Valosin-containing protein from the hard tick Haemaphysalis longicornis: effects of dsRNA-mediated HlVCP gene silencing

We report the cloning and characterization of a cDNA encoding the valosin-containing protein (VCP) from the Haemaphysalis longicornis tick (HlVCP). The full-length HlVCP is 2782 bp and codes for 808 amino acids of a deduced protein with a predicted molecular mass of 89.9 kDa. The domain structure analysis revealed that the deduced protein has 2 Walker A domains, 2 Walker B domains, a Cdc48 domain, and a polyQ-binding domain. The mouse anti-HlVCP serum recognized a 97 kDa native protein in the salivary glands, midgut, and synganglion. RT-PCR analysis revealed that the native VCP was expressed throughout the developing stages and in tick organs. HlVCP silencing resulted in a decrease in tick body mass after blood feeding. This study not only contributes to a growing understanding of the ATPase gene family but also lays the groundwork for future studies on protein secretion and host-tick interaction. This study is the first report of the VCP gene from Chelicerata, which include spiders, scorpions, and ticks.

Characterization of asparaginyl endopeptidase, legumain induced by blood feeding in the ixodid tick Haemaphysalis longicornis

We characterize here a cDNA from the ixodid tick Haemaphysalis longicornis, which encodes an asparaginyl endopeptidase, legumain (HlLgm), that was present as a functional molecule in the midgut of this tick. Endogenous HlLgm was detected as a 38-kDa antigen in H. longicornis extracts and was seen throughout all developmental stages. Endogenous HlLgm was mainly localized in the midgut epithelium by immunohistochemistry, and was shown to be up-regulated by the host blood-feeding process. Recombinant HlLgm (rHlLgm) produced in Escherichia coli was shown to hydrolyze the synthetic substrate Z-Ala-Ala-Asn-MCA at the rate of 6.42x10(-4)mumol/min/mg protein. Its activity was inhibited by the thiol blocking reagents iodoacetamide and N-ethylmaleimide. The enzyme was shown to possess a unique feature of having an autocatalyzed cleavage at asparagines(364-365) at the C-terminus of both endogenous HlLgm and rHlLgm. rHlLgm degraded bovine hemoglobin and bovine serum albumin (BSA) showing its strict specificity for hydrolysis of the peptide on the carboxyl side of the asparagines, as demonstrated by internal amino acid sequence analysis of proteolytic product of BSA cleavage. These results suggest that HlLgm plays an important role in host blood-meal digestion and may be critical for the final process of digestion of blood components.

Babesial vector tick defensin against Babesia sp. parasites

Antimicrobial peptides are major components of host innate immunity, a well-conserved, evolutionarily ancient defensive mechanism. Infectious disease-bearing vector ticks are thought to possess specific defense molecules against the transmitted pathogens that have been acquired during their evolution. We found in the tick Haemaphysalis longicornis a novel parasiticidal peptide named longicin that may have evolved from a common ancestral peptide resembling spider and scorpion toxins. H. longicornis is the primary vector for Babesia sp. parasites in Japan. Longicin also displayed bactericidal and fungicidal properties that resemble those of defensin homologues from invertebrates and vertebrates. Longicin showed a remarkable ability to inhibit the proliferation of merozoites, an erythrocyte blood stage of equine Babesia equi, by killing the parasites. Longicin was localized at the surface of the Babesia sp. parasites, as demonstrated by confocal microscopic analysis. In an in vivo experiment, longicin induced significant reduction of parasitemia in animals infected with the zoonotic and murine B. microti. Moreover, RNA interference data demonstrated that endogenous longicin is able to directly kill the canine B. gibsoni, thus indicating that it may play a role in regulating the vectorial capacity in the vector tick H. longicornis. Theoretically, longicin may serve as a model for the development of chemotherapeutic compounds against tick-borne disease organisms.

Molecular characterization of a blood-induced serine carboxypeptidase from the ixodid tick Haemaphysalis longicornis

Ticks feed exclusively on blood to obtain their nutrients, but the gene products that mediate digestion processes in ticks remain unknown. We report the molecular characterization and possible function of a serine carboxypeptidase (HlSCP1) identified in the midgut of the hard tick Haemaphysalis longicornis. HlSCP1 consists of 473 amino acids with a peptidase S10 family domain and shows structural similarity with serine carboxypeptidases reported from other arthropods, yeasts, plants and mammals. Endogenous HlSCP1 is strongly expressed in the midgut and is supposed to localize at lysosomal vacuoles and on the surface of epithelial cells. Endogenous HlSCP1, identified as a 53 kDa protein with pI value of 7.5, was detected in the membrane/organelle fraction isolated from the midgut, and its expression was upregulated during the course of blood-feeding. Enzymatic functional assays revealed that a recombinant HlSCP1 (rHlSCP1) expressed in yeast efficiently hydrolyzed the synthetic substrates specific for cathepsin A and thiol protease over a broad range of pH and temperature values. Furthermore, rHlSCP1 was shown to cleave hemoglobin, a major component of the blood-meal. Our results suggest that HlSCP1 may play a vital role in the digestion of the host's blood-meal.

Molecular characterization of Rhipicephalus (Boophilus) microplus Bm86 homologue from Haemaphysalis longicornis ticks

One sequence in the EST database of a midgut cDNA library prepared from semi-engorged female Haemaphysalis longicornis ticks has been found to be a homologue of the Bm86 gene of Rhipicephalus (Boophilus) microplus ticks. The full-length sequence containing a 1785 bp open reading fragment (ORF) was obtained and designated as the Hl86 gene. The predicted amino acid sequence of the Hl86 gene shows a 37% identity to the Bm86 gene. Hl86 is predicted to be a GPI-anchored membrane-bound glycoprotein with a 19-amino acid signal sequence and a 22-amino acid hydrophobic region adjacent to the carboxyl terminus. The most important feature that Hl86 has in common with Bm86 is the repeated pattern of 6 cysteine residues forming epidermal growth factor (EGF)-like domains. RT-PCR analysis showed that Hl86 mRNA transcripts are expressed in all the life cycles of H. longicornis, and the expression was found in the midgut of the adult tick. The Hl86 was expressed in Escherichia coli as a gene10 fusion protein. Mouse anti-recombinant Hl86 serum recognized an 86 kDa protein band in the midgut lysate of semi-engorged ticks in Western blot analysis and showed a strong reaction on the luminal surface of midgut cells in an indirect immunofluorescent antibody test (IFAT). Silencing of the Hl86 gene by RNAi led to a significant reduction in the engorged tick body weight. This is the first report of cloning and characterization of the Bm86 homologue in different genera and species of ixodid and argasid ticks since Bm86 was first reported in 1989.

Characterization of glutamine: fructose-6-phosphate aminotransferase from the ixodid tick, Haemaphysalis longicornis, and its critical role in host blood feeding

Glutamine: fructose-6-phosphate aminotransferase (GFAT, EC2.6.1.16) is the first, and rate-limiting, enzyme in the hexosamine biosynthetic pathway, and is involved in the regulation of chitin biosynthesis and glycosylation of proteins. We report here the molecular characterization and potential functions of a novel GFAT (HlGFAT) from the ixodid tick Haemaphysalis longicornis. HlGFAT consists of 696 amino acids, possesses a class II glutamine aminotransferase domain and two sugar isomerase motifs, and has a close phylogenetic relationship to insect GFAT. HlGFAT was expressed at all stages of development and in multiple organs. The transcription levels in the cuticle and midgut were enhanced significantly by blood feeding during the first 3 days and decreased on the fifth day, while those in salivary glands maintained almost the same level during the first 3 days, and decreased to a rather low level at 5 days postinfestation. Endogenous HlGFAT was identified at all developmental stages and in multiple organs, such as epidermis, midgut epithelium, salivary gland, ovary, Malpigian's tubule and trachea. It was identified as a protein of 78.4 kDa using Western blot analysis. Following RNA interference of HlGFAT, engorgement by adult females was reduced significantly. One of the potential mechanisms for this effect may be that the inhibition of HlGFAT limits chitin biosynthesis, so disrupting cuticle growth and possibly peritrophic matrix formation during blood feeding.

An investigation into the distribution, host-preference and population density of ixodid ticks affecting domestic animals in Bangladesh

To study the distribution, host-preference and population density of ixodid ticks in Bangladesh, an attempt was made to collect adult ticks from various host animals in three distinct topographic zones, viz. flood plains, hills and steppe 'Barind'. Five species of ixodid ticks were recorded, namely, Boophilus microplus (56.3%), Haemaphysalis bispinosa (11.3%), Rhipicephalus sanguineus (14.7%), Hyalomma anatolicum anatolicum (15.0%) and Amblyomma testudinarium (2.8%). The data showed that B. microplus occurred predominantly on cattle (42.4%). The other hosts involved were buffaloes (12.5%), goats (25.5%) and pigs (8.2%). H. bispinosa mostly parasitized goats (31.5%) rather than cattle (12.0%) and buffaloes (10.8%). R. sanguineus was principally a dog tick (27.4%) but also parasitized cattle (10.8%) and goats (6.8%). H. a. anatolicum was restricted to cattle (19.2%) and A. testudinarium was found on both cattle (4.4%) and pigs (2.3%). These results indicate that ixodid ticks are not strictly host-specific except for H. a. anatolicum. The population density of these ticks was significantly (p < 0.01) influenced by the changing of seasons. B. microplus, H. bispinosa and R. sanguineus were by far the most widely distributed species; the distribution of H. a. anatolicum was restricted to the steppe 'Barind tract' and A. testudinarium was found in the hilly regions only.

Molecular and reverse genetic characterization of serine proteinase-induced hemolysis in the midgut of the ixodid tick Haemaphysalis longicornis

Enzyme-induced hemolysis has been shown to occur in the midgut of ticks; however, little is known about the molecular basis for hemolytic activity. We report here the molecular and reverse genetic characterization of a hemolytic midgut serine proteinase, HlSP, recently identified from the ixodid tick Haemaphysalis longicornis. Endogenous HlSP was found in the midgut lumen and its contents, indicating that HlSP is extracellularly secreted. Recombinant H. longicornis serine proteinase (rHlSP) expressed in Escherichia coli showed dose-dependent hemolytic activity towards rabbit erythrocytes, with a maximum hemolysis of 94.5% within 1 h in vitro. Tests of pH dependency showed that rHlSP displayed optimal activity at pH 6.0. In binding assays, rHlSP showed high affinity to band 3, which shares the major erythrocyte membrane proteins. Disruption of HlSP-specific mRNA by RNA interference resulted in inhibition of the degradation of host erythrocyte membranes by endogenous HlSP in the knock-down ticks, indicating that HlSP plays a crucial role in the hemolysis in the midgut of haematophagous ticks. Our results suggest that HlSP may be essential for initiating the proteolytic cascade for the degradation of the host blood-meal.

RNA interference of cytosolic leucine aminopeptidase reduces fecundity in the hard tick, Haemaphysalis longicornis

Ticks are effective vectors of pathogens because of their blood feeding and high fecundity. This high fecundity is related to the size of the blood meal. Therefore, knowledge of how blood proteins are degraded and converted to proteins, including yolk protein, is important for the development of ways to inhibit the utilization of blood proteins by ticks. RNA interference (RNAi) is becoming a powerful post-transcriptional gene silencing technique that provides insight into gene function. We constructed a double-stranded RNA (dsRNA) based on a previously cloned Haemaphysalis longicornis leucine aminopeptidase (HlLAP) gene to reevaluate the biological role in tick blood digestion. Gene specific transcriptional, translational, and functional disruptions were achieved by the introduction of dsRNA into the ticks. Significantly delayed onset of egg-laying and reduced egg oviposition resulted from the RNAi for the HlLAP gene. These results suggest that HlLAP actually works as a blood digestive enzyme and affects tick fecundity via unknown mechanisms. The reduction of egg oviposition may be caused by a decrease in nutrients, especially free amino acids generated by HlLAP, from the blood meal. This is the first report of an impact on tick reproduction caused by gene silencing of a blood digestion-related molecule.

Molecular characterization and oligosaccharide-binding properties of a galectin from the argasid tick Ornithodoros moubata

The argasid tick Ornithodoros moubata is a vector of various viral and borrelian diseases in animals and humans. We report here molecular characterization and oligosaccharide-binding properties of a novel galectin (OmGalec) from this tick. OmGalec consisted of 333 amino acids with a predicted molecular weight of 37.4 kDa. Its amino acid sequence did not contain a signal peptide or transmembrane domain. It possessed tandem-repeated carbohydrate recognition domains, in which the typical motifs important for carbohydrate affinity were conserved. OmGalec was expressed both transcriptionally and translationally at all stages of the tick life cycle and in multiple organs and was abundant in hemocytes, midguts, and reproductive organs, which are of importance in immunity, interaction with pathogens, and development, respectively, suggesting that OmGalec is a multifunctional molecule. The oligosaccharide affinity profile analyzed by applying an automated frontal affinity chromatography system revealed that rOmGalec showed a general feature of the galectin family, i.e. significant affinity for lactosamine-type disaccharides, Galbeta1-3(4)Glc(NAc), via recognition of 4-OH and 6-OH of galactose and 3 (4)-OH of Glc(NAc). Its preference for type I saccharides and alpha1-3GalNAc-containing oligosaccharides might provide clues for identifying its ligands and its potential multiple functions. Our results may contribute to the elucidation of galectin functions in the development and immunity of arthropods and/or vector and pathogen interaction and provide valuable information for the development of novel tick control strategies.

Effect of piperazine (diethylenediamine) on the moulting, proteome expression and pyrophosphatase activity of Ascaris suum lung-stage larvae

Piperazine (diethylenediamine) is an anthelmintic widely used against animal and bird ascariasis. In this study, we show that treatment with piperazine blocks Ascaris suum larval moulting and development processes and affects larval proteome expression profiles. A. suum lung-stage L3 (LL3) obtained from an infected rabbit's lungs were cultured in RPMI medium in the presence of increasing concentrations of piperazine sulfate (Pzes). Our results showed that Pzes potently inhibited moulting of A. suum LL3 in a dose-dependent manner and that moulting was completely blocked (100%) at 50mM concentrations. We then examined the changes in A. suum LL3 proteome expression patterns following Pzes exposure using two-dimensional (2D) electrophoresis. Pzes exposure inhibited expression of at least 16 major protein spots in unmoulted LL3 out of more than 200 visible protein spots resolved on 2D gels prepared from moulted larvae (i.e., lung-stage L4). Pzes exposure also inhibited expression of 13 immunogenic protein spots in unmoulted LL3. More importantly, Pzes exposure inhibited activity of a moulting-specific enzyme, inorganic pyrophosphatase of A. suum (AsPPase), by 26%. Expression of native AsPPase was also reduced following Pzes exposure as detected by immunoblotting and immunofluorescent staining. Transmission electron microscopy showed that Pzes interfered with growth and ecdysis of the cuticle and caused damage to gut tissues of the larvae. Our results suggest that A. suum LL3 may become a suitable model to screening new-class anthelmintics with antimoulting functions and that A. suum LL3-Pzes may serve as a useful tool for identification of moulting-specific potential proteins in Ascaris roundworms.

Human β-defensin-3 induction in H pylori-infected gastric mucosal tissues

AIM: To examine human β-defensin-3 (hBD-3) expression in inflamed gastric mucosal tissues or MKN45 gastric cancer cells with or without H pylori infection for better understanding the innate immune response to H pylori.

METHODS: We used reverse transcription-polymerase chain reactions and immunohistochemistry to examine hBD-3 expression in inflamed gastric mucosal tissues or MKN45 gastric cancer cells with or without H pylori. Effects of hBD-3 against H pylori were also evaluated.

RESULTS: The mean mRNA expression of hBD-3 in H pylori-positive specimens was significantly higher than that in H pylori-negative specimens (P = 0.0002, Mann-Whitney). In addition, unlike uninfected samples, 8 of 15 (53.33%) infected mucosal samples expressed hBD-3 protein. H pylori dose-dependently induced mRNA expression of hBD-3 in MKN45 cells, an effect inhibited by adding anti-toll-like receptor (TLR)-4 antibody. HBD-3 protein completely inhibited H pylori growth.

CONCLUSION: Our results suggest that like hBD-2, hBD-3 may be involved in the pathophysiology of H pylori-induced gastritis.

Identification and characterisation of a leucine aminopeptidase from the hard tick Haemaphysalis longicornis

Aminopeptidases responsible for blood digestion have yet to be identified in haematophagous ticks. We report here the cloning and molecular characterisation of a cDNA encoding leucine aminopeptidase, a member of the M17 cytosolic aminopeptidase family, from the hard tick Haemaphysalis longicornis (HlLAP). Endogenous HlLAP was detected in the soluble fraction of adult tick extracts by immunoblotting. Immunohistochemical studies demonstrated that endogenous HlLAP expression mainly took place in the cytosol of midgut epithelial cells. Furthermore, expression of HlLAP was induced by a blood-feeding process. A functional recombinant HlLAP expressed in Escherichia coli efficiently hydrolyses synthetic substrates for aminopeptidase, a leucyl (with the Km value 0.19 +/- 0.011 mM and Vmax value 157.2 +/- 3.17 nmol/min/mgprotein) and a methionyl substrate (with the Km value 0.12+/-0.0052 mM and Vmax value 171.9 +/- 2.31 nmol/min/mgprotein). Enzyme activity was found to be optimum at pH 8 and 35 degrees C. The recombinant HlLAP enzyme activity was strongly dependent on metal divalent cations, Mn2+, and was inhibited by bestatin. These results indicate that HlLAP play an important role for host's blood digestion process.

Fluoride exposure inhibits protein expression and enzyme activity in the lung-stage larvae ofAscaris suum

Sodium fluoride (NaF) is an anion that has been previously shown to block the moulting process ofAscaris suumlarvae. This study describes moulting and development-specific protein expression profiles ofA. suumlung-stage L3 (AsLL3) following NaF exposure. AsLL3s cultured in the presence or absence of NaF were prepared for protein analysis using two-dimensional (2D) electrophoresis. NaF exposure inhibited at least 22 proteins in AsLL3 compared with moulted larvae (i.e. AsLL4). A further comparison of AsLL4 with those of pre-cultured AsLL3 and NaF-exposed AsLL3 revealed 8 stage-specifically and 4 over-expressed proteins. Immunoblot analysis revealed an inhibition by NaF of 19 immunoreactive proteins. Enzyme assay and immunochemical data showed an inhibition of the moulting-specific inorganic pyrophosphatase activity by 41% and a decreased expression in NaF-treated larvae, indicating its significance in the moulting process. A protein spot associated with NaF inhibition was isolated and identified by peptide mass spectrometry and bioinformatics approaches to be a member of 3–hydroxyacyl–CoA dehydrogenase/short-chain dehydrogenase enzyme families. These results have implications for the identification of proteins specific to the moulting process as potential chemotherapeutic targets.

Clinical utility of FDG-PET for evaluation of the viability in post-chemotherapeutic residual lesions in pediatric solid tumors

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Background: Exact evaluation of viability in post-chemotherapeutic residual lesions in patients with solid tumors should allow us to select the appropriate therapeutic options. F-18 fluorodeoxyglucose position emission tomography (FDG-PET) is one of the promising modality to evaluate it without invasive procedure. Methods: The cohort is a total of 14 patients with pediatric solid tumors (rhabdomyosarcoma 7, Ewing sarcoma 4, Wilms tumor 2 and neuroblastoma 1), which are either newly diagnosed or newly relapsed between January 2005 and December 2005. A total of 15 residual tumors from the 14 patients after chemotherapy underwent 51 FDG-PET scans. Seven residual tumors out of 6 patients, who were newly diagnosed, and another 8 tumors out of 8 patients, who were relapsed, were evaluated after induction or reinduction chemotherapy. Parameters of FDG-PET were assessed by area of FDG uptake and standardized uptake values (SUV). Results of FDG-PET were compared either with histological examination of the residual tumors (n=11) or with the clinical status 6-month after the last FDG-PET (n=4) in order to judge whether the findings of FDG-PET were true or false. Results: Three of 15 residual lesions showed increased SUV, while 12 lesions obtained negative SUV. Three lesions with positive SUV consisted of 2 true-positive and 1 false-positive lesions. Among twelve lesions were negative SUV, 11 lesions were true-negative, and 1 was false-negative. The sensitivity and specificity of FDG-PET in predicting the viability of residual lesions were 66% and 91%, respectively. A lesion of rhabdomyosarcoma which obtained negative SUV in FDG-PET histological showed viable cells. A lesion of another rhabdomyosarcoma which showed positive SUV was evaluated as inflammatory lesion. Conclusions: Although FDG-PET showed excellent sensitivity and fair specificity in predicting the viability of residual lesions in patients with pediatric solid tumors, possibility of false-negativity should give us a caution not to rely on FDG-PET to judge the termination of therapy.

No significant financial relationships to disclose.

Balloon or Stent-assisted Coil Embolization for Acutely Ruptured Wide-necked Aneurysms

SUMMARY

In this paper, we report five cases with acutely ruptured wide-necked aneurysms, which were treated with coil embolization using a balloon or stent-assisted technique. Balloon-assisted coil embolization using Equinox balloon, Commodore balloon, and Hyperform balloon were performed for four patients and stent-assisted coil embolization using BX velocity for one patient. We discuss problems of coil embolization for acutely ruptured wide-necked aneurysms with a balloon or stent-assisted technique.

Vaccination with recombinant Ascaris suum 24-kilodalton antigen induces a Th1/Th2-mixed type immune response and confers high levels of protection against challenged Ascaris suum lung-stage infection in BALB/c mice

Previous studies have shown that antigens from various life-cycle stages of Ascaris suum can induce host-protective immunity against challenge infections with infective eggs of A. suum. This study evaluated whether Escherichia coli-expressed recombinant 24-kDa antigen from A. suum (rAs24) was a suitable vaccine candidate for the control of Ascaris infections by examining its performance in a mouse model. Immunization of BALB/c mice in three consecutive doses with rAs24 in Freund's Complete Adjuvant (FCA) results in protection against challenge infections as manifested by a 58% reduction (P<0.001) in recovery and stunted development of A. suum lung-stage larvae at day 7 post-challenge. Sera obtained from immune protected mice had a significantly increased level of immunoglobulin G (IgG) (P<0.0001) but had no IgE response. Analysis of IgG-subclass profiles revealed that IgG1 (P<0.0001) showed the greatest increase followed by IgG2b (P<0.005), IgG2a (P<0.006) and IgG3 (P<0.04). Splenic T cells from rAs24-FCA immunized mice secreted significantly high levels of both Th1 cytokine gamma-interferon (P<0.005) and Th2 cytokine interleukin-10 (P<0.001) after stimulation with rAs24 in vitro. Interestingly, affinity purified anti-rAs24 IgG was shown to inhibit moulting of A. suum lung-stage L3 to L4 in vitro by 26%, indicating an in vivo function of the endogenous As24 in the moulting processes. An intense expression of endogenous As24 in the hypodermis and gut epithelium of A. suum lung-stage L3 by immunofluorescence supports a function for endogenous As24. These findings may contribute to the understanding of rAs24-induced Th1/Th2-mediated effector mechanisms required for the protection of A. suum lung-stage larval infection.

Nasal immunization with a malaria transmission-blocking vaccine candidate, Pfs25, induces complete protective immunity in mice against field isolates of Plasmodium falciparum

Malaria transmission-blocking vaccines based on antigens expressed in sexual stages of the parasites are considered one promising strategy for malaria control. To investigate the feasibility of developing noninvasive mucosal transmission-blocking vaccines against Plasmodium falciparum, intranasal immunization experiments with Pichia pastoris-expressed recombinant Pfs25 proteins were conducted. Mice intranasally immunized with the Pfs25 proteins in the presence of a potent mucosal adjuvant cholera toxin induced robust systemic as well as mucosal antibodies. All mouse immunoglobulin G (IgG) subclasses except IgG3 were found in serum at comparable levels, suggesting that the immunization induced mixed Th1 and Th2 responses. Consistent with the expression patterns of the Pfs25 proteins in the parasites, the induced immune sera specifically recognized ookinetes but not gametocytes. In addition, the immune sera recognized Pfs25 proteins with the native conformation but not the denatured forms, indicating that mucosal immunization induced biologically active antibodies capable of recognizing conformational epitopes of native Pfs25 proteins. Feeding Anopheles dirus mosquitoes with a mixture of the mouse immune sera and gametocytemic blood derived from patients infected with P. falciparum resulted in complete interference with oocyst development in mosquito midguts. The observed transmission-blocking activities were strongly correlated with specific serum antibody titers. Our results demonstrated for the first time that a P. falciparum transmission-blocking vaccine candidate is effective against field-isolated parasites and may justify the investigation of noninvasive mucosal vaccination regimens for control of malaria, a prototypical mucosa-unrelated mosquito-borne parasitic disease.

Pyrophosphatase of the roundworm Ascaris suum plays an essential role in the worm's molting and development

Previous studies indicated that inorganic pyrophosphatase of Ascaris suum (AsPPase) plays an important role in larval survival in the host. Here we describe a precise role for AsPPase in larval molting and development and also describe the potential role of recombinant AsPPase (rAsPPase) in protective immunity to A. suum infection. Using reverse transcriptase PCR analysis, we found that disruption of AsPPase gene function by RNA interference resulted in suppression of AsPPase mRNA levels. RNA interference also caused inhibition of molting of third-stage larvae (31%) and suppression of native protein expression, as demonstrated by a 56% reduction in enzyme activity and quantified by immunoblot and immunofluorescence analyses, suggesting that AsPPase has a role in the molting process. The anatomic location of the AsPPase native enzyme in the hypodermis of larvae along with its elevated expression prior to and during the molting process supports such a role. Anti-rAsPPase immunoglobulin G (IgG) also resulted in 57% inhibition of molting of A. suum lung-stage third-stage larvae to fourth-stage larvae in vitro with developmental arrest. Antigenic epitopes of AsPPase overlapped the enzyme active sites. Mice immunized with rAsPPase exhibited high antigen-specific IgG antibody responses and were protected (>70%) against a challenge A. suum migratory-phase infection. Splenic T cells from rAsPPase-immunized mice produced low levels of T helper 1-type cytokines (gamma interferon and interleukin-2) in vitro but exhibited an elevated interleukin-10 response. A significantly high level of IgG1 subclass antibodies was found in immunized mice. Our results establish that AsPPase has a critical role in the molting and development of Ascaris roundworms and suggest the potential of AsPPase for use as a candidate vaccine against ascariasis.

Enzymatic characterization of a cubilin-related serine proteinase from the hard tick Haemaphysalis longicornis

In the present study, we performed enzymatic characterization of Haemaphysalis longicornis serine proteinase (HlSP) with a view to shed light on the mechanisms of blood digestion in the hard ticks. Escherichia coli-expressed recombinant HlSP (rHlSP) was shown to potently hydrolyze the synthetic substrates Bz-(DL)-Arg-pNA, Z-Ala-Ala-Leu-pNA and Suc-Ala-Ala-Ala-pNA and yielded an activity of 31.5, 88.2 and 18.3 mumol/min/mg protein, respectively at an optimum temperature of 25 degrees C. However, the enzyme showed little activity to hydrolyze the substrates Suc-Arg-Pro-Phe-His-Leu-Leu-Val-Tyr-MCA and Pyr-Phe-Leu-pNA. The optimum pH for the enzyme was shown to be 4.0 to 5.0. Several inhibitors such as antipain, leupeptin and phenylmethylsulfonyl fluoride (PMSF), specific for serine proteinase were shown to inhibit enzyme activity by 20-82%, while E-64 (specific for cysteine proteinases) and pepstatinA (specific for aspartic proteinases) had shown only little inhibitory effects on it. This is the first report on enzymatic characterization of a functional serine proteinase from the hard ticks.

Molecular cloning and partial characterization of a nematode-specific 24 kDa protein fromAscaris suum

The cloning and molecular characterization of a cDNA encodingAscaris suum24 kDa antigen (As24) are described. The cDNA sequence consists of 853 bp with an open reading frame coding for a protein of 147 amino acids with an inferred signal peptide of 19 amino acids. The predicted molecular mass and pI were 16 kDa and 8·35 respectively. The endogenous protein in adultA. suumwas 24 kDa with the expected pI. A search of the public databases revealed over 50% homology with proteins from filarial parasites but not to other known proteins, suggesting that As24 is a nematode-specific protein. Immunohistochemical studies using polyclonal antibodies raised againstEscherichia coli-expressed recombinant As24 demonstrated that the endogenous As24 proteins were intensely localized in unembryonated eggs within the uterus, uterine and gut epithelium, muscle tissues and in the hypodermis of an adult femaleA. suum. Endogenous As24 was expressed throughoutA. suumdevelopment and was detected in the excretory/secretory products by immunoblot analysis. Importantly, a homologous protein(s) was detected inAscarisfrom human andToxocara canisfrom dog, suggesting that As24 is a nematode-specific protein.

Recombinant Ascaris 16-Kilodalton protein-induced protection against Ascaris suum larval migration after intranasal vaccination in pigs

We recently cloned a protective antigen that is commonly expressed in Ascaris species that infect humans and pigs. We evaluated the vaccinal effects of this 16-kilodalton protein (As16) in pigs, the natural host of Ascaris suum, by intranasal immunization. Pigs that received Escherichia coli-expressed recombinant As16 (rAs16) coupled with cholera toxin (CT) had significantly elevated levels of rAs16-specific serum immunoglobulin G (IgG) and mucosal-associated IgA antibodies. rAs16 evoked a type II immune response characterized by elevated levels of interleukin-4 and -10 in the culture supernatants of peripheral blood mononuclear cells of the vaccinated pigs. An increased level of rAs16-specific serum IgG1 was also detected. Pigs vaccinated with rAs16-CT were protected from migration of A. suum larvae through the lungs, as indicated by a 58% reduction in the recovery of lung-stage third-stage larvae (L3), compared with that in nonvaccinated controls. Purified immunoglobulin from rAs16-CT-vaccinated pigs inhibited survival of infective L3 and interrupted the molting of lung-stage L3. Immunofluorescence studies revealed that this immunoglobulin bound to the digestive tracts of L3, suggesting that it might inactivate functions of the gut tissues of Ascaris species. We conclude that rAs16 is a promising mucosal vaccine candidate for pig and human ascariasis.