All enveloped viruses enter cells by fusing their envelope with a target cell membrane while avoiding premature fusion with membranes of the producer cell-the latter being particularly important for ...viruses that bud at internal membranes. Flaviviruses bud in the endoplasmic reticulum, are transported through the TGN to reach the external milieu, and enter other cells via receptor-mediated endocytosis. The trigger for membrane fusion is the acidic environment of early endosomes, which has a similar pH to the TGN of the producer cell. The viral particles therefore become activated to react to mildly acidic pH only after their release into the neutral pH extracellular environment. Our study shows that for yellow fever virus (YFV), the mechanism of activation involves actively knocking out the fusion brake (protein pr) through a localized conformational change of the envelope protein upon exposure to the neutral pH external environment. Our study has important implications for understanding the molecular mechanism of flavivirus fusion activation in general and points to an alternative way of interfering with this process as an antiviral treatment.
Rheumatoid factors (RF) are autoantibodies that recognize epitopes in the Fc region of immunoglobulin (Ig) G and that correlate with the clinical severity of rheumatoid arthritis (RA). Here we report ...the X-ray crystallographic structure, at 3 Å resolution, of a complex between the Fc region of human IgG1 and the Fab fragment of a monoclonal IgM RF (RF61), derived from an RA patient and with a relatively high affinity for IgG Fc. In the complex, two Fab fragments bind to each Fc at epitopes close to the C terminus, and each epitope comprises residues from both Cγ3 domains. A central role in the unusually hydrophilic epitope is played by the side-chain of Arg355, accounting for the subclass specificity of RF61, which recognizes IgG1,−
2, and −
3 in preference to IgG4, in which the corresponding residue is Gln355. Compared with a previously determined complex of a lower affinity RF (RF-AN) bound to IgG4 Fc, in which only residues at the very edge of the antibody combining site were involved in binding, the epitope bound by RF61 is centered in classic fashion on the axis of the V
H:V
L β-barrel. The complementarity determining region-H3 loop plays a key role, forming a pocket in which Arg355 is bound by two salt-bridges. The antibody contacts also involve two somatically mutated V
H residues, reinforcing the suggestion of a process of antigen-driven maturation and selection for IgG Fc during the generation of this RF autoantibody.
Background: Many persons with multiple sclerosis (PwMS) report increased fatigue in the afternoon and evening compared with the morning. It is commonly accepted that physical capacity also decreases ...as time of day progresses, potentially influencing the outcomes of testing.
Objective: The objective of this article was to determine whether self-reported fatigue level and walking capacity are influenced by time of day in PwMS.
Methods: A total of 102 PwMS from 8 centers in 5 countries, with a diverse level of ambulatory dysfunction (Expanded Disability Status Scale EDSS <6.5), participated. Patients performed walking capacity tests and reported fatigue level at three different time points (morning, noon, afternoon) during 1 day. Walking capacity was measured with the 6-Minute Walk Test (6MWT) and the 10-m walk test performed at usual and fastest speed. Self-reported fatigue was measured by the Rochester Fatigue Diary (RFD). Subgroups with mild (EDSS 1.5–4.0, n = 53) and moderate (EDSS 4.5–6.5, n = 49) ambulatory dysfunction were formed, as changes during the day were hypothesized to depend on disability status.
Results: Subgroups had different degree of ambulatory dysfunction (p < 0.001) but reported similar fatigue levels. Although RFD scores were affected by time of day with significant differences between morning and noon/afternoon (p < 0.0001), no changes in walking capacity were found in any subgroup. Additional analyses on subgroups distinguished by diurnal change in self-reported fatigue failed to reveal analogous changes in walking capacity.
Conclusions: Testing of walking capacity is unaffected by time of day, despite changes in subjective fatigue.
Background The restrictive emphasis on ambulation and the limited sensitivity to changes figure among the shortcomings of the Expanded Disability Status Scale (EDSS). The MS Functional Composite ...(MSFC) proposed as an alternative, does not assess the hands separately, depends on the stratification of a reference population and the clinical significance of the Z -score change is poorly defined. Objectives Hence the need for an assessment tool based on the motor components of the MSFC that would consider hand function separately and that could be expressed using a clearly defined, clinically relevant interval scoring system. Methods The Short and Graphic Ability Score (SaGAS 20/10) is composed by 3 measures: the 25 feet timed walk at fast speed (T25FW) and the nine-hole peg test (9-HPT) of each hand separately. The timed performances ( t ) of these 3 measures expressed as a logarithmic function of time in three (sS) subscores that are constructed in such a way that any interval of 1.0 unit corresponds to a change of 20%, considered as clinically meaningful. (T25FWsS) T25FW subscore = 20–11.474 x log (4/ t ); a walking time of 4 s corresponding to a maximum T25FWsS of 20. (9HPTsS) 9HPT subscore = 10–11.474 x log (20/ t ); a 9HPT of 20 s corresponding to a maximum NHPTsS of 10. The SaGAS 20/10 is computed: (T25FWsS + NHPTsS right hand + NHPTsS left hand)/2. The 3 subscores can be displayed graphically as a Vitruvian Man on an IPhone app. 148 consecutive patients (mean age 56.5; Mean EDSS 6.1 ± 1.1) with definitive MS were assessed at the beginning and at the end of their rehabilitation stay. Results The SaGAS 20/10 at admission in our population was 11.6 (±2.5). Range 0.0–19.4. The correlation coefficients between SaGAS 20/10 and the EDSS ( r = −0.62) and the Rivermead Mobility Index ( r = 0.82) were all statistically significant ( p < 0.001). The SaGAS 20/10 was more sensitive than the EDSS for the clinically relevant changes (>1 point on SaGAS 20/10) occurring during the rehabilitation stay (32.3% vs. 8.1%; p < 0.001). Conclusions SaGAS 20/10 is a simple, valid and sensitive IPhone app that appears as an alternative to the MSFC and as a most welcome complement to the EDSS for the moderately disabled patients where the gold standard fails to assess the patients comprehensively.
Introduction Clinical trials indicate that disease-modifying therapies (DMT) are effective in reducing disease activity and may slow disease progression ( Freedman, 2011 ). Patients judge gait and ...visual functions as the most valuable ( Heesen et al., 2008 ). The present work explored the impact of patient’s mobility, especially difficulties in walking, as a factor influencing quality of life (QoL) from the perspective of physicians (HCPs). Methods Between March and July 2011 a survey was conducted amongst 40 Swiss HCPs. The objective was to gain insight on symptoms most frequently reported, impact of walking impairment on QoL, assessment tools, treatment options used, follow-up and monitoring over time. Results Walking impairment was considered important/very important by 98% HCPs. Regarding the type of walking impairment, the ‘lack of coordination/balance’ was reported most frequently and 14 times as 1st intervention. The impact of walking impairment on the ability to work was considered important/very important by 83% of HCPs, on social contacts by 75% and on family life by 73%. Walking impairment was reported through HCPs observation in 36 cases and through asking by HCP in 24 cases but primary reporting by the patient in 19 cases. The most frequently used tool to assess walking impairment was EDSS reported by 93% of HCPs. Physiotherapy was the most frequent help for walking impairment and was reported 38 times, in 53% as 1st priority. The involvement of physiotherapist was considered important/very important by 78% of HCPs. New treatment options were considered to be important/very important by 83% of HCPs. Forty three percentage of HCPs were not aware of new drugs for patients with walking impairment. Conclusions The majority of Swiss HCPs have an awareness of walking impairment – most often reported as ‘lack of coordination/balance’ – as a primary concern. It impacts on the ability to work, affects social contacts and family life and consequently QoL. However, as patients raised this issue in nearly 50% of the cases, assessing walking impairment on a systematic basis does not occur in clinical practice. Walking impairment was assessed with EDSS, which is not easily performed. As drugs for patients with walking impairment are in development, it raises the need for tests such as Timed 25-Foot Walk ( Coleman et al., 2012 ) in clinical practice especially as it is validated and simple to apply.
Understanding direct salt effects on protein crystal polymorphism is addressed by comparing different crystal forms (triclinic, monoclinic, tetragonal and orthorhombic) for hen, turkey, bob white ...quail and human lysozymes. Four new structures of hen egg‐white lysozyme are reported: crystals grown in the presence of NapTS diffracted to 1.85 Å, of NaI to 1.6 Å, of NaNO3 to 1.45 Å and of KSCN to 1.63 Å. These new structures are compared with previously published structures in order to draw a mapping of the surface of different lysozymes interacting with monovalent anions, such as nitrate, chloride, iodide, bromide and thiocyanate. An analysis of the structural sites of these anions in the various lysozyme structures is presented. This study shows common anion sites whatever the crystal form and the chemical nature of anions, while others seem specific to a given geometry and a particular charge environment induced by the crystal packing.
Background & Aims:
Eradication of
Helicobacter pylori infections in humans results in the healing of gastritis and gastric ulcers. This study used a mouse model to test whether oral vaccination can ...cure
Helicobacter infection and gastritis.
Methods:
Mice were infected with
Helicobacter felis. Three weeks after infection, the mice were orally immunized with
H. pylori urease B subunit. Control mice were simultaneously infected but sham immunized.
Results:
Three to 8 weeks after oral immunization of
H. felis—infected mice with recombinant
H. pylori urease B subunit, the infection cleared and there was no evidence of gastritis. Vaccinated mice remained protected against two consecutive
H. felis challenges.
Conclusions:
These results show that the lack of natural immunity against
Helicobacter can be overcome by oral immunization and that vaccination offers a novel therapeutic approach to
Helicobacter-induced gastritis.
On entering the host cell the rotavirus virion loses its outer shell to become a double-layered particle (DLP). The DLP then transcribes the 11 segments of its dsRNA genome using its own ...transcriptase complex, and the mature mRNA emerges along the 5-fold axis. In order to better understand the transcription mechanism and the role of VP6 in transcription we have studied three monoclonal antibodies against VP6: RV-238 which inhibits the transcriptase activity of the DLP; and RV-133 and RV-138 which have no effect on transcription. The structures obtained by cryo-electron microscopy of the DLP/Fab complexes and by X-ray crystallography of the VP6 trimer and the VP6/Fab-238 complex have been combined to give pseudo-atomic structures. Steric hindrance between the Fabs results in limited Fab occupancy. In particular, there are on average only three of a possible five Fabs-238 which point towards the 5-fold axis. Thus, Fabs-238 are not in a position to block the exiting mRNA, nor is there any visible conformational change in VP6 on antibody binding at a resolution of 23 Å. However, the epitope of the inhibiting antibody involves two VP6 monomers, whereas, those of the non-inhibiting antibodies have an epitope on only one VP6. Thus, the inhibition of transcription may be a result of inhibition of a possible change in the VP6 conformation associated with the transcription of mRNA.
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