Ficolin-2 binds to serotype 35B pneumococcus as it does to serotypes 11A and 31, and these serotypes cause more infections in older adults than in children

• Published in: PloS one 2018-12, Vol.13 (12), p.e0209657-e0209657
• Main Authors: Geno, K Aaron, Spencer, Brady L, Bae, Sejong, Nahm, Moon H
• Format: Article
• Language: English
• Subjects: Acetylation; Acetyltransferase; Acetyltransferases - deficiency; Acetyltransferases - genetics; Acetyltransferases - immunology; Adolescent; Adult; Adults; Age composition; Age Factors; Aged; Biology and Life Sciences; Child; Child, Preschool; Children; Chronology; Critical care; Cytometry; Demographic aspects; Deposition; Disease control; Epidemiology; Female; Ficolins; Health aspects; Humans; Identification and classification; Immunity; Innate immunity; Invasiveness; Lectins - genetics; Lectins - immunology; Ligands; Male; Medicine; Medicine and Health Sciences; Middle Aged; Older people; People and Places; Pneumococcal infections; Pneumococcal Infections - genetics; Pneumococcal Infections - immunology; Pneumococcal Infections - microbiology; Pneumococcal Infections - pathology; Protein Binding - genetics; Research and Analysis Methods; Review boards; Risk factors; Serogroup; Serotypes; Serotyping; Skewed distributions; Streptococcus infections; Streptococcus pneumoniae; Streptococcus pneumoniae - genetics; Streptococcus pneumoniae - immunology; Streptococcus pneumoniae - pathogenicity; Studies; United States; Vaccines; Young Adult
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0209657

Among 98 serotypes of Streptococcus pneumoniae, only a small subset regularly causes invasive pneumococcal diseases (IPD). We previously demonstrated that serotype 11A binds to ficolin-2 and has low invasiveness in children. Epidemiologic data suggested, however, that serotype 11A IPD afflicts older adults, possibly indicating reduced ficolin-2-mediated immune protection. Therefore, we studied the epidemiology of ficolin-2-bound serotypes. We obtained IPD case data from the United States Centers for Disease Control and Prevention. We studied three prominent ficolin-2-bound serotypes and their acetyltransferase-deficient variants for ficolin-2 binding and ficolin-2-mediated complement deposition with flow-cytometry. We determined the age distributions of these serotypes from the obtained epidemiologic data. We discovered that the serotype 35B capsule is a novel ficolin-2 ligand due to O-acetylation via WciG. Ficolin-2-mediated complement deposition was observed on serotypes 11A and 35B but not serotype 31 or any O-acetyl transferase deficient derivatives of these serotypes. Serotypes 11A, 35B, and 31 cause more IPD among older adults than children. Studies of the three serotypes provide additional evidence for ficolin-2 providing innate immunity against IPD. The skewed age distribution of the three serotypes suggests that older adults have reduced ficolin-2-mediated immunity and are more susceptible to these serotypes.