Mouse Peptidoglycan Recognition Protein PGLYRP-1 Plays a Role in the Host Innate Immune Response against Listeria monocytogenes Infection

The role of mouse peptidoglycan recognition protein PGLYRP-1 in innate immunity against Listeria monocytogenes infection was studied. The recombinant mouse PGLYRP-1 and a polyclonal antibody specific to PGLYRP-1 were prepared. The mouse PGLYRP-1 showed antibacterial activities against L. monocytogenes and other Gram-positive bacteria. PGLYRP-1 mRNA expression was induced in the spleens and livers of mice infected with L. monocytogenes. The viable bacterial number increased, and the production of cytokines such as gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) was reduced in mice when mice had been injected with anti-PGLYRP-1 antibody before infection. The levels of IFN-gamma and TNF-alpha titers in the organs were higher and the viable bacterial number was reduced in mice injected with recombinant mouse PGLYRP-1 (rmPGLYRP-1) before infection. PGLYRP-1 could directly induce these cytokines in spleen cell cultures. The elimination of intracellular bacteria was upregulated in NMuLi hepatocyte cells overexpressing PGLYRP-1. The enhancement of the elimination of L. monocytogenes from the organs was observed in IFN-gamma(-/-) mice by rmPGLYRP-1 administration but not in TNF-alpha(-/-) mice. These results suggest that PGLYRP-1 plays a role in innate immunity against L. monocytogenes infection by inducing TNF-alpha.