Association of pneumococcal carriage in infants with the risk of carriage among their contacts in Nha Trang,Vietnam: A nested cross-sectional survey

BackgroundInfants are at highest risk of pneumococcal disease. Their added protection through herd effects is a key part in the considerations on optimal pneumococcal vaccination strategies. Yet, little is currently known about the main transmission pathways to this vulnerable age group. Hence, this study investigates pneumococcal transmission routes to infants in the coastal city of Nha Trang, Vietnam.Methods and findingsIn October 2018, we conducted a nested cross-sectional contact and pneumococcal carriage survey in randomly selected 4- to 11-month-old infants across all 27 communes of Nha Trang. Bayesian logistic regression models were used to estimate age specific carriage prevalence in the population, a proxy for the probability that a contact of a given age could lead to pneumococcal exposure for the infant. We used another Bayesian logistic regression model to estimate the correlation between infant carriage and the probability that at least one of their reported contacts carried pneumococci, controlling for age and locality. In total, 1,583 infants between 4 and 13 months old participated, with 7,428 contacts reported. Few infants (5%, or 86 infants) attended day care, and carriage prevalence was 22% (353 infants). Most infants (61%, or 966 infants) had less than a 25% probability to have had close contact with a pneumococcal carrier on the surveyed day. Pneumococcal infection risk and contact behaviour were highly correlated: If adjusted for age and locality, the odds of an infant’s carriage increased by 22% (95% confidence interval (CI): 15 to 29) per 10 percentage points increase in the probability to have had close contact with at least 1 pneumococcal carrier. Moreover, 2- to 6-year-old children contributed 51% (95% CI: 39 to 63) to the total direct pneumococcal exposure risks to infants in this setting. The main limitation of this study is that exposure risk was assessed indirectly by the age-dependent propensity for carriage of a contact and not by assessing carriage of such contacts directly.ConclusionsIn this study, we observed that cross-sectional contact and infection studies could help identify pneumococcal transmission routes and that preschool-age children may be the largest reservoir for pneumococcal transmission to infants in Nha Trang, Vietnam.     

Ubiquity of Bacillus thuringiensis on phylloplanes of arboreous and herbaceous plants in Japan

A total of 120 Bacillus thuringiensis strains was isolated from phylloplanes of 35 species of arboreous and herbaceous plants in an area of northern Kyushu, Japan. The isolates belonged to at least 17 serotypes and the group of H serotype 3 was predominant. Twenty strains were untypable by the existing reference H antisera and 47 were untestable due to autoagglutination or poor motility. Of the 120 isolates, 25 produced bipyramidal parasporal inclusions and the others, spherical or irregular-shaped. Insecticidal activity against mosquitoes ( Culex pipiens molestus and Anopheles stephensi ) and/or diamondback moth, Plutella xylostella , was associated with 28 isolates (23·3%). Overall results revealed that: B. thuringiensis is ubiquitous on a variety of plants; bacterial flora on phylloplanes consists of highly heterogeneous H serogroups; and there is little correlation between plant species and phenotypes of B. thuringiensis isolates.     

The kinesin KIF4 mediates HBV/HDV entry through the regulation of surface NTCP localization and can be targeted by RXR agonists in vitro

Intracellular transport via microtubule-based dynein and kinesin family motors plays a key role in viral reproduction and transmission. We show here that Kinesin Family Member 4 (KIF4) plays an important role in HBV/HDV infection. We intended to explore host factors impacting the HBV life cycle that can be therapeutically addressed using siRNA library transfection and HBV/NLuc (HBV/NL) reporter virus infection in HepG2-hNTCP cells. KIF4 silencing resulted in a 3-fold reduction in luciferase activity following HBV/NL infection. KIF4 knockdown suppressed both HBV and HDV infection. Transient KIF4 depletion reduced surface and raised intracellular NTCP (HBV/HDV entry receptor) levels, according to both cellular fractionation and immunofluorescence analysis (IF). Overexpression of wild-type KIF4 but not ATPase-null KIF4 mutant regained the surface localization of NTCP and significantly restored HBV permissiveness in these cells. IF revealed KIF4 and NTCP colocalization across microtubule filaments, and a co-immunoprecipitation study revealed that KIF4 interacts with NTCP. KIF4 expression is regulated by FOXM1. Interestingly, we discovered that RXR agonists (Bexarotene, and Alitretinoin) down-regulated KIF4 expression via FOXM1-mediated suppression, resulting in a substantial decrease in HBV-Pre-S1 protein attachment to HepG2-hNTCP cell surface and subsequent HBV infection in both HepG2-hNTCP and primary human hepatocyte (PXB) (Bexarotene, IC₅₀ 1.89 ± 0.98 μM) cultures. Overall, our findings show that human KIF4 is a critical regulator of NTCP surface transport and localization, which is required for NTCP to function as a receptor for HBV/HDV entry. Furthermore, small molecules that suppress or alleviate KIF4 expression would be potential antiviral candidates targeting HBV and HDV entry.     

Crystal structure of Grimontia hollisae collagenase provides insights into its novel substrate specificity toward collagen

Collagenase from the gram-negative bacterium Grimontia hollisae strain 1706B (Ghcol) degrades collagen more efficiently even than clostridial collagenase, the most widely used industrial collagenase. However, the structural determinants facilitating this efficiency are unclear. Here, we report the crystal structures of ligand-free and Gly-Pro-hydroxyproline (Hyp)-complexed Ghcol at 2.2 and 2.4 Å resolution, respectively. These structures revealed that the activator and peptidase domains in Ghcol form a saddle-shaped structure with one zinc ion and four calcium ions. In addition, the activator domain comprises two homologous subdomains, whereas zinc-bound water was observed in the ligand-free Ghcol. In the ligand-complexed Ghcol, we found two Gly-Pro-Hyp molecules, each bind at the active site and at two surfaces on the duplicate subdomains of the activator domain facing the active site, and the nucleophilic water is replaced by the carboxyl oxygen of Hyp at the P1 position. Furthermore, all Gly-Pro-Hyp molecules bound to Ghcol have almost the same conformation as Pro-Pro-Gly motif in model collagen (Pro-Pro-Gly)₁₀, suggesting these three sites contribute to the unwinding of the collagen triple helix. A comparison of activities revealed that Ghcol exhibits broader substrate specificity than clostridial collagenase at the P2 and P2′ positions, which may be attributed to the larger space available for substrate binding at the S2 and S2′ sites in Ghcol. Analysis of variants of three active-site Tyr residues revealed that mutation of Tyr564 affected catalysis, whereas mutation of Tyr476 or Tyr555 affected substrate recognition. These results provide insights into the substrate specificity and mechanism of G. hollisae collagenase.     

On the preparation of indoxyl red from indican and some new characteristics

An indole compound with a strong purple–red color was produced by boiling a solution of indican under acidic conditions and purified by chromatographies on DEAE-650S Toyopearl TSK-gel and silica-gel columns. The purple-red compound purified was identified as indoxyl red, on the basis of FAB Mass, ¹³C NMR, ¹H NMR, UV–visible spectra, and IR spectra. Although indoxyl red was first synthesized by Seidel⁹ 70 years ago, very little information has been available on its characteristics. We repot here that the compound was purple-red colored at acidic pH and green at pH 13, and showed antiproliferative and cytotoxic activities to the mouse B cell lymphoma cell line NSF202.     

Diterpenoids from the fruits of Vitex trifolia

An abietane-type diterpene, named vitetrifolin A, and two labdane-type diterpenes, named vitetrifolins B and C, were isolated from the acetone extract of the fruits of Vitex trifolia L. (Viticis Fructus; Verbenaceae) along with three known diterpenes, rotundifuran, dihydrosolidagenone and abietatriene 3beta-ol. The structures of these compounds were elucidated on the basis of spectroscopic analysis, X-ray crystallographic analysis and chemical evidence.     

Oncogenic receptor tyrosine kinase in leukemia.

Growth, survival and differentiation of hematopoietic cells are regulated by the interaction between hematopoietic growth factors and their receptors. While the defect in this interaction results in an insufficient hematopoiesis, the aberrantly elevated activation leads to the transformation of hematopoietic cells. The constitutive active mutations of receptor tyrosine kinase, such as c-Kit platelet-derived growth factor receptor (PDGFR) or fins-like tyrosine kinase 3 (Flt3), play a major role in the development of hematopoietic neoplasia. The constitutive activation is provoked by several mechanisms, such as making fusion genes by chromosomal translocations, or various mutations involving regulatory regions of the receptor. The chromosomal translocation brings the receptor intracytoplasmic domain juxtaposed to an unrelated molecule which has dimerization or multimerization motif, resulting in the constitutive dimerization of the receptor. The missense, insertion or deletion mutations in the regulatory regions, such as juxtamembrane domain, activation loop and extracellular domain, cause constitutive activation by releasing the respective auto-inhibitory functions of each regulatory region. Constitutive active receptors generate different signals quantitatively and qualitatively from wild type receptor, which mediate the oncogenic phenotype. Given the frequent involvement of constitutive active receptor tyrosine kinase in hematopoietic malignancies, targeted inhibitions of active tyrosine kinase and downstream aberrant signaling are rapidly developing novel therapeutic modality with much promise.     

Isolation and characterization of a novel Bacillus thuringiensis strain expressing a novel crystal protein with cytocidal activity against human cancer cells

AIMS: To characterize a novel, unusual, Bacillus thuringiensis strain, to clone its Cry gene and determine the spectrum of action of the encoded Cry protein. METHODS AND RESULTS: The B. thuringiensis strain, referred to as M15, was isolated from dead two-spotted spider mites (Tetranychus urticae Koch; Arthropoda: Arachnida: Tetranychidae). It is an autoagglutination-positive strain and is therefore non-serotypeable. A sporulated culture produces a roughly spherical parasporal inclusion body, the crystal, tightly coupled to the spore. Although the crystal appears to be composed of at least two major polypeptides of 86 and 79 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Southern hybridization indicates that the corresponding crystal protein gene is likely present in only one copy. The crystal protein gene was cloned and, based on nucleotide sequence homology with an orthologous cry31Aa1 gene, assigned the name cry31Aa2. Although initially isolated from spider mites, B. thuringiensis M15 is non-toxic to spider mites and it does not produce the wide spectrum beta-exotoxin. Assays on mammalian cells, however, reveal that Cry31Aa2, when cleaved with trypsin, is cytocidal to some human cancer cells but not to normal human cells. No cytocidal activity was induced after protease treatment of Cry31Aa2 with either chymotrypsin or proteinase K. Trypsin, chymotrypsin and proteinase K cleavage sites were determined. CONCLUSIONS: The B. thuringiensis strain M15 exhibits specific cytocidal activities against some human cancer cells. Significance and Impact of the Study: This study raises questions as to the actual role of this bacterial strain and its crystal protein in the environment. It may be possible to further develop the Cry31Aa2 protein to target specific human cancer cells.