Fei D T, Lowe J, Jardieu P
Department of Bioanalytical Technology, Genentech, Inc., South San Francisco, CA 94080.
J Immunol Methods. 1994 May 16;171(2):189-99. doi: 10.1016/0022-1759(94)90039-6.
A novel bioactivity assay has been developed to quantitate the biological activity of a humanized, monoclonal anti-IgE antibody (rhuMAbE25) in human whole blood. Heparinized blood specimens from prescreened healthy donors were sensitized for 2 h with a constant amount of human plasma containing IgE specific for ragweed and then challenged with ragweed allergen. Histamine was released in a dose-dependent fashion and reached plateau levels after 30 min. As expected, the release of histamine by ragweed allergen was time, temperature and Ca2+ dependent, and could be enhanced by the presence of 33% deuterium oxide. Allergen-triggered release could be inhibited by rhuMAbE25 with an effective dose range from 0.1 to 1 microgram/ml. Preincubation with other humanized MAbs, which exhibit 95% homology to rhuMAbE25 but differ in epitope specificity, failed to inhibit the ragweed-induced histamine release. Overall, this bioactivity assay has a low interassay variability (%CV) of 17% (n = 23) and can be readily modified to determine if rhuMAbE25 or other anti-allergy therapeutics are capable of blocking histamine release elicited by other allergens. Moreover, the assay can be used to confirm IgE-mediated allergic responses and to provide early information regarding safety and potential efficacy of therapeutics aimed at blocking IgE dependent responses.
已开发出一种新型生物活性测定法，用于定量人源化单克隆抗IgE抗体（rhuMAbE25）在人全血中的生物活性。从预先筛选的健康供体采集的肝素化血液标本，用恒定剂量的含有针对豚草的特异性IgE的人血浆致敏2小时，然后用豚草过敏原进行激发。组胺以剂量依赖的方式释放，并在30分钟后达到平台水平。正如预期的那样，豚草过敏原引起的组胺释放依赖于时间、温度和Ca2+，并且在存在33%氧化氘的情况下会增强。rhuMAbE25可以抑制过敏原触发的释放，有效剂量范围为0.1至1微克/毫升。与其他与人源化单克隆抗体（rhuMAbE25具有95%的同源性，但表位特异性不同）预孵育，未能抑制豚草诱导的组胺释放。总体而言，这种生物活性测定法的批间变异系数（%CV）较低，为17%（n = 23），并且可以很容易地进行修改，以确定rhuMAbE25或其他抗过敏疗法是否能够阻断其他过敏原引发的组胺释放。此外，该测定法可用于确认IgE介导的过敏反应，并提供有关旨在阻断IgE依赖性反应的疗法的安全性和潜在疗效的早期信息。
