Characterization, crystallization and preliminary X--ray diffraction analysis of acutohaemolysin, a haemolytic toxin from Agkistrodon acutus venom

Comparative analysis of Deinagkistrodon acutus venom from Taiwan and China utilizing chromatographic, electrophoretic, and bioinformatic approaches, along with ELISA employing a monospecific antivenom

Deinagkistrodon acutus is a medically important pitviper inhabiting mainly South China and Taiwan. The hemorrhagic effects of its envenoming are compatible to its venom, which is abundant in metalloproteases (svMPs) and C-type lectin-like proteins. In this study, we investigated geographic variations in the venom of D. acutus collected from Taiwan and four Mainland Chinese provinces: Fujian, Jiangxi, Anhui, and Hunan. The variations were assessed through high-performance liquid chromatography, non-metric multidimensional scaling analysis, gel electrophoresis, and enzyme-linked immunosorbent assay (ELISA) with a monospecific antivenom (DaMAV) generated against the Taiwanese D. acutus venom, and discussed based on venom-protein sequences in databases and literature related to D. acutus venom. Additionally, the cross-reactivity of DaMAV against Crotalus horridus and Calloselasma rhodostoma venoms was investigated. We noted differential abundances of D. acutus venom metalloproteases, C-type lectin-like proteins, and phospholipase A2, along with point mutations and selective expression of serine protease isoforms. The ELISA results revealed that the venom from Taiwan was more reactive toward Taiwanese DaMAV than the four Mainland Chinese venoms, consistent with chromatographic profile differences, whereas C. horridus venom presented moderate cross-reactivity with DaMAV. The observed immunoreactivities of these venom with DaMAV can be attributed to the high prevalence of their PIII-svMPs, which are the dominant antigens, and the conservation of PIII-svMP epitopes.

Sharp-nosed Pit Viper (Deinagkistrodon acutus) from Taiwan and China: A comparative study on venom toxicity and neutralization by two specific antivenoms across the Strait

In East Asia, the Sharp-nosed Pit Viper (Deinagkistrodon acutus) is a medically important venomous snake in Taiwan and China, two geographical areas long separated by the Taiwan Strait. Yet, snake venom variation is little known between specimens found across the Strait. This study thus investigated the intra-species variation of D. acutus venoms from Taiwan (Da-Taiwan) and China (Da-China) in their profiles of gel electrophoresis, toxicity, immunoreactivity and neutralization effect by antivenom. Da-China venom exhibited higher procoagulant, hemorrhagic and lethal activities than Da-Taiwan venom, presumably attributed to the higher abundance of moderate-to-high molecular weight toxins (procoagulants and hemorrhagins) in the venom. The mono-specific antivenoms produced in Taiwan (DaMAV-Taiwan) and China (DaMAV-China) were immunoreactive toward both venoms, and were able to neutralize the venom toxicity to different extents. DaMAV-Taiwan was more efficacious in neutralizing the venom procoagulant and lethal effects, while DaMAV-China was more potent against hemorrhagic effect. The discrepancy in efficacy between the two antivenoms could be due to varying proportions of neutralizing antibodies in the respective products, influenced by techniques of antibody raising and purification. Further study is warranted to elucidate variation in the proteome and antigenicity of D. acutus venom between snakes from Taiwan and China.

Snake venom proteome and immuno-profiling of the hundred-pace viper, Deinagkistrodon acutus, in Taiwan

Deinagkistrodon acutus, also known as the hundred-pace viper or Chinese moccasin, is a clinically significant venomous snake in Taiwan. To address the lack of knowledge on the venom proteome of D. acutus, the venom composition was studied by a bottom-up proteomic approach combining reverse phase high-performance liquid chromatography, SDS-PAGE, and LC-MS/MS analysis. The immunoreactivity and cross-reactivity of Taiwanese freeze-dried D. acutus antivenom (DA-AV) and hemorrhagic antivenom (FH-AV) were investigated, as well. The proteomic analysis revealed the presence of 29 distinct proteins from D. acutus venom belonging to 8 snake venom protein families. Snake venom metalloproteinase (SVMP, 46.86%), C-type lectin (CLEC, 37.59%), phospholipase A₂ (PLA₂, 7.33%) and snake venom serine protease (SVSP, 6.62%) were the most abundant proteins. In addition to DA-AV, FH-AV also showed a profile of broad immunorecognition toward the venom of D. acutus. Remarkably, both antivenoms specifically reacted with the HPLC fractions containing SVMPs, and the titer was 5-10 times higher than fractions of other components. This information helps us to deeply understand the pathophysiology of D. acutus envenomation and guide us to development of more effective antivenom for clinical treatment.

The crystal structure of a novel, inactive, lysine 49 PLA2 from Agkistrodon acutus venom: an ultrahigh resolution, AB initio structure determination

The crystal structure of acutohaemolysin, a lysine 49 phospholipase A2 protein with 1010 non-hydrogen protein atoms and 232 water molecules, has been determined ab initio using the program SnB at an ultrahigh resolution of 0.8 A. The lack of catalytic activity appears to be related to the presence of Phe102, which prevents the access of substrate to the active site. The substitution of tryptophan for leucine at residue 10 interferes with dimer formation and may be responsible for the additional loss of hemolytic activity. The ultrahigh resolution of the experimental diffraction data permits alternative conformations to be modeled for disordered residues, many hydrogen atoms to be located, the protonation of the Nepsilon2 atom in the catalytic residue His48 to be observed experimentally, and the density of the bonding electrons to be analyzed in detail.