Maternal antibodies and acquired serological response to Moraxella catarrhalis in children determined by an enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay (ELISA) for determination of serum immunoglobulin G (IgG) antibodies to Moraxella catarrhalis was developed, with an ultrasonic extract of M. catarrhalis immobilized on polystyrene microtiter plates serving as the antigen. The specificity was determined by adsorption tests. All of the 541 women tested showed a high level of maternal IgG antibodies to M. catarrhalis in umbilical cord blood specimens. One hundred eighty-nine children aged 0 to 15 years were examined. A low level of IgG antibodies to M. catarrhalis in serum was found in children aged up to 1 year; in older children, the levels increased with age. Levels in the same range as maternal IgG antibody levels were reached at the age of 10 years. The level of antibodies in children did not correlate with the state of colonization with M. catarrhalis or with the state of acute lower respiratory tract infection. Pairs of acute-phase and convalescent-phase serum samples did not discriminate between the children with M. catarrhalis in pure culture and those with mixed cultures of M. catarrhalis, Haemophilus influenzae, and Streptococcus pneumoniae. In adult women, high IgG antibody levels and low colonization rates with M. catarrhalis were found, whereas in small children, low IgG antibody levels and high colonization rates were found.