Healthy elderly people lack neutrophil-mediated functional activity to type V group B Streptococcus.
OBJECTIVE
To determine the function of capsular polysaccharide (CPS)-specific immunoglobulin-G (IgG) and neutrophils from older adults in increasing ingestion and killing of type V group B Streptococcus (GBS).


METHODS
Cross-sectional study.


METHODS
Outpatient clinic at Baylor College of Medicine.


METHODS
The subjects were 40 healthy, community-dwelling adults aged 65 and older from Houston, Texas.


METHODS
The serum level of type V GBS CPS-specific IgG was measured using an enzyme-linked immunosorbent assay. Functional activity was evaluated using an opsonophagocytosis assay.


RESULTS
Sera from four subjects promoted efficient neutrophil-mediated phagocytosis and killing of type V GBS (mean log10 reduction+/-standard deviation in colony-forming units (cfu)=1.51+/-0.39). Each had serum CPS-specific IgG concentrations exceeding 1 microg/mL. Sera from 36 subjects did not promote neutrophil-mediated functional activity (mean log10 reduction in cfu=-0.09+/-0.06; P=.025). Only one of these 36 had a CPS-specific IgG concentration exceeding 1 microg/mL. When pooled sera from young adults given type V GBS conjugate vaccine was added at CPS-specific IgG concentrations of 4 microg/mL or 0.4 microg/mL, sera from all subjects promoted neutrophil-mediated killing of type V GBS. No impairment was evident in the neutrophil function of elderly subjects when it was compared with that of young adults.


CONCLUSIONS
CPS-specific IgG and neutrophils from healthy older adults function to ingest and kill type V GBS, but these antibodies are not present in sufficient amounts in most individuals. Further studies should determine whether a type V GBS vaccine induces functionally active antibodies in older people.
Amaya
Rene A
RA
Departments of Pediatrics and Molecular Virology and Microbiology, Section of Infectious Disease, Baylor College of Medicine, Houston, Texas 77030, USA.
Baker
Carol J
CJ
Keitel
Wendy A
WA
Edwards
Morven S
MS
D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D009504:Neutrophils / Q000276:immunology*; D010587:Phagocytosis / Q000276:immunology; D013292:Streptococcus agalactiae / Q000276:immunology*
D007074:Immunoglobulin G