Venomics of the poorly studied hognosed pitvipers Porthidium arcosae and Porthidium volcanicum

We report the first proteomics analyses of the venoms of two poorly studied snakes, the Manabi hognosed pitviper Porthidium arcosae endemic to the western coastal province of Manabí (Ecuador), and the Costa Rican hognosed pitviper P. volcanicum with distribution restricted to South Pacific Costa Rica and western Panamá. These venom proteomes share a conserved compositional pattern reported in four other congeneric species within the clade of South American Porthidium species, P. nasutum, P. lansbergii, P. ophryomegas, and P. porrasi. The paraspecific immunorecognition profile of antivenoms produced in Costa Rica (ICP polyvalent), Perú (Instituto Nacional de Salud) and Brazil (soro antibotrópico pentavalente, SAB, from Instituto Butantan) against the venom of P. arcosae was investigated through a third-generation antivenomics approach. The maximal venom-binding capacities of the investigated antivenoms were 97.1 mg, 21.8 mg, and 25.7 mg of P. arcosae venom proteins per gram of SAB, ICP, and INS-PERU antibody molecules, respectively, which translate into 28.4 mg, 13.1 mg, and 15.2 mg of total venom proteins bound per vial of SAB, ICP, and INS-PERU AV. The antivenomics results suggest that 21.8%, 7.8% and 6.1% of the SAB, ICP, and INS-PERU antibody molecules recognized P. arcosae venom toxins. The SAB antivenom neutralized P. arcosae venom's lethality in mice with an ED₅₀ of 31.3 mgV/g SAB AV. This preclinical neutralization paraspecificity points to Brazilian SAB as a promising candidate for the treatment of envenomings by Ecuadorian P. arcosae. BIOLOGICAL SIGNIFICANCE: Assessing the preclinical efficacy profile of antivenoms against homologous and heterologous medically relevant snake venoms represents an important goal towards defining the biogeographic range of their clinical utility. This is particularly relevant in regions, such as Mesoamerica, where a small number of pharmaceutical companies produce antivenoms against the venoms of a small number of species of maximum medical relevance among the local rich herpetofauna, leaving a wide range of snakes of secondary medical relevance, but also causing life-threatening human envenomings without nominal clinical coverage. This work is part of a larger project aiming at mapping the immunological characteristics of antivenoms generated in Latin American countries towards venoms of such poorly studied snakes of the local and neighboring countries' herpetofauna. Here we report the proteomics characterization of the Manabi hognosed pitviper Porthidium arcosae endemic to the western coastal province of Manabí (Ecuador), and the Costa Rican hognosed pitviper P. volcanicum with distribution restricted to southwestern Costa Rica, the antivenomics assessment of three bothropoid commercial antivenoms produced in Costa Rica, Perú, and Brazil against the venom components of P. arcosae, and the in vivo capacity of the Brazilian soro antibotrópico pentavalente (SAB) from Instituto Butantan to neutralize the murine lethality of P. arcosae venom. The preclinical paraspecific ED₅₀ of 31.3 mg of P. arcosae venom per gram of antivenom points to Brazilian SAB as a promising candidate for the treatment of envenomings by the Manabi hognosed pitviper P. arcosae.

Immunorecognition capacity of Indian polyvalent antivenom against venom toxins from two populations of Echis carinatus

Clinicians report low efficacy of Indian polyvalent antivenom (PAV), with >20 vials required for treatment of a snakebite envenoming. We hypothesize that the antivenom efficacy could be reduced due to insufficient antibodies against some venom toxins. To test this, we used third-generation antivenomics to reveal bound and unbound venom toxins of Echis carinatus venom from Goa (ECVGO) and Tamil Nadu (ECVTN). We used 60, 120, 180, 240, 300, and 360 μg of venom and passed through mini-columns containing ~5 mg Antivenom bound to CNBr beads. The non-retained (unbound) and retained (bound) toxins were identified using reverse-phase HPLC and tandem mass spectrometry. Low molecular weight toxins - Short disintegrins (5.3 kDa) and DIS domain of P-II SVMP from ECVGO and ECVTN showed poor binding with antivenom. The immunorecognition sites of antivenom saturated at the lower antivenom-venom ratio for ECVGO than for ECVTN. The immunoretained capacity of antivenom against ECVTN was 140.6 μg and ECVGO was 125.1 μg. The amount of immunoretained toxins quantified can further be used to estimate the efficacy of antivenom by correlating it with in-vivo studies. The unbound toxins identified from this study could be targeted to improve the effectiveness of antivenom.

Proteomics and neutralization of Bungarus multicinctus (Many-banded Krait) venom: Intra-specific comparisons between specimens from China and Taiwan

The Many-banded Krait (Bungarus multicinctus) is a medically important venomous snake in East Asia. This study investigated the venom proteomes of B. multicinctus from Guangdong, southern China (BM-China) and insular Taiwan (BM-Taiwan), and the neutralization activities of two antivenom products (produced separately in China and Taiwan) against the lethal effect of the venoms. The venom proteomes of both specimens contained similar toxin families, notwithstanding small variations in the subtypes and abundances of minor components. More than 90% of the total venom proteins belong to three-finger toxins (3FTx, including alpha-neurotoxins) and phospholipases A₂ (PLA₂, including beta-bungarotoxins), supporting their key involvement in the pathophysiology of krait envenomation which manifests as pre- and post-synaptic neurotoxicity. The venoms exhibited potent neurotoxic and lethal effects with extremely low i.v. LD₅₀ of 0.027 μg/g (Bm-China) and 0.087 μg/g (Bm-Taiwan), respectively, in mice. Bungarus multicinctus monovalent antivenom (BMMAV) produced in China and Neuro bivalent antivenom (NBAV) produced in Taiwan were immunoreactive toward both venoms and their toxin fractions. The antivenoms neutralized the venom lethality variably, with BMMAV being more efficacious than NBAV by approximately two-fold. Findings suggest that the monovalent antivenom has a higher potency presumably due to its species-specificity toward the krait venom.

Proteomics, toxicity and antivenom neutralization of Sri Lankan and Indian Russell's viper (Daboia russelii) venoms

BACKGROUND

The western Russell's viper (Daboia russelii) is widely distributed in South Asia, and geographical venom variation is anticipated among distant populations. Antivenoms used for Russell's viper envenomation are, however, raised typically against snakes from Southern India. The present study investigated and compared the venom proteomes of D. russelii from Sri Lanka (DrSL) and India (DrI), the immunorecognition of Indian VINS Polyvalent Antivenom (VPAV) and its efficacy in neutralizing the venom toxicity.

METHODS

The venoms of DrSL and DrI were decomplexed with C18 high-performance liquid chromatography and SDS-polyacrylamide gel electrophoresis under reducing conditions. The proteins fractionated were identified through nano-ESI-liquid chromatography-tandem mass spectrometry (LCMS/MS). The immunological studies were conducted with enzyme-linked immunosorbent assay. The neutralization of the venom procoagulant effect was evaluated in citrated human plasma. The neutralization of the venom lethality was assessed in vivo in mice adopting the WHO protocol.

RESULTS

DrSL and DrI venom proteomes showed comparable major protein families, with phospholipases A2 (PLA2) being the most abundant (> 60% of total venom proteins) and diverse (six protein forms identified). Both venoms were highly procoagulant and lethal (intravenous median lethal dose in mice, LD50 = 0.24 and 0.32 µg/g, for DrSL and DrI, respectively), while lacking hemorrhagic and anticoagulant activities. VPAV was immunoreactive toward DrSL and DrI venoms, indicating conserved protein antigenicity in the venoms. The high molecular weight venom proteins were, however, more effectively immunorecognized than small ones. VPAV was able to neutralize the coagulopathic and lethal effects of the venoms moderately.

CONCLUSION

Considering that a large amount of venom can be injected by Russell's viper during envenomation, the potency of antivenom can be further improved for optimal neutralization and effective treatment. Region-specific venoms and key toxins may be incorporated into the immunization procedure during antivenom production.

Comparative venomics and preclinical efficacy evaluation of a monospecific Hemachatus antivenom towards sub-Saharan Africa cobra venoms

Cobras are the most medically important elapid snakes in Africa. The African genera Naja and Hemachatus include snakes with neurotoxic and cytotoxic venoms, with shared biochemical, toxinological and antigenic characteristics. We have studied the antigenic cross-reactivity of four sub-Saharan Africa cobra venoms against an experimental monospecific Hemachatus haemachatus antivenom through comparative proteomics, preclinical assessment of neutralization, and third generation antivenomics. The venoms of H. haemachatus, N. annulifera, N. mossambica and N. nigricollis share an overall qualitative family toxin composition but depart in their proportions of three-finger toxin (3FTxs) classes, phospholipases A₂ (PLA₂s), snake venom metalloproteinases (SVMPs), and cysteine-rich secretory proteins (CRISPs). A monospecific anti-Hemachatus antivenom produced by Costa Rican Instituto Clodomiro Picado neutralized the lethal activity of the homologous and heterologous neuro/cytotoxic (H. haemachatus) and cyto/cardiotoxic (N. mossambica and N. nigricollis) venoms of the three spitting cobras sampled, while it was ineffective against the lethal and toxic activities of the neurotoxic venom of the non-spitting snouted cobra N. annulifera. The ability of the anti-Hemachatus-ICP antivenom to neutralize toxic (dermonecrotic and anticoagulant) and enzymatic (PLA₂) activities of spitting cobra venoms suggested a closer kinship of H. haemachatus and Naja subgenus Afrocobra spitting cobras than to Naja subgenus Uraeus neurotoxic taxa. These results were confirmed by third generation antivenomics. BIOLOGICAL SIGNIFICANCE: African Naja species represent the most widespread medically important elapid snakes across Africa. To gain deeper insight into the spectrum of medically relevant toxins, we compared the proteome of three spitting cobras (Hemachatus haemachatus, Naja mossambica and N. nigricollis) and one non-spitting cobra (N. annulifera). Three finger toxins and phospholipases A₂ are the two major protein families among the venoms analyzed. The development of antivenoms of broad species coverage is an urgent need in sub-Saharan Africa. An equine antivenom raised against H. haemachatus venom showed cross-reactivity with the venoms of H. haemachatus, N. mossambica and N. nigricollis, while having poor recognition of the venom of N. annulifera. This immunological information provides clues for the design of optimum venom mixtures for the preparation of broad spectrum antivenoms.

Bothrops atrox, the most important snake involved in human envenomings in the amazon: How venomics contributes to the knowledge of snake biology and clinical toxinology

Bothrops atrox snakes are mostly endemic of the Amazon rainforest and is certainly the South American pit viper responsible for most of the snakebites in the region. The composition of B. atrox venom is significantly known and has been used to trace the relevance of the venom phenotype for snake biology and for the impacts in the clinics of human patients involved in accidents by B. atrox. However, in spite of the wide distribution and the great medical relevance of B. atrox snakes, B. atrox taxonomy is not fully resolved and the impacts of the lack of taxonomic resolution on the studies focused on venom or envenoming are currently unknown. B. atrox venom presents different degrees of compositional variability and is generally coagulotoxic, inducing systemic hematological disturbances and local tissue damage in snakebite patients. Antivenoms are the effective therapy for attenuating the clinical signs. This review brings a comprehensive discussion of the literature concerning B. atrox snakes encompassing from snake taxonomy, diet and venom composition, towards clinical aspects of snakebite patients and efficacy of the antivenoms. This discussion is highly supported by the contributions that venomics and antivenomics added for the advancement of knowledge of B. atrox snakes, their venoms and the treatment of accidents they evoke.

Proteomics and antivenom immunoprofiling of Russell's viper (Daboia siamensis) venoms from Thailand and Indonesia

The Eastern Russell’s viper, Daboia siamensis, is a WHO Category 1 medically important venomous snake. It has a wide but disjunct distribution in Southeast Asia. The specific antivenom, D. siamensis Monovalent Antivenom (DsMAV-Thailand) is produced in Thailand but not available in Indonesia, where a heterologous trivalent antivenom, Serum Anti Bisa Ular (SABU), is used instead. This study aimed to investigate the geographical venom variation of D. siamensis from Thailand (Ds-Thailand) and Indonesia (Ds-Indonesia), and the immunorecognition of the venom proteins by antivenoms.

Quantitative proteomic analysis and antivenom study revealing that neurotoxic phospholipase A2 enzymes, the major toxin class of Russell's viper venom from southern India, shows the least immuno-recognition and neutralization by commercial polyvalent antivenom

The proteome composition of Russell's viper venom (RVV) from southern India (SI) was investigated by 1D-SDS-PAGE of venom followed by tandem mass spectrometry analysis of protein bands. A total of 66 proteins belonging to 14 snake venom protein families were identified by LC-MS/MS analysis against Viperidae (taxid 8689) protein entries from the non-redundant NCBI database. Phospholipase A2 (43.25%) and snaclec (14.57%) represented the most abundant enzymatic and non-enzymatic proteins, respectively. SI RVV was characterized as containing a higher quantity of PLA2 and a lower amount of Kunitz-type serine protease inhibitors, in comparison to RVV from other regions of the Indian subcontinent. The enzymatic activities, pharmacological properties, and clinical manifestations of RV envenomation in SI were well correlated with its proteome composition; however, ATPase, ADPase, and hyaluronidase enzymes were not identified by LC-MS/MS analysis, owing to paucity of the existing database. Neurological symptoms exhibited by RV-bite patients in SI were correlated to the presence of abundant neurotoxic phospholipase A2 enzymes (15.66%) in SI RVV. Neutralization studies, immunological cross-reactivity, and antivenomics studies unequivocally demonstrated the poor recognition and lowest neutralization of PLA2 enzymes by commercial polyvalent antivenom, which is a major concern for the treatment of RV-envenomed patients in SI.

Antivenomics as a tool to improve the neutralizing capacity of the crotalic antivenom: a study with crotamine

Background

Snakebite treatment requires administration of an appropriate antivenom that should contain antibodies capable of neutralizing the venom. To achieve this goal, antivenom production must start from a suitable immunization protocol and proper venom mixtures. In Brazil, antivenom against South American rattlesnake (Crotalus durissus terrificus) bites is produced by public institutions based on the guidelines defined by the regulatory agency of the Brazilian Ministry of Health, ANVISA. However, each institution uses its own mixture of rattlesnake venom antigens. Previous works have shown that crotamine, a toxin found in Crolatus durissus venom, shows marked individual and populational variation. In addition, serum produced from crotamine-negative venoms fails to recognize this molecule.

Methods

In this work, we used an antivenomics approach to assess the cross-reactivity of crotalic antivenom manufactured by IVB towards crotamine-negative venom and a mixture of crotamine-negative/crotamine-positive venoms.

Results

We show that the venom mixture containing 20% crotamine and 57% crotoxin produced a strong immunogenic response in horses. Antivenom raised against this venom mixture reacted with most venom components including crotamine and crotoxin, in contrast to the antivenom raised against crotamine-negative venom.

Conclusions

These results indicate that venomic databases and antivenomics analysis provide a useful approach for choosing the better venom mixture for antibody production and for the subsequent screening of antivenom cross-reactivity with relevant snake venom components.

Strategies in 'snake venomics' aiming at an integrative view of compositional, functional, and immunological characteristics of venoms

This work offers a general overview on the evolving strategies for the proteomic analysis of snake venoms, and discusses how these may be combined through diverse experimental approaches with the goal of achieving a more comprehensive knowledge on the compositional, toxic, and immunological characteristics of venoms. Some recent developments in this field are summarized, highlighting how strategies have evolved from the mere cataloguing of venom components (proteomics/venomics), to a broader exploration of their immunological (antivenomics) and functional (toxicovenomics) characteristics. Altogether, the combination of these complementary strategies is helping to build a wider, more integrative view of the life-threatening protein cocktails produced by venomous snakes, responsible for thousands of deaths every year.

What killed Karl Patterson Schmidt? Combined venom gland transcriptomic, venomic and antivenomic analysis of the South African green tree snake (the boomslang), Dispholidus typus

Background

Non-front-fanged colubroid snakes comprise about two-thirds of extant ophidian species. The medical significance of the majority of these snakes is unknown, but at least five species have caused life-threatening or fatal human envenomings. However, the venoms of only a small number of species have been explored.

Methods

A combined venomic and venom gland transcriptomic approach was employed to characterise of venom of Dispholidus typus (boomslang), the snake that caused the tragic death of Professor Karl Patterson Schmidt. The ability of CroFab™ antivenom to immunocapture boomslang venom proteins was investigated using antivenomics.

Results

Transcriptomic-assisted proteomic analysis identified venom proteins belonging to seven protein families: three-finger toxin (3FTx); phospholipase A₂ (PLA₂); cysteine-rich secretory proteins (CRISP); snake venom (SV) serine proteinase (SP); C-type lectin-like (CTL); SV metalloproteinases (SVMPs); and disintegrin-like/cysteine-rich (DC) proteolytic fragments. CroFab™ antivenom efficiently immunodepleted some boomslang SVMPs.

Conclusions

The present work is the first to address the overall proteomic profile of D. typus venom. This study allowed us to correlate the toxin composition with the toxic activities of the venom. The antivenomic analysis suggested that the antivenom available at the time of the unfortunate accident could have exhibited at least some immunoreactivity against the boomslang SVMPs responsible for the disseminated intravascular coagulation syndrome that caused K.P. Schmidt's fatal outcome.

General significance

This study may stimulate further research on other non-front-fanged colubroid snake venoms capable of causing life-threatening envenomings to humans, which in turn should contribute to prevent fatal human accidents, such as that unfortunately suffered by K.P. Schmidt.

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The venom proteome of Dispholidus typus (boomslang) is reported.

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Transcriptomic-assisted proteomic analysis identified venom proteins belonging to seven protein families.

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Boomslang venom proteome is dominated (75%) by snake venom PIII-metalloproteinases (PIII-SVMPs).

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CroFab™ antivenom efficiently immunodepleted some boomslang PIII-SVMPs.

Proteomics and antivenomics of Papuan black snake (Pseudechis papuanus) venom with analysis of its toxicological profile and the preclinical efficacy of Australian antivenoms

The Papuan black snake (Pseudechis papuanus Serpentes: Elapidae) is endemic to Papua New Guinea, Indonesian Papua and Australia's Torres Strait Islands. We have investigated the biological activity and proteomic composition of its venom. The P. papuanus venom proteome is dominated by a variety (n≥18) of PLA₂s, which together account for ~90% of the venom proteins, and a set of low relative abundance proteins, including a short-neurotoxic 3FTx (3.1%), 3-4 PIII-SVMPs (2.8%), 3 cysteine-rich secretory proteins (CRISP; 2.3%) 1-3 l-amino acid oxidase (LAAO) molecules (1.6%). Probing of a P. papuanus cDNA library with specific primers resulted in the elucidation of the full-length nucleotide sequences of six new toxins, including vespryn and NGF not found in the venom proteome, and a calglandulin protein involved in toxin expression with the venom glands. Intravenous injection of P. papuanus venom in mice induced lethality, intravascular haemolysis, pulmonary congestion and oedema, and anticoagulation after intravenous injection, and these effects are mainly due to the action of PLA₂s. This study also evaluated the in vivo preclinical efficacy of Australian black snake and polyvalent Seqirus antivenoms. These antivenoms were effective in neutralising the lethal, PLA₂ and anticoagulant activities of P. papuanus venom in mice. On the other hand, all of the Seqirus antivenoms tested using an antivenomic approach exhibited strong immunorecognition of all the venom components. These preclinical results suggest that Australian Seqirus¹ antivenoms may provide paraspecific protection against P. papuanus venom in humans.

SIGNIFICANCE PARAGRAPH

The toxicological profile and proteomic composition of the venom of the Papuan black snake, Pseudechis papuanus, a large diurnal snake endemic to the southern coast of New Guinea and a handful of close offshore islands, were investigated. Intravenous injection of P. papuanus venom in mice induced intravascular hemolysis, pulmonary congestion and edema, anticoagulation, and death. These activities could be assigned to the set of PLA₂ molecules, which dominate the P. papuanus venom proteome. This study also showed that Australian Seqirus black snake or polyvalent antivenoms were effective in neutralising the lethal, PLA₂ and anticoagulant activities of the venom. These preclinical results support the continued recommendation of these Seqirus antivenoms in the clinical management of P. papuanus envenoming in Australia, Papua New Guinea or Indonesian Papua Province.

Preclinical evaluation of three polyspecific antivenoms against the venom of Echis ocellatus: Neutralization of toxic activities and antivenomics

Snakebite envenoming has a heavy burden in the public health in sub-Saharan Africa. The viperid species Echis ocellatus (carpet viper or saw-scaled viper) is the medically most important snake in the savannahs of western sub-Saharan Africa. Several antivenoms are being distributed and used in this region for the treatment of envenomings by E. ocellatus, but the preclinical efficacy of some of these antivenoms has not been assessed. The present study evaluated the preclinical efficacy against E. ocellatus venom of three polyspecific antivenoms: (a) Snake Venom Antiserum (Pan Africa), manufactured by Premium Serums and Vaccines (India); (b) Snake Venom Antiserum (Africa), manufactured by VINS Bioproducts (India); and (c) Antivipmyn(®) Africa, manufactured by Instituto Bioclon (Mexico). Antivenomics analysis revealed the ability of the three antivenoms to immunocapture the majority of components of the venoms of E. ocellatus from Cameroon, Nigeria and Mali, although their maximal immunocapturing capability varied. Bioclon and Premium Serums antivenoms were effective in the neutralization of lethal, hemorrhagic and in vitro coagulant activities of the venom of E. ocellatus from Cameroon, albeit with different potencies. VINS antivenom neutralized hemorrhagic activity of this venom, but failed to neutralize lethality at the highest antivenom dose tested, and had a low neutralizing efficacy against in vitro coagulant effect.

Proteomic characterization and comparison of venoms from two elapid snakes (Bungarus multicinctus and Naja atra) from China

Bungarus multicinctus (many-banded krait) and Naja atra (Chinese cobra) are widely distributed and medically important venomous snakes in China; however, their venom proteomic profiles have not been fully compared. Here, we fractionated crude venoms and analyzed them using a combination of proteomic techniques. Three-finger toxins (3-FTx) and phospholipase A2 (PLA2) were most abundant in both species, respectively accounting for 32.6% and 66.4% of total B. multicinctus venom, and 84.3% and 12.2% of total N. atra venom. Venoms from these two species contained one common protein family and six less abundant species-specific protein families. The proteomic profiles of B. multicinctus and N. atra venoms and analysis of toxicological activity in mice suggested that 3-FTx and PLA2 are the major contributors to clinical symptoms caused by envenomation. The venoms differed in enzymatic activity, likely the result of inter-specific variation in the amount of related venom components. Antivenomics assessment revealed that a small number of venom components (3-FTxs and PLA2s in B. multicinctus, and 3-FTxs in N. atra) could not be immunocaptured completely, suggesting that we should pay attention to enhancing the immune response of these components in designing commercial antivenoms for B. multicinctus and N. atra.

BIOLOGICAL SIGNIFICANCE

The proteomic profiles of venoms from two medically important snake species - B. multicinctus and N. atra - have been explored. Quantitative and qualitative differences are evident in both venoms when proteomic profiles and transcriptomic results are compared; this is a reminder that combined approaches are needed to explore the precise composition of snake venom. Two protein families (3-FTx and PLA2) of high abundance in these snake venoms are major players in the biochemical and pharmacological effects of envenomation. Elucidation of the proteomic profiles of these snake venoms is helpful in understanding composition-function relationships and will facilitate the clinical application of antivenoms.

A comparative study of venomics of Naja naja from India and Sri Lanka, clinical manifestations and antivenomics of an Indian polyspecific antivenom

Naja naja (Indian cobra) from Sri Lanka and India is the WHO Category 1 medically important snakes in both countries. Some antivenom produced against Indian N. naja (NNi) were less effective against Sri Lankan N. naja (NNsl). Proteomes of NNi and NNsl venoms were studied by RP-HPLC, SDS-PAGE and LC/MS/MS. Six protein families were identified in both venoms with the most abundant were the 3 finger toxins (3FTs) where cytotoxins (CTX) subtype predominated, followed by phospholipase A2, cysteine-rich venom protein, snake venom metalloproteases, venom growth factors, and protease inhibitors. Qualitative and quantitative differences in the venomics profiles were observed. Some proteins were isolated from either NNi or NNsl venom. Postsynaptic neurotoxins (NTX) were identified for the first time in NNsl venom. Thus, there are geographic intra-specific variations of venom composition of the two N. naja. The relative abundance of CTX and NTX explained well the clinical manifestations of these venoms. Antivenomics study of an Indian antivenom (Vins) showed the antibodies effectively bound all venom toxins from both snakes but more avidly to the Indian venom proteins. The lower antibody affinity towards the 'heterologous' venom was the likely cause of poor efficacy of the Indian antivenom used to treat NNsl envenoming.

Combined venomics, venom gland transcriptomics, bioactivities, and antivenomics of two Bothrops jararaca populations from geographic isolated regions within the Brazilian Atlantic rainforest

Bothrops jararaca is a slender and semi-arboreal medically relevant pit viper species endemic to tropical and subtropical forests in southern Brazil, Paraguay, and northern Argentina (Misiones). Within its geographic range, it is often abundant and is an important cause of snakebite. Although no subspecies are currently recognized, geographic analyses have revealed the existence of two well-supported B. jararaca clades that diverged during the Pliocene ~3.8Mya and currently display a southeastern (SE) and a southern (S) Atlantic rainforest (Mata Atlântica) distribution. The spectrum, geographic variability, and ontogenetic changes of the venom proteomes of snakes from these two B. jararaca phylogroups were investigated applying a combined venom gland transcriptomic and venomic analysis. Comparisons of the venom proteomes and transcriptomes of B. jararaca from the SE and S geographic regions revealed notable interpopulational variability that may be due to the different levels of population-specific transcriptional regulation, including, in the case of the southern population, a marked ontogenetic venom compositional change involving the upregulation of the myotoxic PLA2 homolog, bothropstoxin-I. This population-specific marker can be used to estimate the proportion of venom from the southern population present in the B. jararaca venom pool used for the Brazilian soro antibotrópico (SAB) antivenom production. On the other hand, the southeastern population-specific D49-PLA2 molecules, BinTX-I and BinTX-II, lend support to the notion that the mainland ancestor of Bothrops insularis was originated within the same population that gave rise to the current SE B. jararaca phylogroup, and that this insular species endemic to Queimada Grande Island (Brazil) expresses a pedomorphic venom phenotype. Mirroring their compositional divergence, the two geographic B. jararaca venom pools showed distinct bioactivity profiles. However, the SAB antivenom manufactured in Vital Brazil Institute neutralized the lethal effect of both venoms to a similar extent. In addition, immobilized SAB antivenom immunocaptured most of the venom components of the venoms of both B. jararaca populations, but did not show immunoreactivity against vasoactive peptides. The Costa Rican bothropic-crotalic-lachesic (BCL) antivenom showed the same lack of reactivity against vasoactive peptides but, in addition, was less efficient immunocapturing PI- and PIII-SVMPs from the SE venom, and bothropstoxin-I, a CRISP molecule, and a D49-PLA2 from the venom of the southern B. jararaca phylogroup. The remarkable paraspecificity exhibited by the Brazilian and the Costa Rican antivenoms indicates large immunoreactive epitope conservation across the natural history of Bothrops, a genus that has its roots in the middle Miocene. This article is part of a Special Issue entitled: Omics Evolutionary Ecolog.

Venomics and antivenomics of Bothrops erythromelas from five geographic populations within the Caatinga ecoregion of northeastern Brazil

The Caatinga lancehead, Bothrops erythromelas, is a medically relevant species, responsible for most of the snakebite accidents in most parts of its distribution range in northeastern Brazil. The spectrum and geographic variability of its venom toxins were investigated applying a venomics approach to venom pools from five geographic areas within the Caatinga ecoregion. Despite its wide habitat, populations of B. erythromelas from Ceará, Pernambuco, Juazeiro, Paraiba, and Ilha de Itaparica exhibit highly conserved venom proteomes. Mirroring their compositional conservation, the five geographic venom pools also showed qualitatively and quantitatively overlapping antivenomic profiles against antivenoms generated in Vital Brazil (BR) and Clodomiro Picado (CR) Institutes, using different venoms in the immunization mixtures. The paraspecificity exhibited by the Brazilian SAB and the Costa Rican BCL antivenoms against venom toxins from B. erythromelas indicates large immunoreactive epitope conservation across genus Bothrops during the last ~14 million years, thus offering promise for the possibility of generating a broad-spectrum bothropic antivenom. Biological Significance Accidental snakebite envenomings represent an important public health hazard in Brazil. Ninety per cent of the yearly estimated 20-30,000 snakebite accidents are caused by species of the Bothrops genus. Bothrops erythromelas, a small, moderately stocky terrestrial venomous snake, is responsible for most of the snakebite accidents in its broad distribution range in the Caatinga, a large ecoregion in northeastern Brazil. To gain a deeper insight into the spectrum of medically important toxins present in the venom of the Caatinga lancehead, we applied a venomics approach to define the proteome and geographic variability of adult B. erythromelas venoms from five geographic regions. Although intraspecific compositional variation between venoms among specimens from different geographic regions has long been appreciated by herpetologists and toxinologists as a general feature of highly adaptable and widely distributed snake species, the five B. erythromelas populations investigated exhibit highly conserved venom proteomes. The overall toxin profile of the Caatinga lancehead's venom explains the local and systemic effects observed in envenomations by B. erythromelas. The five geographic venom pools sampled also showed qualitatively and quantitatively overlapping antivenomic profiles against antivenoms generated using different bothropic venoms in the immunization mixtures. The large immunoreactive epitope conservation across genus Bothrops offers promise for the generation of a broad-spectrum bothropic antivenom.

Preclinical efficacy of Australian antivenoms against the venom of the small-eyed snake, Micropechis ikaheka, from Papua New Guinea: an antivenomics and neutralization study

There is no specific antivenom for the treatment of envenoming by the small-eyed snake, Micropechis ikaheka, a dangerous fossorial species endemic to Papua New Guinea, Irian Jaya (West Papua) and neighbouring islands. This study evaluated one marine (sea snake) and four terrestrial (tiger snake, brown snake, black snake and polyvalent) antivenoms, manufactured in Australia by bioCSL Limited, for their ability to immunoreact ('antivenomic' analysis) and neutralize enzymatic and toxic activities of M. ikaheka venom. All antivenoms neutralized lethality of the venom and attenuated, dose-dependently, myotoxic activity. The polyvalent antivenom also neutralized cardiotoxic activity. In contrast, antivenoms were ineffective in the neutralization of phospholipase A₂ (PLA₂) and anticoagulant activities. Antivenomics outcomes were in concordance with neutralization tests, for chromatographic peaks corresponding to α-neurotoxins of the three finger family, responsible for lethality, were quantitatively retained in the immunoaffinity columns, whereas peaks corresponding to PLA₂s were immunocaptured only to a partial extent. The ability of antivenoms to neutralize lethal, i.e. neurotoxic, and myotoxic activities of M. ikaheka venom, which represent the most relevant clinical manifestations of envenoming, suggests that these antivenoms may provide paraspecific protection in humans, although the poor neutralization of PLA₂ supports the need for well-designed clinical studies to not only determine which antivenoms are most appropriate for treatment of M. ikaheka envenoming, but to also fully describe the syndrome of envenoming caused by this beautiful, but lethal species.

BIOLOGICAL SIGNIFICANCE

Snakebite by the small-eyed snake, Micropechis ikaheka, in Papua New Guinea can be life-threatening. The predominant clinical features in this envenoming are neurotoxicity and systemic myotoxicity. Although it accounts for only a small proportion of snakebites on the mainland, 40% of snakebites on Karkar Island are attributed to bites by the Ikaheka snake. However, no specific antivenom is available for the treatment of M. ikaheka envenoming in Papua New Guinea. This study evaluated a panel of Australian bioCSL antivenoms for their paraspecific immunoreaction and neutralization of the toxic activities of M. ikaheka venom. All antivenoms exhibited strong immunorecognition of α-neurotoxins of the 3FTx family and neutralized the lethal, i.e. neurotoxic, and myotoxic activities of M. ikaheka venom. However, these antivenoms exhibited poor neutralization of PLA₂ and anticoagulant activities. This study suggests that the Australian antivenoms may provide paraspecific protection against M. ikaheka venom in humans, a hypothesis that demands studies aimed at assessing whether these antivenoms neutralize neurotoxicity and myotoxicity in the clinical setting.

Immunological profile of antivenoms: preclinical analysis of the efficacy of a polyspecific antivenom through antivenomics and neutralization assays

Parenteral administration of animal-derived antivenoms constitutes the mainstay in the treatment of snakebite envenomings. Despite the fact that this therapy has been available for over a century, the detailed understanding of the neutralizing and immunoreactivity profiles of the majority of antivenoms is pending. Currently, a combination of preclinical neutralization tests and 'antivenomics', i.e. a proteomic-based assessment of antivenom immunoreactivity, provides a powerful analytical platform to investigate the preclinical efficacy of antivenoms. In this review, the studies performed on the polyvalent antivenom manufactured by Instituto Clodomiro Picado, Costa Rica, are summarized. This antivenom is prepared by immunizing horses with a mixture of the venoms of Bothrops asper, Crotalus simus and Lachesis stenophrys, and is used in Central America for the treatment of envenomings by viperid species. Overall, the antivenom shows a widespread pattern of immunological reactivity against homologous and heterologous venoms, which correlates with its ability to neutralize lethal, hemorrhagic, myotoxic, coagulant, defibrinogenating, phospholipase A2 and proteinase activities of viperid venoms. At the same time, antivenomics detected several venom components against which the antivenom shows only partial or negligible immunorecognition, such as low molecular mass vasoactive peptides, disintegrins, and some phospholipases A2, P-I metalloproteinases and serine proteinases. Such information can be used to design strategies for enhancing the antibody response of horses against poorly immunogenic, toxicologically-relevant venom components in order to further improve the efficacy of this antivenom.

BIOLOGICAL SIGNIFICANCE

The timely parenteral administration of an appropriate antivenom remains, more than a century after the development of the first serum antivenimeux by Calmette and Phisalix and Bertrand, the only currently effective treatment for snakebite envenomings. A key technical issue in the generation of novel antivenoms is the design of optimized immunization venom mixtures that ensure that the resulting antidotes will be effective against the highest number of venoms from snakes of medical concern across the geographical range where they will be used. Antivenomics is a proteomics-based protocol developed to complement in vitro and in vivo standard preclinical tests in the qualitative and quantitative characterization of the immunological profile and the extent of cross-reactivity of antivenoms against homologous and heterologous venoms. Antivenomics is translational venomics. The combination of antivenomics and neutralization assays represents a powerful analytical platform to investigate the efficacy of antivenoms at the molecular and preclinical levels. This article is part of a Special Issue entitled: Proteomics of non-model organisms.

Proteomic and biochemical analyses of short-tailed pit viper (Gloydius brevicaudus) venom: age-related variation and composition-activity correlation

We conducted an in-depth analysis of the proteomic and biochemical profiles of the venom of neonate and adult short-tailed pit vipers (Gloydius brevicaudus). Identified proteins were assigned to a few main toxin families. Disintegrin, phospholipase A2 (PLA2), serine proteinase, cysteine-rich secretory protein, C-type lectin-like protein, l-amino acid oxidase and snake venom metalloproteinase (SVMP) were detected in both venoms, while 5'-nucleotidase was detected only in the adult venom. SVMP was the predominant protein family in both venoms (neonate: 65.7%; adult: 64.4%), followed by PLA2 (neonate: 13.4%; adult: 25.0%). Antivenomic analysis revealed that commercial G. brevicaudus antivenom almost neutralized the chromatographic peaks with medium and high molecular masses in both venoms, but did not completely recognize peaks with low molecular mass. Toxicological and enzymatic activities show remarkable age-related variation in G. brevicaudus venom, probably resulting from variation in venom composition. Our data demonstrate age-related variation across venomics, antivenomics and biochemical profiles of G. brevicaudus venom, and have implications for the management of G. brevicaudus bites, including improving antivenom preparation by combining both venoms.

BIOLOGICAL SIGNIFICANCE

This study investigates the composition and biochemical activity of neonate and adult Gloydius brevicaudus venoms. We found remarkable age-related variation in venom biological activity, likely the result of variation in venom composition. Antivenomics analysis was used to explore difference in neonate and adult G. brevicaudus venoms. Our findings have implications for the diagnosis and clinical management of G. brevicaudus bites, and the design of venom mixtures that will increase the efficacy of commercial antivenom. This article is part of a Special Issue entitled: Proteomics of non-model organisms.

Snake venomics of Lachesis muta rhombeata and genus-wide antivenomics assessment of the paraspecific immunoreactivity of two antivenoms evidence the high compositional and immunological conservation across Lachesis

We report the proteomic analysis of the Atlantic bushmaster, Lachesis muta rhombeata, from Brazil. Along with previous characterization of the venom proteomes of L. stenophrys (Costa Rica), L. melanocephala (Costa Rica), L. acrochorda (Colombia), and L. muta muta (Bolivia), the present study provides the first overview of the composition and distribution of venom proteins across this wide-ranging genus, and highlights the remarkable similar compositional and pharmacological profiles across Lachesis venoms. The paraspecificity of two antivenoms, produced at Instituto Vital Brazil (Brazil) and Instituto Clodomiro Picado (Costa Rica) using different conspecific taxa in the immunization mixtures, was assessed using genus-wide comparative antivenomics. This study confirms that the proteomic similarity among Lachesis sp. venoms is mirrored in their high immunological conservation across the genus. The clinical and therapeutic consequences of genus-wide venomics and antivenomics investigations of Lachesis venoms are discussed.

BIOLOGICAL SIGNIFICANCE

The proteomics characterization of L. m. rhombeata venom completes the overview of Lachesis venom proteomes and confirms the remarkable toxin profile conservation across the five clades of this wide-ranging genus. Genus-wide antivenomics showed that two antivenoms, produced against L. stenophrys or L. m. rhombeata, exhibit paraspecificity towards all other congeneric venoms. Our venomics study shows that, despite the broad geographic distribution of the genus, monospecific antivenoms may achieve clinical coverage for any Lachesis sp. envenoming.