Galectin-2 suppresses nematode development by binding to the invertebrate-specific galactoseß1-4fucose glyco-epitope.

Galactoseß1-4Fucose (GalFuc) is a unique disaccharide found in invertebrates including nematodes. A fungal galectin CGL2 suppresses nematode development by recognizing the galactoseß1-4fucose epitope. The Caenorhabditis elegans galectin LEC-6 recognizes it as an endogenous ligand and the Glu67 residue of LEC-6 is responsible for this interaction. We found that mammalian galectin-2 (Gal-2) also has a comparable glutamate residue, Glu52. In the present study, we investigated the potential nematode-suppressing activity of Gal-2 using C. elegans as a model and focusing on Gal-2 binding to the GalFuc epitope. Gal-2 suppressed C. elegans development whereas its E52D mutant (Glu52 substituted by Asp), galectin-1 and galectin-3 had little effect on C. elegans growth. Lectin-staining using fluorescently-labeled Gal-2 revealed that, like CGL2, it specifically binds to the C. elegans intestine. Natural C. elegans glycoconjugates were specifically bound by immobilized Gal-2. Western blotting with anti-GalFuc antibody showed that the bound glycoconjugates had the GalFuc epitope. Frontal affinity chromatography with pyridylamine-labeled C. elegans N-glycans disclosed that Gal-2 (but not its E52D mutant) recognizes the GalFuc epitope. Gal-2 also binds to the GalFuc-bearing glycoconjugates of Ascaris and the GalFuc epitope is present in the parasitic nematodes Nippostrongylus brasiliensis and Brugia pahangi. These results indicate that Gal-2 suppresses C. elegans development by binding to its GalFuc epitope. The findings also imply that Gal-2 may prevent infestations of various parasitic nematodes bearing the GalFuc epitope.

Effect of reagents used during detection and quantification of Ascaris suum in environmental samples on egg viability.

Soil-transmitted helminths (STHs) are a major health concern globally. Infection is mostly through contact with contaminated water, food or soil. Therefore to break the cycle of viable transmission STH eggs must be quantitatively detected in the environment. The effect of different reagents on the viability of Ascaris suum eggs during laboratory detection and quantification was assessed and different incubation solutions compared. Sulphuric acid gave a slightly higher recovery percentage of viable eggs (91.2%) than distilled water (90.0%) and 0.5% formalin (87.6%), although the difference was not statistically significant (p > 0.05). Acetoacetic acid, ethyl acetate, ammonium bicarbonate, zinc sulphate, magnesium sulphate and Tween 80, are reagents widely used in test protocols for the detection and quantification of STH eggs. Eggs were exposed to these reagents for different time durations. Acetoacetic acid resulted in the highest loss of viability (3.4 ± 0.7% viable), while magnesium sulphate resulted in the least effect (88.5 ± 1.2% viable). In conclusion the use of the selected reagents in the detection of these eggs was found to affect the viability of exposed eggs, especially during prolonged exposures. Therefore we recommended that eggs be exposed for ≤5 minutes, to reduce the risk of viability loss.

Viability assessment of Ascaris suum eggs stained with fluorescent dyes using digital colorimetric analysis.

The aim of the study was to develop a method for the colorimetric evaluation of nematode eggs using appropriate instruments. The materials for the study were live and dead (inactivated) eggs of the Ascaris suum. Viability of the eggs was assessed using four different kits for fluorescent staining (for each technique, a series of photos were taken). Images of stained eggs were analysed using graphic software with RGB (red-green-blue) function. The viability of the eggs was assessed according to the relative positions of the distributions of colour intensities of live or dead eggs - distributions area's overlap index (DAOI), and distributions area's separation index (DASI) were calculated. Computer analysis of the intensity of green colour was not satisfactory. However, analysis of images in the spectrum of red colour proved useful for the effective differentiation between live or dead eggs. The best parameters were observed using the Annexin V FITC Apoptosis Detection Kit (DASI = 41 and 67). The investigation confirmed the usefulness of fluorescent dyes used in conjunction with digital analysis for the assessment of the viability of A. suum eggs. The use of computer software allowed a better objectivity of the assessment, especially in the case of doubtful staining.

Differential Chromosomal Localization of Centromeric Histone CENP-A Contributes to Nematode Programmed DNA Elimination.

The stability of the genome is paramount to organisms. However, diverse eukaryotes carry out programmed DNA elimination in which portions or entire chromsomes are lost in early development or during sex determination. During early development of the parasitic nematode, Ascaris suum, 13% of the genome is eliminated. How different genomic segments are reproducibly retained or discarded is unknown. Here, we show that centromeric histone CENP-A localization plays a key role in this process. We show that Ascaris chromosomes are holocentric during germline mitoses, with CENP-A distributed along their length. Prior to DNA elimination in the four-cell embryo, CENP-A is significantly diminished in chromosome regions that will be lost. This leads to the absence of kinetochores and microtubule attachment sites necessary for chromosome segregation, resulting in loss of these regions upon mitosis. Our data suggest that changes in CENP-A localization specify which portions of chromosomes will be lost during programmed DNA elimination.

Effects of some pesticides on development of Ascaris suum eggs.

To evaluate the effects of pesticides to parasite eggs, Ascaris suum eggs were incubated with 5 different pesticides (1:1,500-1:2,000 dilutions of 2% emamectin benzoate, 5% spinetoram, 5% indoxacarb, 1% deltamethrin, and 5% flufenoxuron; all v/v) at 20℃ for 6 weeks, and microscopically evaluated the egg survival and development on a weekly basis. The survival rate of A. suum eggs incubated in normal saline (control eggs) was 90±3% at 6 weeks. However, the survival rates of eggs treated with pesticides were 75-85% at this time, thus significantly lower than the control value. Larval development in control eggs commenced at 3 weeks, and 73±3% of eggs had internal larvae at 6 weeks. Larvae were evident in pesticide-treated eggs at 3-4 weeks, and the proportions of eggs carrying larvae at 6 weeks (36±3%-54±3%) were significantly lower than that of the control group. Thus, pesticides tested at levels similar to those used in agricultural practices exhibited low-level ovicidal activity and delayed embryogenesis of A. suum eggs, although some differences were evident among the tested pesticides.

Cloning and characterization of hypoxia-inducible factor-1 subunits from Ascaris suum - a parasitic nematode highly adapted to changes of oxygen conditions during its life cycle.

The parasitic nematode Ascaris suum successfully adapts to a significant decrease in oxygen availability during its life cycle by altering its metabolic system dramatically. However, little is known about the regulatory mechanisms of adaptation to hypoxic environments in A. suum. In multicellular organisms, hypoxia-inducible factor-1 (HIF-1), a heterodimeric transcription factor composed of HIF-1α and HIF-1ß subunits, is a master regulator of genes involved in adaptation to hypoxia. In the present study, cDNAs encoding HIF-1α and HIF-1ß were cloned from A. suum and characterized. The full-length A. suum hif-1α and hif-1ß cDNAs contain open reading frames encoding proteins with 832 and 436 amino acids, respectively. In the deduced amino acid sequences of A. suum HIF-1α and HIF-1ß, functional domains essential for DNA-binding, dimerization, and oxygen-dependent prolyl hydroxylation were conserved. The interaction between A. suum HIF-1α and HIF-1ß was confirmed by the yeast two-hybrid assay. Both A. suum hif-1α and hif-1ß mRNAs were expressed at all stages examined (fertilized eggs, third-stage larvae, lung-stage larvae, young adult worms, and adult muscle tissue), and most abundantly in the aerobic free-living third-stage larvae, followed by a gradual decrease after infection of the host. hif-1 mRNA transcription was not sensitive to the oxygen environment in either third-stage larvae or adult worms (muscle tissue), and was regulated in a stage-specific manner. High expression of hif-1 mRNAs in third-stage larvae suggests its contribution to pre-adaptation to a hypoxic environment after infection of their host. Sequence analysis of 5'-upstream regions of mitochondrial complex II (succinate-ubiquinone reductase/quinol-fumarate reductase) genes, which show stage-specific expression and play an important role in oxygen adaptation during the life cycle, revealed that all subunits except for the adult-type flavoprotein subunit (Fp) possess putative hypoxia-responsive elements (HREs), suggesting that they are hif-1 target genes.

Viability of Ascaris suum eggs in stored raw and separated liquid slurry.

Separation of pig slurry into solid and liquid fractions is gaining importance as a way to manage increasing volumes of slurry. In contrast to solid manure and slurry, little is known about pathogen survival in separated liquid slurry. The viability of Ascaris suum eggs, a conservative indicator of fecal pollution, and its association with ammonia was investigated in separated liquid slurry in comparison with raw slurry. For this purpose nylon bags with 6000 eggs each were placed in 1 litre bottles containing one of the two fractions for 308 days at 5 °C or 25 °C. Initial analysis of helminth eggs in the separated liquid slurry revealed 47 Ascaris eggs per gramme. At 25 °C, egg viability declined to zero with a similar trend in both raw slurry and the separated liquid slurry by day 308, a time when at 5 °C 88% and 42% of the eggs were still viable in separated liquid slurry and raw slurry, respectively. The poorer survival at 25 °C was correlated with high ammonia contents in the range of 7.9-22.4 mM in raw slurry and 7.3-23.2 mM in liquid slurry compared to 3.2-9.5 mM in raw slurry and 2.6-9.5 mM in liquid slurry stored at 5 °C. The study demonstrates that at 5 °C, A. suum eggs have a higher viability in separated liquid slurry as compared to raw slurry. The hygiene aspect of this needs to be further investigated when separated liquid slurry is used to fertilize pastures or crops.

Effect of temperature on embryonation of Ascaris suum eggs in an environmental chamber.

The influence of temperature on the development and embryonation of Ascaris suum eggs was studied using coarse sand medium in an environmental chamber with 50% humidity. The time required for development and embryonation of eggs was examined under 3 different temperature conditions, 5°C, 25°C, and 35°C. A. suum eggs did not develop over 1 month at the temperature of 5°C. However, other temperature conditions, 25°C and 35°C, induced egg development to the 8-cell-stage at days 5-6 after incubation. All eggs examined developed to the 8-cell stage at day 6 after incubation in the sand medium at 25°C. The higher temperature, 35°C, slightly accelerated the A. suum egg development compared to 25°C, and the development to the 8-cell stage occurred within day 5 after incubation. The formation of larvae in A. suum eggs at temperatures of 35° and 25°C appeared at days 17 and 19 after incubation, respectively. These findings show that 35° condition shortens the time for the development of A. suum eggs to the 8-cell-stage in comparison to 25°C, and suggest the possibility of accelerated transmission of this parasite, resulting from global warming and ecosystem changes.

Changes in cyclic nucleotides, locomotory behavior, and body length produced by novel endogenous neuropeptides in the parasitic nematode Ascaris suum.

Recent technical advances have rapidly advanced the discovery of novel peptides, as well as the transcripts that encode them, in the parasitic nematode Ascaris suum. Here we report that many of these novel peptides produce profound and varied effects on locomotory behavior and levels of cyclic nucleotides in A. suum. We investigated the effects of 31 endogenous neuropeptides encoded by transcripts afp-1, afp-2, afp-4, afp-6, afp-7, and afp-9-14 (afp: Ascaris FMRFamide-like Precursor protein) on cyclic nucleotide levels, body length and locomotory behavior. Worms were induced to generate anteriorly propagating waveforms, peptides were injected into the pseudocoelomic cavity, and changes in the specific activity (nmol/mg protein) of second messengers cAMP (3'5' cyclic adenosine monophosphate) and cGMP (3'5' cyclic guanosine monophosphate) were determined. Many of these neuropeptides changed the levels of cAMP (both increases and decreases were found), whereas few neuropeptides changed the level of cGMP. A subset of the peptides that lowered cAMP was investigated for effects on the locomotory waveform and on body length. Injection of AF19, or AF34 (afp-13), AF9 (afp-14), AF26 or AF41 (afp-11) caused immediate paralysis and cessation of propagating body waveforms. These neuropeptides also significantly increased body length. In contrast, injection of AF15 (afp-9) reduced the body length, and decreased the amplitude of waves in the body waveform. AF30 (afp-10) produced worms with tight ventral coils. Although injection of neuropeptides encoded by afp-1 (AF3, AF4, AF10 or AF13) produced an increased number of exaggerated body waves, there were no effects on either cAMP or cGMP. By injecting peptides into behaving A. suum, we have provided an initial screen of the effects of novel peptides on several behavioral and biochemical parameters.

The role of Intelectin-2 in resistance to Ascaris suum lung larval burdens in susceptible and resistant mouse strains.

The underlying mechanism of predisposition to Ascaris infection is not yet understood but host genetics are thought to play a fundamental role. We investigated the association between the Intelectin-2 gene and resistance in F2 mice derived from mouse strains known to be susceptible and resistant to infection. Ascaris larvae were isolated from murine lungs and the number of copies of the Intelectin-2 gene was determined in F2 mice. Intelectin-2 gene copy number was not significantly linked to larval burden. In a pilot experiment, the response to infection in parental mice of both sexes was observed in order to address the suitability of female F2 mice. No overall significant sex effect was detected. However, a divergence in resistance/susceptibility status was observed between male and, female hybrid offspring. The responsiveness to Ascaris in mice is likely to be controlled by multiple genes and, despite a unique absence from the susceptible C57BL/6j strain, the Intelectin-2 gene does not play a significant role in resistance. The observed intra-strain variation in larval burden requires further investigation but we hypothesize that it stems from social/dominance hierarchies created by the presence of female mice and possibly subsequent hormonal perturbations that modify the intensity of the immune response.

Ascaris suum: RNAi mediated silencing of enolase gene expression in infective larvae.

Ascaris suum is an important parasite of pigs that causes tremendous economic losses globally to agriculture and animal husbandry annually. RNA interference (RNAi) technology has been described as a successful and useful approach for the elucidation of gene function in parasitic nematodes. In the present study, RNAi was used to silence the expression of a gene encoding enolase in A. suum by soaking infective larvae in double-stranded RNA derived from an EST (representing As-enol-1) selected from an A. suum infective larvae-specific cDNA library. The mRNA levels of RNAi-treated larvae were examined by Reverse-Transcription PCR (RT-PCR) analysis. The survival of RNAi-treated larvae was compared with larvae treated with dsRNA-free culture medium. The effect of enolase depletion on the development of A. suum larvae was assessed by infecting BALB/c mice with RNAi-treated larvae. The results showed that enolase gene expression was silenced completely and the survival rate of the RNAi-treated nematodes was reduced by 20.11% (P<0.01) after soaking for 72 h. Although no significant difference was detected in the numbers of larvae recovered from the liver and lungs of infected mice 4 days post infection, RNAi knockdown of the A. suum enolase mRNA led to significant shorter larvae, indicating that loss of enolase expression may cause delays in larval development.

RNAi-mediated silencing of a novel Ascaris suum gene expression in infective larvae.

In the present study, the potential of RNA interference (RNAi) as a gene silencing tool and the resultant effects on Ascaris suum larval development was examined by targeting a gene (represented by the EST 06G09) specifically expressed in the infective larvae of A. suum. BALB/c mice were infected with RNAi-treated larvae. The results showed that the target gene was silenced after soaking for 72 h, and the survival rate of the RNAi-treated larvae was reduced by 17.25% (P<0.01). A significant difference (P<0.05) was detected in the numbers of larvae collected from the livers and lungs of infected mice 4 days after infection with untreated larvae (164.29 ± 21.51) and RNAi-treated larvae (71.43 ± 14.35). Significant differences (P<0.01) were also found in the body length and width between untreated larvae (480 ± 105.77 µm for length and 23.93 ± 3.72 µm for width) and RNAi-treated larvae (400.57 ± 71.31 µm for length and 20.20 ± 2.43 µm for width). These results show that the gene represented by EST 06G09 may play a role in the development of A. suum larvae.

Genetic influence on the kinetics and associated pathology of the early stage (intestinal-hepatic) migration of Ascaris suum in mice.

The generative mechanism(s) of aggregation and predisposition to Ascaris lumbricoides and A. suum infections in their host population are currently unknown and difficult to elucidate in humans and pigs for ethical/logistical reasons. A recently developed, optimized murine model based on 2 inbred strains, putatively susceptible (C57BL/6j) and resistant (CBA/Ca) to infection, was exploited to elucidate further the basis of the contrasting parasite burdens, most evident at the pulmonary stage. We explored the kinetics of early infection, focusing on the composite lobes of the liver and lung, over the first 8 days in an effort to achieve a more detailed understanding of the larval dispersal over time and the point at which worm burdens diverge. Larval recoveries showed a heterogenous distribution among the lobes of the lungs, being higher in the right lung of both strains, and in the susceptible strain larvae accumulating preferentially in 2 (caudal and middle) of the 4 lobes. Total larval burdens in these 2 lobes were largely responsible for the higher worm burdens in the susceptible strain. While total lung larval recoveries significantly differed between mouse strains, a difference in liver larval burdens was not observed. However, an earlier intense inflammatory response coupled with more rapid tissue repair in the hepatic lobes was observed in CBA/Ca mice, in contrast to C57BL/6j mice, and it is possible that these processes are responsible for restricting onward pulmonary larval migration in the resistant genotype.

Population dynamics of Ascaris suum in trickle-infected pigs.

The population dynamics of Ascaris suum was studied by long-term exposure of pigs to infective eggs. The pigs were experimentally inoculated with 25 A. suum eggs/kg/day, and 7, 8, and 8 pigs were necropsied at weeks 4, 8, and 14 postinoculation (PI), respectively. Despite the fact that the pigs were continuously reinfected, dramatic reductions in numbers of liver lesions (white spots) and migrating lung larvae were observed as a function of time. However, even at the end of the study, a few larvae were able to complete migration, but these larvae seemed unable to mature in the small intestine. Thus, the adult worm population seemed to consist of worms from the first part of the exposure period. The noticeable decrease in number of white spots suggests that the level of exposure is not reflected in the number of white spots in the late phase of a continuous infection. The serum levels of A. suum L3-specific IgG1 and IgA were significantly elevated by week 4 PI, after which the antibody levels declined. The population dynamics and parasite regulating mechanisms are discussed for A. suum in pigs as well as for the closely related species A. lumbricoides in humans.

Ascaris suum cytochrome b5, an adult-specific secretory protein reducing oxygen-avid ferric hemoglobin.

The anaerobic parasitic nematode Ascaris suum has an oxygen-avid hemoglobin in the perienteric fluid, the biological function of which remains elusive. Here, we report that Ascaris cytochrome b5 is expressed specifically in the intestinal parasitic stage and is secreted into the perienteric fluid, thus co-localizing with Ascaris hemoglobin. We also found that cytochrome b5 reduces Ascaris non-functioning ferric methemoglobin more efficiently than mammalian methemoglobin. Furthermore, a computer graphics model of the electron transfer complex between Ascaris cytochrome b5 and Ascaris hemoglobin strongly suggested that these two proteins are physiological redox partners. Nitric oxide has been reported to react easily with oxygen captured in hemoglobin to form nitrate, but not toxic free radicals, which may result in production of methemoglobin for the cytochrome b5 to regenerate functional ferrous hemoglobin. Therefore, our findings suggest that Ascaris cytochrome b5 is a key redox partner of Ascaris hemoglobin, which acts as an antioxidant.

Change of subunit composition of mitochondrial complex II (succinate-ubiquinone reductase/quinol-fumarate reductase) in Ascaris suum during the migration in the experimental host.

The mitochondrial metabolic pathway of the parasitic nematode Ascaris suum changes dramatically during its life cycle, to adapt to changes in the environmental oxygen concentration. We previously showed that A. suum mitochondria express stage-specific isoforms of complex II (succinate-ubiquinone reductase: SQR/quinol-fumarate reductase: QFR). The flavoprotein (Fp) and small subunit of cytochrome b (CybS) in adult complex II differ from those of infective third stage larval (L3) complex II. However, there is no difference in the iron-sulfur cluster (Ip) or the large subunit of cytochrome b (CybL) between adult and L3 isoforms of complex II. In the present study, to clarify the changes that occur in the respiratory chain of A. suum larvae during their migration in the host, we examined enzymatic activity, quinone content and complex II subunit composition in mitochondria of lung stage L3 (LL3) A. suum larvae. LL3 mitochondria showed higher QFR activity ( approximately 160 nmol/min/mg) than mitochondria of A. suum at other stages (L3: approximately 80 nmol/min/mg; adult: approximately 70 nmol/min/mg). Ubiquinone content in LL3 mitochondria was more abundant than rhodoquinone ( approximately 1.8 nmol/mg versus approximately 0.9 nmol/mg). Interestingly, the results of two-dimensional bule-native/sodium dodecyl sulfate polyacrylamide gel electrophoresis analyses showed that LL3 mitochondria contained larval Fp (Fp(L)) and adult Fp (Fp(A)) at a ratio of 1:0.56, and that most LL3 CybS subunits were of the adult form (CybS(A)). This clearly indicates that the rearrangement of complex II begins with a change in the isoform of the anchor CybS subunit, followed by a similar change in the Fp subunit.

Helminths of wild boar in the isolated population close to the northern border of its habitat area.

One hundred wild boars (Sus scrofa) from a geographically isolated population on the island Saaremaa of western Estonia were examined for visceral helminths. Seven helminth species, Metastrongylus pudendotectus, M. salmi, M. elongatus, Ascaris suum, Trichuris suis, Dicrocoelium dendriticum and Taenia hydatigena larva, were found. The predominant helminths discovered were lung nematodes (prevalence 82%, mean intensity 96.2 per animal). A significant negative correlation was observed between the weight of wild boars and the number of lungworms and helminth species. The number of helminth species found in the wild boar population on the island was lower compared to that of the adjacent mainland.

[Effects of some species of hydrocoles on the development of ascarid eggs].

The study established that aquatic plants differently affected the development of ascarid eggs. Some species of algae exerted a damaging effect on ascarid eggs only at early stages of embryogenesis while others did at its late stages, but some species did not produce any noticeable effect on the development of the eggs. A great difference was found in the development of ascarid eggs in different seasons. Gas exchange conditions were ascertained to affect the development of ascarid eggs. Analysis of the effect of egg lysozyme versus mollusk one on ascarid embryogenesis demonstrated that the latter had a more pronounced antiparasitic activity.

A real-time PCR method for quantifying viable ascaris eggs using the first internally transcribed spacer region of ribosomal DNA.

Worldwide, 1.4 billion people are infected with the intestinal worm Ascaris lumbricoides. As a result, Ascaris eggs are commonly found in wastewater and sludges. The current microscopy method for detecting viable Ascaris eggs is time- and labor-intensive. The goal of this study was to develop a real-time quantitative PCR (qPCR) method to determine the levels of total and viable Ascaris eggs in laboratory solutions using the first internally transcribed spacer (ITS-1) region of ribosomal DNA (rDNA) and rRNA. ITS-1 rDNA levels were proportional to Ascaris egg cell numbers, increasing as eggs developed from single cells to mature larvae and ultimately reaching a constant level per egg. Treatments causing >99% inactivation (high heat, moderate heat, ammonia, and UV) eliminated this increase in ITS-1 rDNA levels and caused decreases that were dependent on the treatment type. By taking advantage of this difference in ITS-1 rDNA level between viable, larvated eggs and inactivated, single-celled eggs, qPCR results were used to develop inactivation profiles for the different treatments. No statistical difference from the standard microscopy method was found in 75% of the samples (12 of 16). ITS-1 rRNA was detected only in samples containing viable eggs, but the levels were more variable than rDNA levels and ITS-1 rRNA could not be used for quantification. The detection limit of the rDNA-based method was approximately one larvated egg or 90 single-celled eggs; the detection limit for the rRNA-based method was several orders of magnitude higher. The rDNA qPCR method is promising for both research and regulatory applications.