Why does local edema persist? Immunological mismatch between phospholipase A₂ potency and antivenom affinity in Protobothrops mucrosquamatus envenomation
7 affiliations
- 1Department of Emergency Medicine, Tri-Service General Hospital, National Defense Medical University, Taipei, Taiwan
- 2Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan
- 3Institute of Preventive Medicine, National Defense Medical University, New Taipei, Taiwan
- 4Department of Biology and Anatomy, National Defense Medical University, Taipei, Taiwan
- 5Department of Medical Toxicology, Taichung Veterans General Hospital, Taichung, Taiwan
- 6School of Public Health, National Defense Medical University, Taipei, Taiwan
- 7Department of Emergency Medicine, Kaohsiung Armed Forces General Hospital, Kaohsiung, Taiwan
Abstract
Background: Protobothrops mucrosquamatus is the primary species responsible for snakebite morbidity in Taiwan, typically resulting in severe localized tissue edema. Although freeze-dried hemorrhagic antivenom (FHAV) is the standard treatment, persistent swelling remains a frequent clinical challenge. This study aimed to identify primary edematogenic toxins and evaluate the neutralizing efficacy of FHAV and small-molecule inhibitors (SMIs) to address this therapeutic gap. Methodology/principal findings: Multiple linear regression of a retrospective cohort of 50 patients was used to identify predictors of edema remission. Experimentally, a murine paw edema model was established to evaluate the potency of crude venom and isolated fractions (PLA2, SVSP, and SVMP/CTL), whereas ELISA was used to determine FHAV immunoreactivity. Clinically, total FHAV dosage was the strongest independent predictor of the remission timeline (β = 0.658, T = 5.167, P < 0.001), accounting for 69.8% of the variance. Experimentally, the PLA2-enriched fraction was identified as the primary edematogenic driver, eliciting swelling at 100 μg/mL, which was statistically indistinguishable from that of crude venom, whereas the other fractions required fivefold higher concentrations to achieve similar effects. However, ELISA revealed a significant immunological mismatch: the SVMP/CTL fraction sequestered 81.49% of the FHAV, indicating that highly potent PLA2 was poorly targeted. Furthermore, SMIs (varespladib, marimastat, and batimastat) at 10 μM exhibited limited efficacy against crude venom-induced edema, suggesting that single-target interventions against the complex venom proteome are insufficient. Conclusions/significance: Persistent localized edema arises from an immunological mismatch in which FHAV recognizes primarily high-molecular-weight immunogens instead of the primary edematogenic driver, PLA2. Current clinical management necessitates increasing FHAV dosages to compensate for low specific affinity through increased total antibody volume. These findings highlight that robust prospective multicenter trials are urgently needed to transition from empirical dosing to standardized, potency-aligned FHAV protocols, potentially incorporating multimodal therapeutic cocktails to achieve comprehensive neutralization. Author summary: Envenomation by Protobothrops mucrosquamatus is the leading cause of snakebite morbidity in Taiwan and frequently results in severe and persistent localized tissue edema. Although standard therapy with freeze-dried hemorrhagic antivenom (FHAV) is life-saving, clinicians regularly encounter a clinical paradox wherein patients experience progressive swelling despite receiving standard antivenom doses. This study elucidates this phenomenon by identifying a profound immunological mismatch between toxin potency and antivenom binding specificity. Mechanistically, phospholipase A2 (PLA2) enzymes serve as the primary drivers of rapid, intense edematogenesis, whereas FHAV targets predominantly higher molecular weight toxins with a lower relative capacity to induce tissue swelling. Retrospective analysis of a cohort of 50 patients and translational laboratory models confirmed that the total administered FHAV dose is the principal independent predictor of the edema remission timeline. These findings highlight that current antibody neutralization profiles are suboptimally aligned with the specific toxin families driving localized tissue destruction. Ultimately, this work advocates for a paradigm shift toward potency-aligned antivenom protocols and multimodal therapeutic cocktails to accelerate clinical recovery and minimize permanent localized tissue damage.
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BibTeX
@article{ho2026does,
title = {{Why does local edema persist? Immunological mismatch between phospholipase A₂ potency and antivenom affinity in Protobothrops mucrosquamatus envenomation}},
author = {Cheng-Hsuan Ho and Yu-Wei Chiang and Yan-Chiao Mao and Chih-Hsiung Hsu and Feng-Chen Chen and Shih-Hung Tsai and Shing-Hwa Liu},
journal = {PLOS Neglected Tropical Diseases},
year = {2026},
month = sep,
doi = {10.1371/journal.pntd.0014689},
url = {https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014689},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Why does local edema persist? Immunological mismatch between phospholipase A₂ potency and antivenom affinity in Protobothrops mucrosquamatus envenomation
AU - Cheng-Hsuan Ho
AU - Yu-Wei Chiang
AU - Yan-Chiao Mao
AU - Chih-Hsiung Hsu
AU - Feng-Chen Chen
AU - Shih-Hung Tsai
AU - Shing-Hwa Liu
PY - 2026
DA - 2026/09/03
JO - PLOS Neglected Tropical Diseases
DO - 10.1371/journal.pntd.0014689
UR - https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014689
AB - Background: Protobothrops mucrosquamatus is the primary species responsible for snakebite morbidity in Taiwan, typically resulting in severe localized tissue edema. Although freeze-dried hemorrhagic antivenom (FHAV) is the standard treatment, persistent swelling remains a frequent clinical challenge. This study aimed to identify primary edematogenic toxins and evaluate the neutralizing efficacy of FHAV and small-molecule inhibitors (SMIs) to address this therapeutic gap. Methodology/principal findings: Multiple linear regression of a retrospective cohort of 50 patients was used to identify predictors of edema remission. Experimentally, a murine paw edema model was established to evaluate the potency of crude venom and isolated fractions (PLA2, SVSP, and SVMP/CTL), whereas ELISA was used to determine FHAV immunoreactivity. Clinically, total FHAV dosage was the strongest independent predictor of the remission timeline (β = 0.658, T = 5.167, P < 0.001), accounting for 69.8% of the variance. Experimentally, the PLA2-enriched fraction was identified as the primary edematogenic driver, eliciting swelling at 100 μg/mL, which was statistically indistinguishable from that of crude venom, whereas the other fractions required fivefold higher concentrations to achieve similar effects. However, ELISA revealed a significant immunological mismatch: the SVMP/CTL fraction sequestered 81.49% of the FHAV, indicating that highly potent PLA2 was poorly targeted. Furthermore, SMIs (varespladib, marimastat, and batimastat) at 10 μM exhibited limited efficacy against crude venom-induced edema, suggesting that single-target interventions against the complex venom proteome are insufficient. Conclusions/significance: Persistent localized edema arises from an immunological mismatch in which FHAV recognizes primarily high-molecular-weight immunogens instead of the primary edematogenic driver, PLA2. Current clinical management necessitates increasing FHAV dosages to compensate for low specific affinity through increased total antibody volume. These findings highlight that robust prospective multicenter trials are urgently needed to transition from empirical dosing to standardized, potency-aligned FHAV protocols, potentially incorporating multimodal therapeutic cocktails to achieve comprehensive neutralization. Author summary: Envenomation by Protobothrops mucrosquamatus is the leading cause of snakebite morbidity in Taiwan and frequently results in severe and persistent localized tissue edema. Although standard therapy with freeze-dried hemorrhagic antivenom (FHAV) is life-saving, clinicians regularly encounter a clinical paradox wherein patients experience progressive swelling despite receiving standard antivenom doses. This study elucidates this phenomenon by identifying a profound immunological mismatch between toxin potency and antivenom binding specificity. Mechanistically, phospholipase A2 (PLA2) enzymes serve as the primary drivers of rapid, intense edematogenesis, whereas FHAV targets predominantly higher molecular weight toxins with a lower relative capacity to induce tissue swelling. Retrospective analysis of a cohort of 50 patients and translational laboratory models confirmed that the total administered FHAV dose is the principal independent predictor of the edema remission timeline. These findings highlight that current antibody neutralization profiles are suboptimally aligned with the specific toxin families driving localized tissue destruction. Ultimately, this work advocates for a paradigm shift toward potency-aligned antivenom protocols and multimodal therapeutic cocktails to accelerate clinical recovery and minimize permanent localized tissue damage.
SN - 1935-2735
ER -