Quantitative label-free proteomic analysis of excretory-secretory proteins in different developmental stages of Trichinella spiralis

Trichinella spiralis (T. spiralis) is a zoonotic parasitic nematode with a unique life cycle, as all developmental stages are contained within a single host. Excretory-secretory (ES) proteins are the main targets of the interactions between T. spiralis and the host at different stages of development and are essential for parasite survival. However, the ES protein profiles of T. spiralis at different developmental stages have not been characterized. The proteomes of ES proteins from different developmental stages, namely, muscle larvae (ML), intestinal infective larvae (IIL), preadult (PA) 6 h, PA 30 h, adult (Ad) 3 days post-infection (dpi) and Ad 6 dpi, were characterized via label-free mass spectrometry analysis in combination with bioinformatics. A total of 1217 proteins were identified from 9341 unique peptides in all developmental stages, 590 of which were quantified and differentially expressed. GO classification and KEGG pathway analysis revealed that these proteins were important for the growth of the larvae and involved in energy metabolism. Moreover, the heat shock cognate 71 kDa protein was the centre of protein interactions at different developmental stages. The results of this study provide comprehensive proteomic data on ES proteins and reveal that these ES proteins were differentially expressed at different developmental stages. Differential proteins are associated with parasite survival and the host immune response and may be potential early diagnostic antigen or antiparasitic vaccine candidates.

The retention and concentration of glycogen in Trichinella nativа in the winter-spring period

The metabolism of Trichinella spp. is primarily anoxybiotic in nature. Their main energy source is glycogen, which is stored in the stichocites at the muscular stage of the larval development. When subject to tow temperatures the Trichinella larvae consume glycogen and neutral fats to provide for basal metabolism until the energy supplies reach the critical level. The present study establishes the glycogen concentration as well the invasive activity of T. nativа when affected by low temperatures in natural conditions. The carcasses of infected laboratory rats were placed in containers beneath the snow cover, in the natural conditions of a game husbandry in Central Russia. The viability, invasive capacity and the glycogen level were monitored in the Trichinella larvae monthly. The invasive capacity of Trichinella larvae was established based on the presence of the larvae in the muscular tissue of laboratory mice after the peroral administration of the helminth larvae. On the 45 day of the experiment, the mice were euthanized by cervical dislocation, and if the Trichinella larvae could be discovered in the muscular tissue with the help of the trichinelloscopic compression method, the invasive capacity of the Trichinella larvae was viewed as positive. To establish the quantitative value of glycogen content in Trichinella larvae a modified method was used. In order to measure the glycogen level in the T. nativa larvae isolated by fermentation larvae were counted in one drop of the suspended sedimentation in the Migacheva-Kotelnikov chamber. To establish the quantitative value of glycogen content in Trichinella larvae a method based on the treatment of glycogen with iodine, optical density measurement with a refractometer MКMФ-02 was used. For the purpose of measuring the concentration of glycogen in Trichinella larvae in the suspended sedimentation a calibration curve was used. The studies showed that the viability indicator of the Trichinella larvae which had been preserved in natural conditions in the four months of the winter-spring period, in the muscular tissue of laboratory rats remained high (over 90 %). The glycogen concentration in one helminth larva was 0.041 μg in January, 0.033 μg in February, 0.015 μg in April. The invasive capability of the preserved Trichinella larvae was considerably reduced to 33.3 %. In the winter period, under temperatures below 0 °C, a decrease in the glycogen concentration in the Trichinella larvae was observed.

TSL-1 antigens of Trichinella: An overview of their potential role in parasite invasion, survival and serodiagnosis of trichinellosis

The majority of studies on the immunobiology of Trichinella species have centred on the larval muscular phase (L1) with a view to identifying immunodominant antigens located on the surface of the cuticle and in the larval secretions; the nucleus of the parasite-host interaction. These antigens have been classified as eight groups (TSL-1-TSL-8), of which those belonging to the group TSL-1 have been most intensely studied. The principal constituents are glycoproteins, glycan carriers that contain a unusual sugar, the tyvelose (3,6-dideoxy-d-arabinohexose). Studies aimed at improving serodiagnostic techniques to detect trichinellosis indicate that these antigens are ideal candidates. They are capable of inducing a strong humoral response involving the generation of specific antibodies against beta-tyvelose, a sugar that seems to be exclusive to the Trichuroidea. Furthermore, these glycoproteins appear to fulfil an important function in the development and maintenance of the parasite in the muscular niche, and they appear to be fundamental for the invasion of the intestinal epithelium. It has also been demonstrated that specific monoclonal antibodies against tyvelose can mediate a degree of immunoprotection in the rat through the phenomenon known as rapid expulsion.

Comparative analysis of the excretory-secretory proteome of the muscle larva of Trichinella pseudospiralis and Trichinella spiralis

The nematodes Trichinella spiralis and Trichinella pseudospiralis are both intracellular parasites of skeletal muscle cells and induce profound alterations in the host cell resulting in a re-alignment of muscle-specific gene expression. While T. spiralis induces the production of a collagen capsule surrounding the host-parasite complex, T. pseudospiralis exists in a non-encapsulated form and is also characterised by suppression of the host inflammatory response in the muscle. These observed differences between the two species are thought to be due to variation in the proteins excreted or secreted (ES proteins) by the muscle larva. In this study, we use a global proteomics approach to compare the ES protein profiles from both species and to identify individual T. pseudospiralis proteins that complement earlier studies with T. spiralis. Following two-dimensional gel electrophoresis, tandem mass spectrometry was used to identify the peptide spots. In many cases identification was aided by the determination of partial peptide sequence from selected mass ions. The T. pseudospiralis spots identified included the major secreted glycoproteins and the secreted 5'-nucleotidase. Furthermore, two major groups of T. spiralis-specific proteins and several T. pseudospiralis-specific proteins were identified. Our results demonstrate the value of proteomics as a tool for the identification of ES proteins that are differentially expressed between Trichinella species and as an aid to identifying key parasite proteins that are involved in the host-parasite interaction. The value of this approach will be further enhanced by data arising out the current T. spiralis genome sequencing project.

Molecular cloning and characterization of an Rcd1-like protein in excretory-secretory products of Trichinella pseudospiralis

A cDNA library was constructed from muscle larvae of Trichinella pseudospiralis. A cDNA clone, designated as Tp8 contained a cDNA transcript of 1326 bp length with a single open reading frame, which encoded 303 amino acid residues (34,187 Da, estimated molecular mass). The predicted amino acid sequence of the clone had an identity of approximately 60% to the Rcd1 (Required cell differentiation 1) -like proteins among a wide range of organisms. Real-time quantitative polymerase chain reaction results showed that the transcription level of Tp8 gene reached the highest value in adult worms, and that the transcription level in muscle larvae before stichosome formation was higher than in muscle larvae after stichosome formation. The recombinant Tp8 protein migrated at 37 kDa and reacted to antibody against T. pseudospiralis excretory-secretory (E-S) products and sera from mice infected with T. pseudospiralis. An antibody against the Tp8 recombinant protein could stain proteins migrating at approximately 34 kDa (which is the expected size from the sequence) on Western blotting of E-S products from muscle larvae. An immunocytochemical study showed that the Tp8 protein was present within the stichocyte of muscle larvae and adults worms.

Effects of raw biles and their non-protein fractions from fox, pig, sheep and chicken on the survival of Trichinella spp. in vitro

The in vitro differential effect of fox, pig, sheep and chicken bile and corresponding non-protein fractions at various concentrations on the motility of released muscle larvae of Trichinella spiralis, Trichinella nativa and Trichinella nelsoni was examined. In many cases, the percentages of motile (live) larvae of the three Trichinella species cultured in the presence of the non-protein fractions of bile from the study animals were significantly higher (p<0.001) compared to their respective control cultures. In addition, the percentages of motile (live) larvae of all Trichinella species cultured in the presence of the non-protein fraction of bile at every concentration from all study animals were significantly higher (p<0.001) compared to their respective cultures in the presence of raw bile. Not only did results with non-protein fractions of bile differ from those with raw bile, but also the non-protein fraction, with increased dilution, showed a decrease in the percentages of motile larvae while the opposite was true with the raw bile (p<0.001). These observations indicate that the non-protein fraction of bile prolongs the in vitro survival of larvae.

Expression of Hsp90, Hsp70 and Hsp60 in Trichinella species exposed to oxidative shock

Stress response and phosphorylation of heat shock proteins (HSPs) 60, 70 and 90 were studied in Trichinella nativa, T. nelsoni, T. pseudospiralis and T. spiralis larvae at 30-min intervals following exposure to 20, 100 and 200 mM H2O2. There was a time- and dose-dependent differential survival for the infective stage larvae (L1) of these four Trichinella species. Immunoblotting analysis revealed that constitutive Hsp60 and Hsp70, but not Hsp90, from test Trichinella species are constitutively phosphorylated on serine/threonine residues as they converted to forms with increased sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) mobility by treatment with alkaline phosphatase. After exposure to H2O2, while there was a time-related occurrence of the three HSPs with decreased SDS-PAGE mobility, these HSPs were insensitive to alkaline phosphatase except in the case of exposure to 20 mM H2O2 for Hsp60 from all Trichinella species and Hsp70 from T. spiralis and T. nelsoni. The synthesis of HSPs forms with decreased SDS-PAGE mobility is a susceptibility signal because the lower concentration of peroxide (20 mM) did not cause a decrease on HSPs SDS-PAGE mobility in T. spiralis and T. nelsoni, the two more resistant selected Trichinella species.

Expression of excretory and secretory protein genes of Trichinella at muscle stage differs before and after cyst formation

By adapting a semi-quantitative reverse transcriptase-PCR (RT-PCR) method, we investigated kinetics of gene expression at different developmental stages of Trichinella spiralis and T. pseudospiralis. The analyzed genes included four kinds of excretory and secretory (ES) proteins, a heat shock protein (HSP) and a DNA binding protein and showed that T. spiralis and T. pseudospiralis expressed ES proteins in a stage-specific manner. The gene encoding a 43 kDa ES protein was expressed by muscle larvae, either pre-cyst or post-cyst larvae. The genes encoding: the 53 kDa ES protein of T. spiralis; 53 kDa ES protein of T. pseudospiralis; and 19.6 kDa ES protein of T. spiralis were expressed by post-cyst larvae and adult worms, but not expressed by pre-cyst larvae or newborn larvae. The results showed that pre-cyst larvae and post-cyst larvae are similar but different in the expression of 53 and 19.6 kDa ES proteins. On the other hand, genes of housekeeping proteins, such as HSP and the DNA binding protein, were expressed at all stages although there were some differences in the expression level.

Molecular cloning and characterization of a novel protein of Trichinella pseudospiralis excretory-secretory products

A novel excretory-secretory (ES) protein of Trichinella pseudospiralis was produced. A cDNA library was constructed from mRNA of muscle larvae at 30 days post infection (p.i.) and immunoscreened with the antibody against ES products. A clone, designated Tp22-3, contained a cDNA transcript of 815 bp in length with a single open reading frame which encoded 244-amino acids (28407 Da in the estimated molecular mass). A database search revealed that no sequences had a homology to this predicted protein. The recombinant protein was produced in an Escherichia coli expression system. Stage specific expression of this protein was suggested from the following experiments. An antibody against the recombinant protein could stain proteins migrating at about 28 kDa (which is the expected size from the sequence) on Western blotting of crude extracts or ES products from 30 days p.i. muscle larvae, but failed to stain any proteins in crude extracts from newborn larvae or 15 days p.i. muscle larvae. The antibody reacted to the stichocytes of larvae at 30 days p.i., but did not react to 15 days p.i. muscle larvae. The production of an mRNA transcript for Tp22-3 gene was restricted largely to the 30 days p.i. muscle larvae and adult worms.

Molecular cloning and characterization of a 21 kDa protein secreted from Trichinella pseudospiralis

Recombinant protein was produced from the cDNA library of Trichinella pseudospiralis, which seemed to form part of the excretory-secretory (ES) products. The library was constructed from cDNA of muscle larvae at 1 month post-infection, and immunoscreened with antibody against T. pseudospiralis ES products. A clone, designated Tp21-3, contained a cDNA transcript of 657 bp in length with a single open reading frame, which encoded 172 amino acids (19617 Da in the estimated molecular mass). The predicted amino acid sequence of clone Tp21-3 had a similarity of 76% to that of clone ORF 17.20 (GenBank under accession number U88239) from T. spiralis. The recombinant fusion proteins encoded by clone Tp21-3 were produced in an Escherichia coli expression system and affinity purified. On Western blotting analysis, Tp21-3 recombinant proteins migrated at 40 kDa and reacted to antibody against T. pseudospiralis ES products and T. pseudospiralis-infected sera. Sera were developed against Tp 21-3 recombinant proteins, which reacted to a single band migrating at 21 kDa in crude worm extract and ES products from T. pseudospiralis on Western blotting analysis, and reacted with stichocytes of T. pseudospiralis on immunohistochemical staining.

DNA-binding activity in the excretory-secretory products of Trichinella pseudospiralis (Nematoda: Trichinelloidea)

A novel DNA-binding peptide of Mr approximately 30 kDa was documented for the first time in the excretory-secretory (E-S) products of the infective-stage larvae of Trichinella pseudospiralis. Larvae recovered from muscles of infected mice were maintained for 48 h in DMEM medium. E-S products of worms extracted from the medium were analysed for DNA-binding activity by the electrophoretic mobility shift assay (EMSA). Multiple DNA-protein complexes were detected. A comparison of the Mr of proteins in the complexes indicated that they could bind to the target DNA as a dimer, tetramer or multiples of tetramers. Site selection and competition analysis showed that the binding has a low specificity. A (G/C-rich)-gap-(G/T-rich)-DNA sequence pattern was extracted from a pool of degenerate PCR fragments binding to the E-S products. Results of immunoprecipitation and electrophoretic mobility supershift assay confirmed the authenticity of the DNA-binding protein as an E-S product.

Secretion of the novel Trichinella protein TSJ5 by T. spiralis and T. pseudospiralis muscle larvae

The Trichinella tsJ5 gene is preferentially expressed in muscle larvae of Trichinella spiralis and encodes a novel protein. Previous observations have shown tsJ5 to be expressed at higher levels in encapsulating species than in non-encapsulating species and down-regulation of gene expression in T. pseudospiralis to be correlated with a lower protein abundance in the muscle larva of this species. In the present study we have determined the full-length cDNA sequence of the tsJ5 homologue in T. pseudospiralis (tpJ5). Antigens recognised by an anti-J5 antibody are found on the cuticular surface of both T. spiralis and T. pseudospiralis muscle larvae, as well as in the body wall muscle. We show that both the TSJ5 and TPJ5 proteins are found in the excretory/secretory fractions collected from muscle larva cultured in vitro and that despite the absence of a typical N-terminal signal sequence, secretion of pTSJ5 is mediated through the classical ER/Golgi secretory pathway.

Cloning and characterization of Rab and Ran/TC4 cDNA clones in Trichinella spp

The cloning and characterization of seven Rab and three Ran/TC4 partial cDNA sequences in both cystic (Trichinella spiralis and T. britovi) and noncystic species (T. pseudospiralis) are reported. These molecules were cloned by rapid amplification of cDNA ends via polymerase chain reaction (RACE-PCR), using cDNA from the aforementioned Trichinella spp. coupled to the AP1 adaptor. As primers, AP1 and 5B (derived from the WDTAGQE sequence of region 2 specific for Rab and Ran proteins) sequences were included in the PCR. The cloned cDNAs were sequenced and characterized by both Southern-blot and Northern-blot analysis. Trichinella spp. Rab- and Ran-like molecules showed divergences in both the nucleotide and the deduced amino acid sequences as compared with the corresponding homologues previously described in other organisms. In addition, differences were observed among the Trichinella species, mainly between the cystic and the noncystic species, in both DNA restriction-enzyme polymorphism and expression of the six GTPases isolated.

Heat shock response of Trichinella spiralis and T. pseudospiralis

Heat shock proteins (HSPs) were documented for the first time in both somatic extracts and excretory/secretory (ES) products of the infective-stage larvae of Trichinella spiralis and T. pseudospiralis. Larvae recovered from muscles of infected mice were heat shocked at 37, 40, 43 and 45 degrees C in RPMI 1640 medium containing L(-)[35S]methionine. Somatic extracts and ES products of heat-shocked worms were then analysed by SDS-PAGE, autoradiography and laser densitometry. Prominent bands of HSPs were observed at 43 degrees C which is the optimal heat shock temperature. The major HSPs in somatic extracts of T. spiralis were 20, 47, 50, 70, 80 and 86 kDa. When the temperature was increased from 37 to 43 degrees C, the greatest increase in absorbance was observed in HSPs 70 and 86. In vitro translation of mRNA in a nuclease-treated rabbit reticulocyte lysate system showed an increase in the synthesis of the 80 kDa protein. This suggests that the production of HSP 80 is regulated at the transcriptional level. The major HSPs in the ES products were 11, 45, 53 and 64 kDa. In T. pseudospiralis, the major HSPs in the somatic extracts were 20, 26, 31, 50, 53, 70, 80 and 86 kDa, and in the ES products, 11, 35, 37, 41 and 64 kDa.

Studies on the rate of selective uptake of amino acids by Trichinella larvae in vivo

Groups of C57BL/6J mice, orally infected with 300 larvae each of Trichinella spiralis or T. pseudospiralis were injected with [3H]-alanine, tyrosine, tryptophan or glycine. The incorporation of isotope labelled amino acids into larval proteins was measured at 2, 6, and 12 months post-infection. It was shown that there is a significant increase in the in vivo uptake of isotope labelled amino acids with time by the larvae of T. spiralis and T. pseudospiralis. The level of uptake was highest for tyrosine followed by tryptophan, alanine and then glycine, for both species. The in vivo uptake of amino acids by T. pseudospiralis larvae was always higher than T. spiralis or the host at 6 and 12 months post-infection. At 2 months post-infection, T. spiralis uptake of these amino acids was higher, except for tyrosine. This may be related to the special needs of these larvae during the process of encystation. The higher metabolic requirements of T. pseudospiralis may be related to the higher energy needs of these non encapsulated, highly motile and mobile muscle larvae.

Analysis of a 43-kDa glycoprotein from the intracellular parasitic nematode Trichinella spiralis

The L1 larvae of the parasitic nematode Trichinella spiralis invade skeletal muscle and initiate a process that has been interpreted to represent skeletal muscle dedifferentiation. In this process, the infected region of the muscle cell is converted into a unique structure, called the Nurse cell. The nematode T. spiralis can survive for tens of years within the cytoplasm of the Nurse cell and secretes proteins into the cytoplasm that are believed to play a role in mediating the Nurse cell formation or maintenance. We have cloned a cDNA encoding the T. spiralis-derived, 43-kDa secreted protein. Structural analysis of the predicted 344-amino acid sequence revealed an N terminally located signal peptide and a potential helix-loop-helix motif in the main body of the protein. Antibodies raised against the 43-kDa recombinant protein were used in immunocytolocalizations of T. spiralis-infected skeletal muscle sections. These antibodies strongly stained the Nurse cell nuclei and the nematode itself. Specific, though slightly weaker staining also occurred in the Nurse cell cytoplasm. In Western blots, the antibodies react with the 43-kDa protein but also detected at least two other T. spiralis-secreted proteins. DNA hybridizations reveal at least one additional 43-kDa-related sequence encoded in the T. spiralis genome. We conclude that either the 43-kDa protein and/or a closely related 43-kDa family member is secreted into the muscle and translocates to the muscle-derived nuclei. This model may provide insights into the mechanisms involved in Nurse cell formation.

Trichinella spiralis: modifications of the cuticle of the newborn larva during passage through the lung

A scintigraphic method was developed to study the distribution of radioactivity after iv injection of 131I-labeled Trichinella spiralis newborn larvae into normal rats. It was found that the radioactivity was immediately retained in the lungs and thereafter slowly released, with a mean transit time in excess of 9 hr, as calculated by image analysis. At various times after iv injection of newborn larvae into normal mice, the lungs were removed and parasites were recovered and counted. Fifty to seventy percent of the larvae injected were recovered after 30 sec, between 10 and 30% after 1 min, and less than 4% at 15 min. These results indicate that during the very rapid passage of newborn larvae through the lungs, labeled components of the cuticle are detached and retained. It is suggested that the modifications produced in the cuticle of the newborn larva during its passage through the lung may increase its resistance to the nonspecific defense mechanisms of the host.

Biochemical effects of luxabendazole on Trichinella spiralis

Biochemical changes produced by luxabendazole in muscle-stage Trichinella spiralis larvae consisted of a decrease in free glucose and glycogen levels (46.71% and 35.66%, respectively) after in vivo treatment, slight in vitro inhibition of fumarate reductase activity (24.15%) and, finally, inhibition of [3H]-colchicine-tubulin binding, which was found to be of a competitive nature, with an inhibition constant (Ki) of 0.9 x 10(-7) M. In a parallel study, luxabendazole did not appear to be inhibitory to [3H]-colchicine binding to pig-brain tubulin.

The mode of action of some benzimidazole drugs on Trichinella spiralis

In an attempt to find possible targets for benzimidazole action in muscle-stage larvae of Trichinella spiralis, the effects of mebendazole and thiabendazole were tested in vivo by oral treatment of infested mice and in vitro by including these anthelmintics in an adequate maintenance medium containing decapsulated larvae. The effects of the anthelmintics on succinate dehydrogenase and fumarate reductase activities, measured in the mitochondrial fraction obtained from the in vivo- or in vitro-treated larvae showed that only thiabendazole causes significant inhibition of fumarate reductase activity. On the other hand, measurements of free glucose, glycogen reserves and soluble protein in the treated larvae indicate that in vivo, mebendazole and thiabendazole clearly diminish free glucose levels, although in vitro only mebendazole produces the same diminution. Both the glycogen and protein contents of the larvae remained unchanged after treatment in vivo or in vitro. The importance of these findings with regard to a possible site of action for mebendazole and thiabendazole is discussed.

Trichinella spiralis: behavior, structure, and biochemistry of larvae following exposure to components of the host enteric environment

Four layers are present on the surface of infective larvae of Trichinella spiralis isolated from host muscle in pepsin-HCl. Trypsin treatment of pepsin-HCl isolated worms caused partial degradation and removal of large patches of the two outer surface layers. Following exposure to bile, only traces of the outer layers remained on the worms surface. These changes in the worm surface were accompanied by a shift from Type I behavior, typical of pepsin-HCl isolated larvae, to Type II behavior, (snakelike) following exposure to either trypsin or bile. Worm behavior was also temperature dependent. Type I behavior was typical of worms maintained at room temperature regardless of treatment, while Type II behavior displayed by worms held at 37 C was treatment dependent. The absorption of in vitro glucose or beta-methyl-D-glucoside was lowest in pepsin-HCl isolated first stage infective larvae, significantly higher in trypsin treated worms and greatest in worms following exposure to bile. Sugar uptake by worms isolated from the host small intestine after 1 hr of enteral infection was similar to that seen in worms isolated from host muscle in pepsin-HCl. Sugar uptake in vitro in worms 2 hr following enteral infection was similar to worms following exposure to bile. The highest levels of sugar absorption in vitro occurred in worms which had resided in the small intestine for 3 hr. The lowest rates of incorporation of label into worm tissues was seen in 1 hr enteral and pepsin-HCl isolated worms. Infective larvae treated with trypsin or bile incorporated significantly greater amounts of label than the two former groups. The highest levels of incorporation of label into worm tissues was seen in 3 hr enteral worms. These findings support the view that trypsin, bile, and temperature serve as environmental cues which lead to alteration of the parasite's behavioral and nutritional status.

Glucose absorption in vitro by the enteric stages of Trichinella spiralis

Absorption of glucose in vitro by enteric stages of Trichinella spiralis was examined in worms isolated at different times following infection. Glucose absorption by 6-h-old worms was similar to that seen during moulting (24 h post-infection (p.i.]. As embryogenesis began (48 h p.i.) glucose absorption in vitro by the parasite rose dramatically to a peak in 72-h-old worms. Absorption of glucose in vitro remained high in 96-h-old worms but as larviposition began (120 h p.i.) glucose uptake by T. spiralis dropped significantly. Glucose absorption by worms isolated from the host during the primary immune response was unaffected. Glucose absorption in vitro remained at similar levels in worms isolated between 120 and 312 h p.i. The percentage of absorbed label incorporated into parasite tissues was greatest in 48- and 312-h-old worms. Glucose uptake in vitro by pre-adult and adult worms changed with time and these changes accompanied specific events in the biology of the parasite.

Glycosidases of Trichinella spiralis

The exoglycosidases beta-N-acetyl-D-glucosaminidase, beta-N-acetyl-D-galactosaminidase, alpha-1-fucosidase, alpha-D-glucosidase and alpha-D-mannosidase, and a non-specific acid phosphohydrolase are present at high levels in extracts of adult and muscle-stage (L1) Trichinella spiralis and at lower (5-30-fold) levels in extracts of the newborn larvae. The enzyme activities from the L1 extract were characterized. All displayed maximum activity at acid pH. beta-N-acetyl-D-glucosaminidase and beta-N-acetyl-D-galactosaminidase had identical molecular weights (110 000), pH optima (5.0), and isoelectric points (5.7) indicating that both of these substrate specificities reside in the same protein molecule. alpha-1-Fucosidase had a molecular weight of 125 000 and exhibited two pH optima (5.0 and 6.0) and four isoelectric points (5.9, 6.4, 6.7 and 7.1) indicating its presence in multiple molecular forms. alpha-D-Glucosidase had a molecular weight of 85 000, a pH optimum of 6.0 and an isoelectric point of 5.2; alpha-D-mannosidase had a molecular weight of 192 000, a pH optimum of 6.0 and an isoelectric point of 4.5; and acid phosphatase had a molecular weight of 81 000, a pH optimum of 6.0 and two isoelectric points (4.8 and 5.9) indicating its existence in two molecular forms. The same glycosidases and acid phosphatase were detected also in culture fluids collected after 15-20-h incubation of both L1 and adults. As in the worm extracts, beta-N-acetyl-D-glucosaminidase was present in these culture fluids at the highest activity with acid phosphatase present at the next highest activity.

Metabolic integration during the host associations of multicellular animal endoparasites

The nature of metabolic interaction during parasitic infection was discussed and the concept of metabolic integration outlined. The subjective nature of the integrative argument was noted. The parasite-host relationships of larval trematodes of the genus Schistosoma with their intermediate molluscan hosts, the nematode Trichnella spiralis and cestode Hymenolepis diminuta, with their definitive hosts, as well as the hymenopterous insect parasite, Hyposoter exiguae, with its insect host, Trichoplusia ni, were examined. The significance of the immune system in the establishment of the parasite-host association and the means by which parasites evade host defense were discussed. The involvement of microorganisms or "hyperparasites" during the host associations of multicellular parasites was described. The importance of evolutionary considerations in assessing the nature of metabolic interaction and its significance to the success of the parasite-host relationship was emphasized. The use of teleological assessment and anthropomorphic description was discussed.

Taurine levels in Trichinella spiralis infected versus noninfected rat diaphragms

1. Trichinella spiralis muscle larvae caused a significant (P less than 0.05) reduction in the concentration of muscle taurine on day 10 and a highly significant (P less than 0.001) reduction on day 15 postinfection in rat diaphragms. 2. No significant (P greater than 0.05) taurine alteration was observed on days 5, 8, 30 and 60 post-infection. 3. Although taurine was found to be a constitutent of the amino acid pool of T. spiralis excysted larvae, its concentration was sufficiently low so as not to be a factor in adding to the taurine level of the host. 4. Carbon-14 labelled taurine was determined to be transported into T. spiralis excysted larvae. 5. The taurine pool in these larvae is probably derived from the host.

Changing proteins on the surface of a parasitic nematode

Most of the organisms of the phylum Nematoda are free living, but some are animal or plant parasites of major importance to man. During their life cycle all nematodes undergo a series of moults in which they shed an external cuticle, consisting of an outermost membrane-like layer of unknown composition and a series of fibrillar layers similar to collagens. Because of this structure, the cuticle has been viewed as an acellular exoskeleton with rather inert molecular components. However, observations have shown that it contains enzymes and sometimes haemoglobin, and that nutrients are absorbed through it in the infective larvae and adut stages of Brugia pahangi. It is bound by complement and antibody, resulting in the adherence of leukocytes, and antibody-dependent cell-mediated reactions damage the cuticle of newborn larvae of Trichinella spiralis and the microfilariae of Dipetalonema viteae and Litomosoides carinii. We report here that the surface of the cuticle of the parasitic nematode Trichinella spiralis expresses protein molecules which change qualitatively following the moulting process, and quantitatively during growth of the worms within one stage. Also, surface proteins are released in vitro at a rate which depends on the conditions of culture of the worms.

Survival of Trichinella spiralis larvae in sewage sludge anaerobic digesters

The survival of some bacteria, viruses, protozoans, and helminths through the sewage digestion process has been a question of considerable concern among researchers throughout the world. Among the most resistant organisms are some of the pathogenic roundworms and tapeworms. Encysted larvae of Trichinella spiralis are sometimes present in animal tissues discarded as waste from slaughterhouses, restaurants or other sources. In experimental anaerobic sewage digesters, encysted larvae of T. spiralis, in rat muscle, were able to survive a maximum of 96 hr in a "batch" digester. In a digester "fed" daily with small numbers of encysted larvae, "draw-off" remained infective for white rats throughout a 16-day experimental period. Potentially infective material could be present when there is continuous "draw-off" from the anaerobic digesters.

Lethality of disrupted intestinal lamina propia cells for Trichinella spiralis in vitro

The possible direct role of inflammatory cells in resistance to Trichinella spiralis was studied by observing the effects of lamina propria cells from the small intestine (LP cells) of immunized rats on various stages of the parasite. Effects produced by physically disrupted cells were compared to those produced by intact cells on worms exposed to phytohemagglutinin or immune serum. LP cells were isolated from the rat intestine by collagenase digestion of everted gut segments that were previously denuded of epithelium by treatment with hyaluronidase. Disrupted cells, but not intact ones, selectively killed T. spiralis juvenile and adult worms in vitro, whereas larvae were unaffected by similar treatment. Attempts to identify the lethal component of disrupted cells led to an evaluation of the enzyme, peroxidase. Mucosal peroxidase is localized in LP cells and its activity increases several-fold during intestinal trichinosis. It is presumed to be myeloperoxidase, a particulate-bound enzyme of myeloid-derived leukocytes that functions as part of a potent antimicrobial system in combination with H2O2 and a halide. Results indicated that the vermicidal component of LP cells was associated with the pellet fraction of disrupted centrifuged LP cells, but was not linked to a peroxidase-H2O2-halide system.