Cysticercus pisiformis-derived novel-miR1 targets TLR2 to inhibit the immune response in rabbits

Cysticercosis pisiformis, a highly prevalent parasitic disease worldwide, causes significant economic losses in the rabbit breeding industry. Previous investigations have identified a novel microRNA, designated as novel-miR1, within the serum of rabbit infected with Cysticercus pisiformis. In the present study, we found that C. pisiformis-derived novel-miR1 was released into the rabbit serum via exosomes. Through computational analysis using TargetScan, miRanda, and PITA, a total of 634 target genes of novel-miR1 were predicted. To elucidate the functional role of novel-miR1, a dual-luciferase reporter assay was utilized and demonstrated that novel-miR1 targets rabbit Toll-like receptor 2 (TLR2). Rabbit peripheral blood lymphocytes (PBLCs) were transfected with novel-miR1 mimic and mimic NC, and the in vitro experiments confirmed that novel-miR1 suppressed the expression of pro-inflammatory cytokines such as TNF-α, IL-1β, and IL-6 through the nuclear factor kappa B (NF-κB) pathway. In vivo experiments demonstrated that novel-miR1 was significantly upregulated during the 1-3 months following infection with C. pisiformis in rabbits. Notably, this upregulation coincided with a downregulation of TLR2, P65, pP65, TNF-α, IL-1β, and IL-6 in PBLCs. Collectively, these results indicate that the novel-miR1 derived from C. pisiformis inhibited the rabbits' immune response by suppressing the NF-κB-mediated immune response. This immune modulation facilitates parasite invasion, survival, and establishment of a persistent infection.

A novel, sequencing-free strategy for the functional characterization of Taenia solium proteomic fingerprint

The flatworm Taenia solium causes human and pig cysticercosis. When cysticerci are established in the human central nervous system, they cause neurocysticercosis, a potentially fatal disease. Neurocysticercosis is a persisting public health problem in rural regions of Mexico and other developing countries of Latin America, Asia, and Africa, where the infection is endemic. The great variability observed in the phenotypic and genotypic traits of cysticerci result in a great heterogeneity in the patterns of molecules secreted by them within their host. This work is aimed to identify and characterize cysticercal secretion proteins of T. solium cysticerci obtained from 5 naturally infected pigs from Guerrero, Mexico, using 2D-PAGE proteomic analysis. The isoelectric point (IP) and molecular weight (MW) of the spots were identified using the software ImageMaster 2D Platinum v.7.0. Since most secreted proteins are impossible to identify by mass spectrometry (MS) due to their low concentration in the sample, a novel strategy to predict their sequence was applied. In total, 108 conserved and 186 differential proteins were identified in five cysticercus cultures. Interestingly, we predicted the sequence of 14 proteins that were common in four out of five cysticercus cultures, which could be used to design vaccines or diagnostic methods for neurocysticercosis. A functional characterization of all sequences was performed using the algorithms SecretomeP, SignalP, and BlastKOALA. We found a possible link between signal transduction pathways in parasite cells and human cancer due to deregulation in signal transduction pathways. Bioinformatics analysis also demonstrated that the parasite release proteins by an exosome-like mechanism, which could be of biological interest.

Oral nitazoxanide treatment of experimental neurocysticercosis induces gluconeogenesis in Taenia crassiceps cysticerci

Neurocysticercosis is the most frequent helminthiasis of the central nervous system and is caused by the presence of Taenia solium cysticerci. Nitazoxanide (NTZ) is an antifolate containing the pyrrolopyrimidine-based nucleus that exerts its antiprotozoal activity due to interference with the pyruvate:ferredoxin oxidoreductase (PFOR) enzyme which is essential to anaerobic energy metabolism. The aim of this work was to determine the effect of NTZ on the energetic metabolism of Taenia crassiceps cysticerci intracranially inoculated BALB /c mice. The infected animals were treated with a single oral dose of NTZ 30 days after the inoculation. Analysis of the organic acids was performed through high performance liquid chromatography. Glucose was detected only in the treated groups, alongside with a significant decrease in lactate, pyruvate and oxaloacetate concentrations which indicate an increase in gluconeogenesis. The non-detection of alpha-ketoglutarate indicated the use of the fumarate reductase pathway in all groups. It was possible to confirm the drugs mode of action due to the non-detection of acetate in the treated groups. There was an increase in the fatty acids oxidation. Therefore it was possible to observe that NTZ induces gluconeogenesis as well as the increase of alternative energetic pathways such as fatty acids oxidation in T. crassiceps cysticerci.

Metabolite pattern ofCysticercus cellulosaemetacestode from different predilection sites of swine using proton magnetic resonance spectroscopy

Cysticercosis due to Taenia solium is one of the most common public health problems in various regions of the world. We have performed prolon magnetic resonance spectroscopy (1H MRS) experiments of the fluid aspirated from cysticerci excised from skeletal muscle (n = 16) and brain (n = 9) of infected swine to compare the metabolite pattern of cysticerci in different predilection sites. Perchloric acid extract of cysticercus cysts excised from skeletal muscles (n = 16) was also prepared to ascertain water-soluble, low molecular weight metabolites using 1H MRS. Absolute quantification and statistical analysis of different metabolites was done to look for any significant differences in different locations of cysts. The metabolite pattern of cysticerci was found to be similar in the various predilection sites. Metabolites observed were leucine, valine, alanine, lysine, glycine, lipid contents, lactate, glutamate, acetate, succinate, creatine, choline, and glucose. Concentration of creatine in cysticercus fluid of cysts removed from the muscle was found to be significantly higher (p = 0.001) than the cysts located in the brain. We conclude that the metabolite pattern in the cysticerci is not influenced by the surrounding tissue location; however concentration of certain metabolites may depend upon the tissue location.

TsAg5, a Taenia solium cysticercus protein with a marginal trypsin-like activity in the diagnosis of human neurocysticercosis

Neurocysticercosis is an endemic parasitic disease caused by Taenia solium larva. Although the mechanism of infection is not completely understood, it is likely driven by proteolytic activity that degrades the intestinal wall to facilitate oncosphere penetration and further infection. We analyzed the publicly available T. solium EST/DNA library and identified two contigs comprising a full-length cDNA fragment very similar to Echinococcus granulosus Ag5 protein. The T. solium cDNA sequence included a proteolytic trypsin-like-domain in the C-terminal region, and a thrombospondin type-1 adherence-domain in the N-terminal region. Both the trypsin-like and adherence domains were expressed independently as recombinant proteins in bacterial systems. TsAg5 showed marginal trypsin-like activity and high sequence similarity to Ag5. The purified antigens were tested in a Western immunoblot assay to diagnose human neurocysticercosis. The sensitivity of the trypsin-like-domain was 96.36% in patients infected with extraparenchymal cysts, 75.44% in patients infected with multiple cysts, and 39.62% in patients with a single cyst. Specificity was 76.70%. The thrombospondin type-1 adherence-domain was not specific for neurocysticercosis.

Utility of a protein fraction with cathepsin L-Like activity purified from cysticercus fluid of Taenia solium in the diagnosis of human cysticercosis

Neurocysticercosis, an endemic parasitic disease in most developing countries, is caused by Taenia solium and compromises the human central nervous system. Cathepsin L-like proteases are secreted by several parasites including T. solium and constitute important antigens for immunodiagnostics. A protein fraction with cathepsin L-like activity was purified from the cysticercus fluid by size exclusion and ion exchange chromatography. Cathepsin L-like activity was measured fluorometrically by detecting the hydrolysis of the fluorogenic substrate Z-Phe-Arg-AMC. The purified protein fraction included antigens of 53 and 25 kD that were tested in a Western immunoblot and in an enzyme-linked immunosorbent assay (ELISA) for detection of human cysticercosis. The sensitivity of the Western immunoblot was 96% for patients infected with multiple cysts and 78% for patients with a single cyst. Specificity was 98%. The sensitivity of the ELISA was 98% in patients with multiple cysts and 84% in patients with a single cyst. Specificity was 92.7%.

[Renaturation, purification and antigenicity identification of recombinant protein of Cysticercus cellulosae expressed in Escherichia coli]

To obtain the recombinant 18 kD protein with high purity and normal bioactivity of Cysticercus cellulosae (rCE18), E. coli cells with the rCE18 were disrupted ultra-sonically, and the inclusion bodies were washed with a solution containing 0.2% deoxycholic acid sodium (DOC)and 2% DOC, respectively. Then they were denatured with 0.9% sodium lauroyl sarcosine (SKL) followed by dialysis and gel filtration to refold and purify the target protein. At the same time, this method was compared with GST-FF affinity chromatography and recovering from SDS-PAGE gel. Biological activity of purified rCE18 was analyzed with indirect ELISA, and the purity of the products was identified using SDS-PAGE. The purity of refolded inclusion bodies exceeded 60% and the total recovery of activated protein rCE18 was about 41.3%. The specificity of rCE18 reached up to 97.2% using indirect ELISA. An effective way for purifying and refolding rCE18 expressed in E. coli as inclusion bodies was established, rCE18 with higher purity and activity was obtained, which has the potential for developing diagnosis methods of porcine cysticercosis.

A novel, cheap and effective fusion expression system for the production of recombinant proteins

To develop faster, less expensive methods for expression and purification of proteins, the annexin B1-intein fusion expression system was constructed. The interest proteins fused to the annexin B1-intein tag were purified in a single-step method based on the Ca(2+)-binding activity of annexin B1, and the annexin B1-intein fusion tag was removed based on the self-cleaving activity of the intein. Moreover, we found that in some cases, fusion to annexin B1 can promote the solubility of heterologous proteins. The production of soluble and highly active of interleukin-2 and low-molecular single-chain urokinase in our results proved that the system was a novel, cheap and effective fusion expression system for the production of valuable soluble recombinant proteins in Escherichia coli.

Taenia solium cysticerci synthesize androgens and estrogens in vitro

Cysticerci from Taenia solium develop in the pig muscle and cause severe diseases in humans. Here we report on the capacity of T. solium cysticerci to synthesize sex steroid hormones. T. solium cysticerci were dissected from infected pork meat. Parasites were incubated for different periods in culture media plus antibiotics and tritiated steroid precursors. Blanks and parasite culture media were extracted and analyzed by thin-layer chromatography (TLC) in two different solvent systems. In some experiments, the scoleces were incubated separately. Results showed that T. solium cysticerci transform [(3)H]androstenedione to [(3)H]testosterone in a time-dependent manner. The production was confirmed in two different solvent systems. The incubation with [(3)H]testosterone yielded only small amounts of [(3)H]androstenedione. The recrystallization procedure further demonstrated that the metabolite identified by TLC was testosterone. The isolated scoleces incubated in the presence of [(3)H]androstenedione yielded [(3)H]testosterone and small quantities of [(3)H]17beta-estradiol. The results reported here demonstrate that T. solium cysticerci have the capacity to synthesize steroid hormones.

Cyanide-resistant respiration in Taenia crassiceps metacestode (cysticerci) is explained by the H2O2-producing side-reaction of respiratory complex I with O2

The nature of the cyanide-resistant respiration of Taenia crassiceps metacestode was studied. Mitochondrial respiration with NADH as substrate was partially inhibited by rotenone, cyanide and antimycin in decreasing order of effectiveness. In contrast, respiration with succinate or ascorbate plus N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) was more sensitive to antimycin and cyanide. The saturation kinetics for O2 with NADH as substrate showed two components, which exhibited different oxygen affinities. The high-O2-affinity system (Km app=1.5 microM) was abolished by low cyanide concentration; it corresponded to cytochrome aa3. The low-O2-affinity system (Km app=120 microM) was resistant to cyanide. Similar O2 saturation kinetics, using succinate or ascorbate-TMPD as electron donor, showed only the high-O2-affinity cyanide-sensitive component. Horse cytochrome c increased 2-3 times the rate of electron flow across the cyanide-sensitive pathway and the contribution of the cyanide-resistant route became negligible. Mitochondrial NADH respiration produced significant amounts of H2O2 (at least 10% of the total O2 uptake). Bovine catalase and horse heart cytochrome c prevented the production and/or accumulation of H2O2. Production of H2O2 by endogenous respiration was detected in whole cysticerci using rhodamine as fluorescent sensor. Thus, the CN-resistant and low-O2-affinity respiration results mainly from a spurious reaction of the respiratory complex I with O2, producing H2O2. The meaning of this reaction in the microaerobic habitat of the parasite is discussed.

Purification of Taenia solium cysticerci superoxide dismutase and myoglobin copurification

Superoxide dismutase from Taenia solium cysticerci ( Ts SOD) was purified by sequential ion exchange chromatography on quaternary-amino-ethyl-cellulose (QAE) followed by hydrophobic interaction on phenyl sepharose (PS) and chromatofocusing on a polybuffer exchanger 94 (PBE). Ts SOD is a 30 kDa molecular weight dimeric enzyme with 15 kDa monomers. It is partially negative, hydrophilic, with 6.3 isoelectric point and has 2,900 U/mg activity. Bovine erythrocyte SOD antibodies cross react with Ts SOD. This enzyme is 80% inhibited by 10 mM of KCN suggesting that it has a Cu/Zn active site. Furthermore, Ts SOD totally loses its activity at 100 degrees C for 4 min. The first 25 amino acids from the Ts SOD N-terminal are (M K A V X V M R G E E G V K G V V H F T Q A G D A). This sequence is 76% similar to the Schistosoma mansoni Cu/Zn SOD. By chance, myoglobin (Mb) was also found during the purification process. A 16 kDa band was recognized in immunoblotting by horse heart Mb antibodies in QAE, PS and PBE, the last-mentioned being found at pH 7.0. The first 15 amino acids from the amino terminal group (G L S D G E W Q L V L N V W G) in this 16 kDa protein are identical to several other Mbs which have been reported.

Human cerebral cysticercosis: immunolocalization of a sodium-dependent glucose cotransporter (SGLT) in larval and adult tapeworms

Light microscopic immunocytochemistry was used to examine human brain cysticerci resected from the fourth ventricles of patients who had not been treated with anthelminthic drugs. Tissues were examined from 3 different patients undergoing surgery for treatment of hydrocephalus. A rabbit polyclonal antiserum to the peptide corresponding to amino acids 564-575 unique to the rabbit sodium-dependent, SGLT1 glucose cotransporter labeled with immunoperoxidase, localized immunoreactive SGLT epitopes. This antibody localizes SGLT1 in the apical brush borders of human enterocytes, but is negative in cytoplasm, as well as lateral and basal enterocyte membranes. Taenia solium neurocysticerci were SGLT positive; transporter protein was highly expressed on the surface microvilli of the external cyst wall. The well-developed network of small and larger osmoregulatory ducts within racemose larval cystcerci displayed high expression of SGLT cotransporter, consistent with a resorptive function for this system of tubules. Because water is cotransported with glucose molecules by the SGLT protein, its high expression in neurocysticerci may contribute to the expansive growth of these larvae in subarachnoid and intraventricular sites. The SGLT epitopes were also immunolocalized in gravid proglottids of Taenia saginata, indicating that cotransporter expression persisted in intestinal-dwelling, adult tapeworms. Cotransporter antibody was abundantly localized at the proglottid tegumentary surface and in the lateral osmoregulatory ducts, analogous to the SGLT localization in cysticerci. Furthermore, high expression of this cotransporter was seen in the branches of the uterus, suggesting that SGLT-mediated absorption of glucose and water has an important functional role within the reproductive system of adult tapeworms.

Sex steroids and parasitism: Taenia crassiceps cisticercus metabolizes exogenous androstenedione to testosterone in vitro

Sex hormones are known to modulate immune responses and may be implicated in sex associated susceptibilities to infections. Taenia crassiceps cysticerci grow to larger numbers in female mice than in males. Gonadectomy alters the course of this infection and hormone replacement with 17beta-estradiol increases the parasite numbers. However, in chronic Taenia crassiceps cysticercosis the sex-hormone profile of males becomes more like that of the females' and progressively loose their sexual behavior. To have further insight in these outstanding endocrinological effects induced by the parasite upon the host, we investigated the parasite's capacity to produce sex steroids. In vitro experiments showed that Taenia crassiceps cysticerci transform 3H-Androstenedione to 3(H)-Testosterone, but not 3H-Pregnenolone. The production of 3H-Testosterone increased when the parasite numbers doubled. A recrystallisation procedure demonstrated that the metabolite identified by TLC was in fact testosterone. Thus, the cysticercus has the ability to use 3H-Androstenedione to make Testosterone possibly by a 17beta-Hydroxysteroid deshidrogenase-like activity in the parasite. In vivo, the parasite could use steroid precursors from the host to produce sex hormones, either accidentally or as needed for its own development, and thus alters the host's normal environment with sexual and immunological repercussions.

A method for the isolation of tegument syncytium mitochondria from Taenia crassiceps cysticerci and partial characterization of their aerobic metabolism

Heterogeneous populations of mitochondria have been described in helminths. Mitochondria from different tissues have been isolated in adult organisms. However, in larvae, due to their small size, isolation from tissues has not been feasible. A method for the isolation of tegumental mitochondria from the larval stage of Taenia crassiceps is described. After solubilization of the plasma membrane with saponin, tegumental mitochondria were purified by a simple and rapid protocol of differential centrifugation, which allowed the retention of suitable quantities of well-preserved mitochondria, as judged by biochemical and ultrastructural parameters. Respiratory activity evoked by exogenous NADH was negligible, but its oxidation increased several-fold after sonication of intact mitochondria. Other substrates, e.g., succinate and malate-glutamate, were oxidized at high rate, leading to the formation of a H+ gradient across the inner mitochondrial membrane, which, in turn, supported oxidative phosphorylation. These results indicate that tegumental mitochondria carry out aerobic metabolism.

Metabolism of [3-(13)C]-pyruvate by cysticerci of Taenia crassiceps

Carbon-13 decoupled 1H spin-echo nuclear magnetic resonance (NMR) spectra, with and without 13C population inversion, of extracts of Taenia crassiceps cysticerci incubated in media containing [3-(13C)]-pyruvate showed 13C enrichment in alanine, lactate, acetate, succinate, and citrate. Labeling in the latter three metabolites provides substantial evidence that the malic enzyme reaction in this cestode also functions in the direction opposite to that in which it is normally portrayed. The direct passage of pyruvate from the cytosol to the mitochondrion is suggested by the greater percentage of 13C detected in acetate relative to succinate.

Alterations in metabolic activity of Cysticercus fasciolaris on some anthelmintic treatments

Effect of candidate compounds 81-470 i.e. methyl [5[4-(2-pyridinyl)-1-piperazinyl]carbonyl]-1H-benzimidazole-2-yl]- carbamate and 86-162 i.e. methyl-5(6)-(alpha-hydroxyphenyl methyl) benzimidazole-2-carbamate along with reference drugs mebendazole and praziquantel on energy metabolism of C. fasciolaris recovered from rats treated with single dose of 500 mg/kg, ip was investigated. All the drugs significantly lowered the rate of uptake of glucose and alanine by the parasite. Suppression in the formation of lactate, the major end-product, was also noticed. Nonetheless the ratio of lactate produced versus the substrates consumed was not substantially affected. The recovered cysticerci also possessed less glycogen and ATP compared to the normal parasites. Although the effects exerted by the drugs were of the identical nature, they significantly differed in the magnitude of their action. Mebendazole followed by praziquantel maximally affected all the above metabolic activities while 86-162 proved to be the weakest in action. The results suggest that the examined drugs exert their chemotherapeutic activity by interfering with uptake of glucose and alanine but do not significantly alter their catabolism.

Praziquantel treatment of porcine brain and muscle Taenia solium cysticercosis. 1. Radiological, physiological and histopathological studies

Porcine Taenia solium cysticercosis, recognized as a model of the human disease, was used to analyze the effect of the anthelminthic drug praziquantel on hosts and parasites. The drug (50 mg/kg daily) was given over 15 days in the feed of 13 cysticercotic and 9 control pigs. Changes in the number, size and appearance of brain parasites were seen by computerized tomography immediately after the last dose of praziquantel, although not all cysticerci had disappeared by day 47 following the end of the treatment. Muscle parasites became small and hyperdense shortly after treatment and disappeared from tomographic images afterwards. No alterations were found in EEGs or in brain-stem auditory and somatosensory evoked potentials. Muscle cysticerci showed increasing degrees of degeneration with time after treatment, and an augmented inflammatory reaction was concomitantly observed. In contrast, more heterogeneous results were obtained in parasites lodged in the brain, since viable cysts and less intense inflammatory reactions were found in the brain at different times after treatment. Physiological evaluation of the parasites showed that evagination was inhibited immediately after treatment and that oxygen consumption decreased with time. The results of this investigation suggest that praziquantel damages cysticerci and that the inflammatory reaction destroys and eliminates them.

Respiratory changes associated with the in vitro evagination of Taenia solium cysticerci

The metabolic adaptability of Taenia solium cysticerci was studied in vitro, by measuring their respiratory rate before, during, and after trypsin-induced evagination. Under aerobic conditions, the oxygen consumption increased about 40% during evagination of the cysticeri and returned to basal rates after the process was completed. The percentage of evagination induced by trypsin was not affected under anaerobic conditions or in the presence of respiratory poisons such as cyanide and carbon monoxide. These data indicate that cysticerci use either aerobic or anaerobic pathways according to oxygen availability in the environment. Results from experiments of irreversible respiratory poisoning using cyanide suggest the presence of an alternative respiratory chain. Proteolytic action of trypsin on a fibrous layer surrounding the invaginated larvae is suggested by histological evidence.

[Fatty conversion of mouse fibroblasts of the L-929 line induced by cysticerci of the cat tapeworm]

Effect of exometabolites of cysticerci of H. taeniaeformis on morphological features of transformed fibroblasts was investigated using L-929 cells. Studies on histochemistry and ultrastructure of L-929 cells treated with the cysticercal exometabolites induced a fatty conversion of these cells. It is proposed that the exometabolites in question may exert their influence on differentiation degree in the in vitro long-term cultivated fibroblasts-like cells.

Analysis of porphyrins and enzymes in porphyrin synthesis in Taenia solium cysticercus from man and pig

Porphyrins and activities of heme biosynthetic enzymes in Taenia solium cysticerci from porcine and human hosts, were examined in order to clarify the possible step where heme synthesis is interrupted. Porphyrins in the vesicular fluid of the parasite were predominantly coproporphyrin, followed by penta-carboxylated porphyrin, which together accounted for 90% of the accumulated porphyrins. Coproporphyrin and penta-carboxylated porphyrin were both type I and III isomers. Small amounts of protoporphyrin and uroporphyrin, and trace amounts of tri-, hexa- and hepta-carboxylated porphyrins were also detected. Fluorescence and phosphorescence spectra and lifetime studies revealed that at least 75% of the porphyrins were bound to metal, probably Zn, while the rest was free. Reverse phase high performance liquid chromatography monitored at an excitation wavelength of 417 nm and at an emission wavelength of 585 nm demonstrated that approximately 90% of these porphyrins were Zn-coproporphyrin. A fluorescence excitation peak at 283 nm with an emission peak at 585 nm and 625 nm indicated that some of the porphyrins were associated with proteins in the vesicular fluid of the parasite. Low levels of delta-aminolevulinic acid dehydratase, porphobilinogen deaminase and uroporphyrinogen decarboxylase activities, and heme concentrations were found in the extract of the parasite walls and scolex, but not in the vesicular fluid. The porphyrin accumulation pattern in this parasite can best be explained by postulating a deficiency of coproporphyrinogen oxidase activity, similar to that in human patients with hereditary coproporphyria. A parasite dissected from a human host was considerably less porphyric than those from pigs, but the pattern of accumulated porphyrins was quite similar in both. In view of their porphyrin contents, T. solium cysticerci could be light sensitive.

In vitro hydroxylation of proline in the collagen of the cysticercus of Taenia solium

1. In vitro hydroxylation of proline in cysticercus collagen was carried out using two different vertebrate enzymes. 2. Chick embryo enzyme is more active on cysticercus collagen than new-born rabbit enzyme. 3. Hydroxylation of cysticercus collagen is more efficient at 40 than at 37 degrees C. 4. No prolyl hydroxylase activity was detected in cysticercus extracts. 5. Collagen from the adult tapeworms Taenia solium and T. saginata lack hydroxyproline. 6. SLS crystallites from T. solium and T. saginata collagen show the same band pattern as cysticercus collagen.

Porphyrin content of the cysticercus of Taenia solium

The strong red fluorescence of the cysticercus of Taenia solium depends on the presence of several porphyrins in the vesicular fluid of the parasite: probably protoporphyrin IX, coproporphyin I or III, and 2 decarboxylated porphyrins intermediate between uroporphyrin and coproporphyrin. Cyst porphyrins associated to form conglomerates of high molecular weight that dissociated in acid solutions and were not antigenic themselves nor associated with antigenic molecules. An appreciable fraction of the porphyrins was capable of undergoing oxidation and reduction, indicating that some of the porphyrins were complexed with metal ions. The metabolic basis for the accumulation of porphyrins is unknown. Preliminary results suggest that conditions deleterious to the cysticercus cause release of porphyrins so that the appearance of porphyrins in the cerebrospinal fluid of neurocysticercotic patients may prove useful in monitoring therapeutic attacks on the parasite.