Antibody responses to capsular polysaccharide, lipopolysaccharide, and outer membrane in adults infected with Haemophilus influenzae type b.

The antibody response to Haemophilus influenzae type b antigens as capsular polysaccharide, lipopolysaccharide, and outer membrane components was studied by enzyme-linked immunosorbent assay in 10 adults infected with this bacterium. Almost all patients had detectable amounts of immunoglobulins G and M antibodies specific to capsular polysaccharide, lipopolysaccharide, or outer membrane in their first serum sample. A significant antibody response in one or more antibody subclasses to capsular polysaccharide, lipopolysaccharide, and outer membrane was noted in 9 of 10, 7 of 10, and 7 of 10 patients, respectively. The occurrence of H. influenzae type b infections in adults cannot be completely explained either by the absence of antibodies against H. influenzae type b in their serum or by the failure to develop specific antibodies to the capsule or certain cell wall components even if these factors probably are important in some cases, e.g., in one patient who was splenectomized.