scnasRNA-seq resolves in vivo single-cell RNA dynamics of immune cells during Salmonella infection

The immune response against pathogens involves multiple cell state transitions and complex gene expression changes. Here we established an in vivo single-cell nascent RNA labeling sequencing method (scnasRNA-seq) and applied it to survey time-resolved RNA dynamics during immune response to acute enteric infection with Salmonella. We showed that detection of nascent RNA synthesis reflects more realistic information on cell activation and gene transcription than total RNA level. Interplay of nascent RNA synthesis and RNA degradation together modulate dynamics of total RNA. We found that bone marrow macrophages are first primed at very early stage upon Salmonella infection. In contrast, the innate immune response of macrophages in intestine is limited. Notably, intestinal CD8+ T cells and plasma cells are rapidly and specifically activated at early stage post infection. Intestinal late enterocytes quickly express MHC-I molecules and present Salmonella antigen to CD8+ T cells for their activation, serving as antigen presenting cells for initiation of adaptive immunity. Our findings unveil novel RNA control strategies of immune cells and dynamic time course of immune response activation upon Salmonella infection, challenging the doctrine boundary between innate immunity and adaptive immunity against bacterial infection. To measure newly transcribed RNA in vivo, we administrated mice with S4U through tail vein injection to label nascent RNA. Bone marrow cells and small intestinal cells were collect and perform scRNA-seq.