T. Nieminen et al., Pneumococcal conjugate vaccination in toddlers: mucosal antibody response measured as circulating antibody-secreting cells and as salivary antibodies, PEDIAT INF, 18(9), 1999, pp. 764-772
Background Our previous studies have shown an antibody-secreting cell (ASC)
response to pneumococcal vaccines in adults and suggested that a high IgA
ASC response is an indicator of a secretory IgA response in saliva. We beli
eve that the mucosal immune response is potentially an important characteri
stic of the pneumococcal vaccines and should thus be measured when the new
pneumococcal conjugate vaccines are evaluated.
Objectives. To study mucosal and serum antibody responses to pneumococcal c
onjugate vaccines in toddlers.
Methods. Each investigational vaccine, containing either 3 or 10 mu g of pn
eumococcal PS serotypes 6B, 14, 19F and 23F conjugated to either diphtheria
toroid (PncD) or tetanus protein (PncT), was administered to 10 children (
a total of 30 children). The ASC response was measured on Day 7 after immun
ization by enzyme-linked immunospot assay, and the salivary and serum antib
odies were measured before and 7 and 28 days after the immunization by enzy
me immunoassay.
Results. The vaccines studied induced ASC responses to the pneumococcal pol
ysaccharides (PS) in all children vaccinated. The ASC responses to the PS c
omponents of the vaccine (the geometric mean number of ASCs varying from 12
0 to 160 ASC/10(6) cells) were lower than those seen earlier in adults afte
r conjugate vaccine (240 to 2015 ASC/10(6) cells), but comparable with thos
e seen earlier in adults after pneumococcal PS vaccine (113 to 136 ASC/10(6
) cells). The ASC response was clearly dominated by IgA-secreting cells. Sa
livary IgA responses were detected in 35% of the children, but IgG was rare
ly detected in saliva. A positive correlation was demonstrated between the
number of IgA ASCs and salivary IgA concentration (r = 0.70, P = 0.01), sug
gesting that a high number of IgA ASCs after parenteral immunization is an
indicator of a secretory IgA response in saliva. On Day 28 after immunizati
on increased serum concentrations of IgG were detected in most vaccinees (7
5 to 95%, depending on the serotype).
Conclusions. Both mucosal and systemic antibody responses were induced by P
ncD and PncT vaccines in toddlers.