Table 1.
Details of D. russelii venom samples.
Fig 1.
Map of India, prepared with QGIS 3.8.2 [35], depicts (A) sampling locations and (B) SDS-PAGE profiles of D. russelii venoms.
M: Protein marker (units in kDa); PB: Punjab; TN: Tamil Nadu; AP: Andhra Pradesh; WB: West Bengal; MH: Maharashtra; MP: Madhya Pradesh.
Fig 2.
Venom variability in pan-Indian D. russelii populations.
This figure depicts RP-HPLC profiles of D. russelii venoms sourced from distinct biogeographic zones. Venom profiles, shown here, highlight the considerable differences in the protein compositions of geographically distinct populations. The area under the curve for all labelled and uniquely colour coded fraction peaks are depicted in the corresponding doughnut charts.
Fig 3.
Comparative venom profiles of the biogeographically disparate D. russelii populations.
This figure represents the relative composition of various toxins constituting D. russelii venoms, as estimated from the mass spectrometry and HPLC data. Each toxin type is uniquely colour coded, and its relative abundance is indicated.
Fig 4.
Coagulopathies induced by the biogeographically distinct populations of D. russelii.
Heatmaps depict the influence of D. russelii venoms in impeding the (A) extrinsic and (B) intrinsic blood coagulation pathways, respectively. (C) The impact of varying concentrations of venoms (15.6 to 250 ng) on plasma clotting time (mins), and the ability of Premium Serums antivenom (1:4 dilution of 1 mg/ml or 0.25 μg/μl antivenom) in neutralising these effects are shown as bar graphs. The error bars represent the standard deviation among the replicates. (D) Haemolytic activities of D. russelii venoms have also been shown. Numbers inside each tile in A and B denote the plasma clotting time in seconds, and the numbers in D indicate the percentage of relative activity with respect to the positive control (0.5% Triton X). Blank: plasma control; ASV Blank: plasma + antivenom (1:4); NC: negative control; PB: Punjab; TN: Tamil Nadu; AP: Andhra Pradesh; WB: West Bengal; MH: Maharashtra; MP: Madhya Pradesh.
Fig 5.
Immunological cross-reactivity of commercial Indian antivenoms against the pan-Indian populations of D. russelii venoms.
Heatmaps, shown here, quantify the binding of commercial Indian antivenoms to the venoms of pan-Indian populations of D. russelii. Multiple dilutions of antivenoms (1:500, 1:2500 and 1:12500) were tested in indirect ELISA experiments. Non-specific binding of naive horse IgGs (1:4 dilution) to Daboia venoms is also shown in the first plate for reference. A gradient colour scale has been shown indicating the degree of binding from low (black) to high (cream). PB: Punjab; TN: Tamil Nadu; AP: Andhra Pradesh; WB: West Bengal; and MH: Maharashtra; MP: Madhya Pradesh.
Fig 6.
Venom potencies of the pan-Indian populations of D. russelii and the neutralisation potencies of the Premium Serums antivenom.
This figure depicts (A) venom potencies (mg/kg) of various D. russelii populations and (B) the neutralising potencies (mg/ml) of the Premium Serums antivenom against them. The error bars show 95% confidence intervals, and the marketed neutralising potency (0.60 mg/ml) of the commercial product against D. russelii venom is shown as a vertical dotted line (panel B).
Fig 7.
The preclinical inefficacy of Indian antivenom therapy in snakebite hotspots.
This figure depicts the alarming preclinical ineffectiveness of commercial antivenoms in the major snakebite hotspots of India (highlighted in red circles). The relative differences in neutralisation potencies of antivenoms against the geographically distinct populations of N. naja (green vials) [71], D. russelii (yellow vials) and B. caeruleus (purple vial) [20] are shown in comparison to the venom source (for antivenom production) population in southern India. The red dotted lines on vials represent the marketed neutralising potency of the commercial products. Sampling locations have been indicated with uniquely coloured markers (top right box) on the biogeographical map of India that was prepared with QGIS 3.8.2 [35]. The intensity of purple clouds on the map is indicative of the estimated standardised snakebite death rates per million reported by Suraweera et al. 2020 [2], with the brighter regions representing the major hotspots.