DataSheet_1_Lipidation of pneumococcal proteins enables activation of human antigen-presenting cells and initiation of an adaptive immune response.pdf

Streptococcus pneumoniae remains a significant global threat, with existing vaccines having important limitations such as restricted serotype coverage and high manufacturing costs. Pneumococcal lipoproteins are emerging as promising vaccine candidates due to their surface exposure and conservation across various serotypes. While prior studies have explored their potential in mice, data in a human context and insights into the impact of the lipid moiety remain limited. In the present study, we examined the immunogenicity of two pneumococcal lipoproteins, DacB and MetQ, both in lipidated and non-lipidated versions, by stimulation of primary human immune cells. Immune responses were assessed by the expression of common surface markers for activation and maturation as well as cytokines released into the supernatant. Our findings indicate that in the case of MetQ lipidation was crucial for activation of human antigen-presenting cells such as dendritic cells and macrophages, while non-lipidated DacB demonstrated an intrinsic potential to induce an innate immune response. Nevertheless, immune responses to both proteins were enhanced by lipidation. Interestingly, following stimulation of dendritic cells with DacB, LipDacB and LipMetQ, cytokine levels of IL-6 and IL-23 were significantly increased, which are implicated in triggering potentially important Th17 cell responses. Furthermore, LipDacB and LipMetQ were able to induce proliferation of CD4+ T cells indicating their potential to induce an adaptive immune response. These findings contribute valuable insights into the immunogenic properties of pneumococcal lipoproteins, emphasizing their potential role in vaccine development against pneumococcal infections.

肺炎链球菌（Streptococcus pneumoniae）仍是全球范围内的重大威胁，现有疫苗存在血清型覆盖范围受限、制造成本高昂等显著局限。肺炎链球菌脂蛋白因具有表面暴露性及跨多种血清型的保守性，正成为极具潜力的候选疫苗。尽管先前研究已探索了其在小鼠模型中的潜力，但针对人体情境的相关数据以及对脂质基团作用机制的认知仍较为匮乏。
本研究中，我们通过刺激原代人免疫细胞，对两种肺炎链球菌脂蛋白——DacB与MetQ的脂化型与非脂化型的免疫原性进行了评估。免疫应答通过检测活化与成熟相关的常见表面标志物表达量，以及上清液中释放的细胞因子水平进行评估。
研究结果显示，对于MetQ而言，脂化修饰对人抗原呈递细胞（antigen-presenting cells，如树突状细胞（dendritic cells）与巨噬细胞（macrophages））的活化至关重要；而非脂化的DacB则具备触发固有免疫应答的内在潜力。尽管如此，两种蛋白的免疫应答均可通过脂化修饰得到增强。值得注意的是，在用DacB、LipDacB及LipMetQ刺激树突状细胞后，IL-6与IL-23的细胞因子水平显著升高，这两类细胞因子与触发潜在关键的Th17细胞应答密切相关。此外，LipDacB与LipMetQ能够诱导CD4+ T细胞增殖，表明其具备触发适应性免疫应答的潜力。
本研究的发现为肺炎链球菌脂蛋白的免疫原性特性提供了宝贵见解，凸显了其在抗肺炎链球菌感染疫苗开发中的潜在应用价值。