A neutralizing recombinant single chain antibody, scFv, against BaP1, A P-I hemorrhagic metalloproteinase from Bothrops asper snake venom.

BaP1 is a P-I class snake venom metalloproteinase (SVMP) relevant in the local tissue damage associated with envenomings by Bothrops asper, a medically important snake species in Central America and parts of South and North America. The main treatment for these accidents is the passive immunotherapy using antibodies raised in horses. In order to obtain more specific and batch-to-batch consistent antivenons, recombinant antibodies are considered a good option compared to animal immunization. We constructed a recombinant single chain variable fragment (scFv) from a monoclonal antibody against BaP1 (MABaP1) formerly secreted by a hybridoma clone. This recombinant antibody was cloned into pMST3 vector in fusion with SUMO protein and contains VH and VL domains linked by a flexible (G4S)3 polypeptide (scFvBaP1). The aim of this work was to produce scFvBaP1 and to evaluate its potential concerning the neutralization of biologically important activities of BaP1. The cytoplasmic expression of this construct was successfully achieved in C43 (DE3) bacteria. Our results showed that scFvBaP1-SUMO fusion protein presented an electrophoretic band of around 43 kDa from which SUMO alone corresponded to 13.6 kDa, and only the scFv was able to recognize BaP1 as well as the whole venom by ELISA. In contrast, neither an irrelevant scFv anti-LDL nor its MoAb partner recognized it. BaP1-induced fibrinolysis was significantly neutralized by scFvBaP1, but not by SUMO, in a concentration-dependent manner. In addition, scFvBaP1, as well as MaBaP1, completely neutralized in vivo hemorrhage, muscle necrosis, and inflammation induced by the toxin. Docking analyses revealed possible modes of interaction of the recombinant antibody with BaP1. Our data showed that scFv recognized BaP1 and whole B. asper venom, and neutralized biological effects of this SVMP. This scFv antibody can be used for understanding the molecular mechanisms of neutralization of SVMPs, and for exploring the potential of recombinant antibody fragments for improving the neutralization of local tissue damage in snakebite envenoming.

Immunochemical and biological characterization of monoclonal antibodies against BaP1, a metalloproteinase from Bothrops asper snake venom.

BaP1 is a P-I class of Snake Venom Metalloproteinase (SVMP) relevant in the local tissue damage associated with envenomations by Bothrops asper, a medically-important species in Central America and parts of South America. Six monoclonal antibodies (MoAb) against BaP1 (MABaP1) were produced and characterized regarding their isotype, dissociation constant (K(d)), specificity and ability to neutralize BaP1-induced hemorrhagic and proteolytic activity. Two MABaP1 are IgM, three are IgG1 and one is IgG2b. The K(d)s of IgG MoAbs were in the nM range. All IgG MoAbs recognized conformational epitopes of BaP1 and B. asper venom components but failed to recognize venoms from 27 species of Viperidae, Colubridae and Elapidae families. Clone 7 cross-reacted with three P-I SVMPs tested (moojeni protease, insularinase and neuwiedase). BaP1-induced hemorrhage was totally neutralized by clones 3, 6 and 8 but not by clone 7. Inhibition of BaP1 enzymatic activity on a synthetic substrate by MABaP1 was totally achieved by clones 3 and 6, and partially by clone 8, but not by clone 7. In conclusion, these neutralizing MoAbs against BaP1 may become important tools to understand structure-function relationships of BaP1 and the role of P-I class SVMP in snakebite envenomation.

Immunochemical and biological characterization of monoclonalantibodies against BaP1, a metalloproteinase from Bothrops aspersnake venom

BaP1 is a P-I class of Snake Venom Metalloproteinase (SVMP) relevant in the local tissue damage associated with envenomations by Bothrops asper, a medically-important species in Central America and parts of South America. Six monoclonal antibodies (MoAb) against BaP1 (MABaP1) were produced and characterized regarding their isotype, dissociation constant (Kd), specificity and ability to neutralize BaP1-induced hemorrhagic and proteolytic activity. Two MABaP1 are IgM, three are IgG1 and one is IgG2b. The Kds of IgG MoAbs were in the nM range. All IgG MoAbs recognized conformational epitopes of BaP1 and B. asper venom components but failed to recognize venoms from 27 species of Viperidae, Colubridae and Elapidae families. Clone 7 cross-reacted with three P-I SVMPs tested (moojeni protease, insularinase and neuwiedase). BaP1-induced hemorrhage was totally neutralized by clones 3, 6 and 8 but not by clone 7. Inhibition of BaP1 enzymatic activity on a synthetic substrate by MABaP1 was totally achieved by clones 3 and 6, and partially by clone 8, but not by clone 7. In conclusion, these neutralizing MoAbs against BaP1 may become important tools to understand structure–function relationships of BaP1 and the role of P-I class SVMP in snakebite envenomation.

Isolation and characterization of a serine proteinase with thrombin-like activity from the venom of the snake Bothrops asper

A serine proteinase with thrombin-like activity was isolated from the venom of the Central American pit viper Bothrops asper. Isolation was performed by a combination of affinity chromatography on aminobenzamidine-Sepharose and ion-exchange chromatography on DEAE-Sepharose. The enzyme accounts for approximately 0.13 percent of the venom dry weight and has a molecular mass of 32 kDa as determined by SDS-PAGE, and of 27 kDa as determined by MALDI-TOF mass spectrometry. Its partial amino acid sequence shows high identity with snake venom serine proteinases and a complete identity with a cDNA clone previously sequenced from this species. The N-terminal sequence of the enzyme is VIGGDECNINEHRSLVVLFXSSGFL CAGTLVQDEWVLTAANCDSKNFQ. The enzyme induces clotting of plasma (minimum coagulant dose = 4.1 µg) and fibrinogen (minimum coagulant dose = 4.2 µg) in vitro, and promotes defibrin(ogen)ation in vivo (minimum defibrin(ogen)ating dose = 1.0 µg). In addition, when injected intravenously in mice at doses of 5 and 10 µg, it induces a series of behavioral changes, i.e., loss of the righting reflex, opisthotonus, and intermittent rotations over the long axis of the body, which closely resemble the `gyroxin-like' effect induced by other thrombin-like enzymes from snake venoms.

Isolation and characterization of a serine proteinase with thrombin-like activity from the venom of the snake Bothrops asper.

A serine proteinase with thrombin-like activity was isolated from the venom of the Central American pit viper Bothrops asper. Isolation was performed by a combination of affinity chromatography on aminobenzamidine-Sepharose and ion-exchange chromatography on DEAE-Sepharose. The enzyme accounts for approximately 0.13% of the venom dry weight and has a molecular mass of 32 kDa as determined by SDS-PAGE, and of 27 kDa as determined by MALDI-TOF mass spectrometry. Its partial amino acid sequence shows high identity with snake venom serine proteinases and a complete identity with a cDNA clone previously sequenced from this species. The N-terminal sequence of the enzyme is VIGGDECNINEHRSLVVLFXSSGFL CAGTLVQDEWVLTAANCDSKNFQ. The enzyme induces clotting of plasma (minimum coagulant dose = 4.1 microg) and fibrinogen (minimum coagulant dose = 4.2 microg) in vitro, and promotes defibrin(ogen)ation in vivo (minimum defibrin(ogen)ating dose = 1.0 microg). In addition, when injected intravenously in mice at doses of 5 and 10 microg, it induces a series of behavioral changes, i.e., loss of the righting reflex, opisthotonus, and intermittent rotations over the long axis of the body, which closely resemble the ;gyroxin-like' effect induced by other thrombin-like enzymes from snake venoms.

Crystallization and preliminary diffraction data of BaP1, a haemorrhagic metalloproteinase from Bothrops asper snake venom.

BaP1 is a metalloproteinase isolated from the venom of the Central American snake Bothrops asper (terciopelo). It is a 24 kDa protein consisting of a single chain which includes the metalloproteinase domain only, therefore being classified as a class P-I snake-venom metalloproteinase. BaP1 induces prominent local tissue damage, such as haemorrhage, myonecrosis, blistering, dermonecrosis and oedema. In order to elucidate its structure, BaP1 was crystallized by the hanging-drop vapour-diffusion technique in 0.1 M bicine pH 9.0, 10% PEG 20 000 and 2%(v/v) dioxane. Diffraction data were observed to a resolution of 2.7 A. Crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 38.22, b = 60.17, c = 86.09 A.

Inhibitory properties of the anti-bothropic complex from Didelphis albiventris serum on toxic and pharmacological actions of metalloproteases and myotoxins from Bothrops asper venom.

Anti-bothropic complex (ABC) was isolated from the serum of the South American opossum (Didelphis albiventris) by single-step affinity chromatography using a Sepharose-immobilized metalloprotease (BaP1) from Bothrops asper as the binding protein. Biochemical characterization of ABC showed the presence of two glycosylated subunits of 43 and 45 kDa, respectively, with an isoelectric point < 4. The two subunits were separated by ion-exchange HPLC. The N-terminal sequences of both subunits (LKAMDPTPXLWIETESP, where X is Arg-9 and Pro-9, respectively) showed a high degree of identity with other serum inhibitors isolated from different marsupials. Functional studies pointed out that ABC inhibits the hemorrhagic and proteolytic activities on fibrin, fibrinogen, and casein induced by the metalloproteases BaP1 and BaH4 isolated from B. asper venom. In addition to the anti-hemorrhagic and anti-proteolytic activities, ABC also showed anti-myotoxic, anti-lethal, and anti-edematogenic effects against myotoxic phospholipases A(2) isolated from the same venom. Moreover, it had inhibitory effects on the phospholipase A(2) activity of the crude venom as well as the isolated venom phospholipases A(2).

Neutralization of proteases from Bothrops snake venoms by the aqueous extract from Casearia sylvestris (Flacourtiaceae).

Aqueous extract from Casearia sylvestris leaves, a typical plant from Brazilian open pastures, was able to neutralize the hemorrhagic activity caused by Bothrops asper, Bothrops jararacussu, Bothrops moojeni, Bothrops neuwiedi and Bothrops pirajai venoms. It also neutralized two hemorrhagic metalloproteinases from Bothrops asper venom. Proteolytic activity on casein induced by bothropic venoms and by isolated proteases, including Bn2 metalloproteinase from B. neuwiedi venom, was also inhibited by the C. sylvestris extract in different levels. The alpha-fibrinogen chain was partially protected against degradation caused by B. jararacussu venom, when this venom was incubated with C. sylvestris extract. We also observed that this extract partially increased the time of plasma coagulation caused by B. jararacussu, B. moojeni and B. neuwiedi venoms. C. sylvestris extract did not induce proteolysis in any substrate assayed.

Pathological alterations induced by neuwiedase, a metalloproteinase isolated from Bothrops neuwiedi snake venom.

The pathological alterations induced by neuwiedase, a 22 kDa class P-I metalloproteinase from the venom of the South American pit viper Bothrops neuwiedi, were studied in mice. Neuwiedase was devoid of hemorrhagic activity when tested in the skin up to a dose of 200 microgram, and also after intramuscular injection in the gastrocnemius. However, it induced bleeding when applied onto the mouse cremaster muscle in intravital microscopy experiments, and caused pulmonary hemorrhage when injected intravenously at doses higher than 5 microgram/g. Median lethal dose (LD(50)) by the intravenous route was 5 microgram/g, whereas LD(50) of crude venom was 0.47 microgram/g. After intramuscular injection, neuwiedase induced a mild myotoxic effect, evidenced histologically and by the increment in plasma creatine kinase activity, but it was devoid of hemorrhagic and thrombotic effects. In contrast, crude B. neuwiedi venom induced prominent hemorrhage and myonecrosis in gastrocnemius muscle. Both venom and neuwiedase induced an inflammatory reaction in muscle tissue characterized by abundant polymorphonuclear leukocytes. Moreover, a conspicuous edema developed in the foot pad after subcutaneous injection of neuwiedase. Anti-neuwiedase antibodies produced in rabbits were effective in the neutralization of hemorrhagic activity of crude venom, evidencing immunological cross-reactivity between neuwiedase and other hemorrhagic metalloproteinases present in the venom, and suggesting that metalloproteinases devoid of, or having low, hemorrhagic activity could be good immunogens to generate antibodies effective against high molecular mass metalloproteinasas having potent hemorrhagic activity. It is concluded that neuwiedase, despite its lack of hemorrhagic effect when injected in the gastrocnemius muscle, contributes to local tissue damage by inducing edema, inflammatory infiltrate and mild myotoxicity, and by degrading extracellular matrix components. In addition, large doses of neuwiedase may contribute to pulmonary bleeding

Skeletal muscle necrosis and regeneration after injection of Thalassophryne nattereri (niquim) fish venom in mice.

Stings by Thalassophryne nattereri are responsible for envenomation of fishermen in north-eastern Brazil. Its venom induces prominent local tissue damage, characterized by pain, oedema and necrosis. The pathogenesis of acute muscle damage induced by T. nattereri venom was studied in mice. Intramuscular injection induced myonecrosis within the first hours. Some muscle cells presented a hypercontracted morphology, but most necrotic fibres were not hypercontracted, being instead characterized by a disorganization of myofibrils, with Z line loss, mitochondrial swelling and sarcolemmal disruption. In addition, thrombosis was observed histologically in venules and veins, together with vascular congestion and stasis, evidenced by intravital microscopy. Venom induced a rapid increment in serum creatine kinase (CK) levels, concomitant with a reduction in gastrocnemius muscle CK activity, whereas no increments in muscle lactic acid were detected. A rapid cytolytic effect was induced by the venom on C2C12 murine myoblasts in culture. The inflammatory reaction in affected muscle was characterized by oedema and scarce cellular infiltrate of polymorphonuclear leucocytes and macrophages, with a consequent delay in the removal of necrotic material. Skeletal muscle regeneration was partially impaired, as evidenced by the presence of regenerating fibres of variable size and by the increase of fibrotic tissue in endomysium and perimysium. It is suggested that T. nattereri venom affects muscle fibres by a direct cytotoxic effect, and that the vascular alterations described preclude a successful regenerative process.

Modulation of the susceptibility of human erythrocytes to snake venom myotoxic phospholipases A(2): role of negatively charged phospholipids as potential membrane binding sites.

Cerrophidion (Bothrops) godmani myotoxins I (CGMT-I) and II (CGMT-II), Asp-49 and Lys-49 phospholipases A(2) (PLA2s), which drastically differ in enzymatic activity, were devoid of direct hemolytic effects on erythrocytes (RBC) from different species despite the fact that enzymatically active CGMT-I was able to hydrolyze RBC membrane phospholipids and disrupt liposomes prepared from RBC lipids. Human RBC did not become susceptible to the toxins after treatment with neuraminidase or after altering membrane fluidity with cholesterol or sublytic concentrations of detergent. Unlike normal RBC, significant hemolysis was induced by CGMT-II and another similar Lys-49 isoform, B. asper MT-II (BAMT-II), in RBC enriched with phosphatidylserine (PS). Hemolysis was greater in RBC preincubated with pyridyldithioethylamine (PDA), a potent inhibitor of aminophospholipid transport. RBC enriched with phosphatidic acid (PA) also became susceptible to the myotoxins but was unaffected by PDA. Cells enriched with phosphatidylcholine (PC) remained resistant to the action of the toxins. BAMT-II also induced damage in black lipid membranes prepared with PS but not PC alone. When RBC binding of BAMT-II was measured by enzyme-linked immunosorbent assay, it was observed that PS- and PA-enriched erythrocytes were always able to capture more toxin than normal and PC-enriched RBC. This effect was significantly improved by PDA (in the case of PS) and it was observed either in the presence or in the absence of calcium in the medium. These data suggest that negatively charged lipids in the outer leaflet of cell membranes constitute myotoxic PLA2 binding sites. The scarcity of anionic phospholipids in the outer leaflet of RBC could explain their resistance to the action of these PLA2s.

Characterization of aspercetin, a platelet aggregating component from the venom of the snake Bothrops asper which induces thrombocytopenia and potentiates metalloproteinase-induced hemorrhage.

Thrombocytopenia occurs in a number of patients bitten by Bothrops asper, a species responsible for the majority of snakebites in Central America and southern Mexico. In this work we describe the isolation of a new platelet-aggregating protein, named aspercetin, from the venom of B. asper, which induces thrombocytopenia in mice. Isolation was carried out by a combination of ion-exchange chromatography on DEAE-Sepharose and affinity chromatography on Affi-Gel Blue. Aspercetin is a disulfide-linked heterodimer, with a pI of 4.5 and a molecular mass of 29,759 Da, detemined by MALDI-ESI mass spectrometry. N-terminal sequence shows homology with a number of venom proteins which belong to the C-type lectin family. Aspercetin has functional similarities with botrocetin, from B. jararaca venom, since it induces platelet aggregation only in the presence of plasma or purified von Willebrand factor. Aspercetin-mediated platelet aggregation results from the interaction of von Willebrand factor with platelet receptor GPIb. Aspercetin lacks anticoagulant effect and does not agglutinate erythrocytes, in contrast with other representatives of the C-type lectin family isolated from snake venoms. Moreover, aspercetin is not lethal, nor does it induce myonecrosis, hemorrhage and edema. When injected intravenously or intramuscularly in mice it induces a rapid, dose-dependent drop in platelet counts and prolongs the bleeding time, suggesting that it may play a role in the thrombocytopenia that develops in a number of B. asper envenomations. Moreover, mice injected intravenously with aspercetin and then receiving an intradermal injection of B. asper hemorrhagic metalloproteinase BaP1 develop a larger hemorrhagic lesion than mice receiving only BaP1. This suggests that aspercetin, by reducing platelet numbers, may