Venom Concentrations and Clotting Factor Levels in a Prospective Cohort of Russell’s Viper Bites with Coagulopathy

Background Russell’s viper envenoming is a major problem in South Asia and causes venom induced consumption coagulopathy. This study aimed to investigate the kinetics and dynamics of venom and clotting function in Russell’s viper envenoming. Methodology/Principal Findings In a prospective cohort of 146 patients with Russell’s viper envenoming, we measured venom concentrations, international normalised ratio [INR], prothrombin time (PT), activated partial thromboplastin time (aPTT), coagulation factors I, II, V, VII, VIII, IX and X, and von Willebrand factor antigen. The median age was 39y (16–82y) and 111 were male. The median peak INR was 6.8 (interquartile range[IQR]:3.7 to >13), associated with low fibrinogen [median,13), associated with low fibrinogen [median,3 at 6h post-antivenom but had reduced to Conclusions Russell’s viper coagulopathy results in prolonged aPTT, INR, low fibrinogen, factors V, VIII and X which recover over 48h. Severity of clotting abnormalities was associated with venom concentrations

Variable plasma levels of Factor V Leiden correlate with circulating platelet microparticles in carriers of Factor V Leiden

Introduction: Inheritance of Factor V Leiden (FVL) is associated with an increased but variable level of risk for thrombosis. We have previously shown that FVL heterozygotes have elevated levels of circulating pro-coagulant microparticles (MP). Here we sought to determine if these subjects differed in their plasma levels of FVL and if this was related to MP concentrations and/or history of thrombosis. Materials and Methods: The Hemoclot Quanti. V-L clotting assay was used to specifically measure FVL in plasma samples from 44 known carriers (12 M, 32 F; aged 46 ± 13 years). Circulating MP were quantified by flow cytometry using fluorochrome conjugated antibodies to platelet (CD41a), leukocyte (CD45), and endothelial (CD62e) surface markers, and MP prothrombinase activity was determined by ELISA. Results: The cohort was found to have a mean FVL of 49.5 ± 5.6% and this was positively correlated to the total number of circulating CD41a + MP (R = 0.31, p = 0.03) but not to other MP subsets or to MP prothrombinase activity. The amount of FVL relative to normal factor V (FVL/FV clotting ratio) was calculated and found to be highly variable, ranging from 0.37 to 0.69, and significantly correlated with a history of thrombosis (n = 14; p = 0.04). Conclusions: This is the first study to investigate the relationship between varying levels of FVL and plasma derived MP. These results are consistent with our previous findings of an increase in MP levels in carriers of FVL as compared to controls, and suggest a role for FVL/FV ratio in predicting risk of thrombosis in carriers of FVL

Circulating microparticles are elevated in carriers of Factor V Leiden

Microparticles (MP) are small membrane bound cellular particles that play an important role in thrombosis. This study was carried out to evaluate if increased numbers or procoagulant potential of circulating MP contribute to the heterogeneity in occurrence of thrombosis in heterozygotes carrying Factor V Leiden (FVL) mutation. Levels of circulating platelet (CD41a), endothelial (CD62e) as well as leukocyte (CD45) derived MP from 45 FVL heterozygous individuals were enumerated by flow cytometry and compared with normal controls. Functional studies included enzyme linked immunoassay based prothrombinase activity (ELISA) and modified dilute Russell Viper venom test (DRVVT). Circulating MP were significantly higher in the FVL cohort compared to the controls (median = 2100 vs. 1508 MP/μl, respectively p = 0.0021).All subsets of MP (platelet, endothelial and leukocyte) were significantly elevated in the FVL group, the most striking disparity seen in the number of CD45 positive leukocyte MP. Despite the differences in the number of MP between the controls and FVL cohorts, there was no significant difference in the prothrombinase activity recorded by the ELISA (2.0 vs 2.4 PS equivalents; p = 0.7374) or clotting time assessed by the DRVVT (47 vs 46 sec, p = 0.8118). When the FVL cohort was considered alone there was no significant difference in MP parameters between FVL subjects with or without a history of thrombosis. This is the first study on circulating MP levels in subjects who are heterozygote for factor V Leiden. We report that circulating platelet and leukocyte MP are elevated in carriers of this mutation and may be important contributors to risk of thrombosis

Reduction of prothrombin and Factor V levels following supplementation with omega-3 fatty acids is sex dependent: a randomised controlled study

Background: LCn-3PUFA comprised of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) offer cardioprotection involving a decrease in coagulant activity; however, the evidence is equivocal. We have previously demonstrated that the acute (24. h) effects and chronic (4. weeks) effects of LCn-3PUFA supplementation on platelet aggregation in human subjects are sex specific. This study investigated the mechanisms of the sex-dependent effects of LCn-3PUFA with 4. weeks supplementation of EPA-rich vs. DHA-rich oils on procoagulant and platelet activity in healthy subjects. Design: A double-blinded, placebo-controlled randomised trial was conducted in 94 healthy adults: male (<i>n</i>=41) and female (<i>n</i>=53). Platelet coagulation parameters including factors I, II, V, VII, VIII, IX, X, vWF:Ag and endogenous thrombin potential were measured at baseline and 4 weeks post supplementation with EPA-rich or DHA-rich oil capsules. Results: We have previously reported that platelet aggregation is specifically reduced by supplementation with EPA in males and DHA in females. This sex-specific effect was also observed for decreases in plasma levels of Factor II (-7.9±3.8%, <i>P</i>=.026), Factor V (-6.5±4.5%, <i>P</i>=.022) and vWF:Ag (-7.3±2.1%, <i>P</i>=.034) and was most pronounced in males supplemented with EPA. In contrast, DHA-mediated reduction in platelet aggregation in females was not accompanied by any significant changes in the coagulation parameters tested. Conclusion: Significant interactions between sex and specific LCn-3PUFA exist to reduce procoagulant activity differentially in males vs. females and could have profound effects on managing risk of thrombotic disease

Indian Polyvalent Antivenom Accelerates Recovery From Venom-Induced Consumption Coagulopathy (VICC) in Sri Lankan Russell's Viper (Daboia russelii) Envenoming

Background: Venom-induced consumption coagulopathy (VICC) is an important clinical consequence of Russell's viper (Daboia russelii) envenoming. There is limited evidence for antivenom effectiveness in resolving VICC. We aimed to compare the recovery of VICC in patients who received and did not receive antivenom following Russell's viper envenoming. Patients and Methods: This was a non-randomized observational study comparing patients with VICC from Russell's viper envenoming given antivenom for systemic envenoming and those not given antivenom. Antivenom administration was decided by the treating physicians. We included 44 patients with confirmed Russell's viper bites with one or more International Normalized Ratio (INR) value ≥ 1.5 (VICC). We compared five patients who did not receive antivenom with 39 patients who did receive antivenom. The primary outcome was the proportion of patients with an INR Results: The antivenom group had higher peak serum venom concentrations [median (IQR) = 272 (96–1,076) ng/mL versus 21 (8–58) ng/mL] and more severe VICC compared to the no antivenom group. Twenty seven of 39 patients (69%) in the antivenom group had an INR p = 0.006" Fisher's exact test). The fibrinogen recovered in 32 of 39 patients (82%) in the antivenom group compared to one of five patients (20%) in the no antivenom group (absolute difference 62%" 95% CI: 28 to 95%" p = 0.001" Fisher's exact test). Both INR and fibrinogen were significantly improved between 24 and 48 h post-bite in the antivenom group compared to the no antivenom group. Conclusion: Antivenom accelerated the recovery of VICC in patients with Russell's viper envenoming, compared to no recovery in a smaller group of patients with milder VICC not receiving antivenom. This supports the efficacy of antivenom in patients with VICC

Procoagulant snake venoms have differential effects in animal plasmas: Implications for antivenom testing in animal models

Background: Animal models are used to test toxic effects of snake venoms/toxins and the antivenom required to neutralise them. However, venoms that cause clinically relevant coagulopathy in humans may have differential effects in animals. We aimed to investigate the effect of different procoagulant snake venoms on various animal plasmas.Methods: Prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen and D-dimer levels were measured in seven animal plasmas (human, rabbit, cat, guinea pig, pig, cow and rat). In vitro clotting times were then used to calculate the effective concentration (EC50) in each plasma for four snake venoms with different procoagulant toxins: Pseudonaja textilis, Daboia russelli, Echis carinatus and Calloselasma rhodostoma.Results: Compared to human, PT and aPTT were similar for rat, rabbit and pig, but double for cat and cow, while guinea pig had similar aPTT but double PT. Fibrinogen and D-dimer levels were similar for all species. Human and rabbit plasmas had the lowest EC50 for P. textilis (0.1 and 0.4 μg/ml), D. russelli (0.4 and 0.1 μg/ml), E. carinatus (0.6 and 0.1 μg/ml) venoms respectively, while cat plasma had the lowest EC50 for C. rhodostoma (11 μg/ml) venom. Cow, rat, pig and guinea pig plasmas were highly resistant to all four venoms with EC50 10-fold that of human.Conclusions: Different animal plasmas have varying susceptibility to procoagulant venoms, and excepting rabbits, animal models are not appropriate to test procoagulant activity. In vitro assays on human plasma should instead be adopted for this purpose

Quantification of hTERT Splice Variants in Melanoma by SYBR Green Real-time Polymerase Chain Reaction Indicates a Negative Regulatory Role for the β Deletion Variant1

Telomerase activity is primarily determined by transcriptional regulation of the catalytic subunit, human telomerase reverse transcriptase (hTERT). Several mRNA splice variants for hTERT have been identified, but it is not clear if telomerase activity is determined by the absolute or relative levels of full-length (functional) and variant hTERT transcripts. We have developed an SYBR green-based reverse transcription-quantitative polymerase chain reaction assay for the enumeration of the four common hTERT mRNA variants and correlated these with telomerase activity and telomere length in 24 human melanoma cell lines. All except five of the lines expressed four hTERT transcripts, with an overall significant level of co-occurrence between absolute mRNA levels of full-length α+/β+ hTERT and the three splice variants α-/β+, α+/β-, and α-/β-. On average, α+/β+ made up the majority (48.1%) of transcripts, followed by α+/β- (44.6%), α-/β- (4.4%), and α-/β+ (2.9%). Telomerase activity ranged from 1 to 247 relative telomerase activity and correlated most strongly with the absolute amount of α+/β+ (R = 0.791, P = .000004) and the relative amount of α+/β- (R = -0.465, P = .022). This study shows that telomerase activity in melanoma cells is best determined by the absolute expression of full-length hTERT mRNA and indicates a role for the hTERT β deletion variant in the negative regulation of enzyme activity

Comparative sensitivity of commercially available aPTT reagents to mulga snake (Pseudechis australis) venom

This study aimed to determine the relative sensitivity of activated partial thromboplastin time (aPTT) reagents to the anticoagulant effects of phospholipases in mulga snake (Pseudechis australis) venom. Twenty-one haematology laboratories participating in the Royal College of Pathologists of Australasia Quality Assurance Programs were sent human plasma samples spiked with mulga venom (n = 25 total results). Results for 17 patients with mulga snake envenoming were available through the Australian Snakebite Project. Only 12 of 25 venom spiked samples returned an abnormally prolonged aPTT. Tests performed with Dade Actin FS (n = 7) did not identify any of the spiked samples as abnormal. Although clotting times were significantly prolonged using the lupus anticoagulant sensitive Actin FSL (n = 5, p = 0.043), only one was reported as abnormal. Only laboratories using TriniCLOT aPTT S (n = 6), HemosIL APTT SP (n = 2) and Stago PTT-A (n = 1) consistently recorded the spiked sample as being above the upper normal reference interval. Abnormally prolonged aPTTs were recorded for four of eight patients whose tests were performed with Actin FSL, five of eight patients with TriniCLOT aPTT HS, and three of three patients using TriniCLOT aPTT S. We conclude that some reagents used for routine aPTT testing are relatively insensitive to the anticoagulant effects of mulga snake venom. Tests performed with these reagents should be interpreted with caution