784

Abstract

Introduction: Multiple cell surface proteins are glycosylated including TLR ligands. Sialic acid is a common terminal moiety on such proteins and can be removed by pathogen expressed neuraminidases. Desialylation is common in the airway in influenza and is an important aspect of post influenza bacterial pneumonia. Methods: Airway and monocyte cell lines and peritoneal macrophages were treated with NANase (neuraminidase) which hydrolyzes predominantly α(2-3) glycosidic linkages of terminal sialic acids. Desialylation was assessed by flow cytometry as was the expression of TLR2 and TLR4. After NANase treatment (60 min) cells were treated with either TLR2 or 4 ligands and cytokines were measured. Activation of phosho p38, IkB was done by WB and AP-1 and NFkB by EMSA. Results: NANase treatment decreased cell surface sialic acid by 50%. Removal of this amount of sialic acid did not significantly change the expression of TLR2 or 4 on the cell surface of BEAS 2B, J774 or PMs and western blot confirmed no change. After NANase followed by treatment with either TLR ligand treatment, IL-8 was increased in BEAS 2B and TNFa was increased in J774 and PM culture supernatant. In J774 cells and BEAS2b cells, NANase + TLR ligand did not augment phosphorylation of p38 or degradation of IkB and did induce exaggerated AP1 or NFKB activity by EMSA. Conclusions: We conclude that cell surface desialylation can enhance the sensitivity to TLR ligands without activation of conventional signaling elements. Removal of sialic acid may open other pathways for TLR ligand signaling.