Jang Jeyoun, Cho Minhui, Lee Hae-Ri, Cha Kiweon, Chun Jeong-Hoon, Hong Kee-Jong, Park Jungchan, Rhie Gi-Eun
Division of High-Risk Pathogen Research, Center for Infectious Diseases, National Institute of Health, 187 Osongsaengmyeong2-ro, Cheongwon-gun, Chungbuk 363-951, Republic of Korea.
Biochim Biophys Acta. 2013 Mar;1830(3):2804-12. doi: 10.1016/j.bbagen.2012.11.006.
The poly-gamma-D-glutamic acid (PGA) capsule, a major virulence factor of Bacillus anthracis, protects bacilli from immune surveillance and allows its unimpeded growth in the host. Recently, the importance of the PGA in the pathogenesis of anthrax infection has been reported. The PGA capsule is associated with lethal toxin (LT) in the blood of experimentally infected animals and enhances the cytotoxicity of LT.
To investigate the role of anti-PGA Abs on progression of anthrax infection, two mouse anti-PGA mAbs with K(d) values of 0.8 microM and 2.6 microM respectively were produced and in silico three dimensional (3D) models of mAbs with their cognitive PGA antigen complex were analyzed.
Anti-PGA mAbs specifically bound encapsulated B. anthracis H9401 and showed opsonophagocytosis activity against the bacteria with complement. The enhancement effect of PGA on LT-mediated cytotoxicity was confirmed ex vivo using mouse bone marrow-derived macrophages and was effectively inhibited by anti-PGA mAb. Passive immunization of mAb completely protected mice from PGA-enhanced LT toxicity and partially rescued mice from anthrax spore challenges. 3D structure models of these mAbs and PGA complex support specific interactions between CDR and cognitive PGA. These results indicate that mouse mAb against PGA capsule prevents the progress of anthrax disease not only by eliminating the vegetative form of encapsulated B. anthracis but also by inhibiting the enhanced cytotoxic activity of LT by PGA through specific binding with PGA capsule antigen.
Our results suggest a potential role for PGA antibodies in preventing and treating anthrax infection.
聚γ-D-谷氨酸（PGA）荚膜是炭疽芽孢杆菌的主要毒力因子，可保护杆菌免受免疫监视，并使其在宿主体内不受阻碍地生长。最近，已有报道指出PGA在炭疽感染发病机制中的重要性。在实验感染动物的血液中，PGA荚膜与致死毒素（LT）相关，并增强了LT的细胞毒性。
为了研究抗PGA抗体在炭疽感染进展中的作用，制备了两种K(d)值分别为0.8 microM和2.6 microM的小鼠抗PGA单克隆抗体，并对其与认知PGA抗原复合物的单克隆抗体的计算机三维（3D）模型进行了分析。
抗PGA单克隆抗体特异性结合被包裹的炭疽芽孢杆菌H9401，并对补体存在下的细菌表现出调理吞噬活性。使用小鼠骨髓来源的巨噬细胞在体外证实了PGA对LT介导的细胞毒性的增强作用，并被抗PGA单克隆抗体有效抑制。单克隆抗体的被动免疫完全保护小鼠免受PGA增强的LT毒性，并部分挽救受炭疽芽孢攻击的小鼠。这些单克隆抗体与PGA复合物的3D结构模型支持CDR与认知PGA之间的特异性相互作用。这些结果表明，抗PGA荚膜的小鼠单克隆抗体不仅通过消除被包裹的炭疽芽孢杆菌的营养形式，而且通过与PGA荚膜抗原特异性结合来抑制PGA增强的LT细胞毒性活性，从而预防炭疽疾病的进展。
我们的结果表明PGA抗体在预防和治疗炭疽感染中具有潜在作用。
