A novel high molecular weight fibrinogenase from the venom of Bitis arietans

A case of fatal envenomation by a captive puff adder (Bitis arietans) in Malaysia

The Puff Adder (Bitis arietans) is a viper native to Africa and the Middle East. Envenomation by this species often requires the administration of appropriate antivenom in order to achieve a favorable outcome. A patient was bitten in both hands by a captive B. arietans presented to a teaching hospital in Malaysia. The patient developed painful progressive swelling on both limbs that extended to the chest, hypotension, hypokalemia with worsening anemia, thrombocytopenia, coagulopathy, and severe metabolic acidosis. The patient was managed supportively while waiting for the appropriate antivenom, Antivipmyn-Africa, from the Singapore Zoo. The patient developed cardiorespiratory arrest twice and did not recover from the second. The patient was pronounced dead 23 hours post-incident. The local unavailability of the appropriate antivenom may be the most important factor that contributed to the patient's death. There is also a need to amend the Malaysian Wildlife Act in order to prevent such cases from recurring.

Bioactive Molecules Derived from Snake Venoms with Therapeutic Potential for the Treatment of Thrombo-Cardiovascular Disorders Associated with COVID-19

As expected, several new variants of Severe Acute Respiratory Syndrome-CoronaVirus-2 (SARS-CoV-2) emerged and have been detected around the world throughout this Coronavirus Disease of 2019 (COVID-19) pandemic. Currently, there is no specific developed drug against COVID-19 and the challenge of developing effective antiviral strategies based on natural agents with different mechanisms of action becomes an urgent need and requires identification of genetic differences among variants. Such data is used to improve therapeutics to combat SARS-CoV-2 variants. Nature is known to offer many biotherapeutics from animal venoms, algae and plant that have been historically used in traditional medicine. Among these bioresources, snake venom displays many bioactivities of interest such as antiviral, antiplatelet, antithrombotic, anti-inflammatory, antimicrobial and antitumoral. COVID-19 is a viral respiratory sickness due to SARS-CoV-2 which induces thrombotic disorders due to cytokine storm, platelet hyperactivation and endothelial dysfunction. This review aims to: (1) present an overview on the infection, the developed thrombo-inflammatory responses and mechanisms of induced thrombosis of COVID-19 compared to other similar pathogenesis; (2) underline the role of natural compounds such as anticoagulant, antiplatelet and thrombolytic agents; (3) investigate the management of coagulopathy related to COVID-19 and provide insight on therapeutic such as venom compounds. We also summarize the updated advances on antiviral proteins and peptides derived from snake venoms that could weaken coagulopathy characterizing COVID-19.

Mechanisms Responsible for the Anticoagulant Properties of Neurotoxic Dendroaspis Venoms: A Viscoelastic Analysis

Using thrombelastography to gain mechanistic insights, recent investigations have identified enzymes and compounds in Naja and Crotalus species' neurotoxic venoms that are anticoagulant in nature. The neurotoxic venoms of the four extant species of Dendroaspis (the Black and green mambas) were noted to be anticoagulant in nature in human blood, but the mechanisms underlying these observations have never been explored. The venom proteomes of these venoms are unique, primarily composed of three finger toxins (3-FTx), Kunitz-type serine protease inhibitors (Kunitz-type SPI) and <7% metalloproteinases. The anticoagulant potency of the four mamba venoms available were determined in human plasma via thrombelastography; vulnerability to inhibition of anticoagulant activity to ethylenediaminetetraacetic acid (EDTA) was assessed, and inhibition of anticoagulant activity after exposure to a ruthenium (Ru)-based carbon monoxide releasing molecule (CORM-2) was quantified. Black mamba venom was the least potent by more than two orders of magnitude compared to the green mamba venoms tested; further, Black Mamba venom anticoagulant activity was not inhibited by either EDTA or CORM-2. In contrast, the anticoagulant activities of the green mamba venoms were all inhibited by EDTA to a greater or lesser extent, and all had anticoagulation inhibited with CORM-2. Critically, CORM-2-mediated inhibition was independent of carbon monoxide release, but was dependent on a putative Ru-based species formed from CORM-2. In conclusion, there was great species-specific variation in potency and mechanism(s) responsible for the anticoagulant activity of Dendroaspis venom, with perhaps all three protein classes-3-FTx, Kunitz-type SPI and metalloproteinases-playing a role in the venoms characterized.

[Recurrent retroperitoneal hematoma due to viperine envenomation: case study]

Les envenimations ophidiennes constituent un problème de santé publique en Afrique, entrainant 20 000 décès annuels. Cette mortalité traduit les difficultés de prise en charge des complications en particuliers hémorragiques. Nous rapportons le cas de Mr SL 35 ans, agriculteur, victime d'une morsure de vipère entrainant un syndrome hémorragique, suivi d'un abdomen aigu d'installation progressive. L'échographie objectivait un épanchement de grande abondance, dont la ponction ramenait du sang incoagulable. Devant la reconstitution de l'hémopéritoine après trois doses de sérum antivenimeux et la coagulation des prélèvements sur tube sec, une laparotomie exploratrice était réalisée à J9. Elle a retrouvé un hématome retro péritonéal bombant dans le méso-colon et qui s'écoulait dans la cavité péritonéale. Le geste a consisté à une évacuation de 1500ml de sang, et un toilettage au sérum physiologique. Les suites opératoires ont été simples. Le patient était transféré en secteur d'hospitalisation de chirurgie à J3 post opératoire puis sortie d'hôpital à J19.

Kn-Ba: a novel serine protease isolated from Bitis arietans snake venom with fibrinogenolytic and kinin-releasing activities

Background

Bitis arietans is a venomous snake found in sub-Saharan Africa and in parts of Morocco and Saudi Arabia. The envenomation is characterized by local and systemic reactions including pain, blistering, edema and tissue damage, besides hemostatic and cardiovascular disturbances, which can cause death or permanent disabilities in its victims. However, the action mechanisms that provoke these effects remain poorly understood, especially the activities of purified venom components. Therefore, in order to elucidate the molecular mechanisms that make the Bitis arietans venom so potent and harmful to human beings, this study reports the isolation and biochemical characterization of a snake venom serine protease (SVSP).

Methods

Solubilized venom was fractionated by molecular exclusion chromatography and the proteolytic activity was determined using fluorescent substrates. The peaks that showed serine protease activity were determined by blocking the proteolytic activity with site-directed inhibitors. In sequence, the fraction of interest was submitted to another cycle of molecular exclusion chromatography. The purified serine protease was identified by mass spectrometry and characterized biochemically and immunochemically.

Results

A serine protease of 33 kDa with fibrinogen-degrading and kinin-releasing activities was isolated, described, and designated herein as Kn-Ba. The experimental Butantan Institute antivenom produced against Bitis arietans venom inhibited the Kn-Ba activity.

Conclusions

The in vitro activities of Kn-Ba can be correlated with the capacity of the venom to provoke bleeding and clotting disorders as well as hypotension, which are common symptoms presented by envenomed victims. Obtaining satisfactory Kn-Ba inhibition through the experimental antivenom is important, given the WHO’s recommendation of immunotherapy in cases of human accidents with venomous snakes.

Electronic supplementary material

The online version of this article (10.1186/s40409-018-0176-5) contains supplementary material, which is available to authorized users.

The effect of physiological levels of South African puff adder (Bitis arietans) snake venom on blood cells: an in vitro model

A significant burden of illness is caused globally by snakebites particularly by the puff adder, Bitis arietans. Presently there is no reliable and rapid method to confirm envenomation on blood chemistry; although coagulation parameters like prothrombin time, partial thromboplastin time, international normalized ratio and also serum electrolytes are tested. Here, we found that direct in vitro exposure of physiological relevant whole venom levels to human healthy blood (N = 32), caused significant physiological changes to platelet activity using a hematology analyzer, and measuring occlusion time, as well as lyses time, with the global thrombosis test (GTT). Disintegrated platelets were confirmed by scanning electron microscopy (SEM). We also confirmed the pathologic effects on erythrocytes (RBCs) (visible as eryptotic RBCs), by looking at both light microscopy and SEM. Thromboelastography showed that no clot formation in whole blood could be induced after addition of whole venom. We propose further clinical studies to investigate the use of light microscopy smears and hematology analyzer results immediately after envenomation, as a possible first-stage of clinical confirmation of envenomation.

Decreased snake venom metalloproteinase effects via inhibition of enzyme and modification of fibrinogen

Since the introduction of antivenom administration 120 years ago to treat venomous snake bit, it has been the gold standard for saving life and limb. However, this therapeutic approach is not always effective and not without potential life-threatening side effects. We tested a new paradigm to abrogate the plasmatic anticoagulant effects of fibrinogenolytic snake venom metalloproteinases by modification of fibrinogen with iron and carbon monoxide and by inhibiting these Zn(2+) dependent metalloproteinases directly with carbon monoxide exposure. Assessment of the fibrinogenolytic effects of venoms collected from Puff adder, Gaboon viper and Indian cobra snakes on plasmatic coagulation kinetics was performed with thrombelastography. Pretreatment of plasma with iron and carbon monoxide exposure markedly attenuated the effects of all three venoms, and direct pretreatment of each venom with carbon monoxide also significantly decreased the ability to compromise coagulation. These results demonstrated that the introduction of a transition metal (e.g., modulation of the α-chain of fibrinogen with iron), modulation of transition metal in heme (e.g., carbon monoxide modulation of fibrinogen-bound heme iron), and direct inhibition of transition metal containing venom enzymes (e.g., CO binding to Zn(2+) or displacing Zn(2+) from the catalytic site) significantly decreased fibrinogenolytic activity. This biometal modulation strategy to attenuate the anticoagulant effects of snake venom metalloproteinases could potentially diminish hemostatic injury in envenomed patients until antivenom can be administered.

New proline-rich oligopeptides from the venom of African adders: Insights into the hypotensive effect of the venoms

BACKGROUND

The snakes from the Bitis genus are some of the most medically important venomous snakes in sub Saharan Africa, however little is known about the composition and effects of these snake venom peptides. Considering that the victims with Bitis genus snakes have exacerbate hypotension and cardiovascular disorders, we investigated here the presence of angiotensin-converting enzyme modulators on four different species of venoms.

METHODS

The peptide fractions from Bitis gabonica gabonica, Bitis nasicornis, Bitis gabonica rhinoceros and Bitis arietans which showed inhibitory activity on angiotensin-converting enzyme were subjected to mass spectrometry analysis. Eight proline-rich peptides were synthetized and their potencies were evaluated in vitro and in vivo.

RESULTS

The MS analysis resulted in over 150 sequences, out of which 32 are new proline-rich oligopeptides, and eight were selected for syntheses. For some peptides, inhibition assays showed inhibitory potentials of cleavage of angiotensin I ten times greater when compared to bradykinin. In vivo tests showed that all peptides decreased mean arterial pressure, followed by tachycardia in 6 out of 8 of the tests.

CONCLUSION

We describe here some new and already known proline-rich peptides, also known as bradykinin-potentiating peptides. Four synthetic peptides indicated a preferential inhibition of angiotensin-converting enzyme C-domain. In vivo studies show that the proline-rich oligopeptides are hypotensive molecules.

GENERAL SIGNIFICANCE

Although proline-rich oligopeptides are known molecules, we present here 32 new sequences that are inhibitors of the angiotensin-converting enzyme and consistent with the symptoms of the victims of Bitis spp, who display severe hypotension.

African adders: partial characterization of snake venoms from three Bitis species of medical importance and their neutralization by experimental equine antivenoms

BACKGROUND

An alarming number of fatal accidents involving snakes are annually reported in Africa and most of the victims suffer from permanent local tissue damage and chronic disabilities. Envenomation by snakes belonging to the genus Bitis, Viperidae family, are common in Sub-Saharan Africa. The accidents are severe and the victims often have a poor prognosis due to the lack of effective specific therapies. In this study we have biochemically characterized venoms from three different species of Bitis, i.e., Bitis arietans, Bitis gabonica rhinoceros and Bitis nasicornis, involved in the majority of the human accidents in Africa, and analyzed the in vitro neutralizing ability of two experimental antivenoms.

METHODOLOGY/PRINCIPAL FINDINGS

The data indicate that all venoms presented phospholipase, hyaluronidase and fibrinogenolytic activities and cleaved efficiently the FRET substrate Abz-RPPGFSPFRQ-EDDnp and angiotensin I, generating angiotensin 1-7. Gelatinolytic activity was only observed in the venoms of B. arietans and B. nasicornis. The treatment of the venoms with protease inhibitors indicated that Bitis venoms possess metallo and serinoproteases enzymes, which may be involved in the different biological activities here evaluated. Experimental antivenoms produced against B. arietans venom or Bitis g. rhinoceros plus B. nasicornis venoms cross-reacted with the venoms from the three species and blocked, in different degrees, all the enzymatic activities in which they were tested.

CONCLUSION

These results suggest that the venoms of the three Bitis species, involved in accidents with humans in the Sub-Saharan Africa, contain a mixture of various enzymes that may act in the generation and development of some of the clinical manifestations of the envenomations. We also demonstrated that horse antivenoms produced against B. arietans or B. g. rhinoceros plus B. nasicornis venoms can blocked some of the toxic activities of these venoms.

Current treatment for venom-induced consumption coagulopathy resulting from snakebite

Venomous snakebite is considered the single most important cause of human injury from venomous animals worldwide. Coagulopathy is one of the commonest important systemic clinical syndromes and can be complicated by serious and life-threatening haemorrhage. Venom-induced consumption coagulopathy (VICC) is the commonest coagulopathy resulting from snakebite and occurs in envenoming by Viperid snakes, certain elapids, including Australian elapids, and a few Colubrid (rear fang) snakes. Procoagulant toxins activate the clotting pathway, causing a broad range of factor deficiencies depending on the particular procoagulant toxin in the snake venom. Diagnosis and monitoring of coagulopathy is problematic, particularly in resource-poor countries where further research is required to develop more reliable, cheap clotting tests. MEDLINE and EMBASE up to September 2013 were searched to identify clinical studies of snake envenoming with VICC. The UniPort database was searched for coagulant snake toxins. Despite preclinical studies demonstrating antivenom binding toxins (efficacy), there was less evidence to support clinical effectiveness of antivenom for VICC. There were no placebo-controlled trials of antivenom for VICC. There were 25 randomised comparative trials of antivenom for VICC, which compared two different antivenoms (ten studies), three different antivenoms (four), two or three different doses or repeat doses of antivenom (five), heparin treatment and antivenom (five), and intravenous immunoglobulin treatment and antivenom (one). There were 13 studies that compared two groups in which there was no randomisation, including studies with historical controls. There have been numerous observational studies of antivenom in VICC but with no comparison group. Most of the controlled trials were small, did not use the same method for assessing coagulopathy, varied the dose of antivenom, and did not provide complete details of the study design (primary outcomes, randomisation, and allocation concealment). Non-randomised trials including comparison groups without antivenom showed that antivenom was effective for some snakes (e.g., Echis), but not others (e.g., Australasian elapids). Antivenom is the major treatment for VICC, but there is currently little high-quality evidence to support effectiveness. Antivenom is not risk free, and adverse reactions can be quite common and potentially severe. Studies of heparin did not demonstrate it improved outcomes in VICC. Fresh frozen plasma appeared to speed the recovery of coagulopathy and should be considered in bleeding patients.

In vitro toxic effects of puff adder (Bitis arietans) venom, and their neutralization by antivenom

This study investigated the in vitro toxic effects of Bitis arietans venom and the ability of antivenom produced by the South African Institute of Medical Research (SAIMR) to neutralize these effects. The venom (50 µg/mL) reduced nerve-mediated twitches of the chick biventer muscle to 19% ± 2% of initial magnitude (n = 4) within 2 h. This inhibitory effect of the venom was significantly attenuated by prior incubation of tissues with SAIMR antivenom (0.864 µg/µL; 67% ± 4%; P < 0.05; n = 3–5, unpaired t-test). Addition of antivenom at t₅₀ failed to prevent further inhibition or reverse the inhibition of twitches and responses to agonists. The myotoxic action of the venom (50 µg/mL) was evidenced by a decrease in direct twitches (30% ± 6% of the initial twitch magnitude) and increase in baseline tension (by 0.7 ± 0.3 g within 3 h) of the chick biventer. Antivenom failed to block these effects. Antivenom however prevented the venom induced cytotoxic effects on L6 skeletal muscle cells. Venom induced a marginal but significant reduction in plasma clotting times at concentrations above 7.8 µg/100 µL of plasma, indicating poor procoagulant effects. In addition, the results of western immunoblotting indicate strong immunoreactivity with venom proteins, thus warranting further detailed studies on the neutralization of the effects of individual venom toxins by antivenom.

A novel 25 kDa protein from the venom of Bitis arietans with similarity to C-type lectins causes fibrinogen-dependent platelet agglutination

Snake venoms affect blood coagulation and platelet functions in various ways. Venom from the Viperidae and Crotalidae family of snakes contains biologically active proteins that possess coagulant and anticoagulant activities, as well as platelet aggregating and inhibitory activities. Many of these proteins belong to the C-type lectin family. C-type lectins from viper venoms can act by prohibiting the interaction between platelet receptors, such as GPIIbIIIa and the GPIb/V/IX complex, and their ligands. We report on the purification of a novel 25 kDa protein, Ba25, from Bitis arietans with a primary structure that possesses similarity to other C-type lectins from viper venom. This protein has a profound effect on the clotting of whole blood, as well as being able to cause agglutination of platelets in platelet rich plasma without degranulation of the cells, but not of washed platelets in the absence of fibrinogen. Ba25 interacts with the platelet via the GPIb/V/IX, as well as the GPIIbIIIa receptor, and causes an increase in binding of fibrinogen to platelets. These results suggest that Ba25 may be a potent mediator of platelet-platelet interactions, and other coagulatory mechanisms.

Severe puff adder (Bitis arietans) envenomation with coagulopathy

BACKGROUND

The puff adder (Bitis arietans) is a highly toxic venomous snake that is responsible for a large proportion of the venomous snakebites in sub-Saharan Africa, where it is indigenous. Puff adder bites in North America result from snakes in captivity. Although thrombolytic enzymes are present in puff adder venom, significant coagulopathy has not been previously reported with a confirmed puff adder envenomation.

RESULTS

We report a serious puff adder envenomation to the finger, characterized by severe swelling, local tissue necrosis, hypotension, thrombocytopenia, severe coagulopathy, and hemorrhage. Fifteen vials of South Africa polyvalent antivenom were administered, beginning 4.5 hours post-envenomation, with step-wise improvement in hematological abnormalities. Other treatments included vasopressors, ventilatory support, leeches, transfusion, and eventual digit amputation. After a prolonged hospital course, the patient had a good outcome.

CONCLUSIONS

Puff adder envenomation causes tissue necrosis, hypotension, coagulopathy, thrombocytopenia, and spontaneous bleeding. Severe coagulopathy may occur. Physicians treating severe cases should be prepared to administer at least 15 vials of antivenom if needed.

A novel nonhemorragic protease from the African puff adder (Bitis arietans) venom

A nonhemorrhagic proteinase B-20 from the venom of Bitis arietans has been purified to apparent electrophoretic homogeneity by chromatography on Sephadex G-100, Q-Sepharose, and CM-cellulose. It has a molecular weight of 20 k Da as determined by size exclusion chromatography on Sephadex G-100 and migrated as a single 20-k Da band on SDS polyacrylamide. It has an optimum pH of 6-8 and is inactive at pH 4.0. EDTA and 1,10-phenanthroline strongly inhibited the enzyme suggesting it is a metalloenzyme. Also it is inhibited by antipain but is unaffected by trasylol, antitrypsin, and pepsptatin. Colombin, an identified active component of Aristolochia albida used in the treatment of snake poisoning, did not inhibit the protease activity. It lost over 90% of its activity in the presence of 0.5 microM Hg(2+) but the inhibition was completely blocked in the presence of 10 microM mercaptoethanol implicating sulfhydryl groups in the catalytic entity of the protein. The activity was also inhibited competitively by glutathione and cysteine with inhibition binding constants K(i) of 240 and 40 microM, respectively. The enzyme is unaffected by several divalent cations but activated by 1 mM Fe(3+). It had a prolyl endopeptidase and thermolysin-like activity. The enzyme displayed a fast acting alpha-fibrinolytic and delayed gamma-fibrinolytic activity when tested on human fibrinogen. The relevance of these findings is discussed.