title: Serum opsonic activity after immunization of adults with Haemophilus influenzae type b-diphtheria toxoid conjugate vaccine.
abstract: We measured the uptake of radiolabeled Haemophilus influenzae type b by human polymorphonuclear leukocytes. Haemophilus influenzae type b strains were preopsonized in individual sera from six adults immunized with type b polysaccharide vaccine (PRP) or six adults immunized with PRP covalently coupled to diphtheria toxoid (PRP-D vaccine). Serum was heat inactivated before use, and exogenous human complement was added. Of the 12 subjects, 3 had high levels of opsonic activity (greater than 40% of immune control) in their preimmunization serum. This activity did not correlate with the concentrations of anti-PRP antibody and was unaffected by absorption of anti-PRP antibody. At 1 month after vaccination, the serum of PRP-D subjects had higher opsonic activity than that from subjects who received PRP (5% serum, mean PRP-D = 86%, mean PRP = 53%, P = 0.001). After 12 months, both groups had higher serum opsonic activity than before immunization (P less than 0.02), but there was no difference between the two groups (mean PRP-D = 48%, mean PRP = 51%). In postimmunization serum, opsonic activity induced by PRP-D or PRP vaccines correlated directly with anti-PRP antibody concentrations as measured by a radioantigen binding assay. We conclude that both vaccines induce opsonic activity, opsonic activity induced by immunization of adults correlates well with the concentration of anti-PRP antibody achieved, and in preimmune sera with low concentrations of anti-PRP antibody, factors other than anti-PRP antibody contribute to opsonic activity.
mesh_terms: D000328:Adult; D000907:Antibodies, Bacterial / Q000032:analysis; D001428:Bacterial Vaccines / Q000276:immunology*; D001770:Blood Bactericidal Activity; D004168:Diphtheria Toxoid / Q000276:immunology*; D006193:Haemophilus influenzae / Q000276:immunology*; D006801:Humans; D007114:Immunization; D009895:Opsonin Proteins / Q000032:analysis*; D010587:Phagocytosis; D011135:Polysaccharides, Bacterial / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines; D004168:Diphtheria Toxoid; D009895:Opsonin Proteins; D011135:Polysaccharides, Bacterial