Spatial cluster analysis of Plasmodium vivax and P. malariae exposure using serological data among Haitian school children sampled between 2014 and 2016

BackgroundEstimation of malaria prevalence in very low transmission settings is difficult by even the most advanced diagnostic tests. Antibodies against malaria antigens provide an indicator of active or past exposure to these parasites. The prominent malaria species within Haiti is Plasmodium falciparum, but P. vivax and P. malariae infections are also known to be endemic.Methodology/Principal findingsFrom 2014–2016, 28,681 Haitian children were enrolled in school-based serosurveys and were asked to provide a blood sample for detection of antibodies against multiple infectious diseases. IgG against the P. falciparum, P. vivax, and P. malariae merozoite surface protein 19kD subunit (MSP1₁₉) antigens was detected by a multiplex bead assay (MBA). A subset of samples was also tested for Plasmodium DNA by PCR assays, and for Plasmodium antigens by a multiplex antigen detection assay. Geospatial clustering of high seroprevalence areas for P. vivax and P. malariae antigens was assessed by both Ripley’s K-function and Kulldorff’s spatial scan statistic. Of 21,719 children enrolled in 680 schools in Haiti who provided samples to assay for IgG against PmMSP1₁₉, 278 (1.27%) were seropositive. Of 24,559 children enrolled in 788 schools providing samples for PvMSP1₁₉ serology, 113 (0.46%) were seropositive. Two significant clusters of seropositivity were identified throughout the country for P. malariae exposure, and two identified for P. vivax. No samples were found to be positive for Plasmodium DNA or antigens.Conclusions/SignificanceFrom school-based surveys conducted from 2014 to 2016, very few Haitian children had evidence of exposure to P. vivax or P. malariae, with no children testing positive for active infection. Spatial scan statistics identified non-overlapping areas of the country with higher seroprevalence for these two malarias. Serological data provides useful information of exposure to very low endemic malaria species in a population that is unlikely to present to clinics with symptomatic infections.     

Mannose receptor dependent uptake of a ricin A chain--antibody conjugate by rat liver non-parenchymal cells

Mannose receptor mediated uptake by the reticuloendothelial system has been suggested as an explanation for the rapid removal of ricin A chain antibody conjugates from the circulation after their administration. We have measured, in the rat, hepatic uptake of a ricin A chain antibody conjugate in vivo and its susceptibility to inhibition by a mannosylated protein and have measured uptake of the conjugate in vitro by rat parenchymal and non-parenchymal liver cells. The results indicate that rapid hepatic uptake of conjugate does occur in vivo; cultured non-parenchymal cells accumulate the conjugate to a much greater degree than cultured parenchymal cells and that mannose receptors appear to be involved in the process.     

Tobamovirus evolution: gene overlaps, recombination, and taxonomic implications

Tobamoviruses, mostly isolated from solanaceous plants, may represent ancient virus lineages that have codiverged with their hosts. Recently completed nucleotide sequences of six nonsolanaceous tobamoviruses allowed assessment of the codivergence hypothesis and support a third subgroup within tobamoviruses. The genomic sequences of 12 tobamoviruses and the partial sequences of 11 others have been analyzed. Comparisons of the predicted protein sequences revealed three clusters of tobamoviruses, corresponding to those infecting solanaceous species (subgroup 1), those infecting cucurbits and legumes (subgroup 2), and those infecting crucifers. The orchid-infecting odontoglossum ringspot tobamovirus was associated with subgroup 1 genomes by its coat and movement protein sequences, but with the crucifer-pathogenic tobamoviruses by the remainder of its genome, suggesting that it is the progeny of a recombinant. For four of five genomic regions, subgroup 1 and 3 genomes were equidistant from a subgroup 2 genome chosen for comparison, suggesting uniform rates of evolution. A phylogenetic tree of plant families based on the tobamoviruses they harbor was congruent with that based on rubisco sequences but had a different root, suggesting that codivergence was tempered by rare events of viruses of one family colonizing another family. The proposed subgroup 3 viruses probably have an origin of virion assembly in the movement protein gene, a large (25-codon) overlap of movement and coat protein open reading frames, and a comparably shorter genome. Codon-position- dependent base compositions and codon prevalences suggested that the coat protein frame of the overlap region was ancestral. Bootstrapped parsimony analysis of the nucleotides in the overlap region and of the sequences translated from the -1 frame (the subgroup 3 movement protein frame) of this region produced trees inconsistent with those deduced from other regions. The results are consistent with a model in which a no or short overlap organization was ancestral. Despite encoding of subgroup 2 and 3 movement protein C-termini by nonhomologous nucleotides, weak similarities between their amino acid sequences suggested convergent sequence evolution.      

Unprogrammed Deworming in the Kibera Slum,Nairobi: Implications for Control of Soil-Transmitted Helminthiases

BackgroundPrograms for control of soil-transmitted helminth (STH) infections are increasingly evaluating national mass drug administration (MDA) interventions. However, “unprogrammed deworming” (receipt of deworming drugs outside of nationally-run STH control programs) occurs frequently. Failure to account for these activities may compromise evaluations of MDA effectiveness.MethodsWe used a cross-sectional study design to evaluate STH infection and unprogrammed deworming among infants (aged 6–11 months), preschool-aged children (PSAC, aged 1–4 years), and school-aged children (SAC, aged 5–14 years) in Kibera, Kenya, an informal settlement not currently receiving nationally-run MDA for STH. STH infection was assessed by triplicate Kato-Katz. We asked heads of households with randomly-selected children about past-year receipt and source(s) of deworming drugs. Local non-governmental organizations (NGOs) and school staff participating in school-based deworming were interviewed to collect information on drug coverage.ResultsOf 679 children (18 infants, 184 PSAC, and 477 SAC) evaluated, 377 (55%) reported receiving at least one unprogrammed deworming treatment during the past year. PSAC primarily received treatments from chemists (48.3%) or healthcare centers (37.7%); SAC most commonly received treatments at school (55.0%). Four NGOs reported past-year deworming activities at 47 of >150 schools attended by children in our study area. Past-year deworming was negatively associated with any-STH infection (34.8% vs 45.4%, p = 0.005). SAC whose most recent deworming medication was sourced from a chemist were more often infected with Trichuris (38.0%) than those who received their most recent treatment from a health center (17.3%) or school (23.1%) (p = 0.05).ConclusionUnprogrammed deworming was received by more than half of children in our study area, from multiple sources. Both individual-level treatment and unprogrammed preventive chemotherapy may serve an important public health function, particularly in the absence of programmed deworming; however, they may also lead to an overestimation of programmed MDA effectiveness. A standardized, validated tool is needed to assess unprogrammed deworming.     

Use of the tac promoter and lacIq for the controlled expression of Zymomonas mobilis fermentative genes in Escherichia coli and Zymomonas mobilis.

The Zymomonas mobilis genes encoding alcohol dehydrogenase I (adhA), alcohol dehydrogenase II (adhB), and pyruvate decarboxylase (pdc) were overexpressed in Escherichia coli and Z. mobilis by using a broad-host-range vector containing the tac promoter and the lacIq repressor gene. Maximal IPTG (isopropyl-beta-D-thiogalactopyranoside) induction of these plasmid-borne genes in Z. mobilis resulted in a 35-fold increase in alcohol dehydrogenase I activity, a 16.7-fold increase in alcohol dehydrogenase II activity, and a 6.3-fold increase in pyruvate decarboxylase activity. Small changes in the activities of these enzymes did not affect glycolytic flux in cells which are at maximal metabolic activity, indicating that flux under these conditions is controlled at some other point in metabolism. Expression of adhA, adhB, or pdc at high specific activities (above 8 IU/mg of cell protein) resulted in a decrease in glycolytic flux (negative flux control coefficients), which was most pronounced for pyruvate decarboxylase. Growth rate and flux are imperfectly coupled in this organism. Neither a twofold increase in flux nor a 50% decline from maximal flux caused any immediate change in growth rate. Thus, the rates of biosynthesis and growth in this organism are not limited by energy generation in rich medium.     

Sucrose phosphate synthase, a key enzyme for sucrose biosynthesis in plants: protein purification from corn leaves and immunological detection

We have purified the protein for the enzyme sucrose phosphate synthase (SPS) from corn (Zea mays) leaves. Partially purified SPS protein was used to generate specific monoclonal antibodies. The following immunoaffinity chromatography allowed the isolation of pure SPS protein. The apparent molecular mass of the SPS polypeptide is 138 kilodaltons. By immunoblot, an SPS antigen was found to accumulate in mature leaves. SPS protein levels remain constant during the day/night cycle. The observed diurnal fluctuation of extractable enzyme activity, therefore, must be caused by modification of the specific activity of SPS in vivo.     

EXTENSIVE CHROMOSOMAL DIVERGENCE WITHIN A SINGLE RIVER BASIN IN THE GOODEID FISH,ILYODON FURCIDENS

Extensive variation in the number of metacentric chromosomes exists among populations of the viviparous goodeid fish, Ilyodon furcidens, in the Río Coahuayana basin of south central Mexico (states of Colima and Jalisco). The variation can be divided, somewhat arbitrarily, into four “cytotypes” with 0-2, 0-4, 6 and 10-16 metacentrics. Of these, the first, shared with the closely adjacent Río Armería and similar to other species of Ilyodon, is probably ancestral. The wholly non-Robertsonian nature of the variation and its extent appear to be unprecedented among teleosts, but its uniqueness is difficult to evaulate because fish chromosome data in general may be biased toward both monomorphism and Robertsonian variation. Variation is evident with all cytotypes but has been well characterized for only a single population of the 0-4M cytotype. That population, unlike most of the others, consists of two interbreeding morphs which differ in mouth width. The variation is heterogeneously distributed between the morphs; the significance of this observation is not yet clear. The distribution of the cytotypes is approximately clinal with respect to the number of metacentric chromosomes. Although the cline may be a direct response to some gradient in selection intensity, the possibility that it is the result of secondary contact of previously isolated populations, fostered by tributary transfer, is real. Allozyme comparisons reveal minimal genic divergence among the cytotypes. There are no fixed allelic differences, and the average unbiased genetic distance between the two extreme cytotypes is 0.042. Gene diversity analysis indicates that an average of less than 3% of the total variation (H_T = 0.072) is partitioned among cytotypes; about 24% is partitioned among populations within cytotypes. Genic and chromosomal divergence in Ilyodon are clearly uncoupled. Laboratory F₁, backcross, and F₂ intercytotype hybrids are fully viable, and are indistinguishable in fertility from our stocks derived from single populations. F₃ intercytotype hybrids are also fully viable but have not yet been tested for fertility. This suggests that, during the course of chromosomal evolution, single rearrangement heterozygotes were not appreciably negatively heterotic, even though the rearrangements are probably pericentric inversions. The combined data suggest that the chromosome rearrangements, even in multiple form, do not function as significant isolating mechanisms. Chromosomal evolution in Ilyodon, though quite marked, has apparently not fostered speciation.     

Substructural specificity and polyvalent carbohydrate recognition by the Entamoeba histolytica and rat hepatic N- acetylgalactosamine/galactose lectins

Both the Entamoeba histolytica lectin, a virulence factor for the causative agent of amebiasis, and the mammalian hepatic lectin bind to N-acetylgalactosamine (GalNAc) and galactose (Gal) nonreducing termini on oligosaccharides, with preference for GalNAc. Polyvalent GalNAc- derivatized neoglycoproteins have >1000-fold enhanced binding affinity for both lectins (Adler,P., Wood,S.J., Lee,Y.C., Lee,R.T., Petri,W.A.,Jr. and Schnaar,R.L.,1995, J. Biol. Chem ., 270, 5164-5171). Substructural specificity studies revealed that the 3-OH and 4-OH groups of GalNAc were required for binding to both lectins, whereas only the E.histolytica lectin required the 6-OH group. Whereas GalNAc binds with 4-fold lower affinity to the E.histolytica lectin than to the mammalian hepatic lectin, galactosamine and N-benzoyl galactosamine bind with higher affinity to the E. histolytica lectin. Therefore, a synthetic scheme for converting polyamine carriers to poly-N-acyl galactosamine derivatives (linked through the galactosamine primary amino group) was developed to test whether such ligands would bind the E.histolytica lectin with high specificity and high affinity. Contrary to expectations, polyvalent derivatives including GalN6lys5, GalN4desmosine, GalN4StarburstTMdendrimer, and GalN8StarburstTMdendrimer demonstrated highly enhanced binding to the mammalian hepatic lectin but little or no enhancement of binding to the E.histolytica lectin. We propose that the mammalian hepatic lectin binds with greatest affinity to GalNAc "miniclusters," which mimic branched termini of N-linked oligosaccharides, whereas the E.histolytica lectin binds most effectively to "maxiclusters," which may mimic more widely spaced GalNAc residues on intestinal mucins.