Bothrops bilineatus: An Arboreal Pitviper in the Amazon and Atlantic Forest

Throughout evolution, numerous proteins have been convergently recruited into the venoms of various animals, including centipedes, cephalopods, cone snails, fish, insects (several independent venom systems), platypus, scorpions, shrews, spiders, toxicoferan reptiles (lizards and snakes), and sea anemones. The protein scaffolds utilized convergently have included AVIT/colipase/prokineticin, CAP, chitinase, cystatin, defensins, hyaluronidase, Kunitz, lectin, lipocalin, natriuretic peptide, peptidase S1, phospholipase A(2), sphingomyelinase D, and SPRY. Many of these same venom protein types have also been convergently recruited for use in the hematophagous gland secretions of invertebrates (e.g., fleas, leeches, kissing bugs, mosquitoes, and ticks) and vertebrates (e.g., vampire bats). Here, we discuss a number of overarching structural, functional, and evolutionary generalities of the protein families from which these toxins have been frequently recruited and propose a revised and expanded working definition for venom. Given the large number of striking similarities between the protein compositions of conventional venoms and hematophagous secretions, we argue that the latter should also fall under the same definition.

As more data are generated from proteome and transcriptome analyses of snake venoms, we are gaining an appreciation of the complexity of the venoms and, to some degree, the various sources of such complexity. However, our knowledge is still far from complete. The translation of genetic information from the snake genome to the transcriptome and ultimately the proteome is only beginning to be appreciated, and will require significantly more investigation of the snake venom genomic structure prior to a complete understanding of the genesis of venom composition. Venom complexity, however, is derived not only from the venom genomic structure but also from transcriptome generation and translation and, perhaps most importantly, post-translation modification of the nascent venom proteome. In this review, we examine the snake venom metalloproteinases, some of the predominant components in viperid venoms, with regard to possible synthesis and post-translational mechanisms that contribute to venom complexity. The aim of this review is to highlight the state of our knowledge on snake venom metalloproteinase post-translational processing and to suggest testable hypotheses regarding the cellular mechanisms associated with snake venom metalloproteinase complexity in venoms.

Bothrops asper inflicts the majority of snakebites in Central America and in the northern regions of South America, mostly affecting young agricultural workers in rural settings. This species is capable of provoking severe envenomings associated with local and systemic manifestations. The main clinical features are: local edema, ecchymoses, blisters, dermonecrosis, myonecrosis, defibrinogenation, thrombocytopenia, systemic bleeding, hypotension and renal alterations. In addition, soft-tissue infection, acute renal failure, compartmental syndrome, central nervous system hemorrhage and, in pregnant women, abortion, fetal wastage and abruptio placentae have been described as complications. Intravenous administration of antivenom constitutes the mainstay in the therapy. Antivenoms composed of either whole IgG or F(ab')(2) fragments, manufactured in Brazil, Colombia, Costa Rica and Mexico, have been tested in controlled clinical trials, and rational protocols for antivenom administration have been developed. In addition to antivenom therapy, a number of ancillary interventions are recommended in the treatment of B. asper bites.