Interactions between extracellular Borrelia burgdorferi proteins and non-Borrelia-directed immunoglobulin M antibodies.
Previous work showed that outer surface protein A (OspA) and OspB of Borrelia burgdorferi may occur within an extracellular multiprotein complex, which was resolved by electrophoresis as an 83-kDa major extracellular protein band. To characterize the 83-kDa band, we sequenced the N terminus of the predominant peptide in the band and examined the interaction between the associated proteins. Peptide sequence and amino acid composition comparisons showed identity with the heavy chain of immunoglobulin M (IgM). Reduction sensitivity experiments and the recognition of the band by antibodies specific for rabbit mu chain indicated that the multiprotein complex contained pentameric IgM. Immunoelectron microscopy showed that anti-mu chain antibodies and monoclonal antibodies to OspA and OspB bound to extracellular amorphous material surrounding cells. Furthermore, the Osps coprecipitated with either nonspecific polyclonal rabbit IgM antibodies or with murine monoclonal anti-human serum albumin IgM antibodies, using insoluble anti-mu chain antibody conjugates. Although the apparent 83-kDa complex was stable under conditions of chelation and concentrated salts, it was disrupted by treatment with neuraminidase. These results indicate that extracellular B. burgdorferi proteins, including OspA and OspB, interact with IgM. The association is apparently not a classic antibody-antigen interaction but may result from other mechanisms.
Dorward
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DW
Laboratory of Vectors and Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, Hamilton, Montana 59840.
Huguenel
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ED
Davis
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Garon
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CF
D000595:Amino Acid Sequence; D000818:Animals; D000937:Antigen-Antibody Reactions; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D015748:Borrelia burgdorferi Group / Q000276:immunology*; D007075:Immunoglobulin M / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000494:pharmacology
D001425:Bacterial Outer Membrane Proteins; D007075:Immunoglobulin M; D009439:Neuraminidase