High Rate of Subclinical Chikungunya Virus Infection and Association of Neutralizing Antibody with Protection in a Prospective Cohort in The Philippines

Background

Chikungunya virus (CHIKV) is a globally re-emerging arbovirus for which previous studies have indicated the majority of infections result in symptomatic febrile illness. We sought to characterize the proportion of subclinical and symptomatic CHIKV infections in a prospective cohort study in a country with known CHIKV circulation.

Methods/Findings

A prospective longitudinal cohort of subjects ≥6 months old underwent community-based active surveillance for acute febrile illness in Cebu City, Philippines from 2012-13. Subjects with fever history were clinically evaluated at acute, 2, 5, and 8 day visits, and at a 3-week convalescent visit. Blood was collected at the acute and 3-week convalescent visits. Symptomatic CHIKV infections were identified by positive CHIKV PCR in acute blood samples and/or CHIKV IgM/IgG ELISA seroconversion in paired acute/convalescent samples. Enrollment and 12-month blood samples underwent plaque reduction neutralization test (PRNT) using CHIKV attenuated strain 181/clone25. Subclinical CHIKV infections were identified by ≥8-fold rise from a baseline enrollment PRNT titer <10 without symptomatic infection detected during the intervening surveillance period. Selected CHIKV PCR-positive samples underwent viral isolation and envelope protein-1 gene sequencing. Of 853 subjects who completed all study procedures at 12 months, 19 symptomatic infections (2.19 per 100 person-years) and 87 subclinical infections (10.03 per 100 person-years) occurred. The ratio of subclinical-to-symptomatic infections was 4.6:1 varying with age from 2:1 in 6 month-5 year olds to 12:1 in those >50 years old. Baseline CHIKV PRNT titer ≥10 was associated with 100% (95%CI: 46.1, 100.0) protection from symptomatic CHIKV infection. Phylogenetic analysis demonstrated Asian genotype closely related to strains from Asia and the Caribbean.

Conclusions

Subclinical infections accounted for a majority of total CHIKV infections. A positive baseline CHIKV PRNT titer was associated with protection from symptomatic CHIKV infection. These findings have implications for assessing disease burden, understanding virus transmission, and supporting vaccine development.     

Spatio‐temporal variation in European starling reproductive success at multiple small spatial scales

Understanding population dynamics requires spatio‐temporal variation in demography to be measured across appropriate spatial and temporal scales. However, the most appropriate spatial scale(s) may not be obvious, few datasets cover sufficient time periods, and key demographic rates are often incompletely measured. Consequently, it is often assumed that demography will be spatially homogeneous within populations that lack obvious subdivision. Here, we quantify small‐scale spatial and temporal variation in a key demographic rate, reproductive success (RS), within an apparently contiguous population of European starlings. We used hierarchical cluster analysis to define spatial clusters of nest sites at multiple small spatial scales and long‐term data to test the hypothesis that small‐scale spatio‐temporal variation in RS occurred. RS was measured as the number of chicks alive ca. 12 days posthatch either per first brood or per nest site per breeding season (thereby incorporating multiple breeding attempts). First brood RS varied substantially among spatial clusters and years. Furthermore, the pattern of spatial variation was stable across years; some nest clusters consistently produced more chicks than others. Total seasonal RS also varied substantially among spatial clusters and years. However, the magnitude of variation was much larger and the pattern of spatial variation was no longer temporally consistent. Furthermore, the estimated magnitude of spatial variation in RS was greater at smaller spatial scales. We thereby demonstrate substantial spatial, temporal, and spatio‐temporal variation in RS occurring at very small spatial scales. We show that the estimated magnitude of this variation depended on spatial scale and that spatio‐temporal variation would not have been detected if season‐long RS had not been measured. Such small‐scale spatio‐temporal variation should be incorporated into empirical and theoretical treatments of population dynamics.     

Dead Shrimp Blues: A Global Assessment of Extinction Risk in Freshwater Shrimps (Crustacea: Decapoda: Caridea)

We present the first global assessment of extinction risk for a major group of freshwater invertebrates, caridean shrimps. The risk of extinction for all 763 species was assessed using the IUCN Red List criteria that include geographic ranges, habitats, ecology and past and present threats. The Indo-Malayan region holds over half of global species diversity, with a peak in Indo-China and southern China. Shrimps primarily inhabit flowing water; however, a significant subterranean component is present, which is more threatened than the surface fauna. Two species are extinct with a further 10 possibly extinct, and almost one third of species are either threatened or Near Threatened (NT). Threats to freshwater shrimps include agricultural and urban pollution impact over two-thirds of threatened and NT species. Invasive species and climate change have the greatest overall impact of all threats (based on combined timing, scope and severity of threats).     

S6K1 is a multifaceted regulator of Mdm2 that connects nutrient status and DNA damage response

p53 mediates DNA damage‐induced cell‐cycle arrest, apoptosis, or senescence, and it is controlled by Mdm2, which mainly ubiquitinates p53 in the nucleus and promotes p53 nuclear export and degradation. By searching for the kinases responsible for Mdm2 S163 phosphorylation under genotoxic stress, we identified S6K1 as a multifaceted regulator of Mdm2. DNA damage activates mTOR‐S6K1 through p38α MAPK. The activated S6K1 forms a tighter complex with Mdm2, inhibits Mdm2‐mediated p53 ubiquitination, and promotes p53 induction, in addition to phosphorylating Mdm2 on S163. Deactivation of mTOR‐S6K1 signalling leads to Mdm2 nuclear translocation, which is facilitated by S163 phosphorylation, a reduction in p53 induction, and an alteration in p53‐dependent cell death. These findings thus establish mTOR‐S6K1 as a novel regulator of p53 in DNA damage response and likely in tumorigenesis. S6K1–Mdm2 interaction presents a route for cells to incorporate the metabolic/energy cues into DNA damage response and links the aging‐controlling Mdm2–p53 and mTOR‐S6K pathways.     

The crystal structure of a TIR domain from Arabidopsis thaliana reveals a conserved helical region unique to plants

Plants use a highly evolved immune system to exhibit defense response against microbial infections. The plant TIR domain, together with the nucleotide‐binding (NB) domain and/or a LRR region, forms a type of molecule, named resistance (R) proteins, that interact with microbial effector proteins and elicit hypersensitive responses against infection. Here, we report the first crystal structure of a plant TIR domain from Arabidopsis thaliana (AtTIR) solved at a resolution of 2.0 Å. The structure consists of five β‐strands forming a parallel β‐sheet at the core of the protein. The β‐strands are connected by a series of α‐helices and the overall fold mimics closely that of other mammalian and bacterial TIR domains. However, the region of the αD‐helix reveals significant differences when compared with other TIR structures, especially the αD3‐helix that corresponds to an insertion only present in plant TIR domains. Available mutagenesis data suggest that several conserved and exposed residues in this region are involved in the plant TIR signaling function.     

Thickness sensing of hMSCs on collagen gel directs stem cell fate

Mechanically compliant substrate provides crucial biomechanical cues for multipotent stem cells to regulate cellular fates such as differentiation, proliferation and maintenance of their phenotype. Effective modulus of which cells sense is not only determined by intrinsic mechanical properties of the substrate, but also the thickness of substrate. From our study, it was found that interference from underlying rigid support at hundreds of microns away could induce significant cellular response. Human mesenchymal stem cells (hMSCs) were cultured on compliant biological gel, collagen type I, of different thickness but identical ECM composition and local stiffness. The cells sensed the thin gel (130 μm) as having a higher effective modulus than the thick gel (1440 μm) and this was reflected in their changes in morphology, actin fibers structure, proliferation and tissue specific gene expression. Commitment into neuronal lineage was observed on the thin gel only. Conversely, the thick gel (1440 μm) was found to act like a substrate with lower effective modulus that inhibited actin fiber polymerization. Stem cells on the thick substrate did not express tissue specific genes and remained at their quiescent state. This study highlighted the need to consider not only the local modulus but also the thickness of biopolymer gel coating during modulation of cellular responses.     

Bullatantriol,a sesquiterpene from annona bullata

Bullatantriol has been isolated from Annona bullata. Its constitution and relative configuration have been established by X-ray analysis. Its absolute configuration has been assigned by chiroptical investigation of the corresponding 7-ketone.     

Mutagenic and carcinogenic potential of a textile azo dye processing plant effluent that impacts a drinking water source

Recently a textile azo dye processing plant effluent was identified as one of the sources of mutagenic activity detected in the Cristais River, a drinking water source in Brazil [G.A. Umbuzeiro, D.A. Roubicek, C.M. Rech, M.I.Z. Sato, L.D. Claxton, Investigating the sources of the mutagenic activity found in a river using the Salmonella assay and different water extraction procedures, Chemosphere 54 (2004) 1589-1597]. Besides presenting high mutagenic activity in the Salmonella/microsome assay, the mutagenic nitro-aminoazobenzenes dyes CI Disperse Blue 373, CI Disperse Violet 93, and CI Disperse Orange 37 [G.A. Umbuzeiro, H.S. Freeman, S.H. Warren, D.P. Oliveira, Y. Terao, T. Watanabe, L.D. Claxton, The contribution of azo dyes in the mutagenic activity of the Cristais river, Chemosphere 60 (2005) 55-64] as well as benzidine, a known carcinogenic compound [T.M. Mazzo, A.A. Saczk, G.A. Umbuzeiro, M.V.B. Zanoni, Analysis of aromatic amines in surface waters receiving wastewater from textile industry by liquid chromatographic with eletrochemical detection, Anal. Lett., in press] were found in this effluent. After approximately 6 km from the discharge of this effluent, a drinking water treatment plant treats and distributes the water to a population of approximate 60,000. As shown previously, the mutagens in the DWTP intake water are not completely removed by the treatment. The water used for human consumption presented mutagenic activity related to nitro-aromatics and aromatic amines compounds probably derived from the cited textile processing plant effluent discharge [G.A. Umbuzeiro, D.A. Roubicek, C.M. Rech, M.I.Z. Sato, L.D. Claxton, Investigating the sources of the mutagenic activity found in a river using the Salmonella assay and different water extraction procedures, Chemosphere 54 (2004) 1589-1597; G.A. Umbuzeiro, H.S. Freeman, S.H. Warren, D.P. Oliveira, Y. Terao, T. Watanabe, L.D. Claxton, The contribution of azo dyes in the mutagenic activity of the Cristais river, Chemosphere 60 (2005) 55-64]. Therefore, it is important to evaluate the possible risks involved in the human consumption of this contaminated water. With that objective, one sample of the cited industrial effluent was tested for carcinogenicity in the aberrant crypt foci medium-term assay in colon of Wistar rats. The rats received the effluent in natura through drinking water at concentrations of 0.1%, 1%, and 10%. The effluent mutagenicity was also confirmed in the Salmonella/microsome assay with the strains TA98 and YG1041. There was an increased number of preneoplastic lesions in the colon of rats exposed to concentrations of 1% and 10% of the effluent, and a positive response for both Salmonella strains tested. These results indicate that the discharge of the effluent should be avoided in waters used for human consumption and show the sensitivity of the ACF crypt foci assay as an important tool to evaluate the carcinogenic potential of environmental complex mixtures.     

Effect of germicidal UVC light on fungi isolated from grapes and raisins

AIMS: To examine how UVC affects the different genera of fungi commonly isolated from grapes, with the aim of understanding changes in mycobiota during grape ripening and possible applications for preventing grape decay during storage. METHODS AND RESULTS: Spores of Aspergillus carbonarius, Aspergillus niger, Cladosporium herbarum, Penicillium janthinellum and Alternaria alternata (between 100-250 spores/plate agar) were UVC irradiated for 0 (control), 10, 20, 30, 60, 300 and 600 s. Plates were incubated at 25 degrees C and colonies were counted daily up to 7 days. Alternaria alternata and Aspergillus carbonarius were the most resistant fungi. Conidial germination in these species was reduced by approx. 25% after 10 s of exposure, compared with greater than 70% reduction for the remaining species tested. Penicillium janthinellum spores were the most susceptible at this wavelength. UVC exposures of 300 s prevented growth of all isolates studied, except for Alternaria alternata. CONCLUSIONS: UVC irradiation plays a major role in selecting for particular fungi that dominate the mycobiota of drying grapes. SIGNIFICANCE AND IMPACT OF THE STUDY: The UVC irradiation of harvested grapes could prevent germination of contaminant fungi during storage or further dehydration.     

The inner cavity of Escherichia coli DegP protein is not essential for molecular chaperone and proteolytic activity

The Escherichia coli DegP protein is an essential periplasmic protein for bacterial survival at high temperatures. DegP has the unusual property of working as a chaperone below 28 degrees C, but efficiently degrading unfolded proteins above 28 degrees C. Monomeric DegP contains a protease domain and two PDZ domains. It oligomerizes into a hexameric cage through the staggered association of trimers. The active sites are located in a central cavity that is only accessible laterally, and the 12 PDZ domains act as mobile sidewalls that mediate opening and closing of the gates. As access to the active sites is restricted, DegP is an example of a self-compartmentalized protease. To determine the essential elements of DegP that maintain the integrity of the hexameric cage, we constructed several deletion mutants of DegP that formed trimers rather than hexamers. We found that residues 39 to 78 within the LA loops, as well as the PDZ2 domains are essential for the integrity of the DegP hexamer. In addition, we asked whether an enclosed cavity or cage of specific dimensions is required for the protease and chaperone activities in DegP. Both activities were maintained in the trimeric DegP mutants without an enclosed cavity and in deletion DegP mutants with significantly reduced dimensions of the cage. We conclude that the functional unit for the protease and chaperone activities of DegP is a trimer and that neither a cavity of specific dimensions nor the presence of an enclosed cavity appears to be essential for the protease and chaperone activities of DegP.