 gene, is an RNA-binding protein

The reovirus M1, L1, and L2 genes encode proteins found at each vertex of the viral core and are likely to form a structural unit involved in RNA synthesis. Genetic analyses have implicated the M1 gene in viral RNA synthesis and core nucleoside triphosphatase activity, but there have been no direct biochemical studies of mu2 function. Here, we expressed mu2 in vitro and assessed its RNA-binding activity. The expressed mu2 binds both poly(I-C)- and poly(U)-Sepharose, and binding activity is greater in Mn2+ than in Mg2+. Heterologous RNA competes for mu2 binding to reovirus RNA transcripts as effectively as homologous reovirus RNA does, providing no evidence for sequence-specific RNA binding by mu2. Protein mu2 is now the sixth reovirus protein demonstrated to have RNA-binding activity.

Interference by a non-defective variant of influenza A virus is due to enhanced RNA synthesis and assembly

Mouse-adapted influenza A virus, FM-MA, interferes with the replication of wild-type strains on co-infection. The interference phenotype was previously mapped to FM-MA segment 2 encoding a mutant PB1 protein, the catalytic component of the RNA polymerase complex. To identify the point at which FM-MA interferes with wild-type A/HK/1/68 (HK), the relative levels of transcription and genome replication of the PB1, NP and M1 genes were determined for FM-MA and HK viruses in co-infected cells using RT-PCR. All stages of HK macromolecular synthesis (primary and secondary transcription, genomic RNA, complementary RNA and protein synthesis) were suppressed relative to FM-MA. Infection with HK virus alone resulted in the accumulation of similar or greater amounts of RNA at late times post-infection relative to FM-MA thus indicating that the presence of FM-MA specifically compromised HK transcription and replication in co-infected cells. However early in infection FM-MA was ten times more active in mRNA transcription than HK or its parental strain FM. FM-MA's ability to interfere was primarily due to an increased capacity for primary transcription. FM-MA genomes were also selectively assembled into progeny virus from cells co-infected with HK and FM-MA, a step which was distinct from the capacity for enhanced RNA synthesis. This suggests that interference of HK growth by FM-MA in mixed infections results from two distinct events: a preferential synthesis of FM-MA-specific macromolecules which is then augmented by a preferential assembly of FM-MA genomes.

Genetic studies on a mumps vaccine strain associated with meningitis

Vaccination with mumps measles and rubella (MMR) vaccine containing the live attenuated mumps strain, Urabe AM9, is associated with an increased incidence of meningitis. The isolation of mumps virus from CSF and subsequent identification as Urabe AM9-like by sequence analysis confirmed the causative role of Urabe AM9 vaccine in meningitis. To assess the role of genetic reversion in vaccine failure, sequence comparisons were made between several genes of Urabe AM9 vaccine and post-vaccination meningitis mumps isolates. An amino acid substitution in the Urabe AM9 HN gene Lys335Glu was not detected in the post-vaccination meningitis isolates suggesting that reversion to wild type sequence was associated with vaccine failure. However, further analysis showed that the vaccine was a mixture of viruses that differed at aa 335 of HN, possessing either the wild type Lys335 or the mutant Glu335, whereas the clinical isolates were homogeneous and possessed the wild type Lys335. Passage of the Urabe AM9 vaccine preparations in Vero cells resulted in the amplification of the Glu335 virus, however the post-vaccination meningitis isolates (Lys335) grew better in Vero cells than Urabe AM9 vaccine. A virus isolate, similar to the post-vaccination isolates was obtained from the vaccine suggesting that the strain responsible for vaccine failure was a pre-existing component of the vaccine and was not necessarily the result of reversion. The Urabe AM9 vaccine is a heterogeneous mixture of genotypes that differ in virulence with the HN Glu335 viruses being attenuated and at least a subset of the HN Lys335 viruses that are associated with disease. The Glu335 mutation may be among a class of attenuating mutations identified in several neurotropic viruses that involve charged amino acids in neutralising epitopes of receptor binding proteins. Copyright 1998 John Wiley & Sons, Ltd.

Expression of platelet-derived growth factor-A mRNA in human placenta: effect of magnesium infusion in pre-eclampsia

The expression of platelet-derived growth factor-A (PDGF-A) mRNA was examined in the cotyledons of normal human placentae and those from patients with pre-eclampsia. These patients exhibited pre-delivery blood pressure of 154+/-4/99+/-4 mmHg (mean+/-SEM) and met the criteria established for pre-eclampsia. During labour they received MgSO4 infusion for various time intervals (4-25 h). The PDGF-A message was quantitated to beta-actin by the solution hybridization nuclease protection assay. Since the two groups differed in two parameters (pre-eclampsia and MgSO4 treatment), the direct comparison was not feasible. An analysis of covariance revealed a significant difference in the message between the pre-eclamptic and control groups (P<0.01); the gestational age was not a significant covariate for either group but the time on MgSO4 in pre-eclampsia group was significant (P<0.002). A linear regression analysis of PDGF-A mRNA values for the pre-eclamptic group showed a time-dependent downregulation of the message by MgSO4 (P<0.01, r=- 0.796). These results show a uniform expression of PDGF-A mRNA in cotyledons of normal human placenta between 35 and 40 weeks of gestation. Furthermore, MgSO4 has an inhibitory effect on the expression of this message which may have aside from its anticonvulsive action beneficial effect on the function of pre-eclamptic placenta.

Arteriovenous extracorporeal carbon dioxide removal: a mathematical model and experimental evaluation

To explore the feasibility and operating limits of arteriovenous extracorporeal CO2 removal (AVCO2R) for support of acute respiratory failure, the authors developed a mathematical model to simulate (AVCO2R), evaluate the effects of several parameters used in its application, and predict the feasibility and necessary conditions for total CO2 removal. The mathematical model incorporated compartments representing blood, pulmonary alveoli, pulmonary capillaries, peripheral tissues and capillaries, and an extracorporeal gas exchange device. The model was validated against an animal model of extracorporeal CO2 removal. This model consisted of anesthetized and mechanically ventilated piglets. An extracorporeal CO2 removal device was placed by cannulation of a femoral artery and vein. Dynamic and steady state measurements of CO2 transfer were made and compared with simulations using the mathematical model. There was good agreement between experimental and simulated data, validating the mathematical model under a variety of conditions. The mathematical model was used to determine operating parameters for total CO2 removal. Relationships between extracorporeal blood flow, device diffusing capacity, and device gas sweep flow were established for CO2 removal at various levels of CO2 production. These simulations indicate that it is possible to achieve total CO2 removal using an extracorporeal shunt fraction of 10%-15% of cardiac output, a device diffusing capacity of 0.5 ml x min(-1) x torr(-1) (kg body weight)(-1), and a gas:blood flow of 5 or greater.

Selective use of vancomycin to prevent coagulase-negative staphylococcal nosocomial bacteremia in high risk very low birth weight infants

OBJECTIVE

To determine whether vancomycin added to parental nutrition (PN) fluids could prevent nosocomial infections in very low birth weight newborns and which infants would benefit most from prophylaxis.

DESIGN

Double blind, randomized controlled study.

SETTING AND STUDY POPULATION

Very low birth weight infants receiving PN in a tertiary neonatal intensive care unit.

METHODS

Thirty-eight infants with and without central vascular catheters were randomized to receive no medication or 25 microg/ml vancomycin added to PN for the duration of the infant's PN requirements.

RESULTS

The addition of 25 microg/ml vancomycin to PN prevented bacteremia in very low birth weight infants receiving PN. There was a significant reduction in the number of coagulase-negative staphylococcal (CONS) bacteremias (defined as isolation of the same organism from two positive blood cultures) during PN (5 vs. 0; P = 0.037) as well as the total number of bacteremias and fungemias (9 vs. 1; P = 0.036). The total number of hospital days (108 +/- 13 vs. 76 +/- 6; P = 0.039) were reduced in infants receiving vancomycin. Infants with birth weights of < 1000 g who received corticosteroids for treatment of chronic lung disease benefitted most from treatment. No vancomycin-resistant strains of CONS or enterococci were detected during the study period.

CONCLUSIONS

Prophylactic treatment with vancomycin effectively prevented CONS bacteremia under the conditions of the study. Its use was most effective in infants with birth weights of <1000 g.

Mutations in the hemagglutinin and matrix genes of a virulent influenza virus variant, A/FM/1/47-MA, control different stages in pathogenesis

The mouse adapted strain of influenza A/FM/1/47 virus, FM-MA, has increased virulence due to mutations in HA, M1 and at least one other, unmapped, genome segment. Genetic reassortants that differ due to the HA or M1 mutations were used to define the role of these mutations in pathogenesis. Pathological changes in lungs of infected mice were assessed by hematoxylin phloxine saffron (HPS) staining, and viral infection was measured by fluorescent antibody staining of thin sections and flow cytometry of lung parenchymal cells. HA played a role in bronchiolar pathology by increasing necrosis of bronchiolar epithelium, peribronchiolar lymphocytes, and airway obstruction. The HA mutation was shown to be responsible for a 0.2 unit decreased in the pH optimum of fusion and controlled resistance to alpha and beta inhibitors of hemagglutination. Both these changes in biology may confer a replicative advantage in bronchioles seen in the first day of infection. Thus the HA mutation may have conferred a survival advantage in the extracellular lung environment. The M1 mutation resulted in improved growth in the lung and cultured cells and was associated with increases in recruitment of macrophages, spread of infection into the alveoli of the lung and interstitial pneumonia. Sequence analysis indicated that the unmapped mutation in the control of FM-MA virulence is either the K482-->R substitution in the PB2 protein or the D538-->G substitution in the PB1 protein. One or other of these mutations results in a growth advantage in infected lung but not in cultured cells as well as a further increased recruitment and infection of macrophages in the lung. Infection with virulent strains of influenza that induced increases in macrophage recruitment caused hypothermia in the mouse.

The Urabe AM9 mumps vaccine is a mixture of viruses differing at amino acid 335 of the hemagglutinin-neuraminidase gene with one form associated with disease

The reason for the high incidence of vaccine-associated meningitis due to the Urabe AM9 vaccine was assessed by comparing the nucleotide (nt) sequence of the hemagglutinin-neuraminidase (HN) gene from vaccine virus to those of viruses isolated from persons with postvaccination meningitis. A G1081--> A nt substitution that was predicted to result in a Glu335--> Lys reversion in the HN protein was detected between Urabe AM9 (G) and postvaccine meningitis mumps virus isolates (A). Further analysis showed that the Urabe AM9 vaccine was a mixture of viruses with wild type (A) and variant (G) nt at position 1081. Urabe AM9 vaccinees who developed meningitis or parotitis possessed predominantly A (98%-100%) at nt 1081, indicating strong selection of the wild type (A) form relative to the variant (G) form. Mumps virus homogeneous for the variant Glu335 form of the HN gene may be safer than the original Urabe AM9 vaccine.

Thyroglossal duct cyst causing airway obstruction in an adult

Thyroglossal duct cysts, though not uncommon, rarely present with evidence of laryngeal compromise. The case presented is one of the very few cases with documented laryngeal invasion reported in the English language. Of clinical significance is the patient's presentation with laryngeal symptoms of choking and dysphonia in the presence of a small anterior cervical mass. While the thyroglossal duct cyst usually presents as an asymptomatic anterior neck mass, this case illustrates the importance of considering a thyroglossal duct cyst in any patient with airway compromise in the absence of a neck mass.