Protein D of Haemophilus influenzae is not a universal immunoglobulin D-binding protein.
Haemophilus influenzae type b and nontypeable H. influenzae have been reported to bind human immunoglobulin D (IgD). IgD myeloma sera from five patients were tested for the ability of IgD to bind to H. influenzae. Serotype b strains bound human IgD in four of the five sera tested. IgD in the fifth serum bound strongly to type b strain MinnA but poorly to other type b strains. Additionally, IgD binding was not observed when nontypeable strains were tested. The gene for protein D, the putative IgD-binding protein, was cloned from the IgD-binding H. influenzae type b strain MinnA and expressed in Escherichia coli. IgD binding to E. coli expressing protein D was not demonstrable. Recombinant protein D was purified, and antisera were generated in rabbits. Using these rabbit sera, we detected protein D in nontypeable as well as serotype b strains by Western blotting (immunoblotting). In contrast, IgD myeloma protein 4490, which was previously reported to bind to protein D by Ruan and coworkers (M. Ruan, M. Akkoyunlu, A. Grubb, and A. Forsgren, J. Immunol. 145:3379-3384), bound strongly to both type b and nontypeable H. influenzae as well as to E. coli expressing protein D. Thus, IgD binding is a general property of H. influenzae type b strains but not a general property of nontypeable strains, although both type b and nontypeable strains produce protein D. With the exception of IgD myeloma protein 4490 binding, we have no evidence for a role of protein D in IgD binding to H. influenzae.
Connaught Centre for Biotechnology Research, Toronto, Ontario, Canada.
K
K
Sasaki
R S
RS
Munson
D000818:Animals; D001426:Bacterial Proteins; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D005798:Genes, Bacterial; D006193:Haemophilus influenzae / Q000378:metabolism*; D006801:Humans; D007072:Immunoglobulin D / Q000378:metabolism*; D008074:Lipoproteins; D008222:Lymphokines / Q000378:metabolism*; D008969:Molecular Sequence Data; D009101:Multiple Myeloma / Q000097:blood; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D029584:Prostatic Secretory Proteins; D011817:Rabbits; D017422:Sequence Analysis, DNA
D001426:Bacterial Proteins; D002352:Carrier Proteins; D007072:Immunoglobulin D; D008074:Lipoproteins; D008222:Lymphokines; D011135:Polysaccharides, Bacterial; D029584:Prostatic Secretory Proteins; C043076:beta-microseminoprotein; C013059:immunoglobulin-binding factors; C067989:glpQ protein, Haemophilus influenzae