Insights into tick-pathogen interactions – a single cell RNA sequencing approach of transcriptional changes during ehrlichial infection

This study provides a single-cell resolution framework for interpreting tick cell line biology during infection with a medically relevant ehrlichial pathogen. Using scRNA-seq, we show that the <i>I. scapularis</i> embryonic-derived ISE6 cell line comprises multiple transcriptionally distinct cell states, yet these states do not map cleanly onto canonical tick tissue signatures, even when compared against a curated reference tissue atlas. Despite this heterogeneity, EME broadly infects ISE6 cell population, indicating that susceptibility is not restricted to a specific cell type. We further define a time-dependent arthropod vector response in which early infection is marked by activation of stress and metabolic adaptation response, followed by late-stage inhibition of key signaling, transcriptional, and proliferative pathways as bacterial burden increases. Together, these findings strengthen the biological interpretation of ISE6 as an in vitro model for tick-pathogen interactions and provide a resource for future mechanistic studies of ehrlichial persistence, replication, and vector competence.