Serum and salivary antibody responses to non-capsular Haemophilus influenzae antigens in children with meningitis and epiglottitis.

Serum IgG, IgA and IgM antibody and salivary IgA antibody concentrations to non-capsular Haemophilus influenzae antigens were measured in 13 children with H. influenzae type b meningitis and in 15 children with epiglottitis. Most had detectable serum IgG and IgM antibody at presentation but significantly fewer patients with meningitis had serum IgA antibody at presentation (P less than 0.05). Serum antibody concentrations had risen significantly by 3 weeks after presentation in patients with epiglottitis only. Convalescent serum IgG antibody concentrations against these antigens were higher in younger children with epiglottitis. Salivary IgA antibody to H. influenzae was detectable at presentation in all children with epiglottitis and in 12 of 13 with meningitis. Salivary antibody concentrations did not differ significantly between the two patient groups at presentation, although patients with meningitis had higher salivary IgA antibody concentrations than 10 children of similar age with bronchiolitis (P less than 0.02). There was no association between the presence of salivary antibody and low concentrations of convalescent serum antibody. The rise in convalescent serum antibody concentrations to non-capsular H. influenzae antigens only in children with epiglottitis is similar to findings for antibody to capsular polysaccharide. However, this rise was greater for IgG in younger patients, and the low titre of convalescent serum antibody in patients with meningitis was not associated with higher titres of IgA antibody in secretions as described by others for polysaccharide antibody. These findings suggest that the poor serum antibody response to these antigens in patients with meningitis is independent of age and is not due to mucosal induction of systemic tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)