Modified vaccinia Ankara (MVA) is a live, attenuated human smallpox vaccine and a vector for the development of new vaccines against infectious diseases and cancer. Efficient activation of the immune system by MVA partially relies on its encounter with dendritic cells (DCs). MVA infection of DCs leads to multiple outcomes, including cytokine production, activation of costimulatory molecules for T cell stimulation, and cell death. Here, we examined how these diverse responses are orchestrated in human DCs. Single-cell analyses revealed that the response to MVA infection in DCs was limited to early viral gene expression. In response to the early events in the viral cycle, we found that DCs grouped into three distinct clusters. A cluster of infected cells sensed the MVA genome by the intracellular innate immunity pathway mediated by cGAS, STING, TBK1, and IRF3 and subsequently produced inflammatory cytokines. In response to these cytokines, a cluster of noninfected bystander cells increased costimulatory molecule expression. A separate cluster of infected cells underwent caspase-dependent apoptosis. Induction of apoptosis persisted after inhibition of innate immunity pathway mediators independently of previously described IRF-dependent or replication-dependent pathways and was a response to early MVA gene expression. Together, our study identified multiple mechanisms that underlie the interactions of MVA with human DCs.

改良痘苗安卡拉 (MVA) 是一种减毒活人天花疫苗，也是开发针对传染病和癌症的新疫苗的载体。MVA 对免疫系统的有效激活部分依赖于它与树突状细胞 (DC) 的接触。DCs 的 MVA 感染会导致多种结果，包括细胞因子的产生、用于 T 细胞刺激的共刺激分子的激活和细胞死亡。在这里，我们检查了这些不同的反应是如何在人类 DC 中进行协调的。单细胞分析表明，DC 中对 MVA 感染的反应仅限于早期病毒基因表达。针对病毒周期的早期事件，我们发现 DC 分为三个不同的簇。一组感染细胞通过 cGAS、STING、TBK1 介导的细胞内先天免疫通路感知 MVA 基因组，和 IRF3 并随后产生炎性细胞因子。作为对这些细胞因子的反应，一组未感染的旁观者细胞增加了共刺激分子的表达。一个单独的感染细胞簇经历了半胱天冬酶依赖性细胞凋亡。在独立于先前描述的 IRF 依赖性或复制依赖性途径抑制先天免疫途径介质后，细胞凋亡的诱导持续存在，并且是对早期 MVA 基因表达的反应。总之，我们的研究确定了 MVA 与人类 DCs 相互作用的多种机制。在独立于先前描述的 IRF 依赖性或复制依赖性途径抑制先天免疫途径介质后，细胞凋亡的诱导持续存在，并且是对早期 MVA 基因表达的反应。总之，我们的研究确定了 MVA 与人类 DCs 相互作用的多种机制。