Engineered protein containing crotoxin epitopes induces neutralizing antibodies in immunized rabbits

Development and evaluation of a recombinant multi-epitopic protein (TsMEP) as an antigen candidate for Tityus serrulatus antivenom production

Scorpionism is Brazil's most prevalent envenomation. Treatment typically involves the use of heterologous antivenoms derived from the immunization of horses with crude T. serrulatus venom (TsV). Due to the high toxicity of this immunogen, as well as the particular challenges associated with the use of venoms as antigens, there is interest in exploring new alternatives for reducing their use in antivenom production. In this study, ten linear B-cell epitopes from hyaluronidase and voltage-gated sodium channel toxins, previously identified using the SPOT-synthesis method, were selected to construct a recombinant chimeric MultiEpitopic Protein from T. serrulatus scorpion venom (TsMEP). We demonstrated that TsMEP is non-toxic, and antibodies elicited in rabbits against this antigen exhibited reactivity in ELISA with Brazilian T. serrulatus, T. bahiensis, T. obscurus, and T. stigmurus venoms, as well as with Peruvian Hadruroides lunatus and North African Androctonus australis hector scorpion venoms. In vivo and in vitro neutralization assays revealed that rabbit anti-TsMEP antibodies partially neutralize the hyaluronidase activity of T. serrulatus venom and its lethality. Data presented here suggests that this multiepitopic protein could be a promising candidate in experimental immunization approaches for antivenom production for clinical use against Tityus spp. venoms.

Structural, biochemical and immunochemical characterization of an acidic phospholipase A2 from Lachesis acrochorda (Viperidae: Crotalinae) venom

Viperids of the genus Lachesis, also known as bushmasters, are capable of injecting great amounts of venom that cause severe envenomation incidents. Since phospholipases type A2 are mainly involved in edema and myonecrosis within the snakebite sites, in this work, the isolation, amino acid sequence and biochemical characterization of the first phospholipase type A2 from the venom of Lachesis acrochorda, named Lacro_PLA2, is described. Lacro_PLA2 is an acidic aspartic 49 calcium-dependent phospholipase A2 with 93% similarity to the L. stenophrys phospholipase. Lacro_PLA2 has a molecular mass of 13,969.7 Da and an experimental isoelectric point around 5.3. A combination of N-terminal Edman degradation and MS/MS spectrometry analyses revealed that Lacro_PLA2 contains 122 residues including 14 cysteines that form 7 disulfide bridges. A predicted 3D model shows a high resemblance to other viperid phospholipases. Nevertheless, immunochemical and phospholipase neutralization tests revealed a notorious level of immunorecognition of the isolated protein by two polyclonal antibodies from viperids from different genus, which suggest that Lacro_PLA2 resembles more to bothropic phospholipases. Lacro_PLA2 also showed significantly high edema activity when was injected into mice; so, it could be an alternative antigen in the development of antibodies against toxins of this group of viperids, seeking to improve commercial polyclonal antivenoms.

Crotoxin B: Heterologous Expression, Protein Folding, Immunogenic Properties, and Irregular Presence in Crotalid Venoms

Crotoxin complex CA/CB and crotamine are the main toxins associated with Crotalus envenomation besides the enzymatic activities of phospholipases (PLA₂) and proteases. The neutralization at least of the crotoxin complex by neutralizing the subunit B could be a key in the production process of antivenoms against crotalids. Therefore, in this work, a Crotoxin B was recombinantly expressed to evaluate its capacity as an immunogen and its ability to produce neutralizing antibodies against crotalid venoms. A Crotoxin B transcript from Crotalus tzabcan was cloned into a pCR^®2.1-TOPO vector (Invitrogen, Waltham, MA, USA) and subsequently expressed heterologously in bacteria. HisrCrotoxin B was extracted from inclusion bodies and refolded in vitro. The secondary structure of HisrCrotoxin B was comparable to the secondary structure of the native Crotoxin B, and it has PLA₂ activity as the native Crotoxin B. HisrCrotoxin B was used to immunize rabbits, and the obtained antibodies partially inhibited the activity of PLA₂ from C. tzabcan. The anti-HisrCrotoxin B antibodies neutralized the native Crotoxin B and the whole venoms from C. tzabcan, C. s. salvini, and C. mictlantecuhtli. Additionally, anti-HisrCrotoxin B antibodies recognized native Crotoxin B from different Crotalus species, and they could discriminate venom in species with high or low levels of or absence of Crotoxin B.

Biological and proteomic characterization of the venom from Peruvian Andes rattlesnake Crotalus durissus

The Peruvian rattlesnake Crotalus durissus is a venomous species that is restricted to the Peruvian Departments of Puno and Madre de Dios. Although clinically meaningful in this region, Crotalus durissus venom composition remains largely elusive. In this sense, this work aimed to provide a primary description of Peruvian C. durissus venom (PCdV). The enzymatic activities (SVMP, SVSP, LAAO, Hyaluronidase and PLA₂) of PCdV were analyzed and compared to Brazilian Crotalus durissus terrificus venom (BCdtV). PCdV showed higher PLA₂ activity when compared to the Brazilian venom. PCdV also showed cytotoxicity in VERO cells. For proteomic analysis, PCdV proteins were separated by HPLC, followed by SDS-PAGE. Gel bands were excised and tryptic digested for MALDI-TOF/TOF identification. Approximately 21 proteins were identified, belonging to 7 families. Phospholipases A₂ (PLA₂, 66.63%) were the most abundant proteins of the venom, followed by snake venom serine proteinases (SVSPs, 13.37%), C-type lectins (Snaclec, 8.98%) and snake venom metalloproteinases (SVMPs, 7.13%), crotamine (2.98%) and phosphodiesterase (PDE, 0.87%). Moreover, antivenom recognition assays indicated that both Brazilian and Peruvian antivenoms recognize PCdV, indicating the presence of antigenically related proteins in crotalic venoms. The results reported here, may impact in the venom selection for the production of effective Pan-American crotalic antivenom.

Amazonian scorpions and scorpionism: integrating toxinological, clinical, and phylogenetic data to combat a human health crisis in the world's most diverse rainfores

Venom from Amazonian scorpions of the genus Tityus contains components capable of eliciting a distinct clinical, mostly neurological, syndrome. This contrasts with the mainly autonomic manifestations produced after envenomation by congeneric southern and northern South American species. Herein, we summarize Pan-Amazonian scorpionism by synthesizing available toxinological, clinical, and molecular data gathered from all affected areas in Amazonia, including Brazil, Ecuador, Colombia, Peru, Venezuela, and French Guiana. We searched multiple databases, as well as our own records, for reports of scorpion envenomations in Amazonia by confirmed Tityus spp., and compared the clinical manifestations. To help uncover clinical and venom relationships among problematic species, we explored phylogenetic relationships with a rate-calibrated analysis of mitochondrial COI data from available species. The possible existence of diversity gradients for venom toxic and immunogenic components despite the predicted strong phylogenetic association among species is underscored by discussed clinical and toxinological findings. A multicentric effort, involving all nations affected by this neglected disease, is urgently needed to offer alternatives for treating and understanding this pathology, including the preparation of neutralizing antibodies with a broad range of efficacy.