Snakebite accidents, neglected tropical diseases per the WHO, pose a significant public health threat due to their severity and frequency. Envenomation by Bothrops genus snakes leads to severe manifestations due to proteolytic enzymes. While the antibothropic serum produced by the Butantan Institute saves lives, its efficacy is limited as it fails to neutralize certain serine proteases. Hence, developing new-generation antivenoms, like monoclonal antibodies, is crucial. This study aimed to explore the inhibitory potential of synthetic peptides homologous to the CDR3 regions of a monoclonal antibody targeting a snake venom thrombin-like enzyme (SVTLE) from B. atrox venom. Five synthetic peptides were studied, all stable against hydrolysis by venoms and serine proteases. Impressively, four peptides demonstrated uncompetitive SVTLE inhibition, with Ki values ranging from 10⁻⁶ to 10⁻⁷ M. These findings underscore the potential of short peptides homologous to CDR3 regions in blocking snake venom toxins, suggesting their promise as the basis for new-generation antivenoms. Thus, this study offers potential advancements in combatting snakebites, addressing a critical public health challenge in tropical and subtropical regions.

A comprehensive LC-MS study examined the venom components of the solitary scoliid wasp Scolia oculata. Online mass fingerprinting showed that crude venom contains 25 small molecules (amino acids, biogenic amines, and nucleosides/nucleotides) and 45 peptides with MW 400-2700. The small molecules were identified by elemental composition analysis, and peptide sequences were determined by ESI-MS/MS and MALDI-TOF/TOF MS analyses. As major peptide components, a known peptide, β-scoliidine (DYVTVKGFSPLRKA), and three new peptides, γ-scoliidine (YVTVKGFSPLR), δ-scoliidine (YVTVKGFSPLREP) and ε-scoliidine (DYVTVKGFSPLREP) were identified, all of which are closely homologous to each other. Once the neuroprotective effects of β-scoliidine have already been described, the other three new scoliidine peptides were analyzed against oxidative stress-induced toxicity in PC12 neuronal cells by mitochondrial metabolism assay, and the structure-activity relationship was evaluated. Interestingly, pre-treatment with ε-scoliidine increased the mitochondrial metabolism of PC12 cells (106 ± 3.6%; p = 0.007) exposed to H₂O₂-induced oxidative stress in contrast to γ- and δ-scoliidines (77.6 ± 4.8 and 68.5 ± 4.1%, respectively) in compared to cells treated only H₂O₂ (75.8 ± 2.4%). These new peptides were also analyzed for enzyme inhibitor/substrate assays with angiotensin-converting enzyme (ACE), neprilysin (NEP), and acetylcholinesterase (AChE). In these assays, only δ- and ε-scoliidines increased the AChE activity (128.7 ± 3.8%; p = 0.01; and 116.8 ± 3.8% p = 0.03; respectively) in relation to basal activity (100.1 ± 1.6%). In addition, the four peptides were analyzed through in silico analysis, and none of them demonstrated possible hemolytic and toxic activities. In our study, the comprehensive LC-MS and MS/MS analyses of Scolia oculate venom identified four major peptide components of the venom β-, γ-, δ- and ε-scoliidines, and small differences in their primary structures are important to their neuroprotective properties.

With the development of biotechnology, vaccines changed from whole attenuated microorganisms to purified or recombinant subunits, or fragments of nucleic acids, bringing the need of immunostimulatory molecules to ensure immunogenicity. Pro-inflammatory molecules that activate antigen-presenting cells (APCs) are potential candidates for the development of new immunostimulatory molecules. Due to its pro-inflammatory properties, Bothrops venoms are a likely source of these molecules. Herein, we obtained seven fractions of Bothrops jararacussu (B. jararacussu) venom, which were tested in cultures of murine peritoneal macrophages. All the fractions exerted significant immunostimulatory effect for at least one cytokine analyzed, but the low molecular weight fraction (Fr7) was the only one that increased the production of the pro-inflammatory mediators tumor necrosis factor (TNF), interleukin (IL)-6, monocyte chemoattractant protein-1 (MCP-1) and IL-1β, at a low sub-toxic concentration (5 μg/mL). This fraction was selected to evaluate whether it would be able to modulate murine peritoneal cells in vivo. Fr7 recruited activated APCs in vivo, including macrophages and subpopulations of dendritic cells and B1 cells, and also promoted the expansion and/or activation of adaptive immune cells, including TCD4, TCD8 and B2 lymphocytes. The molecular content of Fr7 was preliminary investigated by MALDI-TOF analysis, with molecular masses compatible with peptides and phospholipases A₂. Initial steps of purification were also performed using HPLC. Two subfractions provided interesting results that deserve further investigation, aiming to obtain a purified molecule with immunostimulatory effects and to explore its mechanism of action.