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We report a structural and functional proteomics characterization of venoms of the two subspecies (Bothrops bilineatusbilineatusand B. b. smaragdinus) of the South American palm pit viper from the Brazilian state of Rondônia and B. b. smaragdinusfrom Perú. These poorly known arboreal and mostly nocturnal generalist predators are widely distributed in lowland rainforests throughout the entire Amazon region, where they represent an important cause of snakebites. The three B. bilineatusspp. venom samples exhibit overall conserved proteomic profiles comprising components belonging to 11 venom protein classes, with PIII (34–40% of the total venom proteins) and PI (8–18%) SVMPs and their endogenous tripeptide inhibitors (SVMPi, 8–10%); bradykinin-potentiating-like peptides (BBPs, 10.7–15%); snake venom serine proteinases (SVSP, 5.5–14%); C-type lectin-like proteins (CTL, 3–10%); phospholipases A2(PLA2, 2.8–7.6%); cysteine-rich secretory proteins (CRISP, 0.9–2.8%); l-amino acid oxidases (LAO, 0.9–5%) representing the major components of their common venom proteomes. Comparative analysis of the venom proteomes of the two geographic variants of B. b. smaragdinuswith that of B. b. bilineatusrevealed that the two Brazilian taxa share identical molecules between themselves but not with Peruvian B. b. smaragdinus, suggesting hybridization between the geographically close, possibly sympatric, Porto Velho (RO, BR) B. b. smaragdinusand B. b. bilineatusparental populations. However, limited sampling does not allow determining the frequency of this event. The toxin arsenal of the South American palm pit vipers may account for the in vitro recorded collagenolytic, caseinolytic, PLA2, l-amino acid oxidase, thrombin-like and factor X-activating activities, and the clinical features of South American palm pit viper envenomings, i.e., local and progressively ascending pain, shock and loss of consciousness, spontaneous bleeding, and profound coagulopathy. The remarkable cross-reactivity of the Brazilian pentabothropic SAB antivenom toward the heterologous B. b. bilineatusvenom suggests that the paraspecific antigenic determinants should have been already present in the venom of the last common ancestor of the Bothrops″jararaca″ and ″taeniatus″ clades, about 8.5 Mya in the mid-late Miocene epoch of the Cenozoic era. The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the data set identifiers PXD020043, PXD020026, and PXD020013.

New treatments that circumvent the pitfalls of traditional antivenom therapies are critical to address the problem of snakebite globally. Numerous snake venom toxin inhibitors have shown promising cross-species neutralization of medically significant venom toxins in vivoand in vitro. The development of high-throughput approaches for the screening of such inhibitors could accelerate their identification, testing, and implementation and thus holds exciting potential for improving the treatments and outcomes of snakebite envenomation worldwide. Energetics-based proteomic approaches, including thermal proteome profiling and proteome integral solubility alteration (PISA) assays, represent “deep proteomics” methods for high throughput, proteome-wide identification of drug targets and ligands. In the following study, we apply thermal proteome profiling and PISA methods to characterize the interactions between venom toxin proteoforms in Crotalus atrox(Western Diamondback Rattlesnake) and the snake venom metalloprotease (SVMP) inhibitor marimastat. We investigate its venom proteome-wide effects and characterize its interactions with specific SVMP proteoforms, as well as its potential targeting of non-SVMP venom toxin families. We also compare the performance of PISA thermal window and soluble supernatant with insoluble precipitate using two inhibitor concentrations, providing the first demonstration of the utility of a sensitive high-throughput PISA-based approach to assess the direct targets of small molecule inhibitors for snake venom.

ABSTRACTThe monocled cobra (Naja kaouthia) is among the most feared snakes in Southeast Asia due to its toxicity, which is predominantly derived from long-chain α-neurotoxins. The only specific treatment for snakebite envenoming is antivenom based on animal-derived polyclonal antibodies. Despite the lifesaving importance of these medicines, major limitations in safety, supply consistency, and efficacy create a need for improved treatments. Here, we describe the discovery and subsequent optimization of a recombinant human monoclonal immunoglobulin G antibody against α-cobratoxin using phage display technology. Affinity maturation by light chain-shuffling resulted in a significant increase in in vitroneutralization potency and in vivoefficacy. The optimized antibody prevented lethality when incubated with N. kaouthiawhole venom prior to intravenous injection. This study is the first to demonstrate neutralization of whole snake venom by a single recombinant monoclonal antibody, thus providing a tantalizing prospect of bringing recombinant antivenoms based on human monoclonal or oligoclonal antibodies to the clinic.

ABSTRACTBrucella abortusis an intracellular pathogen of monocytes, macrophages, dendritic cells, and placental trophoblasts. This bacterium causes a chronic disease in bovines and in humans. In these hosts, the bacterium also invades neutrophils; however, it fails to replicate and just resists the killing action of these leukocytes without inducing significant activation or neutrophilia. Moreover, B. abortuscauses the premature cell death of human neutrophils. In the murine model, the bacterium is found within macrophages and dendritic cells at early times of infection but seldom in neutrophils. Based on this observation, we explored the interaction of mouse neutrophils with B. abortus. In contrast to human, dog, and bovine neutrophils, naive mouse neutrophils fail to recognize smooth B. abortusbacteria at early stages of infection. Murine normal serum components do not opsonize smooth Brucellastrains, and neutrophil phagocytosis is achieved only after the appearance of antibodies. Alternatively, mouse normal serum is capable of opsonizing rough Brucellamutants. Despite this, neutrophils still fail to kill Brucella, and the bacterium induces cell death of murine leukocytes. In addition, mouse serum does not opsonize Yersinia enterocoliticaO:9, a bacterium displaying the same surface polysaccharide antigen as smooth B. abortus. Therefore, the lack of murine serum opsonization and absence of murine neutrophil recognition are specific, and the molecules responsible for the Brucellacamouflage are N-formyl-perosamine surface homopolysaccharides. Although the mouse is a valuable model for understanding the immunobiology of brucellosis, direct extrapolation from one animal system to another has to be undertaken with caution.

Animal-derived antivenoms constitute the mainstay in the therapy of snakebite envenoming. Antivenoms are manufactured by immunizing animals, usually horses, with venoms from a single or several medically-relevant snake species. Antivenoms are constituted by either whole IgG molecules or the immunoglobulin fragments F(ab')2 and Fab, obtained by digestion with pepsin and papain, respectively. Differences in the pharmacokinetics of these active substances have pharmacodynamic implications. Novel technological possibilities may improve the quality of antivenoms in the future, as well as their microbial safety. Antivenom administration might induce early and late adverse reactions, whose possible mechanisms are discussed. Owing to the large variety in the composition of snake venoms and to the need to demonstrate neutralization of relevant snake venoms in different countries, a meticulous preclinical and clinical assessment of antivenom efficacy and safety is required before an antivenom is introduced into clinical application. The accessibility of antivenoms in low-income tropical countries is of concern and efforts should be directed at guaranteeing the access of safe and effective antivenoms at affordable prices and their correct clinical use in these countries.

Lys49-phospholipase A2 homologues constitute a large family of toxins present in the venoms of viperid snake species, which despite lacking catalytic activity, cause significant skeletal muscle necrosis. The main structural determinants of this toxic effect have been experimentally mapped to a region near their C-terminus (115-129), which combines cationic and hydrophobic/aromatic amino acid residues. Short (13-mer) synthetic peptides representing this C-terminal region can mimick several of the effects of Lys49 PLA2 homologues. In addition to their ability to damage muscle cells, these peptides display antibacterial, antiendotoxic, antifungal, antiparasite, and antitumor activities, as well as VEGF-receptor 2 (KDR)-binding and heparin-binding properties. Modifications of their sequences have shown possibilities to enhance their effects upon prokaryotic cells, while decreasing toxicity for eukaryotic cells. This review presents an updated summary on the biomimetic actions exerted by such peptides, and highlights their potential value as molecular tools or as drug leads in diverse biomedical areas.

A particular subgroup of toxins with phospholipase A2 (PLA2) structure, but devoid of this enzymatic activity, is commonly found in the venoms of snakes of the family Viperidae, and known as the PLA2 homologues. Among these, the most frequent type presents a lysine residue at position 49 (Lys49), in substitution of the otherwise conserved aspartate (Asp49) of catalytically-active PLA2s. A brief and updated overview of these toxic PLA2 homologues is presented, emphasizing their various biological activities, both in vivo and in vitro. The relevance of these bioactivities in relation to their possible adaptive roles for the snakes is discussed. Finally, experiments designed to assess the validity of such hypothetical roles are suggested, to stimulate future studies in this field.

The therapy of snakebite envenomation has been based on the parenteral administration of animal-derived antivenoms. Despite the success of this treatment at reducing the impact of snakebite mortality and morbidity, mostly due to their capacity to neutralize systemically- acting toxins, antivenoms are of relatively low efficacy in the prevention of venom-induced local tissue damage, which often leads to permanent disability. The issue of safety also remains a concern, particularly for some antivenoms which induce a relatively high incidence of adverse reactions. Consequently, there is a need to improve the therapy of snakebite envenomations on the following lines: (a) the technologies to produce antivenoms require improvements aimed at obtaining more refined preparations of higher efficacy and safety, while being affordable for the public health systems of developing countries. (b) The growing knowledge on the biochemistry and toxicology of snake venoms should pave the way for the identification of natural and synthetic inhibitors of venom toxins, particularly of those involved in local tissue pathology. Such inhibitors might become a highly effective therapeutic tool for the abrogation of venominduced local tissue damage. (c) A better knowledge of the inflammatory events secondary to venom actions may open the possibility of modulating such response, in order to prevent further tissue damage and to promote successful tissue repair and regeneration. A global partnership, involving many participants and combining scientific, technological and public health actions, is required to achieve a leap forward in the treatment of snakebite envenomations world-wide.

Envenomations due to snake bites are commonly treated by parenteral administration of horse or sheep-derived polyclonal antivenoms aimed at the neutralization of toxins. However, despite the widespread success of this therapy, it is still important to search for different venom inhibitors, either synthetic or natural, that could complement or substitute for the action of antivenoms. Several plants have been utilized in folk medicine as antiophidian. However, only a few species have been scientifically investigated and still less had their active components isolated and characterized both structurally and functionally. This article presents a review of plants showing neutralizing properties against snake venoms which were assayed in research laboratories, correlating them with ethnopharmacological studies, as (i) the part of the plant used as antidote, (ii) its respective genus and family and (iii) inhibition of the main pharmacological, toxic and enzymatic activities of snake venoms and isolated toxins. Protective activity of many of these plants against the lethal action of snake venoms has been confirmed by biological assays. Compounds in all of them belong to chemical classes capable of interacting with macromolecular targets (enzymes or receptors). Popular culture can often help to guide scientific studies. In addition, biotechnological application of these inhibitors, as helpful alternative or supplemental treatments to serum therapy, and also as important models for synthesis of new drugs of medical interest, needs to be better oriented and scientifically explored.

ABSTRACTThe activities of short synthetic, nonhemolytic peptides derived from the C-terminal region of myotoxin II, a catalytically inactive phospholipase A2homologue present in the venom of the snake Bothrops asper, have been shown to reproduce the bactericidal activity of the parent protein. They combine cationic and hydrophobic-aromatic amino acids, thus functionally resembling the antimicrobial peptides of innate defenses. This study evaluated the antimicrobial and antiendotoxic properties of a 13-mer derivative peptide of the C-terminal sequence from positions 115 to 129 of myotoxin II, named pEM-2. This peptide (KKWRWWLKALAKK) showed bactericidal activity against both gram-positive and gram-negative bacteria. In comparison to previously described peptide variants derived from myotoxin II, the toxicity of pEM-2 toward eukaryotic cells in culture was significantly reduced, being similar to that of lactoferricin B but lower than that of polymyxin B. The all-denantiomer of pEM-2 [pEM-2 (d)] retained the same bactericidal potency of its l-enantiomeric counterpart, but it showed an enhanced ability to counteract the lethal activity of an intraperitoneal lipopolysaccharide challenge in mice, which correlated with a significant reduction of the serum tumor necrosis factor alpha levels triggered by this endotoxin. Lethality induced by intraperitoneal infection of mice with Escherichia colior Salmonella entericaserovar Typhimurium was reduced by the administration of pEM-2 (d). These results demonstrate that phospholipase A2-derived peptides may have the potential to counteract microbial infections and encourage further evaluations of their actions in vivo.

To characterize the host response to venom from snakes of the familyViperidaein Costa Rica, we investigated the release of cytokines IL-1, IL-6, IL-8, TNF-α, MIP-1β, and RANTES in pediatric patients who were bitten by a snake.

BnSP-7, a Lys49 myotoxic phospholipase A2 homologue from Bothrops neuwiedi pauloensis venom, was structurally and functionally characterized. Several biological activities were assayed and compared with those of the chemically modified toxin involving specific amino acid residues. The cDNA produced from the total RNA by RT-PCR contained approximately 400 bp which codified its 121 amino acid residues with a calculated pI and molecular weight of 8.9 and 13,727, respectively. Its amino acid sequence showed strong similarities with several Lys49 phospholipase A2 homologues from other Bothrops sp. venoms. By affinity chromatography and gel diffusion, it was demonstrated that heparin formed a complex with BnSP-7, held at least in part by electrostatic interactions. BnSP-7 displayed bactericidal activity and promoted the blockage of the neuromuscular contraction of the chick biventer cervicis muscle. In addition to its in vivo myotoxic and edema-inducing activity, it disrupted artificial membranes. Both BnSP-7 and the crude venom released creatine kinase from the mouse gastrocnemius muscle and induced the development of a dose-dependent edema. His, Tyr, and Lys residues of the toxin were chemically modified by 4-bromophenacyl bromide (BPB), 2-nitrobenzenesulfonyl fluoride (NBSF), and acetic anhydride (AA), respectively. Cleavage of its N-terminal octapeptide was achieved with cyanogen bromide (CNBr). The bactericidal action of BnSP-7 on Escherichia coli was almost completely abolished by acetylation or cleavage of the N-terminal octapeptide. The neuromuscular effect induced by BnSP-7 was completely inhibited by heparin, BPB, acetylation, and CNBr treatment. The creatine kinase releasing and edema-inducing effects were partially inhibited by heparin or modification by BPB and almost completely abolished by acetylation or cleavage of the N-terminal octapeptide. The rupture of liposomes by BnSP-7 and crude venom was dose and temperature dependent. Incubation of BnSP-7 with EDTA did not change this effect, suggesting a Ca2+-independent membrane lytic activity. BnSP-7 cross-reacted with antibodies raised against B. moojeni (MjTX-II), B. jararacussu (BthTX-I), and B. asper (Basp-II) myotoxins as well as against the C-terminal peptide (residues 115–129) from Basp-II.

Myotoxic phospholipases A2 (PLA2s; group II) account for most of the muscle-tissue damage that results from envenomation by viperid snakes. In the venom of the Godman's viper (Cerrophidion godmani, formerly Bothrops godmani), an enzymically active PLA2 (myotoxin I) and an inactive, Lys-49 variant (myotoxin II) induce extensive muscle damage and oedema. In this study, two distinct myotoxin inhibitor proteins of C. godmani, CgMIP-I and CgMIP-II, were purified directly from blood plasma by selective binding to affinity columns containing either myotoxin I or myotoxin II, respectively. Both proteins are glycosylated, acidic (pI = 4) and composed of 20-25-kDa subunits that form oligomers of 110 kDa (CgMIP-I) or 180 kDa (CgMIP-II). In inhibition studies, CgMIP-I specifically neutralized the PLA2 and the myotoxic, oedema-forming and cytolytic activities of myotoxins I, whereas CgMIP-II selectively inhibited the toxic properties of myotoxin II. N-terminal amino acid sequence analysis and sequencing of cDNAs encoding the two inhibitors revealed that CgMIP-I is similar to γ-type inhibitors, which share a pattern of cysteine residues present in the Ly-6 superfamily of proteins, whereas CgMIP-II shares sequence identity with α-type inhibitors that contain carbohydrate-recognition-like domains, also found in C-type lectins and mammalian PLA2 receptors. N-terminal sequencing of myotoxin I revealed a different primary structure from myotoxin II [De Sousa, Morhy, Arni, Ward, Díaz and Gutiérrez (1998) Biochim. Biophys. Acta 1384, 204-208], which provides insight into the nature of such pharmacological specificity.

Myotoxin-I (MjTX-I) was purified to homogeneity from the venom of Bothrops moojeni by ion-exchange chromatography on CM-Sepharose. Its molecular weight, estimated by SDS–PAGE, was 13,400 (reduced) or 26,000 (unreduced). The extinction coefficient (E1.0 mg/ml1.0 cm) of MjTX-I was 1.145 at λ = 278 nm, pH 7.0, and its isoelectric point was 8.2 at ionic strength μ = 0.1. When lyophilized and stored at 4°C, dimeric, trimeric, and pentameric forms of the protein were identified by SDS–PAGE. This “heterogeneous” sample could be separated into three fractions by gel filtration on Sephadex G-50. The fractions were analyzed by isoelectric focusing, immunoelectrophoresis, and amino acid composition, which indicated that heterogeneity was the result of different levels of self-association. Protein sequencing indicated that MjTX-I is a Lys49 myotoxin and consists of 121 amino acids (Mr = 13,669), containing a high proportion of basic and hydrophobic residues. It shares a high degree of sequence identity with other Lys49 PLA2-like myotoxins, but shows a significantly lower identity with catalytically active Asp49 PLA2s. The three-dimensional structure of MjTX-I was modeled based on the crystal structures of three highly homologous Lys49 PLA2-like myotoxins. This model showed that the amino acid substitutions are conservative, and mainly limited to three structural regions: the N-terminal helix, the β-wing region, and the C-terminal extended random coil. MjTX-I displays local myotoxic and edema-inducing activities in mice, and is lethal by intraperitoneal injection, with an LD50 value of 8.5 ± 0.8 mg/kg. In addition, it is cytotoxic to myoblasts/myotubes in culture, and disrupts negatively charged liposomes. In comparison with the freshly prepared dimeric sample, the more aggregated forms showed significantly reduced myotoxic activity. However, the edema-inducing activity of MjTX-I was independent of molecular association. Phospholipase A2 activity on egg yolk, as well as anticoagulant activity, were undetectable both in the native and in the more associated forms. His, Tyr, and Trp residues of the toxin were chemically modified by specific reagents. Although the myotoxic and lethal activities of the modified toxins were reduced by these treatments, neither its edema-inducing or liposome-disrupting activities were significantly altered. Rabbit antibodies to native MjTX-I cross-reacted with the chemically modified forms, and both the native and modified MjTX-I preparations were recognized by antibodies against the C-terminal region 115–129 of myotoxin II from B. asper, a highly Lys49 PLA2-homologue with high sequencial similarity.

The edema effect induced in mice by venoms of Crotalus durissus durissusand Lachesis muta stenophryswas studied. Minimum edema-forming doses were 11 and 5 μg, respectively. Edema developed very rapidly after injections of both venoms and reached a maximum at 6 hr. Neutralizing activity was tested by preincubation of the venoms with polyvalent antivenom. The edema induced by the venom of L. m. stenophryswas partially neutralized, whereas that induced by the venom of C. d. durissuswas not neutralized.

The region 115–129 of myotoxin II, a catalytically inactive Lys49 phospholipase A2, was previously shown to constitute a heparin-binding site and to be involved in its cytolytic actionin vitro.An immunochemical approach was utilized to further explore the role of this region in the toxic activities of myotoxin II. By using a carrier-linked 13-mer synthetic peptide as immunogen, rabbit polyclonal antibodies against region 115–129 were obtained. These antibodies were able to bind to the native protein and to inhibit its myotoxic and cytolytic effects in preincubation-type neutralization experiments. Antibodies to peptide 115–129 formed precipitating macromolecular complexes in gel immunodiffusion, demonstrating the oligomeric state of myotoxin II not only in its crystalline structure (dimeric), but also in solution. Analyses of the antibody response to carrier-linked peptide 115–129 and native myotoxin II suggest that region 115–129, although potentially immunogenic, is not an immunodominant B-cell epitope of this protein, failing to elicit significant antibody responses in animals immunized with the native toxin. Antibodies to peptide 115–129 cross-reacted with 15 purified class II myotoxic phospholipases A2found in snake venoms of the generaBothrops, Agkistrodon, Trimeresurus,andVipera,but not with the recombinant human class II phospholipase A2, for which no toxic actions have been described. Myotoxic phospholipases of the class I (notexin) and class III (bee venom) groups were not recognized by antibodies to p115–129. These results demonstrate that the overall antigenic structure of region 115–129 is conserved among class II myotoxic phospholipases A2, despite differences in their corresponding amino acid sequences. Based on the accumulated experimental evidence, a model of the myotoxic region of myotoxin II, and possibly of related class II Lys49 phospholipase A2myotoxins, is proposed.

Phospholipases A2 containing Lys‐49 have been reported to be extremely weak or inactive as enzyme. We have recently shown that basic proteins I and II (BP‐I and BP‐II), Lys‐49‐PLA2s isolated from the venom of Trimeresurus flavoviridis (Habu snake), are potent to hydrolyze the arachidonate of 2‐arachidonoyl‐1‐stearoyl‐L‐3‐phosphatidylcholine (ASPC) in bilayer vesicles. In order to ensure such enzymatic activity of Lys‐49‐PLA2s, two other Lys‐49‐PLA2s from different snake venoms, myotoxin II (from Bothrops asper) and App‐K49 (form Agkistrodon piscivorus piscivorus), were examined. Myotoxin II was found to be very active, even more potent than BP‐II, liberating about 80% of arachidonic acid from liposomes. App‐K49 was also active (about 50%) for ASPC liposomes. They were very weak or almost inactive for ASPC micelles and monomers. All these Lys‐49‐PLA2s were inactive for ASPC liposomes in the absence of Ca2+. These results clearly demonstrated that Lys‐49‐PLA2s are the enzymes to hydrolyze the C2‐ester bond of ASPC in bilayer membranes.

The pathogenesis of hemorrhage and other local effects induced by the metalloproteinase BaP1, isolated from Bothrops asper venom, was investigated using various in vivo and in vitro models. Upon intramascular injection in mice BaP1 caused rapid hemorrhage in mascular and adipose tissues. Vital microscopy using mouse cremaster muscle evidenced the formation of multiple hemorrhagic foci of an explosive character, originating from capillaries and small venules. In contrast to crude B. asper venom, which besides hemorrhage also induced myonecrosis and thrombosis, vital microscopy detected only hemorrhage after application of BaP1, during the 40-min observation period. However, histological observation in mouse gastrocnemius muscle evidenced a few areas of limited myonecrosis several hours after BaP1 injection, followed by conspicuous inflammatory response. Myonecrosis was followed by an incomplete regenerative response, since regenerating muscle fibers were interspersed with fibrosis in some areas. Metalloproteinase BaP1 was not cytotoxic to human and murine endothelial cells in culture, causing only a mild detachment from the culture plate. Bap1 hydrolyzed types I and IV collage, fibronectin, and laminin upon incubation with these extracellular matrix proteins in vitro. These results suggest that hemorrhage induced by Bap1 is due primarily to the protcolytic degradation to basement membrane component of microvessels and that endothelial cell disruption may be a secondary event. It is concluded that, in addition to hemorrhage. BaP1 contributes to the local tissue damage caused by the venom by inducing myonecrosis, inflammation and extracellular matrix alterations. Copyright 1995, 1999 Academic Press

A new myotoxic phospholipase A2was isolated from the venom of the arboreal snakeBothriechis schlegelii(formerlyBothrops schlegelii) from Costa Rica, by ion-exchange chromatography on CM-Sephadex.B. schlegeliimyotoxin I is a basic protein (pI> 9.3) with a subunit molecular weight of 15 kDa, which migrates as a dimer in sodium dodecyl sulfate–polyacrylamide gel electrophoresis under nonreducing conditions. This myotoxin is recognized by antibodies generated againstBothrops aspermyotoxin II (a lysine-49 phospholipase A2), by both enzyme-immunoassay and gel immunodiffusion, in the latter case with a pattern of partial identity. The toxin induces rapid myonecrosis upon intramuscular injection in mice, as evidenced by the early increase in plasma creatine kinase activity and by direct intravital microscopic observation.B. schlegeliimyotoxin I also induces edema in the mouse footpad assay and exerts lethal activity (LD50∼2.5 μg/g) upon intravenous injection. The toxin has a low phospholipase A2activity (4.2 μEq·mg−1·min−1) using egg yolk phospholipids as substrate. It also shows a weak anticoagulant effectin vitro.Its N-terminal sequence, SMYELGKMILLETGKNAATSYIAYG, shows 93% homology with bothBothrops aspermyotoxin II andB. jararacussubothropstoxin I, suggesting thatB. schlegeliimyotoxin I may be a new lysine-49 variant of this family of myotoxic phospholipases A2.

A protein that neutralizes the biological activities of basic phospholipase A2 (PLA2) myotoxin isoforms from the venom of the snake Bothrops asper was isolated from its blood by affinity chromatography with Sepharose-immobilized myotoxins. Biochemical characterization of this B. asper myotoxin inhibitor protein (BaMIP) indicated a subunit molecular mass of 23–25 kDa, an isoelectric point of 4, and glycosylation. Gel-filtration studies revealed a molecular mass of 120 kDa, suggesting that BaMIP possesses an oligomeric structure composed of five 23–25 kDa subunits. Functional studies indicated that BaMIP inhibits the PLA2 activity of B. asper basic myotoxins I and III, as well as the myotoxicity and edema-forming activity in vivo and cytolytic activity in vitro towards cultured endothelial cells, of all four myotoxin isoforms (I–IV) tested. Sequence analysis of the first 63 amino acid residues from the N-terminus of BaMIP indicated more than 65% sequence similarity to the PLA2 inhibitors isolated from the blood of the crotalid snakes Trimeresurus flavoviridis and Agkistrodon blomhoffii siniticus. These inhibitors also share sequences similar to the carbohydrate-recognition domains of human and rabbit cellular PLA2 receptors, suggesting a common domain evolution among snake plasma PLA2 inhibitors and mammalian PLA2 receptors. Despite this similarity, this is the first description of a natural anti-myotoxic factor from snake blood.

In vivo, hemorrhagic toxins isolated from snake venoms cause a disorganization of the basal lamina of capillaries, with a concomitant degenerative process of endothelial cells. In this study we investigated the effects of BaH-1, a hemorrhagic metalloproteinase purified from the venom of Bothrops asper, on a murine endothelial cell line of capillary origin. A quantitative cytotoxicity assay based on the release of lactic dehydrogenase was utilized. BaH-1, despite its potent hemorrhagic activity, did not exert direct cytolytic activity on the endothelial cells, even at concentrations as high as 65 μg/ml. The only visible effect of BaH-1 on the cultured cells was a relatively slow, moderate detachment of cells, interpreted as a consequence of proteolytic degradation of extracellular matrix components. In contrast, myotoxin II, a lysine-49 phospholipase A2from the same venom, was clearly cytotoxic to this cell type, albeit being devoid of hemorrhagic activity. These findings suggest that the ability of venom metalloproteinases to induce hemorrhage is not related to a direct cytotoxic action on endothelial cells, and that the rapid degenerative changes of endothelium observed in vivoare probably the result of an indirect mechanism.

As part of the characterization of the host reactivity to the venom ofBothrops asper, we investigated the inflammatory responses in the mouse footpad model. The subcutaneously injected venom induced a rapid increase of serum IL-6 concentration, which peaked between 3 and 6 h and returned to normal values at 12 h. In contrast, serum TNF-a and IL-1a were not detectable at any time point studied. A myotoxic phospholipase A2 isoform purified from this venom, myotoxin II, was also able to induce a systemic IL-6 release when injected into the footpad. Both venom and myotoxin induced local edema and a leukocyte infiltrate accumulating in the muscle and subdermal tissue within 6 h. The infiltrate consisted predominantly of neutrophils at 6 and 24 h, but at later times, mononuclear cells also appeared. The edema, leukocyte infiltration, and IL-6 responses did not depend on the hemorrhagic activity of venom, since all three effects were seen after injection of (1) preneutralized venom, devoid of hemorrhagic activity, and (2) purified myotoxin II. Circulating platelet numbers were significantly decreased 30 min after venom injection and returned to normal after 12 h. The venom also induced a rapid inversion in the ratio of neutrophils to lymphocytes in peripheral blood, which did not normalize until 12 h later. The present observations suggest that venom, besides its cytotoxic properties, induces early hematologic and immunologic alterations. These findings may be of relevance in future treatment modalities.

Brucellosis is a bacterial disease of animals and humans. Brucella abortusbarely activates the innate immune system at the onset of infection, and this bacterium is resistant to the microbicidal action of complement.

Objective. To analyze mortality due to Hymenoptera stings in Costa Rica during 1985-2006. Methods. Records of deaths due to Hymenoptera stings in 1985-2006 were retrieved from Instituto Nacional de Estadística y Censos (National Statistics and Census Institute). Mortality rates were calculated on the basis of national population reports, as of 1 July of each year. Information for each case included age, gender, and the province in which the death occurred. In addition, reports of Hymenoptera sting accidents received by the Centro Nacional de Intoxicaciones (National Poison Center, CNI) in 1995-2006 were obtained to assess exposure to these insects. Results. Over the 22-year period analyzed, 52 fatalities due to Hymenoptera stings were recorded. Annual mortality rates varied from 0-1.73 per 1 million inhabitants, with a mean of 0.74 (95% confidence interval: 0.46-0.93). The majority of deaths occurred in males (88.5%), representing a male to female ratio of 7.7:1. A predominance of fatalities was observed in the elderly (50 years of age and older), as well as in children less than 10 years of age. The province with the highest mortality rate was Guanacaste. The CNI documented 1 591 reports of Hymenoptera stings (mostly by bees) in 1995-2006, resulting in an annual average of 133 cases, with only a slight predominance of males over females (1.4:1). Conclusions. Stings by Hymenoptera, mostly by bees, constitute a frequent occurrence in Costa Rica that can be life-threatening in a small proportion of cases, most often in males and the elderly. The annual number of fatalities fluctuated from 0-6, averaging 2.4 deaths per year. Awareness should be raised not only among the general population, but also among health care personnel that should consider this risk in the clinical management of patients stung by Hymenoptera. [ABSTRACT FROM AUTHOR]