Receptor Density-Dependent Motility of Influenza Virus Particles on Surface Gradients

Influenza viruses can move across the surface of host cells while interacting with their glycocalyx. This motility may assist in finding or forming locations for cell entry and thereby promote cellular uptake. Because the binding to and cleavage of cell surface receptors forms the driving force for the process, the surface-bound motility of influenza is expected to be dependent on the receptor density. Surface gradients with gradually varying receptor densities are thus a valuable tool to study binding and motility processes of influenza and can function as a mimic for local receptor density variations at the glycocalyx that may steer the directionality of a virus particle in finding the proper site of uptake. We have tracked individual influenza virus particles moving over surfaces with receptor density gradients. We analyzed the extracted virus tracks first at a general level to verify neuraminidase activity and subsequently with increasing detail to quantify the receptor density-dependent behavior on the level of individual virus particles. While a directional bias was not observed, most likely due to limitations of the steepness of the surface gradient, the surface mobility and the probability of sticking were found to be significantly dependent on receptor density. A combination of high surface mobility and high dissociation probability of influenza was observed at low receptor densities, while the opposite occurred at higher receptor densities. These properties result in an effective mechanism for finding high-receptor density patches, which are believed to be a key feature of potential locations for cell entry

Hierarchical Multivalent Effects Control Influenza Host Specificity

Understanding how emerging influenza viruses recognize host cells is critical in evaluating their zoonotic potential, pathogenicity, and transmissibility between humans. The surface of the influenza virus is covered with hemagglutinin (HA) proteins that can form multiple interactions with sialic acid-terminated glycans on the host cell surface. This multivalent binding affects the selectivity of the virus in ways that cannot be predicted from the individual receptor-ligand interactions alone. Here, we show that the intrinsic structural and energetic differences between the interactions of avian- or human-type receptors with influenza HA translate from individual site affinity and orientation through receptor length and density on the surface into virus avidity and specificity. We introduce a method to measure virus avidity using receptor density gradients. We found that influenza viruses attached stably to a surface at receptor densities that correspond to a minimum number of approximately 8 HA-glycan interactions, but more interactions were required if the receptors were short and human-type. Thus, the avidity and specificity of influenza viruses for a host cell depend not on the sialic acid linkage alone but on a combination of linkage and the length and density of receptors on the cell surface. Our findings suggest that threshold receptor densities play a key role in virus tropism, which is a predicting factor for both their virulence and zoonotic potential.Fil: Overeem, Nico J.. University of Twente; Países BajosFil: Hamming, P. H. Erik. University of Twente; Países BajosFil: Grant, Oliver C.. University of Georgia; Estados UnidosFil: Di Iorio, Daniele. University of Twente; Países BajosFil: Tieke, Malte. Utrecht University; Países BajosFil: Bertolino, María Candelaria. University of Twente; Países Bajos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Li, Zeshi. Utrecht University; Países BajosFil: Vos, Gaël. Utrecht University; Países BajosFil: de Vries, Robert P.. Utrecht University; Países BajosFil: Woods, Robert J.. University of Georgia; Estados UnidosFil: Tito, Nicholas B.. Electric Ant Laboratory; Países BajosFil: Boons, Geert-Jan P. H.. Utrecht University; Países BajosFil: van der Vries, Erhard. Utrecht University; Países BajosFil: Huskens, Jurriaan. University of Twente; Países Bajo

Receptor Density-Dependent Motility of Influenza Virus Particles on Surface Gradients

Influenza viruses can move across the surface of host cells while interacting with their glycocalyx. This motility may assist in finding or forming locations for cell entry and thereby promote cellular uptake. Because the binding to and cleavage of cell surface receptors forms the driving force for the process, the surface-bound motility of influenza is expected to be dependent on the receptor density. Surface gradients with gradually varying receptor densities are thus a valuable tool to study binding and motility processes of influenza and can function as a mimic for local receptor density variations at the glycocalyx that may steer the directionality of a virus particle in finding the proper site of uptake. We have tracked individual influenza virus particles moving over surfaces with receptor density gradients. We analyzed the extracted virus tracks first at a general level to verify neuraminidase activity and subsequently with increasing detail to quantify the receptor density-dependent behavior on the level of individual virus particles. While a directional bias was not observed, most likely due to limitations of the steepness of the surface gradient, the surface mobility and the probability of sticking were found to be significantly dependent on receptor density. A combination of high surface mobility and high dissociation probability of influenza was observed at low receptor densities, while the opposite occurred at higher receptor densities. These properties result in an effective mechanism for finding high-receptor density patches, which are believed to be a key feature of potential locations for cell entry

Genetic fine mapping and genomic annotation defines causal mechanisms at type 2 diabetes susceptibility loci.

We performed fine mapping of 39 established type 2 diabetes (T2D) loci in 27,206 cases and 57,574 controls of European ancestry. We identified 49 distinct association signals at these loci, including five mapping in or near KCNQ1. 'Credible sets' of the variants most likely to drive each distinct signal mapped predominantly to noncoding sequence, implying that association with T2D is mediated through gene regulation. Credible set variants were enriched for overlap with FOXA2 chromatin immunoprecipitation binding sites in human islet and liver cells, including at MTNR1B, where fine mapping implicated rs10830963 as driving T2D association. We confirmed that the T2D risk allele for this SNP increases FOXA2-bound enhancer activity in islet- and liver-derived cells. We observed allele-specific differences in NEUROD1 binding in islet-derived cells, consistent with evidence that the T2D risk allele increases islet MTNR1B expression. Our study demonstrates how integration of genetic and genomic information can define molecular mechanisms through which variants underlying association signals exert their effects on disease

Multivalent Affinity Profiling: Direct Visualization of the Superselective Binding of Influenza Viruses

The influenza A virus (IAV) interacts with the glycocalyx of host cells through its surface proteins hemagglutinin (HA) and neuraminidase (NA). Quantitative biophysical measurements of these interactions may help to understand these interactions at the molecular level with the long-Term aim to predict influenza infectivity and answer other biological questions. We developed a method, called multivalent affinity profiling (MAP), to measure virus binding profiles on receptor density gradients to determine the threshold receptor density, which is a quantitative measure of virus avidity toward a receptor. Here, we show that imaging of IAVs on receptor density gradients allows the direct visualization and efficient assessment of their superselective binding. We show how the multivalent binding of IAVs can be quantitatively assessed using MAP if the receptor density gradients are prepared around the threshold receptor density without crowding at the higher densities. The threshold receptor density increases strongly with increasing flow rate, showing that the superselective binding of IAV is influenced by shear force. This method of visualization and quantitative assessment of superselective binding allows not only comparative studies of IAV-receptor interactions, but also more fundamental studies of how superselectivity arises and is influenced by experimental conditions

Impact of combat events on first responders : Experiences of the armed conflict in Uruzgan, Afghanistan

Introduction Care for battle casualties demands special skills from medics, nurses, and tactical commanders. To date, no inventory has been performed evaluating the first responders (medics, nurses and tactical commanders) around battle casualties. Method This observational cohort study was conducted amongst the first responders (n = 195) who were deployed to Southern Afghanistan (2009-2010) in three Marine companies. The survey focused on four main topics: (1) participants general background, (2) exposure to combat (casualty) situations, (3) self-perceived quality of care (1 [low]-10 [high]) in the pre-hospital phase, and (4) the effects of combat stressors on professional skills and social environment using the Post Deployment Reintegration Scale (PDRS) and the Impact of Event Scale-Revised (IES-R). Results 71% of the eligible Dutch tactical commanders, medics, and nurses participated in this survey. Most (14/16) medics and nurses scored their pre-deployment training as sufficient The overall self-perceived quality of care score was above average (7.8). Most (80%) of the participants were exposed to battle casualties. There were no significant differences regarding rank, gender, age and military task using the impact of event scale and PDRS, except for a worse score on the work negative, family positive and personal positive subscales (p <0.05) in the PDRS for the first responders in comparison to the armed forces norm score. Conclusion The quality of care in the pre-hospital phase was considered adequate, symptoms of post-traumatic stress in this group was low. Active involvement of co-combatants and the social support network are essential in adaption after exposure to combat events. Further research is necessary to identity predisposing preventable high stress factors, and to compose a "waterproof" aftercare programme

Long-term impact of battle injuries; Five-year follow-up of injured dutch servicemen in afghanistan 2006-2010

Objectives Units deployed to armed conflicts are at high risk for exposure to combat events. Many battle casualties (BCs) have been reported in the recent deployment to Afghanistan. The longterm impact of these combat injuries, at their five-year end point, is currently unknown. To date, no systematic inventory has been performed of an identified group of BCs in comparison to non-injured service members from the same operational theatre. Design Observational cross-sectional cohort study. Setting Open online survey among Dutch BCs that deployed to Afghanistan (2006–2010). Participants The Dutch BCs (n = 62) were compared to two control groups of non-injured combat groups (battle exposed [n = 53], and non-battle exposed [n = 73]). Main Outcome Measures Participants rated their impact of trauma exposure (Impact of Events [IES]), post deployment reintegration (Post Deployment Reintegration Scale [PDRS]), general symptoms of distress (Symptom Checklist 90 [SCL-90]), as well as their current perceived quality of life (EuroQol-6D [EQ-6D]). Also cost effectiveness (Short From health survey [SF-36]) and care consumption were assessed (Trimbos/iMTA questionnaire). Results Over 90% of BCs were still in active duty. The mean scores of all questionnaires (IES, EQ-6D, SF-36, and SCL-90) of the BC group were significantly higher than in the control groups (p<0.05). The PDRS showed a significantly lower (p<0.05) outcome in the negative subscales. The mean consumption of care was triple that of both control groups. A lower score on quality of life was related to higher levels of distress and impact of trauma exposure. Conclusions This study showed a clear long-term impact on a wide range of scales that contributes to a reduced quality of life in a group of BCs. Low perceived cost effectiveness matched with high consumption of care in the BC group in comparison to the control groups. These results warrant continuous monitoring of BCs

Scores of IES, PDRS, SCL-90, EQ-6D and TIC-P per subgroup.

<p>BC indicates battle casualty</p><p>CG1: control group 1</p><p>CG2: control group 2</p><p>SD: standard deviation</p><p>N = numberɸ significant difference (p<0.05) using the Kruskall Wallis test.</p><p>*Subscales IES</p><p>INT: intrusion; AVO: avoidance</p><p>HAR: hyper arousal.</p><p>**Subscales PDRS</p><p>WP: Work positive</p><p>WN: Work negative</p><p>FP: Family positive</p><p>FN: Family negative</p><p>PP: Personal positive</p><p>PN: Personal negative.</p><p>***Subscales SCL-90</p><p>ANX: anxiety</p><p>AGO: agoraphobia</p><p>DEP: depression</p><p>SOM: somatization</p><p>IN: insufficient thinking and handling</p><p>SEN: distrust and interpersonal sensitivity</p><p>HOS: hostility</p><p>SLE: sleeping disorders</p><p>REST: rest subscale.</p><p>****Subscales SF-36</p><p>PF: Physical functioning</p><p>SF: Social functioning</p><p>RP: Role physical</p><p>RE: Role emotional</p><p>MH: Mental health</p><p>VT: Vitality</p><p>BP: Bodily pain</p><p>GH: General Health.</p><p>***** Costs in euros.</p><p>Scores of IES, PDRS, SCL-90, EQ-6D and TIC-P per subgroup.</p

Schematic overview of mean scores of the IES, SCL-90, EQ-6D and TIC-P per subgroup.

<p>Schematic overview of mean scores of the IES, SCL-90, EQ-6D and TIC-P per subgroup.</p

CONSORT diagram for questionnaire Dutch battle casualties and control group deployed to Southern Afghanistan.

<p>CONSORT diagram for questionnaire Dutch battle casualties and control group deployed to Southern Afghanistan.</p