Chilukuri Nageswararao, Sun Wei, Parikh Kalpana, Naik Ramachandra S, Tang Lin, Doctor Bhupendra P, Saxena Ashima
Division of Biochemistry, Walter Reed Army Institute of Research, Silver Spring, Maryland 20910-7500, USA.
Toxicol Appl Pharmacol. 2008 Sep 15;231(3):423-9. doi: 10.1016/j.taap.2008.05.016. Epub 2008 May 28.
Human serum butyrylcholinesterase (Hu BChE) serves as an efficacious bioscavenger of highly toxic organophosphorus (OP) compounds. Since there is a concern that the supply of native Hu BChE may be limited, monomeric and tetrameric forms of recombinant Hu BChE (rHu BChE) were evaluated as replacements and found that they lacked sufficient stability in vivo. However, their in vivo stability could be significantly prolonged by conjugation with polyethyleneglycol-20K (PEG) suggesting that monomeric and tetrameric PEG-rHu BChE could function as bioscavengers. Here, the immunogenicity of PEG-rHu BChE was evaluated in mice following two injections given four weeks apart. In addition to pharmacokinetic parameters, such as mean residence time, maximal concentration, time to reach the maximal concentration, elimination half-life and area under the plasma concentration-time curve extrapolated to infinity, the presence of circulating anti-rHu BChE antibodies was also determined. Although the pharmacokinetic parameters were significantly improved for the first injection of monomeric and tetrameric PEG-rHu BChEs, they were much lower for the second injection. Anti-rHu BChE antibodies were detected in the blood of mice following the first and second enzyme injections and their levels were approximately higher by 5-fold and 2-fold in mice injected with monomeric and tetrameric PEG-rHu BChEs as compared to mice injected with unconjugated enzymes. The findings that the rapid clearance of a repeat injection of PEG-rHu BChEs in mice which coincides with the presence of circulating anti-rHu BChE antibodies suggest that PEG conjugation prolonged the circulatory stability of rHu BChE but failed to eliminate its immunogenicity in mice.
人血清丁酰胆碱酯酶（Hu BChE）可作为剧毒有机磷（OP）化合物的有效生物清除剂。由于担心天然Hu BChE的供应可能有限，对重组Hu BChE（rHu BChE）的单体和四聚体形式进行了评估，以作为替代物，结果发现它们在体内缺乏足够的稳定性。然而，通过与聚乙二醇-20K（PEG）偶联，它们在体内的稳定性可显著延长，这表明单体和四聚体PEG-rHu BChE可作为生物清除剂发挥作用。在此，在小鼠间隔四周进行两次注射后，评估了PEG-rHu BChE的免疫原性。除了药代动力学参数，如平均驻留时间、最大浓度、达到最大浓度的时间、消除半衰期以及外推至无穷大的血浆浓度-时间曲线下面积，还测定了循环抗rHu BChE抗体的存在情况。尽管首次注射单体和四聚体PEG-rHu BChE时药代动力学参数有显著改善，但第二次注射时这些参数要低得多。在首次和第二次注射酶后，在小鼠血液中检测到了抗rHu BChE抗体，与注射未偶联酶的小鼠相比，注射单体和四聚体PEG-rHu BChE的小鼠体内抗体水平分别高出约5倍和2倍。在小鼠中重复注射PEG-rHu BChE后迅速清除，这与循环抗rHu BChE抗体的存在相吻合，这一发现表明PEG偶联延长了rHu BChE的循环稳定性，但未能消除其在小鼠中的免疫原性。
