Immunological relation between serum antibodies against pneumolysin and against streptolysin O

The immunological relation between serum antibodies to pneumolysin and to streptolysin O was studied in patients with pneumococcal pneumonia (n = 40), patients with infections due to beta-haemolytic streptococci (n = 35), healthy human controls (n = 60) and in rabbits immunized with pneumolysin. There was no correlation between anti-pneumolysin and anti-streptolysin O titers (r = -0.279). The distribution of anti-pneumolysin titers in patients with high anti-streptolysin O titers did not differ from healthy controls. However, there was a tendency to increased or rising anti-streptolysin O titers in patients with pneumococcal infection. Antibodies obtained during pneumococcal infection might thus give false-positive reactions in the streptolysin O neutralization test. Serum antibodies to streptolysin O do not cross-react with pneumolysin in an ELISA. The pneumolysin ELISA for detection of pneumococcal disease will therefore not be disturbed by false-positive reactions due to antibodies directed against beta-haemolytic streptococci.