CIBIO-UP, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, InBIO, Laboratório Associado, Campus Agrário de Vairão, Vairão, Portugal.
BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Campus Agrário de Vairão, Vairão, Portugal.
Front Immunol. 2022 Jun 17;13:907342. doi: 10.3389/fimmu.2022.907342. eCollection 2022.
Immunoglobulin A provides a major line of defence against pathogens and plays a key role in the maintenance of the commensal microbiota in the intestinal tract. Having been shown to be more effective at tumour cell killing than IgG and strongly active against pathogens present in the mucosae, IgA antibodies have been attracting significant attention in recent years for use as therapeutic antibodies. To improve their therapeutic potential, bioengineered IgA forms with increased serum half-life and neutralizing abilities have been developed but the IgA hinge, which impacts susceptibility to bacterial proteases and ability to bridge between target and effector cells, has not yet been explored. The European rabbit has 15 IgA subclasses with exclusive hinge region motifs and varying lengths, constituting a unique model to evaluate the functional capabilities offered by incorporation of longer IgA hinges into immunoglobulins. Hinge regions from rabbit IgAs, featuring different lengths and sequences, were inserted into human IgA1 heavy chain to substitute the IgA1 hinge. These hinges did not appear to affect antigen binding nor the ability of the engineered chimeric IgA1 to bind and trigger FcαRI, as detected by IgA-mediated cell agglutination and release of superoxide by neutrophils. All rabbit hinge-human IgA1 hybrids were resistant to IgA protease enzyme digestion, as predicted by the lack of the cleavage site in the rabbit hinges. Some IgA1s featuring long rabbit hinges were cleaved by IgA1 protease cleavage type 1 or 2 enzymes, despite the lack of the predicted cleavage sites. More interestingly, the hybrid featuring the rabbit IgA15 hinge was not affected by any of the IgA proteases. The IgA15 hinge is longer than that found in human IgA1 and is composed by a unique motif with a stretch of nine consecutive Ser residues. These characteristics allow the preservation of a long hinge, with associated ability to bridge distantly spaced antigens and provide higher avidity binding, while remaining resistant to IgA protease degradation. The data suggest that the rabbit Cα15 hinge represents an interesting alternative hinge sequence for therapeutic human IgA antibodies that remains resistant to proteolytic cleavage.
免疫球蛋白 A 提供了针对病原体的主要防御线，并在维持肠道共生菌群方面发挥着关键作用。由于其在杀伤肿瘤细胞方面比 IgG 更有效，并且对粘膜中存在的病原体具有强烈的活性，因此 IgA 抗体近年来作为治疗性抗体引起了广泛关注。为了提高其治疗潜力，已经开发出具有延长血清半衰期和中和能力的生物工程 IgA 形式，但 IgA 铰链，它影响对细菌蛋白酶的敏感性和在靶标和效应细胞之间搭桥的能力，尚未得到探索。欧洲兔有 15 种 IgA 亚类，具有独特的铰链区基序和不同的长度，构成了一个独特的模型，可用于评估将更长的 IgA 铰链纳入免疫球蛋白所提供的功能能力。来自兔 IgA 的铰链区，具有不同的长度和序列，被插入到人 IgA1 重链中以替代 IgA1 铰链。这些铰链似乎不会影响抗原结合，也不会影响工程化嵌合 IgA1 结合并触发 FcαRI 的能力，如通过 IgA 介导的细胞凝集和中性粒细胞释放超氧化物所检测到的。所有兔铰链-人 IgA1 杂种都对 IgA 蛋白酶消化具有抗性，正如兔铰链中缺乏切割位点所预测的那样。尽管缺乏预测的切割位点，但一些具有长兔铰链的 IgA1 被 IgA1 蛋白酶 1 型或 2 型酶切割。更有趣的是，具有兔 IgA15 铰链的杂种不受任何 IgA 蛋白酶的影响。兔 IgA15 铰链比人 IgA1 中的铰链长，由一个独特的基序组成，该基序由 9 个连续的 Ser 残基组成。这些特征允许保持长铰链，同时保持与远距离抗原结合的能力，并提供更高的亲和力结合，同时仍然抵抗 IgA 蛋白酶的降解。数据表明，兔 Cα15 铰链代表了一种有趣的治疗性人 IgA 抗体替代铰链序列，它仍然抵抗蛋白水解切割。
