Colombini Mônica, Rocha Anderson M, Freitas-de-Sousa Luciana A, Chaves Alison F A, Serrano Solange M T, Souza Vinicius C, Viala Vincent L, Junqueira-Azevedo Inácio L M, Cerni Felipe A, Sartim Marco A, Sachett Jacqueline A G, Monteiro Wuelton M, Grazziotin Felipe G, Wen Fan Hui, Pucca Manuela B, Moura-da-Silva Ana M
Laboratório de Imunopatologia, Instituto Butantan, São Paulo, Brazil.
Departamento de Ensino e Pesquisa, Fundação de Medicina Tropical Doutor Heitor Vieira Dourado, Manaus, Brazil.
PLoS Negl Trop Dis. 2025 Aug 1;19(8):e0013296. doi: 10.1371/journal.pntd.0013296. eCollection 2025 Aug.
Phenotypic polymorphism in rattlesnake venoms is well-documented, with a dichotomy between hemorrhagic (Type I) and neurotoxic (Type II) venoms. In South America, the Type II phenotype is predominant; however, evidence of Type I venom in Crotalus durissus ruruima raises concerns about the efficacy of the Crotalus antivenom, which is prepared only with Type II venoms. Consequently, the Bothrops-Crotalus antivenom has been proposed as an alternative treatment for envenomation by Type I venoms.
METHODOLOGY/PRINCIPAL FINDINGS: This study characterizes the dichotomy of C. d. ruruima venom by analyzing the structure of isoforms differentially expressed in Type I and Type II venoms, assessing their biological activities, and evaluating the implications for snakebite clinical management in Roraima State (northern Brazil). Four toxins were differentially expressed between Type I and Type II venoms: two PIII-class SVMPs, predominantly found in Type I venoms, associated with proteolytic and hemorrhagic activity; and two PLA2s, corresponding to Crotoxin A and B chains, prevalent in Type II venoms and related to elevated phospholipase A2 activity, myotoxicity, and increased lethality. The structure of Crotoxin chains was well conserved compared to C. d. terrificus Crotoxin. However, the SVMP sequences exhibited multiple substitutions in functional and immunoreactive regions compared to Bothropasin, resulting in low hemorrhagic activity and limited reactivity/neutralization by the Bothrops antivenom. Conversely, the Crotalus antivenom reacted with high antibody titer and neutralized all activities of both venom subtypes, except for the low hemorrhagic activity induced by Type I venoms.
CONCLUSIONS/SIGNIFICANCE: The efficacy of Bothrops antivenom in snakebites caused by rattlesnakes with Type I venoms remains uncertain. We advocate for a clinical study in Roraima to assess patient outcomes and benefits of Bothrops-Crotalus versus Crotalus antivenoms for these accidents. Meanwhile, administering Bothrops-Crotalus antivenom may be acceptable; however, caution is needed regarding the use of heterologous Bothrops antibodies, which have limited efficacy in treating Crotalus envenomation.
响尾蛇毒液的表型多态性已有充分记录，出血性（I型）毒液和神经毒性（II型）毒液之间存在二分法。在南美洲，II型表型占主导；然而，杜氏响尾蛇鲁氏亚种（Crotalus durissus ruruima）中存在I型毒液的证据引发了对仅用II型毒液制备的响尾蛇抗蛇毒血清疗效的担忧。因此，提出用矛头蝮 - 响尾蛇抗蛇毒血清作为I型毒液中毒的替代治疗方法。
方法/主要发现：本研究通过分析I型和II型毒液中差异表达的同工型结构、评估其生物学活性以及评估对巴西北部罗赖马州蛇咬伤临床管理的影响，来表征杜氏响尾蛇鲁氏亚种毒液的二分法。I型和II型毒液之间有四种毒素差异表达：两种PIII类蛇毒金属蛋白酶（SVMP），主要存在于I型毒液中，与蛋白水解和出血活性相关；以及两种磷脂酶A2（PLA2），分别对应于响尾蛇毒素A链和B链，在II型毒液中普遍存在，与磷脂酶A2活性升高、肌毒性和致死率增加有关。与杜氏响尾蛇恐怖亚种（C. d. terrificus）的响尾蛇毒素相比，响尾蛇毒素链的结构保存良好。然而，与矛头蝮蛇毒蛋白酶（Bothropasin）相比，SVMP序列在功能和免疫反应区域表现出多个替换，导致出血活性低，且被矛头蝮抗蛇毒血清的反应性/中和作用有限。相反，响尾蛇抗蛇毒血清以高抗体效价反应并中和了两种毒液亚型的所有活性，但I型毒液诱导的低出血活性除外。
结论/意义：矛头蝮抗蛇毒血清对I型毒液引起的响尾蛇咬伤的疗效仍不确定。我们主张在罗赖马州进行一项临床研究，以评估矛头蝮 - 响尾蛇抗蛇毒血清与响尾蛇抗蛇毒血清对这些咬伤事故的患者预后和益处。同时，使用矛头蝮 - 响尾蛇抗蛇毒血清可能是可以接受的；然而，对于使用异源的矛头蝮抗体需要谨慎，因为它们在治疗响尾蛇中毒方面疗效有限。
