Distribution of carbohydrates recognized by the lectins Euonymus europaeus and concanavalin A in monoxenic and heteroxenic trypanosomatids

We observed a wide distribution of the carbohydrate epitopes galactosyl alpha(1-3)galactose (gal alpha1-3 gal), alpha-glucoside and alpha-mannoside in mono- and heteroxenic trypanosomatids by using fluorescein-labelled lectins of Euonymus europaeus (EE) and Concanavalin A (Con A) as well as sera from acute chagasic patients who have very high levels of anti-gal alpha(1-3)gal antibodies. The direct fluorescence test for gal alpha1-3 gal with EE was positive at minimum concentrations of 6 micrograms/ml for heteroxenic trypanosomatids and 0.7 micrograms/ml for monoxenic ones and for the plant parasite, Phytomonas. On the other hand, heteroxenic trypanosomatids that infect vertebrates bound ten-fold more Con A than monoxenic flagellates and Phytomonas. These data were confirmed in ELISA and Western Blot assays carried out with peroxidase-labelled EE and Con A. Euonymus europaeus recognized several glycoproteins in all trypanosomatids that we tested. Con A, however, recognized a glycoprotein cluster in heteroxenic protozoa, which ranging from 60-120 kDa, seemed to lack monoxenic parasites and Phytomonas. These findings suggest that alpha-D-mannose and alpha-D-glucose might play an important role in the interaction between trypanosomatids and vertebrate hosts.

Purification of cloned trypanosomal calmodulin and preliminary NMR studies

Cloned trypanosomal calmodulin was expressed in Escherichia coli and purified to homogeneity using hydrophobic interaction chromatography on phenyl-Sepharose. The purified protein was subjected to NMR analysis which allows detailed changes to be observed when, firstly, calcium, and secondly, the drug calmidazolium bind. These spectral changes are the result of conformational changes in the protein and proximity effects due to the drug.

The surface coat of bloodstream forms of Trypanosoma musculi from mice

Iodination and immunoprecipitation techniques together with indirect fluorescent antibody tests identified two polypeptides (SP) of molecular weights 88,000-92,000 and 66,000-70,000 in the surface coat of bloodstream forms of the mouse trypanosome, Trypanosoma musculi. As parasites multiply and enter the early plateau phase of infection the 88,000-92,000 SP is present while the 66,000-70,000 SP is only detectable after the mid-plateau phase. Western blotting of parasite extracts showed that the 88,000-92,000 SP was present throughout the course of infection, but it appears to become masked by the 66,000-70,000 SP or possibly immunoglobulin from about 16 days after infection. Based on results when Western blots of parasite extracts were probed with antibodies affinity purified against the 88,000-92,000 SP, the two SP appear to be immunologically related and the smaller may be a cleavage product of the larger. This would explain why affinity purified antibodies to each SP bound to trypanosomes collected 8 days after infection, when only the 88,000-92,000 is detectable in parasite extracts. However, the failure of antibodies affinity purified against the 66,000-70,000 SP to bind to the 88,000-92,000 SP in Western blots suggests that the smaller SP has some epitopes that are immunologically distinct from those of the larger SP.

Analyses of surface membrane carbohydrates in parasitic flagellates of the order kinetoplastida using lectins

Crithidia fasciculata, Leishmania donovani, Leishmania major, Leishmania mexicana amazonensis, Leishmania tropica, Leishmania tarentolae, Trypanosoma sp. from Formosan bats (Tb), Trypanosoma lewisi, Trypanosoma musculi, and different strains of Trypanosoma cruzi (Tc) were cultivated at 27 degrees C in a liquid culture medium. Flagellates harvested from log phase culture were analyzed for their lectin agglutinating characteristics with concanavalin A (Con A), Peanut agglutinin, Ricinus communis agglutinin 120, soybean agglutinin (SBA), Ulex europeus agglutinin (UEA) and wheat germ agglutinin (WGA). Results indicated that all these flagellates might have D-galactose and methyl- alpha-D-manopyranoside on their surface. The presence of L-Fucose, which complexes specifically with UEA, could not be demonstrated on the surface of these flagellates. Results from quantitative comparison of surface molecules of Tb and the Tulahuen strain of Tc suggested that Tb may have more WGA-binding molecules while Tc may have more ConA-binding molecules. Pretreatment of the flagellates with 0.05% trypsin at 37 degrees C for 30 minutes caused some reduction of agglutination titers. Cell agglutination with lectins was completely inhibited or reversed in the presence of the specific lectin-binding monosaccharides.

Differentiation of rodent trypanosomes of the subgenus Herpetosoma by lectins

Trypomastigote forms of Trypanosoma microti, T. evotomys, T. grosi, T. musculi, and T. lewisi and trypomastigote and epimastigote forms of T. acomys were differentiated using 34 lectins and the Aminoff test for N-acetylneuraminic acid (NANA). Twelve of the lectins failed to agglutinate any of the above species. The number of lectins which agglutinated each species differed; T. mciroti, T. evotomys, T. grosi, T. musculi, T. lewisi and T. acomys (trypomastigote and epimastigote forms) were agglutinated by 7, 14, 7, 13, 11 and (11 and 10) lectins respectively. Some of the lectins were common in agglutinating all species of parasites, for example Bauhinia purpurea, Caragana aborescens and Viscum album. The minimum concentration of lectins which agglutinated each parasite was quite different. The agglutinations were cell body-cell body, flagellum-flagellum or flagellum-cell body. Most of the agglutinations were inhibited by their specific carbohydrates. The lowest concentrations of NANA was observed in T. lewisi (0.3 micrograms/ml) and the highest in T. musculi (4.5 micrograms/ml). The concentrations of NANA in T. microti, T. grosi and in T. acomys (trypomastigote and epimastigote forms) were 2, 1.8, 2.9, and (1.4 and 1.2) micrograms/ml respectively.

Studies on trypanosomatid actin. I. Immunochemical and biochemical identification

In this study, the presence of actin in cultured trypanosomatids was investigated using polyclonal antibodies to heterologous actin. Polyclonal antisera to rabbit muscle actin and a monospecific anti-actin antibody react with a 43-kDa polypeptide in extracts of Trypanosoma cruzi, Herpetomonas samuelpessoai and Leishmania mexicana amazonensis on protein immunoblots. The 43-kDa polypeptide co-migrates with skeletal muscle actin and is retained within trypanosomatid cytoskeletons. Attempts to isolate H. samuelpessoai actin through DNase I affinity chromatography showed that the 43-kDa polypeptide did not bind to the column. Instead, low yields of a 47-kDa polypeptide were obtained indicating that the trypanosomatid actin displays unusual DNase I binding behavior when compared to actins from higher eukaryotes. Immunofluorescence studies confirmed that cytoskeletons retain the actin-like protein. In H. samuelpessoai, actin is localized in the region close to the flagellum, whereas in T. cruzi it is more homogeneously distributed. The data presented here show that trypanosomatid actin displays biochemical characteristics similar to actins of other protozoa.

Characterization of plasma membrane polypeptides of Trypanosoma from bats

Cell surface proteins of Trypanosoma dionisii, Trypanosoma vespertilionis and Trypanosoma sp. (M238) were radiodinated and their distribution both in the detergent-poor (DPP) and detergent-enriched phase (DRP) was studied using a phase separation technique in Triton X-114, as well as polyacrylamide gel electrophoresis in sodium dodecyl sulphate (SDS-PAGE). Significant differences were observed in the proteins present in the DRP when the three species of trypanosoma were compared. Two major bands with 88 and 70 KDa were observed in T. sp. (M238) but were not detectable in T. dionisii and T. vespertilionis. Three polypeptides with 96, 77 and 60 KDa were identified in the DRP of T. vespertilionis. Three major bands with 84, 72 and 60 KDa were observed in the DRP of T. dionisii. Two polypeptides with 34-36 KDa present in the DPP, were observed in the three Trypanosome species analyzed. Our observations show that T. sp. (M238) has characteristic surface polypeptides not found in T. dionisii and T. vespertilionis.

Comparison of several lizard Leishmania species and strains in terms of kinetoplast minicircle and maxicircle DNA sequences, nuclear chromosomes, and membrane lipids

Eight strains of a lizard Leishmania species, L. tarentolae, were compared with four other saurian species [L. hoogstrali, L. adleri, L. agamae and Leishmania sp. LizS], with L. major from man and with Trypanosoma platydactyli, a putative lizard trypanosome, in terms of kinetoplast DNA minicircle and maxicircle sequences and in terms of nuclear chromosome patterns on orthogonal gel electrophoresis. The L. tarentolae strains fell into two major groups, one (group A) consisting of the L. tarentolae strains, UC, Krassner and Trager, derived from an Algerian gecko isolate and the other (group B) consisting of five L. tarentolae LEM strains isolated from geckos in southern France. T. platydactyli TPCL2, which was postulated by Wallbanks et al. to represent the lizard form of a French L. tarentolae strain, was closely related to the UC strain and not to the LEM strains, in all respects analyzed. Leishmania sp. LizS from a Mongolian gecko and L. hoogstrali from a Sudanese gecko showed some sequence similarities to the L. tarentolae strains, but the leishmanias said to be L. adleri from a Kenyan lacertid and L. agamae from an Israeli agamid showed no minicircle sequence similarities with lizard Leishmania and in fact were probably the same species. The maxicircle divergent region was larger in the group B strains than in the group A strains, but there were sequences in common with both groups, and not with L. hoogstrali and L. major. Four strains of L. tarentolae, the four other supposed saurian Leishmania species, three mammalian leishmanias, T. platydactyli and four other trypanosomes, T. cyclops (Malaysian macaque), T. conorrhini (Hawaiian reduviid bug), T. cruzi (man) and T. lewisi (feral rat) were analyzed for their contents of sterols and phosphoglyceride fatty acyl groups. T. platydactyli TPCL2 contained a sterol (5-dehydroepisterol), a phosphatidylcholine fatty acyl group (alpha-linolenic acid) and a phosphatidylethanolamine fatty acyl group (dihydrosterculic acid) characteristic of members of the genus Leishmania and not the genus Trypanosoma. The proportions of those lipids in the free sterol and phosphoglyceride fractions of T. platydactyli TPCL2 most closely resembled those seen in the Leishmania strains from Algerian, French, Mongolian and Sudanese geckos.

Structural features and antigenic properties of carbohydrate-containing components of Trypanosoma conorhini

Aqueous and phenolic extracts of Trypanosoma conorhini were fractionated and high molecular weight, carbohydrate-rich fractions obtained. Their antigenic characteristics, reactivity with lectins and partial chemical structure were determined. The major component, the phenolic extract, was electrophoretically diffuse and consisted of 15% protein, 5% phosphorus, hexosamine, and 67% neutral carbohydrate, which contained mannose, galactose, and xylose in a molar ratio of 1.0:1.8:1.8. Chemical analyses and lectin agglutination experiments showed nonreducing end-groups of beta-D-galactopyranose, beta-xylopyranose, and alpha-D-mannopyranose. Phosphate esters occurred, apparently, at O-6 of hexopyranosyl units. Hexosamine was present as nonacetylated units of 2-amino-2-deoxy-alpha-D-glucopyranosyl units that were extremely resistant to acid hydrolysis. On double immunodiffusion tests, the major component gave a precipitation line with rabbit serum against whole cells of Trypanosoma cruzi, suggesting the presence of common antigenic determinant(s) on the cell surface of each trypanosomatid.

Secondary structure of the variant surface glycoproteins of trypanosomes

The secondary structure of seven variant surface glycoproteins (VSGs) of trypanosomes has been determined by Raman spectroscopy. They are all predominantly alpha-helical, the alpha-helix content varying between 50 and 60%. The beta-strand content varies between 20 and 25%, and the content of beta-turn and nonregular structures is about 25%. For three VSGs the N-terminal domain obtained by proteolytic cleavage was found to have essentially the same secondary structure as the complete VSGs. For three VSGs a secondary structure prediction has been performed applying the rules of Chou and Fasman. In all cases, two long alpha-helices extending over about 50 residues or 80 A are predicted in agreement with the X-ray diffraction data of Freymann et al. [(1984) Nature 311, 167-169] and Metcalf et al. [(1987) Nature 325, 84-86]. The region between the two alpha-helical segments exhibits a high potential of beta-turns, suggesting that this segment may be exposed on the cell surface and carry major antigenic determinants.

Further characterization of carbohydrate-containing fractions from Trypanosoma mega

Epimastigotes of Trypanosoma mega were submitted to phenol extraction after lipid extraction, providing an extract whose carbohydrate portion (30%) contained fucose, ribose, xylose, mannose, galactose, and glucose. The purified fraction recovered in the void volume of Bio Gel P-150 gave on SDS-PAGE a band of Mr approximately equal to 55,000 positive for protein and carbohydrate and a diffuse band strongly positive for carbohydrate and lipids (Mr approximately equal to 22,000). The structural analysis of the carbohydrate moiety of this fraction by GLC-MS indicated the presence of nonreducing end groups of fucopyranose, mannopyranose, and galactopyranose, 3-O- and 4-O-substituted and 2,3- and 2,4-di-O-substituted galactopyranosyl units. Extraction of this fraction with chloroform/methanol/water provided a soluble fraction that on SDS-PAGE gave rise to a carbohydrate and lipid-positive band (Mr approximately equal to 22,000). This fraction contained fucose, mannose, and galactose (1:1:1). As main branch points, 2,3-di-O-substituted galactopyranosyl units were present according to methylation data. Similar proportions of fucopyranosyl, mannopyranosyl, galactopyranosyl end units were present. The presence of lipids in this fraction was confirmed by methanolysis following isolation and characterization of the corresponding fatty acid methyl esters. Palmitic acid (16:0) and an 18:1 fatty acid were the predominant fatty acids.

Glycosyl-sn-1,2-dimyristylphosphatidylinositol is the membrane anchor for Trypanosoma equiperdum and T. (Nannomonas) congolense variant surface glycoproteins

We have analysed the structures of the Trypanosoma (Nannomonas) congolense and T. equiperdum variant surface glycoprotein (VSG) membrane anchors. Myristic acid uptake, phospholipase treatment, and nitrous acid deamination showed that, for each species, the anchor is glycosyl-sn-1,2-dimyristylphosphatidylinositol, as has been previously described for T. brucei. Osmotic lysis of these trypanosomes resulted in the release of soluble VSG, lacking fatty acid. In both species and in T. evansi, an endogenous phospholipase C, which cleaved diacylglycerol from membrane form VSG, was identified.

Ultrastructural visualization of lipids in trypanosomatids

An imidazole-buffered osmium tetroxide solution was used to visualize lipids at the ultrastructural level in the following members of the family Trypanosomatidae: Trypanosoma cruzi, T. dionisii, T. vespertilionis. T. rangeli, Crithidia deanei, C. fasciculata, C. oncopelti, and Blastocrithidia culicis. Electron-dense material was seen in various lipid droplets found in all parasites and in the multivesicular structure of members of the sub-genus Schizotrypanum. High contrast of some membranes, mainly those which enclose the mitochondrion, the nucleus, and the endoplasmic reticulum, was observed even in unstained sections. X-ray microanalysis confirmed that the electron density of lipid droplets of B. culicis and membrane-bounded dense granules of C. oncopelti was due to the presence of osmium.

Identification and isolation of a variant surface glycoprotein from Trypanosoma vivax

The protozoan Trypanosoma vivax is one of the most important agents of African trypanosomiasis, a disease that hinders the productive use of livestock in one-third of the African continent. Trypanosoma vivax is also present in the Caribbean and in South America, posing a threat to the livestock industries of the tropical and subtropical world. Much less is known of the biology of this trypanosome than of the better studied T. brucei and T. congolense. One of the variant surface glycoproteins (VSGs) of a West African stock of T. vivax was identified, purified, and partially characterized by the use of a combination of highly resolving techniques to maximize information from the relatively small amount of parasite material available. The molecular weight of the isolated protein (46,000) is smaller than that of VSGs from other species. As with T. brucei VSGs the protein from T. vivax is complexed with sugars and incorporates 3H when living trypanosomes are incubated with [3H]myristic acid, but the T. vivax molecule is more hydrophobic than the T. brucei molecule. The small size of the T. vivax VSG may have a bearing on the functional and evolutionary relationships of variant antigens in trypanosomes.

Characterization of a 19,000 mol. wt. flagellum-specific protein of Trypanosoma cruzi, T. dionisii and T. vespertilionis by a monoclonal antibody

The flagellum-specific monoclonal antibody VESP 9.1 raised against Trypanosoma vespertilionis reacts with a single protein band of 19,000 mol. wt.. This antigen is present on the flagellum of T. cruzi, T. dionisii and T. vespertilionis as well on the epimastigote and the metacyclic trypomastigote developmental stage. A comparative study using indirect immunofluorescence with 15 different trypanosomatids confirmed the specific reactions.

Isolation and characterization of a neutral glycosphingolipid from the epimastigote form of Trypanosoma mega

A glycosphingolipid fraction from Trypanosoma mega was isolated after acetylation and was further purified on a silicic acid column. Final purification was by preparative thin-layer chromatography. The carbohydrate components of the glycolipid were fucose and galactose in approximately equimolar amounts. The neutral glycolipid of T. mega has a sphingosine base composition that consists of sphingosine and traces of dihydrosphingosine. Fatty acids forming amide groups with the sphingosine bases were analyzed by gas-liquid chromatography-mass spectrometry and are a mixture of normal and alpha-hydroxy fatty acids. Normal C16:0, C18:0, and 2-hydroxy C18:0 are the predominant fatty acids.

Cytofluorometry as a method for the differentiation of trypanosomes

The DNA binding guanine specific antibiotic, chromomycin A3, has been evaluated for fluorescence intensity measurements of T. cruzi, T. brucei brucei and T. musculi. Optimal fixation and staining conditions have been determined. The fluorometry was performed with a microscope photometer equipped with electronic systems for short time excitation of 7 milliseconds and operation control. The trypomastigote bloodstream forms of these species have a different chromomycin specific DNA content. The total DNA content of T. cruzi was 2.1-fold higher than for T.b. brucei and 2.3-fold higher than for T. musculi. The nuclear DNA content also was higher in T. cruzi. The nuclear DNA values were recorded to be 1.6-fold greater than in T.b. brucei and 2.0-fold greater than in T. musculi. The amount of the kinetoplast DNA of T. cruzi was shown to be 3.2-fold higher than in T. musculi and 11.7-fold higher than in T.b. brucei. The higher total DNA of T.b. brucei in relation to T. musculi was based on the nuclear values because the content of the kinetoplast DNA of T.b. brucei was 3.7-fold smaller than of T. musculi. The kDNA comprised 25% in T. cruzi, 18% in T. musculi and only 4% in T.b. brucei of the total amount of the chromomycin specific DNA. The chromomycin fluorescence intensities of the DNA of trypanosomes were subjected to a statistical model of discriminant analysis. It was possible to get perfect separation of the three trypanosome species. The hit rate was 100%.

Purification of major variable-surface glycoproteins from African trypanosomes by reverse-phase high-performance liquid chromatography

Reverse-phase high-performance liquid chromatography (RP-HPLC) was used in a one-step procedure to purify and analyze several different major variable-surface glycoproteins (VSGs) from lysates of African trypanosomes. RP-HPLC was used to fractionate lysates of trypanosomes and the VSG localized to the major peak of the elution profile using a rabbit antiserum to the cross-reacting determinant of the VSG. Polyacrylamide gel electrophoresis of HPLC fractions showed that the purity of isolated VSGs was equivalent to or better than that attained using conventional purification procedures. The elution positions of purified VSGs from a variety of cloned trypanosomes were identical, indicating the presence of a common hydrophobic feature on the surface of these highly polymorphic antigens. Preliminary experiments have shown that purification of VSG from trypanosome lysates may be scaled up to preparative levels. The results show that RP-HPLC is a useful procedure for rapid preparation of highly purified trypanosome VSGs and that analysis of their various molecular forms will be facilitated by the application of HPLC methods.

Differentiation between Trypanosoma cruzi and Trypanosoma rangeli on the basis of their sialic acid content

Four day-old culture forms of Trypanosoma rangeli strain San Augustin were tested with the following lectins: Canavalia ensiformis, Pisum sativum, Ricinus communis-120, Sojahispida, Aaptos papillata II, Triticum vulgaris, Limulus polyphemus, lberis amara and Arachis hypogaea. These flagellates were only agglutinated by the lectins from Canavalia ensiformis and Pisum sativum. Furthermore four day-old culture forms of the T. cruzi strains Morcego 1354, P-60, Téhuantépéc and WA 301/130 as well as the T. rangli strains San Augustin, Venezuela and DA-3412 were treated with neuraminidase and the supernatant examined by the Aminoff TBA assay. While the supernatant of the T. cruzi strains showed a red colour complex the supernatant of the T. rangeli strains was weak yellow-green. In contrast to the T. cruzi strains no N-acetylneuraminic acid was detectable on the cell surface of T. rangeli. Therefore the Aminoff test can be used for the differentiation between T. cruzi and T. rangeli.

Amino terminal sequence homology among variant surface glycoproteins of African trypanosomes

Amino terminal amino acid sequences were determined for eight variable surface glycoproteins purified from successive parasitemias of cloned Trypanosoma brucei. These sequences were compared by sequence alignment analysis with each other and with amino terminal sequences of variable surface glycoproteins from other clones of T. brucei, T. congolense and T. equiperdum. Contrary to previously held views, a remarkable degree of sequence homology was found among all sequences. In several cases the homology was greater between glycoproteins from different species than between glycoproteins isolated from successive parasite peaks, suggesting a common primordial gene for trypanosome variable surface glycoproteins. This amino terminal homology, taken together with homologies found in other regions of variant surface glycoproteins strongly suggests that their tertiary structures are conserved.

Presence of a bent helix in fragments of kinetoplast DNA minicircles from several trypanosomatid species

Some restriction fragments of kinetoplast minicircles from several trypanosomatid species (Leishmania tarentolae, Trypanosoma brucei, T. equiperdum, Herpetomonas muscarum, Crithidia fasciculata, but not T. cruzi) migrate anomalously on polyacrylamide gels. This behavior is probably due to a natural curvature of the helix. Bent helices appear to be a common property of kinetoplast minicircles, and may be important for minicircle function. In the case of T. equiperdum, we present evidence that each minicircle has a single bent region which resides in or near the 'conserved sequence.'

Interspecific differentiation of Trypanosoma cruzi, Trypanosoma conorhini and Trypanosoma rangeli by lectins in combination with complement lysis

Four-day-old epimastigote culture forms of Trypanosoma cruzi, Trypanosoma rangeli and Trypanosoma conorhini were tested with 21 lectins. Furthermore T. conorhini was incubated with the following sera: rat, Wistar HAN, germ free; normal fresh hen, rat and human serum. T. rangeli was agglutinated only by the D-mannose specific lectins from Canavalia ensiformis and Pisum sativum. T. cruzi and T. conorhini could be distinguished by the lectin from Tridacna crocea. The epimastigote culture forms of T. conorhini were not lysed by normal fresh rat, hen and human sera. Therefore, T. cruzi, T. conorhini and T. rangeli can be distinguished interspecifically by lectins and by the different lytic effect of rat, hen and human sera. It is possible to separate each of the species by complement lysis. The lysis-resistant species can be cultivated for further examinations.

The surface of the African trypanosomes

The African trypanosomes bear on the outside of their cell membrane a single 10-15 nm thick coat of a glycoprotein. This glycoprotein may differ in structure in the predominant populations of parasitemic waves found in relapsing infections. Variant Specific Glycoprotein (VSG) range in MW between 53,000-63,000 d and may have variable amounts of carbohydrate attached at one, two, or several loci. Such differences in carbohydrate content may account in part for their range in molecular size. Approximately 30 C-terminal residues demonstrate isotypy ; i.e. these regions fall into classes having similar amino acid sequence. Modest homology has been demonstrated in two VSGs of T. congolense arising in relapsing infections although comparison of many VSG show little or no obvious homology. More recently, lipid-associated forms of VSG have been described and it is believed that these forms may be transmembrane proteins. Different VSGs appear to have different amounts of the primary sequence which have alpha-helix-forming potential. In some VSG, in excess of 80% of the structure is helical as judged by both Chou-Fasman calculations and by circular dichroism. This raises the possibility that different VSG may have different folding patterns. The arrangement of VSG on the trypanosome surface probably places the basic amino acid-rich carbohydrate-bearing C-terminus of the polypeptide chain close to the membrane. There is some protein-protein association between VSGs for which (in T. evansi) the C-terminal tail is not required. The importance of VSG structure lies not only in the fact that the molecule mediates the phenomenon of antigenic variation but also in the recent observation that VSG may act on the cellular immune system to suppress the humoral immune responses of the host.

Trypanosoma rhodesiense bloodstream trypomastigote and culture procyclic cell surface carbohydrates

Bloodstream trypomastigote and culture procyclic (insect midgut) forms of a cloned T. rhodesiense variant (WRAT at 1) were tested for agglutination with the lectins concanavalin A (Con A), phytohemagglutinin P (PP), soybean agglutinin (SBA), fucose binding protein (FBP), wheat germ agglutinin (WGA), and castor bean lectin (RCA). Fluorescence-microscopic localization of lectin binding to both formalin-fixed trypomastigotes and red cells was determined with fluorescein isothiocyanate (FITC)-conjugated Con A, SBA, FBP, WGA, RCA, PNA (peanut agglutinin), DBA (Dolichos bifloris), and UEA (Ulex europaeus) lectins. Electron microscopic localization of lectin binding sites on bloodstream trypomastigotes was accomplished by the Con A-horseradish peroxidase-diamino-benzidine (HRP-DAB) technique, and by a Con A-biotin/avidin-ferritin method. Trypomastigotes, isolated by centrifugation or filtration through DEAE-cellulose or thawed after cryopreservation, were agglutinated by the lectins Con A and PP with agglutination strength scored as Con A greater than PP. No agglutination was observed in control preparations or with the lectins WGA, FBA or SBA. Red cells were agglutinated by all the lectins tested. Formalin-fixed bloodstream trypomastigotes bound FITC-Con A and FITC-RCA but not FITC-WAG, -SBA, -PNA, -UEA or -DBA lectins. All FITC-labeled lectins bound to red cells. Con A receptors, visualized by Con A-HRP-DAB and Con A-biotin/avidin-ferritin techniques, were distributed uniformly on T. rhodesiense bloodstream forms. No lectin receptors were visualized on control preparations. Culture procyclics lacked a cell surface coat and were agglutinated by Con A and WGA but not RCA, SBA, PP and FBP. Procyclics were not agglutinated by lectins in the presence of competing sugar at 0.25 M.(ABSTRACT TRUNCATED AT 250 WORDS)

Presence of glycerol and fatty acids in the C-terminal end of a variant surface glycoprotein from Trypanosoma equiperdum

The composition of the C-terminal end of a variant surface glycoprotein from Trypanosoma equiperdum (BoTat-1 VSG) has been examined. It has been reported for two Trypanosoma brucei VSGs (Holder, A.A., Biochem. J. (1983), 209, 261-262) that ethanolamine was involved in binding the C-terminal amino acid to an oligosaccharide side chain. Tryptic glycopeptides were prepared from BoTat-1 VSG and analyzed. One of them was found to contain ethanolamine and consequently was assumed to be C-terminal. It was shown that the glycopeptide also included phosphate, glycerol and fatty acids. The fatty acid composition was representative of that of glycerolipids. All the results suggest that the end of the molecule is a core of phosphatidylethanolamine.

Differentiation of Trypanosoma cruzi Chagas, 1909 and Trypanosoma vespertilionis Battaglia, 1904 by various lectins

Four-days-old culture forms of Trypanosoma cruzi (strain Téhuantépéc, Guatemala) and Trypanosoma vespertilionis (strain P-14, P-9) were tested by 19 carbohydrate-specific agglutinins. The T. cruzi strains are interspecifically distinguishable with the lectins from Euonymus europaeus, Tridacna crocea, Tridacna maxima and the human blood-group testserum anti-B from the T. vespertilionis strains. While the T. vespertilionis strains did react with anti-B and E. europaeus, the T. cruzi strains did not agglutinate. The T. cruzi strains were agglutinated by the lectins from T. crocea and T: maxima while the bat-trypanosomes showed no reactions. Using these lectins it was not possible to distinguish the bat-flagellates intraspecifically. With the lectins from Triticum vulgaris and Arachis hypogaea the T. cruzi strains could be distinguished. While the Ténuantépéc strain did agglutinate with A. hypogaea, T. cruzi strain Guatemala did react only with the lectin from T. vulgaris. The bat-trypanosomes were agglutinated only by A. hypogaea but not by T. vulgaris. The reactions of these trypanosome-species with A. papillata and T. vulgaris demonstrate that both trypanosome species have N-acetylneuraminic acid on their cell surfaces.

Partial determination of the primary structure of a variant surface glycoprotein from Trypanosoma equiperdum. Composition and location of a carbohydrate moiety

Salivarian trypanosomes have the ability to evade the immune response of their hosts by the sequential expression of different cell surface glycoproteins. Among the isolated specific antigens from cloned variants of Trypanosoma equiperdum, a structural study was undertaken on two immunologically cross-reacting variant surface glycoproteins, and results concerning the basic antigenic type are reported. The glycoprotein was cleaved by cyanogen bromide, and amino acids of several purified fractions obtained by gel filtration chromatography of this cleavage mixture were sequenced by automated Edman degradation. Sequencing in particular allowed the identification of the N-terminal portion of the molecule (residues 1-74). Sugar compositions of the fractions have demonstrated the presence of at least two carbohydrate moieties in the glycoprotein. Using a subsequent enzymatic subcleavage we were able to locate the first glycosylation site in position 57. An important observation was that the first oligosaccharide identified was rich in mannose and devoid of galactose.

The fatty acids of Trypanosoma vivax

A study was carried out to determine the lipid composition of the blood-stream form of the African trypanosome. Trypanosoma vivax. Data from thin layer chromatography showed that the major polar lipids were lysophosphatidylcholine, sphingomyelin, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and diphosphatidylglycerol. The major neutral lipids were sterol, monoacylglycerol, diacylglycerol, free fatty acid and triacyglycerol. 16:0, 18:0, 18:1 and 18:2 constituted the major fatty acids of both the polar and neutral lipid fractions. The work constituted the first detailed study on the fatty acid composition of this African trypanosome.

Comparative studies of Trypanosoma cruzi and T. cruzi-like stocks from different South American countries using lectins

The agglutination behaviour of four-day-old epimastigote culture forms of 34 Trypanosoma cruzi, and T. cruzi-like stocks from Brazil, Chile, Colombia, Ecuador and Peru were tested with 15 carbohydrate-specific lectins. We distinguished intraspecifically two groups of agglutination reactions: Group 1 includes stocks which react with Triticum vulgaris and Aaptos papillata II (wheat germ agglutinin: WGA-type). Group 2 includes stocks agglutinated by Arachis hypogaea and Aaptos papillata II (peanut lectin: PNA-type). The agglutination reactions with lectins from Triticum vulgaris and Aaptos papillata II correlate with the presence of N-acetylneuraminic acid on the cell surface. After treatment with neuraminidase, the WGA-type is agglutinated by PNA but not by lectins from Triticum vulgaris and Aaptos papillata II. Further results demonstrate that a certain zymodeme pattern can be correlated with carbohydrate determinants.

Electrophoretic analysis of endonuclease-generated fragments of k-DNA, of esterase isoenzymes, and of surface proteins as aids for species identification of insect trypanosomatids

In order to verify the applicability of biochemical methods for species identification of Trypanosomatidae, 13 species of monoxenic trypanosomatids plus the heteroxenous Trypanosoma cruzi were comparatively analyzed by three different biochemical methods. Insect trypanosomatids examined were: Crithidia acanthocephali, C. fasciculata (three varieties), C. luciliae luciliae, C. luciliae thermophila, C. deanei, C. oncopelti, Herpetomonas muscarum muscarum, H. megaseliae, H. samuelpessoai, H. mariadeanei, Leptomonas seymouri, L. collosoma, L. samueli, and Blastocrithidia culicis. Also included in the survey were aposymbiotic strains of C. deanei and C. oncopelti. Methods used were: electrophoretic profiling of endonuclease-generated fragments of k-DNA, esterase isoenzymes profiling, and polyacrylamide-gel electrophoresis (SDS-PAGE) of radioiodinated cell surface proteins. Interspecific but not intraspecific differences were detected by all three methods among the 13 monoxenic species examined. Thus, it is concluded that these methods can be successfully used, in addition to classical criteria, for species identification of insect trypanosomatids.

The variable surface glycoproteins of Trypanosoma equiperdum are phosphorylated

The phosphoproteins from three Trypanosoma equiperdum variants were studied by labelling the parasites in vivo with 32P. Phosphoprotein analysis reveals the presence of a 58 000 mol. wt. phosphoprotein ( pp58 ) which is absent when live trypanosomes are pre-treated with proteinase K under conditions where only the surface coat containing the variable surface glycoprotein (VSG) is removed. Immunological and fingerprint analysis on labelled pp58 , purified from these variants by affinity chromatography on Concanavalin A-Sepharose, clearly identify this component as the VSG. Furthermore, the VSGs seem to be phosphorylated to the extent of 1 mol phosphate per mol glycoprotein. The phosphorylated region is located in the extreme C-terminal region representing approximately 10% of the total molecule. The phosphorylated residue is not an aliphatic or aromatic ester of serine, threonine, or tyrosine, nor an acyl phosphate involving an aspartyl or glutamyl residue, nor phosphohistidine. The evidence that VSGs are phosphorylated could have considerable implications for the transfer and function of these structures.

The 5S ribosomal RNA of Euglena gracilis cytoplasmic ribosomes is closely homologous to the 5S RNA of the trypanosomatid protozoa

The complete nucleotide sequence of the major species of cytoplasmic 5S ribosomal RNA of Euglena gracilis has been determined. The sequence is: 5' GGCGUACGGCCAUACUACCGGGAAUACACCUGAACCCGUUCGAUUUCAGAAGUUAAGCCUGGUCAGGCCCAGUUAGUAC UGAGGUGGGCGACCACUUGGGAACACUGGGUGCUGUACGCUUOH3'. This sequence can be fitted to the secondary structural models recently proposed for eukaryotic 5S ribosomal RNAs (1,2). Several properties of the Euglena 5S RNA reveal a close phylogenetic relationship between this organism and the protozoa. Large stretches of nucleotide sequences in predominantly single-stranded regions of the RNA are homologous to that of the trypanosomatid protozoan Crithidia fasticulata. There is less homology when compared to the RNAs of the green alga Chlorella or to the RNAs of the higher plants. The sequence AGAAC near position 40 that is common to plant 5S RNAs is CGAUU in both Euglena and Crithidia. The Euglena 5S RNA has secondary structural features at positions 79-99 similar to that of the protozoa and different from that of the plants. The conclusions drawn from comparative studies of cytochrome c structures which indicate a close phylogenetic relatedness between Euglena and the trypanosomatid protozoa are supported by the comparative data with 5S ribosomal RNAs.

Sialic acids are responsible for charge heterogeneity of the variant surface glycoprotein of Trypanosoma congolense

Intact living cells of Trypanosoma congolense can be labeled by periodate/borotritide. The procedure described introduces a radioactive label nearly exclusively into the variant surface glycoprotein (VSG). The label can be removed from the VSG by either neuraminidase treatment or by mild acid hydrolysis. Using thin-layer chromatography the labeled compounds comigrated with 5-acetamido [or 5-glycolamide]3,5-dideoxygalactooctulosonic acid and 5-acetamido [or 5-glycolamide]3,5-dideoxyarabinoheptulosonic acid. These are the compounds commonly obtained after periodate borotritide treatment of glycosidically-linked neuraminic acids. It is evident from the results that sialic acids are constituents of the carbohydrate moieties of the VSG of T. congolense. Sialic acids are responsible for the charge heterogeneity of the VSG which is observed after isoelectric focusing.

Kinetoplast DNA in Trypanosoma equinum

Identification and characterization of kDNA is described in the naturally occurring totally dyskinetoplastic species Trypanosoma equinum. Fluorescence microscopy of live cells, using the highly sensitive and specific probe DAPI (4,6-diamidino-2-phenyl-indole), showed the presence of a diversity of extranuclear fluorescent bodies scattered along the length of the organism. Transmission electron microscopic studies revealed a close similarity between the distribution of these DAPI-fluorescing particles and of dense aggregates of nonfibrillar material resembling the kDNA of dyskinetoplastic strains of other species. Variable sized remnants of kDNA, occurring singly or in clusters, were found scattered throughout the mitochondrion. Analytical cesium chloride ultracentrifugation of total cellular DNA extracts showed a kDNA banding profile at a buoyant density equal to 1.691 gm/cm3, representing approximately 11% of the total cellular DNA content. Molecular spreads of isolated kDNA revealed a population of open circular molecules ranging in contour length from 0.11-9.69 micrometer.

The kinetoplast DNA of Trypanosoma equiperdum

We have analyzed the kinetoplast DNA for Trypanosoma equiperdum (American Type Culture Collection 30019) and two dyskinetoplastic strains derived from it. The DNA networks from the kinetoplastic strain are made up of catenated mini-circles and maxi-circles, like the networks from the closely-related Trypanosoma brucei. The mini-circles of T. equiperdum lack the pronounced sequence heterogeneity of T. brucei mini-circles, as shown by the fragment distribution of restriction digests and by the predominance of well-matched duplexes in electron micrographs of renatured DNA. The electrophoretic analysis of kinetoplast DNA digested with various restriction endonucleases shows the maxi-circle of T. equiperdum to consist of circular DNA molecules of 8.4 x 10(6) daltons, without size or sequence heterogeneity or repetitious segments. A comparison of the sequence by restriction endonuclease fragmentation and hybridization shows extensive sequence homology. The size difference between both maxi-circles is due to the deletion of one continuous segment of 5.10(6) daltons. In the two dyskinetoplastic strains, we cannot detect DNA sequences that hybridize with kinetoplast DNA from T. brucei or from the kinetoplastic strain of T. equiperdum. In one of these strains, a 'low-density' DNA fraction contained a simple sequence DNA, cleaved by restriction endonuclease HindIII into fragments of 180 base-pairs and multimers of this. The relation of this DNA to kinetoplast DNA, if any, is unknown.

Absence of kinetoplast DNA in a late antigenic variant of Trypanosoma equiperdum

We have analysed by several biochemical techniques the DNA components of two antigenic variants isolated from Trypanosoma equiperdum. We did not observe any kinetoplast DNA (kDNA) structures or networks in the late antigen variant BoTat 28. Furthermore, the results of reassociation kinetics of in vitro labelled kDNA show that neither kDNA minicircle sequences nor kDNA maxicircle sequences of BoTat 1, the basic antigen type, can be detected in the total DNA of BoTat 28.

Evidence for concanavalin A binding sites on the surface coat of Trypanosoma congolense

Glycoproteins of Trypanosoma congolense have been detected on SDS-polyacrylamide gels using the Concanavalin A peroxidase technique. Using [35S]diazoniobenzenesulphonate as a marker for cell surface proteins it was possible to distinguish between internal glycoproteins and the surface coat proteins. On SDS-polyacrylamide gels Con A reacted with the surface coat proteins. Results obtained from Con A-induced agglutination of living trypanosomes indicated that sugars of the surface coat proteins were accessible to Con A. This was reinforced by the cytochemical visualization of Con A binding to the trypanosome surface. The results suggested that the surface coat protein contained alpha-linked D-mannosyl, D-glucosyl, or N-acetyl-D-glucosaminoyl residues, which are exposed exteriorly on the surface coat.

Characterization of the molecular components in kinetoplast-mitochondrial DNA of Trypanosoma equiperdum. Comparative study of the dyskinetoplastic and wild strains

The structure of the kinetoplast DNA of Trypanosoma equiperdum has been studied and compared to the structure of the circular mitochondrial DNA extracted from a dyskinetoplastic strain of T. equiperdum. In T. equiperdum wild type, the kinetoplast DNA constitutes approximately 6% of the total cellular DNA and is composed of approximately 3,000 supercoiled minicircles of 6.4 x 10(5) daltons and approximately 50 circular supercoiled molecules of 15.4 x 10(6) daltons topologically interlocked; The buoyant density in CsCl of the minicircles is 1.691 g/cm 3. The large circles have a buoyant density of 1.684 g/cm 3, are homogeneous in size and are selectively cleaved by several restriction endonucleases which do not cleave the minicircles. The cleavage sites of six different restriction endonucleases have been mapped on the large circle. The minicircles are cleaved by two other restriction endonucleases, and their cleavage sites have been mapped. The mitochondrial DNA extracted from the dyskinetoplastic strain of T. equiperdum represents 7% of the total DNA of the cell and is composed of supercoiled circles, heterogeneous in size, and topologically associated in catenated oligomers. Its buoyant density in CsCl is 1.688 g/cm 3. These molecules are not cleaved by any of the eight restriction endonucleases tested. The reassociation kinetics of in vitro labeled kDNA minicircles and large circles has been studied. The results indicate that the minicircles as well as the large circles are homogeneous in sequence and that the circular DNA of the dyskinetoplastic strain has no sequence in common with the kDNA of the wild strain.

Dyskinetoplasty in two species of trypanosomatids

Dyskinetoplastic cells from both Crithidia fasciculata and Trypanosoma equiperdum lack detectable kinetoplast DNA (kDNA) by conventional staining techniques. Two dyskinetoplastic strains of T. equiperdum, either acriflavine-induced or spontaneously occurring, show normal amounts of kDNA (p = 1.692 g/cm3) in analytical caesium chloride, ultracentrifugation. Electron and fluorescence microscopy of the dyskinetoplastic strains of T. equiperdum suggest that the kDNA network is fragmented and dispersed throughout the mitochondrion. The fragmentation and dispersion of the kDNA, rather than a reduction in the amount of kDNA, is the cause of the lack of kinetoplast staining in the dyskinetoplastic strains of T. equiperdum. Acriflavine-treated cultures of C. fasciculata show a decrease in the amount of kDNA (p = 1.703 g/cm3) corresponding to the percentage of dyskinetoplastic cells in the cultures. Electron and fluorescence microscopy of acriflavine-treated cultures of C. fasciculata show the loss of the kDNA network in cells which lack Giemsa and Feulgen staining, confirming the hypothesis that the kDNA is lost in dyskinetoplastic trypanosomatids from insects. Possible modes of acriflavine action are considered and a proposed mechanism for acriflavine action in trypanosomes from mammals is presented.