Gold(I) ion and the phosphine ligand are necessary for the anti-Toxoplasma gondii activity of auranofin.

Auranofin, an FDA-approved drug for rheumatoid arthritis, has emerged as a promising antiparasitic medication in recent years. The gold(I) ion in auranofin is postulated to be responsible for its antiparasitic activity. Notably, aurothiomalate and aurothioglucose also contain gold(I), and, like auranofin, they were previously used to treat rheumatoid arthritis. Whether they have antiparasitic activity remains to be elucidated. Herein, we demonstrated that auranofin and similar derivatives, but not aurothiomalate and aurothioglucose, inhibited the growth of Toxoplasma gondii in vitro. We found that auranofin affected the T. gondii biological cycle (lytic cycle) by inhibiting T. gondii's invasion and triggering its egress from the host cell. However, auranofin could not prevent parasite replication once T. gondii resided within the host. Auranofin treatment induced apoptosis in T. gondii parasites, as demonstrated by its reduced size and elevated phosphatidylserine externalization (PS). Notably, the gold from auranofin enters the cytoplasm of T. gondii, as demonstrated by scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDS) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS).IMPORTANCEToxoplasmosis, caused by Toxoplasma gondii, is a devastating disease affecting the brain and the eyes, frequently affecting immunocompromised individuals. Approximately 60 million people in the United States are already infected with T. gondii, representing a population at-risk of developing toxoplasmosis. Recent advances in treating cancer, autoimmune diseases, and organ transplants have contributed to this at-risk population's exponential growth. Paradoxically, treatments for toxoplasmosis have remained the same for more than 60 years, relying on medications well-known for their bone marrow toxicity and allergic reactions. Discovering new therapies is a priority, and repurposing FDA-approved drugs is an alternative approach to speed up drug discovery. Herein, we report the effect of auranofin, an FDA-approved drug, on the biological cycle of T. gondii and how both the phosphine ligand and the gold molecule determine the anti-parasitic activity of auranofin and other gold compounds. Our studies would contribute to the pipeline of candidate anti-T. gondii agents.

Predicting acquisition of carbapenem-resistant Gram-negative pathogens in intensive care units.

BACKGROUND: Infections by multidrug-resistant Gram-negative (MDRGN) bacteria are among the greatest contemporary health concerns, especially in intensive care units (ICUs), and may be associated with increased hospitalization time, morbidity, costs, and mortality. AIM: The study aimed to predict carbapenem-resistant MDRGN acquisition in ICUs, to determine its risk factors, and to assess the impact of this acquisition on mortality rate. METHODS: A matched case-control study was performed in patients admitted to the ICU at a large Brazilian hospital over a five-year period. Cases were defined as patients who acquired carbapenem-resistant MDRGN bacteria during hospitalization. Controls were defined as patients who had no detection of carbapenem-resistant MDRGN bacteria. Cases were matched to controls according to the admission period. Risk factors were identified by multiple logistic regression using a stepwise selection method. FINDINGS: In total, 343 cases and 1029 controls were analysed. The 30-day mortality rate for subjects with ICU-associated carbapenem-resistant MDRGN was 37.6%. Five variables were identified as statistically significant and more relevant for the acquisition of multidrug-resistant strains: increased Simplified Acute Physiology Score 3, patients with severe chronic obstructive pulmonary disease and exposure to haemodialysis catheter, central venous catheter, or mechanical ventilation. Models developed displayed good results with an accuracy of ∼90%. Patients who acquired MDRGN were 2.72 times more likely to die than non-MDRGN acquisition patients. CONCLUSION: Finding risk factors and developing predictive models may benefit patients through early detection and by controlling the spread of MDR. The presence of mechanical ventilation and central venous catheter were the main risk factors demonstrated, and their use requires special attention.

Characterization of the gene encoding component C3 of the complement system from the spider Loxosceles laeta venom glands: Phylogenetic implications.

A transcriptome analysis of the venom glands of the spider Loxosceles laeta, performed by our group, in a previous study (Fernandes-Pedrosa et al., 2008), revealed a transcript with a sequence similar to the human complement component C3. Here we present the analysis of this transcript. cDNA fragments encoding the C3 homologue (Lox-C3) were amplified from total RNA isolated from the venom glands of L. laeta by RACE-PCR. Lox-C3 is a 5178 bps cDNA sequence encoding a 190kDa protein, with a domain configuration similar to human C3. Multiple alignments of C3-like proteins revealed two processing sites, suggesting that Lox-C3 is composed of three chains. Furthermore, the amino acids consensus sequences for the thioester was found, in addition to putative sequences responsible for FB binding. The phylogenetic analysis showed that Lox-C3 belongs to the same group as two C3 isoforms from the spider Hasarius adansoni (Family Salcitidae), showing 53% homology with these. This is the first characterization of a Loxosceles cDNA sequence encoding a human C3 homologue, and this finding, together with our previous finding of the expression of a FB-like molecule, suggests that this spider species also has a complement system. This work will help to improve our understanding of the innate immune system in these spiders and the ancestral structure of C3.

Prediction of disease severity in neuromyelitis optica by the levels of interleukin (IL)-6 produced during remission phase.

T helper type 17 (Th17) cytokines have been implicated in the pathogenesis of neuromyelitis optica (NMO). As humanized anti-interleukin (IL)-6R (tocilizumab) immunoglobulin (Ig)G has been used as disease-modifying therapy for NMO, the objective of our study was to investigate the role of endogenous IL-6 on NMO-derived CD4(+) T cell behaviour. High production of IL-6, IL-17 and IL-21 by CD4(+) T-cells was detected in NMO patients. Further, IL-21 and IL-6 levels were related directly to the level of neurological disabilities. The addition of anti-IL-6R IgG not only reduced directly the production of these cytokines, but also almost abolished the ability of activated autologous monocytes in enhancing IL-6, IL-17 and IL-21 release by CD4(+) T cells. In contrast, the production of IL-10 was amplified in those cell cultures. Further, anti-IL-6R monoclonal antibodies (mAb) also potentiated the ability of glucocorticoid in reducing Th17 cytokines. Finally, the in-vivo and in-vitro IL-6 levels were significantly higher among those patients who experienced clinical relapse during 2-year follow-up. In summary, our results suggest a deleterious role of IL-6 in NMO by favouring, at least in part, the expansion of corticoid-resistant Th17 cells.

Oral manifestations of neurofibromatosis type 1 in children with facial plexiform neurofibroma: report of three cases.

Neurofibromatosis type 1 (NF1) is a common autosomal genetic disorder with a prevalence of 1 in 3,000 births. NF1 is a complex syndrome characterized by many abnormalities and may affect all organ systems. Oral manifestations of NF1 occur frequently, but reports including NF1 children with facial plexiform neurofibromas and oral alterations are scant. Facial plexiform neurofibroma may cause asymmetry, disfigurement and usually arises from the trigeminal nerve. The aim of this paper is to to report three pediatric NF1 cases with facial plexiform neurofibroma presenting with oral manifestations, which were evaluated clinically and radiographically, and also to briefly review the literature. Patients presented with changes in the oral soft tissues, jaws, and teeth ipsilateral to the tumor.

Tumor necrosis factor beta (TNF-ß) NcoI polymorphism is associated with multiple sclerosis in Caucasian patients from Southern Brazil independently from HLA-DRB1.

This study evaluated the association of tumor necrosis factor beta (TNF-ß) NcoI polymorphism with the presence of multiple sclerosis (MS), disability, and HLA-DRB1 alleles in 208 Brazilian MS patients. As controls, 147 healthy individuals were included. The disability was evaluated at baseline and 5-year follow-up using the Expanded Disability Status Scale (EDSS). The TNF-ß genotypes were determined using PCR and restriction fragment length polymorphism and serum TNF-α level was determined using enzyme-linked immunosorbent assay. Among the MS patients, 166 (79.8 %) were white, 39 (18.7 %) were brown, and three (1.4 %) were Asian descents (those were excluded from the further analysis). Among the 205 MS patients, 149 (72.6 %) presented remitting-relapsing MS. The baseline and 5-year follow-up EDSS ranged from 0.0 to 3.0 and from 1.0 to 5.7, respectively. The TNFB2/B2 genotype was associated with the presence of MS among the white patients (p = 0.0443). Brown patients presented higher disability (p = 0.0234) and higher TNF-α levels (p = 0.0463) than white patients. White and brown patients carrying TNFB2/B2 genotype exhibited higher TNF-α levels (p = 0.0354 and p = 0.0309, respectively) than those with other geotypes. Association between TNF-ß NcoI genotypes and HLA-DRB1 alleles was not observed among the MS patients (p > 0.05). Taken together, TNFB2 allele was associated with the presence of MS independently of HLA-DRB1 in white patients and the TNFB2/B2 genotype was associated with increased TNF-α levels in white and brown patients, which could be an important genetic factor candidate for the susceptibility and pathogenesis of MS.

A new anti-loxoscelic serum produced against recombinant sphingomyelinase D Results of preclinical trials

Envenomation by Loxosceles species (brown spider) can lead to local dermonecrosis and to serious systemic effects. The main toxic component in the venom of these spiders is sphingomyelinase D (SMase D) and various isoforms of this toxin are present in Loxosceles venoms. We have produced a new anti-loxoscelic serum by immunizing horses with recombinant SMase D. In the present study, we compared the neutralization efficacy of the new anti-loxoscelic serum and anti-arachnidic serum (the latter serum is used for therapy for loxoscelism in Brazil) against the toxic effects of venoms from spiders of the genus Loxosceles. Neutralization tests showed that anti-SMase D serum has a higher activity against toxic effects of L. intermedia and L. laeta venoms and similar or slightly weaker activity against toxic effects of L. gaucho than that of Arachnidic serum. These results demonstrate that recombinant SMase D can replace venom for anti-venom production and therapy.

Transcriptome analysis of Loxosceles laeta (Araneae, Sicariidae) spider venomous gland using expressed sequence tags

The bite of spiders belonging to the genus Loxosceles can induce a variety of clinical symptoms, including dermonecrosis, thrombosis, vascular leakage, haemolysis, and persistent inflammation. In order to examine the transcripts expressed in venom gland of Loxosceles laeta spider and to unveil the potential of its products on cellular structure and functional aspects, we generated 3,008 expressed sequence tags (ESTs) from a cDNA library. Results: All ESTs were clustered into 1,357 clusters, of which 16.4% of the total ESTs belong to recognized toxin-coding sequences, being the Sphingomyelinases D the most abundant transcript; 14.5% include "possible toxins", whose transcripts correspond to metalloproteinases, serinoproteinases, hyaluronidases, lipases, C-lectins, cystein peptidases and inhibitors. Thirty three percent of the ESTs are similar to cellular transcripts, being the major part represented by molecules involved in gene and protein expression, reflecting the specialization of this tissue for protein synthesis. In addition, a considerable number of sequences, 25%, has no significant similarity to any known sequence. Conclusion: This study provides a first global view of the gene expression scenario of the venom gland of L. laeta described so far, indicating the molecular bases of its venom composition.

Seizures in patients with systemic lupus erythematosus: data from LUMINA, a multiethnic cohort (LUMINA LIV).

OBJECTIVE: To examine the predictors of time-to-seizure occurrence and their impact on damage accrual and mortality in LUMINA, a multiethnic (Hispanic, African American and Caucasian) cohort of patients with systemic lupus erythematosus. METHODS: Seizures were defined as per the American College of Rheumatology (ARC) nomenclature and case definitions for neuropsychiatric lupus syndromes. Factors associated with time-to-seizure occurrence occurring at or after diagnosis (TD) of systemic lupus erythematosus were examined by univariable and multivariable Cox proportional hazard regression analyses. The impact of seizures on damage accrual and mortality was also examined by multivariable analyses after adjusting for variables known to affect these outcomes. RESULTS: A total of 600 patients were included in these analyses. Of them, 40 (6.7%) developed seizures at or after TD; by multivariable analyses, disease activity and younger age were independent predictors of a shorter time-to-seizure occurrence (HR = 1.10 and 1.04; 95% CI 1.04 to 1.15 and 1.00 to 1.08, p = 0.0004 and 0.0304, respectively) whereas mucocutaneous involvement (HR = 0.34, 95% CI 0.16 to 0.41, p = 0.0039) and hydroxychloroquine use (HR = 0.35, 95% CI 0.15 to 0.80, p = 0.0131) were independent predictors of a longer time-to-seizure occurrence. Seizures were an independent contributor to damage accrual but not to mortality. CONCLUSIONS: Seizures tend to occur early in the course of systemic lupus erythematosus, and contribute to damage accrual. Younger age and disease activity are independent predictors of a shorter time-to-seizure occurrence; antimalarials appear to have a protective role in seizure occurrence.

Loxosceles spider venom induces the release of thrombomodulin and endothelial protein C receptor: implications for the pathogenesis of intravascular coagulation as observed in loxoscelism.

BACKGROUND: The venom of the spider Loxosceles can cause both local and systemic effects including disseminated intravascular coagulation. AIM: The aim of this study was to investigate the effects of the venom of Loxosceles intermedia (L. intermedia) and the purified Sphingomyelinase D (SMaseD) toxin upon the Protein C (PC) natural anticoagulant pathway. RESULTS: Both the venom and e purified SMaseD reduced the cell surface expression of thrombomodulin (TM) and Endothelial PC Receptor on endothelial cells in culture. The reduction of cell surface expression was caused by cleavage from the cell surface mediated by activation of an endogenous metalloproteinase. Reduction of TM and Endothelial PC Receptor on the surface of these cells resulted in an impaired ability of the cells to assist in the thrombin-induced activation of PC. CONCLUSION: This novel observation gives further insight into the mechanisms of the pathology induced by venom from Loxosceles spiders and may aid the development of a suitable therapy.

Sphingomyelinases D induce direct association of C1q to the erythrocyte membrane causing complement mediated autologous haemolysis.

Bites by Loxosceles spiders can induce severe clinical symptoms, including dermonecrosis, thrombosis, vascular leakage, haemolysis and persistent inflammation. The causative toxin is a sphingomyelinase D (SMase D) that cleaves sphingomyelin into choline and ceramide-1-phosphate. A similar enzyme, showing comparable bioactivity, is secreted by certain pathogenic corynebacteria and acts as a potent virulence factor. We have previously found that SMase D toxins led to an increased susceptibility of human erythrocytes (E) to activation of complement (C) via the classical pathway (CP) in the absence of antibodies. In the present study we have investigated the CP initiating components involved in the haemolysis induced by SMases from Corynebacterium pseudotuberculosis (PLD) and from Loxosceles intermedia venom (P1). When P1 or PLD treated E were incubated with C8-depleted human serum, an increase in C1q, serum amyloid protein (SAP) and C-reactive protein (CRP) binding was observed. While purified C1q, SAP and CRP were found to bind to P1 or PLD treated E, depletion of SAP or CRP from human serum did not prevent C-mediated lysis, suggesting that pentraxins are not involved in the initiation of C-activation. However depletion of C1 lead to a greatly reduced haemolysis, demonstrating that the activation of the CP is caused by direct binding of C1q to the SMase treated cells. Binding of fluid phase C-regulators C4b-binding protein and factor H was also observed, however these C-regulators in conjunction with the membrane bound C-regulators were unable to prevent haemolysis, demonstrating the potency of SMase D facilitated binding of C1 and activation of C.

Predictors of post-partum damage accrual in systemic lupus erythematosus: data from LUMINA, a multiethnic US cohort (XXXVIII).

OBJECTIVE: To determine the impact of pregnancy on systemic lupus erythematosus (SLE) outcome. METHODS: SLE patients, age >or=16 yrs, disease duration

Antioxidant responses in bean (Phaseolus vulgaris) roots colonized by arbuscular mycorrhizal fungi.

• Degradation of reactive oxygen species in arbuscular mycorrhizas (AM) may be an efficient mechanism to attenuate the activation of plant defenses. Here, we evaluated the activities of superoxide dismutase (SOD), guaiacol-peroxidase (GPX) and catalase (CAT) in bean (Phaseolus vulgaris) mycorrhizal roots at different conditions and stages of symbiosis development. • Bean plants were inoculated with Glomus clarum (Gc) or G. intraradices (Gi), under low (LP) and high P (HP) concentrations, and grown under glasshouse conditions. In a second experiment, bean seeds were treated with formononetin and inoculated with Gc under LP and HP conditions. The activities of SOD, GPX and CAT were evaluated. • SOD was induced only in roots colonized by Gc, at a late stage of the symbiosis development under LP, and at an early stage under HP. GPX was induced in roots colonized by Gc at an early time point and suppressed later under LP. In general, CAT was induced in roots colonized by Gc under LP. CAT activities in roots were dependent on P and formononetin treatment. • The possible roles of SOD, GPX and CAT in AM are discussed.

The capsular polysaccharides of Cryptococcus neoformans activate normal CD4(+) T cells in a dominant Th2 pattern.

Capsular components of Cryptococcus neoformans induce several deleterious effects on T cells. However, it is unknown how the capsular components act on these lymphocytes. The present study characterized cellular and molecular events involved in immunoregulation of splenic CD4(+) T cells by C. neoformans capsular polysaccharides (CPSs). The results showed that CPSs induce proliferation of normal splenic CD4(+) T cells, but not of normal CD8(+) T or B lymphocytes. Such proliferation depended on physical contact between CPSs and viable splenic adherent cells (SAC) and CD40 ligand-induced intracellular signal transduction. The absence of lymphoproliferation after fixation of SAC with paraformaldehyde has discarded the hypothesis of a superantigen-like activation. The evaluation of a cytokine pattern produced by the responding CD4(+) T lymphocytes revealed that CPSs induce a dominant Th2 pattern, with high levels of IL-4 and IL-10 production and undetectable inflammatory cytokines, such as TNF-alpha and IFN-gamma. Blockade of CD40 ligand by relevant mAb down-regulated the CPS-induced anti-inflammatory cytokine production and abolished the enhancement of fungus growth in cocultures of SAC and CD4(+) T lymphocytes. Our findings suggest that CPSs induce proliferation and differentiation of normal CD4(+) T cells into a Th2 phenotype, which could favor parasite growth and thus important deleterious effects to the host.

Attractiveness of black Shannon trap for phlebotomines.

A white Shannon-type trap was used for captures of female sand flies in the search for natural infection with flagellates, however, due to its low productivity and as a large number of phlebotomines settled on the researchers' black clothes, we decided to compare the relative attractiveness of black and white Shannon-type traps for sand flies. Several pairs of black and white traps were placed side by side in front of caves in four areas in the Serra da Bodoquena, Bonito county, State of Mato Grosso do Sul, Brazil, for a total of 12 observations and 44 h of capture. The experiment resulted in 889 phlebotomines captured, 801 on the black and 88 on the white trap, representing 13 species. The hourly Williams' means were 8.67 and 1.24, respectively, and the black/white ratio was 7.0:1.0. Lutzomyia almerioi, an anthropophilic species closely associated with caves, was predominant (89%). Only two other species, Nyssomyia whitmani and Psathyromyia punctigeniculata, also anthropophilic, were significantly attracted to the black rather than to the white trap (chi(2) test; p < or = 0.01). The difference between the diversity index of the two traps was not significant at level 0.05. The black trap in these circumstances was much more productive than the white, especially for anthropophilic species.

[Presence of Loxosceles similis Moenkhaus, 1898 (Araneae, Sicariidae) in Serra da Bodoquena, State of Mato Grosso do Sul, Brazil]. / Presença de Loxosceles similis Moenkhaus, 1898 (Araneae, Sicariidae) na Serra da Bodoquena, Estado de Mato Grosso do Sul, Brasil.

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.

Attractiveness of black Shannon trap for phlebotomines

A white Shannon-type trap was used for captures of female sand flies in the search for natural infection with flagellates, however, due to its low productivity and as a large number of phlebotomines settled on the researchers' black clothes, we decided to compare the relative attractiveness of black and white Shannon-type traps for sand flies. Several pairs of black and white traps were placed side by side in front of caves in four areas in the Serra da Bodoquena, Bonito county, State of Mato Grosso do Sul, Brazil, for a total of 12 observations and 44 h of capture. The experiment resulted in 889 phlebotomines captured, 801 on the black and 88 on the white trap, representing 13 species. The hourly Williams' means were 8.67 and 1.24, respectively, and the black/white ratio was 7.0:1.0. Lutzomyia almerioi, an anthropophilic species closely associated with caves, was predominant (89 percent). Only two other species, Nyssomyia whitmani and Psathyromyia punctigeniculata, also anthropophilic, were significantly attracted to the black rather than to the white trap (chi2 test; p <= 0.01). The difference between the diversity index of the two traps was not significant at level 0.05. The black trap in these circumstances was much more productive than the white, especially for anthropophilic species

Presença de Loxosceles similis Moenkhaus, 1898 (Araneae, Sicariidae) na Serra da Bodoquena, Estado de Mato Grosso do Sul, Brasil / 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 [quot ]Pitangueiras[quot ] cave and [quot ]Lago Azul[quot ] 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.

O veneno das aranhas do gênero Loxosceles causa lesão dermonecrótica e induz hemólise intravascular dependente de complemento, configurando um quadro clínico de intensa gravidade. No Brasil, as espécies L. gaucho L. intermedia e L. laeta, presentes no ambiente antrópico, têm sido apontadas como principais agentes do loxoscelismo. Além destas, existem outras espécies, que por predominarem no ambiente natural, não têm sido avaliadas quanto ao risco à saúde do homem, como é o caso de Loxosceles similis. O desenvolvimento de projeto de pesquisa, na Serra da Bodoquena, para observações ecológicas e identificação de insetos de interesse médico, possibilitou a captura de espécimens de Loxosceles similis na Serra da Bodoquena, Município de Bonito, Estado do Mato Grosso do Sul, Brasil, nas grutas Pitangueiras e do Lago Azul. Os parâmetros para identificação, características ambientais do habitat da espécie, bem como atualização de sua distribuição geográfica são objetos deste trabalho.

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)

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.