Antibody and Vaccine Group, Centre for Cancer Immunology, School of Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom.
Department of Molecular Biology and Genetics, Faculty of Arts and Sciences, European University of Lefke, Lefke, Cyprus.
Front Immunol. 2023 Oct 27;14:1252274. doi: 10.3389/fimmu.2023.1252274. eCollection 2023.
T cell expressed CD27 provides costimulation upon binding to inducible membrane expressed trimeric CD70 and is required for protective CD8 T cell responses. CD27 agonists could therefore be used to bolster cellular vaccines and anti-tumour immune responses. To date, clinical development of CD27 agonists has focussed on anti-CD27 antibodies with little attention given to alternative approaches.
Here, we describe the generation and activity of soluble variants of CD70 that form either trimeric (t) or dimer-of-trimer proteins and conduct side-by-side comparisons with an agonist anti-CD27 antibody. To generate a dimer-of-trimer protein (dt), we fused three extracellular domains of CD70 to the Fc domain of mouse IgG1 in a 'string of beads' configuration (dtCD70-Fc).
Whereas tCD70 failed to costimulate CD8 T cells, both dtCD70-Fc and an agonist anti-CD27 antibody were capable of enhancing T cell proliferation . Initial studies demonstrated that dtCD70-Fc was less efficacious than anti-CD27 in boosting a CD8 T cell vaccine response , concomitant with rapid clearance of dtCD70-Fc from the circulation. The accelerated plasma clearance of dtCD70-Fc was not due to the lack of neonatal Fc receptor binding but was dependent on the large population of oligomannose type glycosylation. Enzymatic treatment to reduce the oligomannose-type glycans in dtCD70-Fc improved its half-life and significantly enhanced its T cell stimulatory activity surpassing that of anti-CD27 antibody. We also show that whereas the ability of the anti-CD27 to boost a vaccine response was abolished in Fc gamma receptor (FcγR)-deficient mice, dtCD70-Fc remained active. By comparing the activity of dtCD70-Fc with a variant (dtCD70-Fc(D265A)) that lacks binding to FcγRs, we unexpectedly found that FcγR binding to dtCD70-Fc was required for maximal boosting of a CD8 T cell response . Interestingly, both dtCD70-Fc and dtCD70-Fc(D265A) were effective in prolonging the survival of mice harbouring BCL1 B cell lymphoma, demonstrating that a substantial part of the stimulatory activity of dtCD70-Fc in this setting is retained in the absence of FcγR interaction.
These data reveal that TNFRSF ligands can be generated with a tunable activity profile and suggest that this class of immune agonists could have broad applications in immunotherapy.
T 细胞表达的 CD27 在与诱导型膜表达的三聚体 CD70 结合时提供共刺激，并需要保护性 CD8 T 细胞应答。因此，CD27 激动剂可用于增强细胞疫苗和抗肿瘤免疫应答。迄今为止，CD27 激动剂的临床开发集中在抗 CD27 抗体上，而很少关注替代方法。
在这里，我们描述了形成三聚体（t）或二聚体-of-trimer 蛋白的可溶性 CD70 变体的产生和活性，并与激动剂抗 CD27 抗体进行了并排比较。为了产生二聚体-of-trimer 蛋白（dt），我们将 CD70 的三个细胞外结构域融合到小鼠 IgG1 的 Fc 结构域中，形成“串珠”构型（dtCD70-Fc）。
虽然 tCD70 不能刺激 CD8 T 细胞，但 dtCD70-Fc 和激动剂抗 CD27 抗体都能够增强 T 细胞增殖。初步研究表明，dtCD70-Fc 在增强 CD8 T 细胞疫苗应答方面不如抗 CD27 有效，同时 dtCD70-Fc 从循环中迅速清除。dtCD70-Fc 的快速血浆清除不是由于缺乏新生 Fc 受体结合，而是依赖于大量寡甘露糖型糖基化。用酶处理降低 dtCD70-Fc 中的寡甘露糖型糖基化可提高其半衰期并显著增强其 T 细胞刺激活性，超过抗 CD27 抗体。我们还表明，虽然抗 CD27 增强疫苗应答的能力在 Fc γ受体（FcγR）缺陷型小鼠中被废除，但 dtCD70-Fc 仍然具有活性。通过比较 dtCD70-Fc 的活性与缺乏与 FcγR 结合的变体（dtCD70-Fc(D265A)），我们出人意料地发现，FcγR 与 dtCD70-Fc 的结合对于最大程度地增强 CD8 T 细胞应答是必需的。有趣的是，dtCD70-Fc 和 dtCD70-Fc(D265A) 都能有效延长携带 BCL1 B 细胞淋巴瘤的小鼠的存活时间，表明在这种情况下，dtCD70-Fc 的大部分刺激活性在没有 FcγR 相互作用的情况下仍然保留。
这些数据表明 TNFRSF 配体可以具有可调节的活性谱，并表明此类免疫激动剂在免疫治疗中有广泛的应用。
