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International journal for parasitology [journal]
- Impacts of an endoparasitic copepod, Ismaila belciki, on the reproduction, growth and survivorship of its nudibranch host, Janolus fuscus. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Feb 28.
Copepods from the genus Ismaila are large endoparasites that inhabit the main body cavity and/or cerata of opisthobranch molluscs. These parasites exhibit many life history characteristics typically found in parasitic castrators, yet the actual impact of infection on reproduction, growth or survivorship of the hosts are unknown. On the Oregon (USA) coast, Ismaila belciki can infect over 80% of their hermaphroditic hosts, Janolus fuscus. In laboratory mating experiments, we compared the reproductive output (egg mass weight, number of egg capsules, number of viable embryos) and the gonadal somatic index (GSI) of infected versus uninfected J. fuscus. Infected J. fuscus could produce viable sperm and copulate. Mating with an infected individual did not limit a sea slug's reproductive output. However, infected J. fuscus had significantly lower reproductive output (by 34-54%), producing smaller egg masses with fewer capsules and viable embryos. Infected hosts had significantly lower GSI than their uninfected counterparts, although there was no significant difference in GSI between hosts with single and double infections. By collecting the egg sacs produced by the copepod parasite during experiments, we estimated that 25-34% of the host's reproductive output is usurped by the parasite and re-directed to the parasite's own reproduction. In the laboratory, infection did not alter growth in J. fuscus. However, infection significantly decreased survivorship in mature (but not immature) nudibranch hosts. These results suggest that I. belciki is not a true castrator, but it does reduce the reproductive output of its host and may therefore limit the natural population size of J. fuscus.
- Ostertagia ostertagi macrophage migration inhibitory factor is present in all developmental stages and may cross-regulate host functions through interaction with the host receptor. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Feb 27.
Macrophage migration inhibitory factor (MIF) of Ostertagia ostertagi, an abomasal parasite of cattle, was characterized in the present study. Phylogenetic analysis identified at least three O. ostertagi MIFs (Oos-MIFs), each encoded by a distinct transcript: Oos-MIF-1.1, Oos-MIF-1.2 and Oos-MIF-2. Oos-MIF-2 is only distantly related to Oos-MIF-1s, but has higher sequence similarity with the Caenorhabditis elegans MIF2. Oos-MIF-1.1 and Oos-MIF-1.2 are similar (93%) and thus collectively referred to as Oos-MIF-1 when characterized with immunoassays. Recombinant Oos-MIF-1.1 (rOos-MIF-1.1) is catalytically active as a tautomerase. A mutation (rOos-MIF-1.1P1G) or duplication of Pro1 residue (rOos-MIF-1.1P1+P) resulted in reduced oligomerization and loss of tautomerase activity. The tautomerase activity of rOos-MIF-1.1 was only partially inhibited by ISO-1 but was abrogated by a rOos-MIF-1.1-specific antibody. Oos-MIF-1 was detected in all developmental stages of O. ostertagi, with higher levels in the adult stage; it was also detected in adult worm excretory/secretory (ES) product. Oos-MIF-1 was localized to the hypodermis/muscle, reproductive tract and intestine, but not to the cuticle. rOos-MIF-1.1, but not rOos-MIF-1.1P1G, was able to specifically bind to human CD74, a MIF cell surface receptor, with an affinity comparable with human MIF. Immunostaining indicated that macrophages were able to internalize rOos-MIF-1.1, further supporting receptor-mediated transportation. Herein we also show that rOos-MIF-1.1 inhibited migration of bovine macrophages and restored glucocorticoid-suppressed, lipopolysaccharide (LPS)-induced TNF-α and IL-8 in human and/or bovine macrophages. Given its dual role in self-regulation and molecular mimicry, this secreted parasite protein warrants investigation as a vaccine candidate against O. ostertagi infections in cattle.
- A blood meal-induced Ixodes scapularis tick saliva serpin inhibits trypsin and thrombin, and interferes with platelet aggregation and blood clotting. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Feb 27.
Ixodes scapularis is a medically important tick species that transmits causative agents of important human tick-borne diseases including borreliosis, anaplasmosis and babesiosis. An understanding of how this tick feeds is needed prior to the development of novel methods to protect the human population against tick-borne disease infections. This study characterizes a blood meal-induced I. scapularis (Ixsc) tick saliva serine protease inhibitor (serpin (S)), in-house referred to as IxscS-1E1. The hypothesis that ticks use serpins to evade the host's defense response to tick feeding is based on the assumption that tick serpins inhibit functions of protease mediators of the host's anti-tick defense response. Thus, it is significant that consistent with hallmark characteristics of inhibitory serpins, Pichia pastoris-expressed recombinant IxscS-1E1 (rIxscS-1E1) can trap thrombin and trypsin in SDS- and heat-stable complexes, and reduce the activity of the two proteases in a dose-responsive manner. Additionally, rIxscS-1E1 also inhibited, but did not apparently form detectable complexes with, cathepsin G and factor Xa. Our data also show that rIxscS-1E1 may not inhibit chymotrypsin, kallikrein, chymase, plasmin, elastase and papain even at a much higher rIxscS-1E1 concentration. Native IxscS-1E1 potentially plays a role(s) in facilitating I. scapularis tick evasion of the host's hemostatic defense as revealed by the ability of rIxscS-1E1 to inhibit adenosine diphosphate (ADP)- and thrombin-activated platelet aggregation, and delay activated partial prothrombin time (APTT) and thrombin time (TT) plasma clotting in a dose-responsive manner. We conclude that native IxscS-1E1 is part of the tick saliva protein complex that mediates its anti-hemostatic, and potentially inflammatory, functions by inhibiting the actions of thrombin, trypsin and other yet unknown trypsin-like proteases at the tick-host interface.
- Apicoplast acetyl Co-A carboxylase of the human malaria parasite is not targeted by cyclohexanedione herbicides. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Feb 25.
Malaria parasites retain a relict plastid (apicoplast) from a photosynthetic ancestor. The apicoplast is a useful drug target but the specificity of compounds believed to target apicoplast fatty acid biosynthesis has become uncertain, as this pathway is not essential in blood stages of the parasite. Herbicides that inhibit the plastid acetyl Co-A carboxylase of plants also kill Plasmodium falciparum in vitro, but their mode of action remains undefined. We characterised the gene for acetyl Co-A carboxylase in P. falciparum. The P. falciparum acetyl-CoA carboxylase gene product is expressed in blood stage parasites and accumulates in the apicoplast. Ablation of the gene did not render parasites insensitive to herbicides, suggesting that these compounds are acting off-target in blood stages of P. falciparum.
- Enhancing a search for traditional medicinal plants with anthelmintic action by using wild type and stress reporter Caenorhabditis elegans strains as screening tools. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Feb 26.
Traditional healers in Sarawak, Malaysia, use plants such as Picria fel-terrae, Linariantha bicolor and Lansium domesticum to treat gastrointestinal infections. This study aimed to test whether their nematocidal activities could be confirmed in vitro using highly standardised Caenorhabditis elegans models. We applied eight different ethanol solubilised plant extracts and two commercial anthelmintic drugs to larval and adult stages of C. elegans in vitro. Seven C. elegans strains were evaluated, one wild type and six strains with GFP-tagged stress response pathways to help characterise and compare the pathways affected by plant extracts. Our in vitro screen confirmed that both of the commercial anthelmintic drugs and five of the eight traditionally used plant extracts had significant nematocidal activity against both larval and adult C. elegans. The most effective extracts were from P. fel-terrae. The plant extracts triggered different stress response pathways from the commercial anthelmintic drugs. This study showed that using traditional knowledge of plant medicinal properties in combination with a C. elegans in vitro screen provided a rapid and economical test with a high hit rate compared with the random screening of plants for nematocidal activities. The use of transgenic C. elegans strains may allow this approach to be refined further to investigate the mode of action of active extracts.
- Binding of von Willebrand factor and plasma proteins to the eggshell of Schistosoma mansoni. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Feb 18.
Schistosoma mansoni eggs have to cross the endothelium and intestinal wall to leave the host and continue the life cycle. Mechanisms involved in this essential step are largely unknown. Here we describe direct binding to the S. mansoni eggshell of von Willebrand factor and other plasma proteins involved in haemostasis. Using deletion-mutants, we demonstrated that it is the A1 domain of von Willebrand factor that binds to the eggshell. Our results suggest that binding of plasma proteins to the eggshell promotes binding to the endothelium, initiating the passage of the egg through the blood-vessel wall to be excreted in the end.
- Molecular insight into systematics, host associations, life cycles and geographic distribution of the nematode family Rhabdiasidae. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Feb 19.
Rhabdiasidae Railliet, 1915 is a globally distributed group of up to 100 known species of nematodes parasitic in amphibians and reptiles. This work presents the results of a molecular phylogenetic analysis of 36 species of Rhabdiasidae from reptiles and amphibians from six continents. New DNA sequences encompassing partial 18S rDNA, ITS1, 5.8S rDNA, ITS2 and partial 28S rDNA regions of nuclear ribosomal DNA were obtained from 27 species and pre-existing sequences for nine species were incorporated. The broad taxonomic, host and geographical coverage of the specimens allowed us to address long-standing questions in rhabdiasid systematics, evolution, geographic distribution, and patterns of host association. Our analysis demonstrated that rhabdiasids parasitic in snakes are an independent genus sister to the rest of the Rhabdiasidae, a status supported by life cycle data. Based on the combined evidence of molecular phylogeny, morphology and life cycle characteristics, a new genus Serpentirhabdias gen. nov. with the type species Serpentirhabdias elaphe (Sharpilo, 1976) comb. nov. is established. The phylogeny supports the monophyly of Entomelas Travassos, 1930, Pneumonema Johnston, 1916 and the largest genus of the family, Rhabdias Stiles and Hassall, 1905. DNA sequence comparisons demonstrate the presence of more than one species in the previously monotypic Pneumonema from Australian scincid lizards. The distribution of some morphological characters in the genus Rhabdias shows little consistency within the phylogenetic tree topology, in particular the apical structures widely used in rhabdiasid systematics. Our data suggest that some of the characters, while valuable for species differentiation, are not appropriate for differentiation among higher taxa and are of limited phylogenetic utility. Rhabdias is the only genus with a cosmopolitan distribution, but some of the lineages within Rhabdias are distributed on a single continent or a group of adjacent zoogeographical regions. Serpentirhabdias, Entomelas and Pneumonema show rather strict specificity to their host groups. The evolution of the Rhabdiasidae clearly included multiple host switching events among different orders and families of amphibians as well as switching between amphibians and squamatan reptiles. Only a few smaller lineages of Rhabdias demonstrate relatively strict associations with a certain group of hosts.
- Pallial mucus of the oyster Crassostrea virginica regulates the expression of putative virulence genes of its pathogen Perkinsus marinus. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Feb 18.
Perkinsus marinus is a pathogen responsible for severe mortalities of the eastern oyster Crassostrea virginica along the East and Gulf coasts of the United States. When cultivated, the pathogenicity of this microorganism decreases significantly, hampering the study of its virulence factors. Recent investigations have shown a significant increase of the in vivo virulence of P. marinus exposed to oyster pallial mucus. In the current study, we investigated the effect of pallial mucus on P. marinus gene expression compared with cultures supplemented with oyster digestive extracts or with un-supplemented cultures. In parallel, parasite cells cultured under these three conditions were used to challenge oysters and to assess virulence in vivo. Perkinsus marinus mRNA sequencing was performed on an Illumina GAIIX sequencer and data were analysed using the Tuxedo RNAseq suite for mapping against the draft P. marinus genome and for differential expression analysis. Results showed that exposure of P. marinus to mucus induces significant regulation of nearly 3,600 transcripts, many of which are considered as putative virulence factors. Pallial mucus is suspected to mimic internal host conditions, thereby preparing the pathogen to overcome defense factors before invasion. This hypothesis is supported by significant regulation in several antioxidant proteins, heat shock proteins, protease inhibitors and proteasome subunits. In addition, mucus exposure induced the modulation of several genes known to affect immunity and apoptosis in vertebrates and invertebrates. Several proteases (proteolysis) and merozoite surface proteins (cell recognition) were also modulated. Overall, these results provide a baseline for targeted, in depth analysis of candidate virulence factors in P. marinus.
- Evaluating faecal egg count reduction using a specifically designed package "eggCounts" in R and a user friendly web interface. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Feb 17.
The seemingly straightforward task of analysing faecal egg counts resulting from laboratory procedures such as the McMaster technique has, in reality, a number of complexities. These include Poisson errors in the counting technique which result from eggs being randomly distributed in well mixed faecal samples. In addition, counts between animals in a single experimental or observational group are nearly always over-dispersed. We describe the R package "eggCounts" that we have developed that incorporates both sampling error and over-dispersion between animals to calculate the true egg counts in samples of faeces, the probability distribution of the true counts and summary statistics such as the 95% uncertainty intervals. Based on a hierarchical Bayesian framework, the software will also rigorously estimate the percentage reduction of faecal egg counts and the 95% uncertainty intervals of data generated by a faecal egg count reduction test. We have also developed a user friendly web interface that can be used by those with limited knowledge of the R statistical computing environment. We illustrate the package with three simulated data sets of faecal egg count reduction experiments.
- A review of global diversity in avian haemosporidians (Plasmodium and Haemoproteus: Haemosporida): new insights from molecular data. [JOURNAL ARTICLE]
- Int J Parasitol 2014 Feb 18.
Biogeographic patterns of parasite diversity are useful for determining how host-parasite interactions can influence speciation. However, variation in methodologies and sampling effort can skew diversity estimates. Avian haemosporidians are vector-transmitted blood parasites represented by over 1300 unique genetic lineages spread across over 40 countries. We used a global database of lineage distributions for two avian haemosporidian genera, Plasmodium and Haemoproteus, to test for congruence of diversity among haemosporidians and their avian hosts across 13 geographic regions. We demonstrated that avian haemosporidians exhibit similar diversity patterns to their avian hosts; however, specific patterns differ between genera. Haemoproteus spp. diversity estimates were significantly higher than those of Plasmodium spp. in all areas where the genera co-occurred, apart from the Plasmodium spp.-rich region of South America. The geographic distributions of parasite genera also differed, with Haemoproteus spp. absent from the majority of oceanic regions while Plasmodium spp. were cosmopolitan. These findings suggest fundamental differences in the way avian haemosporidians diverge and colonise new communities. Nevertheless, a review of the literature suggests that accurate estimates of avian haemosporidian diversity patterns are limited by (i) a concentration of sampling towards passerines from Europe and North America, (ii) a frequent failure to include microscopic techniques together with molecular screening and (iii) a paucity of studies investigating distributions across vector hosts.