Rift Valley Fever Risk Map Model and Seroprevalence in Selected Wild Ungulates and Camels from Kenya

Since the first isolation of Rift Valley fever virus (RVFV) in the 1930s, there have been multiple epizootics and epidemics in animals and humans in sub-Saharan Africa. Prospective climate-based models have recently been developed that flag areas at risk of RVFV transmission in endemic regions based on key environmental indicators that precede Rift Valley fever (RVF) epizootics and epidemics. Although the timing and locations of human case data from the 2006–2007 RVF outbreak in Kenya have been compared to risk zones flagged by the model, seroprevalence of RVF antibodies in wildlife has not yet been analyzed in light of temporal and spatial predictions of RVF activity. Primarily wild ungulate serum samples from periods before, during, and after the 2006–2007 RVF epizootic were analyzed for the presence of RVFV IgM and/or IgG antibody. Results show an increase in RVF seropositivity from samples collected in 2007 (31.8%), compared to antibody prevalence observed from 2000–2006 (3.3%). After the epizootic, average RVF seropositivity diminished to 5% in samples collected from 2008–2009. Overlaying maps of modeled RVF risk assessments with sampling locations indicated positive RVF serology in several species of wild ungulate in or near areas flagged as being at risk for RVF. Our results establish the need to continue and expand sero-surveillance of wildlife species Kenya and elsewhere in the Horn of Africa to further calibrate and improve the RVF risk model, and better understand the dynamics of RVFV transmission.     

Rates and Factors Associated with Major Modifications to First-Line Combination Antiretroviral Therapy: Results from the Asia-Pacific Region

Background

In the Asia-Pacific region many countries have adopted the WHO’s public health approach to HIV care and treatment. We performed exploratory analyses of the factors associated with first major modification to first-line combination antiretroviral therapy (ART) in resource-rich and resource-limited countries in the region.

Methods

We selected treatment naive HIV-positive adults from the Australian HIV Observational Database (AHOD) and the TREAT Asia HIV Observational Database (TAHOD). We dichotomised each country’s per capita income into high/upper-middle (T-H) and lower-middle/low (T-L). Survival methods stratified by income were used to explore time to first major modification of first-line ART and associated factors. We defined a treatment modification as either initiation of a new class of antiretroviral (ARV) or a substitution of two or more ARV agents from within the same ARV class.

Results

A total of 4250 patients had 961 major modifications to first-line ART in the first five years of therapy. The cumulative incidence (95% CI) of treatment modification was 0.48 (0.44–0.52), 0.33 (0.30–0.36) and 0.21 (0.18–0.23) for AHOD, T-H and T-L respectively. We found no strong associations between typical patient characteristic factors and rates of treatment modification. In AHOD, relative to sites that monitor twice-yearly (both CD4 and HIV RNA-VL), quarterly monitoring corresponded with a doubling of the rate of treatment modifications. In T-H, relative to sites that monitor once-yearly (both CD4 and HIV RNA-VL), monitoring twice-yearly corresponded to a 1.8 factor increase in treatment modifications. In T-L, no sites on average monitored both CD4 & HIV RNA-VL concurrently once-yearly. We found no differences in rates of modifications for once- or twice-yearly CD4 count monitoring.

Conclusions

Low-income countries tended to have lower rates of major modifications made to first-line ART compared to higher-income countries. In higher-income countries, an increased rate of RNA-VL monitoring was associated with increased modifications to first-line ART.     

Pharmacological Inhibition of polysialyltransferase ST8SiaII Modulates Tumour Cell Migration

Polysialic acid (polySia), an α-2,8-glycosidically linked polymer of sialic acid, is a developmentally regulated post-translational modification predominantly found on NCAM (neuronal cell adhesion molecule). Whilst high levels are expressed during development, peripheral adult organs do not express polySia-NCAM. However, tumours of neural crest-origin re-express polySia-NCAM: its occurrence correlates with aggressive and invasive disease and poor clinical prognosis in different cancer types, notably including small cell lung cancer (SCLC), pancreatic cancer and neuroblastoma. In neuronal development, polySia-NCAM biosynthesis is catalysed by two polysialyltransferases, ST8SiaII and ST8SiaIV, but it is ST8SiaII that is the prominent enzyme in tumours. The aim of this study was to determine the effect of ST8SiaII inhibition by a small molecule on tumour cell migration, utilising cytidine monophosphate (CMP) as a tool compound. Using immunoblotting we showed that CMP reduced ST8iaII-mediated polysialylation of NCAM. Utilizing a novel HPLC-based assay to quantify polysialylation of a fluorescent acceptor (DMB-DP3), we demonstrated that CMP is a competitive inhibitor of ST8SiaII (K _i = 10 µM). Importantly, we have shown that CMP causes a concentration-dependent reduction in tumour cell-surface polySia expression, with an absence of toxicity. When ST8SiaII-expressing tumour cells (SH-SY5Y and C6-STX) were evaluated in 2D cell migration assays, ST8SiaII inhibition led to significant reductions in migration, while CMP had no effect on cells not expressing ST8SiaII (DLD-1 and C6-WT). The study demonstrates for the first time that a polysialyltransferase inhibitor can modulate migration in ST8SiaII-expressing tumour cells. We conclude that ST8SiaII can be considered a druggable target with the potential for interfering with a critical mechanism in tumour cell dissemination in metastatic cancers.     

What Are the Health Benefits of Active Travel? A Systematic Review of Trials and Cohort Studies

Background

Increasing active travel (primarily walking and cycling) has been widely advocated for reducing obesity levels and achieving other population health benefits. However, the strength of evidence underpinning this strategy is unclear. This study aimed to assess the evidence that active travel has significant health benefits.

Methods

The study design was a systematic review of (i) non-randomised and randomised controlled trials, and (ii) prospective observational studies examining either (a) the effects of interventions to promote active travel or (b) the association between active travel and health outcomes. Reports of studies were identified by searching 11 electronic databases, websites, reference lists and papers identified by experts in the field. Prospective observational and intervention studies measuring any health outcome of active travel in the general population were included. Studies of patient groups were excluded.

Results

Twenty-four studies from 12 countries were included, of which six were studies conducted with children. Five studies evaluated active travel interventions. Nineteen were prospective cohort studies which did not evaluate the impact of a specific intervention. No studies were identified with obesity as an outcome in adults; one of five prospective cohort studies in children found an association between obesity and active travel. Small positive effects on other health outcomes were found in five intervention studies, but these were all at risk of selection bias. Modest benefits for other health outcomes were identified in five prospective studies. There is suggestive evidence that active travel may have a positive effect on diabetes prevention, which may be an important area for future research.

Conclusions

Active travel may have positive effects on health outcomes, but there is little robust evidence to date of the effectiveness of active transport interventions for reducing obesity. Future evaluations of such interventions should include an assessment of their impacts on obesity and other health outcomes.     

Millennial-Scale Temperature Change Velocity in the Continental Northern Neotropics

Climate has been inherently linked to global diversity patterns, and yet no empirical data are available to put modern climate change into a millennial-scale context. High tropical species diversity has been linked to slow rates of climate change during the Quaternary, an assumption that lacks an empirical foundation. Thus, there is the need for quantifying the velocity at which the bioclimatic space changed during the Quaternary in the tropics. Here we present rates of climate change for the late Pleistocene and Holocene from Mexico and Guatemala. An extensive modern pollen survey and fossil pollen data from two long sedimentary records (30,000 and 86,000 years for highlands and lowlands, respectively) were used to estimate past temperatures. Derived temperature profiles show a parallel long-term trend and a similar cooling during the Last Glacial Maximum in the Guatemalan lowlands and the Mexican highlands. Temperature estimates and digital elevation models were used to calculate the velocity of isotherm displacement (temperature change velocity) for the time period contained in each record. Our analyses showed that temperature change velocities in Mesoamerica during the late Quaternary were at least four times slower than values reported for the last 50 years, but also at least twice as fast as those obtained from recent models. Our data demonstrate that, given extremely high temperature change velocities, species survival must have relied on either microrefugial populations or persistence of suppressed individuals. Contrary to the usual expectation of stable climates being associated with high diversity, our results suggest that Quaternary tropical diversity was probably maintained by centennial-scale oscillatory climatic variability that forestalled competitive exclusion. As humans have simplified modern landscapes, thereby removing potential microrefugia, and climate change is occurring monotonically at a very high velocity, extinction risk for tropical species is higher than at any time in the last 86,000 years.     

Adaptation of an L-Proline Adenylation Domain to Use 4-Propyl-L-Proline in the Evolution of Lincosamide Biosynthesis

Clinically used lincosamide antibiotic lincomycin incorporates in its structure 4-propyl-L-proline (PPL), an unusual amino acid, while celesticetin, a less efficient related compound, makes use of proteinogenic L-proline. Biochemical characterization, as well as phylogenetic analysis and homology modelling combined with the molecular dynamics simulation were employed for complex comparative analysis of the orthologous protein pair LmbC and CcbC from the biosynthesis of lincomycin and celesticetin, respectively. The analysis proved the compared proteins to be the stand-alone adenylation domains strictly preferring their own natural substrate, PPL or L-proline. The LmbC substrate binding pocket is adapted to accomodate a rare PPL precursor. When compared with L-proline specific ones, several large amino acid residues were replaced by smaller ones opening a channel which allowed the alkyl side chain of PPL to be accommodated. One of the most important differences, that of the residue corresponding to V306 in CcbC changing to G308 in LmbC, was investigated in vitro and in silico. Moreover, the substrate binding pocket rearrangement also allowed LmbC to effectively adenylate 4-butyl-L-proline and 4-pentyl-L-proline, substrates with even longer alkyl side chains, producing more potent lincosamides. A shift of LmbC substrate specificity appears to be an integral part of biosynthetic pathway adaptation to the PPL acquisition. A set of genes presumably coding for the PPL biosynthesis is present in the lincomycin - but not in the celesticetin cluster; their homologs are found in biosynthetic clusters of some pyrrolobenzodiazepines (PBD) and hormaomycin. Whereas in the PBD and hormaomycin pathways the arising precursors are condensed to another amino acid moiety, the LmbC protein is the first functionally proved part of a unique condensation enzyme connecting PPL to the specialized amino sugar building unit.     

The K+ Channel KCa3.1 as a Novel Target for Idiopathic Pulmonary Fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a common, progressive and invariably lethal interstitial lung disease with no effective therapy. We hypothesised that K_Ca3.1 K⁺ channel-dependent cell processes contribute to IPF pathophysiology.

Methods

K_Ca3.1 expression in primary human lung myofibroblasts was examined using RT-PCR, western blot, immunofluorescence and patch-clamp electrophysiology. The role of K_Ca3.1 channels in myofibroblast proliferation, wound healing, collagen secretion and contraction was examined using two specific and distinct K_Ca3.1 blockers (TRAM-34 and ICA-17043 [Senicapoc]).

Results

Both healthy non fibrotic control and IPF-derived human lung myofibroblasts expressed K_Ca3.1 channel mRNA and protein. K_Ca3.1 ion currents were elicited more frequently and were larger in IPF-derived myofibroblasts compared to controls. K_Ca3.1 currents were increased in myofibroblasts by TGFβ1 and basic FGF. K_Ca3.1 was expressed strongly in IPF tissue. K_Ca3.1 pharmacological blockade attenuated human myofibroblast proliferation, wound healing, collagen secretion and contractility in vitro, and this was associated with inhibition of TGFβ1-dependent increases in intracellular free Ca²⁺.

Conclusions

K_Ca3.1 activity promotes pro-fibrotic human lung myofibroblast function. Blocking K_Ca3.1 may offer a novel approach to treating IPF with the potential for rapid translation to the clinic.     

Elucidating Emergence and Transmission of Multidrug-Resistant Tuberculosis in Treatment Experienced Patients by Whole Genome Sequencing

Background

Understanding the emergence and spread of multidrug-resistant tuberculosis (MDR-TB) is crucial for its control. MDR-TB in previously treated patients is generally attributed to the selection of drug resistant mutants during inadequate therapy rather than transmission of a resistant strain. Traditional genotyping methods are not sufficient to distinguish strains in populations with a high burden of tuberculosis and it has previously been difficult to assess the degree of transmission in these settings. We have used whole genome analysis to investigate M. tuberculosis strains isolated from treatment experienced patients with MDR-TB in Uganda over a period of four years.

Methods and Findings

We used high throughput genome sequencing technology to investigate small polymorphisms and large deletions in 51 Mycobacterium tuberculosis samples from 41 treatment-experienced TB patients attending a TB referral and treatment clinic in Kampala. This was a convenience sample representing 69% of MDR-TB cases identified over the four year period. Low polymorphism was observed in longitudinal samples from individual patients (2-15 SNPs). Clusters of samples with less than 50 SNPs variation were examined. Three clusters comprising a total of 8 patients were found with almost identical genetic profiles, including mutations predictive for resistance to rifampicin and isoniazid, suggesting transmission of MDR-TB. Two patients with previous drug susceptible disease were found to have acquired MDR strains, one of which shared its genotype with an isolate from another patient in the cohort.

Conclusions

Whole genome sequence analysis identified MDR-TB strains that were shared by more than one patient. The transmission of multidrug-resistant disease in this cohort of retreatment patients emphasises the importance of early detection and need for infection control. Consideration should be given to rapid testing for drug resistance in patients undergoing treatment to monitor the emergence of resistance and permit early intervention to avoid onward transmission.