Publication Date

5-1-2024

Journal

Immunohorizons

DOI

10.4049/immunohorizons.2300076

PMID

38809232

PMCID

PMC11150127

PubMedCentral® Posted Date

5-29-2024

PubMedCentral® Full Text Version

Post-print

Published Open-Access

yes

Keywords

Animals, Mice, Streptococcus agalactiae, Animals, Newborn, N-Acetylneuraminic Acid, Sialic Acid Binding Ig-like Lectin 1, Streptococcal Infections, STAT1 Transcription Factor, Mice, Knockout, Immunity, Innate, Mice, Inbred C57BL, Lung, Macrophages, Alveolar, Female, Macrophages, Lectins, Sialic Acid Binding Immunoglobulin-like Lectins, Antigens, CD, Antigens, Differentiation, B-Lymphocyte

Abstract

The mammalian Siglec receptor sialoadhesin (Siglec1, CD169) confers innate immunity against the encapsulated pathogen group B Streptococcus (GBS). Newborn lung macrophages have lower expression levels of sialoadhesin at birth compared with the postnatal period, increasing their susceptibility to GBS infection. In this study, we investigate the mechanisms regulating sialoadhesin expression in the newborn mouse lung. In both neonatal and adult mice, GBS lung infection reduced Siglec1 expression, potentially delaying acquisition of immunity in neonates. Suppression of Siglec1 expression required interactions between sialic acid on the GBS capsule and the inhibitory host receptor Siglec-E. The Siglec1 gene contains multiple STAT binding motifs, which could regulate expression of sialoadhesin downstream of innate immune signals. Although GBS infection reduced STAT1 expression in the lungs of wild-type newborn mice, we observed increased numbers of STAT1+ cells in Siglece-/- lungs. To test if innate immune activation could increase sialoadhesin at birth, we first demonstrated that treatment of neonatal lung macrophages ex vivo with inflammatory activators increased sialoadhesin expression. However, overcoming the low sialoadhesin expression at birth using in vivo prenatal exposures or treatments with inflammatory stimuli were not successful. The suppression of sialoadhesin expression by GBS-Siglec-E engagement may therefore contribute to disease pathogenesis in newborns and represent a challenging but potentially appealing therapeutic opportunity to augment immunity at birth.

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