Exploring the venom proteome of the African puff adder, Bitis arietans, using a combinatorial peptide ligand library approach at different pHs

Venom variation among the three subspecies of the North African mountain viper Vipera monticola Saint Girons 1953

The North African mountain viper (Vipera monticola) is a medically relevant venomous snake distributed in Morocco, Algeria, and Tunisia. Three subspecies of V. monticola, exhibiting differences in morphotypes and dietary regimes, are currently recognised: V. m. monticola, V. m. atlantica, and V. m. saintgironsi. Through the application of snake venomics, we analysed the venoms of specimens of Moroccan origin belonging to each of the three subspecies. Snake venom metalloproteinases (svMP), snake venom serine proteases (svSP), C-type lectin and C-type lectin-related proteins (CTL), and phospholipases A2 (PLA2) were predominant, with PLA2 being the most abundant toxin family overall. Disintegrins (DI) and cysteine-rich secretory proteins (CRISP) were exclusive to V. m. monticola and V. m. atlantica, while l-amino-acid oxidases (LAAO) were only found in V. m. saintgironsi. The differences detected in the venom profiles, as well as in presence/absence and relative abundances of toxin families, indicate the occurrence of intraspecific venom variation within V. monticola. The identified patterns of venom similarity between subspecies seem to align more with their phylogenetic relationships than with the reported differences in their feeding habits.

Comparing Traditional and Toxin-Oriented Approaches towards Antivenom Production against Bitis arietans Snake Venom

Accidents with snakes are responsible for about 32,000 deaths annually in sub-Saharan Africa, caused mostly by snakes from the genus Bitis, in particular Bitis arietans. B. arietans venom is composed of a complex mixture of toxins, mainly metalloproteases, serine proteases, phospholipases, lectins, and disintegrins. In this work, we compared two approaches to anti-B. arietans antivenom production: immunization with crude snake venom ("traditional approach") and immunization with selected key toxins isolated from the snake venom ("toxin oriented" approach). Fractions from B. arietans venom were isolated by size exclusion chromatography. Crude venom and samples containing serine proteases or metalloproteases were selected for the immunization of BALB/c mice. Anti-B. arietans and anti-serine proteases plasmas showed a similar recognition profile and higher titers and affinity than the anti-metalloproteases plasma. Cross-recognition of other Bitis venoms was observed, but with low intensity. Although the plasma of all experimental groups inhibited the enzymatic activity of B. arietans venom in vitro, in vivo protection was not achieved. Our results have shown limitations in both approaches considered. Based on this, we proposed a model of polyclonal, species-specific, monovalent antivenoms that could be used as a base to produce customizable polyvalent sera for use in sub-Saharan Africa.

Inhibition of bacterial biofilms by the snake venom proteome

Snake venoms possess a range of pharmacological and toxicological activities. Here we evaluated the antibacterial and anti-biofilm activity against methicillin-susceptible and methicillin-resistant Staphylococcus aureus (MSSA and MRSA) of venoms from the Samar spitting cobra Naja samarensis and the Puff adder Bitis arietans. Both venoms prevented biofilm production by pathogenic S. aureus in a growth-independent manner, with the B. arietans venom being most potent. Fractionation showed the active molecule to be heat-labile and >10 kDa in size. Proteomic profiles of N. samarensis venom revealed neurotoxins and cytotoxins, as well as an abundance of serine proteases and three-finger toxins, while serine proteases, metalloproteinases and C-lectin types were abundant in B. arietans venom. These enzymes may have evolved to prevent bacteria colonising the snake venom gland. From a biomedical biotechnology perspective, they have valuable potential for anti-virulence therapy to fight antibiotic resistant microbes.

Anti-Metalloproteases: Production and Characterization of Polyclonal IgG Anti-F2 Fraction Antibodies Purified from the Venom of the Snake Bitis arietans

Bitis arietans is a medically important snake found in Sub-Saharan Africa. The envenomation is characterized by local and systemic effects, and the lack of antivenoms aggravates the treatment. This study aimed to identify venom toxins and develop antitoxins. The F2 fraction obtained from Bitis arietans venom (BaV) demonstrated the presence of several proteins in its composition, including metalloproteases. Titration assays carried out together with the immunization of mice demonstrated the development of anti-F2 fraction antibodies by the animals. The determination of the affinity of antibodies against different Bitis venoms was evaluated, revealing that only BaV had peptides recognized by anti-F2 fraction antibodies. In vivo analyses demonstrated the hemorrhagic capacity of the venom and the effectiveness of the antibodies in inhibiting up to 80% of the hemorrhage and 0% of the lethality caused by BaV. Together, the data indicate: (1) the prevalence of proteins that influence hemostasis and envenomation; (2) the effectiveness of antibodies in inhibiting specific activities of BaV; and (3) isolation and characterization of toxins can become crucial steps in the development of new alternative treatments. Thus, the results obtained help in understanding the envenoming mechanism and may be useful for the study of new complementary therapies.

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.

Antibodies as Snakebite Antivenoms: Past and Future

Snakebite envenomation is considered a neglected tropical disease, affecting tens of thousands of people each year. The recommended treatment is the use of antivenom, which is composed of immunoglobulins or immunoglobulin fragments obtained from the plasma of animals hyperimmunized with one (monospecific) or several (polyspecific) venoms. In this review, the efforts made in the improvement of the already available antivenoms and the development of new antivenoms, focusing on snakes of medical importance from sub-Saharan Africa and Latin America, are described. Some antivenoms currently used are composed of whole IgGs, whereas others use F(ab')2 fragments. The classic methods of attaining snake antivenoms are presented, in addition to new strategies to improve their effectiveness. Punctual changes in immunization protocols, in addition to the use of cross-reactivity between venoms from different snakes for the manufacture of more potent and widely used antivenoms, are presented. It is known that venoms are a complex mixture of components; however, advances in the field of antivenoms have shown that there are key toxins that, if effectively blocked, are capable of reversing the condition of in vivo envenomation. These studies provide an opportunity for the use of monoclonal antibodies in the development of new-generation antivenoms. Thus, monoclonal antibodies and their fragments are described as a possible alternative for the production of antivenoms, regardless of the venom. This review also highlights the challenges associated with their development.

Bitis arietans Snake Venom and Kn-Ba, a Snake Venom Serine Protease, Induce the Production of Inflammatory Mediators in THP-1 Macrophages

Bitis arietans is a snake of medical importance found throughout sub-Saharan Africa and in savannas and pastures of Morocco and western Arabia. The effects of its venom are characterized by local and systemic alterations, such as inflammation and cardiovascular and hemostatic disturbances, which can lead to victims' death or permanent disability. To better characterize the inflammatory process induced by this snake's venom, the participation of eicosanoids and PAF (platelet- activating factor) in this response were demonstrated in a previous study. In addition, edema and early increased vascular permeability followed by an accumulation of polymorphonuclear (PMN) cells in the peritoneal cavity were accompanied by the production of the eicosanoids LTB₄, LTC₄, TXB₂, and PGE₂, and local and systemic production of IL-6 and MCP-1. In this context, the present study focused on the identification of inflammatory mediators produced by human macrophages derived from THP-1 cells in response to Bitis arietans venom (BaV), and Kn-Ba, a serine protease purified from this venom. Here, we show that Kn-Ba, and even the less intensive BaV, induced the production of the cytokine TNF and the chemokines RANTES and IL-8. Only Kn-Ba was able to induce the production of IL-6, MCP-1, and IP-10, whereas PGE₂ was produced only in response to BaV. Finally, the release of IL-1β in culture supernatants suggests the activation of the inflammasomes by the venom of Bitis arietans and by Kn-Ba, which will be investigated in more detail in future studies.

Exploring the five-paced viper (Deinagkistrodon acutus) venom proteome by integrating a combinatorial peptide ligand library approach with shotgun LC-MS/MS

BACKGROUND

Snake venoms are complex mixtures of toxic proteins or peptides encoded by various gene families that function synergistically to incapacitate prey. In the present study, in order to unravel the proteomic repertoire of Deinagkistrodon acutus venom, some trace abundance components were analyzed.

METHODS

Shotgun proteomic approach combined with shotgun nano-LC-ESI-MS/MS were employed to characterize the medically important D. acutus venom, after collected samples were enriched with the combinatorial peptide ligand library (CPLL).

RESULTS

This avenue helped us find some trace components, undetected before, in D. acutus venom. The results indicated that D. acutus venom comprised 84 distinct proteins from 10 toxin families and 12 other proteins. These results are more than twice the number of venom components obtained from previous studies, which were only 29 distinct proteins obtained through RP-HPLC for the venom of the same species. The present results indicated that in D. acutus venom, the most abundant components (66.9%) included metalloproteinases, serine proteinases, and C-type lectin proteins; the medium abundant components (13%) comprised phospholipases A2 (PLA2) and 5'-nucleotidases and nucleases; whereas least abundant components (6%) were aminopeptidases, L-amino acid oxidases (LAAO), neurotoxins and disintegrins; and the trace components. The last were undetected before the use of conventional shotgun proteomics combined with shotgun nano-LC-ESI-MS/MS, such as cysteine-rich secretory proteins Da-CRPa, phospholipases B-like 1, phospholipases B (PLB), nerve growth factors (NGF), glutaminyl-peptide cyclortransferases (QC), and vascular non-inflammatory molecules 2 (VNN2).

CONCLUSION

These findings demonstrated that the CPLL enrichment method worked well in finding the trace toxin proteins in D. acutus venom, in contrast with the previous venomic characterization of D. acutus by conventional LC-MS/MS. In conclusion, this approach combined with the CPLL enrichment was effective for allowing us to explore the hidden D. acutus venomic profile and extended the list of potential venom toxins.

Old World Vipers-A Review about Snake Venom Proteomics of Viperinae and Their Variations

Fine-tuned by millions of years of evolution, snake venoms have frightened but also fascinated humanity and nowadays they constitute potential resources for drug development, therapeutics and antivenoms. The continuous progress of mass spectrometry techniques and latest advances in proteomics workflows enabled toxinologists to decipher venoms by modern omics technologies, so-called ‘venomics’. A tremendous upsurge reporting on snake venom proteomes could be observed. Within this review we focus on the highly venomous and widely distributed subfamily of Viperinae (Serpentes: Viperidae). A detailed public literature database search was performed (2003–2020) and we extensively reviewed all compositional venom studies of the so-called Old-World Vipers. In total, 54 studies resulted in 89 venom proteomes. The Viperinae venoms are dominated by four major, four secondary, six minor and several rare toxin families and peptides, respectively. The multitude of different venomics approaches complicates the comparison of venom composition datasets and therefore we differentiated between non-quantitative and three groups of quantitative workflows. The resulting direct comparisons within these groups show remarkable differences on the intra- and interspecies level across genera with a focus on regional differences. In summary, the present compilation is the first comprehensive up-to-date database on Viperinae venom proteomes and differentiating between analytical methods and workflows.

Interrogating the higher order structures of snake venom proteins using an integrated mass spectrometric approach

Snake venoms contain complex mixtures of proteins vital for the survival of venomous snakes. Aligned with their diverse pharmacological activities, the protein compositions of snake venoms are highly variable, and efforts to characterise the primary structures of such proteins are ongoing. Additionally, a significant knowledge gap exists in terms of the higher-order protein structures which modulate venom potency, posing a challenge for successful therapeutic applications. Here we use a multifaceted mass spectrometry approach to characterise proteins from venoms of Collett's snake Pseudechis colletti and the puff adder Bitis arietans. Following chromatographic fractionation and bottom-up proteomics analysis, native mass spectrometry identified, among other components, a non-covalent l-amino acid oxidase dimer in the P. colletti venom and a C-type lectin tetramer in the B. arietans venom. Furthermore, a covalently-linked phospholipase A₂ (PLA₂) dimer was identified in P. colletti venom, from which the PLA₂ species were shown to adopt compact geometries using ion mobility measurements. Interestingly, we show that the dimeric PLA₂ possesses greater bioactivity than the monomeric PLA₂s. This work contributes to ongoing efforts cataloguing components of snake venoms, and notably, emphasises the importance of understanding higher-order venom protein interactions and the utility of a combined mass spectrometric approach for this task. SIGNIFICANCE: The protein constituents of snake venoms represent a sophisticated cocktail of biologically active molecules ideally suited for further exploration in drug design and development. Despite ongoing efforts to characterise the diverse protein components of such venoms there is still much work required in this area, particularly in moving from simply describing the protein primary sequence to providing an understanding of quaternary structure. The combined proteomic and native mass spectrometry workflow utilised here gives new insights into higher order protein structures in selected snake venoms, and can underpin further investigation into the protein interactions which govern snake venom specificity and potency.

Perspective on the Therapeutics of Anti-Snake Venom

Snakebite envenomation is a life-threatening disease that was recently re-included as a neglected tropical disease (NTD), affecting millions of people in tropical and subtropical areas of the world. Improvement in the therapeutic approaches to envenomation is required to palliate the morbidity and mortality effects of this NTD. The specific therapeutic treatment for this NTD uses snake antivenom immunoglobulins. Unfortunately, access to these vital drugs is limited, principally due to their cost. Different ethnic groups in the affected regions have achieved notable success in treatment for centuries using natural sources, especially plants, to mitigate the effects of snake envenomation. The ethnopharmacological approach is essential to identify the potential metabolites or derivatives needed to treat this important NTD. Here, the authors describe specific therapeutic snakebite envenomation treatments and conduct a review on different strategies to identify the potential agents that can mitigate the effects of the venoms. The study also covers an increased number of literature reports on the ability of natural sources, particularly plants, to treat snakebites, along with their mechanisms, drawbacks and future perspectives.

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.

Evaluation of vasoactivity after haemotoxic snake venom administration

The chick chorioallantoic membrane (CAM) is a widely used model in medical research and fulfils the requirements laid out in the 3 R's. The CAM, contains a dense network of blood vessels, essential for embryo development but also makes the chick embryo an invaluable resource for the study of angiogenesis and the haemotoxicity of substances. Non-neurotoxic snake venom is responsible worldwide for numerous deaths but also has been found to have a vast range of medicinal benefit. This study combines evaluating the time of onset and intensity of effects of three whole viper venoms (Bitis aritans, Crotalus viridis, Agkistrodon contortrix) at varying concentrations. They were applied onto the CAM, using the Luepke grading system as one method of determining their rapid irritation potential. Regarding the principles of 3 R's, this method helps to evaluate the haemotoxic effect of venom as an alternative method to the rodent tests. The information provided from these results can be used as a rapid tool for both medical management of snakebite wounds and the potential use of snake venom in medical treatments. Then, Luepke grading system can help to evaluate the haemotoxic effect of venom in combination with other appropriate methods.

The medical threat of mamba envenoming in sub-Saharan Africa revealed by genus-wide analysis of venom composition, toxicity and antivenomics profiling of available antivenoms

Mambas (genus Dendroaspis) are among the most feared of the medically important elapid snakes found in sub-Saharan Africa, but many facets of their biology, including the diversity of venom composition, remain relatively understudied. Here, we present a reconstruction of mamba phylogeny, alongside genus-wide venom gland transcriptomic and high-resolution top-down venomic analyses. Whereas the green mambas, D. viridis, D. angusticeps, D. j. jamesoni and D. j. kaimosae, express 3FTx-predominant venoms, black mamba (D. polylepis) venom is dominated by dendrotoxins I and K. The divergent terrestrial ecology of D. polylepis compared to the arboreal niche occupied by all other mambas makes it plausible that this major difference in venom composition is due to dietary variation. The pattern of intrageneric venom variability across Dendroaspis represented a valuable opportunity to investigate, in a genus-wide context, the variant toxicity of the venom, and the degree of paraspecific cross-reactivity between antivenoms and mamba venoms. To this end, the immunological profiles of the five mamba venoms were assessed against a panel of commercial antivenoms generated for the sub-Saharan Africa market. This study provides a genus-wide overview of which available antivenoms may be more efficacious in neutralising human envenomings caused by mambas, irrespective of the species responsible. The information gathered in this study lays the foundations for rationalising the notably different potency and pharmacological profiles of Dendroaspis venoms at locus resolution. This understanding will allow selection and design of toxin immunogens with a view to generating a safer and more efficacious pan-specific antivenom against any mamba envenomation.

BIOLOGICAL SIGNIFICANCE

The mambas (genus Dendroaspis) comprise five especially notorious medically important venomous snakes endemic to sub-Saharan Africa. Their highly potent venoms comprise a high diversity of pharmacologically active peptides, including extremely rapid-acting neurotoxins. Previous studies on mamba venoms have focused on the biochemical and pharmacological characterisation of their most relevant toxins to rationalize the common neurological and neuromuscular symptoms of envenomings caused by these species, but there has been little work on overall venom composition or comparisons between them. Only very recently an overview of the composition of the venom of two Dendroaspis species, D. angusticeps and D. polylepis, has been unveiled through venomics approaches. Here we present the first genus-wide transcriptomic-proteomic analysis of mamba venom composition. The transcriptomic analyses described in this paper have contributed 29 (D. polylepis), 23 (D. angusticeps), 40 (D. viridis), 25 (D. j. jamesoni) and 21 (D. j. kaimosae), novel full-length toxin sequences to the non-redundant Dendroaspis sequence database. The mamba genus-wide venomic analysis demonstrated that major D. polylepis venom components are Kunitz-fold family toxins. This feature is unique in relation to the relatively conserved three-finger toxin (3FTx)-dominated venom compositions of the green mambas. Venom variation was interpreted in the context of dietary variation due to the divergent terrestrial ecology of D. polylepis compared to the arboreal niche occupied by all other mambas. Additionally, the degree of cross-reactivity conservation of mamba venoms was assessed by antivenomics against a panel of commercial antivenoms generated for the sub-Saharan Africa market. This study provides a genus-wide overview to infer which available antivenoms may be capable of neutralising human envenomings caused by mambas, irrespective of the species responsible. The information gathered in this study lays the foundations for rationalising the pharmacological profiles of mamba venoms at locus resolution. This understanding will contribute to the generation of a safer and more efficacious pan-Dendroaspis therapeutic antivenom against any mamba envenomation.

Isolation and biochemical characterization of bradykinin-potentiating peptides from Bitis gabonica rhinoceros

Background

Venoms represent a still underexplored reservoir of bioactive components that might mitigate or cure diseases in conditions in which conventional therapy is ineffective. The bradykinin-potentiating peptides (BPPs) comprise a class of angiotensin-I converting enzyme (ACE) inhibitors. The BPPs usually consist of oligopeptides with 5 to 13 residues with a high number of proline residues and the tripeptide Ile-Pro-Pro (IPP-tripeptide) in the C-terminus region and have a conserved N-terminal pyroglutamate residue. As a whole, the action of the BPPs on prey and snakebite victims results in the decrease of the blood pressure. The aim of this work was to isolate and characterize novel BPPs from the venom of Bitis gabonica rhinoceros.

Methods

The crude venom of B. g. rhinoceros was fractionated by size exclusion chromatography and the peptide fraction (<7 kDa) was separated by reverse phase chromatography (RP-HPLC) and analyzed by ESI-IT-TOF-MS/MS. One new BPP was identified, synthetized and assayed for ACE inhibition and, in vivo, for edema potentiation.

Results

Typical BPP signatures were identified in three RP-HPLC fractions. CID fragmentation presented the usual y-ion of the terminal P-P fragment as a predominant signal at m/z 213.1. De novo peptide sequencing identified one Bothrops-like BPP and one new BPP sequence. The new BPP was synthesized and showed poor inhibition over ACE, but displayed significant bradykinin-induced edema potentiation.

Conclusions

So far, few BPPs are described in Viperinae, and based on the sequenced peptides, two non-canonical sequences were detected. The possible clinical role of this new peptides remains unclear.

Development of IgY antibodies against anti-snake toxins endowed with highly lethal neutralizing activity

Snakebite envenoming is a major neglected disease related to poverty in developing countries. Treatment involves the administration of a specific antivenom serum and auxiliary therapies, if necessary. The improvement of antibodies is of great importance for the technological advancement of antivenom therapy and to reduce the morbidity and mortality associated with this medical burden. In the present study, adult hens were immunized nine times with 20μg of B. arietans or C. d. terrificus venoms at three-week intervals between immunizations. Developing antibodies presented increasing avidity and affinity to antigenic toxin epitopes along immunization, attaining a plateau after the seventh immunization. Pooled egg yolk-purified IgY antivenom antibodies, subjected to in vitro-in vivo lethality assay using Swiss adult mice, exhibited potent venom lethal neutralizing activity. Taken together, chickens under the described immunization schedule were considered alternative candidates for antivenom production. Lower maintenance costs, a simple antibody manufacturing process and immunization suffering restrictions are additional advantages.

Hyphenated LC-MALDI-ToF/ToF and LC-ESI-QToF approach in proteomic characterization of honeybee venom

To increase in the depth characterization of venom proteome of Apis mellifera the hyphenated LC-MALDI-ToF/ToF-MS (liquid chromatography-matrix-assisted laser desorption/ionization-time of flight/time of flight tandem mass spectrometry) and LC-ESI-QToF-MS (liquid chromatography-electrospray ionization-quadrupole time of flight tandem mass spectrometry) techniques combined with combinatorial peptide ligand library enrichment method is proposed in this study. The novel approach simplifies pretreatment protocol in venom investigation. By using the protein preparation kit with sequential multi-step elution, the honeybee venom was dispensed into four different fractions. In total 269 proteins were detected, among these 49 honeybee toxins, allergens and components involved in mechanism of envenoming belonging to venom enzyme classes of esterases, proteases/peptidases, protease inhibitors, hydrolases and major royal jelly proteins. Moreover 5 additional putative toxins were identified. Their role in envenoming process was discussed. We concluded that different mass spectrometry techniques increased the detection of the honeybee venom proteins, underscoring the complementary character of analytical methods. The combination of MALDI and ESI ionization has resulted in numerous proteins identifications, not possible to reach with single proteomic technique. The study will contribute to broadening the knowledge about the complexity of honeybee venom. The newly identified proteins may serve not only as toxins and allergens, but also as substances with potential pharmacological activity. Although, the most detected proteins belong to trace elements of honeybee venom without toxic activity or action on vital system of victims, they should be taken into account in characterization of living organism response on Apis mellifera sting.

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.

Exploring the hidden honeybee (Apis mellifera) venom proteome by integrating a combinatorial peptide ligand library approach with FTMS

At present, 30 compounds have been described in the venom of the honeybee, and 16 of them were confirmed by mass spectrometry. Previous studies typically combined 2-D PAGE with MALDI-TOF/TOF MS, a technology which now appears to lack sensitivity to detect additional venom compounds. Here, we report an in-depth study of the honeybee venom proteome using a combinatorial peptide ligand library sample pretreatment to enrich for minor components followed by shotgun LC-FT-ICR MS analysis. This strategy revealed an unexpectedly rich venom composition: in total 102 proteins and peptides were found, with 83 of them never described in bee venom samples before. Based on their predicted function and subcellular location, the proteins could be divided into two groups. A group of 33 putative toxins is proposed to contribute to venom activity by exerting toxic functions or by playing a role in social immunity. The other group, considered as venom trace molecules, appears to be secreted for their functions in the extracellular space, or is unintentionally secreted by the venom gland cells due to insufficient protein recycling or co-secretion with other compounds. In conclusion, our approach allowed to explore the hidden honeybee venom proteome and extended the list of potential venom allergens.

BIOLOGICAL SIGNIFICANCE

This study dug deeper into the complex honeybee venom proteome than ever before by applying a highly performing sample pretreatment and mass spectrometric technology. We present putative biological functions for all identified compounds, largely extending our knowledge of the venom toxicity. In addition, this study offers a long list of potential new venom allergens.

Shotgun proteome analysis of honeybee venom using targeted enrichment strategies

The aim of this study was to explore the honeybee venom proteome applying a shotgun proteomics approach using different enrichment strategies (combinatorial peptide ligand libraries and solid phase extraction). The studies were conducted using nano-LC/MALDI-TOF/TOF-MS system. The MS analysis of peptide profiles (in the range of 900-4500 Da) and virtual gel-image of proteins from Lab-on-Chip assay (in the range of 10-250 kDa) confirm that use of targeted enrichment strategies increase detection of honeybee venom components. The gel-free shotgun strategy and sophisticated instrumentation led to a significant increase of the sensitivity and higher number of identified peptides in honeybee venom samples, comparing with the current literature. Moreover, 11 of 12 known honeybee venom allergens were acknowledged and 4 new, so far uncharacterized proteins were identified. In addition, similarity searches were performed in order to investigate biological relations and homology between newly identified proteins sequences from Apis mellifera and other Hymenoptera.

In vitro diagnosis of Hymenoptera venom allergy and further development of component resolved diagnostics

For most people Hymenoptera stings result in transient and bothersome local inflammatory responses characterized by pain, itching, redness and swelling. In contrast, for those presenting an IgE-mediated allergic reaction, a re-sting may cause life-threatening reactions. In such patients, correct diagnosis is an absolute prerequisite for effective management, i.e. venom-specific immunotherapy. Generally, identification of the offending insect involves a detailed history along with quantification of venom-specific IgE antibodies and venom skin tests. Unfortunately, due to uncertainties associated with both tests, correct diagnosis is not always straightforward. This review summarizes the potentials and limitations of the various in vitro tests that are currently being used in the diagnosis of Hymenoptera venom allergy. Particular attention is paid to the potential of novel cellular tests such as basophil activation tests and component-resolved diagnosis with recombinant venom allergens in the diagnostic approach of patients with difficult diagnosis, i.e. cases in whom traditional venom specific IgE and skin tests yield equivocal or negative results. Finally, this review also covers the recent discoveries in the field of proteome research of Hymenoptera venoms and the selection of cell types for recombinant allergens production.

Unusual stability of messenger RNA in snake venom reveals gene expression dynamics of venom replenishment

Venom is a critical evolutionary innovation enabling venomous snakes to become successful limbless predators; it is therefore vital that venomous snakes possess a highly efficient venom production and delivery system to maintain their predatory arsenal. Here, we exploit the unusual stability of messenger RNA in venom to conduct, for the first time, quantitative PCR to characterise the dynamics of gene expression of newly synthesised venom proteins following venom depletion. Quantitative PCR directly from venom enables real-time dynamic studies of gene expression in the same animals because it circumvents the conventional requirement to sacrifice snakes to extract mRNA from dissected venom glands. Using qPCR and proteomic analysis, we show that gene expression and protein re-synthesis triggered by venom expulsion peaks between days 3-7 of the cycle of venom replenishment, with different protein families expressed in parallel. We demonstrate that venom re-synthesis occurs very rapidly following depletion of venom stores, presumably to ensure venomous snakes retain their ability to efficiently predate and remain defended from predators. The stability of mRNA in venom is biologically fascinating, and could significantly empower venom research by expanding opportunities to produce transcriptomes from historical venom stocks and rare or endangered venomous species, for new therapeutic, diagnostic and evolutionary studies.

Mold and aflatoxin reduction by gamma radiation of packed hot peppers and their evolution during storage

The effect of gamma radiation on moisture content, total mold counts, Aspergillus counts, and aflatoxins of three hot pepper hybrids (Sky Red, Maha, and Wonder King) was investigated. Whole dried peppers packed in polyethylene bags were gamma irradiated at 0 (control), 2, 4, and 6 kGy and stored at 25°C for 90 days. Gamma radiation proved to be effective in reducing total mold and Aspergillus counts in a dose-dependent relationship. Total mold counts in irradiated peppers immediately after treatments were significantly lowered compared with those in nonirradiated samples, achieving 90 and 99% reduction at 2- and 4-kGy doses, respectively. Aspergillus counts were significantly reduced, by 93 and 97%, immediately after irradiation at doses of 2 and 4 kGy, respectively. A radiation dose of 6 kGy completely eliminated the population of total molds and Aspergillus fungi. The evolution of total molds in control and irradiated samples indicated no further fungal proliferation during 3 months of storage at 25°C. Aflatoxin levels were slightly affected by radiation doses of 2 and 4 kGy and showed a nonsignificant reduction of 6% at the highest radiation dose of 6 kGy. The distinct effectiveness of gamma radiation in molds and aflatoxins can be explained by the target theory of food irradiation, which states that the likelihood of a microorganism or a molecule being inactivated by gamma rays increases as its size increases.

Snake venomics of Crotalus tigris: the minimalist toxin arsenal of the deadliest Nearctic rattlesnake venom. Evolutionary Clues for generating a pan-specific antivenom against crotalid type II venoms [corrected]

We report the proteomic and antivenomic characterization of Crotalus tigris venom. This venom exhibits the highest lethality for mice among rattlesnakes and the simplest toxin proteome reported to date. The venom proteome of C. tigris comprises 7-8 gene products from 6 toxin families; the presynaptic β-neurotoxic heterodimeric PLA(2), Mojave toxin, and two serine proteinases comprise, respectively, 66 and 27% of the C. tigris toxin arsenal, whereas a VEGF-like protein, a CRISP molecule, a medium-sized disintegrin, and 1-2 PIII-SVMPs each represent 0.1-5% of the total venom proteome. This toxin profile really explains the systemic neuro- and myotoxic effects observed in envenomated animals. In addition, we found that venom lethality of C. tigris and other North American rattlesnake type II venoms correlates with the concentration of Mojave toxin A-subunit, supporting the view that the neurotoxic venom phenotype of crotalid type II venoms may be described as a single-allele adaptation. Our data suggest that the evolutionary trend toward neurotoxicity, which has been also reported for the South American rattlesnakes, may have resulted by pedomorphism. The ability of an experimental antivenom to effectively immunodeplete proteins from the type II venoms of C. tigris, Crotalus horridus , Crotalus oreganus helleri, Crotalus scutulatus scutulatus, and Sistrurus catenatus catenatus indicated the feasibility of generating a pan-American anti-Crotalus type II antivenom, suggested by the identification of shared evolutionary trends among South and North American Crotalus species.

Reduction of aflatoxin B1 in stored peanuts (Arachis hypogaea L.) using Saccharomyces cerevisiae

Aflatoxin B(1) is a toxigenic and carcinogenic compound produced by Aspergillus flavus and Aspergillus parasiticus. To inhibit aflatoxin contamination of peanuts, seeds of two peanut breeds, IAC Caiapó and IAC Runner 886, were inoculated with A. parasiticus (1.0 × 10(6) spores per ml) and the yeast Saccharomyces cerevisiae (3.2 × 10(7) cells per ml) and incubated at 25°C for 7 and 15 days. Two experiments were conducted for each incubation period separately. The treatments were completely randomized, with three replications per treatment. Treatments included the two cultivars and three types of inoculation (pathogen alone, yeast and pathogen, and yeast 3 h before pathogen). Aflatoxin B(1) was quantified with a densitometer at 366 nm after thin layer chromatography. Aflatoxin B(1) contamination in peanuts was reduced after the addition of S. cerevisiae. The concentration of aflatoxin B(1) decreased by 74.4 and 55.9% after 7 and 15 days, respectively. The greatest aflatoxin reduction was observed when S. cerevisiae was inoculated 3 h before the pathogen in IAC Caiapó seeds and incubated for 7 days at 25°C. The use of S. cerevisiae is a promising strategy for biological control of aflatoxin contamination in peanuts.

Profiling the venom gland transcriptomes of Costa Rican snakes by 454 pyrosequencing

BACKGROUND

A long term research goal of venomics, of applied importance for improving current antivenom therapy, but also for drug discovery, is to understand the pharmacological potential of venoms. Individually or combined, proteomic and transcriptomic studies have demonstrated their feasibility to explore in depth the molecular diversity of venoms. In the absence of genome sequence, transcriptomes represent also valuable searchable databases for proteomic projects.

RESULTS

The venom gland transcriptomes of 8 Costa Rican taxa from 5 genera (Crotalus, Bothrops, Atropoides, Cerrophidion, and Bothriechis) of pitvipers were investigated using high-throughput 454 pyrosequencing. 100,394 out of 330,010 masked reads produced significant hits in the available databases. 5.165,220 nucleotides (8.27%) were masked by RepeatMasker, the vast majority of which corresponding to class I (retroelements) and class II (DNA transposons) mobile elements. BLAST hits included 79,991 matches to entries of the taxonomic suborder Serpentes, of which 62,433 displayed similarity to documented venom proteins. Strong discrepancies between the transcriptome-computed and the proteome-gathered toxin compositions were obvious at first sight. Although the reasons underlaying this discrepancy are elusive, since no clear trend within or between species is apparent, the data indicate that individual mRNA species may be translationally controlled in a species-dependent manner. The minimum number of genes from each toxin family transcribed into the venom gland transcriptome of each species was calculated from multiple alignments of reads matched to a full-length reference sequence of each toxin family. Reads encoding ORF regions of Kazal-type inhibitor-like proteins were uniquely found in Bothriechis schlegelii and B. lateralis transcriptomes, suggesting a genus-specific recruitment event during the early-Middle Miocene. A transcriptome-based cladogram supports the large divergence between A. mexicanus and A. picadoi, and a closer kinship between A. mexicanus and C. godmani.

CONCLUSIONS

Our comparative next-generation sequencing (NGS) analysis reveals taxon-specific trends governing the formulation of the venom arsenal. Knowledge of the venom proteome provides hints on the translation efficiency of toxin-coding transcripts, contributing thereby to a more accurate interpretation of the transcriptome. The application of NGS to the analysis of snake venom transcriptomes, may represent the tool for opening the door to systems venomics.

Ending the drought: new strategies for improving the flow of affordable, effective antivenoms in Asia and Africa

The development of snake antivenoms more than a century ago should have heralded effective treatment of the scourge of snakebite envenoming in impoverished, mostly rural populations around the world. That snakebite still exists today, as a widely untreated illness that maims, kills and terrifies men, women and children in vulnerable communities, is a cruel anachronism. Antivenom can be an effective, safe and affordable treatment for snakebites, but apathy, inaction and the politicisation of public health have marginalised both the problem (making snakebite arguably the most neglected of all neglected tropical diseases) and its solution. For lack of any coordinated approach, provision of antivenoms has been pushed off the public health agenda, leading to an incongruous decline in demand for these crucial antidotes, excused and fed by new priorities, an absence of epidemiological data, and a poor regulatory framework. These factors facilitated the infiltration of poor quality products that degrade user confidence and undermine legitimate producers. The result is that tens of thousands are denied an essential life-saving medicine, allowing a toll of human suffering that is a summation of many individual catastrophes. No strategy has been developed to address this problem and to overcome the intransigence and inaction responsible for the global tragedy of snakebite. Attempts to engage with the broader public health community through the World Health Organisation (WHO), GAVI, and other agencies have failed. Consequently, the toxinology community has taken on a leadership role in a new approach, the Global Snakebite Initiative, which seeks to mobilise the resources, skills and experience of scientists and clinicians for whom venoms, toxins, antivenoms, snakes and snakebites are already fields of interest. Proteomics is one such discipline, which has embraced the potential of using venoms in bio-discovery and systems biology. The fields of venomics and antivenomics have recently evolved from this discipline, offering fresh hope for the victims of snakebites by providing an exciting insight into the complexities, nature, fundamental properties and significance of venom constituents. Such a rational approach brings with it the potential to design new immunising mixtures from which to raise potent antivenoms with wider therapeutic ranges. This addresses a major practical limitation in antivenom use recognised since the beginning of the 20th century: the restriction of therapeutic effectiveness to the specific venom immunogen used in production. Antivenomic techniques enable the interactions between venoms and antivenoms to be examined in detail, and if combined with functional assays of specific activity and followed up by clinical trials of effectiveness and safety, can be powerful tools with which to evaluate the suitability of current and new antivenoms for meeting urgent regional needs. We propose two mechanisms through which the Global Snakebite Initiative might seek to end the antivenom drought in Africa and Asia: first by establishing a multidisciplinary, multicentre, international collaboration to evaluate currently available antivenoms against the venoms of medically important snakes from specific nations in Africa and Asia using a combination of proteomic, antivenomic and WHO-endorsed preclinical assessment protocols, to provide a validated evidence base for either recommending or rejecting individual products; and secondly by bringing the power of proteomics to bear on the design of new immunising mixtures to raise Pan-African and Pan-Asian polyvalent antivenoms of improved potency and quality. These products will be subject to rigorous clinical assessment. We propose radically to change the basis upon which antivenoms are produced and supplied for the developing world. Donor funding and strategic public health alliances will be sought to make it possible not only to sustain the financial viability of antivenom production partnerships, but also to ensure that patients are relieved of the costs of antivenom so that poverty is no longer a barrier to the treatment of this important, but grossly neglected public health emergency.

cDNA cloning, structural, and functional analyses of venom phospholipases A₂ and a Kunitz-type protease inhibitor from steppe viper Vipera ursinii renardi

Snake venom phospholipases A₂ (PLA₂s) display a wide array of biological activities and are each characteristic to the venom. Here, we report on the cDNA cloning and characterization of PLA₂s from the steppe viper Vipera ursinii renardi venom glands. Among the five distinct PLA₂ cDNAs cloned and sequenced, the most common were the clones encoding a basic Ser-49 containing PLA₂ (Vur-S49). Other clones encoded either ammodytin analogs I1, I2d and I2a (designated as Vur-PL1, Vur-PL2 and Vur-PL3, respectively) or an ammodytoxin-like PLA₂ (Vurtoxin). Additionally, a novel Kunitz-type trypsin inhibitor for this venom species was cloned and sequenced. Comparison of these PLA₂ and Kunitz inhibitor sequences with those in the sequence data banks suggests that the viper V. u. renardi is closely related to Vipera ammodytes and Vipera aspis. Separation of V. u. renardi venom components by gel-filtration and ion-exchange chromatography showed the presence of many PLA₂ isoforms. Remarkably, the most abundant PLA₂ isolated was Vur-PL2 while Vur-S49 analog was in very low yield. There are great differences between the proportion of cDNA clones and that of the proteins isolated. Two Vur-PL2 isoforms (designated as Vur-PL2A and Vur-PL2B) indistinguishable by masses, peptide mass fingerprinting, N-terminal sequences and CD spectroscopy were purified from the pooled venom. However, when rechromatographed on cation-exchanger, Vur-PL2A showed only one peak corresponding to Vur-PL2B, suggesting the existence of conformers for Vur-PL2. Vur-PL2B was weakly cytotoxic to rat pheochromocytoma PC12 cells and showed both strong anticoagulant and anti-platelet activities. This is the first case of a strong anticoagulating ammodytin I analog in Vipera venom.