Poly-γ-d-glutamic acid capsule of Bacillus licheniformis, a surrogate of Bacillus anthracis capsule induces interferon-gamma production in natural killer cells through interaction with macrophages


Jeon Jun Ho, Lee Hae-Ri, Rhie Gi-eun
Division of High-risk Pathogens, Center for Laboratory Control of Infectious Diseases, KCDC

The poly-γ-d-glutamic acid (PGA) capsule, a major virulence factor of Bacillus anthracis, provides protection to the bacterium from phagocytosis, thereby facilitating unimpeded bacterial growth in the host. We investigated the crosstalk between murine natural killer (NK) cells and macrophages stimulated with the PGA capsule of Bacillus licheniformis, a surrogate of B. anthracis capsule. PGA induced interferon-gamma (IFN-γ) production from NK cells cultured with macrophages. This effect was dependent on macrophage-derived interleukin (IL)-12 and cell-cell contact between NK cells and macrophages through NK cell receptor NKG2D and its ligand RAE-1. Thus, PGA may enhance NK cell activation by inducing IL-12 production in macrophages and facilitating a contact-dependent crosstalk with macrophages.

Keywords: NK cell activation, Poly-γ-d-glutamic acid, Interferon-gamma, Bacillus anthracis, Bacillus licheniformis