Identification of poorly immunodepleted phospholipase A2 (PLA2) proteins of Bungarus fasciatus venom from Assam, India and evaluation of Indian polyvalent antivenom using third-generation antivenomics

Bungarus fasciatus also referred to as the Banded krait is a snake which possesses venom and belongs to the Elapidae family. It is widely distributed across the Indian subcontinent and South East Asian countries and is responsible for numerous snakebites in the population. B. fasciatus possesses a neurotoxic venom and envenomation by the snake results in significant morbidity and occasional morbidity in the victim if not treated appropriately. In this study, the efficacy of Indian polyvalent antivenom (Premium Serums polyvalent antivenom) was evaluated against the venom of B. fasciatus from Guwahati, Assam (India) employing the Third-generation antivenomics technique followed by identification of venom proteins from three poorly immunodepleted peaks (P5, P6 and P7) using LC-MS/MS analysis. Seven proteins were identified from the three peaks and all these venom proteins belonged to the phospholipase A2 (PLA2) superfamily. The identified PLA2 proteins were corroborated by the in vitro enzymatic activities (PLA2 and Anticoagulant activity) exhibited by the three peaks and previous reports of pathological manifestation in the envenomated victims. Neutralization of enzymatic activities by Premium Serums polyvalent antivenom was also assessed in vitro for crude venom, P5, P6 and P7 which revealed moderate to poor inhibition. Inclusion of venom proteins/peptides, which are non-immunodepleted or poorly immunodepleted, into the immunization mixture of venom used for antivenom production may help in enhancing the efficacy of the polyvalent antivenom.

Venomics and antivenomics of the poorly studied Brazil's lancehead, Bothrops brazili (Hoge, 1954), from the Brazilian State of Pará

Background:

The Brazil’s lancehead, Bothrops brazili, is a poorly studied pit viper distributed in lowlands of the equatorial rainforests of southern Colombia, northeastern Peru, eastern Ecuador, southern and southeastern Venezuela, Guyana, Suriname, French Guiana, Brazil, and northern Bolivia. Few studies have been reported on toxins isolated from venom of Ecuadorian and Brazilian B. brazili. The aim of the present study was to elucidate the qualitative and quantitative protein composition of B. brazili venom from Pará (Brazil), and to carry out a comparative antivenomics assessment of the immunoreactivity of the Brazilian antibothropic pentavalent antivenom [soro antibotrópico (SAB) in Portuguese] against the venoms of B. brazili and reference species, B. jararaca.

Methods:

We have applied a quantitative snake venomics approach, including reverse-phase and two-dimensional electrophoretic decomplexation of the venom toxin arsenal, LC-ESI-MS mass profiling and peptide-centric MS/MS proteomic analysis, to unveil the overall protein composition of B. brazili venom from Pará (Brazil). Using third-generation antivenomics, the specific and paraspecific immunoreactivity of the Brazilian SAB against homologous (B. jararaca) and heterologous (B. brazili) venoms was investigated.

Results:

The venom proteome of the Brazil’s lancehead (Pará) is predominantly composed of two major and three minor acidic (19%) and two major and five minor basic (14%) phospholipase A₂ molecules; 7-11 snake venom metalloproteinases of classes PI (21%) and PIII (6%); 10-12 serine proteinases (14%), and 1-2 L-amino acid oxidases (6%). Other toxins, including two cysteine-rich secretory proteins, one C-type lectin-like molecule, one nerve growth factor, one 5'-nucleotidase, one phosphodiesterase, one phospholipase B, and one glutaminyl cyclase molecule, represent together less than 2.7% of the venom proteome. Third generation antivenomics profile of the Brazilian pentabothropic antivenom showed paraspecific immunoreactivity against all the toxin classes of B. brazili venom, with maximal binding capacity of 132.2 mg venom/g antivenom. This figure indicates that 19% of antivenom's F(ab')₂ antibodies bind B. brazili venom toxins.

Conclusion:

The proteomics outcome contribute to a deeper insight into the spectrum of toxins present in the venom of the Brazil’s lancehead, and rationalize the pathophysiology underlying this snake bite envenomings. The comparative qualitative and quantitative immunorecognition profile of the Brazilian pentabothropic antivenom toward the venom toxins of B. brazili and B. jararaca (the reference venom for assessing the bothropic antivenom's potency in Brazil), provides clues about the proper use of the Brazilian antibothropic polyvalent antivenom in the treatment of bites by the Brazil’s lancehead.

Defining the pathogenic threat of envenoming by South African shield-nosed and coral snakes (genus Aspidelaps), and revealing the likely efficacy of available antivenom

While envenoming by the southern African shield-nosed or coral snakes (genus Aspidelaps) has caused fatalities, bites are uncommon. Consequently, this venom is not used in the mixture of snake venoms used to immunise horses for the manufacture of regional SAIMR (South African Institute for Medical Research) polyvalent antivenom. Aspidelaps species are even excluded from the manufacturer's list of venomous snakes that can be treated by this highly effective product. This leaves clinicians, albeit rarely, in a therapeutic vacuum when treating envenoming by these snakes. This is a significantly understudied small group of nocturnal snakes and little is known about their venom compositions and toxicities. Using a murine preclinical model, this study determined that the paralysing toxicity of venoms from Aspidelaps scutatus intermedius, A. lubricus cowlesi and A. l. lubricus approached that of venoms from highly neurotoxic African cobras and mambas. This finding was consistent with the cross-genus dominance of venom three-finger toxins, including numerous isoforms which showed extensive interspecific variation. Our comprehensive analysis of venom proteomes showed that the three Aspidelaps species possess highly similar venom proteomic compositions. We also revealed that the SAIMR polyvalent antivenom cross-reacted extensively in vitro with venom proteins of the three Aspidelaps. Importantly, this cross-genus venom-IgG binding translated to preclinical (in a murine model) neutralisation of A. s. intermedius venom-induced lethality by the SAIMR polyvalent antivenom, at doses comparable with those that neutralise venom from the cape cobra (Naja nivea), which the antivenom is directed against. Our results suggest a wider than anticipated clinical utility of the SAIMR polyvalent antivenom, and here we seek to inform southern African clinicians that this readily available antivenom is likely to prove effective for victims of Aspidelaps envenoming. BIOLOGICAL SIGNIFICANCE: Coral and shield-nosed snakes (genus Aspidelaps) comprise two species and several subspecies of potentially medically important venomous snakes distributed in Namibia, Botswana, Zimbabwe, Mozambique and South Africa. Documented human fatalities, although rare, have occurred from both A. lubricus and A. scutatus. However, their venom proteomes and the pathological effects of envenomings by this understudied group of nocturnal snakes remain uncharacterised. Furthermore, no commercial antivenom is made using venom from species of the genus Aspidelaps. To fill this gap, we have conducted a transcriptomics-guided comparative proteomics analysis of the venoms of the intermediate shield-nose snake (A. s. intermedius), southern coral snake (A. l. lubricus), and Cowle's shield snake (A. l. cowlesi); investigated the mechanism of action underpinning lethality by A. s. intermedius in the murine model; and assessed the in vitro immunoreactivity of the SAIMR polyvalent antivenom towards the venom toxins of A. l. lubricus and A. l. cowlesi, and the in vivo capability of this antivenom at neutralising the lethal effect of A. s. intermedius venom. Our data revealed a high degree of conservation of the global composition of the three Aspidelaps venom proteomes, all characterised by the overwhelming predominance of neurotoxic 3FTxs, which induced classical signs of systemic neurotoxicity in mice. The SAIMR polyvalent antivenom extensively binds to Aspidelaps venom toxins and neutralised, with a potency of 0.235 mg venom/mL antivenom, the lethal effect of A. s. intermedius venom. Our data suggest that the SAIMR antivenom could be a useful therapeutic tool for treating human envenomings by Aspidelaps species.

Toxin-resolved antivenomics-guided assessment of the immunorecognition landscape of antivenoms

Snakebite envenoming represents a major issue in rural areas of tropical and subtropical regions across sub-Saharan Africa, South to Southeast Asia, Latin America and Oceania. Antivenoms constitute the only scientifically validated therapy for snakebite envenomings, provided they are safe, effective, affordable, accessible and administered appropriately. However, the lack of financial incentives in a technology that has remained relatively unchanged for more than a century, has contributed to some manufacturers leaving the market and others downscaling production or increasing the prices, leading to a decline in the availability and accessibility for these life-saving antidotes to millions of rural poor most at risk from snakebites in low income countries. The shortage of antivenoms can be significantly alleviated by optimizing the use of current antivenoms (through the assessment of their specific and paraspecific efficacy against the different medically relevant homologous and heterologous snake venoms) and by generating novel polyspecific antivenoms exhibiting broad clinical spectrum and wide geographic distribution range. Research on venoms has been continuously enhanced by advances in technology. Particularly, the last decade has witnessed the development of omics strategies for unravelling the toxin composition of venoms ("venomics") and to assess the immunorecognition profile of antivenoms ("antivenomics"). Here, we review recent developments and reflect on near future innovations that promise to revolutionize the mutually enlightening relationship between evolutionary and translational venomics.