Virus maturation targets the protein capsid to concerted disassembly and unfolding

Many animal viruses undergo post-assembly proteolytic cleavage that is required for infectivity. The role of maturation cleavage on Flock House virus was evaluated by comparing wild type (wt) and cleavage-defective mutant (D75N) Flock House virus virus-like particles. A concerted dissociation and unfolding of the mature wt particle was observed under treatment by urea, whereas the cleavage-defective mutant dissociated to folded subunits as determined by steady-state and dynamic fluorescence spectroscopy, circular dichroism, and nuclear magnetic resonance. The folded D75N alpha subunit could reassemble into capsids, whereas the yield of reassembly from unfolded cleaved wt subunits was very low. Overall, our results demonstrate that the maturation/cleavage process targets the particle for an "off pathway" disassembly, because dissociation is coupled to unfolding. The increased motions in the cleaved capsid, revealed by fluorescence and NMR, and the concerted nature of dissociation/unfolding may be crucial to make the mature particle infectious.

Rescue of mumps virus from cDNA

A complete DNA copy of the genome of a Jeryl Lynn strain of mumps virus (15,384 nucleotides) was assembled from cDNA fragments such that an exact antigenome RNA could be generated following transcription by T7 RNA polymerase and cleavage by hepatitis delta virus ribozyme. The plasmid containing the genome sequence, together with support plasmids which express mumps virus NP, P, and L proteins under control of the T7 RNA polymerase promoter, were transfected into A549 cells previously infected with recombinant vaccinia virus (MVA-T7) that expressed T7 RNA polymerase. Rescue of infectious virus from the genome cDNA was demonstrated by amplification of mumps virus from transfected-cell cultures and by subsequent consensus sequencing of reverse transcription-PCR products generated from infected-cell RNA to verify the presence of specific nucleotide tags introduced into the genome cDNA clone. The only coding change (position 8502, A to G) in the cDNA clone relative to the consensus sequence of the Jeryl Lynn plaque isolate from which it was derived, resulting in a lysine-to-arginine substitution at amino acid 22 of the L protein, did not prevent rescue of mumps virus, even though an amino acid alignment for the L proteins of paramyxoviruses indicates that lysine is highly conserved at that position. This system may provide the basis of a safe and effective virus vector for the in vivo expression of immunologically and biologically active proteins, peptides, and RNAs.

Structures of virus and virus-like particles

Virus structures continue to be the basis for mechanistic virology and serve as a paradigm for solutions to problems concerning macromolecular assembly and function in general. The use of X-ray crystallography, electron cryomicroscopy and computational and biochemical methods has provided not only details of the structural folds of individual viral components, but also insights into the structural basis of assembly, nucleic acid packaging, particle dynamics and interactions with cellular molecules.

Autoregulation and multiple enhancers control Math1 expression in the developing nervous system

Development of the vertebrate nervous system requires the actions of transcription factors that establish regional domains of gene expression, which results in the generation of diverse neuronal cell types. MATH1, a transcription factor of the bHLH class, is expressed during development of the nervous system in multiple neuronal domains, including the dorsal neural tube, the EGL of the cerebellum and the hair cells of the vestibular and auditory systems. MATH1 is essential for proper development of the granular layer of the cerebellum and the hair cells of the cochlear and vestibular systems, as shown in mice carrying a targeted disruption of Math1. Previously, we showed that 21 kb of sequence flanking the Math1-coding region is sufficient for Math1 expression in transgenic mice. Here we identify two discrete sequences within the 21 kb region that are conserved between mouse and human, and are sufficient for driving a lacZ reporter gene in these domains of Math1 expression in transgenic mice. The two identified enhancers, while dissimilar in sequence, appear to have redundant activities in the different Math1 expression domains except the spinal neural tube. The regulatory mechanisms for each of the diverse Math1 expression domains are tightly linked, as separable regulatory elements for any given domain of Math1 expression were not found, suggesting that a common regulatory mechanism controls these apparently unrelated domains of expression. In addition, we demonstrate a role for autoregulation in controlling the activity of the Math1 enhancer, through an essential E-box consensus binding site.

Influence of three-dimensional structure on the immunogenicity of a peptide expressed on the surface of a plant virus

The influence of peptide structure on immunogenicity has been investigated by constructing a series of cowpea mosaic virus (CPMV) chimaeras expressing the 14 amino acid NIm-1A epitope from human rhinovirus 14 (HRV-14) at different positions on the capsid surface. Biochemical and crystallographic analysis of a CPMV/HRV chimaera expressing the NIm-1A epitope inserted into the betaC'-betaC" loop of the S protein revealed that, although the inserted peptide was free at its C-terminus, it adopted a conformation distinct from that previously found when a similarly cleaved peptide was expressed in the betaB-betaC loop of the S protein. Adjustment of the site of insertion within the betaB-betaC loop resulted in the isolation of a chimaera in which cleavage at the C-terminus of the epitope was much reduced. Crystallographic analysis confirmed that in this case the epitope was presented as a closed loop. Polyclonal antisera raised against the CPMV/ HRV chimaera presenting the NIm-1A epitope as a closed loop had a significantly enhanced ability to bind to intact HRV-14 particles compared with antisera raised against chimaeras presenting the same sequence as peptides with free C-termini. These results demonstrate that the mode of presentation of an epitope on a heterologous carrier can dramatically affect its immunological properties.

Effects of a tendo-Achilles lengthening procedure on muscle function and gait characteristics in a patient with diabetes mellitus

STUDY DESIGN

Case report with repeated measures.

OBJECTIVES

To describe the effects of a tendo-Achilles lengthening (TAL) and total contact casting (TCC) on wound healing, motion, plantar pressure, and function in a patient with diabetes mellitus, peripheral neuropathy, neuropathic ulcer, and limited dorsiflexion range of motion (DFROM).

BACKGROUND

Limited DFROM has been associated with increased forefoot pressures and skin breakdown. A TAL was expected to increase DFROM and reduce forefoot pressures during walking, but the influence on muscle performance and function was unknown.

METHODS AND MEASURES

The patient was a 42-year-old man with a 20-year history of type 1 diabetes (NIDDM) and a recurrent neuropathic plantar ulcer. Outcome measures were DFROM, isokinetic plantar flexor muscle peak torque, in-shoe and barefoot peak plantar pressure, physical performance test (PPT) score, and peak ankle and hip moments during walking obtained from an automated gait analysis. All tests were completed pre-TAL, 8 weeks post-TAL (after immobilization in a TCC), and 7 months post-TAL.

RESULTS

The wound healed in 40 days. The TAL resulted in a sustained increase in DFROM (0 to 18 degrees). Plantar flexor peak torque was reduced by 21% 8 weeks after the TAL compared with the torque before surgery but recovered fully at 7 months. Seven months following TAL, in-shoe forefoot peak plantar pressure was reduced by 55%, barefoot pressure decreased by 14%, PPT score increased by 24%, peak ankle plantar flexor moment remained decreased by 30%, and the peak hip flexor moment increased by 41% during walking.

CONCLUSION

For this patient, a TAL resulted in short-term deficits in peak plantar flexor torque, but a 7-month follow-up showed improvements in ankle DFROM, walking ability, and a decrease in forefoot in-shoe peak plantar pressure.

Posterior tibial tendon dysfunction

Posterior tibial tendon dysfunction is the most common cause of acquired flatfoot deformity in adults. Although this term suggests pathology involving only the posterior tibial tendon, the disorder includes a spectrum of pathologic changes involving associated tendon, ligament, and joint structures of the ankle, hindfoot, and midfoot. Early recognition and treatment is the key to prevention of the debilitating, long-term consequences of this disorder. Conservative care is possible in the earliest stages, whereas surgical reconstruction and eventually arthrodeses become necessary in the latter stages. The purpose of this article is to review the symptoms, physical examination, radiological examination, classification, and treatment of posterior tibial tendon dysfunction.

Maturation dynamics of a viral capsid: visualization of transitional intermediate states

Typical of DNA bacteriophages and herpesviruses, HK97 assembles in two stages: polymerization and maturation. First, capsid protein polymerizes into closed shells; then, these precursors mature into larger, stabler particles. Maturation is initiated by proteolysis, producing a metastable particle primed for expansion-the major structural transition. We induced expansion in vitro by acidic pH and monitored the resulting changes by time-resolved X-ray diffraction and cryo-electron microscopy. The transition, which is not synchronized over the population, proceeds in a series of stochastically triggered subtransitions. Three distinct intermediates were identified, which are comparable to transitional states in protein folding. The intermediates' structures reveal the molecular events occurring during expansion. Integrated into a movie (see Dynamic Visualization below), they show capsid maturation as a dynamic process.

Older rural women and the use of complementary therapies

One hundred seventy-five rural women over the age of 70 participated in a study to assess their use of complementary therapies and practitioners. Data were collected via questionnaires and interviews. Findings suggest that these women used nontraditional health practices to treat a variety of symptoms, as well as to maintain their independence. However, very few of them informed their primary care providers that they used complementary therapies and practitioners. The majority were inadequately informed regarding the efficacy and safety of the therapies.

Structural fingerprinting: subgrouping of comoviruses by structural studies of red clover mottle virus to 2.4-A resolution and comparisons with other comoviruses

Red clover mottle virus (RCMV) is a member of the comoviruses, a group of picornavirus-like plant viruses. The X-ray structure of RCMV strain S has been determined and refined to 2.4 A. The overall structure of RCMV is similar to that of two other comoviruses, Cowpea mosaic virus (CPMV) and Bean pod mottle virus (BPMV). The sequence of the coat proteins of RCMV strain O were modeled into the capsid structure of strain S without causing any distortion, confirming the close resemblance between the two strains. By comparing the RCMV structure with that of other comoviruses, a structural fingerprint at the N terminus of the small subunit was identified which allowed subgrouping of comoviruses into CPMV-like and BPMV-like viruses.

Graded and areal expression patterns of regulatory genes and cadherins in embryonic neocortex independent of thalamocortical input

The differentiation of areas of the mammalian neocortex has been hypothesized to be controlled by intrinsic genetic programs and extrinsic influences such as those mediated by thalamocortical afferents (TCAs). To address the interplay between these intrinsic and extrinsic mechanisms in the process of arealization, we have analyzed the requirement of TCAs in establishing or maintaining graded or areal patterns of gene expression in the developing mouse neocortex. We describe the differential expression of Lhx2, SCIP, and Emx1, representatives of three different classes of transcription factors, and the type II classical cadherins Cad6, Cad8, and Cad11, which are expressed in graded or areal patterns, as well as layer-specific patterns, in the cortical plate. The differential expression of Lhx2, SCIP, Emx1, and Cad8 in the cortical plate is not evident until after TCAs reach the cortex, whereas Cad6 and Cad11 show subtle graded patterns of expression before the arrival of TCAs, which later become stronger. We find that these genes exhibit normal-appearing graded or areal expression patterns in Mash-1 mutant mice that fail to develop a TCA projection. These findings show that TCAs are not required for the establishment or maintenance of the graded and areal expression patterns of these genes and strongly suggest that their regulation is intrinsic to the developing neocortex.

The refined crystal structure of cowpea mosaic virus at 2.8 A resolution

Comoviruses are a group of plant viruses in the picornavirus superfamily. The type member of comoviruses, cowpea mosaic virus (CPMV), was crystallized in the cubic space group I23, a = 317 A and the hexagonal space group P6(1)22, a = 451 A, c = 1038 A. Structures of three closely similar nucleoprotein particles were determined in the cubic form. The roughly 300-A capsid was similar to the picornavirus capsid displaying a pseudo T = 3 (P = 3) surface lattice. The three beta-sandwich domains adopt two orientations, one with the long axis radial and the other two with the long axes tangential in reference to the capsid sphere. T = 3 viruses display one or the other of these two orientations. The CPMV capsid was permeable to cesium ions, leading to a disturbance of the beta-annulus inside a channel-like structure, suggesting an ion channel. The hexagonal crystal form diffracted X rays to 3 A resolution, despite the large unit cell. The large ( approximately 200 A) solvent channels in the lattice allow exchange of CPMV cognate Fab fragments. As an initial step in the structure determination of the CPMV/Fab complex, the P6(1)22 crystal structure was solved by molecular replacement with the CPMV model determined in the cubic cell.

Hindfoot coronal alignment: a modified radiographic method

Accurate clinical evaluation of the alignment of the calcaneus relative to the tibia in the coronal plane is essential in the evaluation and treatment of hindfoot pathologic condition. Previously described radiographic views of the foot and ankle do not demonstrate the true coronal alignment of the calcaneus relative to the tibia. Some of these views impose on the patient an unnatural posture that itself changes hindfoot alignment, whereas other methods distort the coronal alignment by the angle of the x-ray beam. Our purpose was to develop a modified radiographic view and measurement method for determining an angular measurement of hindfoot coronal alignment based on a cadaver study of the radiographic characteristics of the calcaneus and motion analysis of standing subjects. The view was obtained by having the subject stand on a piece of cardboard to create a foot template. The template was then positioned so that each foot was x-rayed perpendicular to the cassette while still maintaining the natural base of support. A method using multiple ellipses was developed to determine more accurately the coronal axis of the posterior calcaneus. A study using cadavers was performed in which radio-opaque markers were placed on multiple bony landmarks on the calcaneus. The tibia was held fixed in a vertical position, and the foot was x-rayed using the above techniques in different degrees of rotation without changing the relation of the calcaneus to the tibia. The radiographs of the modified Cobey and our view were examined to verify which markers were visible at different angles of rotation and how the hindfoot alignment measurements changed with foot rotation. To define further the differences between the views, an analysis of postural stability was conducted while the subjects were standing with the feet in the positions for imaging both the Buck modification of the Cobey view and our hindfoot alignment view. The combined results of the cadaver, radiographic measurement, and postural stability segments of the study reveal that this coronal hindfoot alignment view and measurement method is reproducible, more closely measures "true" coronal hindfoot alignment, and is more clinically applicable because the alignment is measured while the patient is standing with a normal angle and base of stance. The modified radiographic measurement method relies on posterior calcaneal anatomic landmarks, is less affected by rotation of the foot and ankle, and is reproducible between observers.

Urban older adults and the forfeiture of a driver's license

Frequently, it is assumed that urban older adults are not vulnerable to the consequences of forfeiting a driver's license because of the availability of public transportation. Although all of the study participants were involved in accidents prior to forfeiting their driver's licenses, 221 (78%) of them stated they had been safe drivers. The majority of participants indicated they had been given no choice by either their families or the bureaucracy in forfeiting their driver's licenses. Regret, loneliness, and immobility were the results of no longer being allowed to drive.

Self-regulation theory and coping with physical illness

A self-regulation theory of how patients cope with events that occur during physical illness that has received substantial support from research is described. The theory challenges some traditional thinking about providing patients information and patients' emotional responses to threatening health care events. The use of the theory in practice and suggestions for research to further develop the theory are discussed.

RNA-controlled polymorphism in the in vivo assembly of 180-subunit and 120-subunit virions from a single capsid protein

Repeated, specific interactions between capsid protein (CP) subunits direct virus capsid assembly and exemplify regulated protein-protein interactions. The results presented here reveal a striking in vivo switch in CP assembly. Using cryoelectron microscopy, three-dimensional image reconstruction, and molecular modeling, we show that brome mosaic virus (BMV) CP can assemble in vivo two remarkably distinct capsids that selectively package BMV-derived RNAs in the absence of BMV RNA replication: a 180-subunit capsid indistinguishable from virions produced in natural infections and a previously unobserved BMV capsid type with 120 subunits arranged as 60 CP dimers. Each such dimer contains two CPs in distinct, nonequivalent environments, in contrast to the quasi-equivalent CP environments throughout the 180-subunit capsid. This 120-subunit capsid utilizes most of the CP interactions of the 180-subunit capsid plus nonequivalent CP-CP interactions. Thus, the CP of BMV, and perhaps other viruses, can encode CP-CP interactions that are not apparent from mature virions and may function in assembly or disassembly. Shared structural features suggest that the 120- and 180-subunit capsids share assembly steps and that a common pentamer of CP dimers may be an important assembly intermediate. The ability of a single CP to switch between distinct capsids by means of alternate interactions also implies reduced evolutionary barriers between different capsid structures. The in vivo switch between alternate BMV capsids is controlled by the RNA packaged: a natural BMV genomic RNA was packaged in 180-subunit capsids, whereas an engineered mRNA containing only the BMV CP gene was packaged in 120-subunit capsids. RNA features can thus direct the assembly of a ribonucleoprotein complex between alternate structural pathways.

Preferential role for NF-kappa B/Rel signaling in the type 1 but not type 2 T cell-dependent immune response in vivo

T cell function is a critical determinant of immune responses as well as susceptibility to allergic diseases. Activated T cells can differentiate into effectors whose cytokine profile is limited to type 1 (IFN-gamma-dominant) or type 2 (IL-4-, IL-5-dominant) patterns. To investigate mechanisms that connect extracellular stimuli with the regulation of effector T cell function, we have measured immune responses of transgenic mice whose NF-kappa B/Rel signaling pathway is inhibited in T cells. Surprisingly, these mice developed type 2 T cell-dependent responses (IgE and eosinophil recruitment) in a model of allergic pulmonary inflammation. In contrast, type 1 T cell responses were severely impaired, as evidenced by markedly diminished delayed-type hypersensitivity responses, IFN-gamma production, and Ag-specific IgG2a levels. Taken together, these data indicate that inhibition of NF-kappa B can lead to preferential impairment of type 1 as compared with type 2 T cell-dependent responses.

Correct coordination of neuronal differentiation events in ventral forebrain requires the bHLH factor MASH1

MASH1 is a bHLH transcription factor specifically expressed in the developing nervous system that has an essential role in the formation of multiple neuronal lineages in the peripheral and central nervous systems. Here we demonstrate the requirement for MASH1 for normal development of ventral forebrain structures. MASH1 is expressed at high levels in the ventral telencephalon and specific regions within the ventral diencepharon. In the absence of MASH1, tissue morphology, proliferation, and gene expression within these forebrain regions is disrupted. The decreased incorporation of BrdU in the neuro-epithelium and the enlargement of the ventricles demonstrate a reduction in cell proliferation. A loss of anatomically distinct lateral and medial ganglionic eminences, and a disruption of axons traversing this region, indicate abnormalities in cell-type specification. The aberrant expression of Tuj-1, a marker of neuronal differentiation in the neuroepithelium, and Dlx, a marker of regional cell identity, in the ventricular zone in the MASH1 mutant brains suggest coordination of differentiation events is disrupted. In addition, the involvement of MASH1 in lateral inhibition processes that affect the development of these forebrain regions is implicated. Taken together, an essential role for MASH1 in the coordination of events required for correct cell-type specification and timing of differentiation during neural development in ventral forebrain regions is demonstrated.

Prophylaxis with respiratory syncytial virus F-specific humanized monoclonal antibody delays and moderately suppresses the native antibody response but does not impair immunity to late rechallenge

Respiratory syncytial virus (RSV) is the most significant viral cause of lower respiratory tract disease in infants and children. This study tested the hypothesis that a humanized murine monoclonal antibody (MAb) would protect against RSV infection in mice and have minimal suppressive effect upon the immune response because it is directed against a single epitope. A humanized murine MAb (RSHZ19) was tested for both prophylaxis and treatment of RSV infection in BALB/c mice and compared with a polyclonal product. Mice were rechallenged when passively administered antibody was undetectable (day 104). RSHZ19 reduced virus titer and protected against illness when used in prophylaxis and effected rapid virus clearance when used as treatment. Polyclonal antibody was also an effective prophylaxis but required 200 times the dose in total protein. Peak neutralizing antibody responses were delayed and somewhat suppressed in the prophylactically treated groups, but mice were protected against infection on rechallenge. Secondary antibody response to rechallenge in passively immunized mice was equal to that in untreated mice.

Mania in the geriatric patient population: a review of the literature

The diagnosis of mania in the geriatric population is uncommon. However, it comprises significant healthcare utilization and cost requirements, which are expected to increase in the near future with the projected increase in the geriatric population. The authors review literature pertaining to geriatric mania and discuss epidemiology, psychopathology, neuropathology, differential diagnosis, evaluation, treatment, and outcomes. Literature searches were performed by GratefulMed for the years 1960-1997, with secondary- and tertiary-source follow-up. It is clear from this review that geriatric mania is a complex illness with many possible etiologies and treatments. Much more research needs to be conducted in all of the areas reviewed.

The crystal structure of cricket paralysis virus: the first view of a new virus family

Numerous small, RNA-containing insect viruses are currently classified as picornaviruses, or as 'picorna-like', since they superficially resemble the true picornaviruses. Considerable evidence now suggests that several of these viruses are members of a distinct family. We have determined the gene sequence of the capsid proteins and the 2.4 A resolution crystal structure of the cricket paralysis virus. While the genome sequence indicates that the insect picorna-like viruses represent a distinct lineage compared to true picornaviruses, the capsid structure demonstrates that the two groups are related. These viral genomes are, thus, best viewed as composed of exchangeable modules that have recombined.