Monoclonal antibodies (MAbs) have the potential to assist in the battle against multidrug-resistant bacteria such as carbapenem-resistant Klebsiella pneumoniae (CR-Kp). However, the characteristics by which these antibodies (Abs) function, such as the role of antibody subclass, must be determined before such modalities can be carried from the bench to the bedside. We performed a subclass switch on anticapsular monoclonal murine IgG₃ (mIgG₃) hybridomas and identified and purified a murine IgG₁ (mIgG₁) hybridoma line through sib selection. We then compared the ability of the mIgG₁ and mIgG₃ antibodies to control CR-Kp sequence type 258 (ST258) infection both in vitro and in vivo. We found by enzyme-limited immunosorbent assay (ELISA) and flow cytometry that mIgG₃ has superior binding to the CR-Kp capsular polysaccharide (CPS) and superior agglutinating ability compared to mIgG₁. The mIgG₃ also, predictably, had better complement-mediated serum bactericidal activity than the mIgG₁ and also promoted neutrophil-mediated killing at concentrations lower than that of the mIgG₁. In contrast, the mIgG₁ had marginally better activity in improving macrophage-mediated phagocytosis. Comparing their activities in a pulmonary infection model with wild-type as well as neutropenic mice, both antibodies reduced organ burden in a nonlethal challenge, regardless of neutrophil status, with mIgG₁ having the highest overall burden reduction in both scenarios. However, at a lethal inoculum, both antibodies showed reduced efficacy in neutropenic mice, with mIgG₃ retaining the most activity. These findings suggest the viability of monoclonal Ab adjunctive therapy in neutropenic patients that cannot mount their own immune response, while also providing some insight into the relative contributions of immune mediators in CR-Kp protection.

中文翻译：

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IgG 亚类在抗碳青霉烯类肺炎克雷伯菌的抗体介导保护中的作用。

单克隆抗体 (MAb) 有可能帮助对抗多重耐药菌，例如耐碳青霉烯的肺炎克雷伯菌(CR- Kp )。然而，必须先确定这些抗体 (Abs) 发挥功能的特征，例如抗体亚类的作用，然后才能将此类方式从工作台带到床边。我们对抗荚膜单克隆鼠 IgG ₃ (mIgG ₃ ) 杂交瘤进行了亚类转换，并通过同胞选择鉴定和纯化了鼠 IgG ₁ (mIgG ₁ ) 杂交瘤系。然后我们比较了 mIgG ₁和 mIgG ₃抗体控制 CR- Kp 的能力序列类型 258 (ST258)体外和体内感染。我们通过酶限免疫吸附测定 (ELISA) 和流式细胞术发现，与 mIgG ₁相比，mIgG ₃与 CR- Kp荚膜多糖 (CPS) 的结合和凝集能力更强。该mIgG ₃也，可以预见，具有较好的补体介导的血清杀菌活性比mIgG ₁和浓度也促进了嗜中性粒细胞介导的杀伤比mIgG的降低₁。相比之下，mIgG ₁在改善巨噬细胞介导的吞噬作用方面具有稍好的活性。将它们在肺部感染模型中的活性与野生型以及中性粒细胞减少小鼠进行比较，无论中性粒细胞状态如何，这两种抗体都降低了非致命性挑战中的器官负担，mIgG ₁在两种情况下的总体负担降低幅度最大。然而，在致死接种中，两种抗体在中性粒细胞减少小鼠中均表现出降低的功效，其中 mIgG ₃保留了最大的活性。这些发现表明，单克隆抗体辅助治疗在无法产生自身免疫反应的中性粒细胞减少患者中具有可行性，同时也提供了一些关于免疫介质在 CR- Kp保护中的相对贡献的见解。