Brown Recluse Spider Bite Mediated Hemolysis: Clinical Features, a Possible Role for Complement Inhibitor Therapy, and Reduced RBC Surface Glycophorin A as a Potential Biomarker of Venom Exposure

Background
The venom of Loxoscelesreclusa (Brown Recluse spider) can cause a severe, life-threatening hemolysis in humans for which no therapy is currently available in the USA beyond supportive measures. Because this hemolysis is uncommon, relatively little is known about its clinical manifestation, diagnosis, or management. Here, we aimed to clarify the clinical details of envenomation, to determine the efficacy of the complement inhibitor eculizumab to prevent the hemolysis invitro, and to investigate markers of exposure to Brown Recluse venom.
Study Design and Methods
We performed a 10-year chart review of cases of Brown Recluse spider bite-mediated hemolysis at our institution. We also designed an invitro assay to test the efficacy of eculizumab to inhibit hemolysis of venom exposed red blood cells. Finally, we compared levels of CD55, CD59 and glycophorin A on venom exposed versus venom-naïve cells.
Results
Most victims of severe Brown Recluse spider mediated hemolysis at our institution are children and follow an unpredictable clinical course. Brown Recluse spider bite mediated hemolysis is reduced by 79.2% (SD=18.8%) by eculizumab invitro. Erythrocyte glycophorin A, but not CD55 or CD59, is reduced after red blood cells are incubated with venom invitro.
Conclusion
Taken together, our laboratory data and clinical observations indicate that L. reclusa venom exposure results in non-specific antibody and complement fixation on red blood cells, resulting in complement mediated hemolysis that is curtailed by the complement inhibitor eculizumab invitro. Glycophorin A measurement by flow cytometry may help to identify victims of L. reclusa envenomation.

背景
褐隐蛛（Loxosceles reclusa，俗称棕隐士蛛）的毒液可引发人类严重的、危及生命的溶血反应，目前美国除支持治疗外尚无针对性治疗方案。由于此类溶血反应较为罕见，其临床表现、诊断及治疗策略的相关研究相对匮乏。本研究旨在明确褐隐蛛螫伤中毒的临床细节，探究补体抑制剂依库珠单抗（eculizumab）体外（in vitro）预防溶血的效果，并鉴定褐隐蛛毒液暴露的生物标志物。

研究设计与方法
本研究对本机构10年间收治的褐隐蛛咬伤所致溶血病例开展了病历回顾分析。同时构建体外（in vitro）实验模型，检测依库珠单抗抑制毒液暴露红细胞溶血的效果；此外，比较了毒液暴露组与未暴露组红细胞表面CD55、CD59及血型糖蛋白A（glycophorin A）的表达水平。

结果
本机构收治的重症褐隐蛛咬伤溶血患者多为儿童，且临床病程难以预测。体外（in vitro）实验显示，依库珠单抗可使褐隐蛛咬伤介导的溶血反应降低79.2%（标准差=18.8%）。体外共孵育实验表明，红细胞与褐隐蛛毒液接触后，其表面血型糖蛋白A的表达水平显著降低，而CD55与CD59的表达无明显变化。

结论
综合本研究的实验室数据与临床观察结果可知，褐隐蛛毒液暴露可诱导红细胞表面发生非特异性抗体与补体结合，进而引发补体介导的溶血反应，该反应可在体外被补体抑制剂依库珠单抗抑制。通过流式细胞术检测红细胞表面血型糖蛋白A水平，或可辅助诊断褐隐蛛螫伤中毒患者。