Bacterial Ghosts of Escherichia coli Drive Efficient Maturation of Bovine Monocyte-Derived Dendritic Cells.

Irshad Ahmed Hajam,Subodh Kishore,Elamurugan Appavoo,Pervaiz Ahmad Dar,Veerakyathappa Bhanuprakash,Kondabattula Ganesh,Jagadeesh Bayry

doi:10.1371/journal.pone.0144397

Abstract

Bacterial ghosts (BGs) are empty cell envelopes derived from Gram-negative bacteria. They not only represent a potential platform for development of novel vaccines but also provide a tool for efficient adjuvant and antigen delivery system. In the present study, we investigated the interaction between BGs of Escherichia coli (E. coli) and bovine monocyte-derived dendritic cells (MoDCs). MoDCs are highly potent antigen-presenting cells and have the potential to act as a powerful tool for manipulating the immune system. We generated bovine MoDCs in vitro from blood monocytes using E. coli expressed bovine GM-CSF and IL-4 cytokines. These MoDCs displayed typical morphology and functions similar to DCs. We further investigated the E. coli BGs to induce maturation of bovine MoDCs in comparison to E. coli lipopolysaccharide (LPS). We observed the maturation marker molecules such as MHC-II, CD80 and CD86 were induced early and at higher levels in BG stimulated MoDCs as compared to the LPS stimulated MoDCs. BG mediated stimulation induced significantly higher levels of cytokine expression in bovine MoDCs than LPS. Both pro-inflammatory (IL-12 and TNF-α) and anti-inflammatory (IL-10) cytokines were induced in MoDCs after BGs stimulation. We further analysed the effects of BGs on the bovine MoDCs in an allogenic mixed lymphocyte reaction (MLR). We found the BG-treated bovine MoDCs had significantly (p<0.05) higher capacity to stimulate allogenic T cell proliferation in MLR as compared to the LPS. Taken together, these findings demonstrate the E. coli BGs induce a strong activation and maturation of bovine MoDCs.

Highlights

The bacterial ghosts (BGs) are empty cell envelopes of Gram-negative bacteria produced by the controlled expression of lysis gene E of bacteriophage PhiX174 [1, 2]
We explored the interaction of bovine monocytederived dendritic cells (MoDCs) with E. coli BGs and showed that the BGs drive efficient maturation and activation of the bovine MoDCs
The differentiation of dendritic cells (DCs) from monocytes has been shown earlier to be dependent on species specific Granulocyte-macrophage colony-stimulating factor (GM-CSF) and Interleukin 4 (IL-4) [29, 31]

Summary

Introduction

The bacterial ghosts (BGs) are empty cell envelopes of Gram-negative bacteria produced by the controlled expression of lysis gene E of bacteriophage PhiX174 [1, 2]. The foreign antigens have been loaded inside the cytoplasmic lumen or expressed both on the surface and in the periplasmic space of BGs [6, 7]. Previous studies demonstrate BGs mediate active immunization against their own envelope structures or when used as antigen delivery vector [7, 8]. Other studies found it safe and potent adjuvant which is capable of polarizing the immune response toward Th1 or Th2 depending upon the presentation of antigen [8]. Very little is known about the interaction of BGs with dendritic cells (DCs) and their impact on the maturation of DCs or induction of Th1/Th2 cytokines

Methods

Results

Conclusion