Group B Streptococcus engages an inhibitory siglec through sialic acid mimicry to blunt innate immune and inflammatory responses in vivo

Yung-Chi Chang, Joshua Olson, Federico C. Beasley, Christine Tung, Jiquan Zhang, Paul R. Crocker, Ajit Varki (Lead / Corresponding author), Victor Nizet (Lead / Corresponding author)

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    Abstract

    Group B Streptococcus (GBS) is a common agent of bacterial sepsis and meningitis in newborns. The GBS surface capsule contains sialic acids (Sia) that engage Sia-binding immunoglobulin-like lectins (Siglecs) on leukocytes. Here we use mice lacking Siglec-E, an inhibitory Siglec of myelomonocytic cells, to study the significance of GBS Siglec engagement during in vivo infection. We found GBS bound to Siglec-E in a Sia-specific fashion to blunt NF-?B and MAPK activation. As a consequence, Siglec-E-deficient macrophages had enhanced pro-inflammatory cytokine secretion, phagocytosis and bactericidal activity against the pathogen. Following pulmonary or low-dose intravenous GBS challenge, Siglec-E KO mice produced more pro-inflammatory cytokines and exhibited reduced GBS invasion of the central nervous system. In contrast, upon high dose lethal challenges, cytokine storm in Siglec-E KO mice was associated with accelerated mortality. We conclude that GBS Sia mimicry influences host innate immune and inflammatory responses in vivo through engagement of an inhibitory Siglec, with the ultimate outcome of the host response varying depending upon the site, stage and magnitude of infection.
    Original languageEnglish
    Article numbere1003846
    JournalPLoS Pathogens
    Volume10
    Issue number1
    DOIs
    Publication statusPublished - 2 Jan 2014

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