Cloning and molecular characterization of a cubilin-related serine proteinase from the hard tick Haemaphysalis longicornis

Serine proteinases are one of the largest proteolytic families of enzymes, and have diverse cellular activities in mammalian tissues. We report here the cloning and molecular characterization of a cDNA encoding the serine proteinase of the hard tick Haemaphysalis longicornis (HlSP). The HlSP cDNA is 1570 bp long and the deduced precursor protein consists of 464 amino acids with a predicted molecular mass of 50.4 kDa and a pI of 8.2. The preprotein, consisting of 443 amino acids, was predicted to include a complement C1r/C1s, Uegf, and bone morphogenic protein-1 domain, a low-density lipoprotein receptor class A domain, and a catalytic domain. HlSP sequence analysis showed high similarity to serine proteinases reported from arthropods and vertebrate animal species. Two-dimensional immunoblot analysis revealed endogenous HlSP in adult tick extracts at 50 kDa. Endogenous HlSP was also expressed in all lifecycle stages of H. longicornis. Immunohistochemical studies detected the endogenous enzyme in the midgut epithelial cells of an adult tick. The Escherichia coli-expressed recombinant HlSP was demonstrated to degrade bovine serum albumin and hydrolyze the substrate Bz-L-Arg-pNA at the rate of 30.2 micromol/min/mg protein. Further, HlSP expression was up-regulated during a blood-feeding process, indicating its involvement in the digestion of host blood components.

The proteome expression patterns in adult Ascaris suum under exposure to aerobic/anaerobic environments analyzed by two-dimensional electrophoresis

We investigated the protein expression patterns (the proteome) in adult Ascaris suum under exposure to aerobic and anaerobic environments in vitro using two-dimensional polyacrylamide gel electrophoresis. Adult A. suum were cultured in RPMI-1640 in the absence of oxygen (anaerobic) or in its presence (aerobic), and whole worm extracts and their excretory-secretory (ES) products were prepared for protein analysis. More than 200 protein spots resolved in two-dimensional gels. A comparison of aerobic versus anaerobic cultures revealed two aerobic and three anaerobic specific spots differentially expressed in adult worm extracts. ES products released during aerobic/anaerobic cultures also exhibited one aerobic and seven anaerobic specific spots in two-dimensional maps. One of the anaerobic specific protein spot was analyzed for its internal amino acid sequence (1-LLAFELAPHGIR-12; 1-VNTVNPGAVD-10) and the protein was predicted to be a putative dehydrogenase. These findings suggest that the availability of oxygen or its absence in the environment may influence protein expression patterns in parasitic nematodes.

Temperature and metal ions-dependent activity of the family I inorganic pyrophosphatase from the swine roundworm Ascaris suum

Temperature dependence, heat stability and metal ions-dependent activity were examined on the Family I inorganic pyrophosphatase (PPase) recently identified from Ascaris suum. Recombinant A. suum PPase (rAsPPase) showed an optimal activity at 55 degrees C. The rAsPPase was heat stable at 40 degrees C in the absence of added Mg(2+) and at 50 degrees C in its presence. The enzyme required divalent metal ions for its activity. The preferences for the metal ions (5 mM concentration) were in the order: Mg(2+)> Co(2+)> Cu(2+)> Fe(2+)> Zn(2+)> Mn(2+). On the contrary, enzyme activity was inhibited by Ca(2+). These findings suggest that catalytic features of AsPPase are consistent with the Family I PPases reported from a wide range of organisms.

Metabolic derangements in interstitial brain edema with preserved blood flow: selective vulnerability of the hippocampal CA3 region in rat hydrocephalus

Hydrocephalus induces interstitial brain edema, which causes neurological deficits, even if the intracranial pressure is maintained within the normal range, and the cerebral blood flow (CBF) does not decline to an ischemic level. The precise mechanisms underlying such edema-induced neuronal dysfunction remain unclear. In the present study, in an attempt to elucidate the metabolic derangements in brain tissue with interstitial edema, we evaluated the changes in CBF and oxidative/glucose metabolism using a rat model of kaolin-induced hydrocephalus. Hydrocephalus was produced in male Wistar rats by intrathecal injection of 0.1 ml aluminum silicate suspension (200 mg/ml) via the cisterna magna. CBF was determined by 14[C]-iodoantipyrine autoradiography. Oxidative metabolism was evaluated by cytochrome oxidase (CYO) histochemistry, and glucose metabolism by hexokinase (HK) histochemistry. CBF declined with the development of hydrocephalus, but did not reach an ischemic level. The CYO activity was diffusely depressed in both the cortex and hippocampus. The HK activity was preserved at the early stage of hydrocephalus. At the advanced stage, the HK activity was reduced in the hippocampal CA3 region first, and diffusely thereafter. In conclusion, interstitial brain edema impairs oxidative metabolism even at the early stage of hydrocephalus, and shifts the metabolism to anaerobic glycolysis despite a preserved CBF. Impairment of glucose metabolism was first observed in the CA3 region, suggesting that the CA3 is metabolically vulnerable, and CA3 dysfunction may contribute to the memory deficits seen in hydrocephalus.

Gene Silencing of a Cubilin-Related Serine Proteinase from the Hard Tick Haemaphysalis longicornis by RNA Interference

RNA interference (RNAi) has been recently exploited to determine gene function by degrading specific mRNAs in several eukaryotic organisms. We constructed a double stranded RNA (dsRNA) from a previously cloned Haemaphysalis longicornis serine proteinase (HlSP) gene to test the importance of the function of the HlSP gene product during blood-feeding. Growth of unfed ticks treated with HlSP dsRNA was significantly inhibited compared to that of PBS-treated ticks. This inhibition was supported by the level of HlSP mRNA. HlSP may play a crucial role for blood-feeding in these ticks. This is the first report on gene silencing of a functional serine proteinase in hard ticks.

Mice intranasally immunized with a recombinant 16-kilodalton antigen from roundworm Ascaris parasites are protected against larval migration of Ascaris suum

Protective immunity to the pig roundworm, Ascaris suum, has been demonstrated by immunization of pigs with antigens derived from the parasite's larval stages. We identified a protective antigen commonly expressed in the human and pig Ascaris infections as a 16-kDa protein (As16), which has no similarity at the amino acid level to mammalian proteins but has some similarity to those of the filarial parasites and Caenorhabditis elegans gene product. Localization analysis revealed that the native As16 was highly expressed in the adult worm intestine, hypodermis, and cuticles. In addition, As16 was detected in the parasite excretory and secretory products. Mice intranasally vaccinated with Escherichia coli-expressed recombinant As16 (rAs16), coupled with cholera toxin B subunit, generated a significant increase in the level of rAs16-specific immunoglobulin G (IgG) and IgE in serum. Mucosal IgA levels were also increased. The recombinant protein evoked a mixed (both Th1 and Th2) type of immune response characterized by elevated levels of gamma interferon and interleukin-10 in the culture supernatants of activated spleen cells. An increased level of IgG1 and IgG2a in serum was also observed. The vaccinated mice showed a reduction by 58% in the recovery of challenged larvae compared to a nonvaccinated control. These results suggest the possibility of developing a mucosal vaccine for human and pig ascariasis.

Serum antibodies induced by intranasal immunization of mice with Plasmodium vivax Pvs25 co-administered with cholera toxin completely block parasite transmission to mosquitoes

Transmission-blocking vaccines (TBVs) targeting ookinete surface proteins expressed on sexual-stage malaria parasites are considered one promising strategy for malaria control. To evaluate the prospect of developing non-invasive and easy-to-administer mucosal malaria transmission-blocking vaccines, mice were immunized intranasally with a Plasmodium vivax ookinete surface protein, Pvs25 with a mucosal adjuvant cholera toxin (CT). Immunization induced significant serum IgG with high IgG1/IgG2a ratio (indicative of Th-2 type immune response). Feeding Anopheles dirus mosquitoes with mixtures of immune sera and gametocytemic blood derived from vivax-infected volunteer patients in Thailand significantly reduced both the number of midgut oocysts as well as the percentage of infected mosquitoes. The observed transmission-blocking effect was dependent on immune sera dilution. This study demonstrates for the first time that the mucosally induced mouse immune sera against a human malaria ookinete surface protein can completely block parasite transmission to vector mosquitoes, suggesting the possibility of non-invasive mucosal vaccines against mucosa-unrelated important pathogens like malaria.

Inorganic pyrophosphatase in the roundworm Ascaris and its role in the development and molting process of the larval stage parasites

Inorganic pyrophosphatase (PPase) is an important enzyme that catalyzes the hydrolysis of inorganic pyrophosphate (PPi) into ortho-phosphate (Pi). We report here the molecular cloning and characterization of a gene encoding the soluble PPase of the roundworm Ascaris suum. The predicted A. suum PPase consists of 360 amino acids with a molecular mass of 40.6 kDa and a pI of 7.1. Amino acid sequence alignment and phylogenetic analysis indicates that the gene encodes a functional Family I soluble PPase containing features identical to those of prokaryotic, plant and animal/fungal soluble PPases. The Escherichia coli-expressed recombinant enzyme has a specific activity of 937 micro mol Pi.min-1.mg-1 protein corresponding to a kcat value of 638 s-1 at 55 degrees C. Its activity was strongly dependent on Mg2+ and was inhibited by Ca2+. Native PPases were expressed in all developmental stages of A. suum. A homolog was also detected in the most closely related human and dog roundworms A. lumbricoides and Toxocara canis, respectively. The enzyme was intensely localized in the body wall, gut epithelium, ovary and uterus of adult female worms. We observed that native PPase activity together with development and molting in vitro of A. suum L3 to L4 were efficiently inhibited in a dose-dependent manner by imidodiphosphate and sodium fluoride, which are potent inhibitor of both soluble- and membrane-bound H+-PPases. The studies provide evidence that the PPases are novel enzymes in the roundworm Ascaris, and may have crucial role in the development and molting process.

Identification and molecular characterization of a chitinase from the hard tick Haemaphysalis longicornis

A cDNA encoding tick chitinase was cloned from a cDNA library of mRNA from Haemaphysalis longicornis eggs and designated as CHT1 cDNA. The CHT1 cDNA contains an open reading frame of 2790 bp that codes for 930 amino acid residues with a coding capacity of 104 kDa. The deduced amino acid sequence shows a 31% amino acid homology to Aedes aegypti chitinase and a multidomain structure containing one chitin binding peritrophin A domain and two glycosyl hydrolase family 18 chitin binding domains. The endogenous chitinase of H. longicornis was identified by a two-dimensional immunoblot analysis with mouse anti-rCHT1 serum and shown to have a molecular mass of 108 kDa with a pI of 5.0. A recombinant baculovirus AcMNPV.CHT1-expressed rCHT1 is glycosylated and able to degrade chitin. Chitin degradation was ablated by allosamidin in a dose-dependent manner. The optimal temperature and pH for activity of the purified chitinase were 45 degrees C and pH 5-7. The CHT1 cDNA has an ELR motif for chemokine-mediated angiogenesis and appears to be a chitinase of the chemokine family. Localization analysis using mouse anti-rCHT1 serum revealed that native chitinase is highly expressed in the epidermis and midgut of the tick. AcMNPV.CHT1 topically applied to H. longicornis ticks exhibited replication. This is the first report of insect baculovirus infection of ticks. The importance of AcMNPV.CHT1 as a novel bio-acaricide for tick control is discussed.

A new active vitamin D analog, ED-71, causes increase in bone mass with preferential effects on bone in osteoporotic patients

As a candidate for active vitamin D analogs that have selective effects on bone, 1alpha,25-dihydroxy-2beta-(3-hydroxypropoxy)vitamin D3 (ED-71) has been synthesized and is currently under clinical trials. In ovariectomized rat model for osteoporosis, ED-71 caused an increase bone mass at the lumbar vertebra to a greater extent than 1alpha-hydroxyvitamin D3 (alfacalcidol), while enhancing calcium absorption and decreasing serum parathyroid hormone levels to the same degree as alfacalcidol. ED-71 lowered the biochemical and histological parameters of bone resorption more potently than alfacalcidol, while maintaining bone formation markers. An early phase II clinical trial was conducted with 109 primary osteoporotic patients. The results indicate that oral daily administration of ED-71 (0.25, 0.5, 0.75, and 1.0 microgram) for 6 months increased lumbar bone mineral density in a dose-dependent manner without causing hypercalcemia and hypercalciuria. ED-71 also exhibited a dose-dependent suppression of urinary deoxypyridinoline with no significant reduction in serum osteocalcin. These results demonstrate that ED-71 has preferential effects on bone with diminished effects on intestinal calcium absorption. ED-71 offers potentially a new modality of therapy for osteoporosis with selective effects on bone.

Human beta-defensin-2 induction in Helicobacter pylori-infected gastric mucosal tissues: antimicrobial effect of overexpression

The objective of this study was to understand more of the innate immune response to Helicobacter pylori by determining the expression of human beta-defensin-2 (hBD-2) in various gastric mucosal tissues and MKN45 gastric cancer cells with or without H. pylori. Semi-quantitative TaqMan RT-PCR and immunohistochemistry were carried out. The antimicrobial effects of a transfected hBD-2 gene against H. pylori were also evaluated. The results showed that hBD-2 was expressed in inflamed gastric mucosal tissues with H. pylori infection, but not in the absence of H. pylori infection. Expression was also detected in gastric cancers in patients with H. pylori infection. Expression was induced in the MKN45 gastric cancer cell line by H. pylori in a manner dependent on the abundance of bacteria. hBD-2-transfected 3T3J2-1 cells secreted hBD-2 protein into the culture medium and this protein inhibited growth of H. pylori completely. The results suggest that hBD-2 may be involved in the pathophysiology of H. pylori-induced gastritis.

Cloning and characterisation of a highly immunoreactive 37 kDa antigen with multi-immunoglobulin domains from the swine roundworm Ascaris suum

Antigens from larval stages of Ascaris suum have been shown to induce protection against challenge infection with infective A. suum eggs. We previously identified several antigens that reacted strongly with serum from pigs inoculated with infective eggs containing L3. In this study, we isolated an antigen with a molecular mass of 37 kDa and a pI of 4.8 (As37) from A. suum infective eggs using two-dimensional electrophoresis, and obtained a full-length cDNA by reverse transcription-polymerase chain reaction using primers designed based on the internal amino acid sequence of As37. The cDNA sequence consisted of 1,540 bp coding for a protein of 321 amino acids with a complex domain organisation. Simple modular architecture research tool (SMART) analysis indicated that As37 contains three immunoglobulin domains, indicating that it is a member of immunoglobulin superfamily (IgSF). A homology search of GenBank showed that As37 has significant similarity to Caenorhabditis elegans DIM-1 protein and has low similarity to part of the multi-repeat Ig domain from nematode twitchin and mammalian skeleton muscle titin, and to members of the IgSF at the amino acid sequence level. Localisation analysis revealed that antibodies to Escherichia coli-expressed recombinant As37 (rAs37) bound to muscle cells and the hypodermis. The antibodies identified a 37 kDa native antigen in human and dog roundworms, suggesting that there are As37 homologues in ascarid nematodes. Sera from mice, rabbits and pigs immunised with A. suum infective eggs reacted with rAs37 in immunoblot analyses. The potential use of rAs37 for protection against A. suum infection is discussed.

Comparison of arbitrarily primed-polymerase chain reaction and pulse-field gel electrophoresis for characterizing methicillin-resistant Staphylococcus aureus

AIMS

The aim of this study was to analyse genotypes for clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), including hetero-vancomycin-resistant Staph. aureus (VRSA), at a Japanese university hospital.

METHODS AND RESULTS

Seventy-eight clinical isolates of MRSA were analysed by arbitrarily primed-polymerase chain reaction (AP-PCR) using ERIC2 primer and by pulse-field gel electrophoresis (PFGE) following SmaI digestion. Analyses of the nine genotypes and 28 subtypes defined by PFGE, and of the three genotypes and 22 subtypes defined by AP-PCR, both facilitated epidemiological tracing. Used in combination, AP-PCR and PFGE provided more precise classification than the use of a single genotyping method. The six hetero-VRSA isolates were classified into four genotypes defined by the combination of both methods, but these genotypes contained non-VRSA isolates.

CONCLUSIONS

The results suggest that both PFGE and AP-PCR are useful in discriminating MRSA, but not hetero-VRSA, isolates for epidemiological analysis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Combining the results of PFGE with the results of AP-PCR can provide more detail differentiation of MRSA and hetero-MRSA isolates than either method alone.

Species-specific proteins identified in Ascaris lumbricoides and Ascaris suum using two-dimensional electrophoresis

The protein profile of adult female Ascaris lumbricoides and Ascaris suum originating from humans and pigs, respectively, was studied using two-dimensional polyacrylamide gel electrophoresis. Six different major protein spots specific for A. lumbricoides were identified irrespective of their geographical origin and no major specific spot was encountered in A. suum. No major differences in the protein profiles between the extract by phosphate-buffered saline and urea were encountered for either Ascaris species. It is therefore possible to use 2D-PAGE as a tool for discriminating the closely related Ascaris species from humans and pigs.

Lung-stage protein profile and antigenic relationship between Ascaris lumbricoides and Ascaris suum

The protein profile and antigenic properties of lung-stage larvae of Ascaris lumbricoides and A. suum were studied using 2-dimensional electrophoresis and immunoblot analysis, respectively. The protein profiles of the 2 parasites were identical except for the presence of only 1 major protein spot specific for each. There was a complete cross-reactivity between the 2 parasites at the immunological level, and no specific antigen was recognized using specific antibody raised against the 2 parasites in rabbits.

Existence of phenol oxidase in the argasid tick Ornithodoros moubata

Phenol oxidase (PO, EC 1.10.3.1) activity was detected in the hemolymph of the fourth instar nymphs of the argasid tick, Ornithodoros moubata, with peak levels corresponding to the days before the majority of the nymphs had molted, suggestive of a protective role of PO during the ecdysial phase. Higher PO activity was detected in plasma relative to the hemolymph and was negligible in hemocytes. The concentration of the hemolymph and plasma assayed clearly influenced the level of PO activity, and was significantly reduced ( P<0.005) after treatment with 1-phenyl-2 thiourea, a specific PO inhibitor. This is the first report of the existence of PO in the hemolymph and plasma of a soft tick species. The regulation of PO activity and its precise role in soft tick immunity, particularly during the ecdysial phase, are interesting and need to be examined further.

Seroepidemiologic studies on Babesia caballi and Babesia equi infections in Japan

Antibodies to Babesia caballi and Babesia equi were examined on a total of 2,019 horse serum samples that had been collected in 1971-1973 by the National Institute of Animal Health by enzyme-linked immunosorbent assay (ELISA) using recombinant proteins and by Western-blot analysis. Based on the criterion for positivity by ELISA, 5.4% (109/2,019) and 2.2% (44/2,019) had antibodies against B. caballi and B. equi, respectively. The ELISA-positive sera were further examined by Western blot; 30/109 for B. caballi and 2/ 44 for B. equi were positive for native B. caballi or B. equi, but none of them was seropositive for both infections. Based on the results of this study, further investigations should be required to survey horses that have arrived in Japan relatively recently and tick vectors of equine Babesia using ELISA with some recombinant protein, a parasite detection method in an in vitro culture of equine Babesia, and PCR testing.

Comparison of macrophage scavenger receptor-A knockout mice with wild type ones in the immune response against repeated infestation with Haemaphysalis longicornis

Using macrophage scavenger receptor-A knockout (SRKO) mice, we examined the role of macrophage class A scavenger receptors (MRS-A) on the immune response and acquisition of host resistance against repeated infestation with Haemaphysalis longicornis. Except for one batch of nymphs that infested one of the SRKO (SR-/-) mice and showed no appreciable reduction in body weight, all the other groups of nymphs manifested significant decrease in body weight. Both SR-/- and wild type (SR+/+) mice showed a sustained increase in anti-tick antibody titers, but SR+/+ mice showed significantly higher titers. The IFN-gamma assayed in SR-/- mouse immune sera was substantially less compared with that in SR+/+ mice. Immune sera from SR-/- and SR+/+ mice recognized the 51 and 44 kDa, and 44 kDa proteins, respectively, of the salivary gland antigen. The difference in the level of anti-tick resistance manifested by both groups of mice may be influenced by less efficient trapping and processing of tick antigens by macrophages in mice lacking for the macrophage scavenger receptors, and consequently affected the cascade of Th1 and Th2 responses. We have thus obtained valuable data that strongly infer the role of MSR-A in enhancing host defense against repeated infestation with H. longicornis.

Pyrazinamide resistance associated with pncA gene mutation in Mycobacterium tuberculosis in Japan

Thirty Japanese clinical isolates of Mycobacterium tuberculosis were analysed by pyrazinamide susceptibility testing and pyrazinamidase assay, as well as polymerase chain reaction for single-strand conformational polymorphism and direct sequencing of the gene encoding pyrazinamidase (pncA). All sensitive isolates showed pyrazinamidase activity and a wild-type pncA gene, but three resistant isolates had pncA gene mutations and lacked pyrazinamidase activity. The latter isolates showed a minimum inhibitory concentration of at least 100 mg/l by the 7H10 agar proportion method and 400 mg/l by the 7H9 liquid medium method. Isolate 28 showed T-to-C change at position 11, leading to Leu4 --> Ser substitution; isolate 29 had an 8-bp deletion from position 382; and isolate 30 had A-to-C change at position 29, leading to Gln10 --> Pro substitution. The deletion has not been described previously. This is the first demonstration of pncA gene mutations in PZA-resistant M. tuberculosis strains isolated from Japanese patients.

Intranasal immunization with recombinant Ascaris suum 14-kilodalton antigen coupled with cholera toxin B subunit induces protective immunity to A. suum infection in mice

Animals can be rendered immune to Ascaris parasites by immunization with infectious-stage larvae. The specific parasite gene products that mediate protective responses in ascariasis are unknown. We have identified a cDNA encoding Ascaris suum 14-kDa antigen (As14) and evaluated the vaccinal effect of the Escherichia coli-expressed recombinant protein (rAs14). GenBank analysis showed that As14 has low similarity at the amino acid level to a Caenorhabditis elegans gene product and to antigens of the filarial nematodes but not to other known proteins. In addition, As14 homologues were found to be expressed in human and dog roundworms. In mice that received intranasal administration of rAs14 coupled with cholera toxin B subunit (rAs14-CTB), there was a 64% reduction of recovery of larvae compared with that in the nontreated group. The vaccinated mice showed a significant increase in the total serum immunoglobulin G (IgG) levels and the mucosal IgA responses. Elevation of the rAs14-specific IgE response was also seen. Measurement of the IgG subclasses showed a higher level of IgG1 and a lower level of IgG2a antibody response in the sera of the immunized mice, suggesting that protection was associated with a type II immune response. As14 is the first protective antigen against A. suum infection to be identified. Our immunization trial results in laboratory animals suggest the possibility of developing a mucosal vaccine for parasitic diseases caused by ascarid nematodes.