Brucellosis Vaccine Ag85a-S2 activates cGAS-Sting Signaling Pathway in Intestinal Mucosal Cells

Brucellosis is a zoonotic disease caused by Gram-negative bacteria, resulting in an economic loss of billions of USD per year. Most of the Brucellosis vaccines in the application are the whole bacteria vaccines, which typically have high toxicity and low immunogenicity. We recently developed an S2 vaccine adjuvanted with Ag85A (Ag85A-S2), which greatly improved the immunogenic properties of S2. However, the mechanisms of Ag85A-S2 remained elusive. Here, we found that Ag85A-S2 activated cGAS-STING pathways both in intestinal mucosal cells and in a cGAS knockout cell line in vitro. We demonstrated that the cGAS knockout significantly downregulated the abundance of interferon and other cytokines induced by Ag85A-S2. In sum, Ag85-S2-mediated enhancement of immune responses was dependent on both cGAS and STING. Our results provided a new strategy for preventing Brucellosis from livestock, which might reduce the dosage and potential toxicity compared to the traditional S2 vaccine. Overall design: We knocked out cGAS and stimulated this knockout cell line with Ag85a-S2.布鲁氏菌病（Brucellosis）是由革兰氏阴性菌（Gram-negative bacteria）引发的人畜共患病，每年造成数十亿美元的经济损失。当前临床应用的布鲁氏菌病疫苗多为全菌体疫苗，此类疫苗普遍存在毒性较高、免疫原性较低的缺陷。我们近期研发了一款搭载Ag85A佐剂的S2疫苗（Ag85A-S2），该疫苗大幅提升了S2的免疫原性，但Ag85A-S2的作用机制仍未明确。本研究发现，Ag85A-S2可在体外激活肠黏膜细胞与cGAS敲除细胞系中的cGAS-STING信号通路；实验证实，敲除cGAS可显著下调Ag85A-S2诱导的干扰素与其他细胞因子的表达水平。综上，Ag85A-S2介导的免疫应答增强效应同时依赖于cGAS与STING。本研究结果为家畜布鲁氏菌病的防控提供了全新策略，相较于传统S2疫苗，该策略有望降低疫苗使用剂量与潜在毒性。总体实验设计：我们构建了cGAS敲除细胞系，并使用Ag85A-S2对该敲除细胞系进行刺激。