Exoproteome from Leptospira interrogans and Host Cells during Infection: Leptospiral Virulence Factors and Cellular Proteins Involved in Stress and Inflammation
Background: Leptospirosis, caused mainly by Leptospira interrogans, is a global zoonotic infectious disease. Macrophages and vascular endothelial cells are the main host cells for L. interrogans during infection, but the proteins released from the pathogen and the two host cells during infection remain mostly unknown.Results: Cellular supernatant proteins (CSPs) from human THP-1 macrophages or umbilical vein endothelial cells (HUVECs) infected with L. interrogans strain Lai were extracted by
... ere extracted by TCA/FASP methods. The exoproteins in the CSPs were identified by LC-MS/MS. Viability of the leptospires and host cells during infection was confirmed by confocal microscopy and MTT. The results showed that higher co-culture temperature (from 28°C to 37°C) and different biochemical environments cause a large change in the exoproteome of the spirochete. L. interrogans increased levels of leptospiral exoproteins related to stress, signal transduction and virulence factors, while the lipoprotein antigens LipL41, LipL21 and/or Loa22 were not detected. During infection of macrophages and endothelial cells, there was a large increase in host-cell exoproteins involved in stress response, complement pathways (C4/5/7/8), inflammatory cytokines (IL-6, TNF-α, MIF, MCP-1 and GM-CSF), extracellular matrix proteins (FN, LN and COLs), and blood coagulation factors. One-third of the leptospires and infected THP-1 macrophages died during macrophage infection, but nearly all the leptospires and endothelial cells remained viable during endothelial cell infection.Conclusions: Infection causes stress reponses for both leptospires and human macrophages and vascular endothelial cells and release of virulence factors, alteration of surface leptospiral lipoprotein antigens and secretion of complement components and inflammatory cytokines from host cells.