Characterization of the IgD binding site of encapsulated Haemophilus influenzae serotype b.
Encapsulated Haemophilus influenzae is a causative agent of invasive disease, such as meningitis and septicemia. Several interactions exist between H. influenzae and the human host. H. influenzae has been reported to bind IgD in a nonimmune manner, but the responsible protein has not yet been identified. To define the binding site on IgD for H. influenzae, full-length IgD and four chimeric IgDs with interspersed IgG sequences and Ag specificity for dansyl chloride were expressed in stably transfected Chinese hamster ovary cells. The binding of recombinant IgD to a panel of encapsulated H. influenzae serotype b (Hib) and nontypeable strains were investigated using a whole cell ELISA and flow cytometry. IgD binding was detected in 50% of the encapsulated Hib strains examined, whereas nontypeable H. influenzae did not interact with IgD. Finally, mapping experiments using the chimeric IgD/IgG indicated that IgD CH1 aa 198-224 were involved in the interaction between IgD and H. influenzae. Thus, by using recombinant IgD and chimeras with defined Ag specificity, we have confirmed that Hib specifically binds IgD, and that this binding involves the IgD CH1 region.
Samuelsson
Martin
M
Medical Microbiology, Department of Laboratory Medicine, Lund University, Malmö University Hospital, Malmö, Sweden.
Hallström
Teresia
T
Forsgren
Arne
A
Riesbeck
Kristian
K
D000595:Amino Acid Sequence; D000818:Animals; D016667:Bacterial Capsules / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D001666:Binding Sites, Antibody; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D000939:Epitopes / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D006193:Haemophilus influenzae / Q000276:immunology* / Q000378:metabolism*; D006801:Humans; D007127:Immunoglobulin Constant Regions / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007072:Immunoglobulin D / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007074:Immunoglobulin G / Q000235:genetics; D007143:Immunoglobulin Heavy Chains / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D050506:Mutant Chimeric Proteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding / Q000276:immunology
D000939:Epitopes; D007127:Immunoglobulin Constant Regions; D007072:Immunoglobulin D; D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains; D050506:Mutant Chimeric Proteins