Developmental Immaturity of Siglec Receptor Expression on Neonatal Alveolar Macrophages Predisposes to Severe Group B Streptococcal Infection

• DOI: 10.1016/j.isci.2020.101207
• Publication Date: 2020-05-28T02:22:15Z
• Authors: Sean J. Lund; Kathryn A. Patras; Jacqueline M. Kimmey; Asami Yamamura; Lindsay D. Butcher; Pamela G.B. Del R...; Gilberto E. Herna...; Alyssa M. McCoy; Omar Lakhdari; Victor Nizet; Lawrence S. Prince
• Keywords: 570; Science; 610; Low Birth Weight and Health of the Newborn; Article; 03 medical and health sciences; Preterm; Infant Mortality; 2.1 Biological and endogenous factors; Lung; Pediatric; 0303 health sciences; Biomedical and Clinical Sciences; Q; Paediatrics; Pneumonia; Perinatal Period - Conditions Originating in Perinatal Period; 3. Good health; Infectious Diseases; Good Health and Well Being; Reproductive Medicine; Medical Microbiology; Pneumonia & Influenza; Microbiome; Infection

Streptococcus agalactiae (Group B Streptococcus, GBS) is the most common neonatal pathogen. However, the cellular and molecular mechanisms for neonatal susceptibility to GBS pneumonia and sepsis are incompletely understood. Here we optimized a mouse model of GBS pneumonia to test the role of alveolar macrophage (ΑΜΦ) maturation in host vulnerability to disease. Compared with juvenile and adult mice, neonatal mice infected with GBS had increased mortality and persistence of lung injury. In addition, neonatal mice were defective in GBS phagocytosis and killing. ΑΜΦ depletion and disruption of ΑΜΦ differentiation in Csf2-/- mice both impaired GBS clearance. AMΦ engage the heavily sialylated GBS capsule via the cell surface Siglec receptors Sn and Siglec-E. Although both newborn and adult ΑΜΦ expressed Siglec-E, newborn ΑΜΦ expressed significantly lower levels of Sn. We propose that a developmental delay in Sn expression on ΑΜΦ may prevent effective killing and clearing of GBS from the newborn lung.