Evolution of functional diversity in the cupin superfamily

The cupin superfamily of proteins is among the most functionally diverse of any described to date. It was named on the basis of the conserved beta-barrel fold ('cupa' is the Latin term for a small barrel), and comprises both enzymatic and non-enzymatic members, which have either one or two cupin domains. Within the conserved tertiary structure, the variety of biochemical function is provided by minor variation of the residues in the active site and the identity of the bound metal ion. This review discusses the advantages of this particular scaffold and provides an evolutionary analysis of 18 different subclasses within the cupin superfamily.

CM101 treatment overrides tumor-induced immunoprivilege leading to apoptosis

CM101, a bacterial polysaccharide exotoxin produced by group B Streptococcus (GBS), also referred to as GBS toxin, has been shown to target pathological neovasculature and activate complement (C3), thereby inducing neovascularitis, infiltration of inflammatory cells, inhibition of tumor growth, and apoptosis in murine tumor models. Data from refractory cancer patients in a Phase I clinical trial with CM101 indicated a similar mechanism of tumor-targeted inflammation. To further our understanding of the mechanism of action of CM101 as an antitumor agent, we examined the role of the inflammatory response in inducing tumor apoptosis in a normal mouse and tumor-bearing mouse model. The i.v. infusion of CM101 into B16BL-6 melanoma tumor-bearing mice elevated p53 mRNA in circulating leukocytes as measured by reverse transcription-PCR, and immunohistochemistry demonstrated infiltration and sequestration of leukocytes. Whole tumor lysates from excised tumors exhibited an increase in binding to the murine p21(Waf1/Cip1) derived p53 DNA binding sequence compared with control whole tumor lysates, in which minimal or no DNA binding was observed. CM101 infusion led to elevated levels of Fas protein within the tumors as well as a decrease in the expression of fas ligand (fasL). Furthermore, tumors were apoptotic as determined by terminal deoxynucleotidyl transferase-mediated nick end labeling and DNA fragmentation assays. Collectively, these data suggest that CM101 up-regulates p53 in tumor-infiltrating leukocytes, initiating a loss of tumor immunoprivilege and consequently rendering the tumor sensitive to Fas/fasL-mediated apoptosis. CM101 induced loss of tumor immunoprivilege through changes in the expression of leukocyte p53, tumor Fas and fasL coupled with neovascularitis and leukocyte infiltration, constitutes a plausible molecular pathway for tumor reduction observed in cancer patients.

Mutagenesis and kinetic studies of a plant cysteine proteinase with an unusual arrangement of acidic amino acids in and around the active site

We report the cloning, overexpression, kinetic analysis, and modeling of the tertiary structure of an unusual plant cysteine proteinase. Ananain (EC 3.4.22.31), from Ananas comosus (pineapple) is distinguished from all other cysteine proteinases in the papain superfamily by having a unique combination of acidic amino acids. As well as lacking the acidic residue immediately preceding the active site histidine (position 158 in papain), it also lacks the extensive surface network of acidic residues that were postulated to compensate for the loss of charge at position 158 in mammalian cathepsins. Ananain has the fewest acidic residues, so far reported, of any plant cysteine proteinase, but two of the carboxyl residues (E50 and E35) postulated to have an enabling role in catalysis, the so-called "electrostatic switch", remain conserved. Comparisons of the kinetics of recombinant wild-type ananain with E50A and E35A mutants proves that these charged groups are not essential for catalysis. Hence this research does not confirm the presence of an electrostatic switch in this cysteine proteinase, and the role of acidic residues in the enhancement of catalytic competence in these enzymes is discussed in light of this new evidence.

Isolation and identification of the group B streptococcal toxin CM101 from infants with sepsis

OBJECTIVE

To determine whether the group B streptococcal (GBS) polysaccharide exotoxin CM101, which induces a complement-activated cytokine-driven inflammatory response, is present in body fluids of infants with GBS disease.

STUDY DESIGN

With a sandwich enzyme-linked immunosorbent assay, CM101 was measured in plasma, urine, and cerebrospinal fluid from newborn infants who were evaluated for possible infection and from older infants with culture-confirmed GBS disease.

RESULTS

Urine from 11 newborn infants with culture-confirmed early-onset disease contained large amounts of CM101 (1.0 to 5.5 mg/48 h). Plasma concentrations were 62.6 +/- 10.5 microg/mL in these infants and were 69.0 +/- 21.2 microg/mL in 4 older infants with late-onset disease. Plasma CM101 concentrations did not correlate with indexes of illness severity, leukocyte counts, or interleukin-6 or interleukin-8 plasma concentrations. CM101 was present in cerebrospinal fluid of 5 infants with meningitis (8.4 +/- 1.6 microg/mL). CM101 was not found in control samples. CM101 isolated from urine had molecular weight and sugar composition similar to those obtained from GBS culture media, and they both elicited a comparable pathophysiologic response when infused intravenously in lambs.

CONCLUSIONS

CM101 is present in infants with GBS disease, and it appears to be the same as CM101 obtained from GBS culture media.

Phytochrome regulation of phytochrome A mRNA levels in the model short-day-plant Pharbitis nil

The exposure of dark-grown Pharbitis nil seedlings to continuous R induces a rapid decrease in PHYA mRNA abundance with a half-life of about 2 h. A 5 min R pulse also induces this decline, and the effect is partially reversible by subsequent FR irradiation, confirming that the regulation of expression is mediated via the Pfr form of a phytochrome. When de-etiolated seedlings are returned to darkness after a W photoperiod, PHYA mRNA slowly reaccumulates from 20% to 50% of the dark level within 24 h. The rate of reaccumulation is greatly accelerated by the removal of Pfr with a FR pulse, resulting in reaccumulation to 100% within approximately 11 h. Without FR irradiation PHYA mRNA expression remains fully repressed for at least 11 h after the end of the photoperiod, suggesting that the controlling Pfr is highly stable.

Antisera against Periplaneta americana Cu,Zn-superoxide dismutase (SOD): separation of the neurohormone bursicon from SOD, and immunodetection of SOD in the central nervous system

In an effort to characterize the insect molting hormone bursicon from the cockroach, Periplaneta americana, amino acid sequences with high identity of Cu,Zn-superoxide dismutase (SOD) of Drosophila virilis were identified. Antisera against a conserved region of SOD, and a sequence unique to Periplaneta SOD were produced and used to test whether bursicon might be a form of SOD. Western blots of one- and two-dimensional gels revealed that the dimeric form of SOD and bursicon have a similar molecular mass (30 kDa). The two proteins can be separated, however, according to their different isoelectric points. Bursicon is identified in two-dimensional gels by elution from four unique spots not labeled by the anti-SOD antisera. In sections of Periplaneta nerve cords the antisera labeled glial material surrounding neuronal somata close to the neural sheath. Bursicon, however, is contained in unique cell pairs in the ganglia of the ventral nerve cord. These neurons were labeled with new antisera produced against novel sequences of one of the four above-mentioned bursicon active spots. The results show unequivocally that SOD and bursicon are distinctly different proteins. Furthermore, the anti-SOD antisera provided a tool to isolate and sequence bursicon.

Polymerase chain reaction amplification of three different Trypanosoma cruzi DNA sequences from human chagasic cardiac tissue

Chagas' disease is caused by the hemoflagellate protozoan Trypanosoma cruzi. The most common, serious manifestation of Chagas' disease is a progressive inflammatory cardiomyopathy, which occurs decades after primary infection. The inability to consistently demonstrate T. cruzi by histologic techniques in inflammatory cardiac lesions has suggested that the parasites' persistence may not be required for the pathology of the chronic phase. In this report we further analyze the persistence and localization of T. cruzi DNA in the hearts of seven patients with chronic chagasic cardiomyopathy, along with four indeterminate patients and seven control patients seronegative for T. cruzi infection. In the seven patients with chronic chagasic cardiomyopathy, we extracted DNA from selected inflammatory foci-positive (IFP) and inflammatory foci-negative (IFN) areas of' hematoxylin and eosin-stained cardiac tissue. We then used polymerase chain reaction methodology to amplify three different T. cruzi sequences (a minicircle sequence [MCS], a satellite repetitive sequence [RS], and, a low copy number sequence within the gene coding for a flagellar protein [FPS]). The MCS was detected in approximately 100% of both the IFP and IFN areas analyzed. The RS was detected in 37.5% and 23% of the IFP and IFN areas, respectively (difference not statistically significant; P > 0.10, degrees of freedom = 1, G test of independence = 1.9522). The FPS was rarely detected (2%), and was only present in DNA extracted from IFP areas. The MCS was also detected in most indeterminate cases (none of whom had inflammatory lesions) although with a markedly diminished amplification signal relative to cardiomyopathy cases. The MCS was not amplified from the cardiac tissues from seronegative controls. These results suggest that the quantity of T. cruzi DNA persisting in hearts of patients with Chagas' disease correlates with cardiomyopathy, but may not be preferentially associated with inflammatory foci.

Ultrastructural effects of the chelating agent 1,10-phenanthroline on Trypanosoma cruzi epimastigotes in vitro

The in vitro effects of the metal chelator 1,10-phenanthroline (OPHEN) on the ultrastructure of Trypanosoma cruzi epimastigotes were investigated. Epimastigotes treated with OPHEN display swelling and electron-dense deposits in the kinetoplast, mitochondrion, and cisternae of the endoplasmic reticulum. These morphological alterations are dose-dependent and first appear at an OPHEN concentration of 5.0 microg/ml. Analytical electron microscope examination indicates that the metallic portion of the electron-dense deposits is predominantly calcium.

Functional studies on the anti-pathoangiogenic properties of CM101

Group B streptococcus (GBS) isolated from human neonates diagnosed with sepsis and respiratory distress produces a polysaccharide exotoxin (CM101) which has been previously described as GBS toxin. CM101 infused i.v. into tumor-bearing mice causes rapid tumor neovascularitis, infiltration of inflammatory cells, inhibition of tumor growth and tumor apoptosis. CM101 has successfully completed phase I studies in refractory cancer patients with very encouraging results. We have now demonstrated a mechanism of action for CM101. Using a normal mouse tumor model, we have examined tumor and normal tissues which were harvested at 0, 5, 15, 30 and 60min post-infusion of either CM101 or dextran. We present evidence that CM101 is rapidly (within the first 5min) bound to the tumor neovasculature. Complement is activated by the alternative pathway (C3) and leukocytes start to infiltrate the tumor within the first 5min. Through RT-PCR and immunohistochemical techniques, we demonstrate that proinflammatory cytokines, interleukin-6 and tumor necrosis factor (TNF)-alpha, are up-regulated in infiltrating leukocytes and TNF receptor 2 is up- regulated in the targeted tumor neovasculature. Combined, these events constitute possible explanations for the observed pathophysiology of tumor ablation.

Cadmium-induced apoptosis in the urogenital organs of the male rat and its suppression by chelation

Cadmium-induced apoptosis is shown to occur, in vivo, in several organs of the male Wistar rat urogenital system, 48 h after cadmium administration i.p. at a dose of 0.03 mmol/kg. Characteristic DNA fragmentation (as measured by an enzyme-linked immunosorbent-assay, ELISA) and histopathologically observed changes characteristic of apoptosis are found in the kidney, prostate, seminal vesicles, testes, and epididymis. TUNEL assay also demonstrates the apoptosis. Such changes are absent from bladder and vas deferens tissue. Timely administration of an appropriate chelating agent capable of reaching intracellular cadmium binding sites can suppress the processes leading to apoptosis. Administration of monoisomyl meso-2,3-dimercaptosuccinate (Mi-ADMS, 0.5 mmol/kg i.p.) to cadmium-treated rats is effective in greatly reducing typical histopathologic signs of apoptosis and the associated chromatin DNA fragmentation as revealed by ELISA when the antagonist is administered 1 h after cadmium. Administration of the chelating agent at law times results in greater degradation of DNA into oligonucleotides and more prominent histopathological evidence of apoptotic changes in the affected organs of the rat urogenital system. There is also a progressive increase in apoptotic changes indicated by TUNEL assay, as the antagonist is administered at progressively greater intervals after cadmium.

Detection of Trypanosoma cruzi with the polymerase chain reaction and in situ hybridization in infected murine cardiac tissue

Chagas' disease is caused by the hemoflagellate protozoan Trypanosoma cruzi, which is predominantly found in South and Central America and Mexico. Although the parasite is present in the United States, confirmed cases of human disease are rare. The most serious manifestation of chronic Chagas' disease is a progressive inflammatory cardiomyopathy. However, T. cruzi has not been consistently demonstrated with histologic techniques in inflammatory cardiac lesions. In this study, we used both polymerase chain reaction (PCR) amplification of extracted DNA from hematoxylin and eosin-stained tissue scrapings, and in situ hybridization to detect the presence of T. cruzi in infected murine cardiac tissue sections. Three T. cruzi-specific DNA sequences were used: a 122-basepair (bp) sequence localized within the minicircle network (MCS), a 188-bp nuclear repetitive sequence (RS), and a 177-bp sequence within the open reading frame of a gene coding for a flagellar protein (FPS). We found that all three sequences are amplifiable from scrapings of murine cardiac tissue. The MCS and RS are detected at 0.167 and 0.24 amastigote DNA equivalents, while FPS is barely detected at 0.24 amastigote DNA equivalents. On the other hand, in situ hybridization with all three sequences allowed for the detection of T. cruzi amastigotes within the tissue. The MCS and FPS, however, consistently yielded a more intense signal. These results indicate that PCR and in situ hybridization may prove useful in establishing the prevalence of T. cruzi in human chagasic cardiomyopathy.

Synthesis and in vitro trypanocidal activity of some novel iron chelating agents

This report describes the syntheses and in vitro trypanocidal activity of a number of iron (III) chelators against epimastigotes of Trypanosoma cruzi. The compounds examined included a number of lipophilic N-alkyl derivatives of 2-ethyl- and 2-methyl-3-hydroxypyrid-4-ones, N,N'-bis(o-hydroxybenzyl)-(+/-)-trans-1,2-diaminocyclohexane, cyclotetrachromotropylene and four commercially available carboxy derivatives of pyridine, pyrazine, and pyarazole. Benznidazole, the drug clinically used in the treatment of Chagas' disease in humans, served as standard. All compounds were screened in vitro against Trypanosoma cruzi epimastigotes at 50 and 100 micrograms/ml for 72 h of exposure. At 100 micrograms/ml dosage, at least 4 compounds exhibited high epimastigote growth inhibition (65-69%) comparable to benznidazole (72%), whereas 9 compounds showed moderate to fair activity (53-64%) in the in vitro assay. At the lower concentration (50 micrograms/ml), the inhibitory activity of the best of these compounds was reduced significantly (39-48%) compared to the standard drug (59%). The activity of all the carboxylic acids remained in the lower range (4-25%). It is hypothesized that the enhanced activity of some of the compounds is due to their increased lipophilicity which enables them to successfully pass through the cellular membrane of Trypanosoma cruzi epimastigotes. The trypanocidal activities of the most effective compounds were significantly reduced when tested in the presence of added ferric ion.

Phase I study of the antineovascularization drug CM101

CM101 is a bacterial polysaccharide that induces neovascular inflammation in malignant tumors. Fifteen patients with refractory malignancies received CM101 i.v. by a 15-min infusion every other day, three times in 1 week, at doses ranging from 1 unit (7.5 microgram)/kg to 5 units/kg. Serum was analyzed for anti-CM101 IgG and IgM weekly. Plasma levels of inflammatory cytokines, including tumor necrosis factor alpha, interleukin 8, interleukin 10, MIP-1alpha, and soluble E-selectin, were analyzed from -15 min to 12 h during each treatment. Dose-limiting toxicities, including grade IV dyspnea and arrhythmia, were encountered at the 5-unit/kg level. Toxicities occurred primarily within the first 12 h after therapy and included mild-to-moderate fever and chills, nausea, cough, headache, facial flushing, dyspnea, myalgias, and acute tumor-related pain. No patient developed detectable antibodies to CM101. All patients experienced marked time- and dose-dependent elevations in all cytokines studied. Three patients experienced tumor shrinkage. The results show that CM101 can be safely administered at doses that produce evidence for severe, and possibly tumor-specific, inflammation. Further study is necessary to better characterize the mechanism of action and determine the optimal dose and schedule of this new agent.

The in vitro effects of extracellular adenosine triphosphate on the ultrastructure of Trypanosoma cruzi epimastigotes

Incubation for 24 h in culture medium containing 50 mM adenosine triphosphate (ATP) produces distinct alterations in the ultrastructure of Trypanosoma cruzi epimastigotes, most obvious of which is the formation of large membrane-bound vacuoles in the cytosol. These vacuoles become positive following exposure to the macromolecule horseradish peroxidase (HRP). After a 20-min chase in phosphate-buffered saline (PBS) the HRP-positive vacuoles begin to separate into discrete structures such that after a 60-min chase, obvious reservosomes are identifiable. It is hypothesized that extracellular ATP causes increased permeability of the epimastigote's plasma membrane, resulting in ionic fluxes that, in turn, interfere with the normal formation of reservosomes.

Inhibition of Trypanosoma cruzi epimastigotes in vitro by iron chelating agents

The relative effectiveness of 20 iron chelating agents in suppressing the growth and multiplication of Trypanosoma cruzi epimastigotes has been examined in vitro. 1,2-Dimethyl-3-hydroxypyrid-4-one (L1) and several of its newly synthesised N-substituted analogs containing hydrophobic substituents were significantly more effective than deferoxamine, even though they possess only two donor sites for iron(III) while deferoxamine has six. Analogs with hydrophilic substituents were uniformly less active than L1 itself. Variations in effectiveness as the polarity of the compound is varied indicate that the ability to cross the cellular membrane is of critical importance in the determination of the in vitro trypanocidal activity of iron(III) chelating agents. A group of four tris(2-aminoethyl)amine based tris-imines were also screened, all of which had poor activity (0-28% inhibition). Among the other iron(III) chelating agents which showed a relatively high level of activity at 50 and 100 micrograms/ml were salicylhydroxamic acid (70 and 73% inhibition) and hydroxyurea (42 and 52% inhibition). N,N'-Di(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid and acetohydroxamic acid exhibited only slight activity at 50 and 100 micrograms/ml. The best of these iron(III) chelating agents were as effective against the epimastigote form at both 50 and 100 micrograms/ml (74-82% inhibition) as benznidazole (81% inhibition), the drug currently used in the clinic.

In vitro trypanocidal activity of tetraethylthiuram disulfide and sodium diethylamine-N-carbodithioate on Trypanosoma cruzi

Tetraethylthiuram disulfide (disulfiram) (TETD) and sodium diethylamine-N-carbodithioate (DECD) were examined for their in vitro trypanocidal activity against Trypanosoma cruzi. Benznidazole (BNZ), the drug used clinically for the chemotherapy of Chagas' disease, was used as a positive control. Inhibition assays included evaluation against the epimastigote, trypomastigote, and amastigote forms. Tetraethylthiuram disulfide and its reductive metabolite DECD inhibited 64.6% and 69.7%, respectively, of epimastigotes at a concentration of 50 micrograms/ml after 72 hr and BNZ caused 69.1% inhibition at the same concentration. Both TETD and DECD were not as effective against tissue culture trypomastigotes as BNZ (TETD = 47.7%,; DECD = 46.1%; BNZ = 88.7%) at 50 micrograms/ml after 24 hr. However, TETD and DECD treatment of amastigote-infected 3T3 fibroblasts yielded 60 and 67% inhibition, respectively, as compared to BNZ with an inhibition of 62%. A possible mechanism of action of TETD and DECD is via interference with the essential metal metabolism of T. cruci. Since toxicity data for both TETD and DECD are available and both drugs are active against the parasite, these drugs are candidates for further study to determine if they are of potential clinical interest as a prophylactic or therapeutic agent against Chagas' disease.

Antibodies reactive to Trypanosoma cruzi epimastigotes or amastigotes express different idiotypic patterns if from patients with different clinical forms of Chagas' disease

Antibodies (Abs) were purified from pooled sera of patients with either indeterminate (IND or I) or cardiac (CARD or C) Chagas' disease, on either epimastigote (EPI or E) or amastigote-enriched (AMAST or A) antigen (Ag) columns and their idiotypic (Id) expression examined. Anti-Id rabbit Abs were raised to the different preparations (E-IdI, E-IdC, A-IdI and A-IdC). Competitive ELISAs using anti-Ids were able to discriminate between IdI and IdC, disregarding Ag reactivity. E-IdI and A-IdI present different inhibitory abilities, as do E-IdC and A-IdC, but IdC always competes with IdI for anti-IdI comparably. In contrast, a 4-8-fold increase of IdI is required to compete in parallel with IdC for anti-IdC. Therefore, Ids from IND patients share only low levels of the Ids that are most characteristic of CARD patients. While some CARD Abs also express Ids in common with IND patients, these studies reveal that CARD Abs express some Ids that are characteristic to only CARD patients, and these Ids are present on Abs purified with either EPI or AMAST.

An ultrastructure study of the in vitro effects of L-leucine methyl ester and ammonium chloride on Trypanosoma cruzi epimastigotes

Trypanosoma cruzi epimastigotes were subjected to the lysosomotropic agents L-leucine methyl ester and ammonium chloride to determine their effects on the ultrastructure of the parasite. The lysosomotropic agents applied to epimastigotes caused a time-dependent alteration in the morphology of the cells marked by a 5-fold increase in the number of lysosomes. Continued exposure to ammonium chloride caused slight disruption of the reservosomes. The amino acid ester, however, while causing the parasite to swell after prolonged exposure (e.g., 24 h), had little effect on the reservosomes, the kinetoplast, or even the mitochondrion. A specific inhibitor of cysteine proteinases provided some protection for lysosomes from the effects of the amino acid ester. Although it is agreed that reservosomes are similar to endosomes, no lysosomal fusion with the reservosomes was observed. Acid phosphatase activity was observed only in lysosomes.

In vivo studies of cadmium-induced apoptosis in testicular tissue of the rat and its modulation by a chelating agent

In vivo CdCl2-induced apoptotic DNA fragmentation in the testes of the male Wistar rat has been demonstrated on agarose gel. Characteristic DNA migration patterns (laddering) provide evidence of apoptosis (programmed cell death) in testicular tissue of rats administered CdCl2 at a level of 0.03 mmol/kg 48 h previously. Evidence that administration of an appropriate cadmium chelating agent within the first 24 h can suppress some or all of the apoptotic changes in testicular DNA has also been obtained for the first time. A greater reduction in apoptosis is observed as the interval between the administration of the cadmium and that of the chelating agent is shortened. Administration of monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS) to male Wistar rats given CdCl2 is effective in the modulation of the typically apoptotic DNA fragmentation and associated histopathologic injury when the antagonist is given within approximately 1 h after the CdCl2 exposure. When the antagonist is given at later times there is a progressively more pronounced degradation of the DNA into oligonucleotides as seen in the typical electrophoretic DNA ladder pattern found with apoptosis. There is also a progressive increase in histopathological tissue changes as the antagonist is administered at progressively greater intervals after the cadmium.

Chelating agent inhibition of Trypanosoma cruzi epimastigotes in vitro

A number of chelating agents and some of their derivatives are as effective as, or superior to, benznidazole, the compound currently in clinical use, in the suppression of the reproduction of epimastigotes of Trypanosoma cruzi, the protozoa that causes Chagas' disease. All compounds were examined at a culture concentration of 5 micrograms/mL. The most effective compounds included N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine, sodium diethylamine-N-carbodithioate, piperidine-N-carbodithioate and several of its analogs, a number of other carbodithioates with two nonpolar groups on the nitrogen, and tetraethylthiuram disulfide, a prodrug of sodium diethylamine-N-carbodithioate and widely used in the treatment of alcoholism. The introduction of additional ionic or nonionic polar groups on the chelating molecule generally results in a loss of tyrpanocidal activity. Common commercially available chelating agents which exhibited no activity included D-penicillamine, meso-2,3-dimercaptosuccinic acid, and triethylenetetramine tetrahydrochloride. Dose-response data on the culture indicated that some of these compounds exhibited inhibition of Trypanosoma cruzi epimastigotes at concentrations as low as 0.625 microgram/mL. It is proposed that the mechanism of action of these compounds is based on their ability to interfere with the essential metal metabolism at intracellular sites of the epimastigote involving iron, copper, or zinc. The results also indicate that a certain degree of hydrophobicity may be necessary for the groups attached to the literal metal-bonding structure if the compounds are to successfully inhibit the epimastigotes of Trypanosoma cruzi. The development of antiprotozoal drugs which are chelating agents specifically designed to selectively disrupt the essential metal metabolism of Trypanosoma cruzi should furnish a new generation of drugs which can be used in the treatment of Chagas' disease.

In vitro effects of mannan and cytochalasin B on the uptake of horseradish peroxidase and [14C]sucrose by Trypanosoma cruzi epimastigotes

Ultrastructural and quantitative studies were conducted to determine the in vitro effects of mannan and cytochalasin B (CB) on the transport of horseradish peroxidase (HRP) and [14C]sucrose by epimastigotes of Trypanosoma cruzi (strain Y). Time-dependent changes in HRP uptake were observed in cells incubated with the actin inhibitor CB. After 60 min incubation in CB, HRP and sucrose uptakes were inhibited by 48 +/- 15.4% and 16.5 +/- 3.96%, respectively. Morphological changed included HRP reaction product on the cell surface and a reduction in the number of HRP-positive reservosomes when compared to controls. After 120 min incubation, no inhibition was measured for either molecule. However, electron microscopy revealed HRP reaction product on the surface of the cells and in the cytosol. Also, perturbation of the plasma membrane was evident, suggesting that CB compromised the integrity of the plasma membrane, allowing HRP and sucrose to diffuse into the cytosol, giving misleading quantitative results. Mannan displayed a concentration-dependent inhibitory effect on HRP uptake but had little effect on sucrose uptake. Electron microscopic analysis revealed no change in the number of reservosomes per cell but reduction in the amount of HRP in reservosomes concomitant with mannan concentration. These results suggest that T. cruzi epimastigotes transport HRP by receptor-mediated and fluid-phase pinocytosis.

Monoclonal antibodies for structure-function studies of (R)-3-hydroxybutyrate dehydrogenase, a lipid-dependent membrane-bound enzyme

Monoclonal antibodies (mAbs) have been used to study structure-function relationships of (R)-3-hydroxybutyrate dehydrogenase (BDH) (EC 1.1.1.30), a lipid-requiring mitochondrial membrane enzyme with an absolute and specific requirement for phosphatidylcholine (PC) for enzymic activity. The purified enzyme (apoBDH, devoid of phospholipid and thereby inactive) can be re-activated with preformed phospholipid vesicles containing PC or by short-chain soluble PC. Five of six mAbs cross-react with BDH from bovine heart and rat liver, including two mAbs to conformational epitopes. One mAb was found to be specific for the C-terminal sequence of BDH and served to: (1) map endopeptidase cleavage and epitope sites on BDH; and (2) demonstrate that the C-terminus is essential for the activity of BDH. Carboxypeptidase cleavage of only a few (< or = 14) C-terminal amino acids from apoBDH (as detected by the loss of C-terminal epitope for mAb 3-10A) prevents activation by either bilayer or soluble PC. Further, for BDH in bilayers containing PC, the C-terminus is protected from carboxy-peptidase cleavage, whereas in bilayers devoid of PC the C-terminus is cleaved, and subsequent activation by PC is precluded. We conclude that: (1) the C-terminus of BDH is essential for enzymic activity, consistent with the prediction, from primary sequence analysis, that the PC-binding site is in the C-terminal domain of BDH; and (2) the allosteric activation of BDH by PC in bilayers protects the C-terminus from carboxypeptidase cleavage, indicative of a PC-induced conformational change in the enzyme.

An evaluation of the comparative tuberculin skin test for detecting tuberculosis in farmed deer

A comparative cervical skin test using 1.0 mg/ml bovine purified protein derivative and 0.5 mg/ml avian purified protein derivative was evaluated as a method for detecting tuberculosis in farmed deer. A positive comparative cervical skin test reaction was defined as a bovine response with a 2 mm or greater increase in skin thickness which was greater or equal to the avian response. Estimates of the sensitivity of the comparative cervical skin test were obtained from a series of experiments conducted on 60 deer intratracheally inoculated with Mycobacterium bovis. Prior tuberculin skin testing was found to suppress the skin reactivity to a subsequent comparative cervical skin test. This effect was most pronounced at short intervals of 3-7 days, but could still be measured 60 days after the previous test. When the test interval was greater than 60 days, the sensitivity of the comparative cervical skin test was 91.4%. The specificity of the comparative cervical skin test was 98.7% when 1157 deer from 17 uninfected herds with a history of nonspecific skin test reactions were examined. There was no statistical difference in the mean skin thickness increases of three groups of infected animals tested with 2 mg/ml, 0.2 mg/ml and 0.02 mg/ml of bovine purified protein derivative respectively.

PGE2 regulates cAMP production in cultured rabbit CCD cells: evidence for dual inhibitory mechanisms

In cultured cortical collecting duct (CCD) cells, exogenous prostaglandin E2 (PGE2) inhibited arginine vasopressin (AVP)-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) production in a concentration-dependent manner. Although pertussis toxin (PT, 500 ng/ml) alone did not reverse the PGE2-dependent inhibition, PT and staurosporine, a protein kinase C inhibitor, together partially reversed the effect of exogenous PGE2. In contrast, PT completely reversed the inhibition of AVP-dependent cAMP production by sulprostone. These data suggest that exogenous PGE2 can inhibit AVP-stimulated cAMP production and that the inhibitory effects of PGE2 are mediated by staurosporine- and PT-sensitive component(s). Short-term (15-240 min) incubation with phorbol 12-myristate 13-acetate (PMA, 10(-7) M) inhibited PGE2-stimulated cAMP production. Long-term (20 h) incubation with PMA augmented PGE2-stimulated cAMP production. These data provide evidence for the maintenance of a PT-sensitive PGE2-dependent inhibitory pathway of cAMP production in cultured CCD cells. In addition, data are presented that support an inhibitory role for protein kinase C in the effects of PGE2 on the metabolism of cAMP in these cells.

Identification and characterization of an alpha-mannosidase from Trypanosoma cruzi

In this report we describe the first purification and characterization of the acid alpha-mannosidase from the human parasite Trypanosoma cruzi. The purified enzyme exhibited a native mol. wt of 240,000 Da and is apparently composed of four identical subunits of mol. wt 58,000 Da. Each of the four subunits contains one N-linked high-mannose-type oligosaccharide. The alpha-mannosidase exhibited a pH optimum of 3.5 and a pI of 5.9. This low pH optimum and the ability of swainsonine to inhibit its activity suggest that the alpha-mannosidase is a lysosomal enzyme. Antibodies against the T.cruzi enzyme did not react with mammalian lysosomal alpha-mannosidase and, conversely, antibody against a rat lysosomal alpha-mannosidase did not react with the T.cruzi enzyme. Thus, the T.cruzi enzyme appears to be distinct from its mammalian counterpart.

Schistosoma japonicum: excretory-secretory products of the eggs during miracidial development

The release pattern of excretory-secretory (E-S) products of Schistosoma japonicum eggs was investigated using eggs cultured in a chemically defined medium (MEMSE-J) for 16 days. The amount of protein released in culture supernatants was greater in 0- to 4-day and 12- to 16-day cultures than in 4- to 12-day cultures. The protein composition of E-S products and soluble extracts of newly laid eggs (N-SEA) and in vitro matured eggs (M-SEA) was analyzed by SDS-PAGE. Silver staining patterns of N-SEA and M-SEA were found to be similar except for the band at approximately 66 kDa, which appeared in highest concentrations in N-SEA. Western blot analysis with human infected sera showed antibody recognition of a 140- to 160-kDa antigen present in E-S products from mature eggs, while E-S products from immature eggs were unreactive. When either [35S]methionine or [3H]glucosamine was added to the culture medium, newly synthesized proteins or glycoproteins of the SEA and E-S products were labeled. Incorporation of both isotopes into SEA appears to correlate with developmental activity of the eggs. In contrast, release of E-S proteins and glycoproteins is more apparent as the miracidium matures. These results suggested that the source of E-S products from immature eggs is likely to be the collapsing vitelline cells and that of E-S products from mature eggs to be mainly miracidial secretions.

Detection of a circulating antigen in human schistosomiasis japonica using a monoclonal antibody

A double antibody enzyme-linked immunosorbent assay (sandwich ELISA) was used for the detection of a circulating antigen from human schistosomiasis japonica infections. This assay involves the use of polyclonal rabbit Schistosoma japonicum soluble egg antigen (SEA) antiserum to bind circulating antigen and a monoclonal antibody (MabH4) to identify and quantify this antigen. Sera from 108 S. japonicum-infected patients (acute and chronic) were tested. Sera from 93 of 95 patients with chronic infection were positive for this antigen; sera from 12 of 13 patients with acute infections were also positive. Antigen was not detectable in control human sera. Sera from 35 chronic schistosomiasis patients were collected 6-12 months after praziquantel treatment. Circulating antigen was not detectable in the sera of 33 of these patients and was dramatically reduced in 2. This ELISA system may prove valuable in differentiating past and current infections.

The effect of praziquantel on the circulating antigen SJ 70 in murine schistosomiasis japonica

A circulating schistosome 70 kDa antigen (SJ 70) has been detected in the sera of mice infected with Schistosoma japonicum. For the detection of this antigen, a double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was employed. SJ 70 is first detected in the serum of S. japonicum-infected mice 4 weeks after infection. Antigen levels rise rapidly, plateau by 7 weeks after infection, and remain relatively unchanged for at least another 9 weeks. In mice infected with S. japonicum for 7 weeks and then treated with praziquantel (100 mg/kg body weight), there is a significant decrease in serum antigen levels within 2 weeks after treatment, and an almost complete disappearance of antigen from the serum 3-4 weeks after treatment.

Characterization of a large gene family in Schistosoma japonicum that encodes an immunogenic miracidial antigen

Three of eleven clones isolated from a genomic expression library of Schistosoma japonicum DNA using chronically infected human sera also react with chronically infected mouse sera. Characterization of these three clones showed that they contain different members of the same gene family. One clone contains two members of the gene family approximately 2 kb apart and in opposite orientation to each other. DNA sequence homologies between pairs of genes range from 98% to 99.5%. Southern hybridization results indicate there are approximately 40 copies of these genes per haploid genome. Sera from mice immunized with purified fusion protein detected immunoreactive products in the central ganglion and ciliated epidermal cells of miracidia.

Priming with nondepolarizing relaxants for rapid tracheal intubation: a double-blind evaluation

Results of a series of controlled, randomized, double-blind trials investigating intubation conditions with priming sequences of nondepolarizing relaxants are reported. In Phase I of the study the groups received: Group A, tubocurarine (DTC) 3 mg + succinylcholine 1.5 mg.kg-1, Group B, atracurium 0.05 mg.kg-1 + 0.35 mg.kg-1, Group C, vecuronium, 0.01 mg.kg-1 + 0.07 mg.kg-1; in Phase II: Group D, no relaxant, Group E, DTC 0.05 mg.kg-1 + vecuronium 0.07 mg.kg-1, Group F, vecuronium 0.01 mg.kg-1 + vecuronium 0.12 mg.kg-1; in Phase III, Group G, DTC 3 mg + succinylcholine 1.5 mg.kg-1, Group H, vecuronium 0.01 mg.kg-1 + 0.09 mg.kg-1, Group I vecuronium 0.1 mg.kg-1 as a single bolus. Intubation conditions were assessed at 60 seconds. A seven-minute priming interval was used in Phase I and II and a four-minute interval was used in Phase III. Priming produced significantly better intubating conditions than an equivalent single bolus; however, intubating conditions with priming did not appear to match the uniformly excellent conditions produced by succinylcholine. The data suggest that a four-minute priming interval is as effective as a seven-minute interval. The results of this study differed substantially from previous unblinded studies; therefore, it is suggested that a randomized, double-blind design with simultaneous succinylcholine controls be considered a prerequisite for future studies of intubation conditions.

Short interval intradermal skin testing in farmed red deer (Cervus elaphus) inoculated withMycobacterium bovis

Two groups of 26 red deer (Cervus elaphus) were tuberculin skin tested for 41 weeks at three and six week intervals respectively, except at 17 weeks when the internal was two and five weeks. Seventeen weeks after the start of the experiment 36 deer were inoculated intratracheally with Mycobacterium bovis, and the remaining 16 were run in-contact. At six weeks post inoculation, 35 of the 36 inoculated deer reacted to the skin test with a mean skin thickness difference (STD) of 6.3 mm. In inoculated deer further testing led to a suppression of skin sensitivity which was significantly greater in the three-weekly tested group. There was no statistical difference in skin thickness response between 1 and 2 mg/ml bovine purified protein derivative (PPD). Of 454 tests on noninoculated deer (noninfected), 107 produced reactions. These reactions were small and 96% had a STD of less than 2 mm.

Cloning of a Schistosoma japonicum gene encoding a major immunogen recognized by hyperinfected rabbits

A library of randomly sheared Schistosoma japonicum genomic DNA fragments was constructed in the bacteriophage expression vector lambda gt11. A portion of the library was screened with sera collected from rabbits 8 weeks after they were infected with 1000 cercariae. Four clones whose recombinant gene products react with the rabbit sera were purified to homogeneity. Clone SjIR-12A was chosen for detailed study because of its very intense reaction with the rabbit sera. SjIR-12A was found to encode part of a 70 kDa protein (Sj70) that is present in both soluble egg antigen (SEA) and soluble worm antigen preparations (SWAP). Western blot analysis suggests that Sj70 is the only SWAP component that is strongly immunoreactive with the rabbit sera. Rabbit antibodies that react with the SjIR-12A fusion protein were immunoaffinity purified and used to localize immunoreactive product to the nervous tissue of male and female adult worms, the dorsal and lateral tegument of male adult worms, and in eggs to the miracidial tegument and the area between the eggshell and miracidium. Southern hybridization analysis suggests there are approximately four copies of the Sj70 gene per haploid genome.

Modulation of Schistosoma japonicum pulmonary egg granulomas with monoclonal antibodies

We have examined the ability of various Schistosoma japonicum egg antigens to sensitize mice for subsequent secondary pulmonary egg granuloma formation. Further, we produced monoclonal antibodies (Mabs) specific for egg antigens and evaluated their abilities to modulate pulmonary granuloma formation and inhibit soluble egg antigen (SEA)-stimulated lymphocyte blastogenesis. A homogeneous, 140 Kd egg glycoprotein, SJe; 140-GP was nearly as effective as intact eggs in sensitizing for egg-focused pulmonary granuloma formation, while SEA, or the heterogeneous immunoaffinity (IA)-purified C10 antigens were ineffective. The in vivo administration of chronic infection serum (CIS) or Mabs reactive with SJe; 140-GP, to egg-sensitized/egg-challenged mice, modulated pulmonary granuloma formation. Two of these modulatory SJe; 140-GP-specific Mabs (1 A1-1 or 14B3-8), an IgG1, and an IgG3, respectively, did not alter the responses of SEA-stimulated lymph node cells from mice with acute or chronic schistosomiasis japonica. In contrast, another SJe; 140-GP-specific IgG3 Mab (7A6-5), CIS, immunoaffinity purified anti-SEA from CIS, or the non-SEA-binding fraction of CIS, all resulted in dose-related inhibition of SEA-induced proliferation. These data confirm the antibody-driven nature of some immunoregulatory networks in murine schistosomiasis japonica, and extend these observations to include certain Mabs. The immunogenic nature of SJe; 140-GP, and the modulatory and inhibitory activities of Mabs specific for this glycoprotein, indicate it may play a central role in granuloma formation and modulation in this infection.

Collaborative study on antigens for immunodiagnosis of Schistosoma japonicum infection

Six research laboratories in Australia, Japan, the Philippines and the USA participated in a collaborative evaluation of immunodiagnostic tests for Schistosoma japonicum infections. The serum bank consisted of 385 well-documented sera from Brazil, Kenya, Philippines, Republic of Korea and Europe. Twelve S. japonicum antigen/test system combinations were evaluated.Crude S. japonicum egg antigens showed the highest sensitivity and specificity. The defined or characterized antigens showed no advantage over the crude antigens. Quantitative seroreactivity of all S. japonicum antigens showed a positive correlation with faecal egg counts (log x + 1) in all age groups. The performance of the circumoval precipitin test was satisfactory within the same laboratory but with differences in the results between laboratories. A monoclonal antibody used in a competitive radioimmunoassay test system performed as well as the crude egg antigens.The high sensitivity of crude S. japonicum antigens now permits further evaluation for wide-scale use in public health laboratories of endemic areas to support control efforts.

Uptake and excretion of amino acids and utilization of glucose by Schistosoma japonicum eggs

The utilization of amino acids and glucose in the external nutrients and the excretion of nitrogenous compounds by Schistosoma japonicum eggs were investigated with the eggs cultured in a chemically defined medium (MEMSE-J). Of the 15 amino acids in MEMSE-J, arginine and glutamine markedly decreased in concentration during cultivation of S. japonicum eggs. The nitrogenous excretory products of developing eggs were demonstrated to be at least four amino acids (alanine, proline, glutamic acid and ornithine), urea and ammonia. Glucose was consumed at an estimated rate of 32 ng/living egg/day during the period of egg growth and differentiation. When 14C-labelled glucose was included in the culture medium, the radioactivity was incorporated into three amino acids (alanine, proline and glutamic acid), which were excreted by S. Japonicum eggs. The results were discussed with reference to the possible role in stimulating fibrosis in the granuloma of schistosomiasis.

Studies of tolerance in schistosomiasis

We have studied the induction of immune tolerance by exogenous exposure to schistosomal egg antigen (SEA). We compared routes of administration, exposure to different forms of SEA (eggs, normal SEA, reultracentrifuged SEA), and treatment schedules. Tolerance was evaluated in comparison to SEA sensitization, after challenge with SEA or eggs. Anti-SEA responses were measured by ELISA assays, and cell-mediated responsiveness by 24-hr skin tests and pulmonary granuloma formation 8 and 16 days after intravenous egg injection. Oral administration of either SEA in PBS or NaHCO3, or eggs in PBS did not induce tolerance or sensitization. Reultracentrifuged SEA was similar to SEA in inducing cell-mediated immune response. Intrathymic exposure to SEA either had no effect or sensitized the animal for subsequent exposure to SEA. Two intraperitoneal injections of 0.5 to 1.0 mg of SEA lead to reduced cell-mediated responses, but resulted in high levels of anti-SEA antibody, suggesting a state of split tolerance or immune deviation. Our studies suggest that with complex, poorly defined antigens such as SEA, many of the classic methods of eliciting tolerance fail. The biologic significance of the form of tolerance inducible by high doses of SEA remains to be defined.

The molecular biology of schistosomes

Investigators in various laboratories have been studying the molecular biology of schistosome genetics for several years. A recent meeting at the Marine Biological Laboratory in Woods Hole, Massachusetts, USA, sponsored by the Edna McConnell Clark Foundation, brought together 30 scientists from 16 laboratories to share what they have learned from their studies and debate strategies and techniques.

Effects of anti-schistosomal chemotherapy on immune responses, protection and immunity. I. Changes in cellular and humoral responses

The cellular and humoral immune responses of CF1 and C57BL/6 mice with schistosomiasis mansoni were evaluated before and after chemotherapeutic cure of their infections by praziquantel. Mice were infected for either 10 or 20 weeks prior to treatment and followed until 10 weeks after treatment. Peripheral blood eosinophilia, without concomitant general leukocytosis, was observed within 3 days of treatment and persisted for up to 4 weeks. By 6 and 10 weeks after treatment schistosomal-associated hepatosplenomegaly had greatly decreased. Delayed-type hypersensitivity to a soluble adult worm extract (SWAP) was modulated over 20 weeks of infection, and in C57BL/6 mice this modulation was alleviated by cure. In parallel studies of pulmonary egg granuloma formation, granuloma modulation was not effectively reversed. Antibodies against egg (SEA), cercarial (CAP) and adult worm (SWAP) extracts generally decreased by 10 weeks after chemotherapy of mice that were previously infected for 10 weeks. Mice infected for 20 weeks and then treated, generated increased levels of antibodies to SWAP and CAP by 10 weeks after treatment. Immunoglobulin isotypic analyses largely reflected the results of total antibody studies. These data demonstrate that the duration of infection prior to treatment is a determining factor in subsequent expression of immune reactivity, and provide the immunological background for experiments on resistance following chemotherapy of experimental murine schistosomiasis mansoni.