Bacterial lipoteichoic acid is a negative regulator of human dendritic cell activation 2313

Abstract Description Dendritic cells (DCs) play a pivotal role in the recognition, phagocytosis, and presentation of microbial antigens. Streptococcus gordonii, an opportunistic Gram-positive bacterium, causes an infective endocarditis. Since lipoteichoic acid (LTA) is a representative virulence factor of S. gordonii, we here investigated its role in human DCs activation stimulated with LTA-deficient (ΔltaS) S. gordonii and S. gordonii LTA. DCs treated with heat-killed ΔltaS S. gordonii (HKSG) showed relatively higher binding and phagocytic activities than those treated with wild-type HKSG. Furthermore, ΔltaS HKSG was superior to wild-type HKSG in inducing phenotypic maturation markers including CD80, CD83, CD86, PD-L1, and PD-L2, antigen presenting molecule MHC class II, and proinflammatory cytokines such as TNF-α and IL-6. Concomitantly, DCs treated with the ΔltaS HKSG induced better T cell activities, including proliferation and activation marker (CD25) expression, than those treated with the wild-type. LTA, but not lipoproteins, isolated from S. gordonii weakly activated TLR2 and barely affected the expression of phenotypic maturation markers or cytokines in DCs. Collectively, these results demonstrated that LTA is not a major immuno-stimulating agent of S. gordonii but rather it interferes with bacteria-induced DC maturation, suggesting its potential role in immune evasion. Topic Categories Innate Immune Responses and Host Defense: Cellular Mechanisms (INC)