Antibody responses to nasopharyngeal carriage of Streptococcus pneumoniae in adults: a longitudinal household study.
BACKGROUND
Natural immunity to Streptococcus pneumoniae is thought to be induced by exposure to S. pneumoniae or cross-reactive antigens. No longitudinal studies of carriage of and immune responses to S. pneumoniae have been conducted using sophisticated immunological laboratory techniques.


METHODS
We enrolled 121 families with young children into this study. Nasopharyngeal (NP) swabs were collected monthly for 10 months from all family members and were cultured in a standard fashion. Cultured S. pneumoniae isolates were serotyped. At the beginning (month 0) and end (month 10) of the study, venous blood was collected from family members >18 years old. Serotype-specific antipolysaccharide immunoglobulin G (IgG) and functional antibody and antibodies to pneumolysin, pneumococcal surface protein A (PspA), and pneumococcal surface antigen A (PsaA) were measured in paired serum samples.


RESULTS
Levels of anticapsular IgG increased significantly after carriage of serotypes 9V, 14, 18C, 19F, and 23F by an individual or family member. For serotype 14, a higher level of anticapsular IgG at the beginning of the study was associated with reduced odds of carriage (P = .006). There was a small (approximately 20%) but significant increase in titers of antibodies to PsaA and pneumolysin but no change in titers of antibody to PspA.


CONCLUSIONS
Adults respond to NP carriage by mounting anticapsular and weak antiprotein antibody responses, and naturally induced anticapsular IgG can prevent carriage.
Goldblatt
David
D
Immunobiology Unit, Institute of Child Health, University College London, UK. d.goldblatt@ich.ucl.ac.uk
Hussain
Mahein
M
Andrews
Nick
N
Ashton
Lindsey
L
Virta
Camilla
C
Melegaro
Alessia
A
Pebody
Richard
R
George
Robert
R
Soininen
Anu
A
Edmunds
John
J
Gay
Nigel
N
Kayhty
Helena
H
Miller
Elizabeth
E
D000328:Adult; D000917:Antibody Formation; D002353:Carrier State; D002675:Child, Preschool; D004739:England; D005191:Family Characteristics; D006801:Humans; D008137:Longitudinal Studies; D009305:Nasopharynx / Q000382:microbiology*; D011018:Pneumonia, Pneumococcal / Q000453:epidemiology / Q000635:transmission*; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000276:immunology* / Q000302:isolation & purification