Taenia solium tapeworms synthesize corticosteroids and sex steroids in vitro

Cysticercosis is a disease caused by the larval stage of Taenia solium cestodes that belongs to the family Taeniidae that affects a number of hosts including humans. Taeniids tapeworms are hermaphroditic organisms that have reproductive units called proglottids that gradually mature to develop testis and ovaries. Cysticerci, the larval stage of these parasites synthesize steroids. To our knowledge there is no information about the capacity of T. solium tapeworms to metabolize progesterone or other precursors to steroid hormones. Therefore, the aim of this paper was to investigate if T. solium tapeworms were able to transform steroid precursors to corticosteroids and sex steroids. T. solium tapeworms were recovered from the intestine of golden hamsters that had been orally infected with cysticerci. The worms were cultured in the presence of tritiated progesterone or androstenedione. At the end of the experiments the culture media were analyzed by thin layer chromatography. The experiments described here showed that small amounts of testosterone were synthesized from (3)H-progesterone by complete or segmented tapeworms whereas the incubation of segmented tapeworms with (3)H-androstenedione, instead of (3)H-progesterone, improved their capacity to synthesize testosterone. In addition, the incubation of the parasites with (3)H-progesterone yielded corticosteroids, mainly deoxicorticosterone (DOC) and 11-deoxicortisol. In summary, the results described here, demonstrate that T. solium tapeworms synthesize corticosteroid and sex steroid like metabolites. The capacity of T. solium tapeworms to synthesize steroid hormones may contribute to the physiological functions of the parasite and also to their interaction with the host.

Steroid synthesis by Taenia crassiceps WFU cysticerci is regulated by enzyme inhibitors

Cysticerci and tapeworms from Taenia crassiceps WFU, ORF and Taenia solium synthesize sex-steroid hormones in vitro. Corticosteroids increase the 17β-estradiol synthesis by T. crassiceps cysticerci. T. crassiceps WFU cysticerci synthesize corticosteroids, mainly 11-deoxycorticosterone (DOC). The aim of this work was to investigate whether classical steroidogenic inhibitors modify the capacity of T. crassiceps WFU cysticerci to synthesize corticosteroids and sex steroid hormones. For this purpose, T. crassiceps WFU cysticerci were obtained from the abdominal cavity of mice, pre-cultured for 24h in DMEM+antibiotics/antimycotics and cultured in the presence of tritiated progesterone ((3)H-P4), androstendione ((3)H-A4), or dehydroepiandrosterone ((3)H-DHEA) plus different doses of the corresponding inhibitors, for different periods. Blanks with the culture media adding the tritiated precursors were simultaneously incubated. At the end of the incubation period, parasites were separated and media extracted with ether. The resulting steroids were separated by thin layer chromatography (TLC). Data were expressed as percent transformation of the tritiated precursors. Results showed that after 2h of exposure of the cysticerci to 100 μM formestane, the (3)H-17β-estradiol synthesis from tritiated androstenedione was significantly inhibited. The incubation of cysticerci in the presence of (3)H-DHEA and danazol (100 nM) resulted in (3)H-androstenediol accumulation and a significant reduction of the 17β-estradiol synthesis. The cysticerci (3)H-DOC synthesis was significantly inhibited when the parasites were cultured in the presence of different ketoconazole dosis. The drug treatments did not affect parasite's viability. The results of this study showed that corticosteroid and sex steroid synthesis in T. crassiceps WFU cysticerci can be modified by steroidogenic enzyme inhibitors. As was shown previously by our laboratory and others, parasite survival and development depends on sex steroids, therefore the inhibition of their synthesis is a good starting point exploited in situations where the inhibition of steroidogenesis could help to control the infection for the development of new treatments, or replacement of the usual therapy in resistant parasite infections. We raise the possibility that these drug actions may be beneficially.

Identification of immunodominant peptides from Gnathostoma binucleatum

Gnathostomiasis is now recognized as a zoonosis with a worldwide distribution. In the Americas, it is caused by the third-stage larvae of Gnathostoma binucleatum and in Asia mainly by G. spinigerum. The availability and preparation of specific antigens are among the main obstacles for developing reliable immunodiagnostic tests. In this study, six immunodominant peptides were identified and characterized from G. binucleatum, somatic antigens (AgS: 24, 32, and 40 kDa) and excretory-secretory antigens (AgES: 42, 44, and 56 kDa) by two-dimensional immunoblot analysis. Among those immunodominant peptides, two AgS spots were characterized by mass spectrometric analysis (32 kDa; pI 6.3 and 6.5) and identified as type 1 galectins. In accordance with this finding, a fraction of AgS exhibited affinity to lactose and displayed a 100% specificity and sensitivity for the diagnosis of human gnathostomiasis.

Taenia crassiceps WFU cysticerci synthesize corticosteroids in vitro: metyrapone regulates the production

Taenia solium and Taenia crassiceps WFU cysticerci and tapeworms have the ability to synthesize sex steroid hormones and have a functional 3β-hydroxisteroid dehydrogenase. Corticosteroids (CS) like corticosterone and dexamethasone have been shown to stimulate in vitro estrogen production by Taenia crassiceps WFU cysticerci. The aim of this work was to study the ability of T. crassiceps WFU cysticerci to synthesize corticosteroids, and the effect of the inhibitor metyrapone on the CS synthesis. For this purpose T. crassiceps WFU cysticerci were obtained from the abdominal cavity of mice, thoroughly washed and pre-incubated in multiwells for 24 h in DMEM plus antibiotics/antimycotics. The tritiated CS precursor progesterone ((3)H-P4) was added to the culture media and parasites cultured for different periods. Blanks containing the culture media plus the (3)H-P4 were simultaneously incubated. Blanks and parasite culture media were ether extracted and analyzed by thin layer chromatography (TLC) in two different solvent systems. Corticosterone production was measured in the culture media by RIA. In some experiments metyrapone (0.1-0.5 mM) was added for 24, 48 or 72 h. Results showed that cysticerci mainly synthesized tritiated 11-deoxy corticosterone (DOC) and small amounts of corticosterone that was also detected by RIA. Small amounts of (3)H-11-deoxy cortisol were also found. Corticosteroid synthesis was time dependent. The addition of metyrapone significantly inhibited tritiated DOC, deoxycortisol and corticosterone synthesis. These results show for the first time that parasites have the capacity to synthesize CS that is modulated by metyrapone. Data suggest that DOC is the main corticosteroid in the parasites.

Visualization and 3D reconstruction of flame cells of Taenia solium (cestoda)

Background

Flame cells are the terminal cells of protonephridial systems, which are part of the excretory systems of invertebrates. Although the knowledge of their biological role is incomplete, there is a consensus that these cells perform excretion/secretion activities. It has been suggested that the flame cells participate in the maintenance of the osmotic environment that the cestodes require to live inside their hosts. In live Platyhelminthes, by light microscopy, the cells appear beating their flames rapidly and, at the ultrastructural, the cells have a large body enclosing a tuft of cilia. Few studies have been performed to define the localization of the cytoskeletal proteins of these cells, and it is unclear how these proteins are involved in cell function.

Methodology/Principal Findings

Parasites of two different developmental stages of T. solium were used: cysticerci recovered from naturally infected pigs and intestinal adults obtained from immunosuppressed and experimentally infected golden hamsters. Hamsters were fed viable cysticerci to recover adult parasites after one month of infection. In the present studies focusing on flame cells of cysticerci tissues was performed. Using several methods such as video, confocal and electron microscopy, in addition to computational analysis for reconstruction and modeling, we have provided a 3D visual rendition of the cytoskeletal architecture of Taenia solium flame cells.

Conclusions/Significance

We consider that visual representations of cells open a new way for understanding the role of these cells in the excretory systems of Platyhelminths. After reconstruction, the observation of high resolution 3D images allowed for virtual observation of the interior composition of cells. A combination of microscopic images, computational reconstructions and 3D modeling of cells appears to be useful for inferring the cellular dynamics of the flame cell cytoskeleton.

Intrahepatic growth and maturation of Gnathostoma turgidum in the natural definitive opossum host, Didelphis virginiana

Gnathostoma turgidum is a gastric nematode parasite of opossums found in the Americas. We recently found that G. turgidum juveniles appear in the liver of the opossums where they become mature adults and almost synchronously move to the stomach during certain months of the year, suggesting the importance of the liver for the growth and maturation of this species in the final hosts. In this study we attempted to detect G. turgidum larvae in the liver of opossums, Didelphis virginiana that are the natural final hosts. The results show that tiny (<3mm in length) third stage larvae (L3) appeared in the liver of opossums around November and December. Also in the liver, we found large L3 of up to about 10mm in length together with juveniles and mature adults from February to March. In spite of their length, large L3 have 4 rows of hooklets, and their gonads remained undeveloped. Morphological features of the small and large L3 of G. turgidum are described including scanning electron microscope images. The seasonal switching of the several growth stages of G. turgidum from small L3 to adult worms in the liver and eventual migration to the stomach in opossums suggests the unique feature of G. turgidum utilizing the liver as the maturation site.

Discovery of an endemic area of Gnathostoma turgidum infection among opossums, Didelphis virginiana, in Mexico

Gnathostomosis, caused by Gnathostoma binucleatum, is a serious public health issue in Mexico. Although 2 other Gnathostoma spp., G. turgidum and G. lamothei, have been found in wild animals, their natural life cycle or their relation to human disease remains unclear. While we were conducting an epidemiological survey on Gnathostoma spp. in Sinaloa State, Mexico, we found an endemic area for G. turgidum in common opossums, Didelphis virginiana, located in Tecualilla, Sinaloa. The species identification was carried out by morphological and molecular biological methods. This is the first record of an endemic area for G. turgidum infection in opossums, D. virginiana, in the Americas.

Antimicrobial peptides (Temporin A and Iseganan IB-367): effect on the cysticerci of Taenia crassiceps

Taenia solium infections continue being a health problem in undeveloped countries, and few effective control measures against this parasite are being applied. Antimicrobial peptides (AMPs) belong to the innate immune response and capable of destroying pathogens. We tested the ability of two AMPs, Temporin A (TA) and Iseganan IB-367 (IB-367) to damage T. crassiceps cysticerci in vitro. Doses of 200 and 400 microg/ml of TA and IB-367 caused cysticerci to shrink, lose motility, the formation of macrovesicles in the tegument, as well as decreased evagination properties. These changes were observed as early as 3-6h and became more pronounced over 24h, when the morphological changes of the bladders became evident by both light and electron microscopy. Electron micrographs of cysticerci exposed to peptides showed initial changes as collapsed microvesicles in the tegument, with formation of large vesicles and extrusion of tegumentary tissues into the surrounding media, which led to complete loss of the tegument as well as shrinkage and complete loss of structure of parenchymal tissue after 24h. Peptides administered to cysticercotic mice one month post-infection in a single intraperitoneal dose of 200 or 400 microg, reduced the parasite load by 25% for IB-367, and 50% for TA. The humoral response of infected mice does not appear capable of killing surviving cysticerci. Our studies show that in vitro, AMPs severely damage the tegument and the scolex, and open a new pathway for biological drug design or the development of transgenic animals that over express these peptides capable of killing the cysticerci in vivo.

Morphology and biochemistry of the pork tapeworm, Taenia solium

This chapter describes the life cycle, general morphology and ultrastructure of the larval and adult stages of Taenia solium, a parasitic flatworm of humans found in underdeveloped countries. Experimental results describing the role of proteins and glycoproteins in the host-parasite relationship, as well as the various strategies the larval stage has developed to evade the host immune responses are analyzed. Characteristics of the tapeworm attachment site in the hamster intestine and the host inflammatory reaction are reviewed. The general morphology and ultrastructure of the experimental tapeworm is described, with emphasis on muscle fiber distribution, the abundance of cytoplasmic glycogen and its association with gap junctions, the development of testis, structure of mature spermatids and vas efferens. Recent descriptions of T. solium actin, myosin and calreticulin components, metabolic steroid pathways, apoptosis and glucose uptake of tapeworms in the hamster model are reviewed.

Taenia crassiceps: chloride currents expressed in Xenopus oocytes upon injection of mRNA of cysticerci (WFU strain) isolated from mice

To study the properties of ion channels of the tapeworm Taenia crassiceps, mRNA was isolated from cysticerci and injected into mature oocytes of the frog Xenopus laevis and ion currents were recorded four days after injection with the two-electrode voltage clamp technique. Oocytes injected with mRNA of T. crassiceps expressed outward currents (I(TC)) that activated instantly after onset of the test pulse, followed by a slow inactivation at potentials over +40 mV, with a reversal potential of -23.2+/-5 mV. They were not affected by changes on monovalent cationic composition of external media, but replacement of external chloride by gluconate shifted significantly the reversal potential, suggesting that I(TC) are anion currents, with a permeability sequence of NO3->Cl(-)>I(-)>>Gluconate. These currents were sensitive to changes of external pH but not to hypotonic challenges. They were significantly inhibited by DIDS, NPPB and Niflumic acid, but not by 9-anthracene. These results suggest that I(TC) are the result of expression of anion channels from the tapeworm T. crassiceps.

The key steroidogenic enzyme 3beta-hydroxysteroid dehydrogenase in Taenia solium and Taenia crassiceps (WFU)

Larval and adult stages of Taenia solium and Taenia crassiceps WFU strain were analyzed by histochemical and biochemical methods to determine the existence of steroid pathways. The presence of the key enzyme 3beta-hydroxisteroid-dehydrogenase (3beta-HSD) was examined in frozen sections of cysticerci obtained from mice and segments of tapeworms obtained from the intestine of hamsters. 3beta-HSD activity was detected by nitroblue-tetrazolium products after incubation with dehydroepiandrosterone, androstendiol, or pregnenolone. Tapeworm tissues exhibited 3beta-HSD activity in the subtegumentary areas of the neck and immature proglottids following incubation with androstendiol, as well as surrounding the testes in mature proglottids. T. solium cysticerci exhibited 3beta-HSD activity in the subtegumentary tissues. The synthesis of steroid hormones involving the activity of 3beta-HSD was studied in cysticerci or tapeworms incubated in the presence of tritiated steroid precursors. The culture media were analyzed by thin layer chromatography and showed synthesis of androstendiol, testosterone, and 17beta-estradiol by cysticerci, androstendiol, and 17beta-estradiol by tapeworms. The results strongly suggest the activity of 3beta-HSD in taeniid parasites that have at least a part of the enzymatic chain required for androgen and estrogen synthesis and that the enzymes are present in the larval stage and from the early strobilar stages to the mature proglottids.

Ultrastructure of a spermatid transport system in the mature proglottids of experimental Taenia crassiceps (WFU strain)

In classical textbooks of parasitology, the mature proglottids of taeniids are depicted as structures in which the individual testis are connected to the vas deferens through the vas efferens system, usually depicted as a network of channels. From our morphological analyses of proglottids in the cestode Taenia crassiceps, we have been unable to identify this channel network. It is unclear how the spermatids are transported from the testes to the vas deferens, as is unresolved the location of the cells responsible for the production of testosterone (Leydig cells) or the possible equivalent of Sertoli cells, necessary for the differentiation process of these cells. In this experimental work, we have examined the ultrastructure of tissues in the vicinity of the vas deferens in mature proglottids obtained from the intestines of hamsters infected with cysticerci from the peritoneum of infected mice. Worm tissues were fixed, processed, and sectioned for transmission electron microscopy. Significant areas of the testis epithelia emitted cytoplasmic projections surrounded by extracellular matrix, where they appear as septated pockets enclosing free axonemes and spermatids. Vas efferens walls are made up of nucleated cells with cytoplasm annealing to each other through cell membrane junctions. Lodged between the junctions are membrane-bound pouches with dense granules found as aggregates or aligned in a semicircular array. The efferens wall exhibits numerous spermatids emerging into the lumen, an observation that suggests the epithelial wall may have the maturing functions of Sertoli cells of vertebrates. Large cells adjacent to the vas efferens contained prominent rough endoplasmic reticulum and large mitochondria, characteristics described for Leydig cells of vertebrates. Our observations suggest that taeniid spermatids are either transported from the testes to the vas system by epithelial pockets or that the epithelial pockets may be cross-sections of a highly coiled vas efferens system.

Taeniid tapeworm responses to in vitro glucose

Experimental taeniid strobilae from Taenia solium and T. crassiceps (WFU strain) were incubated for 0-72 h in 0, 5 or 20 mM glucose solutions and further exposed for 15 min to the gap junction fluorochrome Lucifer Yellow. Frozen sections were obtained from each worm and observed under an epifluorescent microscope. Worm sections from strobilae incubated with glucose, revealed intense fluorescence in the base of the tegumentary surface, suggesting that this tissue behaves as a gap junction complex. Fluorescence intensity differences between control worms not exposed to glucose and worms incubated with glucose, were highly significant. The results demonstrate that under in vitro conditions, glucose is taken up along the whole strobilar tegument in both taeniid species, suggesting, that although taeniids attached to the duodenum probably take up most of their nutrients directly from the mucosal wall, the capacity for absorbing glucose along the tegumentary surface is always active and may increase the survival capacity of these intestinal worms by promoting glucose absorption at other points in the intestinal lumen.

Apoptosis patterns in experimental Taenia solium and Taenia crassiceps strobilae from golden hamsters

Apoptosis or programmed cell death (PCD) patterns of two taeniid species, Taenia solium and Taenia crassiceps, were explored in adult tapeworms grown in golden hamsters. Animals were fed either ten viable T. solium cysticerci from naturally infected pigs or from T. crassiceps WFU strain maintained in Balb/c mice. Adult strobilae were recovered from the intestine at different times after infection and either frozen at -70 degrees C or fixed in paraformaldehyde-glutaraldehyde. Frozen sections were processed using the DNA fragmentation fluorescent TUNEL reagents and examined in an epifluorescent microscope. Fixed tissues were processed for light and electron microscopy. Typical apoptotic cells were found in the central core of scolex and strobilar tissues, mainly in the germinal tissue and subtegumentary areas. By the TUNEL technique, cells exhibited the characteristic fluorescent images of condensed nuclear chromatin. By light microscopy of thick sections stained with toluidine blue, we found a number of small rounded cells which had lost their cytoplasmic bridges and had shrunken nuclei with aggregated chromatin, cells which were found interspersed with normal syncytial cells. Similar cell morphology was confirmed by electron microscopy. Stunted viable worms, recovered with longer mature specimens, had very short strobilae and exhibited a large number of apoptotic cells in the germinal neck tissues. The results are consistent with the syncytial nature of these parasites, and strongly suggest that cell proliferation and PCD in these adult cestodes are continuous processes of the germinal tissue and tegumentary cytons.

Antigenic Proteins Associated with Calcareous Corpuscules of Taenia solium: Partial Characterization of a Calcium-Binding Protein

BACKGROUND

A protein fraction was isolated from calcareous corpuscles of Taenia solium cysticerci. The antigens in this fraction were recognized in ELISA and Western blot assays by all sera from a group of patients with active neurocysticercosis (NC) and were not recognized by the sera from patients with other neurological disorders. Western blot analysis also showed that several high molecular weight proteins were strongly recognized by antibodies in all the neurocysticercotic patient sera, suggesting a potential for serological diagnosis of neurocysticercosis.

METHODS

In order to characterize these antigenic proteins, we used a monoclonal antibody raised against a high MW calcium-binding protein associated with calcareous corpuscles of Echinococcus granulosus (EgCaBP1).

RESULTS

Western blot assays revealed the recognition of a protein band of about 260 kDa, appearing within the range of the high MW antigens recognized by the NC sera. Several cDNA clones were isolated through screening of a T. solium metacestode library with a DNA probe for EgCaBP1, containing partial coding sequences showing about 88% identity with the protein of E. granulosus. Moreover, a recombinant product expressed in bacteria from the partial coding sequence of T. solium showed the ability to bind Ca2+ and was recognized by the monoclonal antibody. This recombinant calcium-binding protein of T. solium was not recognized by the NC patient sera by ELISA and Western blot.

CONCLUSIONS

Antigenic proteins in the calcareous corpuscles of T. solium metacestodes deserve further analysis as candidates in the development of diagnostic tools for neurocysticercosis.

Cloning and expression of a Na+, K+-ATPase α-subunit from Taenia solium (TNaK1α)

The Na(+), K(+)-ATPase are membrane-associated enzymes that transport Na(+) and K(+) across the membrane generating chemical and electrical gradients, essential to maintain the resting potential for the excitation of myocytons and neurons and for transport of nutrients. The cDNA encoding a full-length isoform of Taenia solium Na(+), K(+)-ATPase alpha-subunit (TNaK1alpha) was isolated from a cysticercal cDNA library. TNaK1alpha has 1014 amino acids and a predicted molecular mass of 111,989Da. The protein displays strong sequence homology and conserved motifs typical of Na(+), K(+)-ATPase alpha-subunits. Northern and Southern hybridizations reveal a TNaK1alpha mRNA of about 3.7kb, which is encoded by a single gene. Polyclonal antibodies raised against a synthetic peptide corresponding to the NH(2)-terminal sequence of TNaK1alpha recognized a 100-kDa polypeptide in the membrane fraction of adult and larval stages of T. solium and other Taenia species. Immunolocalization studies using the same antibodies revealed that the TNaK1 is preferentially localized in muscle cells and protonephridial ducts, and in small quantities in the tegument of T. solium cysticerci.

Excitability changes in human forearm corticospinal projections and spinal reflex pathways during rhythmic voluntary movement of the opposite limb

Rhythmic movements brought about by the contraction of muscles on one side of the body give rise to phase-locked changes in the excitability of the homologous motor pathways of the opposite limb. Such crossed facilitation should favour patterns of bimanual coordination in which homologous muscles are engaged simultaneously, and disrupt those in which the muscles are activated in an alternating fashion. In order to examine these issues, we obtained responses to transcranial magnetic stimulation (TMS), to stimulation of the cervicomedullary junction (cervicomedullary-evoked potentials, CMEPs), to peripheral nerve stimulation (H-reflexes and f-waves), and elicited stretch reflexes in the relaxed right flexor carpi radialis (FCR) muscle during rhythmic (2 Hz) flexion and extension movements of the opposite (left) wrist. The potentials evoked by TMS in right FCR were potentiated during the phases of movement in which the left FCR was most strongly engaged. In contrast, CMEPs were unaffected by the movements of the opposite limb. These results suggest that there was systematic variation of the excitability of the motor cortex ipsilateral to the moving limb. H-reflexes and stretch reflexes recorded in right FCR were modulated in phase with the activation of left FCR. As the f-waves did not vary in corresponding fashion, it appears that the phasic modulation of the H-reflex was mediated by presynaptic inhibition of Ia afferents. The observation that both H-reflexes and f-waves were depressed markedly during movements of the opposite indicates that there may also have been postsynaptic inhibition or disfacilitation of the largest motor units. Our findings indicate that the patterned modulation of excitability in motor pathways that occurs during rhythmic movements of the opposite limb is mediated primarily by interhemispheric interactions between cortical motor areas.

Ultrastructure of spermiogenesis and the spermatozoon in Taenia crassiceps strobilae WFU strain (Cestoda, Cyclophyllidea, Taeniidae) from golden hamsters

Strobilae from Taenia crassiceps (WFU strain) were obtained from outbred hamsters (Mesocricetus auratus) by feeding them viable metacestodes maintained by intraperitoneal passage in female Balb/c mice. Mature and gravid proglottids from strobilae were recovered from hamster intestines and fixed for light and electron microscopy. By light microscopy, the expected structure of taeniid proglottids was observed. Ultrastructural analysis of ten proglottids showed that testicular follicles and vas deferens contained filiform spermatids, with a single axoneme, and an elongated helicoidal nucleus inserted between the axoneme and the spiraled cortical microtubules. At the apical cone, a single crest-like body was found and mature spermatids also exhibited transverse intracytoplasmic walls. The morphology and characters of the spermatids in T. crassiceps conform to type III spermiogenesis, which has been described in other taeniids.

Ultrastructure of spermatogonia and spermatocyte lobules in Taenia solium strobilae (Cestoda, Cyclophyllidea, Taeniidae) from golden hamsters

Golden hamsters ( Mesocricetus auratus) were infected with Taenia solium metacestodes dissected from infected pig meat. Adult worms were collected from hamster intestines of animals killed 5-60 days post-infection (dpi), incubated in RPMI 1640 medium with or without colchicine, fixed and processed for transmission electron microscopy (TEM). Sections for light microscopy from 40 different blocks with scolex, immature and mature proglottids were photographed. Thin sections were cut from 25 selected blocks, examined and photographed with TEM. Metaphase mitosis figures were observed in the subtegument of the germinative tissue and interpreted as germ cell precursors. In immature proglottids (20 dpi), discrete cell clusters of three to four cells surrounded by a thin cytoplasmic envelope were identified along the inner border of the lateral excretory ducts. These were also observed in more mature proglottids (40-60 dpi) as clusters of eight cells enclosed in a cytoplasmic envelope, with nuclei of spermatogonia exhibiting the synaptolems of primary meiotic cells. In mature proglottids from 45 dpi, a large number of spermatocyte lobules were found, exhibiting different stages of spermatogenesis from primary spermatocytes to mature filiform spermatids with a single axoneme, annular nucleus and spiral cortical microtubules, similar to spermatozoa described for type III spermiogenesis of species of the family Taeniidae. All mature spermatocyte lobules were enclosed in a highly organized cellular envelope and surrounded by a basal lamina. The envelopes contained a number of distinct organelles, seen in cross-section as discrete lattices of microtubules located between two layers of plasma membrane, as well as thickened furled cytoplasm with numerous strands of rough endoplasmic reticulum and pockets of microtubules.

Effects of cyclosporin-A on immune response, tissue protection and motor function of rats subjected to spinal cord injury

The aim of this work was to test the effect of cyclosporin-A (CsA) on some immunological, morphological and functional aspects developed after spinal cord injury. The specific cellular immune response against spinal cord constituents, the amount of spared tissue and myelination at the site of injury, and the motor function outcome were assessed in a first series of experiments. Rats were subjected to spinal cord compression and treated with cyclosporin-A before lesion and during the entire study. A specific lymphocyte response against spinal cord antigens was found in untreated spinal cord injured rats but not in cyclosporine-A treated injured rats. A significantly better myelination index was also found in injured cyclosporin-A-treated rats, as compared to untreated animals. The amount of spared spinal cord tissue at the epicenter was not significantly different comparing CsA-treated with vehicle-treated rats. Looking for a potential therapeutic use of CsA, in a second series of experiments, rats were subjected to spinal cord contusion and treated with cyclosporin-A from 1 to 72 h after lesion. Motor recovery and red nuclei neurons survival, were evaluated, and found to be significantly better in spinal cord injured rats treated with cyclosporin-A than in injured-untreated rats. This work confirms the existence of an autoimmune cellular reaction after injury that can be inhibited by cyclosporin-A treatment. Furthermore, cyclosporin-A promotes neuroprotection by diminishing both demyelination and neuronal cell death, resulting in a better motor outcome after spinal cord injury.

Acute outbreak of gnathostomiasis in a fishing community in Sinaloa, Mexico

An increasing number of human cases of gnathostomiasis have been reported in Sinaloa, Mexico, most of whom have a custom of eating of raw fish dishes such as 'cebiche'. Here we report five adult patients, three women and two men, having an acute episode of vomiting and abdominal pain a few minutes after eating a dish of cebiche prepared from a spotted sleeper perch (Eleotris picta) fished from a nearby lake in southern Sinaloa. All five patients experienced acute throat pain, chest and joint pains, headache and fever. One patient, a 55-year-old male, was hospitalized with suspected pancreatitis and pneumonia. By 8-9 days later, all five patients developed between three and 12 edematous, migrating skin lesions on the back, abdomen, upper and lower extremities, face, eye and scalp. By ELISA, all of them were sero-positive to Gnathostoma doloresi antigen and had elevated IgE levels. Eosinophilia was found in two patients. These patients lived in an agricultural and fishing community. In this community we carried out a sero-epidemiological survey and study of living conditions in a random sample of 309 individuals distributed in 74 households. Frequent consumption of raw fish was reported in 36% of households, and 12 individuals had a clinical history of migrating skin lesions. The sero-prevalence to Gnathostoma antigens was 34.95%. Five fish species and four species of ichthyophagous birds collected from three lakes in the village and a nearby estuary were infected with the advanced third-stage larvae of G. binucleatum, a species found in Ecuador and Mexico. The results describe the first known outbreak of acute gnathostomiasis on the American continent.

A comparative study of biochemical and immunological properties of triosephosphate isomerase from Taenia solium and Sus scrofa

We produced the Taenia solium triosephosphate isomerase (TPI) in Escherichia coli and compared its biochemical and immunological properties with those of the commercial TPI from Sus scrofa. Taenia solium TPI is a homodimer composed of two 27-kDa monomers, with a specific activity of 5,683 U/mg and a Km value of 0.758, and S. scrofa TPI is also dimeric with similar monomeric molecular weight, specific activity of 4,227 U/mg, and a Km value of 0.51. The catalytic parameters for the isomerization of glyceraldehyde 3-phosphate, affinity between TPI monomers, and kinetic thermal denaturation and inactivation were similar for both enzymes. Anti-T. solium TPI antibodies cross-react weakly with Schistosoma mansoni TPI but do not cross-react with S. scrofa, human, or protozoan TPIs. These antibodies inhibited T. solium TPI activity but did not affect S. scrofa enzymatic activity. Immunizations with 1 microg of the T. solium TPI reduced 52% of cysticerci in a mouse-Taenia crassiceps model 1 mo after challenge. Our findings show that T. solium and S. scrofa TPIs possess similar biochemical and enzymatic properties but do not share immunological properties because anti-T. solium TPI antibodies did not recognize S. scrofa TPI. Inhibition of enzyme activity by anti-TPI antibodies suggests that they can be used as inhibitors of the enzyme.

Ultrastructure of smooth muscle, gap junctions and glycogen distribution in Taenia solium tapeworms from experimentally infected hamsters

Taenia solium adults were grown in hamsters infected by feeding them with cysticerci from pig carcasses. Viable strobilae were collected from the hamster duodenum 20-60 days post-infection, fixed and processed for transmission electron microscopy (TEM). Fourteen strobilae were cut into pieces and embedded in individual blocks. Sections, stained with toluidine blue, were then photographed by light microscopy. Over 1,200 TEM images were obtained from selected blocks. Maturing proglottids exhibited a dense myofilament lattice of connecting fibers, each contained in sarcoplamsic extensions of myocytons and emitting cytoplasmic processes loosely attached to other cells, structures characterized as myocyton-myofilament-pseudopod units, which are interpreted as structures involved in the transport of cells and membrane-bound-glycogen from the germinative tissues to mature proglottids. Densely packed membrane-bound glycogen particles were found between the tegumentary cytons of the neck tissue, and as single-stranded particles between the tegumentary cytons of mature proglottids. These were wrapped around cell bodies in the parenchyma of maturing proglottids and as thin cytoplasmic strands between the testicular lobules of mature proglottids. A large number of cell-to-cell adhesions were identified as gap junctions connected to glycogen strands. We suggest that these are involved in the transport of glucose to differentiating tissues.

Morphology of Gnathostoma spp. isolated from natural hosts in Sinaloa, Mexico

Gnathostomosis is an emerging public health problem in Sinaloa, Mexico, where an increasing number of human cases have been diagnosed since 1989. The present study was carried out to determine the presence of the parasite in other natural hosts from the area. Birds, fish, opossums and raccoons were captured from local dams and lagoons. The flesh from bird and fish specimens was ground and examined under a 100 W light bulb. Larvae were processed for light and electron microscopy. A total of 368 advanced stage 3 (AL3) larvae were found in 300 ichthyophagous birds, with Egretta alba exhibiting the highest infection rate. A total of 4,156 fish were examined, of which six species were infected with AL3 larvae: Arius guatemalensis (blue sea catfish), Dormitator latifrons (Pacific fat sleeper), Gobiomorus sp. (fat sleeper), Oreochromis sp. (Nile tilapia), Cichlasoma beani (Sinaloan cichlid or green guapote) and Eleotris picta (spotted sleeper). Twenty larvae from birds were used to infect domestic cats and dogs. Young adult worms were recovered from the stomach of a cat with a 17 day infection and from a dog with a 35 day infection. Larvae exhibited four rows of hooklets on the head bulb, whereas the young adults had nine rows of hooklets. The cuticular spines of adult worms along the body evolved from single-pointed, bi- or trifurcated spines. Nuclei were counted in intestinal cells examined in serial sections of larvae recovered from a great heron and a fish, in which a mean of 1.6 nuclei/cell was found, corresponding to data published for Gnathostoma binucleatum. Although the external morphology of both larvae and adults are in agreement with previous descriptions of Gnathostoma spinigerum, the results indicate that natural host infections in Sinaloa may be caused by either G. spinigerum or G. binucleatum.

Ultrastructural damage of Trypanosoma cruzi epimastigotes exposed to decomplemented immune sera

The susceptibility of Trypanosoma cruzi epimastigotes to lysis by normal or immune sera in a complement-dependent reaction has been reported, but the effects induced directly by immune serum depleted of complement remain unstudied. The aim of this work was to study the ultrastructural alterations induced in T. cruzi epimastigotes by immune mouse or rabbit sera with or without complement. A local isolate of T. cruzi (Queretaro) was used in all experiments. Immune sera were raised in both mouse and rabbit by immunization with T. cruzi epimastigote antigens. Light microscopy showed intense agglutination of epimastigotes when incubated with decomplemented mouse or rabbit immune sera. A distinctive ultrastructural feature of this agglutination pattern was the fusion of plasma membranes and a pattern of intercrossing between subpellicular microtubules. Agglutination was associated with fragmentation of nuclear membranes and swelling of cytoplasm, Golgi cisternae, endoplasmic reticulum, mitochondria and kinetoplast membranes. Agglutinated parasites also incorporated trypan blue stain. Results of [3H]-thymidine incorporation confirmed that epimastigotes exposed to specific antibodies in the absence of complement were incapable of proliferating. Ultrastructural changes observed in epimastigote micrographs incubated with decomplemented immune mouse sera were statistically significant (P<0.001) when compared with results obtained from images after incubation with decomplemented normal mouse sera.

Taenia solium: germinal cell precursors in tapeworms grown in hamster intestine

BACKGROUND

In a previous study, it was shown that growth of evaginated metacestodes occurs in the germinative tissue of the neck by duplication of somatic stem cells. In these specimens, it was not possible to find the mitotic figures required to demonstrate duplication of germ cell lines.

METHODS

Taenia solium strobilae were collected from the intestinal lumen of outbred hamsters infected orally with 10 metacestodes dissected from naturally infected pigs. Animals were anesthetized 1-10 days postinfection, the small intestine excised, submerged in PBS, and cut open longitudinally. Live Taenias were incubated for 6-8 h in medium containing colchicine or 3H-thymidine, washed, and embedded for electron microscopy. For light microscopy and autoradiography, longitudinal sections were cut from whole blocks and mounted on glass slides. A population of large cells without nuclear membranes and containing discrete aggregates of chromatin were observed apposed to myofibrils in the germinative tissue of the neck. These cells were confirmed by electron microscopy as metaphase mitotic figures, with chromosomes attached to a microtubular spindle, embedded in cytoplasm, without a nuclear membrane, and with characteristic centrioles.

RESULTS

Only tapeworms in which 3H-thymidine was injected directly into the worm tissue by microsyringe were positive by autoradiography, demonstrating that in contrast to evaginated metacestodes, intestinal worms do not transport thymidine across the tegument.

CONCLUSIONS

The results show that differentiating T. solium worms have a subset of stem cells that require passage through a mammalian host to go into mitosis, and that tapeworms grown in an experimental animal do not take up 3H-thymidine in vitro.

Formation of calcareous corpuscles in the lumen of excretory canals of Taenia solium cysticerci

Platyhelminths, like many other organisms, are capable of producing mineral concretions. In cestodes these are referred to as calcareous corpuscles. Studies on these concretions in different cestodes both in vivo and in vitro have resulted in a number of hypotheses on their origin, formation, and structure. Calcareous corpuscles are believed to be of cellular origin, although the kind of cell involved and the mechanisms of mineralization remain under discussion. In the present paper we show that formation of calcareous corpuscles in cysticerci of Taenia solium is not of intracellular origin, as described for other cestodes, but occurs extracellularly in the lumen of protonephridial ducts in a way similar to that proposed for trematodes. This finding enhances the function of the protonephridial ducts, at least in the larvae of T. solium, to the roles formerly ascribed to the calcareous corpuscles.

Clinical manifestations and immunodiagnosis of gnathostomiasis in Culiacan, Mexico

Gnathostomiasis was first described in Mexico in 1970, and endemic areas have been spreading in six states of this country. In Culiacan, Sinaloa, 300 cases of cutaneous larva migrans were recorded between January 1992 and December 1995. In addition, a Gnathostoma larva was surgically removed from the eye of one patient. Cutaneous lesions were observed mainly on the face, neck, arms, and legs. About 70% of the patients showed eosinophilia. A skin biopsy was carried out on 35 patients and the parasite was identified in histopathologic sections of 12 of these patients. In four patients, the larva migrated out spontaneously from the skin. An enzyme-linked immunosorbent assay using a crude somatic extract of adult Gnathostoma doloresi worms showed that 93% of the patients were seropositive, confirming the reliability of clinical diagnosis. A total of 14 advanced third-stage Gnathostoma larvae were found in four species of ichthyophagous birds captured on dams and dikes near the city of Culiacan. Scanning electron micrographs of human and bird larvae showed that they were morphologically indistinguishable from G. spinigerm. We conclude that the life cycle of Gnathostoma has been established in Sinaloa, and has become a serious public health issue for residents.

Taenia solium: description of the intestinal implantation sites in experimental hamster infections

Experimental infections in golden hamsters with viable Taenia solium metacestodes were used to study by light and electron microscopy the implantation site of the adult tapeworm in the intestinal wall. Implantation sites from 3-, 4-, 10-, and 40-day infections were located in the upper third of the duodenum, excised and fixed in Zenker's or Karnovsky's solution, embedded in Polybed resin, and sectioned longitudinally to observe the position of the worm on the intestinal wall. The scolex of the tapeworm was situated between host villi, with the rostellum penetrating the intestinal wall and the suckers entrapping adjacent villi. Serial sections through several whole implantation sites revealed that the worm was anchored to the host by all 4 suckers simultaneously, each of which was located at a different level and had entrapped intestinal villi in its cavity. Host tissue within the suckers was damaged, exhibiting various degrees of cell lysis and necrosis of epithelial and submucosal cells. The tegumentary surface and microtriches of the scolex were well preserved, with occasional coalescence of tegumentary microvesicles in 10- and 40-day-old infections; microtriches were in direct contact with the damaged host tissue. This study is the first morphological and ultrastructural description of the attachment of T. solium to the intestinal wall employing an experimental model, the results of which may contribute to a better understanding of the biology of human tapeworm infections.

Host cells in the spiral canal of Taenia solium (Cestoda) cysticerci

The presence of host inflammatory cells inside the spiral canal of all viable Taenia solium cysts obtained from naturally infected pigs is described. Cells can penetrate into the vicinity of suckers and rostellum, although most appear damaged, suggesting that conditions in the canal are deleterious for them. These observations extend the localization of host inflammatory infiltrate to this intricate microniche, which may offer new approaches for the treatment of cysticercosis, based on a scolex-targeted action. The presence of host cells in the canal of cysts also poses the problem of the resulting contamination with host materials in studies using cysts extracts. As an example, host DNA contamination is readily detectable in genomic DNA isolated from T. solium and Taenia taeniaeformis cysts, as demonstrated by polymerase chain reaction amplification and subsequent sequencing of a segment of the 18S ribosomal gene.

Autoradiographic analysis of the germinative tissue in evaginated Taenia solium metacestodes

Evaginated Taenia solium metacestodes dissected from infected pork meat were incubated in vitro in RPMI 1640 medium with tritiated thymidine, washed, and further incubated for various chase periods. Worms were fixed and embedded in Poly/Bed and sections were processed for autoradiography. Results showed that all longitudinal sections had a germinative region located 500-700 mm posterior to the apex of the scolex with tegumentary cytons arranged in staggered columns perpendicular to the tegument. After 6-hr pulse and 0-12-hr chase periods, a large number of labeled cells were found in the parenchyma and tegumentary wall, included were myocytons, calcareous corpuscle cells, flame cells, osmoregulatory channel cells, and, in the medullary parenchyma, labeled undifferentiated round cells with a large nucleus, prominent nucleolus, abundant ribosomes, and no cytoplasmic organelles. These undifferentiated cells were not labeled after 24-hr and 48-hr chase periods, an observation that strongly suggests these cells divide and migrate toward the tegument in a pattern similar to that described for other cestodes. The morphology and localization of these cells support the view that they are stem cells that give rise to the various cell types of the tegumentary wall. The results indicate that T. solium contains a germinative tissue similar to that described in other cestodes, in which stem cells proliferate continuously, differentiate, and migrate to the tegument, constituting the main process by which these worms develop from metacestode to the adult stage.

Immunosuppression and inhibition of inflammation in mice induced by a small Taenia solium RNA-peptide to implanted T. solium metacestodes

Subcutaneous implantation of Taenia solium metacestodes in mice induces an inflammatory reaction made up mainly of neutrophils and eosinophils after 12 days. Administration of a small RNA-peptide (metacestode factor, MF) purified from T. solium metacestodes significantly reduces the inflammatory site in both size and composition, yielding a very low number of eosinophils. The metacestodes implanted in control mice were completely destroyed and their remnants were surrounded by an intense inflammation predominantly made up of neutrophils and eosinophils. In contrast, metacestodes implanted in mice treated with MF showed apparently intact suckers, rostellum, hooks, and tegument. Inhibition of inflammation around the parasites was also observed in mice immunized with T. solium metacestode antigens and inoculated simultaneously with MF. Mice immunized only with T. solium metacestode antigens produced a granulomatous process around metacestodes that destroyed most of the large metacestode structures: suckers, rostellum, hooks, and tegument-wall tissues. Furthermore, treatment of mice with MF or implanted metacestodes decreased the antibody (P < 0.05) and cellular responses (P < 0.05) to metacestode antigens. The antibody responses was even lower when both of these treatments were given simultaneously. These findings support the idea that MF plays a key role in the down-regulation of the host immune response, contributing to the parasite's survival.

Fermentative and aerobic metabolism in Rhizobium etli

Strains of Rhizobium etli, Rhizobium meliloti, and Rhizobium tropici decreased their capacity to grow after successive subcultures in minimal medium, with a pattern characteristic for each species. During the growth of R. etli CE 3 in minimal medium (MM), a fermentation-like response was apparent: the O2 content was reduced and, simultaneously, organic acids and amino acids were excreted and poly-beta-hydroxybutyrate (PHB) was accumulated. Some of the organic acids excreted into the medium were tricarboxylic acid (TCA) cycle intermediates, and, concomitantly, the activities of several TCA cycle and auxiliary enzymes decreased substantially or became undetectable. Optimal and sustained growth and a low PHB content were found in R. etli CE 3 when it was grown in MM inoculated at a low cell density with O2 maintained at 20% or with the addition of supplements that have an effect on the supply of substrates for the TCA cycle. In the presence of supplements such as biotin or thiamine, no amino acids were excreted and the organic acids already excreted into the medium were later reutilized. Levels of enzyme activities in cells from supplemented cultures indicated that carbon flux through the TCA cycle was maintained, which did not happen in MM. It is proposed that the fermentative state in Rhizobium species is triggered by a cell density signal that results in the regulation of some of the enzymes responsible for the flux of carbon through the TCA cycle and that this in turn determines how much carbon is available for the synthesis and accumulation of PHB. The fermentative state of free-living Rhizobium species may be closely related to the metabolism that these bacteria express during symbiosis.

Purification and ultrastructural localization of surface glycoproteins of Taenia solium (Cestoda) cysticerci

A glycoprotein-enriched fraction was obtained by Concanavalin A-Sepharose 4B affinity chromatography from a crude extract of T. solium cysticerci. The six most prominent glycoproteins with molecular sizes of 180, 103, 96, 68, 55 and 45 kDa were purified by electro-elution from polyacrylamide gel slices. Ultrastructural localization assays using hyperimmune rabbit sera to each glycoprotein, demonstrated their presence on the tegumentary surface of the bladder wall of T. solium cysticerci. Similar studies showed that the 180 kDa glycoprotein is also present on the surface of the T. solium and T. saginata adult worms, as well as in T. saginata, T. pisiformis and T. crassiceps cysticerci. The 55 kDa glycoprotein, which is one of the most abundant on the cyst surface, was found to correspond to the heavy chain of pig IgG by Western blotting.

Taenia solium taeniasis and neurocysticercosis in a Mexican rural family

A case of neurocysticercosis in a six-year-old Mexican boy and a case of Taenia solium taeniasis in his five-year-old brother are reported. Neurocysticercosis was suspected based on clinical findings and was confirmed by computed tomography scanning. A parasitologic examination with zinc-sulfate flotation and formalin-ether sedimentation techniques was carried out on the whole family, and revealed Taenia sp. eggs in three stool samples from the five-year-old boy. The entire family agreed to undergo chemotherapy with niclosamide, but only the child passing taeniid eggs eliminated T. solium. No additional taeniasis cases were found in an examination of 20% of the village population, using the same parasitologic techniques. The results of an ELISA using cysticercus antigens were negative for the boy with neurocysticercosis, for other family members, and for 24 village volunteers, but were positive for the T. solium tapeworm carrier. It was concluded that in this family, person-to-person transmission of the tapeworm occurred due to poor living conditions and hygiene.

Epidemiologic study and control of Taenia solium infections with praziquantel in a rural village of Mexico

This study reports the results of an epidemiologic survey for the detection of Taenia solium in a rural village of 559 inhabitants in Sinaloa, Mexico, as well as a large scale treatment of the population with praziquantel. The study was carried out in two stages. In stage 1, serial stool analysis of 392 persons detected a cluster of three T. solium tapeworms. A fourth T. solium tapeworm was detected through a household census, giving a 1.32% prevalence rate for this helminth. Over 70% of the population over five years of age was treated with a 10 mg/kg dose of praziquantel, and no additional tapeworms were found. Environmental studies for the detection of Taenia sp. eggs in soil, water, and and objects from the houses of tapeworm-infected individuals showed only one soil sample containing eggs compatible with Taenia sp. A total of 72 domestic pigs were examined for the presence of cysticerci under the tongue. One animal had cysts, and belonged to a household that had two T. solium tapeworm infections. Stage 2 of the study was carried out one year after large scale antihelminthic treatment (LSAT), and no infections with Taenia sp. eggs were found. No cysticercus-infected pigs were detected. Intestinal parasitosis decreased from 69.2% to 37.5%. It is concluded that LSAT with praziquantel is efficient in decreasing endemic foci of T. solium. Seropositivity to T. solium bladder fluid antigens was tested by enzyme-linked immunosorbent assay and found to be 11% before LSAT and 7% one year later. In family members living with T. solium tapeworm carriers, the number of seropositive individuals was 28%. The relative risk ratio of seropositivity for persons living in the same household with a T. solium tapeworm carrier was 2.95. Positive response was significantly higher in the 30-39-year-old age group, in which 30% were seropositive in stage 1, compared with 7% one year after LSAT. High seropositivity rates were significantly associated with tapeworm clusters as well as with individuals with a clinical history of seizures.

Paramyosin is the Schistosoma mansoni (Trematoda) homologue of antigen B from Taenia solium (Cestoda)

Antigen B, a major antigen of the cestode parasite Taenia solium, has been purified and a portion of amino acid sequence obtained. Paramyosin of the trematode parasite Schistosoma mansoni, an immunogenic protein that has shown promise as a vaccine candidate, has several biochemical and immunological properties in common with antigen B. A full-length cDNA clone of S. mansoni paramyosin has been obtained and the predicted translation product contains a sequence that is highly homologous to the sequence obtained for antigen B. The predicted amino acid composition and isolectric point of paramyosin are nearly identical to those established for antigen B. Recombinant S. mansoni paramyosin, expressed in Escherichia coli as a fusion protein with beta-galactosidase, was recognized by antisera against T. solium antigen B. We conclude from these results that S. mansoni paramyosin and T. solium antigen B are homologous proteins. Since S. mansoni paramyosin is thought to be a muscle protein and T. solium antigen B a secreted glycoprotein with anti-complement activity, this conclusion raises some interesting questions regarding the role of this class of proteins in the host-parasite relationship.

Crystals of virus-like particles in the metacestodes of Taenia solium and T. crassiceps

Crystals of virus-like particles (VLP) are described as occurring in the nuclei of damaged tegumentary cytons from carcasses of Taenia solium metacestodes that had been stripped of their teguments. The VLP are grouped as parallel lines of round particles in an hexagonal packaging of spheroids forming small or large crystals. The individual particles have an external diameter of 36-37 nm and a wall of 5-6 nm thick, which surround a cavity of lower electron density. As identical crystals were also observed in normal tissues of T. solium and of T. crassiceps, it is suggested that both species of cysticerci are normal carriers of a similar species of virus. The possible biological implications of this condition are discussed.

Serology as an indicator of Taenia solium tapeworm infections in a rural community in Mexico

Serial stool examinations were carried out on a sample of 516 persons living in the town of El Salado (1993 inhabitants). In a group of 40 families (198 individuals), selected by random sampling, there were 2 cases of Taenia solium infection (1.2%); an additional group of 67 families (318 individuals), who volunteered for the study, had 4 cases (1.1%). 5 of the 6 T. solium cases were clustered in 4 neighbouring households. Serum antibodies to the larval stage of T. solium were detected by ELISA using bladder fluid as antigen. 22 members of the random sample group were positive (11%); 58 persons of the total sample of 478 were positive (12%). 43% of individuals living in the same household as a T. solium-infected person were positive, compared to 8.6% seropositive individuals among those not known to have been in daily contact with a T. solium carrier. Odds ratio analysis of the random and total samples showed that the risk of being seropositive when living in the same household as a tapeworm carrier was 9.05 and 6.85 respectively. The results showed a significant correlation between T. solium tapeworm clusters and higher seropositivity rates among contacts rather than among non-contacts. The immune response is a sensitive indicator of a tapeworm infection in a household or family, and is easier to determine than the traditional search for taeniid eggs in stool, a method which is difficult to apply in developing countries due to lack of trained personnel.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning and sequencing of two actin genes from Taenia solium (Cestoda)

Genomic and cDNA actin clones were isolated from Taenia solium gene libraries. The actin genes are interrupted by intervening sequences. Protein coding regions of both genes predict the same amino acid sequence. cDNA sequence data indicate that at least one gene is expressed at the larval stage. Results from Northern and Western blots showed that T. solium expresses an actin transcript of about 1,400 bases and a protein of 45,000 Da.