Trogocytosis-associated cell to cell spread of intracellular bacterial pathogens

Abstract

Macrophages are myeloid-derived phagocytic cells and one of the first immune cell types to respond to microbial infections. However, a number of bacterial pathogens are resistant to the antimicrobial activities of macrophages and can grow within these cells. Macrophages have other immune surveillance roles including the acquisition of cytosolic components from multiple types of cells. We hypothesized that intracellular pathogens that can replicate within macrophages could also exploit cytosolic transfer to facilitate bacterial spread. We found that viable Francisella tularensis, as well as Salmonella enterica bacteria transferred from infected cells to uninfected macrophages along with other cytosolic material through a transient, contact dependent mechanism. Bacterial transfer occurred when the host cells exchanged plasma membrane proteins and cytosol via a trogocytosis related process leaving both donor and recipient cells intact and viable. Trogocytosis was strongly associated with infection in mice, suggesting that direct bacterial transfer occurs by this process in vivo.DOI: http://dx.doi.org/10.7554/eLife.10625.001

Actin-based motility and cell-to-cell spread of bacterial pathogens

“…Despite these developments, we still don’t fully understand the processes of motility and spread at the mechanistic level, or how the mechanisms compare between pathogens. Moreover, the diversity of spread mechanisms extends well beyond what we covered in this review, and also includes those involving ejectosomes ( M. marinum [68]), trogocytosis ( Francisella tularensis [69]), efferocytosis ( L. monocytogenes [70]) and cell-cell fusion ( Burkholderia [6]). Thus, it is clear that bacterial pathogens have evolved many ways to manipulate the host cell machinery to promote their life cycle.…”

CD169 + macrophages orchestrate innate immune responses by regulating bacterial localization in the spleen

“…This result explains why LLO-deficient Lm-based vaccine vectors are poor at inducing a potent CD8 T cell response. Because ActA- assisted cell-to-cell spread was not required for the trans-infection of Lm from CD169 + macrophages to CD8αα DCs, other processes such as trogocytosis (34) likely play a more important role.…”

Intercellular mitochondrial transfer: bioenergetic crosstalk between cells

“…Although amebic trogocytosis promotes death of host cells, the functional role of the engulfed mitochondria in amebic invasion remains unclear. In another example of trogocytosis, the organisms, Francisella tularensis and Salmonella enterica transfer intracellular contents from infected to uninfected macrophages along with cytosolic materials such as plasma membrane components and functional major histocompatibility complex I (MHC-I) (Steele, Radlinski et al 2016). Presumably, trogocytosis energizes the invading microorganism, although direct evidence of this is lacking.…”