DETECTION OF SERUM ANTIBODIES AGAINST CHLAMYDIA-PNEUMONIAE BY ELISA

Chlamydia pneumoniae causes pneumonia and other respiratory infections in children, adolescents and adults. We tried to evaluate the diagnos tic value of detection of serum antibodies by ELISA for C. pneumoniae infections in Japanese children. Serum IgG, IgA and IgM antibodies to C. pneumoniae were determined by the microimmunofluorescence (MIF) tes t. Serum IgG and IgA antibodies were also determined by ELISA test kit s. Results obtained by ELISA were compared with those obtained by MIF test. IgG antibody to C. pneumoniae was detected in 135 (39.5%) by ELI SA and in 125 (36.5%) by MIF out of 342 sera from Japanese infants and children without respiratory infections (aged from 2 months old to 15 years old). IgA antibody to C. pneumoniae was detected in 129 (37.7%) by ELISA and in 117 (34.2%) by MIF out of 342 sera tested. Of 342 spe cimens 113 were IgG-positive by ELISA and MIF (sensitivity: 90.4%, spe cificity: 89.9%, r = 0.853). Of 342 sera 28 had IgG antibody titers of 1:256 and none had titers 1:512 or higher by MIF. Of 28 infants and c hildren a total of nine were less than 4 years of age. On the other ha nd, of 342 specimens 99 were IgA-positive by ELISA and MIF (sensitivit y: 84.6%, specificity: 86.7%, r = 0.769). Of 342 sera 16 had IgA antib ody titers of 1:256 or higher by MIF. Of 16 infants and children, ten were less than 4 years of age. ELISA had excellent sensitivity and spe cificity relative to MIF test for detection of IgC and IgA antibodies to C. pneumoniae. It was suggested that C. pneumoniae infection in Jap anese infants and children under 4 years of age was not infrequent.