Mucosal immune responses to capsular pneumococcal polysaccharides in immunized preschool children and controls with similar nasal pneumococcal colonization rates.
BACKGROUND
Immunization with conjugate pneumococcal vaccines induces significant primary and memory IgG anti-polysaccharide (PS) responses in serum. It can also induce mucosal responses in infants especially after a polysaccharide booster. However, it is unclear whether it can prime for mucosal memory responses on nasal exposure to pneumococcus, which may be important in protection against pneumococcal invasion and/or carriage.


METHODS
IgA and IgG to serotypes 4, 6B, 9V, 14, 18C, 19F and 23F (conjugate vaccine serotypes), 1 and 3 (nonvaccine serotypes) capsular PS were measured by immunoassay in saliva from 2- to 5-year-old children previously given three doses of 7-valent pneumococcal conjugate vaccine in infancy, followed by 23-valent PS vaccine at 13 months and from unvaccinated controls of similar age and sex. Salivary antibody responses were analyzed in relation to carriage of pneumococci assessed by bacterial culture of nasopharyngeal swab samples collected in the summer and winter of the year 2000.


RESULTS
Rates of detectable IgG antibodies to all vaccine serotypes except 23F were higher in subjects than in controls. No such differences were observed for IgA antibodies except for serotype 6B. Nasal colonization rates were similar, and in both groups mucosal IgA responses were more common and larger than IgG responses.


CONCLUSIONS
The mucosal anti-capsular IgA responses observed could develop in response to colonization in preschool children, regardless of vaccination status, and contribute to the falling carriage rates observed with increasing age.
Zhang
Qibo
Q
Department of Clinical Sciences South Bristol, University of Bristol Faculty of Medicine, UBHT Education Centre, Upper Maudlin Street, Bristol BS2 8AE, UK.
Arnaoutakis
Konstantinos
K
Murdoch
Craig
C
Lakshman
Raman
R
Race
Gillian
G
Burkinshaw
Roger
R
Finn
Adam
A
D000914:Antibodies, Viral / Q000032:analysis / Q000276:immunology; D016022:Case-Control Studies; D002675:Child, Preschool; D015331:Cohort Studies; D015169:Colony Count, Microbial; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D007109:Immunity / Q000502:physiology*; D018928:Immunity, Mucosal; D007115:Immunization Schedule; D007070:Immunoglobulin A / Q000032:analysis / Q000276:immunology; D007074:Immunoglobulin G / Q000032:analysis; D007156:Immunologic Memory; D008297:Male; D009061:Mouth Mucosa / Q000276:immunology; D009297:Nasal Mucosa / Q000276:immunology; D011008:Pneumococcal Infections / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000008:administration & dosage*; D011336:Probability; D012016:Reference Values; D012680:Sensitivity and Specificity; D018074:Vaccines, Conjugate / Q000008:administration & dosage
C414006:23-valent pneumococcal capsular polysaccharide vaccine; D000914:Antibodies, Viral; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate