[Presence of Loxosceles similis Moenkhaus, 1898 (Araneae, Sicariidae) in Serra da Bodoquena, State of Mato Grosso do Sul, Brazil]

The venom of Loxosceles spiders causes dermonecrotic lesion and induces complement-dependent intravascular haemolysis that characterizes a severe systemic effect. In Brazil, L. gaucho, L. intermedia and L. laeta, present in the anthropic environment, have been pointed out as the most important agents of the loxoscelism. Besides these species there are others that, by predominating in the natural environment, have not been evaluated regarding human health risk, as in the case of Loxosceles similis. The development of a research project in Bodoquena Range, for ecological observation and identification of insects of medical interest, enabled the capture of Loxosceles similis specimens in the "Pitangueiras" cave and "Lago Azul" cave, in Bodoquena Range, municipality of Bonito, State of Mato Grosso do Sul, Brazil. The objectives of this study were to define the parameters for identification, environmental features of the habitat of this species, as well as an update of its geographical distribution.

Increments in serum cytokine and nitric oxide levels in mice injected with Bothrops asper and Bothrops jararaca snake venoms

Changes in serum levels of several cytokines and nitric oxide were studied in BALB/c mice injected intraperitoneally with one median lethal dose (LD(50)) of the venoms of Bothrops asper and Bothrops jararaca, two of the medically most important poisonous snakes of Latin America. Despite differences observed in the time-course of cytokine increments and in serum cytokine levels, both venoms induced prominent elevations of TNF-alpha, IL-1, IL-6, IL-10 and IFN-gamma. There was an early increase in TNF-alpha and IL-1, followed by a more pronounced increment by 18 h. IL-6 levels peaked between 4 and 6 h, and this cytokine probably modulates the secretion of TNF-alpha and IL-1 and the synthesis of acute-phase proteins. Both venoms induced an early increment in serum IL-10, whereas IFN-gamma levels reached higher values in mice injected with B. jararaca venom than in those receiving B. asper venom. Serum nitric oxide concentration increased in mice injected with both venoms rapidly after envenomation, remaining elevated for 24 h. It is concluded that a complex pattern of cytokine and nitric oxide synthesis and secretion occurs in severe experimental envenomation by B. asper and B. jararaca venoms. Furthermore, it is suggested that some of these mediators, particularly TNF-alpha, IL-1 and nitric oxide, might play a relevant role in the pathophysiology of systemic alterations induced by these venoms.

Molecular and immunochemical evidences demonstrate that endooligopeptidase A is the predominant cytosolic oligopeptidase of rabbit brain

Oligopeptidases are tissue endopeptidases that do not attack proteins and are likely to be involved in the maturation and degradation of peptide hormones and neuropeptides. The rabbit brain endooligopeptidase A and the rat testes soluble metallopeptidase (EC 3.4.24.15) are thiol-activated oligopeptidases which are able to generate enkephalin from a number of opioid peptides and to inactivate bradykinin and neurotensin by hydrolyzing the same peptide bonds. A monospecific antibody raised against the purified rabbit brain endooligopeptidase A allowed the identification of a 2. 3 kb cDNA coding for a truncated enzyme of 512 amino acids, displaying the same enzymatic features as endooligopeptidase A. In spite of all efforts, employing several strategies, the full-length cDNA could not be cloned until now. The analysis of the deduced amino acid sequence showed no similarity to the rat testes metalloendopeptidase sequence, except for the presence of the typical metalloprotease consensus sequence [HEXXH]. The antibody raised against recombinant endooligopeptidase A specifically inhibited its own activity and reduced the thiol-activated oligopeptidase activity of rabbit brain cytosol to less than 30%. Analysis of the endooligopeptidase A tissue distribution indicated that this enzyme is mainly expressed in the CNS, whereas the soluble metallo EC 3.4.24.15 is mainly expressed in peripheral tissues.

Loxosceles intermedia spider envenomation induces activation of an endogenous metalloproteinase, resulting in cleavage of glycophorins from the erythrocyte surface and facilitating complement-mediated lysis

Loxosceles is the most venomous spider in Brazil, and envenomation causes dermonecrosis and complement (C)-dependent intravascular hemolysis. The authors studied the mechanism of induction of C-induced hemolysis. Purified Loxosceles toxins rendered human erythrocytes susceptible to lysis by human C but did not have an effect on the E-bound C-regulators DAF, CR1, or CD59. However, incubation with venom toxins caused cleavage of glycophorin from the erythrocyte (E) surface, facilitating C activation and hemolysis. The results suggest that glycophorin is an important factor in the protection of E against homologous C. Cleavage of glycophorin (GP) A, GPB, and GPC occurred at sites close to the membrane but could not be accomplished using purified GPA and purified toxins, demonstrating that cleavage was not an effect of a direct proteolytic action of the Loxosceles toxins on the glycophorins. Inhibition of the cleavage of glycophorins induced by Loxosceles venom was achieved with 1,10-phenanthroline. The authors propose that the sphingomyelinase activity of the toxins induces activation of an endogenous metalloproteinase, which then cleaves glycophorins. They observed the transfer of C-dependent hemolysis to other cells, suggesting that the Loxosceles toxins can act on multiple cells. This observation can explain the extent of hemolysis observed in patients after envenomation. Identification of the mechanism of induction of susceptibility to C-mediated lysis after Loxosceles envenomation opens up the possibility of the development of an effective therapeutic strategy. (Blood. 2000;95:683-691)

Bothrops asper snake venom and its metalloproteinase BaP-1 activate the complement system. Role in leucocyte recruitment

The venom of the snake Bothrops asper, the most important poisonous snake in Central America, evokes an inflammatory response, the mechanisms of which are not well characterized. The objectives of this study were to investigate whether B. asper venom and its purified toxins--phospholipases and metalloproteinase--activate the complement system and the contribution of the effect on leucocyte recruitment. In vitro chemotaxis assays were performed using Boyden's chamber model to investigate the ability of serum incubated with venom and its purified toxins to induce neutrophil migration. The complement consumption by the venom was evaluated using an in vitro haemolytic assay. The importance of complement activation by the venom on neutrophil migration was investigated in vivo by injecting the venom into the peritoneal cavity of C5-deficient mice. Data obtained demonstrated that serum incubated with crude venom and its purified metalloproteinase BaP-1 are able to induce rat neutrophil chemotaxis, probably mediated by agent(s) derived from the complement system. This hypothesis was corroborated by the capacity of the venom to activate this system in vitro. The involvement of C5a in neutrophil chemotaxis induced by venom-activated serum was demonstrated by abolishing migration when neutrophils were pre-incubated with antirat C5a receptor antibody. The relevance of the complement system in in vivo leucocyte mobilization was further demonstrated by the drastic decrease of this response in C5-deficient mice. Pre-incubation of serum with the soluble human recombinant complement receptor type 1 (sCR 1) did not prevent the response induced by the venom, but abolished the migration evoked by metalloproteinase-activated serum. These data show the role of the complement system in bothropic envenomation and the participation of metalloproteinase in the effect. Also, they suggest that the venom may contain other component(s) which can cause direct activation of C5a.

Ontogenetic development of Loxosceles intermedia spider venom

Envenomation by Loxosceles spider has become a public health problem in the South region of Brazil, mainly due to high levels of domiciliary infestation by Loxosceles intermedia spiders. The toxic effects of L. intermedia venom are mostly associated with a 35 kDa protein (F35) which presents complement-dependent haemolytic and dermonecrotic activities. The aim of this study was to detect, through biological and immunochemical assays, the appearance of the main toxic component, F35, during the ontogenetic development of L. intermedia spiders. The toxin appeared in its fully active form in venom of third instar spiderlings; from then on its activity increased throughout development until adulthood. On the other hand, F35 was not detected in extracts of either eggs or spiderlings of the first and second instars.

Sex-linked variation of Loxosceles intermedia spider venoms

In order to investigate intraspecific differences in Loxosceles intermedia spider venom we compared some biological properties of male and female venoms. Females produced higher amounts of venom than males. Furthermore, female venom presented more potent dermonecrotic and complement-dependent activities than male venom. Interestingly, the F35 toxin, a dermonecrotic and complement-dependent haemolytic factor, was also present in greater amounts in female venom, as demonstrated by ELISA. Therefore, the higher production and increased toxicity of venom in female specimens as compared to males may contribute to the variability observed in the severity of envenoming caused by L. intermedia spiders.

Sphingomyelinases in the venom of the spider Loxosceles intermedia are responsible for both dermonecrosis and complement-dependent hemolysis

The bite of spiders of the genus Loxosceles can induce a variety of biological effects, including dermonecrosis and complement (C) dependent haemolysis. The aim of this study was to characterise the toxins in the venom responsible for the different biological effects. We have previously shown that a 35 kDa protein, named F35, purified from Loxosceles intermedia venom, incorporates into the membranes of human erythrocytes and renders them susceptible to the alternative pathway of autologous C. Here we have further purified the F35 protein which was resolved by reversed phase chromatography into three tightly contiguous peaks termed P1, P2, and P3. P1 and P2 were shown to be homogeneous by SDS-PAGE and N-terminal aminoacid analysis, while P3 consisted of two highly homologous proteins. N-terminal sequencing of all four proteins showed a high degree of homology, which was confirmed by cross-reactivity of antisera raised against the individual purified proteins. Functional characterisation of P1 and P2 indicated the presence of sphingomyelinase activity and either protein in isolation was capable of inducing all the in vivo effects seen with whole spider venom, including C-dependent haemolysis and dermonecrosis. In all assays, P2 was more active than P1, while P3 was completely inactive. These data show that different biological effects of L. intermedia venom can be assigned to the sphingomyelinase activity of two highly homologous proteins, P1 and P2. Identification of these proteins as inducers of the principal pathological effects induced by whole venom will aid studies of the mechanism of action of the venom and the development of a effective therapy.

Endotoxemic-like shock induced by Loxosceles spider venoms: pathological changes and putative cytokine mediators

The systemic symptoms, tissue lesions and release of cytokines were analysed in four isogenic mouse strains with distinct haplotypes injected with various doses of Loxosceles intermedia spider venom. The estimated LD50 were 24.5 microg for C57Bl/6, 17.6 microg for BALB/c, 6.3 microg for C3H/HeJ and 4.6 microg for A/Sn mice. Prostration, acute cachexia, hypothermia, neurological disorders and hemoglobinuria were the signals preceding death. Accumulation of eosinophilic material inside the proximal and distal renal tubules and acute tubular necrosis were the most common histopathological findings. Death was prevented by previous treatment of venom with specific antivenom serum. The protein F35 purified from the whole venom retained the ability to induce the symptoms of the whole venom. The cytokines tumor necrosis factor (TNF), interleukins IL-6 and IL-10 and the radical nitric oxide were detected in serum at different levels after venom injection. These findings indicate that the state of shock produced in mice by whole endotoxin-free L. intermedia venom or by its purified fraction, protein F35, mimics the endotoxemic shock, that susceptibility to the systemic effects of the venom varies among mice of different haplotypes and that the pattern of in vivo cytokine release resembles that of endotoxemic shock.

Incorporation of a 35-kilodalton purified protein from Loxosceles intermedia spider venom transforms human erythrocytes into activators of autologous complement alternative pathway

Cutaneous inoculation of Loxosceles spp. spider venoms produces local necrosis, occasionally accompanied by systemic intravascular clotting and hemolysis. In this work, we analyzed the role of the C system on the lysis of human erythrocytes (Eh) induced by Loxosceles venoms in vitro. Eh were treated with whole venom of Loxosceles laeta, Loxosceles gaucho, or Loxosceles intermedia, or with purified venom proteins, and incubated with C-sufficient (Cs-NHS) or C9-depleted autologous (C9d-NHS) serum. Hemolysis was determined spectrophotometrically, and deposition of C components or removal of C regulatory proteins was analyzed by FACS. Eh suspensions exposed to venoms or to a purified 35-kDa protein from L. intermedia were lysed after incubation with Cs-NHS, but not with C9d-NHS. Lysis was blocked by heating the serum at 50 degrees C or Ca2+/Mg2+ chelation by EDTA, but not by Ca2+ chelation with EGTA. Deposition of C1, C2, C3, C4, C5, and factor B on the venom-treated Eh occurred during activation of autologous C. Regulatory proteins decay-accelerating factor (DAF) and CD59 were not altered significantly. Conversion of C-resistant Eh into C-susceptible Eh by the L. intermedia venom was accompanied by incorporation of a 35-kDa venom protein onto the cell surface. Thirty-five-kilodalton-related proteins were detected in the two other Loxosceles venoms by ELISA, using rabbit antiserum against the L. intermedia 35-kDa protein. These data suggest that the C system mediates the lysis of human erythrocytes and, by extension, of other cell types able to incorporate the lytic factor of Loxosceles venoms on their cell surfaces.

Incorporation of a 35-kilodalton purified protein from Loxosceles intermedia spider venom transforms human erythrocytes into activators of autologous complement alternative pathway

Cutaneous inoculation of Loxosceles spp. spider venoms produces local necrosis, occasionally accompanied by systemic intravascular clotting and hemolysis. In this work, we analyzed the role of the C system on the lysis of human erythrocytes (Eh) induced by Loxosceles venoms in vitro. Eh were treated with whole venom of Loxosceles laeta, Loxosceles gaucho, or Loxosceles intermedia, or with purified venom proteins, and incubated with C-sufficient (Cs-NHS) or C9-depleted autologous (C9d-NHS) serum. Hemolysis was determined spectrophotometrically, and deposition of C components or removal of C regulatory proteins was analyzed by FACS. Eh suspensions exposed to venoms or to a purified 35-kDa protein from L. intermedia were lysed after incubation with Cs-NHS, but not with C9d-NHS. Lysis was blocked by heating the serum at 50 degrees C or Ca2+/Mg2+ chelation by EDTA, but not by Ca2+ chelation with EGTA. Deposition of C1, C2, C3, C4, C5, and factor B on the venom-treated Eh occurred during activation of autologous C. Regulatory proteins decay-accelerating factor (DAF) and CD59 were not altered significantly. Conversion of C-resistant Eh into C-susceptible Eh by the L. intermedia venom was accompanied by incorporation of a 35-kDa venom protein onto the cell surface. Thirty-five-kilodalton-related proteins were detected in the two other Loxosceles venoms by ELISA, using rabbit antiserum against the L. intermedia 35-kDa protein. These data suggest that the C system mediates the lysis of human erythrocytes and, by extension, of other cell types able to incorporate the lytic factor of Loxosceles venoms on their cell surfaces.

Detection of Trypanosoma-decay accelerating factor antibodies in mice and humans infected with Trypanosoma cruzi

Highly purified Trypanosoma-decay accelerating factor (T-DAF), a 87-93-kD glycoprotein present on the surface of metacyclic and trypomastigote forms of Trypanosoma cruzi, was used as antigen to evaluate the presence of specific serum antibodies in experimentally infected mice and patients with Chagas' disease by enzyme-linked immunosorbent assay (ELISA). Mouse T-DAF antibodies were first recorded on day 7 postinfection, reached maximal concentration on day 30, and maintained at positive titers thereafter. High immunogenicity was clearly demonstrated by the detection of T-DAF antibodies in 96% of the sera collected from chagasic patients in either the acute or the chronic phase of disease. Control sera from normal individuals and from patients with leishmaniasis or other chronic infections did not give positive results. Serologic evaluation using T-DAF as antigen did not discriminate between patients with the cardiac and the digestive forms of the disease. The performance of the T-DAF ELISA was compared with that of conventional screening tests for Chagas' disease (indirect immunofluorescence and hemagglutination). The T-DAF ELISA test showed a sensitivity of 96%, a specificity of 100%, an efficiency of 99%, a positive predicted value of 100%, a negative predicted value of 98%, and a kappa index of 0.96, thus indicating that it can be successfully used for the serodiagnosis of T. cruzi infection in humans.

Pro-inflammatory activities in elapid snake venoms

1. Snake venoms from the genera Micrurus (M. ibiboboca and M. spixii) and Naja (N. naja, N. melanoleuca and N. nigricollis) were analysed, using biological and immunochemical methods, to detect pro-inflammatory activities, cobra venom factor (COF), proteolytic enzymes, thrombin-like substances, haemorrhagic and oedema-producing substances. 2. The venoms of the five snake species activate the complement system (C) in normal human serum (NHS) in a dose-related fashion, at concentrations ranging from 5 micrograms to 200 micrograms ml-1 serum. Electrophoretic conversion of C3 was observed with all venoms in NHS containing normal concentrations of Ca2+ and Mg2+, but only by venoms from N. naja and N. melanoleuca when Ca2+ was chelated by adding Mg(2+)-EGTA. 3. Purified human C3 was electrophoretically converted, in the absence of other C components, by the venoms from N. naja, N. nigricollis and M. ibiboboca. However, only the venoms from N. naja and N. melanoleuca contained a 144 kDa protein revealed in Western blot with sera against COF or human C3. 4. All venoms, at minimum concentrations of 30 ng ml-1, were capable of lysing sheep red blood cells, also in a dose-related fashion, when incubated with these cells in presence of egg yolk as a source of lecithin. Although the venoms from M. spixii and N. nigricollis showed detectable thrombin-like activity, these and the other venoms were free of proteolytic activity when fibrin, gelatin and casein, were used as substrates. 5. When tested on mice skin, all five venoms were capable of inducing an increase in vascular permeability and oedema, but were devoid of haemorrhagic producing substances (haemorrhagins). 6. These data provide evidence indicating that Elapidae venoms contain various pro-inflammatory factors which may be important in the spreading of neurotoxins throughout the tissues of the prey or human victim.

A partial cDNA clone of trypomastigote decay-accelerating factor (T-DAF), a developmentally regulated complement inhibitor of Trypanosoma cruzi, has genetic and functional similarities to the human complement inhibitor DAF

Resistance to complement-mediated lysis in Trypanosoma cruzi is due to the expression of complement-regulatory factors by the virulent developmental forms of this protozoan parasite. An 87- to 93-kDa molecule, which we have termed T-DAF (trypomastigote decay-accelerating factor), is present on the surface of the parasite and inhibits complement activation in a manner functionally similar to the mammalian complement regulatory component, decay-accelerating factor. In this report, we characterized monospecific polyclonal and monoclonal antibodies which were obtained from mice and rabbits immunized with fast protein liquid chromatography-purified T-DAF. These polyclonal antibodies were shown to inhibit T-DAF activity and were capable of inducing lysis of the parasites. Both the polyclonal and monoclonal antibodies were used to screen a cDNA expression library prepared from T. cruzi trypomastigote mRNA. From this library, we obtained a partial lambda gt11 cDNA clone which showed genetic and functional similarity to the human C3 convertase inhibitor DAF (A. Nicholson-Weller, J. Burge, D. T. Fearon, P. F. Weller, and K. F. Austen, J. Immunol. 129:184-189, 1982).

Biotinylation a fast and reproducible method for labelling Trypanosoma cruzi cell surface proteins

In this study we describe a simple and rapid method that uses sulfo-N-hydroxy-succinimidobiotin (sulfo-NHS-biotin) to label Trypanosoma cruzi surface proteins stably without significant loss of biological function. Efficient labelling can be obtained with as little as a 5 minute incubation of parasites in an appropriate concentration of sulfo-NHS-biotin at 4 degrees C. After labelling under these conditions, biotinylated parasites exhibited levels of motility, viability, and in vivo infectivity comparable to those seen with unlabelled control parasites. Moreover, the biological activity of T-DAF, a complement regulatory protein found on the parasite surface, was unaffected when biotinylated under these conditions. Biotinylated surface proteins can be easily detected in a variety of non-radioactive assays employing conjugated streptavidin as a developer. Compared to alternative techniques of surface labelling described in the literature, this method offers better preservation of biological function as well as greater ease of use and safety.

Secretion of a neuropeptide-metabolizing enzyme similar to endopeptidase 22.19 by glioma C6 cells

An endopeptidase capable of metabolizing a number of neuropeptides and generating [Met5] and [Leu5] enkephalin from enkephalin-containing peptides is secreted by glioma C6 cells. This neutral endopeptidase that is likely to be a thiol protease, has a Mr of 71KDa and is effective only towards oligopeptides. Its specificity towards neuropeptides is identical to that of soluble endopeptidase 22.19. Moreover, when a partially purified preparation of enkephalin-generating enzyme secreted by glioma C6 cells was submitted to immunoblotting, an antiserum against purified brain endopeptidase 22.19 recognized a single band at Mr of 71 KDa. These data suggest that the soluble endopeptidase 22.19 may be secreted by glioma C6 cells thus allowing its participation in the biotransformation of opioid peptides in the CNS.

Susceptibility of different strains of mice to South American rattlesnake (Crotalus durissus terrificus) venom: correlation between lethal effect and creatine kinase release

In the present work we report that susceptibility to Crotalus durissus terrificus venom: varies according to the strain of inbred mouse used. The s.c. LD50 for Balb/c and C57BI/6 mice were 193 micrograms/kg and 171 micrograms/kg, whereas for A/J and DBA/J they were 78 micrograms/kg and 74 micrograms/kg, respectively. In addition, a direct correlation between susceptibility to C. d. terrificus venom and creatine kinase serum levels (CK) was observed.

Trypanosoma cruzi: antibody-dependent killing of bloodstream trypomastigotes by mouse bone marrow-derived mast cells and by mastocytoma cells

Two different populations of mast cells, that is, mastocytoma cells (P815) that were maintained either in vitro or in vivo, and mast cells obtained by differentiation of bone marrow precursor cells (MMC) in conditioned medium, were used as effector cells in antibody-dependent cytotoxic reactions (ADCC) against bloodstream trypomastigotes (BT) of Trypanosoma cruzi. The assay consisted of incubating effector cells with parasites that had been previously sensitized with immune mouse sera, immune IgG isotypes, or with medium. After the incubation period, the number of live BT was assessed. It was found that (a) cytotoxicity is antibody dependent; (b) the main isotypes involved are IgG1, IgG2a, and IgG2b; (c) both types of mast cells (mastocytoma and MMC cells) are equally efficient in killing BT; (d) mastocytoma cells degranulated by pretreatment with compound 48/80 are still able to effect ADCC; (e) on optical microscope examination, large numbers of parasites were often seen attached to the cells, but only when anti-T. cruzi antibodies were present; and (f) on electron microscope examination, no integral or ruptured parasites were seen inside the cells. We conclude that both T dependent and T independent mast cells are capable of mediating ADCC by a mechanism that is probably not dependent on granule extrusion.