SPI2 T3SS effectors facilitate enterocyte apical to basolateral transmigration of <i>Salmonella</i> -containing vacuoles <i>in vivo</i>

Abstract

<i>Salmonella</i> pathogenicity island (SPI) 2 type three secretion system (T3SS)-mediated effector molecules facilitate bacterial survival in phagocytes but their role in the intestinal epithelium <i>in vivo</i> remains ill-defined. Using our neonatal murine infection model in combination with SPI2 reporter technology and RNA-Seq of sorted primary enterocytes, we demonstrate expression of SPI2 effector molecules by intraepithelial <i>Salmonella</i> Typhimurium <i>(S</i>. Typhimurium). Contrary to expectation, immunostaining revealed that infection with SPI2 T3SS-mutants resulted in significantly enlarged intraepithelial <i>Salmonella</i>-containing vacuoles (SCV) with altered cellular positioning, suggesting impaired apical to basolateral transmigration. Also, infection with isogenic tagged <i>S</i>. Typhimurium strains revealed a reduced spread of intraepithelial SPI2 T3SS mutant <i>S</i>. Typhimurium to systemic body sites. These results suggest that SPI2 T3SS effector molecules contribute to enterocyte apical to basolateral transmigration of the SCV during the early stage of the infection.