Coevolution Of Risk Perception, Sexual Behaviour, And Hiv Transmission In An Agent-Based Model

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.jtbi.2013.08.014 © 2013. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Risk perception shapes individual behaviour, and is in turn shaped by the consequences of that behaviour. Here we explore this dynamics in the context of human immunodeficiency virus (HIV) spread. We construct a simplified agent-based model based on a partner selection game, where individuals are paired with others in the population, and through a decision tree, agree on unprotected sex, protected sex, or no sex. An individual's choice is conditioned on their HIV status, their perceived population-level HIV prevalence, and the preferences expressed by the individual with whom they are paired. HIV is transmitted during unprotected sex with a certain probability As expected, in model simulations, the perceived population-level HIV prevalence climbs along with actual HIV prevalence. During this time, HIV individuals increasingly switch from unprotected sex to protected sex, HIV+ individuals continue practicing unprotected sex whenever possible, and unprotected sex between HIV+ and HIV individuals eventually becomes rare. We also find that the perceived population-level HIV prevalence diverges according to HIV status: HIV individuals develop a higher perceived HIV prevalence than HIV+ individuals, although this result is sensitive to how much information is derived from global versus local sources. This research illustrates a potential mechanism by which distinct groups, as defined by their sexual behaviour, HIV status, and risk perceptions, can emerge through coevolution of HIV transmission and risk perception dynamics.CIHR Operating GrantNSERC Discovery Gran

Overloading ion-exchange membranes as a purification step for monoclonal antibodies

The present study examined the overloading of ion-exchange membrane adsorbers, a form of frontal chromatography, as the final purification step in the production of mAbs (monoclonal antibodies) produced from CHO (Chinese-hamster ovary) cells. Preferential binding of impurities over antibody product was exploited using commercially available cation- and anion-exchange membranes. Three different antibody feedstreams previously purified over Protein A and ion-exchange column chromatography were tested. Feedstream conductivity and pH were adjusted to induce product and impurity adsorption. Membranes were then overloaded in a normal flow mode, resulting in retention of impurities and breakthrough of purified antibody. Although some amount of the product also binds to the membranes (usually ≤30 g mAb/l membrane), yields of ≥99% were achieved by marginalizing the losses, typically by loading more than 3 kg mAb/l membrane. Analyses of the purified pools show consistent removal of impurities despite strong mAb–ligand interactions and high membrane loadings. The clearance of host cell proteins was affected by pH and conductivity, but was unaffected by flow rate, membrane properties or scale. The importance of the present study lies in our demonstration of an alternative use of ion-exchange membranes for fast, effective and high yielding purification of mAbs

Sexual Behavior, Risk Perception, And Hiv Transmission Can Respond To Hiv Antiviral Drugs And Vaccines Through Multiple Pathways

There has been growing use of highly active antiretroviral treatment (HAART) for HIV and significant progress in developing prophylactic HIV vaccines. The simplest theories of counterproductive behavioral responses to such interventions tend to focus on single feedback mechanisms: for instance, HAART optimism makes infection less scary and thus promotes risky sexual behavior. Here, we develop an agent based, age-structured model of HIV transmission, risk perception, and partner selection in a core group to explore behavioral responses to interventions. We find that interventions can activate not one, but several feedback mechanisms that could potentially influence decision-making and HIV prevalence. In the model, HAART increases the attractiveness of unprotected sex, but it also increases perceived risk of infection and, on longer timescales, causes demographic impacts that partially counteract HAART optimism. Both HAART and vaccination usually lead to lower rates of unprotected sex on the whole, but intervention effectiveness depends strongly on whether individuals over-or under-estimate intervention coverage. Age-specific effects cause sexual behavior and HIV prevalence to change in opposite ways in old and young age groups. For complex infections like HIV-where interventions influence transmission, demography, sexual behavior and risk perception-we conclude that evaluations of behavioral responses should consider multiple feedback mechanisms

The influence of diet and physical activity on bone density of children aged 5-7 years: The Belfast HAPO family study

ObjectiveOsteoporosis is a global health issue, and modifiable behavioural factors need to be identified in childhood to reduce the risk of osteoporosis in later life. The aim of this study was to investigate the influence of diet and physical activity on bone density of children aged 5–7 years participating in the Belfast Hyperglycaemia and Adverse Pregnancy Outcome (HAPO) Family study.Design and methodsPregnant women were recruited to the Belfast centre of the HAPO study at 24–32 weeks gestation. Offspring were followed up at 5–7 years as part of the Belfast HAPO Family Study. Heel bone mineral density (BMD) and bone mineral apparent density (BMAD) were measured and calculated, respectively. Physical activity in the offspring was measured by accelerometery and dietary intakes were measured using a 4-day food diary.ResultsResults from 793 offspring were analysed. Mean age of the offspring ± standard deviation was 6.4 ± 0.5 years. A mean of 48.3 ± 22.4 min each day was spent in moderate to vigorous physical activity (MVPA). Median (interquartile range) dietary calcium and vitamin D intakes were 844 (662–1073) mg/day and 1.7 (1.1–2.5) μg/day, respectively. Neither dietary vitamin D nor calcium intakes were significantly associated with offspring heel BMD or BMAD in multiple regression. However, controlling for confounders, a 30-min greater MVPA was associated with significantly larger heel BMD (0.018 g/cm2 in boys and 0.010 g/cm2 in girls) and BMAD (0.005 g/cm3 in boys and 0.003 g/cm3 in girls).ConclusionPhysical activity was associated with better BMD and BMAD in 5–7-year-old children. Dietary calcium and vitamin D were not predictive of BMD and BMAD

The PRICE study (Protection Rest Ice Compression Elevation): design of a randomised controlled trial comparing standard versus cryokinetic ice applications in the management of acute ankle sprain [ISRCTN13903946]

<p>Abstract</p> <p>Background</p> <p>Cryotherapy (the application of ice for therapeutic purposes) is one of the most common treatment modalities employed in the immediate management of acute soft tissue injury. Despite its widespread clinical use, the precise physiological responses to therapeutic cooling have not been fully elucidated, and effective evidence-based treatment protocols are yet to be established. Intermittent ice applications are thought to exert a significant analgesic effect. This could facilitate earlier therapeutic exercise after injury, potentially allowing for a quicker return to activity. The primary aim of the forthcoming study is therefore to examine the safety and effectiveness of combining intermittent ice applications with periods of therapeutic exercise in the first week after an acute ankle sprain.</p> <p>Methods/Design</p> <p>The study is a randomised controlled trial. 120 subjects with an acute grade I or grade II ankle sprain will be recruited from Accident & Emergency and a University based Sports Injury Clinic. Subjects will be randomised under strict double-blind conditions to either a standard cryotherapy (intermittent ice applications with compression) or cryokinetic treatment group (intermittent ice applications with compression and therapeutic exercise). After the first week, treatment will be standardised across groups. Assessor blinding will be maintained throughout the trial. Primary outcome will be function, assessed using the Lower Extremity Functional Scale (LEFS). Additional outcomes will include pain (10 cm Visual Analogue Scale), swelling (modified figure-of-eight method) and activity levels (<it>activ</it>PAL™ physical activity monitor, PAL Technologies, Glasgow, UK). Diagnostic Ultrasound (Episcan-1-200 high frequency ultrasound scanning system, Longport International Ltd, PA) will also be used to assess the degree of soft tissue injury. After baseline assessment subjects will be followed up at 1, 2, 3 & 4 weeks post injury. All data will be analysed using repeated measures analysis of co-variance (ANCOVA).</p> <p>Discussion</p> <p>This paper describes the rationale and design of a randomised controlled trial which will examine the effectiveness of two different cryotherapy protocols in the early management of acute ankle sprain.</p> <p>Trial Registration</p> <p>ISRCTN13903946</p

Recent changes in summer distribution and numbers of migratory caribou on the southern Hudson Bay coast

The status of migratory woodland caribou inhabiting the coastal region in southern Hudson Bay is dynamic. The Pen Islands Herd within that region was defined in the 1990s, but opportunistic observations between 1999 and 2007 suggested that its status had significantly changed since the late 1980s and early 1990s. We undertook systematic surveys from the Hayes River, MB, to the Lakitusaki River, ON, in 2008 and 2009 to determine current distribution and minimum numbers of woodland caribou on the southern Hudson Bay coast from the Hayes River, Manitoba, to the Lakitusaki River, Ontario. We documented a significant change in summer distribution during the historical peak aggregation period (7-15 July) compared to the 1990s. In 2008 and 2009, respectively, we tallied 3529 and 3304 animals; however, fewer than 180 caribou were observed each year in the Pen Islands Herd&rsquo;s former summer range where over 10 798 caribou were observed during a systematic survey in 1994. Over 80% of caribou were in the Cape Henrietta Maria area of Ontario. Calf proportions in herds varied from 8% of animals in the west to 20% in the east. Our 2008 and 2009 systematic surveys were focused on the immediate coast, but one exploratory flight inland suggested that more caribou may be inland than had been observed in the 1980s-1990s. The causes of change in the numbers and distribution in the coastal Hudson Bay Lowlands and the association of current caribou with the formerly large Pen Islands Herd may be difficult to determine because of gaps in monitoring, but satellite telemetry, genetic sampling, remote sensing, habitat analysis, and aboriginal knowledge are all being used to pursue answers