Viral and Insect Genes that Inhibit the Immune System and Methods of Use Thereof

Viral, endoparasitoid and/or host genes that specifically inhibit the immune response of insect pests, useful for broadening the host range of insect viruses. Symbiont viruses of insect pests are genetically modified to express immune-suppressing proteins or biologically active fragments thereof and, optionally toxins, to increase the virus host range and/or improve the efficacy of insect pathogens

Genome-wide nucleosome mapping of Plasmodium falciparum reveals histone-rich coding and histone-poor intergenic regions and chromatin remodeling of core and subtelomeric genes

<p>Abstract</p> <p>Background</p> <p>Epigenetic modifications of histones and regulation of chromatin structure have been implicated in regulation of virulence gene families in <it>P. falciparum</it>. To better understand chromatin-mediated gene regulation, we used a high-density oligonucleotide microarray to map the position and enrichment of nucleosomes across the entire genome of <it>P. falciparum </it>at three time points of the intra-erythrocytic developmental cycle (IDC) in vitro. We used an unmodified histone H4 antibody for chromatin immunoprecipitation of nucleosome-bound DNA.</p> <p>Results</p> <p>We observed generally low nucleosomal occupancy of intergenic regions and higher occupancy of protein coding regions. In contract to the overall small fluctuation of nucleosomal occupancy in most coding regions throughout the IDC, subtelomeric genes encoding surface proteins such as <it>var </it>and <it>rif</it>, as well as some core chromosomal genes such as transcription factors, showed large changes in chromatin structure. Telomeres harbored a region with the highest nucleosomal occupancy of the genome and also exhibited large changes with higher nucleosomal occupancy at schizont stages. While many of these subtelomeric genes were previously shown to be modified by H3K9 trimethylation, we also identified some housekeeping genes in core chromosome regions that showed extensive changes in chromatin structure but do not contain this modification. tRNA and basal transcription factor genes showed low nucleosomal occupancy at all times, suggesting of an open chromatin structure that might be permissive for constitutively high levels of expression. Generally, nucleosomal occupancy was not correlated with the steady-state mRNA levels. Several <it>var </it>genes were exceptions: the <it>var </it>gene with the highest expression level showed the lowest nucleosomal occupancy, and selection of parasites for <it>var2CSA </it>expression resulted in lower nucleosomal occupancy at the <it>var2CSA </it>locus. We identified nucleosome-free regions in intergenic regions that may serve as transcription start sites or transcription factor binding sites. Using the nucleosomal occupancy data as the baseline, we further mapped the genome-wide enrichment of H3K9 acetylation and detected general enrichment of this mark in intergenic regions.</p> <p>Conclusions</p> <p>These data on nucleosome enrichment changes add to our understanding of the influence of chromatin structure on the regulation of gene expression. Histones are generally enriched in coding regions, and relatively poor in intergenic regions. Histone enrichment patterns allow for identification of new putative gene-coding regions. Most genes do not show correlation between chromatin structure and steady-state mRNA levels, indicating the dominant roles of other regulatory mechanisms. We present a genome-wide nucleosomal occupancy map, which can be used as a reference for future experiments of histone modification mapping.</p

Molecular interactions between parasite and mosquito during midgut invasion as targets to block malaria transmission

Despite considerable effort, malaria remains a major public health burden. Malaria is caused by five Plasmodium species and is transmitted to humans via the female Anopheles mosquito. The development of malaria vaccines against the liver and blood stages has been challenging. Therefore, malaria elimination strategies advocate integrated measures, including transmission-blocking approaches. Designing an effective transmission-blocking strategy relies on a sophisticated understanding of the molecular mechanisms governing the interactions between the mosquito midgut molecules and the malaria parasite. Here we review recent advances in the biology of malaria transmission, focusing on molecular interactions between Plasmodium and Anopheles mosquito midgut proteins. We provide an overview of parasite and mosquito proteins that are either targets for drugs currently in clinical trials or candidates of promising transmission-blocking vaccines

Polysaccharides from the Chinese medicinal herb Achyranthes bidentata enhance anti-malarial immunity during Plasmodium yoelii 17XL infection in mice

<p>Abstract</p> <p>Background</p> <p>Clinical immunity to malaria in human populations is developed after repeated exposure to malaria. Regulation and balance of host immune responses may lead to optimal immunity against malaria parasite infection. Polysaccharides (ABPS) derived from the Chinese herb ox knee <it>Achyranthes bidentata </it>possess immuno-modulatory functions. The aim of this study is to use the rodent malaria model <it>Plasmodium yoelii </it>17XL (<it>P. y</it>17XL) to examine whether pretreatment with ABPS will modulate host immunity against malaria infection and improve the outcome of the disease.</p> <p>Methods</p> <p>To determine whether ABPS could modulate immunity against malaria, mice were pretreated with ABPS prior to blood-stage infection by <it>P. y</it>17XL. Host survival and parasitaemia were monitored daily. The effect of pretreatment on host immune responses was studied through the quantitation of cytokines, dendritic cell populations, and natural regulatory T cells (Treg).</p> <p>Results</p> <p>Pretreatment with ABPS prior to infection significantly extended the survival time of mice after <it>P. y</it>17XL infection. At three and five days post-infection, ABPS pretreated mice developed stronger Th1 immune responses against malaria infection with the number of F4/80⁺CD36⁺macrophages and levels of IFN-γ, TNF-α and nitric oxide being significantly higher than in the control group. More importantly, ABPS-treated mice developed more myeloid (CD11c⁺CD11b⁺) and plasmacytoid dendritic cells (CD11c⁺CD45R⁺/B220⁺) than control mice. ABPS pretreatment also resulted in modulated expression of MHC-II, CD86, and especially Toll-like receptor 9 by CD11c⁺dendritic cells. In comparison, pretreatment with ABPS did not alter the number of natural Treg or the production of the anti-inflammatory cytokine IL-10.</p> <p>Conclusion</p> <p>Pretreatment with the immuno-modulatory ABPS selectively enhanced Th1 immune responses to control the proliferation of malaria parasites, and prolonged the survival of mice during subsequent malaria infection.</p

Tryptophan-rich domains of Plasmodium falciparum SURFIN4.2 and Plasmodium vivax PvSTP2 interact with membrane skeleton of red blood cell

Additional file 1: Table S1. Primers for PCR amplification and plasmid construction

Characterization of TgPuf1, a member of the Puf family RNA-binding proteins from Toxoplasma gondii

BACKGROUND: Puf proteins act as translational regulators and affect many cellular processes in a wide range of eukaryotic organisms. Although Puf proteins have been well characterized in many model systems, little is known about the structural and functional characteristics of Puf proteins in the parasite Toxoplasma gondii. METHODS: Using a combination of conventional molecular approaches, we generated endogenous TgPuf1 tagged with hemagglutinin (HA) epitope and investigated the TgPuf1 expression levels and localization in the tachyzoites and bradyzoites. We used RNA Electrophoretic Mobility Shfit Assay (EMSA) to determine whether the recombination TgPuf1 has conserverd RNA binding activity and specificity. RESULTS: TgPuf1 was expressed at a significantly higher level in bradyzoites than in tachyzoites. TgPuf1 protein was predominantly localized within the cytoplasm and showed a much more granular cytoplasmic staining pattern in bradyzoites. The recombinant Puf domain of TgPuf1 showed strong binding affinity to two RNA fragments containing Puf-binding motifs from other organisms as artificial target sequences. However, two point mutations in the core Puf-binding motif resulted in a significant reduction in binding affinity, indicating that TgPuf1 also binds to conserved Puf-binding motif. CONCLUSIONS: TgPuf1 appears to exhibit different expression levels in the tachyzoites and bradyzoites, suggesting that TgPuf1 may function in regulating the proliferation or/and differentiation that are important in providing parasites with the ability to respond rapidly to changes in environmental conditions. This study provides a starting point for elucidating the function of TgPuf1 during parasite development

Plasmodium vivax populations revisited: mitochondrial genomes of temperate strains in Asia suggest ancient population expansion

<p>Abstract</p> <p>Background</p> <p><it>Plasmodium vivax </it>is the most widely distributed human malaria parasite outside of Africa, and its range extends well into the temperate zones. Previous studies provided evidence for vivax population differentiation, but temperate vivax parasites were not well represented in these analyses. Here we address this deficit by using complete mitochondrial (mt) genome sequences to elucidate the broad genetic diversity and population structure of <it>P. vivax </it>from temperate regions in East and Southeast Asia.</p> <p>Results</p> <p>From the complete mtDNA sequences of 99 clinical samples collected in China, Myanmar and Korea, a total of 30 different haplotypes were identified from 26 polymorphic sites. Significant differentiation between different East and Southeast Asian parasite populations was observed except for the comparison between populations from Korea and southern China. Haplotype patterns and structure diversity analysis showed coexistence of two different groups in East Asia, which were genetically related to the Southeast Asian population and Myanmar population, respectively. The demographic history of <it>P. vivax</it>, examined using neutrality tests and mismatch distribution analyses, revealed population expansion events across the entire <it>P. vivax </it>range and the Myanmar population. Bayesian skyline analysis further supported the occurrence of ancient <it>P. vivax </it>population expansion.</p> <p>Conclusions</p> <p>This study provided further resolution of the population structure and evolution of <it>P. vivax</it>, especially in temperate/warm-temperate endemic areas of Asia. The results revealed divergence of the <it>P. vivax </it>populations in temperate regions of China and Korea from other populations. Multiple analyses confirmed ancient population expansion of this parasite. The extensive genetic diversity of the <it>P. vivax </it>populations is consistent with phenotypic plasticity of the parasites, which has implications for malaria control.</p

Household ecology and out-migration among ethnic Karen along the Thai-Myanmar border

Local migration in developing-world settings, particularly among rural populations, is an important yet understudied demographic process. Research on migration in such populations can help us test and inform anthropological and demographic theory. Furthermore, it can lead to a better understanding of modern population distributions and epidemiologic landscapes