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Recently there has been growing evidence for the role of the eosinophil in the effector mechanism of immunity to reinfection with schistosomes. Mice immune to Schistosoma mansoni are no longer able to resist reinfection after treatment with anti-mouse eosinophil serum (1). In vitro studies using human serum and eosinophils (2) or rat serum and cells (3), have demonstrated antibody-mediated damage to schistosomula by eosinophils. These cells adhere to IgG-coated schistosomula by Fc receptors (3), and peroxidase, from the matrix of the eosinophil granule, is secreted onto the surface of the worm (4).Eosinophils have been shown to possess C3 receptors in addition to Fc (5, 6), and schistosomula are known to activate complement by the alternative pathway, binding C3 to their surface (7). It seemed appropriate, therefore, to investigate the adherence of rat eosinophils to schistosomula through the C3 receptor, and to monitor the effects of this interaction. Materials and MethodsParasite Cycle and Preparation of Schistosomula. A Puerto Rican strain of S. mansoni was maintained in laboratory bred Biomphalaria glabrata and outbred Parkes mice, as described elsewhere (8).Schistosomula were prepared in vitro from cercariae .by a mechanical method (9). Briefly, cercariae freshly shed from snails were concentrated by addition of peniciUin-stroptemycin, followed by chilling and spinning at 1,000 rpm for 15-30 s. 1 ml of deionized water was added to the pellet and the suspension was whirled in a Vortex mixer (Scientific Industries, Inc., Bohemia, N. Y.) for 1 rain. This effected the rupture of tails from bodies, which were afterwards separated by sedimentation in Hanks' balanced salt solution. The cercarial bodies were then incubated at 37°C in RPMI-1640 (Flow Labs. Ltd., Ayrshire, Scotland) and 20 mM N-2-hydroxyethyl-piperazine-N'-2-ethane sulfonic acid (Hepes) ~ for 3 h. The schistosomula were used on the day of preparation. Formalin-fixed schistosomula were prepared as previously described (10).5-Day schistosomula were recovered from the lungs of CBA mice after exposure to 1,000 * Supported by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (Brazil), and the WeUcome Trust. Present address:

SummaryA prominent feature of the life cycle of intracellular parasites is the profound morphological changes they undergo during development in the vertebrate and invertebrate hosts. In eukaryotic cells, most cytoplasmic proteins are degraded in proteasornes. Here, we show that the transformation in axenic medium of trypomastigotes of Trypanosoma cruzi into amastigote-like orgamsms, and the intracellular development of the parasite from amastigotes into trypomastigotes, are prevented by lactacystin, or by a peptide aldehyde that inhibits proteasome function. Clasto-lactacystin, an inactive analogue of lactacystin, and cell-permeant peptide aldehyde inhibitors of T. cruzi cysteine proteinases have no effect. We have also identified the 20S proteasomes from T. cruzi as a target oflactacystin in vivo. Our results document the essential role of proteasomes in the stage-specific transformation of a protozoan. Infection by Trypanosoma cruzi, the causative agent of Chagas' disease, is initiated by metacyclic trypomastigotes present in the feces of triatomine bugs. The trypomastigotes invade host cells and enter the cytoplasm, where they transform into amastigotes. The amastigotes replicate and, a few days later, transform back into trypomastigotes, rupture the host cells, and invade the bloodstream (1). Thus, on two occasions during its intracellular stage, T. cruzi undergoes shape and volume changes, restructures its flagellum and kinetoplast, and synthesizes new sets of surface molecules. These striking modifications are precisely timed, take place in an orderly fashion, and must involve selective degradation of cytoplasmic proteins.In eukaryotic cells, most proteins in the cytoplasm and nucleus are degraded not in lysosomes, hut within proteasomes, after they are marked for destruction by covalent attachment of ubiquitin (Ub) l molecules (2-5). In addition 1Abbreviatzons used in this paper: BSA, bovine serum albumin; CAPS, (3-[Cyclohexylarmno]-l-Propanesulfonlc acid), Ch-L, Chymotrypsln-hke; EDTA, ethylene dl-amino tetra acetic acid; E-64, trans-epoxysuccmyl-L-leucylamldo-3-methyl-butane ethyl ester; FCS, fetal calf serum; F1TC, fluoresceln lsothiocyanate; MES, (2-[N-morphohno]-ethanesulfonlc aod); MG-132, carboxybenzoxyl-leucinyl-leucinyl-leuclnal-H; PGPH, peptidylglutamyl peptlde hydrolase; T-L, Trypsin-like; Ub, ub~qultin.to their role in nonlysosomal protein turnover, proteasomes are involved in specific cellular functions, including the following: the programmed inactivation of mitotic cychns, transcription factors, and transcriptional regulators; the elimination of mutated or damaged proteins; and antigen presentation. The function of the proteasomes is also tightly regulated, and their structure may vary to match function (6-7).The experiments described below were designed to document the participation ofproteasomes in the developmental pathways of protozoan parasites. T. cruzi has an advantage as an experimental model because its trypomastigote form can be induced to change rapidly into amastigotes in axeni...

SummaryRat peritoneal eosinophils adhere to live Schistosoma mansoni schistosomula in vitro in the presence of fresh normal rat serum, or in heat-inactivated serum from rats immune to the parasite. When the eosinophils are present in sufficient numbers the worms show ultrastructural evidence of surface damage and are ultimately killed. It is believed that the appearance of focal lesions in the tegument of the schistosomulum follows the secretion of enzymes by the eosinophils onto the parasite surface. The cells have been observed within these lesions and later between the basal plasma membrane of the tegument and the underlying interstitial material. It is suggested that the cells are responsible for prising the tegument away from the body of the worm. The detached tegument shows evidence of further degradation. Adherent eosinophils which have released their secretions appear to degenerate and are eventually replaced by macrophages. Remnants of both the expended eosinophils and the disrupted tegument have been identified within the macrophages. Adherence of eosinophils through C3–C3 receptor interaction results in earlier and more severe damage to the schistosomula than when adherence occurs through Fe receptors. Rat eosinophils also adhere to C3-coated, glutaraldehyde-flxed schistosomula and C3-coated Sepharose beads. However, evidence of enzyme secretion is only obtained when the target is a schistosomulum.

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Liposomes have long been used as models for lipid membranes and for the reconstitution of a single or multiple proteins. Also, liposomes have adjuvant activity in vaccines against several protozoan or bacterial organisms. Thus, the main objective of the present study was to obtain a crude extract of detergent-solubilized proteins of Leishmania amazonensis amastigotes and reconstitute them into liposomes. Neutral and zwiterionic detergents were less efficient than an ionic detergent. In order to obtain efficient solubilization using only sodium dodecyl sulfate (SDS), the effects of detergent and protein concentration and incubation time were studied. The maximum of solubilized proteins was obtained instantaneously using a ratio of 0.5 mg/ml of protein to 0.1% (w/v) detergent at 4 degrees C. Dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylserine (DPPS) and cholesterol in a weight ratio of 5:1:4 were used for protein reconstitution into liposomes using the cosolubilization method, yielding 60% of incorporation. The incorporation of multiple parasite proteins results in a vesicular diameter of proteoliposomes of about 140 nm, presenting a final lipid weight ratio for DPPC, DPPS and cholesterol of 1:1:5, with high stability. The detergent-solubilized proteins of L. amazonensis amastigotes present in the proteoliposome, when analyzed by SDS-polyacrylamide gel electrophoresis, include a wide range of parasite-incorporated proteins. BALB/c mice inoculated with these proteoliposomes were able to produce antibodies against the proteins reconstituted in DPPC:DPPS:cholesterol liposomes and were partially resistant to infection with L. amazonensis promastigotes. These results indicate that this system can be used as a possible vaccine against L. amazonensis.

Abstract— Two enzymes that selectively hydrolyse kinins at pH 7.5 were obtained in partially purified form from the supernatant fraction of homogenates of previously frozen rabbit brain by gel filtration on Sephadex G‐100. The enzymes were detected and their activity estimated by bioassay with the isolated guinea pig ileum The products of the enzymic reactions were identified by high voltage electrophoresis at pH 3.5 and by the determination with the amino acid analyser of the amino acids released from the kinins. One enzyme, kinin‐converting enzyme, catalyses the hydrolysis of kinin‐10 (Lysbradykinin) and kinin‐11 (Met‐Lys‐bradykinin) into kinin‐9 (bradykinin). It also hydrolyses the aminoacyl‐8‐naphthylamides of methionine, lysine, arginine and leucine. The conversion of kinin‐10 to kinin‐9 was inhibited by puromycin (Ki 3.5 × 10−5 M) These properties are similar to those of brain arylamidases described in the literature. Kininase, the second enzyme, inactives kinins 9, 10 and 11 by peptide‐bond hydrolysis. Similar rates of release of arginine and phenylalanine were observed for the three kinins, suggesting that kininase acts at the carboxy‐terminus of these peptides. Our results suggest that brain contains proteases which apparently selectively metabolize polypeptide hormones that exert definite pharmacological effects on the central and peripheral nervous systems.

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