An amphipathic sulphated glycoconjugate of Leishmania: characterization with monoclonal antibodies

A major glycoconjugate of Leishmania tropica major identified by two monoclonal antibodies was shown to be an externally oriented, amphipathic membrane antigen shed into the culture medium in which the parasites grow. This molecule could be labelled metabolically with [3H]glucose, [3H]galactose, [32P]phosphate and [35S]sulphate. It migrated as a polydisperse band upon electrophoresis in SDS-polyacrylamide gels, spanning the region of the gel corresponding to an apparent mol. wt. of 20 000-67 000 daltons. An apparently identical family of molecules could be labelled on the surface of living promastigotes using galactose oxidase and [3H]-sodium borohydride. This molecule was shown to be released into the supernatant over a period of several hours. Detection of the 3H- or 35S-labelled molecule required several days exposure of autoradiographs, but a novel blotting technique using nitrocellulose coated with monoclonal antibody allowed rapid detection of the molecule in charge shift electrophoresis, Western blotting and dot blotting. The electrophoretic mobility of the glycoconjugate in agarose relative to its mobility in Triton X-100 was increased in the presence of deoxycholate, and decreased in the presence of cetyl trimethyl-ammonium bromide, indicating amphipathic properties consistent with insertion into the lipid bilayer of the membrane. Using the dot-blotting technique the glycoconjugate was detected in all virulent and avirulent clones of LRC-L137 and in two additional isolates of L. tropica major (LRC-L287 and LRC-L251), but not in L. donovani or L. mexicana, consistent with the previously described specificity of the antibodies. However, the general approaches used in this paper showed that L. donovani (LRC-L52) and L. mexicana (LRC-L94) synthesize a similar, but antigenically distinct glycoconjugate.

Surface reaction of Leishmania. III. Ulex europaeus II lectin affinity for excreted factor (EF) serotype A strains

Eukaryotic parasites, including species of Leishmania, acquire or synthesize carbohydrate moieties similar to human blood group antigens. Leishmanial strains separate into three serotypes: A, B and AB. All strains containing the A component are agglutinated by Ulex europaeus lectin. Inhibition by haptene sugar suggests that a Ulex II-like receptor is involved. Organic solvents, but not protease treatment, remove its reactivity, suggesting that the receptor is a glycolipid.

Growth inhibition of Leishmania tropica amastigotes in vitro by rifampicin combined with amphotericin B

Rifampicin and Amphotericin B (AMB) were studied separately and in combination to determine their effect in vitro on intracellular Leishmania tropica amastigotes. On the fourth day of treatment, rifampicin at 200 micrograms ml-1 or AMB at 0.15 microgram ml-1 reduced the parasites' survival index (PSI) to 10% compared with the untreated control. In combination, there was a significant synergistic effect at several concentrations. The synergistic therapeutic effects were not accompanied by toxicity to the host cells, although each drug alone caused cellular degeneration in the ultrastructure of the parasites with the formation of large autophagic-like vacuoles, while the combination increased the percentage of degenerate cells.

The cellular and humoral immune response in subjects vaccinated against cutaneous leishmaniasis using Leishmania tropica major promastigotes

In vitro lymphocyte transformation was studied in 24 subjects 12 months after vaccination with live Leishmania tropica major vaccine, in 10 normal control subjects and in three controls residing in an endemic area. The vaccines had lesions in various stages of clinical development. Lymphocytes from all the subjects were studied for their response to stimulation with L. tropical major promastigotes. Lymphocytes of vaccinated subjects responded to low concentrations of antigen whereas the lymphocyte response of the controls tended to be depressed by the same concentration of the antigen. Serum from each subject was subjected to a study of the humoral antibody titre against L. tropica major and L. donovani using indirect immunofluorescence. A humoral response to L. donovani was present in a majority of vaccinees who had developed a positive lesion whereas no such responses was present in any of the controls. The data suggest that high humoral responses were accompanied by relatively low cell-mediated responses and vice versa. No significant humoral response to L. tropica major could be demonstrated in any of the subjects. A combination of both the cell-mediated and humoral mechanisms may participate in the immune response although their usefulness in the assessment of the protectivity of leishmania vaccines has not been established.

Monoclonal antibodies for serotyping Leishmania strains

Mouse monoclonal antibodies raised against Leishmania tropica major were found to precipitate with the excreted factor produced by this and other leishmanial species. We suggest that a classification system for Leishmania, based on selective precipitation reactions between monoclonal antibodies and the excreted factor, would remove many ambiguities that currently exist.

Leishmania tropica and Leishmania donovani: solid phase radioimmunoassay using leishmanial excreted factor

A radioimmunoassay for the quantitative determination of anti-leishmanial excreted factor (EF) antibody in rabbit sera was developed. The assay, using Leishmania tropica and Leishmania donovani promastigotes EF, purified by either extraction with phenol followed by fractionation on a Sephadex G-100 column or by the dissociation of EF antibody complexes, was shown to be sensitive and reproducible. Using monospecific anti-EF antibodies, levels of as low as 0.06-0.12 micrograms/ml of anti-EF IgG could be detected. The specificity of the assay was assessed by inhibition with homologous and heterologous EF. Only minor cross-reactivity with heterologous EF was observed, and as little as 2.5 micrograms/ml of EF could be detected. Sera from kala-azar patients showed only 1.8-3.1 times more anti-EF activity, as compared with uninfected controls. No specificity was observed with sera from kala-azar patients with regard to the type of EF used. Almost the same activity was obtained with both EF from L. tropica and L. donovani. No anti-EF antibodies were detected in sera from patients with cutaneous leishmaniasis.

Action of leishmanial excreted factor (EF) on human lymphocyte blast transformation

The effect of Leishmania tropica major excreted factor (EF) on human immune and normal mononuclear peripheral blood cells has been studied. The response of lymphocytes to stimulation either specifically with leishmanial antigens or non-specifically with phytohemagglutinin (PHA) in the presence of EF was tested by the uptake of 3 [H]thymidine. The results showed that EF inhibits the response of cells from immune donors to leishmanial antigens and from normal donors to PHA or PPD. Adherent and non-adherent cells were separated and the effect of EF on both populations was analysed. The results showed that EF inhibited blast transformation if both EF and antigen were presented to each of the separate populations. The inhibition of the adherent cells (mainly monocytes) was more marked than the inhibition of the non-adherent population (mainly lymphocytes).

Chemotherapeutic activity of rifampicin on leishmanial amastigotes and promastigotes in vitro

Rifampicin reduced the in vitro growth of Leishmania tropica major promastigotes and amastigotes: 100 micrograms/ml reducing the growth of amastigotes on Day 2 and 250 to 500 micrograms/ml reducing the growth of promastigotes on Day 1. A distinct effect of solvents was noted. Methanol, dimethylsulfoxide and Tween 80 appeared to increase drug effectiveness. Pretreatment of L. tropica major promastigotes with 200 micrograms/ml rifampicin for 3 days had no effect on either macrophage engulfment of the treated promastigotes or their transformation into amastigotes. Intracellular amastigotes treated for only 3 days recovered and 8-day treatment with 100 micrograms/ml rifampicin was insufficient to totally eliminate the amastigotes. The promastigotes of different strains of Leishmania showed different sensitivities to rifampicin, L. aethiopica being more sensitive than L. donovani, L. tropica minor and L. tropica major.

Leishmanial excreted factors (EFs): purification by affinity chromatography

Leishmania species grown in culture excrete a polyanionic, carbohydrate-rich factor (EF) which binds to antibodies produced in rabbits against the parent Leishmania species. EF, previously purified by physical and chemical methods, was purified by affinity chromatography on a Ricinus lectin column. The purified samples were characterised and analysed. The results show a notable proportion of galactose in EF and clarify the reasons for its polyanionic properties. Heterogenicity of EF is demonstrated and discussed.

Frozen stored Leishmania tropica vaccine: the effects of dose, route of administration and storage on the evolution of the clinical lesion. Two field trials in the Israel Defense Forces

The first field trial of frozen vaccine against cutaneous leishmaniasis yielded a 100% take rate and a high ulceration rate at a dose of four million units. Two further trials were designed to investigate differences in response rates on the basis of duration of storage, sex of vaccinee, vaccination dose and method of administration. 257 soliders (151 males and 106 females) were inoculated in 1978 with an isolate of Leishmania tropica major that had been stored at the temperature of liquid nitrogen for 11 months before use. Those inoculated with an intradermal jet injector and those receiving half a million units by conventional injection yielded very low take rates. For those receiving two million and one million units, no difference in response was demonstrated between males and females or between doses. The over-all take rate for these groups after six months of follow-up was 71.6% with an ulceration rate of only 23.7%. In a subsequent trial in 1979, 131 men were inoculated with one of two frozen isolates of L. tropica major that had been stored for 11 and 18 months, respectively, at doses of either two million or four million units. The take rate after 12 months of follow-up was 91% and 93% for the four and two million units dose, respectively. The corresponding ulceration rates were 39.5% and 25%. The lesions produced by the higher dose developed more rapidly than those produced by the lower dose. The ability of the parasites to produce lesions rapidly with high ulceration rates appears to decline during prolonged storage, even in the frozen state.

Binding of Leishmania promastigotes to macrophages

Leishmania tropica promastigotes are easily attached to and engulfed by C3H peritoneal macrophages in vitro at 37 degrees C. Different sugars at 0.3-0.5 M inhibited in vitro the attachment of L. tropica promastigotes to C3H peritoneal macrophages with lactose (Gal-beta [1 leads to 4]Glc) being the most efficient. Inhibition of attachment is also affected by pre-treatment of promastigotes with galactose oxidase. Oligosaccharides extending from promastigote and amastigote cell surfaces contain an important proportion of non-reducing galactose as does the carbohydrate-rich factor (EF) excreted by promastigotes of L. tropica and L. donovani. This study suggests that Leishmania, an obligatory intracellular parasite, uses as a means of entering the host cell a cellular mechanism similar to that used in the removal of damaged cells from blood circulation. This mechanism is assumed to take advantage of the exposed sugars, particularly the exposed non-reducing galactose, on the parasite surface during the stage of attachment. Once the parasite is inside the cell, the EF it produces might have a protective function, being inhibitory to some of the host cell lysosomal enzymes.

Effect of leishmanial excreted factor on the activities of adenylate cyclase from hamster liver and Leishmania tropica

The carbohydrate segment of the excreted factor of culture cells from L. tropica and L. donovani was shown to interact with the adenylate cyclase from hamster liver. At a concentration of 1 mg/ml the excreted factor inhibited the stimulated activity of the mammalian enzyme by about 50%, independent of the activation by glucagon, 5'-guanylylimidodiphosphate and forskolin, respectively. In contrast to the adenylate cyclase system from hamster liver the enzyme from L. tropica-culture cells was not stimulated by addition of glucagon, 5'-guanylylimidodiphosphate and forskolin. In addition, the activity of the adenylate cyclase from L. tropica was not affected by addition of its endogenous excreted factor.

Identification of galactose as the immunodominant sugar of leishmanial excreted factor and subsequent labeling with galactose oxidase and sodium boro[3H]hydride

Inhibition by low-molecular-weight sugars of precipitin line formation between a polysaccharide (EF) excreted by Leishmania tropica subsp. major, Leishmania enriettii, and rabbit antileishmanial antibodies on double gel diffusion plates revealed that galactose residues, possibly as components of lactosyl groups, were the critical immunodominant sugars mediating antibody recognition of EF. The galactose residues of the EF of L. tropica subsp. major were specifically labeled with tritium via galactose oxidase and sodium boro[3H]hydride. The radioactive EF had an apparent molecular weight of about 85,000 on sodium dodecyl sulfate-polyacrylamide gels and was precipitated by antileishmanial antibodies as well as Ricinus communis lectins I and II (galactose specific). Lectins specific for glucose-mannose residues, fucose, N-acetylglucosamine, and N-acetylgalactosamine did not precipitate the labeled EF. Treatment of [3H]EF with proteolytic (trypsin, papain, protease) or glycosidic (alpha-amylase, beta-galactosidase) enzymes had no effect on either the electrophoretic pattern of the material or on its recognition by antileishmanial antibodies or R. communis lectin. This resistance to enzyme activity suggests that EF may be a useful marker for the presence of the parasite in vivo if it can be detected in minute quantities.

Rifampicin treatment of cutaneous leishmaniasis

In a small-scale preliminary trial of oral rifampicin treatment was considered successful in six out of eight cutaneous leishmaniasis patients and probably effective in a seventh. The in vitro effect of rifampicin on leishmania organisms concerns inhibition of mitochondrial function or replication. The need for protozoological control in the assessment of treatment is stressed.

Cellular changes in bone marrow of malaria-infected mice. III. Chemotaxis of granulocytes

The number of bone marrow cells and their chemotactic activity was studied during malaria infection. Two days after infection of Balb/c mice with Plasmodium berghei, an increase in granulocyte number was observed in the blood. A modified Boyden chamber chemotaxis assay was employed to investigate the mechanism of granulocyte accumulation in the blood. Bone marrow cells from normal mice, from mice during a primary lethal infection and from immune mice after challenge were compared. The complement factor C5a showed chemotactic activity for bone marrow cells; a significant decrease of chemotaxis was only observed after 6 days of primary infection. Extracts of spleen, liver and infected erythrocytes lacked chemotactic activity, or caused inhibition of cell migration. Serum from mice with a 2-day primary infection contained chemotactic activity. The active component was heat labile, protease sensitive and had an estimated molecular weight of 250,000.

Polyamines and the growth of leishmanial parasites

The relation between the grown of leishmanial parasites and polyamine biosynthesis was studied. Polyamines, mainly putrescine and spermidine, accumulated in macrophages infected with Leishmania tropica major promastigotes grown in vitro. Similar results were obtained, when tissues of BALB/C mice infected with L. tropica major were examined. A consistent increase in cellular putrescine and spermidine levels was observed in infected skin and spleen. With the accumulation of putrescine, a concomitant increase in ornithine decarboxylase activity was detected in growing leishmanial promastigotes and in macrophages supporting the growth of leishmanial amastigotes. An increase in the activity of ornithine decarboxylase was also observed in Leishmania-infected skin and spleen from BALB/C mice.

Coagglutination and indirect hemagglutination in the detection of an excreted immunologically active substance from Leishmania

The methods of coagglutination and indirect hemagglutination were used to detect the production of the immunologically active excreted factor (EF) of Leishmania. Staphylococci, rich in protein A and sensitized with specific anti-Leishmania antibodies, coagglutinated with supernatant fractions of cultures, thus enabling continuous monitoring of the excretion of EF by multiplying parasites. Papain-treated human red blood cells, sensitized with crude or purified EF, also agglutinated with the coagglutination reagent. The sensitized papain-treated red blood cells may be employed in indirect hemagglutination to detect specific antibodies to Leishmania in rabbit and human sera. As the EF is specific for each Leishmania serotype group, coagglutination and indirect hemagglutination offer the possibility of rapid, easy, sensitive and specific diagnostic tools in the determinations of both antigen and antibody in specimens from suspected cases of leishmaniasis.

Adoptive transfer of immunity to Plasmodium berghei after busulfan and cyclophosphamide treatment of recipient mice

Balb/c mice injected with P. berghei die about 21 days after infection. Successful cell transfer in mice was made possible by the pretreatment of the recipient with a combination of busulfan and cyclophosphamide. Cell counts showed that drug-treated mice contain 20 times less bone marrow cells than normal mice, and when injected with P. berghei die significantly later than normal controls. The animals were injected with normal (NBM) and immune bone marrow and normal (NSp) and immune spleen (ISp). The results obtained showed that ISp lengthens significantly the average survival time, producing cure of 50% of the recipients. Transfer of NSp and NBM also lengthens the average survival time.

Production and secretion of Leishmania braziliensis proteins

The kinetics of secretion of proteins by Leishmania braziliensis was followed by incorporation of [3H]leucine into macromolecules produced by the cells which are released into the growth medium. About 10% of the total protein synthesized by actively growing cells is secreted. Cycloheximide (100 microgram/ml) and puromycin (0.5 mM) inhibited the incorporation of labelled leucine by 85 and 99%, respectively. The secreted proteins do not seem to result from cell lysis since, first, the kinetics of production are linear and, secondly, less than 1% of thymidine or uridine incorporated by the cells is found in the medium. Cells grown with [3H]leucine and then transferred to fresh medium show two phases of secretion. During the first six hours, it is slow and reaches a plateau. The release increases about ten-fold during the next six hours. An analysis of the secreted material showed that following precipitation with methanol and sodium acetate, three isotopically labelled peaks were eluted from Sephadex G-120-150. The first of these, containing 50% of the radioactivity, did not react with anti-leishmanial serum, while the last two did. Since the last two fractions could be labelled with [3H]glucosamine as well as [3H]leucine it is suggested that they are glycoprotein in nature and are similar to the products released by other species of Leishmania.

Leishmanial excreted factor: protein-bound and free forms from promastigote cultures of Leishmania tropica and Leishmania donovani

Leishmania spp. growing in culture produce an immunologically active substance called excreted factor (EF), which precipitates antibodies raised against intact cells and has been implicated as the conditioning agent for parasite infection of host macrophages. An improved method for isolation of the material is described, based on Sephadex column chromatography of growth medium which had been boiled at pH 5.0. This procedure allows the detection of differences among the EF molecules of different species, and it overcomes previous shortcomings through the monitoring of immunological activity throughout. Analysis of the products of this procedure revealed that EFs from Leishmania tropica and Leishmania donovani share a common carrier protein, identified as rabbit serum albumin, and are chemically quite similar. Growth medium from L. tropica boiled at acidic pH contains primarily an EF-albumin complex of 75,000 molecular weight. Treated growth medium from L. donovani, on the other hand, contains both the albumin complex and a smaller molecule (less than 27,000 molecular weight) that is not associated with rabbit protein. This material accounts for nearly 20% of the EF of one L. donovani strain, but constitutes only a minute fraction of L. tropica EF. Treatment of the EF-albumin complex with trichloroacetic acid separates the molecule into two major subunits, one having a molecular weight of about 61,000 (without anti-Leishmania activity) and the other having a molecular weight of about 18,000 (with no anti-rabbit activity). The protein-free EF of L. tropica differs from that released by trichloroacetic acid extraction in that it is capable of precipitating antisera of nonhomologous serotypes, whereas the albumin complex and the trichloroacetic acid-treated EF fragment are not. EFs from both species display pH-dependent affinity for certain lectins.

Development of a storable Leishmania tropica vaccine: field testing with frozen promastigotes

The development of a frozen vaccine against cutaneous leishmaniasis offers the possibility of controlling the quality, efficiency and sterility of the promastigotes used for inoculation. Thirty-nine soldiers in a settlement in a hyperendemic area were inoculated with a fresh isolate of Leishmania tropica that was stored at the temperature of liquid nitrogen. Thirty of the soldiers were injected by conventional syringe while the rest were inoculated by an intradermal jet injector. The infective material was transported either in ice or at liquid nitrogen temperature. All the subjects developed lesions at the site of inoculation, without unwarranted reactions. One month after inoculation 31 subjects were examined by a physician. All the reactions were positive--12 ulcers and 19 nodules. After four months, all 39 soldiers were examined: 25 (64%) had ulcers; eight (21%) had nodules; and six (15%) were without visible reaction. The different methods of transporting the vaccine, as well as the different responses of men and women, are discussed.

Plasmodium berghei adoptive transfer and immunosuppression of immunity in allogenic neonates

Outbred female rats were hyperimmunized with Plasmodium berghei and mated to produce progeny. Spleen cells from the immunized rats and from normal control mothers were adoptively transferred to their 48 hr old neonates. Some neonates from immune mothers were fostered to normal mothers and vice versa. Weanling rats were challenged 35 days after birth with Plasmodium berghei; immune and normal litters which had not received cells were also challenged at the same time. Rats which had received immune spleen cells from their mothers but were fostered on to non-immune mothers showed significantly lower parasitaemias and higher fluorescent antibody titres than any other combination of cell transfer and maternal milk. GVH reaction was minimal. These results suggest that the immune response to P. berghei was suppressed in the presence of passively transferred maternal antibody.

Observations on immunization against cutaneous leishmaniasis in Israel

Trials of immunization against Leishmania tropica were initiated in the Israel Defense Forces in 1968. The rate of takes has declined gradually over the years. In 1975, 425 soldiers were inoculated with the same strain of L. tropica as that used since 1968; they were examined at three- and six-month intervals after the inoculation, with 291 soldiers undergoing at least one follow-up examination. Only 13.7% developed lesions at the inoculation site, usually between three and six months after the inoculation. Leishmanin tests were performed in 220 soldiers and there were positive reactions in 19.5%. There was a fair correlation between the development of clinical lesions and positive leishmanin tests. A positive leishmanin test, or a typical lesion, or both, was seen in 21.3% of the inoculated soldiers. L. tropica tends to lose its virulence after prolonged storage and multiple passages. A new strain isolated a few months before this trial was used to inoculate 50 soldiers, 31 of whom were followed up. All 31 developed typical lesions at the site of inoculation, most of them within two to four weeks following the inoculation.

Promotion of leishmanial infections in non-permissive host macrophages by conditioned medium

Leishmania enriettii grows well in guinea pig macrophages in culture but fails to do so in mouse macrophages. Dialyzed and concentrated conditioned medium from L. enriettii cultures promoted the infection in the mouse macrophages at 37 degrees C and at 32 degrees C. Similarly processed medium on which L. tropica had been cultured did not cause the same effect. Immune precipitation of the conditioned medium by anti-Leishmania serum cancelled out the effect. Infections of guinea pig macrophages by L. tropica were also enhanced by the homologous medium, but we were unable to quantitate the effect.