Resumo em Inglês:

Rabies is a viral zoonotic infectious disease that affects mammals and is caused by genotypes/species of the Lyssavirus genus (Rhabdoviridae, Mononegavirales), with the genotype 1 (classic rabies virus - RABV) being the most prevalent. Despite continuous efforts, rabies is still an incurable disease that causes thousands of deaths amongst humans worldwide. Due to a wide range of hosts and the different evolutionary paths of RABV in each host, several host-specific variants have arisen in an ongoing process. The result of RABV replication in nervous tissues may lead to two opposite clinical outcomes, i.e., paralytic/dumb form and encephalitic/furious one. The paralytic form creates dead-end hosts mainly amongst herbivores, while the furious form of the disease allows for augmented transmission when manifested in gregarious carnivores, as their natural aggressive behavior is accentuated by the disease itself. The aim of this article is to propose a theoretical model intended to explore how the rabies virus intrinsically modulates the immune system of different host classes, the pathological changes that the virus causes in these animals and how these elements favor its own perpetuation in nature, thus providing a basis for better prediction of the patterns this disease may present.

Resumo em Inglês:

Blooms of the cyanobacterium Trichodesmium occur in massive colored patches over large areas of tropical and subtropical oceans. Recently, the interest in such events has increased given their role in major nitrogen and carbon dioxide oceanic fluxes. Trichodesmium occurs all along the Brazilian coast and patches frequently migrate towards the coast. In this paper we screen the toxicity and toxin content of Trichodesmium blooms off the coast of Bahia state. Four samples, collected from February to April 2007, were analyzed. Organisms were identified and assessed for toxicity by means of several methods. Analogues of microcystins, cylindrospermopsins and saxitoxins were analyzed using HPLC. Microcystins were also assayed through ELISA. Results showed dominance of T. erythraeum, which makes up as much as 99% of cell counts. Other organisms found in smaller quantities include the dinoflagellates Prorocentrum minimum and P. rhathymum. Extracts from all samples delayed or interrupted sea urchin larval development, but presented no acute toxicity during a mouse bioassay. Saxitoxin congeners and microcystins were present at low concentrations in all samples, occurrences that had not previously been reported in the literature. Despite our finding of saxitoxin analogues and microcystins in Trichodesmium blooms, these toxins do not represent a potential harm to human health by primary contact. We conclude, based on our results and those reported in the recent literature, which differ from results published in 1963, that although toxins are present, there is no evidence that T. erythraeum blooms represent a threat to humans.

Resumo em Inglês:

Ionizing radiation has been successfully employed to modify the immunological properties of biomolecules. Very promising results were obtained when crude animal venoms, as well as isolated toxins, were treated with 60Co gamma rays, yielding toxoids with good immunogenicity. The achievement of modified antigens with lower toxicity and preserved or improved immunogenicity can be very useful. Ionizing radiation has already been proven to be a powerful tool to attenuate snake venom toxicity without affecting, and even increasing, their immunogenic properties. However, little is known about the modifications that irradiated molecules undergo and even less about the immunological response that such antigens elicit. In the present work, we investigated the immunological behavior of bothropstoxin-1, a K49 phospholipase, before and after irradiation. Structural modifications of the toxin were analyzed by SDS-PAGE. Isogenic mice were immunized with either the native or the irradiated toxin. The circulating antibodies were isotyped and titrated by ELISA. According to our data, irradiation promoted structural modifications in the toxin characterized by higher molecular weight forms of proteins (aggregates and oligomers). The results also indicated that irradiated toxins were immunogenic and antibodies elicited by them were able to recognize the native toxin in ELISA. These findings suggest that irradiation of toxic proteins can promote significant modifications in their structures; however they still retain many of the original antigenic and immunological properties of native proteins. Also, our data indicate that irradiated proteins induce higher titers of IgG2a and IgG2b, suggesting that Th1 cells are predominantly involved in the immune response.

Resumo em Inglês:

In the present study, Heterometrus fastigiousus venom (HFV) was employed as antigen to produce species-specific scorpion antivenom (SAV) in albino mice (NIH) strain. To determine SAV efficacy, it was pre-incubated with 10 LD50 of HFV and then injected subcutaneously into mice. Subsequently, mortality was observed after 24 hours. Minimum effective dose (MED) was 12.5 LD50 of HFV/mL of SAV. SAV effectiveness to reverse HFV-induced biochemical alterations in mice was analyzed by challenge method. Simultaneously, mice received subcutaneously 40% of 24-hour-LD50 of HFV and intravenously SAV. After four hours, changes in serum glucose, free amino acids, uric acids, pyruvic acid, cholesterol, total protein, alkaline phosphatase, acid phosphatase, lactic dehydrogenase and glutamate-pyruvate transaminase enzyme level were determined. Treatment with species-specific SAV resulted in the reversal of HFV-induced biochemical alterations.

Resumo em Inglês:

TsTX is an α-type sodium channel toxin that stimulates the discharge of neurotransmitters from neurons. In the present study we investigated which neurotransmitters are released in the hippocampus after TsTX injection and if they are responsible for electrographic or histopathological effects. Microdialysis revealed that the toxin increased glutamate extracellular levels in the hippocampus; however, levels of gamma-aminobutyric acid (GABA), glycine, 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were not significantly altered. Neurodegeneration in pyramidal cells of hippocampus and electroencephalographic alterations caused by the toxin were blocked by pretreatment with riluzole, a glutamate release inhibitor. The present results suggest a specific activity of TsTX in the hippocampus which affects only glutamate release.

Resumo em Inglês:

Scorpion stings are a public health problem in Morocco, especially among children, who experience the most severe cases. Epidemiological and clinical findings on scorpion stings in Fez, Morocco, were evaluated in this investigation. Of 163 cases that required medical attention, 62.6% were male children. The mean age of patients was 4.8 ± 3.4 years. The mean time between stings and first medical attention was 3.36 ± 2.5 hours. Almost all cases occurred in the summer (94%) and extremities represented the most frequent sting sites (86.5%). Local pain, hyperemia, scarification, vomiting, sweating, restlessness, tachycardia and tachypnea were the observed clinical symptoms. Regarding severity, 55.2% of patients belonged to class III, followed by class II (26.4%) and class I (18.4%). None of our patients received antivenom; however, all of them were treated symptomatically depending on clinical manifestations.

Resumo em Inglês:

Peptide toxins are usually highly bridged proteins with multipairs of intrachain disulfide bonds. Analysis of disulfide connectivity is an important facet of protein structure determination. In this paper, we successfully assigned the disulfide linkage of two novel peptide toxins, called HNTX-III and HNTX-IV, isolated from the venom of Ornithoctonus hainana spider. Both peptides are useful inhibitors of TTX-sensitive voltage-gated sodium channels and are composed of six cysteine residues that form three disulfide bonds, respectively. Firstly, the peptides were partially reduced by tris(2-carboxyethyl)-phosphine (TCEP) in 0.1 M citrate buffer containing 6 M guanidine-HCl at 40° C for ten minutes. Subsequently, the partially reduced intermediates containing free thiols were separated by reversed-phase high-performance liquid chromatography (RP-HPLC) and alkylated by rapid carboxamidomethylation. Then, the disulfide bonds of the intermediates were analyzed by Edman degradation. By using the strategy above, disulfide linkages of HNTX-III and HNTX-IV were determined as I-IV, II-V and III-VI pattern. In addition, this study also showed that this method may have a great potential for determining the disulfide bonds of spider peptide toxins.

Resumo em Inglês:

Histoplasmosis is a systemic mycosis caused by inhalation of Histoplasma capsulatum microconidia. The disease does not normally affect immunocompetent individuals after a single, transient inhalation exposure. However, longer exposure may cause chronic or disseminated acute pulmonary infection. Herein, we report the case of a 24-year-old immunocompetent patient, who presented fever, cough and dyspnea for one month. The chest radiography revealed interstitial infiltrate and diffuse micronodules. The patient reported having had close and prolonged contact with bats. Diagnosis was confirmed by positive double immunodifusion and immunoblotting assays. She was treated with ketoconazole (400 mg) and there was complete resolution of the disease.

Resumo em Inglês:

Schistosomes utilize proteinases to accomplish several activities such as tissue penetration, tissue digestion and evasion of host immune responses. Cathepsin L is a cysteine proteinase of the papain superfamily detected in their gut lumen which indicates that this enzyme contributes to the proteolysis of ingested hemoglobin. Due to the roles played in the schistosome biology, proteolytic enzymes are considered potential targets for developing and guiding antischistosomal therapies. In the present work, the cathepsin L1 cDNA coding of Schistosoma mansoni was cloned into the pAE vector that provides high-level expression of heterologous proteins in Escherichia coli. The recombinant protein was expressed as inclusion bodies, purified under denaturing conditions through nickel-charged chromatography and used for experimental animal vaccination. ELISA was performed with the pooled sera. Although this protein was shown to be immunogenic, mice immunized with three doses of recombinant protein plus aluminum hydroxide as adjuvant were not protected against S. mansoni infection.

Resumo em Inglês:

Despite measures adopted to control American visceral leishmaniasis (AVL), the disease is spreading in a fast and worrying way throughout western São Paulo state. The aim of this work was to study the variables involved in the disease cycle as well as the effectiveness of controlling measures. The study was carried out in the microregion of Dracena, which is composed of twelve cities and belongs to Alta Paulista, a region of western São Paulo. The necessary data were provided by the Superintendence for Endemic Disease Control and Adolfo Lutz Institute, Regional Laboratory of Presidente Prudente. From August 2005 to January 2008, the following factors were observed: detection of phlebotomine sandflies in the cities and periods in which dogs or humans were diagnosed; number of human deaths; prevalence of suspected dogs tested by serology; percentage of euthanasia in suspected dogs; a possible correlation between positive dogs and cases of the disease in humans; and the disease prevalence among municipalities from the studied region. It was verified that, despite the strategies adopted in Dracena microregion to control AVL, the disease continues to rise. Thus, some procedures of the AVL Monitoring and Control Program should be reviewed, to grant the initiative more credibility and effectiveness.

Resumo em Inglês:

ALT-C, an ECD motif (glutamic acid, cysteine, aspartic acid) disintegrin from Bothrops alternatus snake venom, induces α2β1 integrin-mediated signaling and neutrophil chemotaxis. In vitro, in human umbilical vein endothelial cells (HUVEC), ALT-C induces cell proliferation, thus showing an interesting potential for tissue regeneration studies. This work aimed to evaluate the influence of ALT-C in myoblast viability and differentiation. Myoblasts were obtained from hind limb muscles of 3 to 4-day old Wistar rats. The cells were incubated with ALT-C at different concentrations and incubation periods were followed by total RNA isolation. cDNA synthesis and real time polymerase chain reaction (PCR) were performed with primers of myoD as well as of both (slow and fast) myosin heavy chain isoforms (MHC). ECD-disintegrin increased myoblast viability in a dose-dependent way, mostly with 50 to 100 nM concentrations, and such effect was more prevalent after 48 hours. No changes in gene expression of both MHC isoforms were observed in ALT-C-treated cells. MyoD expression was not detected, which suggests that myoblasts were in mature stages. Protease activity and cytokine array tested in a medium of 50 nM ALT-C-treated cells after 48 hours were not different from controls. In conclusion, it was shown that myoblats are sensitive to ALT-C indicating an integrin-mediated intracellular signaling that increases cell viability.

Resumo em Inglês:

The serum kinetics of Calloselasma rhodostoma (Malayan pit viper) venom - specifically two of its components, the major hemorrhagin (rhodostoxin) and a thrombin-like enzyme - was examined in a rabbit by double-sandwich enzyme-linked immunosorbent assay (ELISA). The animal received intramuscularly a 1.0-mg/kg dose of C. rhodostoma venom. The venom level in serum peaked 12 hours after the injection, followed by a gradual decline and finally reached low rates 72 hours after administration. The serum kinetic profile of venom components, however, did not correspond to the profile of the whole C. rhodostoma venom. The serum levels of the C. rhodostoma thrombin-like enzyme increased slowly and peaked only 48 hours post-injection. Then both thrombin-like enzyme and rhodostoxin remained at relatively high levels 72 hours after administration. Data suggest that various venom components bind to tissue at the injection site with different affinities and that conjugated venom components were continuously released into circulation at different rates. The prolonged high serum levels of both thrombin-like enzyme and hemorrhagin are consistent with the clinical picture of prolonged clotting deficiency in severe cases of C. rhodostoma envenomation. Our results also suggest that since venom components are being released into and eliminated from the circulation at different rates, the "average composition" of the venom antigen in the circulation changes over time. This implies that data from ELISA quantification of antigen levels from serum venom employing "whole venom" as reagent must be interpreted with care.

Resumo em Inglês:

The following notes on gestation periods and litter size in seven specimens of Leiurus quinquestriatus are presented as observational data. Specimens of Leiurus quinquestriatus from southern Egypt and southern Israel were mated in the laboratory during 2007; afterwards, gestation periods and litter sizes of all females were recorded. Previous studies on this species reported that the gestation period ranged from 150 to 155 days and that litter size was between 12 and 99 offspring. In the present study, gestation periods in specimens from both geographic regions varied from 155 to 227 days and litter sizes were between 35 and 87 offspring. The current contribution expands on previously published data on gestation periods and supports previously reported litter size in Leiurus quinquestriatus.

Resumo em Inglês:

A total of 40 bacteria have been successfully isolated from internal organs of the American bullfrog (Rana catesbeiana) raised in Malaysia, namely, eight isolates of Aeromonas spp., 21 of Edwardsiella spp., six of Flavobacterium spp. and five of Vibrio spp. In terms of antibiotic susceptibility testing, each isolate was tested against 21 antibiotics, resulting in 482 (57.3%) cases of sensitivity and 61 (7.3%) cases of partial sensitivity. Meanwhile, 297 (35.4%) bacterial isolates were registered as resistant. The multiple antibiotic resistance (MAR) index of each bacterial species indicated that bacteria from raised bullfrogs have been exposed to tested antibiotics with results ranging from 0.27 to 0.39. Additionally, high percentages of heavy metal resistance among these isolates were observed, with values ranging from 85.0 to 100.0%. The current results provided us information on bacterial levels of locally farmed bullfrogs exposed to copper, cadmium, chromium as well as 21 types of antibiotics.

Resumo em Inglês:

Cutaneous leishmaniases are anthropozoonoses that involve many species of Leishmania and a wide variety of wild mammalian hosts, thus presenting high importance to public health. This study reports the second case of feline leishmaniasis in Mato Grosso do Sul state, in which Leishmania (Leishmania) amazonensis was found in a domestic cat from Ribas do Rio Pardo. Clinical signs were similar to those observed in other diseases commonly diagnosed in cats, such as cryptococcosis and sporotrichosis. Cutaneous leishmaniasis should, therefore, be added to differential diagnoses by feline veterinary practitioners, and also adequate investigations should be carried out to verify the relevance of domestic cats as L. amazonensis reservoirs.